mbutts@mentor.com (Mike Butts) (09/20/89)
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 mbutts@pdx.MENTOR.COM
Opinions are my own, not necessarily those of Mentor Graphics Corp.mbutts@mentor.com (Mike Butts) (09/20/89)
From article <1989Sep19.171259.1670@mentor.com>, by mbutts@mentor.com (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 mbutts@pdx.MENTOR.COM Opinions are my own, not necessarily those of Mentor Graphics Corp.
karn@jupiter (Phil R. Karn) (09/21/89)
> 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
john@anasaz.UUCP (John Moore) (09/21/89)
In article <17673@bellcore.bellcore.com> karn@jupiter.bellcore.com (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!elliott@optilink.UUCP (Paul Elliott x225) (09/23/89)
In article <17673@bellcore.bellcore.com>, 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."