| 摘要 |
Antennas (A1-3) or antenna sections (4a-d) are positioned on a vehicle and are individually switched (S1-3) by an automatically-controlled switch unit (2) to a connection point (21) for diversity reception of signals (5). A unit (25), performs comparative tests of reception level in the HF channels carrying data flow at appropriate bandwidth (B). This unit is designed for rapid response. The delay is about 1/B, equal to the shortest possible level test duration Tp. Testing is initiated by the receiver (3) symbol clock (18), and is simultaneous with symbol identification in the received data flow. Successive tests are carried out in a comparator (10), sending change-over signals (23) to the switch unit (2). Following completion of each test cycle, a suitable reception signal is selected. This is repeated at short intervals, such that by varying the path length through a half wavelength of the high frequency carrier, a suitable receive signal is identified, updating at least 5 times in the interval.
|
