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Re: [Discuss-gnuradio] RSSI calculation

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] RSSI calculation
Date: Wed, 30 Mar 2011 10:19:29 -0400
User-agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv: Gecko/20110303 Thunderbird/3.1.9

On 30/03/2011 8:33 AM, Fengyuan Gong wrote:
Shouldn't the second one also read ADC value on the RFX900/1200/1800/2200/2400 and then calculate out the analog signal

That function just does a read of the AUX_ADC (apparently a 10-bit aux_adc on USRP1), it has no notion that it's an RSSI value--it's just an unstructured collection of bits as far as read_aux_adc is concerned.

The "calculate out the analog-signal strength" part is essentially up to whatever upper-layer software is using the resulting aux_adc
  value, and interpreting it as an RSSI.

In the case of the RFX-series boards, the aux_adc input is connected to the *analog* RSSI estimator that's built into the demodulator chip--in this case, the sum of two (I and Q) square-law detectors, maybe with a little bit of gain. So the aux_adc values read are directly proportional received signal strength. It's up to your software to scale appropriately.

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