SU114654A1 - Method for automatic tuning of the contours of multi-stage VHF and DACs transmitters - Google Patents

Description

The known methods of automatic tuning of multi-stage transmitters do not meet the requirements necessary to ensure very fast tuning of the microwave transmitters.

The peculiarity of the proposed method is that the natural frequency of the resonant circuit of each stage varies with some low compared to the carrier frequency, and the resulting amplitude-modulated carrier voltage, after detection, is used to control the drives of the tuning elements of the circuit.

The proposed sleep-gob provides mutually independent simultaneous tuning of all stages, since the natural frequency of each of the anode circuits is modulated by its own, different from the other, low frequency, and the auxiliary tuning equipment has the necessary selectivity.

This feature of the method allows to achieve a very high speed of adjustment.

FIG. 1 shows a circuit diagram of a circuit with modulation of its resonant frequency; in fig. 2 - amplitude modulation of the voltage on the circuit when the natural frequency changes; in fig. 3 is a block diagram of a control device for implementing the proposed automatic tuning method.

This method is based on the following.

If by changing, for example, capacitance Cn (Fig. 1), periodically with frequency 2, to change the natural frequency of the contour when the emf is included in the same contour. If the frequency is%, then amplitude modulation of the voltage on the circuit of the latter occurs. This process is presented

in fig. 2. If to designate: X - 2Q - - - the generalized mismatch concerning carrier%, where Q-quality factor and m-coefficient of the module about

No. 114654- 2 -

BQ (the modulation law is assumed to be sinusoidal for simplicity), it is possible to obtain a relation between the amplitude of the envelope of the modulated voltage and the detuning X in the form:

  (l (1)

Expression (1) is derived under the condition that the modulation depth T is small, and a small portion of the resonance curve is linear. For practical purposes, the accuracy of this expression is quite sufficient.

If a linear envelope is selected by linear detection, then, as can be seen from expression (1), at the time of tuning, its expression will be zero, and its phases on both sides of the tuning will differ by 180 °. Expression (1) in the function can be represented in a dimensionless form, as

PO. „, 2

mV.

Z 2, (1 + /) - (2)

- Tymax

FIG. 3 is a block diagram illustrating the operation of the tuning system: / - tunable transmitter cascade; 2 - high-frequency voltage detector; 3 - cascade with adjustable gain; 4 - regenerative filter; 5 phase equalization cascade with polarized relay; b - electromechanical vibrator; 7 - modulating generator; 8 - phase shifter.

The high-frequency voltage modulated by the vibrator 6 is detected by the detector 2. The variable component of the detected voltage is fed to an amplifying cascade with adjustable gain 3, where it is amplified and fed to the regenerative RC filter 4. The presence of such a filter only allows to isolate the voltage in this control path frequency 2, which is modulated by the transmitter cascade controlled by this drive. If the filter bandwidth is properly selected, and the attenuation of this filter for frequencies S modulating the previous stages is sufficiently large, then this control channel operates independently of the tuning process of the previous stages.

After filter 4, the voltage is applied to the phase-equalizing cascade 5. The same voltage is applied to the same cascade, f /, phase

which is rigidly connected to the phase of the voltage supplying the vibrator 6. In the reference voltage U is the phase shifter 8, with

which his initial phase is established. The output voltage of the cascade 5 is supplied to a polarized relay that controls the wiring of the wire.

Subject invention

Claims (2)

1. The method of automatic tuning of the contours of a multi-stage VHF and DAC transmitter, characterized in that, in order to obtain a high tuning rate over the range, the natural frequency of the resonant circuit of each stage varies with some low compared with the carrier frequency, and the resulting amplitude post-detection modulated carrier voltages are used to control the drive of the circuit tuning elements of this stage. 2. A method according to claim 1, characterized in that, in order to eliminate the interference of the tuning systems of the individual cascades of the transmitter, the control signal of the tuning elements is passed through the appropriate filters. t Urn