At 07:46 PM 8/20/2005, Frank Brickle wrote:
Jim Lux wrote:
> At 01:04 PM 8/20/2005, Ken N9VV wrote:
>>o Flex tutorial on how it is that a Pentium IV has
>>enough horsepower to perform all the DSP arithmetic when
>>an Orion from Ten-Tec has two very fast dedicated DSP
>>chips and the IC-7800 has four.
>
> The Orion is really two receivers in one box. While the SHARC is a fast
> floating point DSP (and actually available in a radiation tolerant version
> if you care), what speed does it run at?
Remember that the SDR1K DSP is essentially an audio application. It runs
at audio bandwidths. Strictly in terms of number crunching, it's not all
that much more heavyweight, maybe a factor of 4 to 8, than a typical
soundcard digital program. All the RF stuff is done by the hardware.
On the other hand, the Orion and 7800 DSPs run at IF, don't they? That's
a lot more samples per second. A Pentium or PowerPC would be quite
adequate for that job, but they wouldn't have headroom for much else,
they need more glue, and they're wattage pigs.
Not according to the description I read... 20kHz LPF in front of the A/D
for the Orion.
And, on a Watts/MIPS basis, most DSPs blow away the generalized processors
like the Pentium, when comparing reasonably like technology generations (no
fair comparing 1990 vintage against 2000 vintage, for example).
The SDR1K represents a very sensible division of labor between hardware
and software, given the current state of general-purpose hardware at
this point in time.
precisely that...
The Orion is a standalone box, and was designed as such. The SDR1K is
designed to use a (>$1K) PC as an integral part. In a apples to apples
comparison, you'd really need to use 2 SDR1Ks, one with the 100W amp, plus
at least one PC, and at least one high end sound interface, plus various
and sundry software. I'll bet by the time you combine all the stuff you
need, you're pretty close to the nominal $3K-$4K of the Orion and it's ilk.
The real advantage of the SDR1K is that the architecture is very "open".
James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875
