Radar systems and methods
A mode S Interrogation Side Lobe Suppression System (ISLS) for an electronically scanned interrogator is described. One aspect introduces the 90° phase offset between the main and control beams thereby enabling the full power capability of the TRU to be effectively utilized and the effective beamwidth in Mode S to be sharply defined. The system allows the transmission of the simultaneous ISLS pulse of a Mode S all-call interrogation to be transmitted using the same array as is used by the main beam.
1. An electronically-scanned SSR interrogator, adapted to be capable of Mode S All-Calls with simultaneous ISLS pulse, the interrogator comprising:
a plurality of transmit modules, each transmit module including a chain of linear amplifiers permitting linear superposition of a main beam pulse and a control beam pulse, and wherein the interrogator is configured to steer the superpositioned main beam pulse and control beam pulse by applying a progressive phase taper across the plurality of transmit modules.
2. An electronically-scanned SSR interrogator according to claim 1 , in which the linear amplifier chain comprises:
class AB amplifiers.
3. A radar system, comprising:
the electronically scanned SSR interrogator in accordance with claim 1 .
4. An air traffic control system, comprising:
the electronically scanned SSR interrogator in accordance with claim 1 .
5. An electronically-scanned SSR interrogator according to claim 1 , in which the main beam pulse and the control beam pulse are combined in quadrature.
6. An electronically-scanned SSR interrogator according to claim 1 , comprising:
a splitter configured to:
receive a main beam signal and a control beam signal;
split the main beam signal main beam signals
split the control beam signal control beam signals; and
input one of the split main beam signals and one of the split control beam signal s into each of the plurality of transmit modules; and
a phase shifter configured to shift a phase of at least one of the control beam signals input to each of the plurality of transmit modules such that the main beam pulse is transmitted as a sum beam and the control beam pulse is transmitted as a difference pattern.