Self monitoring/calibrating phased array radar and an interchangeable, adjustable transmit/receive sub-assembly

A phase adjustable T/R sub-assembly for a set of i antenna elements where i is a small integer not including 1 and a power of 2, said T/R sub-assembly being adapted for use with a plurality of similar T/R sub-assemblies in a self-calibrating phased array radar apparatus having m.times.n antenna elements and including a calibration network providing a calibration path for each set of i antenna elements, said T/R sub-assembly comprising:

• (1) j stripline signal input ports, where j is a small integer including 1, less than or equal to i,
• (2) a stripline to microstrip divider network and transition having j stripline ports, each connected to a signal input port and i microstrip ports,
• (3) i transmit/receive modules using microstrip transmission paths, each module containing the active electronics for processing the signals of one associated antenna element,
• each module having:
• (i) a bidirectional controllable phase shifter disposed in a transmit/receive operating path connected to one microstrip port of said divider network and transition having a control for setting the phase,
• (ii) a power amplifier disposed in the transmit operating path for amplifying the exciter signal,
• (iii) a low noise amplifier disposed in the receive operating path for amplifying signals from the associated antenna element,
• (iv) a pair of three port transmit/receive branching means, the first branching means having a transmit/receive port coupled to said phase shifter for coupling signals from said phase shifter via the power amplifier to an associated antenna element during transmission and the second branching means having a transmit/receive port for coupling signals from the antenna via the low noise amplifier to said phase shifter during reception,
• (4) i microstrip to stripline transitions coupled to the transmit/receive ports of said second branching means,
• (5) a stripline antenna circuit comprising:
• (i) i linearly aligned adjacent antenna elements,
• (ii) i directional calibration couplers disposed between said transitions and said antenna elements, each having an antenna port coupled to an antenna element, a transmit/receive port coupled to the stripline port of one transition and a calibration port;
• signals received by said antenna being internally coupled to said transmit/receive port, signals coupled to said transmit/receive port being internally coupled to said antenna port and said calibration port, and signals coupled to said calibration port being internally coupled to said transmit/receive port, and
• (iii) a corporate feed network having a singular port for connection to a calibration network internally coupled to i plural ports through paths of equal electrical length, each plural port being connected to the calibration port of each calibration coupler for serially connecting each transmit/receive operating path with a path in said calibration network to facilitate transmit/receive operating path calibration.

A combination for calibration of the transmit path from the exciter to each antenna element and of the receive path from each antenna element to the receiver in an m.times.n element phased array radar apparatus, comprising:

• A. an exciter providing a signal for calibration and transmission,
• B. a receiver including a calibration error sensing circuit having a reference port coupled to said exciter and a measurement port,
• C. beamforming means providing m.times.n/j plural ports where j is a small integer including 1, disposed in the transmit/receive operating paths from exciter/receiver to antenna elements, said beamformer means having a singular port internally coupled to plural ports, said singular port leading to exciter/receiver, and each of said plural ports leading to a subset j of antenna elements, said beamforming means further including means for separating signals proceeding from the exciter to the antenna elements from signals proceeding from the antenna elements to the receiver, the respective transmit and receive operating paths being coincident at the beamformer plural ports,
• D. a corporate calibration feed network providing a singular port internally coupled to (m.times.n/i) plural ports where i is a small integer, each path being of known electrical length to provide a calibrating path for each antenna element to the exciter/receiver,
• E. an (m.times.n/i) fold plurality of transmit/receive sub-assemblies, each disposed in the transmit/receive operating paths for each subset of i antenna elements, each sub-assembly comprising
• (1) i transmit/receive module(s), each module containing the active electronics for processing the signals of one associated antenna element,
• each module having:
• (i) a bidirectional phase shifter disposed in a transmit/receive operating path,
• (ii) a power amplifier disposed in the transmit operating path for amplifying the exciter signal,
• (iii) a low noise amplifier disposed in the receive operating path for amplifying signals from the associated antenna element,
• (iv) a pair of three port transmit/receive branching means for coupling signals from the exciter via the phase shifter, via the power amplifier to an associated antenna element during transmission and for coupling signals from the antenna via the low noise amplifier via the phase shifter to the receiver during reception, the transmit/receive port of the first branching means being coupled to said phase shifter,
• (2) an antenna circuit coupled to the transmit/receive ports of said second branching means comprising:
• (i) i linearly aligned adjacent antenna element(s),
• (ii) i directional calibration coupler(s) disposed between said transitions and said antenna elements, each having an antenna port coupled to an antenna element, a transmit/receive port coupled to the stripline port of one transition and a calibration port;
• signals received by said antenna being internally coupled to said transmit/receive port, signals coupled to said transmit/receive port being internally coupled to said antenna port and said calibration port, and signals coupled to said calibration port being internally coupled to said transmit/receive port, and
• (iii) a network having a singular port for connection to a calibration network internally coupled to a set of i port(s) through paths of substantially equal electrical length, each of said i set of ports being connected to the calibration port of each calibration coupler for serially connecting each transmit/receive operating path with a path in said calibration network to facilitate transmit/receive operating path calibration, and
• F. means for selectively switching the exciter output for transmit operating path measurement into a loop consisting initially of the transmit operating path, secondly of a calibrating path, and finally returning to the receiver measurement port and for switching the exciter output for receive operating path measurement into a loop consisting initially of a calibrating path, secondly of a receive operating path, and finally returning to the receiver measurement port.