D.J. Edwards

Multi-beam adaptive base-station antennas for cellular land mobile radio systems

The authors address the problem of meeting the proliferating demands for mobile telephony within the confinements of the limited radio spectrum allocated to these services. A multiple-beam adaptive base-station antenna is proposed as a major system component in an attempt to solve this problem. The approach is demonstrated by employing an antenna array to resolve the angular distribution of the mobile users as seen at the base-station site, and then using this information to direct beams towards the mobiles in both transmit and receive modes. The energy associated with each mobile is thus confined within the addressed volume, greatly reducing the number of co-channel cells. For a given performance criterion, this results in an increase in the spectral efficiency or capacity of the network. The concept is demonstrated using results generated by a computer simulation of a simplified mobile scenario. The realization of a fully adaptive base-station antenna test rig is discussed.<<ETX>>

A diversity combining antenna array for land mobile satellite communications

A unified approach to adaptive antenna array design and transceiver signal processing architectures is proposed for the user segment of the land mobile satellite communication service. This technique is described in its conceptual form, and compared with steered antenna array configurations currently favored for this class communication system. The proposed system uses established diversity combining techniques previously developed for mobile terrestrial radio. It is suggested that a diversity-based receiver architecture would allow the coherent recombination of the multipath signal energy present at the mobile terminal site, and thereby enhance system performance for a given link budget. The cophasing of the multipath signals can be implemented using a FFSR (feedforward signal regeneration) signal-processing architecture, which uses the presence of a pilot-tone within the communications channel. On transmit, a retrodirective beam is formed towards the active satellite. The economic viability of such a transceiver is also considered.<<ETX>>

Tracking receiver design for the electronic beam squint tracking system in the mobile environment

The authors investigate the beam squint technique from the viewpoint of the tracking receiver in a mobile satellite environment, together with the more general problems experienced by tracking receivers in this situation. This technique is detailed with particular reference to the design and characterization of an optimum tracking receiver, and the new problems which the system poses in this area. The system is described with an identification of the factors in existing receivers which limit the performance of the electronic tracking technique. Using a computer simulation, a fundamental understanding of the physical processes involved is presented and some comprehensive experimental results are included to validate the conclusions and proposed solutions. The techniques described may also be applied to conventional tracking systems, with a useful improvement in performance.<<ETX>>

Electronic beam squint tracking for land mobile satellite terminals

Preliminary results from an investigation of the applicability of the electronic beam squint (EBS) tracking technique to land mobile satellite terminals. Two systems are described, based on the EBS technique, which use both conventional waveguide and phased-array technology. Results are presented covering the error-detection capabilities of the systems, along with some operational analysis to illustrate the dynamic capabilities of the performance of such schemes. The systems described are intended for use at L-band and Ku-band. Both techniques appear to offer a simple, and hence cost-effective, alternative to the current terminal arrangements.<<ETX>>