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Design >> RF Design >> 3 dB SNR lose when use 1-bit quantizer?
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Message started by liu6747 on Aug 14^th, 2007, 2:28pm

Title: 3 dB SNR lose when use 1-bit quantizer?
Post by liu6747 on Aug 14^th, 2007, 2:28pm

Hi, All

I am reading Thomas Lee's RF book. On section 19.6.1 (2nd ed, page718), he talked about GPS receiver architecture, which is RF to Low IF (IQ). The themal noise is about ~ 20 dBc higher than GPS signal at RF input, but GPS siganl has 43 dB process gain. The last stage is two 1-bit quantizers, and note 18 says:

Use fo a 1-bit quantizar costs 3 dB, relative to an infinitely fine quantizar. The most commonly used 2-bit quantizar, combined with appropriate AGC to maximize use of the available quantization levels, reduce the loss to about 0.7dB....

I assume the loss is about SNR, but should it be 6dB? because SNR_ADC=1.76+6N?

Please let me know where I am wrong and let me know how to calculate 3 dB on 1-bit adc

thanks

liu

Title: Re: 3 dB SNR lose when use 1-bit quantizer?
Post by carlgrace on Aug 15^th, 2007, 10:31am

Lee was talking about power, not voltage. So the 3dB power and the 6dB voltage are the same thing.

Carl