Compensating circuit for intermodulation interference of VHF signal - interference signal being filtered out by anti-parallel diodes and inverted, esp. for third order interference

摘要

Interference due to intermodulation in a VHF-receiver, i.e. third order intermodulation products in an aerial amplifier, is compensated in this circuit without loss of bandwidth and negligible extra power by the use of two diodes connected opposite/parallel. The incoming VHF-signal (13) is coupled via capacitor (21) to two parallel/opposite diodes (23,26). Due to their non linear characteristic intermodulation products of the third order are produced whose amplitude may be varied by regulating the direct current of the diodes. The signal is then passed through a high- pass filter (29) and is inverted (31) before being mixed (32) with the incoming VHF-signal.