Re: NEC-LIST: Adaptive Antennas and Mutual Coupling

At 11:40 97-11-08 -0500, Jeffrey Fordham wrote:

>Phase pattern measurements are as easy to collect as are power
>patterns. (If you have a phase and amplitude receiver of course)

My own 2 bits from personal experience:

I assume that your antennas are a few feet large, which not very
practical for an indoors range. (Far field criterions, size, etc.)

If you do outdoors measurements, you will find out that you will be
mostly measuring wind speed rather than phase, unless all the transmit
and receive tower elements are *very* rigid. At 1.9GHz, (this is for
PCS, isn't it?) lambda~16cm, and the sum of the TX and RX antenna
deflections mush stay within a small fraction of that for the duration
of the measurement at all measurement angles... A 2mm swing would
result in 4 degrees of error.

As to the equipment, a garden variety network analyzer (8753, 8720,
8510) works fine for the measurement of the phase pattern, although it
may not be as fast as a special purpose machine, or resilient to
outside interference. Ideally, you would directly use the R, A and B
ports of the machine with perhaps a bandpass filter, a small PA and a
preamp. IF bandwidth is to be reduced, and sweep set to synthesized
steps. Commercial systems include rotor control, but measuring
frequency responses while rotating the antenna by hand doesn't take
too much time.

For the stability requirement, your best bet would be to use mount the
antennas directly on separate buildings on the campus, sufficiently
high to be able to neglect ground reflections. Avoid flimsy "TV"
towers. There remains, of course, the small issue of passing a phase
reference signal from on building to the other...

Alexandre

Montreal
Received on Mon Nov 17 1997 - 09:45:50 EST