The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl Simulators >> Circuit Simulators >> AM Modulation. https://designers-guide.org/forum/YaBB.pl?num=1263572424 Message started by ic_engr on Jan 15th, 2010, 8:20am |
Title: AM Modulation. Post by ic_engr on Jan 15th, 2010, 8:20am Hello, I am trying to simulate an effective GSM signal which has GMSK modulation. What I need to set-up is 1kH AM with 80% modulation on a 900MHz carrier. Can anyone tell me if I can set this up in Spectre/Cadence using the standard analogLib sources or ahdl models ? Will greatly appreciate any suggestions. ic_engr |
Title: Re: AM Modulation. Post by pancho_hideboo on Jan 15th, 2010, 8:39am ic_engr wrote on Jan 15th, 2010, 8:20am:
Do you mean a generation of GMSK by QAM ? GMSK is no more than a FSK. But it has amplitude variations due to limited bandwidth. http://en.wikipedia.org/wiki/GMSK#Gaussian_minimum-shift_keying http://edocs.soco.agilent.com/display/ads2009/GMSK+Mod http://edocs.soco.agilent.com/display/ads2009/PtRF+GSM+%28Pwr+Src%2C+RF+Carrier+Modulated+by+GSM+Signal%29 If you use Cadence Spectre, use "rfLib/GSM_xmtr" and "rfLib/IQ_modulator". If your need is a generation of simple AM signal truely, see the following. http://www.designers-guide.org/Forum/YaBB.pl?num=1233850018 |
Title: Re: AM Modulation. Post by ic_engr on Jan 20th, 2010, 5:59am I did use the GSM_xmt in rfLib in Cadence. However it does not let me control the frequqeuncy. Would you know how I can use it. The only parameter controllable is the 'seed' and the amplitude ? Notice the GSM has a frequency of 900MHz or 2GHz. I would like to try different frequencies from 900MH to 2.5GHz in my simulation. Noticing the 'seed' parameter makes me think this is a random number generator. ic_engr |
Title: Re: AM Modulation. Post by pancho_hideboo on Jan 20th, 2010, 6:03am Answer my question. Is there any relation to AM regarding GMSK ? "rfLib/GSM_xmtr" is baseband I and Q signal generator. If you use these I and Q signals as RF signal, use "rfLib/IQ_modulator" with "rfLib/GSM_xmtr". |
Title: Re: AM Modulation. Post by ic_engr on Jan 20th, 2010, 10:51am I believe its a constant envelope, therefore, you are right no AM modulation relation exists for GMSK. ic_engr |
Title: Re: AM Modulation. Post by ic_engr on Jan 22nd, 2010, 5:34am The I&Q modulator still does not allow me to specify the modulation index. ic_engr |
Title: Re: AM Modulation. Post by pancho_hideboo on Jan 22nd, 2010, 5:41am ic_engr wrote on Jan 22nd, 2010, 5:34am:
MSK is CPFSK of modulation_index=0.5 constant. Study basic modulation theory. http://en.wikipedia.org/wiki/Continuous-phase_frequency-shift_keying#Continuous-phase_frequency-shift_keying The following is MSK signal. http://www.designers-guide.org/Forum/YaBB.pl?num=1195226387 If you would like to vary modulation index, there is an another option of using "ahdlLib/vco", although you can generate any RF modulated signal by using QAM(I/Q Modulator). See http://edocs.soco.agilent.com/display/ads2009/MSK+Mod |
The Designer's Guide Community Forum » Powered by YaBB 2.2.2! YaBB © 2000-2008. All Rights Reserved. |