🚀 go-pugleaf

Before I get started, let me state that my interest in this discussion is
purely in generic radar jamming techniques such as those used in military
applications and not in defeating police radar...

In <1993Jan26.124059.5230@wkuvx1.bitnet> scottcr@wkuvx1.bitnet writes:

>O.K. how are we gonna do this?  A linear transponder with (30 hz /mph
>upconverter?);  Problems with in/out isolation.

A straight repeater would probably suffice, unless the radar has leading
edge tracking.  Depending on the radar, a "passive" electro-mechanical 
method can be viable.

> Maybe since we really
>don't need a truckload of transmit signal (the radar unit is seeing
>1 / (it's signal * 4PI * dist to car^2 * refl coef * dist back^2)
>so if we retransmit say +10 dBm into a horn with 10 db gain that
>should cover it.

In general, the ratio of jammer signal power to radar return signal
power varies as the inverse square of the range to the radar.  Thus, the
power requirements must take into account the ranges over which the
jammer needs to operate, as well as the other factors you mention.

>A balanced modulator would have to be used for mixing as the signals
>would be too close in frequency to filter; but the image being present
>may give us trouble too (does the radar care if it's "coming or going?".
>I am going to guess that
>two horns facing forward spaced say two feet apart are going to have
>about 40+ dB isolation, so this limits the throughput gain (again since
>the freqs are too tight to filter),  What about polarization?

For a narrow-band system (where the frequencies of interest are concentrated
in a very narrow band), isolation problems can sometimes be solved by "tuning"
the antenna installation.  In fact, an RF circulator used with a single
antenna would probably provide ample isolation.

As far as polarization, it depends on what you had in mind.  One idea
is to use a single, dual polarized antenna in place of two antennas; 
unfortunately, I believe that the port-to-port isolation is less than
40 dB.  Another issue is polarization jamming.  That is an involved
subject in it's own right.
-- 
POMPONIO,NICHOLAS A
Georgia Institute of Technology, Atlanta Georgia, 30332
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