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5.75 6.00 6.25 6.50 6.75 7 W 1.25frequency,GH r
Fig. 7 Experimental and theoretical S, i - porantr ler .~ J f
i~ui -pat chniennu~ mcaiured ........... elechical model - - . - -
- M O M
T he values of the S12 an d Sl, arameters are in good agreement
withmeasurement in the neighbourhood of the resonance. The maxima
ofSlz nd S , ; parameters obtained with the model are at the same
valuesas the experimenral ones. The shape of the curves represented
areacceptable too.
Conclusion: A simple modcl, extracted from a 3D
electromagneticmethod, is proposed to describe the electrical
behaviour of coupledpatches. This model takes into account the
coupling between de me ntsand is generalised in th c case of a
patch array antenna . I t can be usedin an electrical simulator to
calculate the S-parameters with moreaccuracy. As this method is
economical in tcrms of computer time,one can consider that its us c
will improve the design of an anay wi thnumerous patches.0 EE
2003Electronics Lellers Online No: 20030627Dol : IO.
049/e1:20030627A. H afianc, H. Aissa t and 0. Picon (ESYCOM,
(iniver.vi& de M a r n e -la- YalUe, 5 Bd Dercarres, 77454
Marne-lo-Yall& Cedex2, F r a n c e )References
I April 2003
I SHEEN.% ALLS. , ABOUZAHKA.M., andK0NC.J.: 'Application o f t h
c three-dimensional finite-difference time domain method to the
analysis ofplanar microstep circuits', IEEE MTT-S Inl. Micmw! Symp.
Dig., 1990,38, (7). pp. 218-252WHEELER, H.A.: 'Transmission-line
propcliies of a swip on dielectricplane', IEEE MTT-S Inf Microw
Sy". Dig., 1977H A P I A N , A., CIRIO, L., and PICON. 0.:
'Elcct"cal mode l and mutualcoupling betwen microstrip antennas
expressed through FDTDmethod'. Proc. 30th European Microwa\,e
Conf., Pans, France. October2000
23
Wideband dielectric resonator antennaexcited by cavity-backed
circular aperturewi th microstrip tuning forkK.W. Leung and C.K.
Leung
A wideband dielechic resonator antenna excited by a circular
apenurcis investigated enpenmentally. The aperture is coupled by a
microshipfeedline wi fi a microsttip fork-like tuning stub. A
backing cavity i splaccd beneath the stub 10 block undesirable
backside radiation. Therehlm loss, field panem, an d antcnnagain of
the proposed configura-tion were measured and th e results are
compared with those withoutth e backing cavily
lnrroducrion: In the last WO decades, the dielectric resonator
antenna(DR A) has received extensivc attention [ I - IO ] because
of its inherentadvantages, including its small size, l ight weight,
low loss, low cost,and ease of excitation, Although the bandwidth
of a D R A is wideenough for many applications (- 10% for
dielectric cons tant E, - O),investigation of bandwidth enhancement
techniques has been a
popular topic for the DRA. Stacking and parastic-element
methods[I-31 were use d but they require more than on e DRA . Som e
attentionhas been paid to single-DRA configurations to reduce size
an d cost,such as the airgap method (41, conductor-loading method
[SI,dielec-tric-coating method 161, str ip-loading method 17, 81,
and special-DRAmethod 191.Recently, it has been found tha t awidcb
and DR A can alsobe obtained by using an annularexcitation slot [
IO] . In this Lctter, weextend the annular slot to become a
circular aperture, which iscoupled by a microstrip li nt with a
fork-like tuning stub [ I l l . Todemonstrate the method a
cylindrical DRA, excited in its fundamen-ta l TM,,,, mode [ IO] ,
is used in our configuration. A hemisphericalbacking cavity, which
is concentric with the aperture, is placcdbeneath the tuning fork
to block the backside radiation through thecircular aperture. T he
proposed configuration can remarkably offer abandwid th as wide as
38%. The re tum loss, radiation pattern, andantenna gain of the
configuration were measured. The results arecompared with those
without the backing cavity. I t is found that thcbandwidth can
further be increased to 40 % if the backing cavity isremoved, at
the cost of reducing the antenna gain.
Anlennn confgrrrafion: The perspective view of the antenna
con-figuration is shown in Fig. lo, where the cylindrical DR A of
radius 0 ,height h, and dielectric co nstant E, is concentrically
fed by a circularaperture of radius F. The circular aperture was
etched on the groundplane o f a 5 0 0 icrostrip feedlinc with a
fork-like tuning stub. Bclawthe tuning fork is a backing cavity of
radius b, which is placedconcentrically with the aperture. Fig. I h
shows the geometry of th etuning fork. As studied in [ I l l , a
distance I , between the two arms ofthe fork is required to give B
uniform f ield distr ibution in the aperture,whereas 1, is used to
f ine-tune the input reactance. In addition, B smal lstraight
microstrip section of ength l 2 is needed to have a wideimpedance
bandwidth. All of them and the microstrip feedline havewidth W,
whereas the substrate has dielectric constant t:?,% an dthickness d
. Two antennas were measured, namely antenna I an dantenna 2. The
backing cavity is used for antenna 1. Antenna 2 is th esame as an
tenna 1, except that the backing cavity is removed.
c?>"O"c4DW- 3 r kdFig. 1 Antenna configurofionr? Perspective
view b Geometry of tuning fork
" I I
I5 6 7 Bfrequency, GH I
Fig. 2 Measured relitin I m s e s of antennas I and 2ELECTRONlCS
LETTERS 10th J u l y 2003 Vol. 39 N o . 14 1033
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2 LEUNC, K.W., ef al.: 'Bandwidth enhancemcnt of dielectric
resonatorantenna by loading a low-profile dielecttic disk of vety
highpermittivity', Elecnn. Lerr., 1997. 33, pp. 725-1263 FAX:. 2..
er al.: 'Parasitic coplanar three-element dielectnc
resonatorantenna rubarmy', Electron. L e x , 1996, 32, pp. 789-7904
WONG, K.-L., CHEN, N.E., and CHBR, H.-T.: 'Analysis of a
hemisphencaldielecttic resonator antcnna with an airgap'. IEEE
Microw Cuid. Wave
Lett., 1993,3, pp. 355-3575 LEUNG, K.W.: 'Complex resonance and
radiation of hemisphencaldielectric resonator antenna with a
concentric conductor'. IEEE Trans.MicmK! Theory Eech.,2001, 49, pp.
524-531CHEN. N.C.. era/.: Analysis ofa broadband slot-coupled
dielectric-coatedhemispherical diclecttic resonator antenna',
Micmb; Opf. Techno/.Leii.,1995,8, pp. 13-16NC. 1l.K , and LEUNG,
K.W: 'Conformal-sulp-excited dielectric resonatorantenna with a
parasitic strip'. IEEE Antennas and Propagation SocietyInt. Symp.
Dig.. Salt Lzke City, Utah, USA, 2000, Vol. 4. pp. 2080-2083LONG.
R.T.. r d:Use of parasitic strip to produce circular
polarisationand increased bandwidth fo r cylindtical dielectric
resonator antenna',Electron. LetI.. 2001, 37 , pp. 40MOR9 K I S H K
, A.A . , y.13. Y., an d GLISSON, A . W : 'Conical dielectnc
resonatorantennas for wideband applications', IEEE Tmns. Antennas
Pmpag.,2002, 50, pp . 169474
10 LEUNG, K.w., el al.: 'Annular-slot-coupled dielectric
resonator antenna',Eiec tron. Lerr., 1998,34, pp. 1275-1277
1 1 SZE.J-Y., and WONG, K.-L.: 'Bandwidth enhancement of a
microstrip-line-fed printed wide-slot antenna', IEEE Tmns. Anfennus
Pmpog. ,200l,49,
67
8
pp. 1020-1024
Current-fed energy-recovery circuit forplasma display panelS a n
g - K y o o Han, Gun-Woo M o o n an d Myung-Joong Youn
A new current-fed energy-recovery circuit far B plasma display
panelis proposed. All power switcher are tumed on with
LCTO-VOIU~C-switching, an d its susw ining voltage is greatly
reduced with the aid ofthe dischargc cucrenl compensation. Funhenna
re, t fcatures a simplerstructure, less mass, lower current stress,
an d lower electromagneticinterface than prior circuits. It is well
suited for wall-hanging colourTVs.
Introduction: A plasma display panel (PDP) is now expected to be
theleading candidate for large-area wall-hanging colour TVs, since
it hasadvantages over conventional display devices, e.g. large
screen, wideview angle, and thinness. S ince a dielectric layer is
encrusted onsustaining and scanning electrodes, an intrinsic
capacitance C, existsbetween these two electrodes inherently.
Therefore, a considerableenergy of 2C,>V: far each cycle is
dissipated in the parasitic resistanceof the PDP and circuits
during charging or discharging transientswithout an energy-recoven
circuit (ERC). Furthermore, the excessivesurge charging and
discharging currents will give r ise to electromag-netic interface
(EMI) noises and increase the surge current ratings ofpower
switches. To solve these problems, a prior ERC [ I , 21 isproposed
as shown in Fig. 1. Althoug h the circuit can rzcowr mostof the
energy stored in C,, it still has several drawbacks. First, since
ithas two large auxiliary circuits, the system is complex and
bulky, andthe cost is high. Also, the large discharge current
(about 150A fo r a42 inch PDP) causes serious voltage drops across
the switchingelements and the parasitic resistance of circuits
during plasmadischarge transients. Therefore, the effective voltage
applied to thePDP decreases, as docs the accumulated amnunt of the
wall charge[2]. To overcome these drawbacks, a new ERC far a PDP
usingcurrent source type as shown in Fig. 2 is proposed in this
Letter. Sinccit has only two inductors and capacitors instcad of
the large auxilialycircuit, the proposed circuit has desirable
advantages such as asimpler stmcture, less mass, lower cost o f
production, and fewerpower switching devices. Furthermore, thcre
are no serious voltagedrops caused by the large discharge current
due to the dischargecurrent compensation, which can also greatly
reduce the currentflowing through power switches. Thus, the circuit
can maintain thepanel to light at lower sustaining voltage [ 2 ] .
In addition, the paweiswitches arc all turned on with
zero-voltage-switching (ZVS) an d thusthe proposed circuit has a
very improved EM1 and high efficiency.
pane plasma ~ ~
I , , I , b i, ,' b t o ( = t 4 ) ' t, t2 ' ' t3b
Fig. 2 Proposed cimcsir an d key w0wfovm.iU Proposed circuith
Key waveformsC i r c ui t operation: Fig. 2 shows a proposed
circuit and its key wave-forms. On e cycle period of a proposed
circuit is divided into two halfcycles, t,r, an d t2-f l . Because
the operation principles of two halfcycles are symmetric, only the
f irst half cycle is explained. C , isassumed to be charged to V J
2 . Bcfore to(= i) , c is maintdincd toV. , and V.J2 is applied to
L with M , an d M1con%ucting. Thus , i,increases linearly as ;'(I)
=- ,+V -&)/ (4L). Whcn M I and Mz are turned off at lo , mode
1begins. With the initial conditions of i,,(tO)=lL an d vc,(tc,)=
V,, i,.starts to charge C,, C, , an d C2 and discharge C, an d C,
as follows:
where C, , C,, C, an d C, are assumed to be equal to C,,, an d L
acts as acurrent source lL .With this arrangement. the abrupt
charging anddischarging operations of C,, ar e avoided and the
voltage across C,> sdecreased toward - V, . When vc,, is clamped
on - V, , V y ets to V,,and Vydrops to 0 V a t I , . M, and Mq re
htmed on and mode 2 begins.
ELECTRONICS LETTERS 10th J u l y 2003 Vol. 39 No. 74 1035
