olddiode_old.ppt

8/10/2019 olddiode_old.ppt

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How to use S-parameter data files

in ADSRay Woodward

Cynthia FurseUtah State University


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This tells how to design a diode detector

circuit to convert AC to DC voltage

Read through the whole tutorial before you start.You will go through two sections:Simulation and Layout


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Simulation

Use this (as you have in previous tutorials) to simulate the RF performance of your circuit. You need to include the lengths of alllines (including the pads for soldering elements to). These are found in

the layout section, so you will do some back-and-forth between layoutand simulation. Some elements are available in the standard libraries (the cap in this

lab), others are not (the diode in this lab). When they are not available,you will have to create them using user -defined S-parameters and

lines (MLIN). These can come from data sheets (like the HP website)or from measurements (like for this lab).


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Layout:

Artwork is used to define the size and shape of solder connects forcomponents like capacitors, diodes, RF chips, etc.

The dimensions of solder pads (where you actually connect your

circuit) are specified on data sheets. They are also available in thelibra library for many standard elements.

The size of pads add length to your lines, so you will need to includethem in your simulation for most accurate results. This means youneed to figure out their size before you simulate the circuit, so you will

do some back-and-forth between layout and simulation.


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There are two ways to get your S-

parameters: Measure them (most accurate) Find them on the web or other data sheet

(wed like this to be most accurate, but forthis lab it isnt)

These methods are described below, foryour reference. Measured values are givenat the end.


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To measure S-parameters of the

diode Build the circuit with just a length of line

attached to the device. Measure the input impedance using the

network analyzer Compensate for the length of the line to find

the S-parameters of your device (matlabcode to do this is included)


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Copy and Paste the data into a text file (diode.txt). Put thistext file into your project directory.

S11 (Mag, Phase(degrees))


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You may have measured or acquired only the S11 values of a diode.

Find the other S-parameters (such as with the matlab code found athttp://www.engineering.usu.edu/classes/ece/6130/LECTURE/LAB/L4/CalcSparam.m),and create a text file that has 2-port S-parameters as shown on the

next slide.S11 = reflection coefficientS21 = 1+S11S22 = reflection coefficient (1+j0 for a diode)S12 = 1 + S22 (or in this case, for a diode, it is zero)


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Measured 2-port S-parameters ofyour diode including the pads:

filename is diode2pt.txt!BEGIN ACDATA# GHz S MA R 50.0!% F n11x n11y n21x n21y n12x n12y n22x n22y

1.75 0.9683 -23.8255 1.9259 -11.7179 0 0 1.0000 02.0 0.9683 -29.8098 1.9021 -14.6593 0 0 1.0000 02.4 0.9521 -35.1478 1.8610 -17.1282 0 0 1.0000 02.6 0.9529 -35.7572 1.8586 -17.4327 0 0 1.0000 03.0 0.8956 -44.0234 1.7578 -20.7357 0 0 1.0000 0!END

Copy diode2pt.txt to the data folder in your current projectdirectory. You can find this file here:http://www.engineering.usu.edu/classes/ece/6130/LECTURE/LAB/L4/diode2pt.txt


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Select Data Items

Select 2-port S-parameters


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You will get a 3-port picture of a diode. Add a ground to theextra port on the bottom


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Next, we will add a capacitor

with solder pads


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Choose Lumped Element with

artwork C_PAD1.

Set size:C=100pFW=60milS=20 milL=80 mil


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Add components as needed:

(Explanations follow)


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Diode and Capacitor

Capacitor withlayout artworkfor solder pads,good for simulation

and milling.

Your diode S-parameters will be here for simulation.

For milling, you will need artwork instead. Coming up.

A shortlength of line todrill for ground pin

Di d S ld d


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Diode Solder pads IF you use diode S-parameters from the HP website, you will need to add the

solder pads (which add length of lines). Find the size of solder pads in the datasheets OR the diode artwork. (See layout slide # 27 below.) Do NOT add these

pads if you are using measured data, because they are already part of the

measurements.

Pads for solderingyour diode. Use 30x30mils. This can befound from diodeartwork (layout slide)to determine thesize. Leave them OUTfor simulation.

Ground extra pin on diode package

For simulation you would use this instead, direct to ground.


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Now: Simulate the circuit and find Z 11 for both

frequencies (2.4 and 2.6 GHz) Use Tline or Smith Chart to design a stub-

matching network. Follow the single-stub tutorial from here to

add a stub matching network to the front ofyour circuit.


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For better matching

See the diode detector handout. A 100-ohm line for the distance d between

the diode and stub and a 50 ohm stub willusually give a better match.

Simulate the circuit with stub to be sureyour matching is good.


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Layout:

Everything is OK for the layout except for your diode. TOdo this, we need to remove the S-parameter box and replaceit with a diode with artwork.


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Find HFDiodeLibraryClick on +

Click on High Frequency

Choose any SOT23 packageFor grounding the extra pin,the 88a is suggested.


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Here is the diode with artwork. The hsms2850 diode we hasthe diode opposite those shown in the artwork. This is whyyou cannot accurately simulate when you are using artwork.

This is for LAYOUT only.


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Synchronize, and take to layout.This is what it looks like without

your matching circuit

Diode

Capspace

Look here to find thesize of diode solderpads for including in

your simulation.

Ground for extradiode pin

Read

VDC here

Ground


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Delete the diode from the picture to be milled, but rememberwhat it looks like for soldering the diode.

Be sure to addhalf the THRU plusyour stub matchhere before milling


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Remember to put holes for all the shorts (ground,short ckt. stubs, etc.) when you mill the circuit

There may also bea short on your stub.


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