Re: AGC and Dynamic Range of ADC

GNU Radio
1

On 09/23/2013 11:07 PM, bob wole wrote:

Can somebody please guide me on this ?

Bob

On Fri, Sep 20, 2013 at 4:44 PM, bob wole address@hidden wrote:

I have USRPN210 with WBX and RFX2400. Is there any AGC chip on N210
motherboard or WBX, RFX2400 before ADC to utilize the dynamic range of ADC
? if yes, which one? If not, then won’t the varying input signal (for
example signal from moving object) to ADC affect the performance of ADC ?

Bob

The ADC on an N210 has over 80dB of dynamic range. If that >>isn’t
enough, then your application can adjust the RF gain to taste.

Only a subset of applications actually benefit from the usual >>hardware
AGC schemes, and such schemes are invariably >>application-specific, so
there’s
no automatic gain control. But your application can >>dynamically
make gain adjustments as it goes.

Hi Marcus thanks for response, If there is no automatic gain control
then
how does it is ensured that ADC doesn’t saturate ? I mean what if there
is
a signal whose amplitude is greater that ADC’s highest input level ?
Won’t
it saturate the ADC ? Also what if the signal is too weak to span much
of
the ADC input voltage, then again we are not using all bits effectively.
Guide please.

Thanks,

Bob

2

On 09/24/2013 10:30 AM, bob wole wrote:

N210 motherboard or WBX, RFX2400 before ADC to utilize the

Only a subset of applications actually benefit from the usual
weak to span much of the ADC input voltage, then again we are not
http://www.sbrac.org http://www.sbrac.org/

There is nothing to ensure that ADC values are neither “too little” nor
“too big”. That’s up to your application. There’s an RF gain control
on the
WBX, for example, that gives 31.5dB of gain control. If you have
very weak signals, then you have to use an external LNA. If your
dynamic
range requirements exceed the 80dB dynamic range of the ADC, then
your application has to account for this, and adjust RF gain
accordingly.