[time-nuts] Slightly OT: inexpensiveUSB analog-digitalconverter?
dlharmon at dlharmon.com
Thu Jan 17 23:11:05 EST 2008
The FPGA does contain the complete digital downconverter and upconverter
(actually 2-4 downconverters are planned). Input to the FPGA is the 16
bit 125 MHz real data from the ADC and the output is 24 bit 500 kHz
complex data. The DSP does nothing but move data at the moment. FFTs and
future demodulation is done on a PC. The lack of floating point in the
Blackfin makes it impractical for high dynamic range FFTs. It requires a
fairly high end laptop to run it due to doing all of the DSP on the PC side.
There is also a DC - 1.8 GHz transceiver front end that is currently
functional except for a few minor issues The phase noise of the front
end is not very good (-90 dBc/Hz @ 10k) due to the YTO and 2nd LO VCO.
I have found that the IF board alone is very useful as it covers 100 kHz
to 40 MHz (transformer coupled). The front end has a bypass relay which
will allow direct use of the ADC and DAC.
The current IF board is working quite nicely. It only had to have 1
jumper wire and 2 pullup resistor added. I plan to do another revision
of the IF board (ADC, DAC, FPGA, DSP, USB) to add a few features and fix
a few minor bugs. I will build 3 for my own use and do not plan to build
any more. I don't really want to deal with any more 0402 parts than I
have to. Gerbers will be posted on my website, but I doubt anyone other
than me would want to build one. It is a very expensive board with lots
of tiny components. The ADC alone is $130.
In addition to spectrum analyzer software, I plan on doing vector
network analyzer software, software defined radio software and
oscillator characterization software. I expect to be posting more
questions here as I get to the oscillator characterization part.
Darrell Harmon - KI4MVK
Ulrich Bangert wrote:
> both the DSP as the FPGA are real workhorses. I am eager to hear which
> is used for what.
> 73 de Ulrich, DF6JB
>> -----Ursprungliche Nachricht-----
>> Von: time-nuts-bounces at febo.com
>> [mailto:time-nuts-bounces at febo.com] Im Auftrag von John Miles
>> Gesendet: Donnerstag, 17. Januar 2008 08:22
>> An: Discussion of precise time and frequency measurement
>> Betreff: Re: [time-nuts] Slightly OT: inexpensiveUSB
>> Seconded; this sounds like a great exercise.
>> So, I guess it's not reasonable to implement the entire
>> digital downconverter on the Spartan-3E FPGA?
>> -- john, KE5FX
>>> -----Original Message-----
>>> From: time-nuts-bounces at febo.com
>> [mailto:time-nuts-bounces at febo.com]On
>>> Behalf Of Ulrich
>>> Sent: Wednesday, January 16, 2008 11:18 PM
>>> To: 'Discussion of precise time and frequency measurement'
>>> Subject: Re: [time-nuts] Slightly OT: inexpensiveUSB
>>> I just found your homepage
>>> WOW! What a project!
>>> 73 de Ulrich, DF6JB
>>>> -----Ursprungliche Nachricht-----
>>>> Von: time-nuts-bounces at febo.com
>> [mailto:time-nuts-bounces at febo.com]
>>>> Im Auftrag von Darrell Harmon
>>>> Gesendet: Donnerstag, 17. Januar 2008 05:11
>>>> An: Discussion of precise time and frequency measurement
>>>> Betreff: Re: [time-nuts] Slightly OT: inexpensiveUSB
>>>> John Miles wrote:
>>>>> Is it just me, or is there a huge hole in the DAQ
>> marketplace for
>>>>> a high-resolution, low-noise, low-to-moderate cost,
>>>>> acquisition dongle?...
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