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Re: [IRCA] phasing units, then and now
- Subject: Re: [IRCA] phasing units, then and now
- From: Andrew Ikin <andrew.ikin@xxxxxxxxxxxxx>
- Date: Mon, 9 Jul 2018 21:22:07 +0000
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- Thread-topic: [IRCA] phasing units, then and now
Hello Guy,
You have raised an interesting question ref. using dual channel SDR for
phasing. These may in future afford an alternative to some expensive
commercial phasers. Also the SDR has the option of offering a fixed phase
over a very wide bandwidth. This could be useful for phasing two orthogonal
loops to provide omni-direction or with a loop + a resistance loaded
longwire for a wideband cardioid pattern.
However, like most other phasing schemes the SDR cannot provide a null over
a wide bandwidth when used say with similar antenna pairs. This can only be
done with a special Phased array controller when the two endfire antennas
are run in anti-phase with a delay-line. This phasing also requires a design
that has zero interaction on the antenna inputs verses phasing/amplitude
adjustments.
One interesting phaser that may have been overlooked was designed by the
Late Graham Maynard in the late 1980s. He used a variable delayline to
provide a 90 degree phase shift with a fixed 180 degree phase reversal
transformer switched in 4 quadrants to provide 0-360 degree phasing. The
advantage of this scheme was a wider null bandwidth as it could be used for
an endfire array too.
73
Andrew Ikin
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