TrifrequencyReconfigurableLinearIrregularArraywithBeam ...downloads.hindawi.com/journals/ijap/2020/9074135.pdfVM “X “-’MM x y z (a) a d p b n3 n1 2 m1 m2 m3 fx O1 O2 x z y (b)

Research ArticleTrifrequency Reconfigurable Linear Irregular Array with BeamDeflection Capability in XKuKa-Bands

Ming Li 1 Haiping Wei2 Jiahao Zhao1 and Qingchang Tao 1

1State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentTsinghua University Beijing 100084 China2National Key Laboratory of Science and Technology on Aerospace Intelligent ControlBeijing Aerospace Automatic Control Institute Beijing 100854 China

Correspondence should be addressed to Qingchang Tao taoqingchangmailtsinghuaeducn

Received 2 April 2020 Revised 31 May 2020 Accepted 8 June 2020 Published 24 June 2020

Academic Editor Renato Cicchetti

Copyright copy 2020Ming Li et al(is is an open access article distributed under the Creative Commons Attribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

(is paper proposes a trifrequency reconfigurable antenna (FRA) which can work in the X-band Ku-band and Ka-band bycontrolling only two RFMEMS switches(e antenna element has a frequency ratio beyond 3 1 and provides a good candidate forthe frequency reconfigurable antenna array since the size of the antenna is reduced by loading multiple metal shorting holesbetween the antenna radiating surface and the ground plate and the overall size is only 014λX times 035λX (λX is the free-spacewavelength at 86GHz) Based on the proposed FRA element a 1times 16 linear irregular frequency reconfigurable antenna array(FRAA) with beam deflection ability is designed which effectively addresses the element spacing problem in the optimization ofthe array In addition the close-coupling in X-band and the grating lobe caused by the long distance of array element spacing inKa-band are comprehensively considered With uniform amplitude feeding network the sidelobe level is below minus15 dB underbeam deflection Moreover both FRA elements and FRAA prototypes have been fabricated and measured to verify their su-periority Good agreements are obtained between simulated and measured results which indicates that the antenna has potentialapplication in the future multifrequency wireless communication and intelligent radar anti-interference fields

1 Introduction

With the rapid development of wireless communicationand intelligent radar technology antennas have been desiredto be multifunctional intelligent miniaturized and low costHowever traditional single-function antenna is difficult tosatisfy these new requirements Increasing the number ofsingle-function antennas to implement multifunctional RF-integrated equipment can inevitably lead to many problemsthat is the increase in the area occupied by the antennamakes it difficult to achieve miniaturization and the stealthperformance of the aircraft Moreover the increase inequipment weight and cost becomes the main obstacle in thegreen application and development of the multifunctionalantenna In such case reconfigurable antenna bymechanically or electrically changing its architecture caneffectively change its performance characteristics (resonant

frequency radiation pattern polarization etc) [1] andtherefore provides a promising candidate to realize intelli-gent RF front end

Frequency reconfigurable antenna (FRA) has the ad-vantages of high spectrum utilization and strong anti-in-terference ability in the frequency domain (e resonantfrequency can be adjusted according to the working envi-ronment Previously FRA has received widespread attentionfrom the industrial sector and academia (e characteristicsof FRA have been verified and FRAs implemented in variousforms including dipole [2] slot [3 4] Vivaldi [5] patch[6 7] fractal [8] pixels [9ndash11] and reflection array [12] withtheir applications in radar [13] wireless communication[4 9] cognitive radio [2 5] aircraft conformal antenna [11]and satellite communication and navigation [7 12]

From the previous research mentioned previously weknow that the previously proposed FRA element mostly

HindawiInternational Journal of Antennas and PropagationVolume 2020 Article ID 9074135 11 pageshttpsdoiorg10115520209074135

focused on the low-frequency band and the frequency ratiowas generally less than 3 1 [2ndash11] However relatively fewreconfigurable antennas for Ku or higher frequency bandsand frequencies greater than 3 1 have been put forward [14]In response to the requirements of wireless communica-tions remote sensing and radar for frequency reconfig-urable antenna arrays a number of researches have also beencarried out [14ndash19] However the half-wavelength con-straint condition of the spacing between the traditionalphased array antenna elements poses great challenges to thelayout of the frequency reconstructed antenna arrayArraying in a low-frequency state makes the high-frequencyspacing too large but in a high-frequency state it can causecoupling in the low frequency [16 19] (erefore trifre-quency FRAA with beam deflection capability covering Ka-band and frequency ratio greater than 3 1 is urgentlydesired

In this paper a novel trifrequency XKuKa FRA elementis proposed and a 1times 16 linear irregular FRAA is designedbased on this element (e proposed design has the fol-lowing advantages (1) (e FRA unit uses two RF MEMSswitches to achieve frequency switching in X-band Ku-band and Ka-band and a frequency ratio of 357 1 isachieved (2) (e loading of multiple shorting metal holesbetween the radiation patch and the ground plate reducesthe overall size of the FRA to 014λX times 035λX (λX is the free-space wavelength at 86GHz) at the lowest frequency (usit provides a good candidate for the optimization of theelement spacing of the FRAA (3) Improved fruit-fly opti-mization algorithm (FOA) together with MATLAB-HFSScosimulation is used to optimize the element spacing of a1times 16 linear irregular FRAA with beam deflection ability inthe same direction in X-band Ku-band and Ka-band (etough spacing problem in the optimization of the traditionalFRAA is effectively addressed by the proposed method inthis paper and the sidelobe levels of different frequencyreconfigurability states are all lower than minus15 dB

(is paper is organized as follows In Section 2 thedesign of the FRA element is introduced and its frequencyreconfigurable performance is simulated and analysed InSection 3 the design and optimization of linear irregularfrequency reconfigurable arrays are discussed in detail andthe sidelobe levels of equally spaced antenna arrays arecompared and analysed (e production and testing of FRAand FRAA prototypes are introduced in Section 4 Finallyconclusion is drawn in Section 5

2 Design of FRA Element

21 Basic Structure Design It is well known that the oper-ating frequency of the antenna depends on the equivalentelectrical length of the radiator Generally speaking thelonger the equivalent electrical length the lower the oper-ating frequency Motivated by that an easy way to achievemultiband reconfigurable antenna can start from thesmallest size corresponding to the highest frequency that isby connecting additional patches with switches and byadjusting the overall size of the antenna by controlling theswitchesrsquo On and Off state According to this principle the

basic structure of the proposed FRA element is shown inFigure 1 (ree multiscale microstrip patches are printed onthe Rogers 4350B dielectric substrate whose dielectricconstant is 366 loss tangent is 0004 and thickness is0508mm It is fed by using a coaxial line When designingthe basic structure of the FRA element the two red rect-angles of 20mmtimes 11mm in Figure 1 indicate that RFswitches are replaced by copper plates to adjust the antennatopology(e connection or disconnection of the metal stripis equivalent to the OnOff function of the switch When S1is On and S2 is Off the FRA element can work in X-bandWhen S1 is Off and S2 is On the FRA element can work inKu-band Otherwise when both S1 and S2 switches are Offthe FRA element will work in Ka-band Figure 2 shows theoptimized process of the size of the three radiators

In addition the antenna is utilized to construct a lineararray working at the Ka-band (highest) which limits the sizeof the antenna element in the array dimension (e recentresearch shows that miniaturization of microstrip antennascan be achieved by shorting surfaces shorting strips orshorting probes [6 20] Inspired by that five metal shortingholes between the microstrip patch and the ground plate areemployed to reduce the overall antenna size in this paperand through the optimization of the diameter and spacing ofthe metal shorting holes a significant reduction in band-width is avoided the optimized results of which are shown inFigure 2(c)

Figure 3 shows the simulation results of reflection co-efficients at different frequency reconstruction states It canbe seen that FRA can work in X-band Ku-band and Ka-band Taking the reflection coefficient less than minus10 dB as thereference the impedance bandwidth and center frequencyare 106MHz (86GHz) 230MHz (171GHz) and 1900MHz(311GHz) respectively Moreover the reconstruction fre-quency ratio of the FRA reaches 361 1 and the size is50mmtimes 123mm which is only 0143λX times 0353λX at thelowest frequency (86GHz)

22 FRA Integrated RF MEMS Switch Design (e coplanarwaveguide capacitive MEMS switch proposed by the au-thorrsquos research group is used (e substrate material is high-resistance silicon (e insulating layer is formed by thermaloxidation of a silicon substrate whose main materialcomponent is silicon oxide A detailed description of theswitch can be found in [21]

(e structure of the FRA integrated RF MEMS switch isshown in Figure 4 Based on the antenna structure in theideal switching state a prepreg layer for lamination is addedunder the ground plate and a Rogers 4350B dielectricsubstrate with a thickness of 0508mm is introduced whichis used to route the coaxial feed port and the DC bias lines ofthe RF MEMS switches Gold wire with 20 um diameter isused to bond RF MEMS switches and microstrip patches

(e transition structure of the RF MEMS switch inte-grated into the microstrip antenna is shown in Figure 5 andthe transition structures of the switches S1 and S2 havedifferent sizes as shown in Table 1 (e CPW center signalline of the RF MEMS switch is connected to the microstrip

2 International Journal of Antennas and Propagation

Feeding point

S1S2

Metal shorting hole

x

y

z

(a)

a

d p

b

n3n1

n2m1

m2m3

fx L1

L2

x

yz

(b)

Figure 1 Geometry of the proposed FRA element (a) 3D view (b) Front view (unit (mm) a 170 b 340 m1 n1 23 m210n2 50 m3 n3 50 d 04 p 10 L1 11 and L2 20)

28 30 32 34

ndash35

ndash30

ndash25

ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)

m1 = 18 n1 = 23m1 = 23 n1 = 23m1 = 28 n1 = 23

m1 = 18 n1 = 25m1 = 23 n1 = 25m1 = 28 n1 = 25

(a)

|S11

| (dB

)

m2 = 08 n2 = 48m2 = 1 n2 = 48m2 = 08 n2 = 5

m2 = 1 n2 = 5m2 = 08 n2 = 52m2 = 1 n2 = 52

16 17 18 19ndash25

ndash20

ndash15

ndash10

ndash5

0

Frequency (GHz)

(b)

|S11

| (dB

)

908580ndash40

ndash30

ndash20

ndash10

0

Frequency (GHz)

p = 08 d = 04p = 08 d = 05p = 09 d = 04

p = 09 d = 05p = 10 d = 04p = 10 d = 05

(c)

Figure 2 Optimized results of the three radiators (a) Ka-band (b) Ku-band (c) X-band

International Journal of Antennas and Propagation 3

antenna radiation patch through a piece of trapezoidalgradient impedance transformation structure to achieveimpedance matching In addition a rectangular slot forswitch installation is designed with a gap of Fc 75 μm anarea of 135mmtimes 125mm (Wctimes Lc) and a depth of410 μm

ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34

S1 On S2 OffS1 Off S2 OnS1 Off S2 Off

Figure 3 Simulation results of reflection coefficients at different frequency reconstruction states

Upper substrate

Ground

PP floor

Lower substrate

Via pad RF MEMS switch

Ground padBond wire Switch driven pad

Coaxial feed pad

Switch bias line

x

y

z

Figure 4 Structure of the FRA integrated RF MEMS switches

Lc

Wc

W3

W1

W2

L1

L2

Fc

Figure 5 Transition structure of RF MEMS switch integrated inmicrostrip antenna

Table 1 Parameters of the transition structure of RFMEMS switchintegrated in microstrip antenna

Parameters S1 (mm) S2 (mm)L1 012 014L2 025 028W1 020 020W2 060 051W3 030 030


Simulation results of the reflection coefficient of FRAintegrated RF MEMS switches are shown in Figure 6 Underdifferent frequency reconstruction states the impedancebandwidth and center frequency of the FRA are 110MHz(87GHz) 226MHz (170 GHz) and 1902MHz (311GHz)respectively (e reflection coefficients of the antenna usingthe ideal switch and the antenna using the RF MEMS switchare evaluated and compared and the basically matchedfrequency reconstruction characteristics are obtained whichalso indicates that the effective integration of the switches isachieved through introducing the switch transitionstructure

3 Design of FRA Array

31 Spacing Optimization of FRA Element As shown inFigure 7 consider anN-element linear scan array distributedalong the x-axis [22] let d be the distance between the arrayelements and let θB be the scan angle then the total fieldstrength at the observation point P in the far field of the arraycan be expressed as

En fe(θ) 1113944N

n1ane

j(2πλ)(nminus 1)d sin θminus sin θB( ) (1)

where fe(θ) is the radiation pattern of a single antennaelement θ is the angle from boresight λ is the wavelengthand an represents the amplitude weighting coefficient of eacharray element

If the array is required not to generate grating lobes d

has to satisfy the following conditions

dltλ

1 +|sin θB| (2)

It can be known from (2) that if the frequency recon-figurable linear array is designed with the array elementspacing in the Ka-band the constraint conditions for theelement interval without the grating lobe are satisfied in bothX-band and Ku-band However for the X-band recon-struction state since the antenna array units are too densean increase in coupling effects and a decrease in radiationefficiency and gain can be resulted If the array spacingdesign is performed in the X-band the sidelobe level of theKa-band will inevitably be reduced and even grating lobescan appear (erefore the optimization of the array elementspacing becomes a key factor in the design of trifrequencyFRAA

Genetic algorithm and full wave analysis software HFSSwere jointly used to solve the optimization problem ofreconfigurable antenna [23] An improved fruit-fly opti-mization algorithm (FOA) is proposed to reduce the side-lobe level for antenna array synthesis in [24] In this paperthe distances between FRA elements are taken as the op-timization objectives and the improved fruit-fly optimiza-tion algorithm and MATLAB-HFSS joint simulation areused to optimize the line irregular FRAA (e spacingoptimization flowchart of the linear irregular FRAA ele-ments is shown in Figure 8

32 FRAA Design Based on the FRA element designed pre-viously and the array unit spacing optimization process shown inFigure 9 a 1times 16 linear irregular FRAA with beam deflectioncapability is designed(en the optimization objective is denotedas D [d1 d2 di d15] where di is the spacing betweenthe i-th and the (i+1)-th FRA element(e optimization intervalof the element spacing is 65mm to 20mm (e optimizationobjective function of this FRAA is defined as follows

minD

maxSLLXKuKa(D) minus SLLdgn11138681113868111386811138681113868

11138681113868111386811138681113868

st D d1 d2 di d151113858 1113859 di isin (65mm 20mm)

(3)

where maxSLLXKuKa(D) is the maximum sidelobe level ofthe array pattern at the three frequency bands and SLLdgn isthe optimization constraint for the sidelobe level which isminus15 dB in the optimization

In order to simplify the design optimization process ofthe 1times 16 linear irregular array copper microstrip lines areused instead of RF MEMS switches (e radiating surfacestructure is shown in Figure 9 (e 16 red rectangles and 16blue rectangles respectively represent a switch group K1and a switch group K2 composed of copper strips (eoptimized element spacing and the required phases areprovided in Figure 10 (e length of the effective radiationaperture of the FRAA is 1280mm

ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34


Figure 6 Simulation results of the reflection coefficient of FRAintegrated RF MEMS switches

X

Z

Y

1 2

P (far field)

n N ndash 1 N

θ

d

Figure 7 Schematic diagram of linear array antenna


When K1 is On and K2 is Off the FRAA works inX-band When K1 is Off and K2 is On the FRAA can workin Ku-band In addition when both K1 and K2 are Off theFRAA will work in Ka-band From the results of the re-flection coefficients of different frequency reconstructionstates in Figure 11 it can be seen that the impedancebandwidth and center frequency of the FRAA are 1100MHz(87GHz) 1950MHz (171GHz) and 1800MHz(300GHz) respectively Moreover the reconstruction fre-quency ratio of the FRA reaches 345 1 (e frequencyreconstruction capability of the antenna array and the fre-quency reconfigurable antenna unit is basically the same

Simulation results of the radiation pattern of the FRAAunder constant amplitude feeding conditions are shown in

Figure 12 Corresponding to the reconstruction states of Ka-band Ku-band and X-band the main polarization states areall vertical polarization and the cross-polarization levels areminus158 dB minus233 dB and minus175 dB respectively Besides thesidelobe levels are minus157 dB minus170 dB and minus162 dB re-spectively(e FRAA gains are 181 dB 170 dB and 125 dBIn addition the pattern beams deflection of the three states isthe same that is θxoz 20deg

For fair comparison a conventional uniform-pitchphased array is designed under the condition that the ef-fective radiation aperture of the antenna array is 128mmwith uniform amplitude excitation (e radiating surfacestructure of the uniform FRAA is shown in Figure 13 (estates of the switch groups corresponding to different

Randomly generating the first fruit fly population

Calculating smell concentration value

Calculating fitness function values

Find the optimal fitness value and determine the optimal result according to the simulated annealing mechanism

End condition Get array element spacing optimization results

YesNo

Cosimulation modeling

Full wave simulation in

HFSS Exporting simulation

results

MATLAB-HFSS cosimulation

Initializing parameters of the element spacing optimization and genetic

algorithm

Figure 8 Flowchart of spacing optimization of the linear irregular FRAA elements

No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x

Figure 9 (e schematic of the 1times 16 linear irregular FRAA


frequency reconstructions are the same as those of the ir-regular array shown in Figure 9 However all the spacingbetween the array elements is 82mm

Figure 14 shows the radiation pattern of the uniformarray Due to the effect of the array factor the beam de-flection is still θxoz 20deg Moreover since the array ap-erture and the number of array elements are not changedits antenna gains and 3 dB beam width are almost the sameas those of the irregular FRAA However it can also be seenthat the sidelobe levels are minus127 dB minus125 dB and minus123 dBin Ka-band Ku-band and X-band respectively (e in-crease in the sidelobe levels of the uniform array relative tothe irregular FRAA is more than 3 dB as shown in Fig-ure 15 It should be noted that when the uniform FRAAworks in the Ka-band state an obvious grating lobe appearsat minus53deg in the pattern which mainly because the arrayelement spacing exceeds the limit condition of (2) Whenthe array works in the Ka-band and the scanning angle is20deg the interval between the arrays should be controlledwithin 72mm to avoid the generation of grating lobesHowever under this constraint the array element spacingin the X-band operating state is less than 02λX which candefinitely result in the strong coupling effect between arrayelements

To show the superiority the irregular FRAA proposed inthis paper is compared with other counterparts as listed inTable 2 (e tunable FRA element has advantages in thefrequency reconstruction range and the number of switchesused In addition the irregular FRAA optimized by the jointintelligent algorithm and MATLAB-HFSS also achieves arelatively low sidelobe level with uniform amplitude feedingIt can also be seen that the proposed FRA element structurehas good potential in forming an array and the imple-mentation of the FRAA has the capability to solve theproblem of the constraint of the element spacing in thecurrent FRAA design

4 Fabrication and Measurement

Based on the design of the FRA element in Section 2 threeprototypes with ideal switch of the FRA element processedare shown in Figure 16 (e feed port is equipped with a292-KFD0705 RF connector that can support frequenciesup to 40 GHz covering the whole frequency reconfigurablerange To test the reflection coefficient of the antennaAgilent A5244A vector network analyser with a maximumadaptive frequency of 50 GHz is used (e reflectioncoefficient test results of the FRA unit are shown in Fig-ure 17 (e results of the prototype test and theoreticalsimulation are in good agreement (e center frequencyand impedance bandwidth of different frequency recon-struction states are almost unchanged compared with thesimulation results which proves that the FRA unit pro-posed in this paper has good frequency reconstructioncharacteristics

According to the FRAA design in Section 3 three typesof ideal switch FRAA prototypes are processed and auniform amplitude feeding network is added to eachprototype By simultaneously optimizing the feed line

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

25

30

Feed

pha

se (r

ad)

Element number

Ku-bandKa-band

4

6

8

10

12

14

X-bandElement spacing

Elem

ent s

paci

ng (m

m)

Figure 10 Optimization results of FRAA element spacing and portfeed phases

ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33


Figure 11 Simulation results of the reflection coefficient of FRAA

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Co-pol K1 On K2 OffCross-pol K1 On K2 OffCo-pol K1 Off K2 On

Cross-pol K1 Off K2 OnCo-pol K1 Off K2 OffCross-pol K1 Off K2 Off

ndash20 ndash10 0 10 20

Z

(dB)

X

Figure 12 Simulated radiation pattern of the linear irregularFRAA with the beam steering angles of θxoz 20deg


width of power divider and the length of the delay line theamplitude consistency of each output port is achievedMoreover the feed phase difference of the FRAA pro-totype for each frequency reconstruction state is deter-mined by Figure 10 (e structure of the FRAA prototypeis shown in Figure 18 and the processed FRAA prototypesare shown in Figure 19

(e radiation patterns of FRAA prototypes are tested in amicrowave shielded room as shown in Figure 20 Figure 21shows the simulated and measured results of the FRAAnormalized radiation pattern under uniform feeding con-ditions (e sidelobe level simulation results of FRAA op-erating in X-band Ku-band and Ka-band are minus151 dBminus149 dB and minus143 dB respectively (e results of the

No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x

Figure 13 (e schematic of the 1times 16 linear uniform FRAA

ndash80

ndash60

ndash40

ndash200

20

40

60

80

K1 On K2 OffK1 Off K2 OnK1 Off K2 Off


Z

(dB)

X

Figure 14 Simulated radiation pattern of the uniform FRAA with the beam steering angles of θxoz 20deg

Irregular FRAAndash18

ndash16

ndash14

ndash12

SLL

(dB)


Uniform FRAA

Figure 15 Comparison of sidelobe levels in irregular and uniform FRAA


sidelobe level measurements are minus136 dB minus131 dB andminus121 dB respectively Due to the testing environment errorthe sidelobe level is slightly increased which shows that thesidelobe level increases with the increase of the operatingfrequency On the whole the simulated and measured re-sults are in good agreement

Table 2 Comparison of the FRAA with other multibandswitchable-band antenna arrays

Item Our work Ref [14] Ref [16] Ref [19] Ref [18]Reconstruction band XKuKa XKuKa LS LC XKu (multiband)Frequency ratio 357 1 312 1 22 1 32 1 18 1Number of element switches 2 4 4 16 0Scanning range 20deg 0deg plusmn60deg plusmn60deg 50degIs the amplitude weighted No No No Not mentioned NoSidelobe level simulation result (dB) minus15720deg Not mentioned Around minus12515deg Around minus1200deg minus140 (synthetic)Element size (λL) 014times 035 014times 013 022times 022 018times 018 033times 033Element spacing (λLλH) Irregular 04127 0505 036lt05 033058

Ka state X state Feed portKu state

Figure 16 (e fabricated FRA prototypes

ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

X-band simuX-band measKu-band simu

Ku-band measKa-band simuKa-band meas

Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34

Figure 17 Measured reflection coefficients of FRA prototypeworking at different states

Upper substrateGround

PP floor

Lower substrate

Uniform amplitude feeding network

x y

z

Figure 18 Structure of the FRAA prototype with uniform am-plitude feeding network

Radiation surface of FRAA in Ka-band

Radiation surface of FRAA in Ku-band

Radiation surface of FRAA in X-band

(a)

Feeding network of FRAA in Ka-band

Feeding network of FRAA in Ku-band

Feeding network of FRAA in X-band

(b)

Figure 19 (e fabricated 1times 16 linear irregular FRAA prototype(a) Radiation surface (b) Feeding network surface

Figure 20 (e measured scene


5 Conclusion

In this paper a frequency reconfigurable antenna elementintegrating two RF MEMS switches has been proposed (eFRA element has the reconstruction capability in X-band Ku-band and Ka-band and the frequency reconstruction ratioreaches 357 1 Besides the miniaturization design of the el-ement has been achieved through five metal shorting holesbetween the radiating surface and the ground plate reaching014λXtimes 035λX providing a good structural basis for thefrequency reconfigurable antenna array By employing intel-ligent algorithm and MATLAB-HFSS joint optimization a1times 16 linear irregular FRAA based on the FRA element hasbeen proposed which realizes that beam deflection in the samedirection corresponds to different frequency reconstructionstate In addition compared with the traditional uniformlyspaced FRAA the sidelobe level of the irregular antenna linearray is improved by not less than 3dB and the grating lobe inthe Ka band is effectively avoided Finally both FRA elementand FRAA prototypes have been fabricated and tested to verifytheir superiority (e measurement results show that theproposed trifrequency reconfigurable linear irregular FRAA

has broad application prospects in the future multifrequencywireless communication and intelligent radar anti-interferencefields

Data Availability

(e data used to support the findings of this study are in-cluded within the article

Conflicts of Interest

(e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

(is work was supported by the National Natural ScienceFoundation of China under Grant 61774096

References

[1] IEEE ldquoIEEE standard definitions of terms for antennasrdquo IEEEStd vol 145-2013 2013

ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band

ndash30 ndash20 ndash10 0

Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)

Figure 21 (e normalized radiation pattern measured and simulated results of FRAA prototypes in different frequency reconstructionstates (a) X-band (b) Ku-band (c) Ka-band


[2] L Ge and K-M Luk ldquoA band-reconfigurable antenna basedon directed dipolerdquo IEEE Transactions on Antennas andPropagation vol 62 no 1 pp 64ndash71 2014

[3] C R White and G M Rebeiz ldquoA shallow varactor-tunedcavity-backed slot antenna with a 191 tuning rangerdquo IEEETransactions on Antennas and Propagation vol 58 no 3pp 633ndash639 2010

[4] C-Y Chiu J Li S Song and R D Murch ldquoFrequency-reconfigurable pixel slot antennardquo IEEE Transactions onAntennas and Propagation vol 60 no 10 pp 4921ndash49242012

[5] M R Hamid P Gardner P S Hall and F GhanemldquoSwitched-band vivaldi antennardquo IEEE Transactions on An-tennas and Propagation vol 59 no 5 pp 1472ndash1480 2011

[6] A Boukarkar X Q Lin Y Jiang and X F Yang ldquoA compactfrequency-reconfigurable 36-states patch antenna for wirelessapplicationsrdquo IEEE Antennas and Wireless Propagation Let-ters vol 17 no 7 pp 1349ndash1353 2018

[7] C Sun H Zheng L Zhang and Y Liu ldquoA compact frequencyreconfigurable patch antenna for Beidou (COMPASS) navi-gation systemrdquo IEEE Antennas Wireless Propagation Lettersvol 13 pp 967ndash970 2014

[8] Y K Choukiker and S K Behera ldquoWideband frequencyreconfigurable Koch snowflake fractal antennardquo IET Micro-waves Antennas amp Propagation vol 11 no 2 pp 203ndash2082017

[9] A Grau M-J Lee J Romeu H Jafarkhani L Jofre andF De Flaviis ldquoA multifunctional mems-reconfigurable pixelantenna for narrowband mimo communicationsrdquo in Pro-ceedings of the 2007 IEEE Antennas and Propagation SocietyInternational Symposium Honolulu HI USA June 2007

[10] D Rodrigo Y Damgaci N Biyikli B A Cetiner J Romeuand L Jofre ldquoMEMS-reconfigurable antenna based on amulti-size pixelled geometryrdquo in Proceedings of the FourthEuropean Conference on Antennas and Propagation (EuCAP)IEEE Barcelona Spain pp 1ndash4 April 2010

[11] M D Wright W Baron J Miller J Tuss D Zeppettella andM Ali ldquoMEMS reconfigurable broadband patch antenna forconformal applicationsrdquo IEEE Transactions on Antennas andPropagation vol 66 no 6 pp 2770ndash2778 2018

[12] H Yang F Yang X Cao et al ldquoA 1600-element dual-fre-quency electronically reconfigurable reflectarray at XKu-bandrdquo IEEE Trans Antennas Propagvol 65 no 6pp 3024ndash3032 2017

[13] R L Jordan B L Huneycutt and M Werner ldquo(e SIR-CX-SAR synthetic aperture radar systemrdquo IEEE Transactions onGeoscience and Remote Sensing vol 33 no 4 pp 829ndash8391995

[14] L Li Z Wu K Li et al ldquoFrequency-reconfigurable Quasi-Sierpinski antenna integrating with dual-band high-imped-ance surfacerdquo IEEE Transactions on Antennas and Propaga-tion vol 62 no 9 pp 4459ndash4467 2014

[15] J A Byford K Y Park P Chahal and E J RothwellldquoFrequency reconfigurable patch antenna arrayrdquo ElectronicsLetters vol 51 no 21 pp 1628ndash1630 2015

[16] N Haider A G Yarovoy and A G Roederer ldquo$LS$ -bandfrequency reconfigurable multiscale phased array antennawith wide angle scanningrdquo IEEE Transactions on Antennasand Propagation vol 65 no 9 pp 4519ndash4528 2017

[17] Q Li T Li Z Li and J Fang ldquoUnidirectional frequencyreconfigurable bow-tie antenna array with AMC reflectorrdquo inProceedings of the 11th European Conference on Antennas andPropagation (EUCAP) pp 2221ndash2223 Paris France March2017

[18] S E Valavan D Tran A G Yarovoy and A G RoedererldquoDual-band wide-angle scaning planar phased array in XKu-bandsrdquo IEEE Transactions on Antennas and Propagationvol 62 no 5 pp 2514ndash2521 2014

[19] M Shirazi J Huang T Li and X Gong ldquoA switchable-frequency slot-ring antenna element for designing a recon-figurable arrayrdquo IEEE Antennas and Wireless PropagationLetters vol 17 no 2 pp 229ndash233 2018

[20] K-L Wong Compact and Broadband Microstrip AntennaJohn Wiley amp Sons New York NY USA 2002

[21] M Li J Zhao Z You andG Zhao ldquoDesign and fabrication ofa low insertion loss capacitive RF MEMS switch with novelmicro-structures for actuationrdquo Solid-State Electronicsvol 127 pp 32ndash37 2017

[22] D Parker and D C Zimmermann ldquoPhased arraysmdashpart 1theory and architecturesrdquo IEEE Transactions on Microwavegteory and Techniques vol 50 no 3 pp 678ndash687 2002

[23] X Yuan Z Li D Rodrigo et al ldquoA parasitic layer-basedreconfigurable antenna design by multi-objective optimiza-tionrdquo IEEE Transactions on Antennas and Propagationvol 60 no 6 pp 2690ndash2701 2012

[24] A Darvish and A Ebrahimzadeh ldquoImproved fruit-fly opti-mization algorithm and its applications in antenna arrayssynthesisrdquo IEEE Transactions on Antennas and Propagationvol 66 no 4 pp 1756ndash1766 2018


focused on the low-frequency band and the frequency ratiowas generally less than 3 1 [2ndash11] However relatively fewreconfigurable antennas for Ku or higher frequency bandsand frequencies greater than 3 1 have been put forward [14]In response to the requirements of wireless communica-tions remote sensing and radar for frequency reconfig-urable antenna arrays a number of researches have also beencarried out [14ndash19] However the half-wavelength con-straint condition of the spacing between the traditionalphased array antenna elements poses great challenges to thelayout of the frequency reconstructed antenna arrayArraying in a low-frequency state makes the high-frequencyspacing too large but in a high-frequency state it can causecoupling in the low frequency [16 19] (erefore trifre-quency FRAA with beam deflection capability covering Ka-band and frequency ratio greater than 3 1 is urgentlydesired

In this paper a novel trifrequency XKuKa FRA elementis proposed and a 1times 16 linear irregular FRAA is designedbased on this element (e proposed design has the fol-lowing advantages (1) (e FRA unit uses two RF MEMSswitches to achieve frequency switching in X-band Ku-band and Ka-band and a frequency ratio of 357 1 isachieved (2) (e loading of multiple shorting metal holesbetween the radiation patch and the ground plate reducesthe overall size of the FRA to 014λX times 035λX (λX is the free-space wavelength at 86GHz) at the lowest frequency (usit provides a good candidate for the optimization of theelement spacing of the FRAA (3) Improved fruit-fly opti-mization algorithm (FOA) together with MATLAB-HFSScosimulation is used to optimize the element spacing of a1times 16 linear irregular FRAA with beam deflection ability inthe same direction in X-band Ku-band and Ka-band (etough spacing problem in the optimization of the traditionalFRAA is effectively addressed by the proposed method inthis paper and the sidelobe levels of different frequencyreconfigurability states are all lower than minus15 dB

(is paper is organized as follows In Section 2 thedesign of the FRA element is introduced and its frequencyreconfigurable performance is simulated and analysed InSection 3 the design and optimization of linear irregularfrequency reconfigurable arrays are discussed in detail andthe sidelobe levels of equally spaced antenna arrays arecompared and analysed (e production and testing of FRAand FRAA prototypes are introduced in Section 4 Finallyconclusion is drawn in Section 5

2 Design of FRA Element

21 Basic Structure Design It is well known that the oper-ating frequency of the antenna depends on the equivalentelectrical length of the radiator Generally speaking thelonger the equivalent electrical length the lower the oper-ating frequency Motivated by that an easy way to achievemultiband reconfigurable antenna can start from thesmallest size corresponding to the highest frequency that isby connecting additional patches with switches and byadjusting the overall size of the antenna by controlling theswitchesrsquo On and Off state According to this principle the

basic structure of the proposed FRA element is shown inFigure 1 (ree multiscale microstrip patches are printed onthe Rogers 4350B dielectric substrate whose dielectricconstant is 366 loss tangent is 0004 and thickness is0508mm It is fed by using a coaxial line When designingthe basic structure of the FRA element the two red rect-angles of 20mmtimes 11mm in Figure 1 indicate that RFswitches are replaced by copper plates to adjust the antennatopology(e connection or disconnection of the metal stripis equivalent to the OnOff function of the switch When S1is On and S2 is Off the FRA element can work in X-bandWhen S1 is Off and S2 is On the FRA element can work inKu-band Otherwise when both S1 and S2 switches are Offthe FRA element will work in Ka-band Figure 2 shows theoptimized process of the size of the three radiators

In addition the antenna is utilized to construct a lineararray working at the Ka-band (highest) which limits the sizeof the antenna element in the array dimension (e recentresearch shows that miniaturization of microstrip antennascan be achieved by shorting surfaces shorting strips orshorting probes [6 20] Inspired by that five metal shortingholes between the microstrip patch and the ground plate areemployed to reduce the overall antenna size in this paperand through the optimization of the diameter and spacing ofthe metal shorting holes a significant reduction in band-width is avoided the optimized results of which are shown inFigure 2(c)

Figure 3 shows the simulation results of reflection co-efficients at different frequency reconstruction states It canbe seen that FRA can work in X-band Ku-band and Ka-band Taking the reflection coefficient less than minus10 dB as thereference the impedance bandwidth and center frequencyare 106MHz (86GHz) 230MHz (171GHz) and 1900MHz(311GHz) respectively Moreover the reconstruction fre-quency ratio of the FRA reaches 361 1 and the size is50mmtimes 123mm which is only 0143λX times 0353λX at thelowest frequency (86GHz)

22 FRA Integrated RF MEMS Switch Design (e coplanarwaveguide capacitive MEMS switch proposed by the au-thorrsquos research group is used (e substrate material is high-resistance silicon (e insulating layer is formed by thermaloxidation of a silicon substrate whose main materialcomponent is silicon oxide A detailed description of theswitch can be found in [21]

(e structure of the FRA integrated RF MEMS switch isshown in Figure 4 Based on the antenna structure in theideal switching state a prepreg layer for lamination is addedunder the ground plate and a Rogers 4350B dielectricsubstrate with a thickness of 0508mm is introduced whichis used to route the coaxial feed port and the DC bias lines ofthe RF MEMS switches Gold wire with 20 um diameter isused to bond RF MEMS switches and microstrip patches

(e transition structure of the RF MEMS switch inte-grated into the microstrip antenna is shown in Figure 5 andthe transition structures of the switches S1 and S2 havedifferent sizes as shown in Table 1 (e CPW center signalline of the RF MEMS switch is connected to the microstrip


Feeding point

S1S2

Metal shorting hole

x

y

z

(a)

a

d p

b

n3n1

n2m1

m2m3

fx L1

L2

x

yz

(b)


28 30 32 34

ndash35

ndash30

ndash25

ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)

m1 = 18 n1 = 23m1 = 23 n1 = 23m1 = 28 n1 = 23

m1 = 18 n1 = 25m1 = 23 n1 = 25m1 = 28 n1 = 25

(a)

|S11

| (dB

)

m2 = 08 n2 = 48m2 = 1 n2 = 48m2 = 08 n2 = 5

m2 = 1 n2 = 5m2 = 08 n2 = 52m2 = 1 n2 = 52

16 17 18 19ndash25

ndash20

ndash15

ndash10

ndash5

0

Frequency (GHz)

(b)

|S11

| (dB

)

908580ndash40

ndash30

ndash20

ndash10

0

Frequency (GHz)

p = 08 d = 04p = 08 d = 05p = 09 d = 04

p = 09 d = 05p = 10 d = 04p = 10 d = 05

(c)




ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34



Upper substrate

Ground

PP floor

Lower substrate



Coaxial feed pad

Switch bias line

x

y

z


Lc

Wc

W3

W1

W2

L1

L2

Fc








En fe(θ) 1113944N

n1ane





dltλ

1 +|sin θB| (2)




minD


11138681113868111386811138681113868


(3)



ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34



X

Z

Y

1 2

P (far field)

n N ndash 1 N

θ

d












YesNo




results



algorithm


No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x









1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

25

30

Feed

pha

se (r

ad)

Element number

Ku-bandKa-band

4

6

8

10

12

14


Elem

ent s

paci

ng (m

m)


ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33



ndash80

ndash60

ndash40

ndash200

20

40

60

80




Z

(dB)

X





No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x


ndash80

ndash60

ndash40

ndash200

20

40

60

80



Z

(dB)

X



ndash16

ndash14

ndash12

SLL

(dB)


Uniform FRAA








ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)



Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34



PP floor

Lower substrate


x y

z





(a)




(b)




5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)



























Feeding point

S1S2

Metal shorting hole

x

y

z

(a)

a

d p

b

n3n1

n2m1

m2m3

fx L1

L2

x

yz

(b)


28 30 32 34

ndash35

ndash30

ndash25

ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)

m1 = 18 n1 = 23m1 = 23 n1 = 23m1 = 28 n1 = 23

m1 = 18 n1 = 25m1 = 23 n1 = 25m1 = 28 n1 = 25

(a)

|S11

| (dB

)

m2 = 08 n2 = 48m2 = 1 n2 = 48m2 = 08 n2 = 5

m2 = 1 n2 = 5m2 = 08 n2 = 52m2 = 1 n2 = 52

16 17 18 19ndash25

ndash20

ndash15

ndash10

ndash5

0

Frequency (GHz)

(b)

|S11

| (dB

)

908580ndash40

ndash30

ndash20

ndash10

0

Frequency (GHz)

p = 08 d = 04p = 08 d = 05p = 09 d = 04

p = 09 d = 05p = 10 d = 04p = 10 d = 05

(c)




ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34



Upper substrate

Ground

PP floor

Lower substrate



Coaxial feed pad

Switch bias line

x

y

z


Lc

Wc

W3

W1

W2

L1

L2

Fc








En fe(θ) 1113944N

n1ane





dltλ

1 +|sin θB| (2)




minD


11138681113868111386811138681113868


(3)



ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34



X

Z

Y

1 2

P (far field)

n N ndash 1 N

θ

d












YesNo




results



algorithm


No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x









1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

25

30

Feed

pha

se (r

ad)

Element number

Ku-bandKa-band

4

6

8

10

12

14


Elem

ent s

paci

ng (m

m)


ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33



ndash80

ndash60

ndash40

ndash200

20

40

60

80




Z

(dB)

X





No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x


ndash80

ndash60

ndash40

ndash200

20

40

60

80



Z

(dB)

X



ndash16

ndash14

ndash12

SLL

(dB)


Uniform FRAA








ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)



Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34



PP floor

Lower substrate


x y

z





(a)




(b)




5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)




























ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34



Upper substrate

Ground

PP floor

Lower substrate



Coaxial feed pad

Switch bias line

x

y

z


Lc

Wc

W3

W1

W2

L1

L2

Fc








En fe(θ) 1113944N

n1ane





dltλ

1 +|sin θB| (2)




minD


11138681113868111386811138681113868


(3)



ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34



X

Z

Y

1 2

P (far field)

n N ndash 1 N

θ

d












YesNo




results



algorithm


No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x









1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

25

30

Feed

pha

se (r

ad)

Element number

Ku-bandKa-band

4

6

8

10

12

14


Elem

ent s

paci

ng (m

m)


ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33



ndash80

ndash60

ndash40

ndash200

20

40

60

80




Z

(dB)

X





No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x


ndash80

ndash60

ndash40

ndash200

20

40

60

80



Z

(dB)

X



ndash16

ndash14

ndash12

SLL

(dB)


Uniform FRAA








ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)



Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34



PP floor

Lower substrate


x y

z





(a)




(b)




5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)






























En fe(θ) 1113944N

n1ane





dltλ

1 +|sin θB| (2)




minD


11138681113868111386811138681113868


(3)



ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90160 165 170 175 180 28 29 30 31 32 33 34



X

Z

Y

1 2

P (far field)

n N ndash 1 N

θ

d












YesNo




results



algorithm


No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x









1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

25

30

Feed

pha

se (r

ad)

Element number

Ku-bandKa-band

4

6

8

10

12

14


Elem

ent s

paci

ng (m

m)


ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33



ndash80

ndash60

ndash40

ndash200

20

40

60

80




Z

(dB)

X





No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x


ndash80

ndash60

ndash40

ndash200

20

40

60

80



Z

(dB)

X



ndash16

ndash14

ndash12

SLL

(dB)


Uniform FRAA








ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)



Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34



PP floor

Lower substrate


x y

z





(a)




(b)




5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)




































YesNo




results



algorithm


No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x









1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

25

30

Feed

pha

se (r

ad)

Element number

Ku-bandKa-band

4

6

8

10

12

14


Elem

ent s

paci

ng (m

m)


ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33



ndash80

ndash60

ndash40

ndash200

20

40

60

80




Z

(dB)

X





No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x


ndash80

ndash60

ndash40

ndash200

20

40

60

80



Z

(dB)

X



ndash16

ndash14

ndash12

SLL

(dB)


Uniform FRAA








ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)



Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34



PP floor

Lower substrate


x y

z





(a)




(b)




5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)

































1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160

5

10

15

20

25

30

Feed

pha

se (r

ad)

Element number

Ku-bandKa-band

4

6

8

10

12

14


Elem

ent s

paci

ng (m

m)


ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)

Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33



ndash80

ndash60

ndash40

ndash200

20

40

60

80




Z

(dB)

X





No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x


ndash80

ndash60

ndash40

ndash200

20

40

60

80



Z

(dB)

X



ndash16

ndash14

ndash12

SLL

(dB)


Uniform FRAA








ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)



Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34



PP floor

Lower substrate


x y

z





(a)




(b)




5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)





























No 1 No 2 No 15 No 16

d1 d15d2

No 3

y

x


ndash80

ndash60

ndash40

ndash200

20

40

60

80



Z

(dB)

X



ndash16

ndash14

ndash12

SLL

(dB)


Uniform FRAA








ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)



Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34



PP floor

Lower substrate


x y

z





(a)




(b)




5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)
































ndash20

ndash15

ndash10

ndash5

0

|S11

| (dB

)



Frequency (GHz)80 85 90 160 165 170 175 180 28 29 30 31 32 33 34



PP floor

Lower substrate


x y

z





(a)




(b)




5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)



























5 Conclusion



Data Availability




Acknowledgments


References


ndash80

ndash60

ndash40

ndash200

20

40

60

80

X-band


Z

(dB)

X

SimuMeas

(a)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ku-band


Z

(dB)

X

SimuMeas

(b)

ndash80

ndash60

ndash40

ndash200

20

40

60

80

Ka-band

SimuMeas


Z

(dB)

X

(c)



















































Documents

TrifrequencyReconfigurableLinearIrregularArraywithBeam ...downloads.hindawi.com/journals/ijap/2020/9074135.pdfVM “X “-’MM x y z (a) a d p b n3 n1 2 m1 m2 m3 fx O1 O2 x z y (b)