[ICOM] Sherwood Engineering and DSP

[Adam Farson]

Hi Tom,

The high-end commercial and military DSP-based radios tend to use a
considerably higher final IF. One Rockwell-Collins design used an ADC
sampling at 456 kHz, followed by a decimation process with a 24 kHz output
which fed the DSP. Nowadays, the DSP will run at a higher speed; the end
result will be that all DSP processes will work more effectively.

The ultimate goal (already achieved by several manufacturers) is direct
sampling, where he ADC samples a part of the actual HF frequency range.

Further reading: Sabin et al., "HF Radio Systems & Circuits", Chapter 8.
(This is the Rockwell-Collins HF textbook.)

Many of the current DSP amateur transceivers are getting quite close, but
noise and artefacts generated in the ADC and DAC will become less
significant with each new generation of these devices.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: icom-bounces at mailman.qth.net [mailto:icom-bounces at mailman.qth.net] On
Behalf Of Tom Norris
Sent: Thursday, June 07, 2007 14:54
To: ICOM Reflector
Subject: Re: [ICOM] Sherwood Engineering and DSP

Adam, how do "the new" ham DSP radios stack up to the commercial units that
have been around for much longer?  Other than cost, sampling speed and maybe
processor bus width differences...

Tom NU4G




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