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[Discuss-gnuradio] Frontend to build a Spectrum Analyzer
From: |
Stefan Mangard |
Subject: |
[Discuss-gnuradio] Frontend to build a Spectrum Analyzer |
Date: |
Wed, 08 Oct 2003 13:31:05 +0200 |
User-agent: |
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.3) Gecko/20030312 |
Hi everybody,
I am a student working a university. My background is mainly in computer
science and VLSI design - unfortunately, I am not an expert in building
RF frontends yet.
However, I would like to achive the following goal and I think my task
has a lot in common with GNU radio.
We have a quite nice PCI oscilloscope at our university that I can use.
It has a resolution of 8 bit and a sampling rate of up to 1GHz.
I would like to build an RF fronted for this oscilloscope that allows me
to use the oscilloscope as spectrum analyzer and as a tuner to receive
short signals (I don't have a real-time decoding constraint - for my
application, I just need to be able to receive a signal in a given
frequency band for a few milliseconds - i.e. until the memory of the
oscilloscope is full). Because of the limited resolution of the
osciloscope I need to do filtering in the analog world.
So, supposedly I need an architecture like this:
antenna - amplifier - mixer - Bandpass - amplifier - oscilloscope
|
|
Oscillator
It should be possible to control the oscillator via the PC.
Additionally, the Bandpass should be switchable between different
bandwiths (at least there should be a mode for a few kHz and one for a
few MHz).
I think the scenario is pretty much the same as in a software radio,
where you want to receive all kinds of transmissions in all the
different frequency bands.
In my application I would like to be able to detect signals up to 1GHz.
I am not experienced in doing RF designs and so I am looking for some
hints concerning to following questions:
- Can I buy suitable RF Frontends somewhere and just plug it between the
Antenna and the Oscilloscope?
- Are there components in the HAM radio world I could use?
- How do you generate the signal for the mixing in GNU Radio? As far as
I know VCOs are only available for a limited frequency range?
- How do you do the bandpass filtering in GNU radio? I suppose you also
need an analog filter, because of the limited resolution of the A/D
converter.
Thanks for any hints,
Stefan
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