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Simulators >> RF Simulators >> Modulated Waveform Generator in Cadence
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Message started by debopriyo on Feb 21^st, 2006, 11:53pm

Title: Modulated Waveform Generator in Cadence
Post by debopriyo on Feb 21^st, 2006, 11:53pm

Hi,

I want to test my mixer and PA with different types of modulated waveforms. I need some help as to how I can generate these modulated waveforms in Cadence, their eye diagram etc.

Thanks a lot!
Debo

Title: Re: Modulated Waveform Generator in Cadence
Post by Andrew Beckett on Feb 22^nd, 2006, 7:51am

There are some behavioural models in rfLib for example, and also you can use modelwriter to generate some.

Andrew.

Title: Re: Modulated Waveform Generator in Cadence
Post by debopriyo on Feb 22^nd, 2006, 10:00am

Hi Andrew,

Thanks for your help! Since I am pretty new in this area, would it be possible for you to kindly give some more details or refer me to some document that explains how I can generate various envelop/modulted signals in Cadence RF Spectre?
Thanks a lot,
Regards, Debo

Title: Re: Modulated Waveform Generator in Cadence
Post by debopriyo on Feb 22^nd, 2006, 1:05pm

ok let me be more specific..i want to create an OFDM modulated signal to test the spectral regrowth of my PA in a 802.11a system. If you could please provide some details on how to generate the signal, Ill be grateful!
Thanks a lot,
Debo

Title: Re: Modulated Waveform Generator in Cadence
Post by Andrew Beckett on Feb 23^rd, 2006, 5:09am

We don't ship an OFDM modulator behavioural model with the tools. I know one has been developed by our services organisation, but one is not shipped by default.

There is some stuff on this in the SpectreRF User Guide (can't lookup right now because my laptop is being re-imaged, and the machine I'm on is far too slow...) - at least for doing envelope simulations, with some examples using other modulation schemes (e.g. CDMA).

You'd need to either contact Cadence to ask about whether they could supply the OFDM modulation example, or write your own in Verilog-A.

Sorry for the short answer - I don't have much free time this week.

Best Regards,

Andrew.

Title: Re: Modulated Waveform Generator in Cadence
Post by Jess Chen on Feb 23^rd, 2006, 8:43am

Debo,

You should not generate your test waveforms in a vacuum. The digital and analog baseband engineers usually work together to generate a waveform that meets spectral mask with margin for spectral regrowth. Since the impairment budget is not unique, you may want to have some baseband customers in mind. If you have any baseband partners, you should be able to get some baseband waveforms from them. You can then filter and mix up to RF for your PA simulation. You can read the data from files into your Spectre simulation with pwlf sources. The rfLib has modulators for mixing up to RF but you can probably do it just as easily yourself with ideal multipliers from the ahdlLib. The baseband data must be filtered to trim the "dog ears" at the harmonics of the sampling frequency. Your transmitter systems engineer should have the filter specifications, if not a ready-to-use behavioral filter model. The sampling frequency and analog filters are extremely important in generating the proper test waveforms.

You will eventually have to test your PA in the lab. Some lab equipments generate sample OFDM waveforms. If you have some fast sampling scopes, you could grab the OFDM waveforms from your test equipment. You only need do this once. Again, you then import the data into your simulation through the pwlf sources.

-Jess