The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl Simulators >> RF Simulators >> Problem of Simulting a Gilbert Multiplier https://designers-guide.org/forum/YaBB.pl?num=1234783833 Message started by Jack on Feb 16th, 2009, 3:30am |
Title: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 3:30am Dear All, I am simulating a Gilbert Multiplier. When I start with the noise figure simulation, the results is 140dB. This result is a little carzy. Also I have seen some topics about the simulation of Mixer. But I think mixer is a little different from multiplier. For mixer, I think if the switching transistor does not contribute the noise, the analysis is similar with the common-source cascade LNA. But for multiplier, the switching transistor also contributes the noise, but for the input transistor of RF signal, its noise is mainly common-mode noise at the output of multiplier because the input transistor of template signal is always working in saturation region. So in this case, how can I simulate the noise figure correctly? Some description of my multiplier: double balanced Gilbert multiplier, but there is no current tail at the bottom to increase the voltage headroom. application for 3-5GHz Impulsed UWB receiver. RF input port is 5GHz sinewave port(50ohms), template signal is also 5GHz sinewave port (50ohms). The output port is 50ohms (dc). there is no impedance matching at each port. Because I am not familiar with PSS simulation and QPSS simulation, which one should I use, how can I set up the parameters? I am appreciating your help! Jack |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 3:46am Also, for Mixer, the LO signal is a frequency-fixed signal, but for Multiplier, the template signal is the same one with the RF input signal for coherent detection. |
Title: Re: Problem of Simulating a Gilbert Multiplier Post by pancho_hideboo on Feb 16th, 2009, 4:44am I can't find out any problem in your post. Your post is not design issue but just very simple common usage of simulator. Jack wrote on Feb 16th, 2009, 3:30am:
What value is conversion gain ? Jack wrote on Feb 16th, 2009, 3:30am:
PSS is a expansion by single frequency basis while QPSS is a expansion by multiple frequency bases which have no common divisor frequency each other. If your questions are usages of very specific EDA vendor's simulator, post to "The Designer's Guide Community Forum ≫ Simulators ≫ RF Simulators". Jack wrote on Feb 16th, 2009, 3:30am:
Jack wrote on Feb 16th, 2009, 3:30am:
Jack wrote on Feb 16th, 2009, 3:30am:
as four quadrant multiplier and as mixer such as down converter or up converter ? But there is no difference about treatment of them in simulation, even though they works as multiplier or mixer. Jack wrote on Feb 16th, 2009, 3:30am:
Jack wrote on Feb 16th, 2009, 3:46am:
Jack wrote on Feb 16th, 2009, 3:46am:
I think this is zero-IF mixer or matched detection. Anyway there is no difference about treatment in simulation. |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 6:57am Thank you very much for your guidance. This mulplifier is used for coherent IR-UWB receiver. It looks like a down-converter. But it works like a square law. If the RF input is Asine(wt), the template signal is like the LO signal, but not as strong as LO signal, so the input transistors are working in saturation region all the time, not like intput transistors of LO signal, they are working between on and off. the template signal is the same one with RF input signal Bsine(wt). So the output is ABsquare(sine(wt)). In my application, this multiplier should work in the time domain. But because it is connected with the Low noise amplifier, so the noise figure is also very important for me. I put an architecture here. |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by pancho_hideboo on Feb 16th, 2009, 7:08am Jack wrote on Feb 16th, 2009, 6:57am:
There is no special issue about treatment in simulation. Your diagram is RF matched detection(correlation detection). Jack wrote on Feb 16th, 2009, 6:57am:
|
Title: Re: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 7:13am The circuit is as follows |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 7:20am Until now, I didn't simulate the conversion gain, I just simulate the noise figure, 1. Do I need to set any input matching? Now I am simulate the multiplier seperately. But the multiplier will be connected to LNA at last, 50ohms matching is not fit in this case. 2. I follows the general mixer simulating method. the RF input port, I set the parameters as follows: 50ohms, dc the Template port: 50ohms, sine, 50mv, 5GHz. the Output port: 50ohms, dc PSS setting: |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by pancho_hideboo on Feb 16th, 2009, 7:22am Jack wrote on Feb 16th, 2009, 7:13am:
Very common circuits. It is not novel at all that there is no tail current. I can't understand what you are confusing. |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 7:23am Pnoise setting: |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by pancho_hideboo on Feb 16th, 2009, 7:26am Jack wrote on Feb 16th, 2009, 7:20am:
Do you have basic knowledge of RF circuit and system ? In your case, common standard Friis's equation for cascaded NF is not satisfied. |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by pancho_hideboo on Feb 16th, 2009, 7:29am Jack wrote on Feb 16th, 2009, 7:23am:
Again do you understand DSB_NF, SSB_NF(USB or LSB) correctly ? |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 7:30am The noise figure in Pnoise is |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 7:33am DSB_NF, SSB_NF(USB or LSB) For DSB_NF and SSB_NF, I think I know the conception, but for USB and LSB, I do not. |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by pancho_hideboo on Feb 16th, 2009, 7:36am Your question is no more than very specific EDA vendor's Tool Play not Design Issues. Maybe other people who are kind hearted and very patient will help you. |
Title: Re: Problem of Simulting a Gilbert Multiplier Post by Jack on Feb 16th, 2009, 7:39am Thank you very much! I change the reference sideband to -1, then the noise figure is decrease much. Do you think this noise figure is reasonable? This is my first time to simulate the multiplier, I have no idea of it. |
The Designer's Guide Community Forum » Powered by YaBB 2.2.2! YaBB © 2000-2008. All Rights Reserved. |