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1. (WO1988003333) SYSTEME D'ANTENNES A RESEAU PILOTE EN PHASE
Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

CLAIMS

1. An antenna system comprising a phased array of antenna elements providing beam steering responsive to the source direction of a received signal comprising a signal band and a pilot signal, the system comprising, in respect of each antenna element, a phase-locked loop arranged to provide a phase-controlled signal of phase locked to said pilot signal for differencing with the received signal to provide a phase compensated output signal of relatively low frequency, said phase-controlled signal being responsive to a phase comparison of a frequency offset version of said output signal and a local oscillator signal common to all of the phase-locked loops, the arrangement being such that the output signals are of the same phase such as to produce a maximum value on summation irrespective of the direction of the source of the received signal.
2. An antenna system comprising a phased array of antenna elements providing beam steering in response to a received signal comprising a signal band and a pilot signal, the system comprising a signal path from each element of the array to common summing means, each said path including first frequency changing means which forms part of a respective phase-locked loop, the phase-locked loop
comprising, in sequence, the first frequency changing means, further frequency changing means, a band-pass filter, a phase-comparator arranged to compare the phase of the filter output with the phase of a local oscillator signal common to all of said phase-locked loops, an integrator responsive to the output of the phase-comparator to control a voltage-controlled-oscillator which is adapted to provide a
differencing signal to said first frequency changing means, the arrangement being such that in operation the voltage-controlled oscillator signal is locked in phase to the pilot signal and the output signal from said first frequency changing means is offset in frequency from the difference between the signal band frequency and the pilot frequency.
3. An antenna system according to Claim 1 or Claim 2, wherein the pilot frequency lies within the said signal band.

4. An antenna system according to Claim 1 or Claim 3 as appendent to Claim 1, wherein said phase-controlled signal is mixed with a relatively high frequency local oscillator signal common to all of said phase-locked loops to provide a transmit signal which tracks the source of said received signal.
5. An antenna system substantially as hereinbefore described with reference to the accompanying drawings.