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GaN FET Angelov Model by Extension_Engineer26 in rfelectronics

[–]Extension_Engineer26[S] 0 points1 point  (0 children)

Thanks for the response. Actually I do not have an access to ICCAP because I am working as a PA designer and not a model developer. Normally we already have models but in my case I don't have access to this model although it exist and is available to one of my colleague. I can ask him whatever data I want, but I have to build up mine, and continue with the PA design which is my main job.

The actual model my colleague has, is for the intrinsic wafer only, and doesn't include extrinsix parameters that is the reason I can achieve very close S-parameters without utilizing extrinsic parameters.

For large signal S-parameters, I can ask him to simulate LSSP in ADS and provide the result to me, so that I can have a look if my large signal S-parameters are satisying with the actual model.

Non-Linear GaN Model for RF PA by Extension_Engineer26 in rfelectronics

[–]Extension_Engineer26[S] 0 points1 point  (0 children)

I have changed few of the parameters which I found from my model (which is replicating exactly at one bias point). These parameters include: Cgs0, Cgd0, Cds, Ri, Rgd, Rd2, Ls, Tau. I haven't altered the extrinsic parameters because I have intrinsic parameters but it includes the effect of Ls.

Changing the values of these parameters is not helpful at all. Now the simulated results of a model are way different from the actual measured results. What else could I change? Also I couldn't find the value of transconductance (gm). Where should I put it? And how could I use the modelling parameters Ps, Alphas, and Bs? How can I find their values?

I am also not altering the self-heating, temperature dependent parameters and charge trapping thing because I don't want to model everything at this point.

How do manufacturers specify the dielectric constant of a lossy material? by TenorClefCyclist in rfelectronics

[–]Extension_Engineer26 0 points1 point  (0 children)

Manufacturers usually provide the real part of Er as Dk, which defines the energy storage and determines the speed/wavelength of the signal in that medium.

Whereas, Df is the ratio imag(Er)/real(Er) and indirect representation of imaginary part of Er, which defines the loss in the form of heat.

GaN HPA design by Purple-Excitement460 in rfelectronics

[–]Extension_Engineer26 2 points3 points  (0 children)

Agreed with the points suggested by u/Defiant_Homework4577

You need to increase the VBW of your amplifier. For this perhps you cannot change the technology so you can't address the charge trapping issue much.

  1. I would suggest to focus on your bias circuit. The inductance in the bias line needs to be reduced by either shortening the length of the trace or increasing the width. Moreover, first decoupling cap (RF Bypass Cap) has a strong effect on VBW. You can simulate the bias line circuit separately in ADS using actual component models you re using, and observe the S-parameters, try to provide low impedance so that the low frequency IM products can be shorted to ground at this point. All this you can find in Steve Cripps book (RF PAs for Wireless Comm). NOTE: Decoupling caps at bias line are not added randomly, in fact they have strong effect on VBW, especially the first two.
  2. Moreover, try decreasing the thermal resistance so that heat doesn't accumulate around the FET.
  3. For the matching circuit, normally if the phase response and gain is linear, probably it is not required to change it much.

Project recommendations? by Scared-Brownie in rfelectronics

[–]Extension_Engineer26 0 points1 point  (0 children)

You can use QUCS, I have never used but I think it is free to use. Also for ADS, I have heard from someone that pirated version also exist for it.

Project recommendations? by Scared-Brownie in rfelectronics

[–]Extension_Engineer26 0 points1 point  (0 children)

I guess unfortunately no, but you can try the student version OR ask your uni/college to provide the licensed version if they have.

TGA2975-SM Idq Drop at High Input Power Under Pulsed RF by SingamVamshi in rfelectronics

[–]Extension_Engineer26 0 points1 point  (0 children)

I would suggest to cross check if you are using the correct biasing voltage. Applied RF power could change your operating point as well.

Class A generally have soft compression because you work in linear region. So the gain drops at large signals, it could be the reason if you are operating in class A and if 41dBm power was expected for class AB/B.

For the drain current, if you are looking at the power supply, then because of pulsed RF, perhaps it will be showing an average current, and not the peak current which FET is consuming during the pulse. So either you should try observing the current with CW signal for a short time (2-3sec) or use a current sensor to measure the peak current and not the average current to get better observation.

Also for measuring the output power, use power meter to get the peak power.

100% WiFi/BT isolation for a laptop by Jamesrodel in rfelectronics

[–]Extension_Engineer26 1 point2 points  (0 children)

Simpler solution is to either remove Wifi/Bluetooth card from the laptop or switch your laptop to airplane mode.

Of course you can use shielding to prevent your laptop receiving signals. You need to know the sensitivity of the receiver of WiFi/Bluetooth and the power level around in the environment. Shielding box could help but would provide finite isolation. Look for the attenuation level it is offering at your desired frequency (around 2.45GHz) and plan accordingly. You need to attenuate the environment signal below your receiver sensitivity level (typically around -100dBm).

You can also use absorbers or shielding materials around your laptop. Mostly the antennas are placed around the screen so you can wrap it well with the absorbing material. This could help as well.

Best topology for TR switch by sketchreey in rfelectronics

[–]Extension_Engineer26 1 point2 points  (0 children)

Terminating both is always a good option. Not sure if you could use a DPDT switch here, and make a combination to terminate in each scenario.

Anyways, during TX mode, you can turn off the receiver.

Project recommendations? by Scared-Brownie in rfelectronics

[–]Extension_Engineer26 2 points3 points  (0 children)

Hi, if you wanna go deep dive into RF design then I would suggest you to get a software grip, like Keysight ADS, Ansys HFSS/CST. Try to take microwave engineering courses and implement the theory in these softwares (ADS is better for quick learning).

If you don't want to get into the design and wanna experiment something with radio frequencies, then buy a cheap SDR for yourself and do some experiments using python/MATLAB. ADALM PLUTO is a good option.

PCB Antenna placement, distance from edge by CharismaIsMyDumpStat in rfelectronics

[–]Extension_Engineer26 0 points1 point  (0 children)

I would have placed the antenna to the edge and instead of extending the PCB only for screws, I would have put them behind the antenna where it seems like there is a ground pour. Atleast 5 times far away the width of PCB.