On Friday 29 September 2006 07:30, Jason Hecker wrote: > > lot more about it, and looking for better parts, but I've learned to ask > > the experts early ;) Any ideas? > > I used to write software for a radar. It used separate antennas for
I still do :) > transmit and receive for several reasons though the RX and TX antennas were > located right next to each other. This arrangement works very well. If > you are concerned about too much power entering the RX stage you could use > a switchable attenuator using a voltage signal and PIN diode. Actually, if 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... > you want any sensible readings and a signal that has good dynamic range at > the ADC you will need a controllable attenuator that increases the RX gain > over time (in a logarithmic way) as the return signal gets weaker with the > squared square of the distance (R^4 !). You'll always get overload signal > for a certain close-in range anyway. Not much you can do about that. For boundary layer/troposphere radars we halve our effective PRF and transmit a short low power pulse and listen with a low gain setting on even pulses and a high power long pulse with high gain on odd pulses. The sampling configuration also alternates to sample low and high. I guess the other possibility is being adaptive, ie adjust your power/gain based on what you can currently see. -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C
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