Re: [IRCA] phasing units, then and now

[Andrew Ikin <andrew.ikin@xxxxxxxxxxxxx>]

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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