Radar system with elevation-responsive PRF control, beam multiplex control, and pulse integration control responsive to azimuth angle
First 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 array antenna means defining an azimuth broadside direction, said array antenna means being coupled to said signal generating means, and including a beam direction control input port, for generating pencil beams, the elevation and azimuth angles of which are controllable in response to elevation and azimuth components of beam direction control signals applied to said beam direction control input port;
beam direction control means coupled to said beam direction control input port of said array antenna means for generating elevation and azimuth components of said beam direction control signals, for controlling said pencil beams to scan in discrete elevation and azimuth angle increments over a predetermined volume during recurrent volume scan intervals;
PRF, beam multiplex, and pulse integration control means coupled to said signal generating means and to said beam direction control means, for generating said pulse control signals to represent a pulse recurrence frequency of said pulses radio-frequency energy, which pulse recurrence frequency is responsive to said elevation component of said beam direction control signals, and for applying said pulse control signals to said pulse control input port of said signal generating means 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 components of said beam direction control signals to said beam direction control input port of said array antenna means during said first and second transmit/receive intervals, respectively, said first and second azimuth components being selected to direct said beam in first and second spaced-apart azimuth directions, respectively, and for, during each scan of said pencil beam over said predetermined volume, controlling the total number of said pulses of radio-frequency energy generated by said signal generating means, and applied to said array antenna means at each of said discrete angle increments of said predetermined volume in response to said pulse control signals, such that the total number of said pulses of radio-frequency energy generated at each of said discrete azimuth angle increments during said scan of said pencil beam over said predetermined volume is responsive to the azimuth angle of said pencil beam measured from said azimuth broadside; and
receiving means coupled to said array antenna means for receiving echoes of said pulses of radio-frequency energy, said receiving means including pulse separating means for separating echoes received during said recurrent first intervals from echoes received during said recurrent second intervals.
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Accused Products
Abstract
A multipurpose system provides radar surveillance for air traffic control purposes. The system includes four separate active phased-array antennas, each with ±45° coverage in azimuth, from 0° to 60° in elevation. Each antenna element of each phased-array antenna is coupled by a low-loss path to the solid-state amplifier associated with a transmit-receive (TR) module. Each antenna produces a sequence of pencil beams, which requires less transmitted power from the TR modules than a fan beam, but requires more time because the pencil beam must be sequenced to cover the same volume as the fan beam. In order to scan the volume in a short time, the PRF is responsive to the elevation angle of the beam, so higher elevation angles use a higher PRF. Low elevation angle beams receive long transmitter pulses for high power, and pulse compression is used to restore range resolution, but the long pulse results in a large minimum range within which targets cannot be detected. A second scan is provided at low elevation angles with a short transmitter pulse to fill in the short-range coverage. Beams at higher elevation angles transmit pulse widths which are shorter than beams at low elevation angles so that the minimum range requirement is met without a second scan, which also reduces the time required for volumetric scan. The number of pulses which are integrated to produce a return increases off-axis, to restore system margin lost due to off-axis power gain reduction. The volumetric scan rate is increased by a dynamic scan regimen by which subsets of beams are pulsed with a high transmitter PRF but with a low effective beam PRF to reduce range ambiguity and preserve Doppler resolution without the usual increase of scan time. For best range resolution, Doppler processing is used, with range sidelobe pulse suppression applied separately to each Doppler frequency bin.
63 Citations
13 Claims
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1. A radar system, comprising:
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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 array antenna means defining an azimuth broadside direction, said array antenna means being coupled to said signal generating means, and including a beam direction control input port, for generating pencil beams, the elevation and azimuth angles of which are controllable in response to elevation and azimuth components of beam direction control signals applied to said beam direction control input port; beam direction control means coupled to said beam direction control input port of said array antenna means for generating elevation and azimuth components of said beam direction control signals, for controlling said pencil beams to scan in discrete elevation and azimuth angle increments over a predetermined volume during recurrent volume scan intervals; PRF, beam multiplex, and pulse integration control means coupled to said signal generating means and to said beam direction control means, for generating said pulse control signals to represent a pulse recurrence frequency of said pulses radio-frequency energy, which pulse recurrence frequency is responsive to said elevation component of said beam direction control signals, and for applying said pulse control signals to said pulse control input port of said signal generating means 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 components of said beam direction control signals to said beam direction control input port of said array antenna means during said first and second transmit/receive intervals, respectively, said first and second azimuth components being selected to direct said beam in first and second spaced-apart azimuth directions, respectively, and for, during each scan of said pencil beam over said predetermined volume, controlling the total number of said pulses of radio-frequency energy generated by said signal generating means, and applied to said array antenna means at each of said discrete angle increments of said predetermined volume in response to said pulse control signals, such that the total number of said pulses of radio-frequency energy generated at each of said discrete azimuth angle increments during said scan of said pencil beam over said predetermined volume is responsive to the azimuth angle of said pencil beam measured from said azimuth broadside; and receiving means coupled to said array antenna means for receiving echoes of said pulses of radio-frequency energy, said receiving means including pulse separating means for separating echoes received during said recurrent first intervals from echoes received during said recurrent second intervals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for radar detection of targets, comprising the steps of:
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forming a pencil antenna beam which may be controlled in elevation and in azimuth about an azimuth broadside direction; generating pulses of radio-frequency energy at a pulse recurrence frequency, and applying said pulses for transmission by said antenna beam; controlling said elevation angles and said azimuth angle to scan said beam at discrete positions over a predetermined volume of space during recurrent volume scan periods; controlling said pulse recurrence frequency of said generation of pulses of radio-frequency energy to be responsive to said elevation angle of said beam; controlling said generation of pulses to produce a single pulse during each of recurrent first and second transmit/receive intervals; controlling said azimuth angle during said recurrent first and second transmit/receive intervals to be 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; during any one volume scan period, generating and transmitting, on each beam, a number of pulses which is responsive to the azimuth angle of said beam as measured from azimuth broadside. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification