Diode Detector Simulation, Design and Measurement

1
Diode Detector Simulation, Design and Measurement

• This tutorial has two parts (read through the
  whole tutorial before
• you start)
• How to use S-parameter data file in ADS
• The diode has S-parameters that are measured (in
  our case) or given in the Spec sheet. To
  simulate the
• Diode, you will use a 2-port Data element. To
  make the diode detector, you will add a
  capacitor.
• To match the diode detector, you will need to
  make a single stub matching network on the front.
• Then you will simulate to get the S-graphs and
  find the Zin. This will tell you how the circuit
  should
• work.
• 2. Generation of Layout
• In order to solder the capacitor and diode to the
  board, you will use solder pads. You will choose
  a
• Different diode that has the same case size as
  the one we are using, and place that with its
  solder pads.
• You will also place solder pads for the
  capacitor. Now you can no longer simulate the
  performance
• Of the circuit. This is just for layout and
  milling.
• by You Chung Chung March, 2001

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1. How to use S-parameter data files in ADS
Designing a diode detector circuit to convert AC
to DC voltage
3
These files are used for Simulation

• Use this part of the tutorial to simulate the RF
  performance of your circuit. You need to include
  the lengths of all lines (including the pads for
  soldering elements to). These are found in the
  layout section, so you will do some
  back-and-forth between layout and 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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In the second half of the tutorial, we will do
the Layout

• Artwork is used to define the size and shape of
  solder connects for components 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 the libra
  library for many standard elements.
• The size of pads add length to your lines, so you
  will need to include them in your simulation for
  most accurate results. This means you need 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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1-1. 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 for this lab
  it isnt)
• These methods are described below, for your
  reference. Measured values are given at the end.

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1-2. 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 (Matlab code to do
  this is included)

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1-3. Find the S parameters of your HP diode, Look
on this web pagehttp//www.hp.com/HP-COMP/rf/hprf
help/products/diodes/hsms285x.htms-data
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1-4. Copy and Paste the data into a text file
(diode.txt). Put this text 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 included matlab code), and
create a text file that has 2-port S-parameters
as shown on the next slide. S11 reflection
coefficient S21 1S11 S22 reflection
coefficient (1j0 for a diode) S12 1 S22 (or
in this case, for a diode, it is zero)
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1-5. Measured 2-port S-parameters of your diode
including the padsfilename 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 0 2.0 0.9683 -29.8098 1.9021
-14.6593 0 0 1.0000 0 2.4
0.9521 -35.1478 1.8610 -17.1282 0
0 1.0000 0 2.6 0.9529 -35.7572
1.8586 -17.4327 0 0 1.0000
0 3.0 0.8956 -44.0234 1.7578 -20.7357
0 0 1.0000 0 !END
Copy diode2pt.txt to the data folder in your
current project directory.
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1-6. Get a Part by typing S2P in the part window
Edit Parameter
Double Click on S2P or Edit/Component/Parameter
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1-7. Adding Zin block, MLIN, MLOC, MTEE and S2P
To make the circuit add MLIN, MTEE, MLOC Also
add S parameter and MSub blocks and Zin block to
measure Zin. Get s2p
50 ohm lines
About 1
Short (1/4-1/2)
To find Zin Go to Simulation-S_Param and select
S Zin block
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1-8. Simulate your Circuit to find Zin
Make this circuit, simulate it and look at the
output graph.
Zin block
Assuming that the values to substitute
are calculated.
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1-9. Edit C_pad1 Parameter Define C, W,S,L from
the data sheet. Units are from your
default.(C_pad1 represents a capacitor WITH its
solder pads.)
Units here are pF and mils
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1-10. Insert S2P parameter file
Insert S2P parameter file Double clock on S2P
part and insert parameter file into the File name
window. Copy the file into data directory under
current working project directory
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1-11. Simulate the circuit and look at the graph
(Data Display)
Add the rectangular plot.
Then select our_zin to plot from the
Plot Traces Attributes Click Add
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1-12. Data Display
Select Real part and click ok Again select
our_zin and click add. Now select
Imaginary part and click ok
Now click ok in the Plot window
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1-13. The Zin Plot, Add markers at 2.4 GHz and
2.6 GHz on both the curves
This plot shows the real and imaginary parts of
Zin Use these values to design your single stub
matching network and also plot on the Smith Chart.
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1-14. Add your single-stub network to the circuit
Remove the Termination and add your single
stub and simulate Use Tune and match to get low
S11 in dB
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1-15. Data display after simulating
Now plot S(1,1) in dB The curve should look like
this. You get the matching at the frequency for
which you designed your single stub. (2.4GHz)
in this case. You should get another curve for
2.6GHz circuit
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2. Generation of Layout

• You have now simulated how your circuit should
  work, but you cant mill it. The mill will not
  know what to do with the S2P element and wont
  leave any particular solder pads for the
  capacitor.
• In this part of the tutorial, you will prepare
  the circuit to be soldered, but wont be able to
  simulate its performance.

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Use of Layout

• Artwork is used to define the size and shape of
  solder connects for components 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 the ADS
  library for many standard elements.
• The size of pads add length to your lines, so you
  will need to include them in your simulation for
  most accurate results. This means you need 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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2-1. Get a diode from Component Library.
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2-2. Select diode from part library that is the
same case size as ours
It is under HFDiodeLibrary/High Frequency Diode
di_hit_hsm88as_19930908
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2-3. Replace the 2-port data element with the
Diode and artwork
Assuming that you know where to find the
diode MBEND2 can be found under Tlines_Microstrip
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2-4. Click on the Layout and then Generate/Update
Layout
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2-5. Click OK on the message
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2-6. Layout with the diode
Ground for extra diode pin
Single Stub Matching Network
Read VDC here
Cap Space
Diode
Ground
You can also plot without the single stub
matching network
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Remove the Diode

• Remove all parts that will be soldered on (diode
  and capacitor) before saving the file to be
  milled.
• If you dont, it will mill their outline and
  mess up your board.

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2-7. Layout without the DiodeThis is what you
should mill.
Remember to put the holes for all the
shorts(ground, short ckt., stubs, etc) when you
mill the circuit
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What to turn in

• Design two diode detectors, one for 2.4 GHz, and
  the other for 2.4 GHz. (Slight change in single
  stub match.)
• Print out the layout of your diode detectors,
  with sizes clearly marked.
• Clearly mark where holes for shorts should go
  (there will be two on each detector).

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Question?

• If you didnt get something in this tutorial,
  please tell Dr. Furse or You Chung which slide(s)
  is confusing.
• Thank you!