Re: AM radio receiver - design



miso@xxxxxxxxx wrote:

On Feb 9, 8:24 am, cs_post...@xxxxxxxxxxx wrote:

For a receiver, if you really want something economical that can pick
out exactly the bandwidth of interest and reject everything else, try
looking at a quadrature sampling detector,

In the early 80s, we did a modem using a similar scheme, but at that
point it could be done in DSP. The easiest way to derive IQ signals
via sampling is by decimation and alternate sample inversion.

Assume this is your sample stream
1 2 3 4 5 6 7 8 9 10
Produce two streams as such
+1 -3 +5 -7 +9
+2 -4 +6 -8 +10

This assumes sampling at 4x. You could need to do clock recovery of
the carrier with a multiplier.

Direct downconversion -> the receiver is hit by the 2nd order IM products -> poor dynamic range.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
.

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