| 摘要 |
Frequency stabilizing in a, for instance star/branched-tree shaped, network can be well executed by locking the frequencies (f1) of the transmitters (T1) in the network center to a common reference frequency source (CFC) and, moreover, per duplex connection, locking (at a fixed frequency distance) the frequency (f2) of the subscriber's transmitter (T2) to the transmission signal (t1) as received from the network center's transmitter (T1). Per duplex connection only the subscriber's local oscillator (L2) has to be tuned so that the transmission signal from the network center is received optimally. If the subscriber's local oscillator is tuned thus and the subscriber transmitter's frequency has the right frequency offset to the tuned local oscillator frequency (f4), at the network center's side, signals from the subscriber's transmitter will be received optimally too if the local oscillator (L1) of the network center's receiver (R1) is set at a certain (predetermined) frequency offset to the signal transmitted to the subscriber's receiver. Frequency setting, at the network center's side and at the subscriber's side, can be executed by means of auxiliary receivers (R1a,R2a) and AFC-units, generating the various frequency control signals, or by means of the receivers (R1,R2) already in use, provided with multiple pass filters and AFC-units. For achieving relative low IF frequencies, certain frequency orders are preferred.
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