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receiver dynamicrange - input signal estimation (Read 1921 times)

paddu

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receiver dynamicrange - input signal estimation
Nov 27^th, 2011, 12:47am

Hi,
Most of wireless receivers dynamic range varies from 60 - 90 dBm. Dynamic range is entireley controlled by programming the individiual gains of LNA, Mixer and VGA's.
My question is how to detect the input signal strength in order to have programmable gain settings so that ADC has the required dynamic range.
How the receiver identifies the input signal strength (across the dynamic range) to set the rx chain gain automatically so that ADC receives the required signal?

Thanks.

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aaron_do

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Re: receiver dynamicrange - input signal estimation
Reply #1 - Nov 28^th, 2011, 5:16pm

Hi,

try reading up on RSSI (Received Signal Strength Indication). For example, go to IEEExplore and search "CMOS RSSI".

regards,
Aaron

EDIT: I'm not sure exactly how its done, but I guess they can use the ADC saturation as a reference for the gain setting in a feedback loop. The gain setting itself is taken into account when calculating the signal strength. Maybe somebody else can give more details. Also check this link:

http://www.designers-guide.org/Forum/YaBB.pl?num=1242377069

there is no energy in matter other than that received from the environment - Nikola Tesla

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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: receiver dynamicrange - input signal estimation Reply #2 - Nov 29^th, 2011, 3:48pm also research the topic of "log amps" or "logarithmic amplifiers" which get used in RSSI systems.
Back to top	Jerry Twomey www.effectiveelectrons.com Read My Electronic Design Column Here Contract IC-PCB-System Design - Analog, Mixed Signal, RF & Medical IP Logged

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