A system and method for automatically generating a return beam in the direction of a received beam. The inventive system (10) includes a phased array antenna (12) for receiving a radio frequency signal having a first wavefront from a first direction. In response to this signal, the invention (10) provides a second signal having a second wavefront. The second signal is a phase conjugate of the first signal and is transmitted in a reverse direction relative to the direction of the first signal. In the illustrative embodiment, the invention includes a plurality of phase conjugators each of which are disposed in a transmit/receive module and coupled to an associated radiating element. Each of the phase conjugators includes a mixer (60) having the input signal as a first input thereto. The input signal has a first frequency and a first phase. A second signal having a frequency equal to twice the first frequency is input to each mixer (60) from a reference frequency module (30) such that the output of the mixer includes a component representative of the negative of the first phase. The output of each mixer (60) is filtered to extract a signal component having a negative phase relative to the input signal. These signal components are then transmitted as the phase conjugated wavefront. This process will occur for each signal when multiple signals are received within the field of regard of the phased array antenna (12).
A time-reversal imaging radar system for acquiring an image of a remote target includes an antenna array having a plurality of spaced-apart antennas, and a transceiver coupled to the antenna array for alternately transmitting a radar signal via the antenna array toward the target and for receiving target-reflected radar signals. The transceiver includes means for multiple-pass time-reversing the transmitted and received radar signals whereby coherent beam focusing is realized at both the target and at the receiver to thereby enhance the resolution of the acquired target image.
Provided is an antenna transceiver system for transmitting and receiving voice, digital data, radar and IR signals, and for processing received signals for use by an operator. The system includes an antenna array having a plurality of radiating elements, each element connected to a transmit/receive ("T/R") module. Each T/R module includes phase shifters, as well as a phase conjugation module for transmitting a return signal to a location along a beam path of an incoming signal. Transmission of the return signal does not require knowledge of the location of either the signal source or the antenna transceiver system. The antenna transceiver system is disposed on a plurality of vertically aligned planes integrated into a compact unit. The units can be embedded in headgear of a user, allowing for hands-free operation of the system. Alternatively, the antenna transceiver system can be integrated into a vehicle, man-transportable backpack, or other designated platforms.
A phased array antenna adapted to be mounted in a helmet. In the illustrative embodiment, the antenna comprises a substrate and an array of radiating elements disposed on said substrate, each of the elements including a-resonant cavity and a mechanism for feeding the cavity with an electromagnetic signal., The cavity is formed in a multi-layer structure between a ground plane and a layer of metallization. A radiating slot or slots are provided in the layer of metallization. A first layer of dielectric material is disposed within the cavity. The feed mechanism is a microstrip feed disposed in the first layer of dielectric material parallel to a plane of a portion of the substrate over which an associated element is disposed. A layer of foam is disposed between the layer of dielectric material and the ground plane. Second and third parallel layers of dielectric material are included in each element. The second layer is disposed adjacent to the ground plane. A layer of element interconnection circuitry is disposed between the second and third layers of dielectric material. A transmit/receive module or circuitry for each element is secured to the third layer of dielectric material. The substrate may be conformal or conformable, as well as rigid. An arrangement is included for steering a beam transmitted or received by the antenna.
