Tuners – With switching means – Capacitor only modified or substituted by switching
Patent
1992-09-01
1994-04-05
Gensler, Paul
Tuners
With switching means
Capacitor only modified or substituted by switching
334 59, 375 63, H03J 524
Patent
active
053009045
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The invention relates to a circuit arrangement for the tank circuit of a high-frequency transmitter output stage operated with frequency shift keying, equipped with a tank circuit capacitor, a tank circuit inductor and a feeder for supplying high-frequency energy to the tank circuit and with a switch for switching the tank circuit to resonance with the other transmission frequency in each case.
Such a circuit arrangement is known, for example, from US-A-3395 351.
In this circuit arrangement, the resonance frequency of the tank circuit is switched by switching an additional inductor connected in parallel to parts of the tank circuit inductor on or off, whereby the tank circuit inductor contains a transformer with a primary winding and secondary winding, whereby the number of turns of the primary winding is less than the number of turns of the secondary winding, whereby the output signals of the transmitter can be supplied to the primary winding and whereby switch-over of the tank circuit to the second resonance frequency always occurs when the first frequency is not present at the primary winding feeder.
This known, quite complex circuit arrangement is intended for a high-power, high-frequency transmitter operating with frequency shift keying where it is important to considerably reduce the control power required for switch-over of an inductor.
In addition, a circuit arrangement for remote control of toy cars is known from GB - A - 994 832, whereby this is located within an inductive wire loop which forms part of an oscillating circuit connected to a small transmitter. The oscillating circuit is completed by a number of capacitors, of which one can be optionally connected in each case. In other words, the resonance frequency of the oscillating circuit consisting of the inductive loop and only one capacitor in each case can be optionally switched to several different control frequencies for the toy cars.
In transmitters of the type mentioned above, it is of decisive importance that the transmitter efficiency is as high as possible, whereby this is also determined by the quality of the tank circuit, this representing the external resistance of the transmitter output stage.
As is known, such high-frequency transmitters are normally pulse-keyed with two different frequencies f1 and f2 for transmission of binary-coded signals, whereby the pulses of one frequency may represent binary "0", for example, and the pulses of the other frequency binary "1". Other types of pulse string representation are naturally also possible, as long as they consist of two different frequencies in this case.
SUMMARY OF INVENTION
The task of the invention is to safeguard optimum adaption of the output circuit or tank circuit for both frequencies during frequency shift keying operation for transmitter output stages of the type mentioned above.
This is achieved by the invention in the manner described in patent claim 1. Reference should be made to the other patent claims for further embodiments of the invention.
The invention will now be described in more detail on the basis of an example embodiment in schematic form in conjunction with the enclosed drawing.
BRIEF DESCRIPTION OF DRAWING
The schematic diagram shows a tank circuit, i.e. an output circuit of a high-frequency transmitter output stage, as could be used, for example, for remote control of models or similar.
DESCRIPTION OF PREFERRED EMBODIMENT
Transmitters of this type generally possess a very low power rating, so that high efficiency is crucial.
For the purpose of explanation, the transmitter will be operated as a transmitter with frequency shift keying between two frequencies f1 and f2 and be described as such. The signals are high-frequency signals whose frequencies should be located at around 150 kHz, for example, i.e. in the longwave band. This naturally does not represent any restriction of the invention concept and frequencies can be selected corresponding to the frequency bands available for the respective purpose.
A circuit arrangement suit
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patent: 3395351 (1968-07-01), Deise et al.
patent: 3939422 (1976-02-01), Deise
Gensler Paul
Topholm & Westermann ApS
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