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Re: [Discuss-gnuradio] Active Radar Hardware
From: |
Lee Patton |
Subject: |
Re: [Discuss-gnuradio] Active Radar Hardware |
Date: |
Fri, 29 Sep 2006 10:03:19 -0400 |
Jason and Daniel -
Thanks for the feedback. I'll look into PIN diodes. The reason I
wanted to use a circulator was because it doesn't require a switching
signal to be generated from the USRP. And, while generating such a
signal is possible, it is difficult (if not impossible?) to ensure it is
timed properly with the transmit waveform -- unless I do some FPGA
coding, which may be the necessary next step. (Again, something with
which I have no experience! But learning new things is fun, right?) I
think I will look into using the actual Tx waveform as the switching
signal.
Also, Jason, thanks for pointing the need for a variable attenuator to
condition the signal for ADC. Although I've been aware of this in the
past, I forgot about it in my application.
Thanks again fellas,
-Lee
On Fri, 2006-09-29 at 18:15 +1000, Jason Hecker wrote:
> > We make MF & VHF systems and for some of our VHF systems we use a single
> > set of antennas and a T/R switch (passive and active). However since our
> > frequency of operation is 2-3 orders of magnitude lower it's probably all
> > different...
>
> The radar I worked on was a ~2.7GHz job. Since the receiver was spammed for
> the first several hundred metres in range due to large amounts of echo from
> ground clutter any such early returns were gated out. After that the circuit
> controlling the attenuator (PIN diodes) ramped the voltage so that the
> overall gain of the system increased in time. This was to maximise or
> normalise the S/N ratio at the ADC. When you are looking for metallic
> bogie's many 10's of KM away you need all the return you can get even with
> the gain achieved from integrating multiple returns.
>
> Anyway, the author of the grandfather post doesn't sound like he has too much
> RF experience (who does?) Perhaps a circulator will do or even better, an
> RX/TX switch module (diplexers?) - though this might involve a hardware hack
> to get the switching pulse out in time. The thought did occur to me to get
> something like a Furuno boating radar head with an integrated separate
> transmit and receive antenna. You'd get a nice narrow beam from one of
> those.
>
>
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