RadioBanter - 30 Years Ago: New cheap 200 kHz ADC: good for digital receiver?

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This is from a web-site that is replaying Usenet, and rec.ham-radio,
from 30 years ago (currently early fall 1989). The site is:

http://www.olduse.net

If you prefer to use your own newsreader, the site also supports an NNTP
connection at:

nntp.olduse.net:119

From rec.ham-radio Sat Sep 28 10:12:30 2019
Xref: utzoo rec.ham-radio:13337 sci.electronics:7834
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wuarch ive!cs.utexas.edu!uunet!zephyr.ens.tek.com!tektron ix!sequent!mntgfx!mbutts
From: (Mike Butts)
Newsgroups: rec.ham-radio,sci.electronics
Subject: New cheap 200 kHz ADC: good for digital receiver?
Message-ID:
Date: 19 Sep 89 17:12:59 GMT
Organization: engr
Lines: 28

The current Electronic Design (9/14/89) has a piece on the new Burr-Brown
PCM1705P, a monolithic dual analog-to-digital converter. It runs at 200 kHz,
gives 14-bit accuracy and 18-bit resolution, and costs $27 in 1K quantity (I'd
guess $50 in onesies). It's designed for high-end home audio, DAT and effects
and such, but the article is mostly about how you can hook it to a DSP & use
it for medical, telecommunications, spectrum analysis, imaging, etc.

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?

Imagine how fast, cheap ADCs and DSPs could cause a revolution in receiver
design (especially when we get cheap ADCs and DSPs that can handle several
MHz IFs, and direct digital synth chips to match):

Antenna --- Mixer --- LPF/gain -- ADC ----- DSP ----- DAC ----- audio
^ |
| |
DDSynth \------ data

A few real RF stages + cheap digital VLSI = high-performance receiver?
- --
Michael Butts, Research Engineer KC7IT 503-626-1302
Mentor Graphics Corp., 8500 SW Creekside Place, Beaverton, OR 97005
!{sequent,tessi,apollo}!mntgfx!mbutts
Opinions are my own, not necessarily those of Mentor Graphics Corp.

From rec.ham-radio Sat Sep 28 10:12:34 2019
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From: (Mike Butts)
Newsgroups: rec.ham-radio,sci.electronics
Subject: New cheap 200 kHz ADC: good for digital receiver?
Message-ID:
Date: 19 Sep 89 17:25:21 GMT
References:
Organization: engr
Lines: 26

- - From article , by (Mike Butts):
Imagine how fast, cheap ADCs and DSPs could cause a revolution in receiver
design (especially when we get cheap ADCs and DSPs that can handle several
MHz IFs, and direct digital synth chips to match):

Antenna --- Mixer --- LPF/gain -- ADC ----- DSP ----- DAC ----- audio
^ |
| |
DDSynth \------ data

A few real RF stages + cheap digital VLSI = high-performance receiver?

If one takes this one step further, to a time of 80 MHz wide dynamic range ADC
chips (2000? 2010?):

Antenna --- LPF/gain -- ADC ----- DSP ----- DAC ----- audio
|
|
\------ data

To heck with superhet, just digitize the HF band and process from there!
- --
Michael Butts, Research Engineer KC7IT 503-626-1302
Mentor Graphics Corp., 8500 SW Creekside Place, Beaverton, OR 97005
!{sequent,tessi,apollo}!mntgfx!mbutts
Opinions are my own, not necessarily those of Mentor Graphics Corp.

From rec.ham-radio Sat Sep 28 10:12:36 2019
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From: karn@jupiter (Phil R. Karn)
Newsgroups: rec.ham-radio,sci.electronics
Subject: New cheap 200 kHz ADC: good for digital receiver?
Message-ID:
Date: 21 Sep 89 01:29:13 GMT
References:
Sender:
Reply-To: (Phil R. Karn)
Organization: Bell Communications Research, Inc
Lines: 12

Antenna --- Mixer --- LPF/gain -- ADC ----- DSP ----- DAC ----- audio
^ |
| |
DDSynth \------ data

A few real RF stages + cheap digital VLSI = high-performance receiver?

Actually, you'll want two mixers, low pass filters and A/D converters.
The mixers should operate in quadrature so you can do things like SSB
filtering in DSP software.

Phil

From rec.ham-radio Sat Sep 28 10:12:38 2019
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From: (John Moore)
Newsgroups: rec.ham-radio,sci.electronics
Subject: New cheap 200 kHz ADC: good for digital receiver?
Message-ID:
Date: 21 Sep 89 13:51:54 GMT
References:
Reply-To: (John Moore)
Followup-To: rec.ham-radio
Organization: Anasazi Inc, Phoenix AZ
Lines: 20

In article (Phil R. Karn) writes:
] Antenna --- Mixer --- LPF/gain -- ADC ----- DSP ----- DAC ----- audio
] ^ |
] | |
] DDSynth \------ data
]
]A few real RF stages + cheap digital VLSI = high-performance receiver?
]
]Actually, you'll want two mixers, low pass filters and A/D converters.
]The mixers should operate in quadrature so you can do things like SSB
]filtering in DSP software.

I don't think so. You should be able to do that in the DSP with a single
ADC. After all, the signal into the ADC is identical to that off the
antenna except that it has a lower carrier frequency.
- --
John Moore (NJ7E) mcdphx!anasaz!john asuvax!anasaz!john
(602) 861-7607 (day or eve) long palladium, short petroleum
7525 Clearwater Pkwy, Scottsdale, AZ 85253
The 2nd amendment is about military weapons, NOT JUST hunting weapons!

From rec.ham-radio Sat Sep 28 10:12:41 2019
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From: (Paul Elliott x225)
Newsgroups: rec.ham-radio,sci.electronics
Subject: New cheap 200 kHz ADC: good for digital receiver?
Summary: Digital Radio / DSP commnt
Message-ID:
Date: 22 Sep 89 17:38:10 GMT
References:
Organization: Optilink Corporation, Petaluma, CA
Lines: 32

In article , karn@jupiter (Phil R. Karn) writes:
Antenna --- Mixer --- LPF/gain -- ADC ----- DSP ----- DAC ----- audio
^ |
| |
DDSynth \------ data

A few real RF stages + cheap digital VLSI = high-performance receiver?

Actually, you'll want two mixers, low pass filters and A/D converters.
The mixers should operate in quadrature so you can do things like SSB
filtering in DSP software.

Phil

Correct me if I'm mistaken, but we can still do the SSB phasing demodulation
in software with the receiver as shown in the diagram (assuming blazingly fast
processing hardware). The only function of the mixer is to shift the input
signal frequency down to a more comfortable range for the A-D and DSP.

Of course, if you had REALLY fast hardware and software, you could dispense
with the mixer and local oscillator altogether... I vaguely remember a
conversation I had with the designer of some sort of (fairly low frequency?)
(aeronautical navigation?) receiver, where they did essentially this in an
ASIC. It doesn't seem entirely practical to me now, so I'm probably forgetting
something critical. I'll post again if I can come up with the details.

- --
Paul M. Elliott Optilink Corporation (707) 795-9444
{pyramid,pixar,tekbspa}!optilink!elliott
"I used to think I was indecisive, but now I'm not so sure."

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