Retrodirective antenna array architectures for wireless communication systems

When receiving a signal from an unspecified direction, retrodirective antenna arrays are able to respond by reradiating a signal towards the source direction without any prior knowledge of the incoming signal direction. This function is performed automatically, without the use of phase-shifters or digital circuitry, which are often used in conventional phased arrays. For this reason, retrodirective arrays are not limited by drawbacks associated with such components, namely phase shifter insertion loss at high frequencies and finite phase control precision as well as the digital circuit speed 'bottle-neck' related to conventional digital beamforming and smart antenna systems. The capability to perform high gain antenna pointing automatically makes the retrodirective array an attractive candidate for advanced digital mobile communication systems.; This dissertation focuses on methodologies to use retrodirective arrays in communication scenarios. In most cases, retrodirective arrays are used as transponders, which are only able to transmit data to an interrogator. This dissertation aims to explore different retrodirective transponder architectures and also introduces new array architectures that are able to act as full-duplex front-ends.; A novel retrodirective array architecture that enables the retrodirective array to respond to an interrogator at the same transmitted frequency with no previous knowledge of the transmission frequency or position is discussed. The frequency autonomous characteristic of this architecture has the features of increased security and reduced beam squint. A prototype array was constructed and measurements show excellent retrodirectivity at various frequencies.; A radar target/communication device which is intended to both facilitate radar imaging and establish a self-tracking communication link between ground terminal and mobile radar station is proposed. The device is realized using a retrodirective array with full-duplex capability. Demonstration of 10 Mbps data receiving and transmitting functions are presented along with its automatic beam-steering ability. Frequency autonomous digital beamforming is also implemented.; A more innovative architecture approach for implementing full-duplex communication using a retrodirective array transceiver is presented using mutually-exclusive modulation techniques: uplink data is contained in time domain while the downlink data is contained in the polarization of the retrodirected signal. A novel phase conjugation mixer, which is also able to modulate the polarization sense of the output radiation is discussed for use in the retrodirective transceiver array.; The final topic of this dissertation is the design of a polarization selective receiver integrated with antenna. The structure utilizes the same phase-conjugation process used in retrodirective arrays to achieve 'switchless switching.'...