Circuit including a phase shifter for generating signals for electronically scanned antennas

DETAILED DESCRIPTION It is an object of the present invention to provide a circuit capable of generating RF signals with a characteristic necessary for electronically scanned antennas which overcomes the drawbacks of the prior art and, more specifically, is simpler than the prior art and introduces less errors.
This object is reached through a circuit for generating RF signals for an electronically scanned antenna, and in particular is to be applied to a TACAN system antenna, and by use of a phase shifter specifically suitable for such a circuit.
The present invention provides a small Butler-matrix to combine a limited number of outputs of a power divider and further combines the remaining outputs of the power divider, suitably phase-shifted, and combines the few outputs of the Butler-matrix through the use of electromagnetic combiners.
A plurality of RF signals suitable for electronically scanned antennas is obtained which have very good precision and require relatively simple circuitry.
An improvement in the SWR is obtained by using in the present invention, phase shifters that are compensated through use of lambda/4 stubs instead of using conventional differential phase shifters that are frequency-compensated through electromagnetic coupling (Schiffman phase shifters), as will become clearer hereinafter.
The phase shifter in the present invention has a very stable shift constancy within an elevated band centered on the operating frequency of the phase shifter.