Radar system with active array antenna, elevation-responsive PRF control, and beam multiplex control

Claim 1

A radar system, comprising: controllable signal generating means including a pulse control input port, for generating pulses of radio-frequency energy in response to pulse control signals applied to said pulse control input port; controllable antenna array means including (a) a plurality of antenna elements, (b) a like plurality of solid state amplifier means, each of which amplifier means includes an input and an output port, and is associated with one of said antenna elements, and (c) a like plurality of phase shifting means, each of which phase shifting means includes (i) a radio frequency input port coupled to said controllable signal generating means for receiving said pulses of radio-frequency energy therefrom, (ii) a beam direction control input port, and (iii) a radio frequency output port coupled to said input port of one of said amplifier means, for generating at said output port of said phase shifting means pulses of radio-frequency energy phase-shifted by an amount determined by beam direction control signals applied to said beam direction control input port, each of said antenna elements being coupled to said output port of the associated one of said amplifier means by an RF coupling path, said antenna elements being distributed in said array in a fashion which provides a greater density of said antenna elements near the center of said array than near the ends of said array to thereby inherently provide a tapered amplitude distribution when each of said antenna elements receives the same amount of power from its associated amplifier means, said controllable array means being adapted for responding to said pulses of radio-frequency energy of a given power by transmitting a single pencil beam of higher power centered in a direction established by the phase shifts of said phase shifting means in response to said beam direction control signals applied to said beam direction control input ports of said phase shifting means; beam direction control means coupled to said beam direction control input ports of said phase shifting means for, from time to time, generating beam direction control signals, including elevation component control signals, for application to said beam direction control input ports, for determining the beam direction, including the elevation component, of said beam direction; beam multiplex and PRF control means coupled to said controllable signal generating means, to said controllable array antenna means, and to said beam direction control means, for generating said pulse control signals for applying said pulse control signals to said pulse control input port of said signal generating means for controlling the pulse recurrence frequency of said pulses of radio-frequency energy to be responsive to said elevation component of said beam direction control signals, and for causing said signal generating means to produce a single pulse of said radio-frequency energy during the transmit portion of each of recurrent first and second transmit/receive intervals, and for causing said beam direction control means to apply first and second azimuth beam direction control signals to said beam direction control input ports of said phase shifting means during said first and second transmit/receive intervals, respectively, said first and second azimuth beam direction control signals causing said antenna beam to be directed in first and second mutually different azimuth directions, respectively; and receiving means coupled to said antenna array means for responding to returns from targets, said receiving means including pulse separation means for separating returns received during said recurrent first intervals from returns received during said recurrent second intervals.

Claim 9

A method for detecting targets by radar, comprising the steps of: generating pulses of radio frequency energy; applying said pulses of radio-frequency energy to a controllable active antenna array means for forming a single pencil beam which may be steered in selected azimuth and elevation directions; tapering the aperture distribution of said antenna array means for causing said beam to have relatively low sidelobe levels; from time to time, controlling said active antenna array means for directing said pencil beam at selected elevation angles; controlling the pulse recurrence frequency of said generation of pulses of radio-frequency energy in response to the elevation angle of said pencil beam; controlling said generation of radio-frequency pulses for producing a single pulse during each of recurrent first and second transmit/receive intervals; controlling said antenna array means for causing said beam to be directed at a first azimuth angle during said first transmit/receive intervals and at a second azimuth angle different from said first azimuth angle during said second transmit/receive intervals; and receiving echo signals during said recurrent first and second transmit/receive intervals; and segregating said echo signals received during said first transmit/receive intervals from those received during said second transmit/receive intervals.

Claim 10

A method for detecting targets by radar, comprising the steps of: generating pulses of radio frequency energy; applying said pulses of radio-frequency energy to a controllable active antenna array means for forming a single pencil beam which may be steered in selected azimuth and elevation directions; tapering the aperture distribution of said antenna array means for causing said beam to have relatively low sidelobe levels; from time to time, controlling said active antenna array means for directing said pencil beam at selected elevation angles; controlling the pulse recurrence frequency of said generation of pulses of radio-frequency energy in response to the elevation angle of said pencil beam; controlling said generation of radio-frequency pulses for producing a single pulse during each of recurrent first and second transmit/receive intervals; controlling said antenna array means for causing said beam to be directed at a first azimuth angle during said first transmit/receive intervals and at a second azimuth angle different from said first azimuth angle during said second transmit/receive intervals; and receiving echo signals during said recurrent first and second transmit/receive intervals; and segregating said echo signals received during said first transmit/receive intervals from those received during said second transmit/receive intervals.