Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hpl-opus!hpnmdla!hpsad!toma
From: toma@hpsad.HP.COM (Tom Anderson)
Newsgroups: comp.dsp
Subject: Re: New cheap 200 kHz 14-bit dual ADC chip = digital HF receiver?
Message-ID: <9520002@hpsad.HP.COM>
Date: 25 Sep 89 23:20:41 GMT
References: <1989Sep21.162329.2416@mentor.com>
Organization: HP Signal Analysis Division - Rohnert Park, CA
Lines: 28

>I wonder if any DSP radio experts out there can comment on whether this
>chip, with an 80 kHz or so IF front end on the input and a DSP on the
>output might make a practical HF receiver, using the DSP for most of the
>selectivity, gain control, and demodulation?  Is it reasonable to use
>that low an IF?  Could you use both ADCs on the chip to alternatively
>sample a higher IF, like 160 kHz?

Yes, you can make an IF with digital parts.  The HP8560A Spectrum
Analyzer has a digital IF in it.  I can't comment specifically on the
Burr-Brown part.  But if I had two channels, I would sample the IF
signal in quadrature instead of alternately.  This way you get the full
benefit of twice the sample rate of a single converter, and you get to
do some DSP tricks with the quadrature inputs.

Notice that any gain or offset mismatch between the two A/Ds (when
sampling alternately) would look like a signal at half the sample rate.

Don't forget to put a good S/H amp in the system.  Parts designed for the
audio market might have some nasty distortion characteristics when the
input signal is at a high frequency.

A book with some ideas on this subject is "Communication Receivers" by
Ulrich L. Rohde and T. T. N. Bucher.

Tom Anderson           Hewlett-Packard   Signal Analysis Division
toma@hpsad.hp.com      "It's only hardware"

Views expressed are my own and not Hewlett-Packard's