Phased Array using a Passive Element Beamformer

This is not easy as has been amply discussed in sources like the ARRL Antenna Book. The schemes described there rely on fairly simple arrangements of antennas, and further, rely on the quarter wave transmission line current forcing properties. The Antenna Book does mention the broadcast approach in passing, that is, using separate LC networks on each element, then separate phase shift networks , and finally suitable power dividers, and then goes on to say that it is too complex, and that setting the array up for various directions is too difficult. Here is the basic idea:

Why is the broadcast approach so difficult?

So, the Antenna Book, and other ham literature, has concentrated on solutions using limited flexibility: limited numbers of elements, restricted numbers of phases to drive the elements. Arrangements like the 4 square with 90 degree phase shifts are popular because with a half dozen relays and one LC network you can make it work, and it gives you a reasonably good null in the back.

A couple of developments in the past few years has changed the situation.

All of a sudden, you can have a single knob to steer the array, with the computer taking all the work out of setting up all those L's and C's.

The key components are



passive1.htm - Revised 16 June 1999, Jim Lux
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