Abstract: In a cellular mobile telecommunications system the position of a mobile station can be estimated in terms of its bearing and range from a cell site. A multi-element direction finding antenna at the cell site receives signals from the mobile station and a receiver circuit estimates the bearing using the relative phase of signals received at different antenna elements and estimates the range by measuring round trip delay of signals to and from the mobile station. Motion of the mobile station can introduce errors into the bearing estimate due to frequency offset and frequency spread when element sampling is non-simultaneous. Compensation for these errors is introduced by using signal samples successively received at the same antenna element to estimate Doppler frequency offset and spread. It is necessary to ensure accurate calibration of the direction finding antenna and the receiver circuit.

Abstract: In a cellular mobile telecommunications system the position of a mobile station can be estimated in terms of its bearing and range from a cell site. A multi-element direction finding antenna at the cell site receives signals from the mobile station and a receiver circuit estimates the bearing using the relative phase of signals received at different antenna elements and estimates the range by measuring round trip delay of signals to and from the mobile station. Motion of the mobile station can introduce errors into the bearing estimate due to frequency offset and frequency spread when element sampling is non-simultaneous. Compensation for these errors is introduced by using signal samples successively received at the same antenna element to estimate Doppler frequency offset and spread. It is necessary to ensure accurate calibration of the direction finding antenna and the receiver circuit.

Abstract: A phase array antenna is monitored by applying to each element of the array in turn a signal known characteristics, detecting the signal output from the selected element as a result of the applied known signal, and comparing the detected signal with the applied signal whereby to monitor changes in the applied signal due to the signal path. The detection is preferably carried out using a single monitoring unit in the near-field of each antenna element. Alternatively the detection is carried out using a single source of applied signals a number of individual monitoring units one for each element of the array, and a switching device for selecting the element of the array to be monitored.

Abstract: Interference on a differential signal received at a first input to a digital data system processor is minimised or cancelled by summing a weighted portion of a local field signal with the differential signal. The local field signal may be a common-mode signal from the same line as the differential signal received at a second input. Weight may be a complex weight which shifts the local field signal in amplitude and phase. A weight control signal is derived from a comparison processor which compares the processed outputs of signal processors. Signal processors are preferably Discrete Multi-tone processors. Several iterations of this technique may be performed to establish an accurate weighting value.