Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

How to know Proper Values for ZL and ZS , Load Pull and Source Pull in ADS

Amir.Sk

Newbie level 6
Joined
Jun 8, 2019
Messages
13
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
127
Hi everyOne!
first things first: I'm new to this stuff!

I'm trying to design an amplifer with a GaAs Design kit.
CAD : ADS
frequency = 1 tone 10.7 GHz
tried to bias it for Class A operation.
stabilized it.
now I'm trying to do load pull and source pull.
I'm just wondering to know the proper range for ZL and ZS?! I mean , I'm getting something from source pull to place at source. but it seems unusual!

please take a look at the procedure :

1-DCIV simulation => class A : VD = 8 & VG = -.5 has been selected.
IV-Curve.png
2- Stability Check , and making it stable with L&S stabling circles : push 9GHz circle back.
Stability.png
3- Load Pull and then load pull and getting 52 +j*52 for the Z-Source which made me think that HOW SHOULD I KNOW THAT THIS IS WOULD BE FINE? for a 150um Gate (UG = 75um and NOF = 2) GaAs Transistor?!!
Source Pull.png


Thank you for Your time!
Surely let me know what basic things I should learn
 

BigBoss

Advanced Member level 5
Joined
Nov 17, 2001
Messages
4,705
Helped
1,426
Reputation
2,850
Reaction score
1,289
Trophy points
1,393
Location
Turkey
Activity points
28,445
Load Pull and Source Pull Analysis is done for those design metrics..

-Max. Efficiency for Power Amplifiers OR
-Max. Gain for an Amplifier OR
-Max. Delivered Power for Power Amplifiers

They cannot generally be obtained simultaneously.You have to decide which is more important for you then you analyze in regard of these three..
 

Amir.Sk

Newbie level 6
Joined
Jun 8, 2019
Messages
13
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
127
Yeah, I’m aiming for best PAE possible and the values that I talked about are all based On best PAE. My question is wheter the values are normal or not? 52 ohm for 75um device?
 

vivekroy

Full Member level 5
Joined
Jan 19, 2019
Messages
245
Helped
100
Reputation
200
Reaction score
97
Trophy points
28
Location
N/A
Activity points
1,660
For max PAE, the I would think that the gain needs to be as high as possible and therefore you need to conjugately match at the input. With the source impedance you are getting from source pull, check your s11. It should be very low.
 

BigBoss

Advanced Member level 5
Joined
Nov 17, 2001
Messages
4,705
Helped
1,426
Reputation
2,850
Reaction score
1,289
Trophy points
1,393
Location
Turkey
Activity points
28,445
Yeah, I’m aiming for best PAE possible and the values that I talked about are all based On best PAE. My question is wheter the values are normal or not? 52 ohm for 75um device?
Nobody knows it..We don't have enough information about your semiconductor devices and their characteristics..
But I think you make some serious mistakes while simulating the circuit.I cannot say 52 Ohm is not proper value but seems weird.
Power Amplifiers have generally low Optimum Load Impedances in order to drive with higher currents due to low supply voltage.
For instance a PA may have 2+j*3 Ohm or similar values for Optimum PAE or Pload. You ought to double-check your simulating environment.
 

vivekroy

Full Member level 5
Joined
Jan 19, 2019
Messages
245
Helped
100
Reputation
200
Reaction score
97
Trophy points
28
Location
N/A
Activity points
1,660
I used to get values like 20-25 ohms at 28GHz for a SiGe transistor (after layout). Most of it used to come from the internal base resistance. I have no idea about GaAs devices though.
 

Amir.Sk

Newbie level 6
Joined
Jun 8, 2019
Messages
13
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
127
You were right guys. Something is seriously wrong!
I have tried S-params simulation and I got terrible results with that ZL and ZS in hand! Hence I'd tried a somehow tricky simulation: changed the terminations Impedance on both side of the circuit till I get a notch on both S11 and S22 in the desired frequency.

notch.png

I came with these 2 values in hands: Zs= 15.352 + j*44.738 and ZL=55.393 + j*164 which are far from what ADS Load-Pull gave me : ZS = 52 + j*52 and ZL=165.282 + J*96.46
which seemed to be correct: (e.g load-pull)
egloadpull.png

also I think its important to mention that I am setting my number of harmonics in load-pull and source-pull to 1 ! because setting them to 2 or 3 made so much confusion and I could not get a single contour on data set page!

someone please help this young lost guy who wanna be a designer! :???:
 

vivekroy

Full Member level 5
Joined
Jan 19, 2019
Messages
245
Helped
100
Reputation
200
Reaction score
97
Trophy points
28
Location
N/A
Activity points
1,660
You were right guys. Something is seriously wrong!
I have tried S-params simulation and I got terrible results with that ZL and ZS in hand! Hence I'd tried a somehow tricky simulation: changed the terminations Impedance on both side of the circuit till I get a notch on both S11 and S22 in the desired frequency.
The load impedance that gives you a notch for s22 will probably not be the same as the one where you get your maximum PAE. Your optimum impedances for maximum power, maximum gain and maximum PAE will be close, but in general the impedances cannot be same always. s22 is typically never that great for any practical amplifier (because you almost always match for maximizing output power or maximizing power added efficiency).
 

Toggle Sidebar

Part and Inventory Search


Welcome to EDABoard.com

Sponsor

Sponsor

Design Fast


×
Top