'Improvements in channel barrier filters for suppressing the widest possible from a TV channel'.

摘要

In a double-tuned circuit channel rejection filter for the greatest possible suppression of a television signal, preferably in UHF bands IV/V, and transmission with minimum attenuation in the remaining operating frequency range, the two parallel resonance circuits, constructed in chamber design and mutually shielded by a metallic partition are connected together via a connecting line and inductively coupled to the input and output terminal, respectively. To extend the possible uses for this channel rejection filter by improving the selectivity whilst at the same time increasing the depths of the rejection notch and return loss in a simple and inexpensive manner, the resonance circuits are constructed in such a manner that the connecting line compensates for the coupling inductances even at the highest UHF frequencies and produces adequate decoupling of the two resonance circuits. For this purpose, its dimensions are selected in such a manner that it exhibits a length of a quarter of the mean operating wavelength and the amount of its capacitive impedance approximately corresponds to that of the two coupling inductances; in addition, the resonance lines of the two parallel resonance circuits in each case face the partition with their end section connected to earth and are arranged approximately perpendicular to the partition. A particularly advantageous possible use of this channel rejection filter in receiving systems consists in connecting it in parallel with a highly selective channel amplifier for amplifying the channel to be rejected in the channel rejection filter. IMAGE