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Abstract

An array antenna (10) that can form and sweep a predicted radiation beam pattern in different directions by using a subharmonic frequency signal from each voltage controlled oscillator (VCO) (20) to control the array phasing. Each VCO (20) generates a radio frequency carrier signal that drives an antenna element (16). A subharmonic signal is generated from a portion of the signal from the VCO (20). The subharmonic signal is mixed with a constant frequency signal to produce an intermediate frequency (IF) signal. The frequency of the IF signal is compared to the frequency of a variable frequency signal in a phase locked loop (PLL) (40). Since the phase of a signal is dependent on its frequency, the variable frequency signal is generated to have a frequency corresponding to a certain phase. The PLL (40) generates an error signal as a function of the difference in frequencies between these two signals. In response to the error signal, the VCO (20) changes the frequency of the carrier output signal. This process is continued by PLL (40) until the frequency of the IF signal is equal to the frequency of the variable frequency signal. The VCO (20) is now generating a signal having a frequency corresponding to the certain phase. The combined resultant relative phase excitation of all the antenna elements generates a maximum field intensity in a predicted direction.

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