There is no reason to; the "pulsing" circuit part isn't placed in the front-end. The PWM generated by the DSP is immediately integrated to a cc voltage, the clean analog gain control signal, near the I/O pin of the processor.
If you consider what kind of pulsing signals are generated by the ADC (at e.g. 130Msps) and the following digital components processing a flood of quad burst signals (the sampled data) you will understand that the low freq. PWM pulses used for the AGC will disappear in this scenario. AGC signal calculation is software implemented, and performed through the analysis (by the DSP) of the samples coming from the ADC. This permits to evaluate and calculate the AGC from the entire broad band of what is presented to the ADC inputs. The problem you underlined rising from the RF ADC input monitoring scheme is so bypassed. As I've stated before, software calculation of the AGC permits to have more powerful performances compared to traditional analog schemes due to the possibility to adopt adaptative, dynamic algorithms and automatic evaluation of the conditions of what has to be received, what is disturbing (unwanted signals), QSB, QRN etc. etc.. This algorithms can shape the AGC control signal adapting it automatically to the kind of signal you try to receive (and respecting the ADCs max ratings for the best performance). This is a new powerful kind of AGC, aligned to the requirements of a modern SDR. vy 73s de ik2wqi - Andreas FRANCIS CARCIA wrote: > I don't like anything pulsing in a RX front end to raise noise. maybe an > analog AGC would be simple. just monitor the A/D input and reduce the gain > when needed. The problem is the broad band input driving the agc monitor. > ------------------------ Yahoo! Groups Sponsor --------------------~--> Yahoo! Groups gets a make over. See the new email design. http://us.click.yahoo.com/XISQkA/lOaOAA/yQLSAA/ELTolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
