RF Amplifier_GAN - Page 1
Forum section: electronics / rf-microwave

author: Nahim
author_rank: Contributor
timestamp: June 19, 2023, 07:31:31 pm
content: Comrades, tell me what could be the problem, in AWR I threw in an amplifying stage circuit on one GAN transistor, everything seems to be in order, I see both amplification and normal matching.The problem is that when I do an extract in EM to optimize, the gain drops to MINUS 20dB and no matter how I try to optimize it, to no avail.The voltage at the DRAIN of the transistor drops from + 28V to 700mV, it seems that the transistor opens completely and shorts the entire power line.But why is everything in order before extracting the structure in EM ! ?And another oddity, if I connect an additional library component to the circuit, for example, an inductance, and supply power through it DIRECTLY to the DRAIN of the transistor, BYPASSING the microstrip lines, then everything is in order and the transistor starts working ...It seems that the microstrips SAG from the current .. (but they shouldn’t, they are quite wide)Who can faced the similar phenomenon?

author: BigBoss
author_rank: Regular Contributor
timestamp: June 19, 2023, 11:48:04 pm
content: Did you include DC ( 0 Hz ) in your EM simulation set-up ??Because when you do an EM simulation, AXIEM creates a netlist for ALL Ports defined by s-parameters.If you did not include DC frequency someundesired weird results might occur. s-parameters have discrete nature and that's why there might be stupid errors for DC currents and voltages.It might also be a convergence problem. General speaking, the simulators do not like floating nodes, very high/very low extreme inductance and capacitance values,unrealistic current and voltage loops etc. You have to avoid to use those constaints.Ports may be sometimes troublesome. They are calibrated while simulator is running and if a port is sticked to a large plane or very close ports cannot be co-calibrated.EM simulation is really tricky.

author: Nahim
author_rank: Contributor
timestamp: June 20, 2023, 09:46:01 am
content: "Did you include DC ( 0 Hz ) in your EM simulation set-up ?? "I don't know, I used the default settings, just set the working bandwidth and the required signal level on port 1.And where can I see this frequency for DC?By the way, HARMONIC BALANCE SIMULATOR - works fine! Problem only when using APLAC HBDoes it make sense to use HARMONIC BALANCE SIMULATOR? Is he accurate?

author: BigBoss
author_rank: Regular Contributor
timestamp: June 20, 2023, 01:33:07 pm
content: Quote from: Nahim on June 20, 2023, 09:46:01 amAs I have said before, it's a convergence error and it appears very frequently in such similar cases.You should manually add 0 Hz to frequency list. Because even tough s-parameters are not defined for 0 Hz, EM simulator will take very very low frequencies into account in order to work with DC.HB simulator and APLAC are similar engines and there is no significant difference between them. APLAC has more additional settings to improve the results. HB is good enough for your case.You can also use SONNET EM simulator if the layout has less than 4 ports ( Sonnet Lite, it's free ) and not very complicated to mesh very dense. ( memory constraint )Sonnet has a more accurate engine for DC-like ( very low frequencies ) problems. You can configure Sonnet in AWR and choose it as main simulator.Good luck.[ Specified attachment is not available ]

author: Nahim
author_rank: Contributor
timestamp: June 20, 2023, 03:49:28 pm
content: Really thanks a lot!!!!!

author: Nahim
author_rank: Contributor
timestamp: June 21, 2023, 03:07:14 pm
content: I tried, but to no avail, the increase shows MINUS 10dB GAIN,but as soon as I switch to the HARMONIC BALANCE SIMULATOR I see normal +11dBBoth simulators are running ... but the difference in readings is obvious

author: BigBoss
author_rank: Regular Contributor
timestamp: June 21, 2023, 08:07:28 pm
content: Quote from: Nahim on June 21, 2023, 03:07:14 pmCan you post your AWR archived project file here to inspect together ??

author: Nahim
author_rank: Contributor
timestamp: June 22, 2023, 12:17:03 am
content: I put it on a file hosting service, since it weighs 7500kb.Here you can only transfer up to 5000kbhttps://easyupload.io/di8py4I would be very surprised if you manage to find a problem ... Ready to thank you through PayPal.

author: BigBoss
author_rank: Regular Contributor
timestamp: June 22, 2023, 02:42:54 am
content: Quote from: Nahim on June 22, 2023, 12:17:03 amThis won't work. You have to "Archive" the project with ALL Library included. It will create a file with an extension *.emz ( File-->Archive Project )I don't need TEMP and DATA_SETS Directory. Also you used Modelithics library but I do not have a right to access. But anyway, I will checkyour EM simulation set-up.

author: Nahim
author_rank: Contributor
timestamp: June 22, 2023, 09:03:12 am
content: https://easyupload.io/lmvfz1Here is a new download link, the file has become heavier

author: BigBoss
author_rank: Regular Contributor
timestamp: June 23, 2023, 01:36:31 pm
content: OK, I have understood your problem.When you simulate your system with Input/Output schematic equivalent of the layout, there is no problem. HB converges well.But if you change the the same circuit with EM simulated block, convergence error occurs because there are some capacitors are not taken into accound along EM simulation.In otherwords, they are not recognized as component or modelThere are also gaps with Ports somewhere.So, since these are not taken into account, the circuits becomes missing and therefore convergence error occurs.All you have to do is to create a symbol ( either black box or layout look-like) then connect the same components at corresponding ports.In order to create a symbol use "Symbol Wizard" and choose either black box type or layout look-like.I have attched a sample to compare with schematic and EM simulated layout and there is almost no difference between them.MWOffice does not have Co-Simulation feature like ADS. You can choose which simulation view will be considered while simulating but AWR does not give this opportunity.( Therefore I always prefer ADS )Example:

author: Nahim
author_rank: Contributor
timestamp: June 23, 2023, 04:06:00 pm
content: Thank you very much and thank you for not being lazy!You really helped me...Tell me your paypal, i will thank you....And how accurate is CO-Simulation in ADS compared to CST studio?

author: BigBoss
author_rank: Regular Contributor
timestamp: June 23, 2023, 06:50:39 pm
content: Quote from: Nahim on June 23, 2023, 04:06:00 pmYou're welcome, never mind.CST Studio is essentially not developed for co-simulations, intead CST studio is very useful for large EM problems such as antennas, Radar Cross Section problems, EMI issues of large structures etc.ADS is pretty accurate for such layout+component designs. I have designed more than 100 system and the results were very close to measurements.If your model is sufficiently accurate and if you set-up EM analysis part well, you'll get always accurate results.Simulators are speciallly developed calculators, if you enter the right data, you get accurate results.

author: Nahim
author_rank: Contributor
timestamp: June 23, 2023, 09:28:21 pm
content: ADS is good for everyone, but there is only one drawback - it is laborious to get EM from a schematic editor.In AWR, getting EM (AXIEM) is very easy, that's the advantage.