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