| 摘要 |
Radio receivers, such as DAB receivers, require filters which are used to discriminate between wanted radio stations and unwanted (interfering) stations. Close channel frequency spacing places high performance requirements on the selectivity of the radio receiver. However, when using on-chip active filters, increased selectivity requires higher power consumption, but is not necessary for all reception conditions. In the present invention, the order of the selectivity filtering is dynamically selected according to reception conditions, with consequent power savings. This is beneficial to battery life in portable applications. The method involves the measurement of signal level (RSSI) before and after the filter. RSSI measurements are taken as filters of different orders are switched into circuit. The set of measurements is compared with a set of templates to ascertain the correct filter to meet the specification for sensitivity in the presence of adjacent channel interference. The comparison algorithm performs a 2-dimensional search over all combinations of interferer distance and power level. A decision can be made on the basis of rms error. |
