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Old July 4th 06, 01:44 PM posted to rec.radio.amateur.homebrew
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Posts: 44
Default quadrature detector & SSB


It's not that easy Ben.....

The I-Q demodulator in this chip doesn't include the required 90 deg audio
phase shift network. That's usually one of the toughest parts of any
phasing-type detector. Also, the LO phase balance is specified as 1.2 deg
and the amplitude balance is specified as 0.2 dB. These imbalances would
combine to give an opposite sidenabd rejection of less than 40 dB, maybe 35
dB. Not too good by modern standards.

Furthermore, the detector circuits only work at IF frequencies, not RF
frequencies. This implies that the internal mixer would have to be used in a
downconversion mode, resulting in a requirement for an image-reject bandpass
filter at the mixer input and some measure of bandpass filtering at the
mixer output.

On top of all this, the LO noise floor is only -100 dBc/Hz, which would
probably cause pretty bad reciprocal mixing under crowded band conditions.

All things considered, I think that by the time one made this chip do what
it has to do for SSB/AM, one would be better off starting from scratch with
more conventional components.

Joe
W3JDR


"Ben Jackson" wrote in message
...
On 2006-07-04, MAc wrote:
How to use quadrature detector to demodulate cw and ssb. I want to use
AD607 in simple project. There is Quadrature detector on "the end" with
two outputs I&Q - and internal phase shifter. How to detest SSB simplest
way?


If it does all that, you just have to choose USB, LSB or AM by chosing
sum, difference or magnitude of the IQ output.

--
Ben Jackson

http://www.ben.com/



 
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