Circuit arrangement for the tank circuit of a high-frequency transmitter output stage operated with frequency shift keying

Claim 1

Circuit arrangement for the tank circuit (1) of a high-frequency transmitter output stage operated with frequency shift keying between a first and second frequency (f 1 , equipped with a tank circuit capacitor (2) and a circuit inductor (3) and with a first switch (5) for supplying high-frequency energy to the tank circuit, as well as with a second switch (4) for switching the tank circuit to resonance with one of the transmission frequencies (f1, f2) in each case by connecting an additional capacitor to parts of the tank circuit inductor, the latter consisting of a transformer (3) with a primary winding (3a) and a secondary winding the number of turns of the primary winding being less than the number of turns of the secondary winding, the output signals of the transmitter being supplied to the primary winding and switch-over-of the tank circuit to the second resonance frequency occurring when the first frequency is not present at the feeder to the primary winding, the secondary winding of the transformer (3) consisting of two winding sections (3b1, 3b2) with an intermediate tap, at which the additional capacitor (2a) is connected, and the second switch (4) being connected between the additional capacitor (2a) and a common base point of the tank circuit so that the additional capacitor (2a) is connected in parallel with only a part (3b2) of the secondary winding when the second switch (4) is closed.