SU661715A1 - Synthesizer of a given frequency range - Google Patents

Description

The invention relates to radio engineering and can be used to create grids of stable frequencies.

A known frequency grid synthesizer comprising a tunable oscillator, a mixer, a first frequency divider, a phase detector and a low-pass filter, as well as a serially connected reference oscillator, a second frequency divider, a frequency detector and a code-voltage converter, the output of which is connected to another to the input of the tunable generator, while the output of the reference generator is connected to another mixer input via a frequency multiplier with a variable multiplication factor, the second output of the second divides L frequency is connected to another input of the phase detector, a first frequency divider output being connected to the other input of the frequency detector 1.

However, this device has continuous frequency jumps when operating in the frequency range, due to the fact that the intermediate frequency at the mixer output is formed by subtracting the output frequency of the multipliers from the frequency of the tunable generator, which, when located near the boundary

The output frequency range may be higher than the frequency of the tunable oscillator. Then synchronization of the synthesizer PLL ring at a frequency below the nominal frequency occurs.

The purpose of the invention is to eliminate false jumps in frequency when operating in the frequency range.

To do this, a frequency grid synthesizer containing a tunable oscillator, a mixer, a first frequency divider, a phase detector and a low pass filter, as well as a serially connected reference oscillator, a second frequency divider, a frequency detector and a code-voltage converter, the output of which is connected k. to another input of the tunable generator; with this, the reference oscillator is connected to a different input of the mixer via a frequency multiplier with a variable multiplier, the second output of the second Frequency coil is connected to another

0 input of the phase detector, and the output of the first frequency divider connected to another input of the frequency detector, between the output of the first frequency divider and the control input of the frequency detector a gating device is introduced, the second input of which is connected to the second output of the frequency divider, and the third input of the gating device is fed control signal ...

The drawing shows a structural electrical circuit of the proposed synthesizer.

The frequency grid synthesizer contains a tunable oscillator 1, a mixer 2, a first frequency divider 3, a phase detector 4 and a low-pass filter 5, as well as a series-connected reference oscillator 6, a second frequency divider 7, a frequency detector 8 and a gt-converter 9 code- the voltage, the output of which is connected to another input of the tunable generator 1, while the output of the reference generator 6 through a multiplier 10 frequency with a variable multiplication factor is connected to another input of the mixer 2, the second output of the second case The frequency unit 7 is connected to another input of the phase detector 4, and the output of the first frequency divider 3 is connected to another input of the frequency detector 8, and between the output of the first frequency divider 3 and the control input G frequency detector 8 a gating device 11 is introduced, the second input of which connected to the second output of the second divider 7 frequency, while a control signal is applied to the third input of the gating device.

The device works as follows.

The frequency of the reference generator 6, divided by the second frequency divider 7, is fed to the gating device 11 and to one of the inputs of the phase detector 4. The frequency of the tunable generator Ifnr converted in mixer 2 by a signal of a multiplier 10 with a variable multiplication factor at an intermediate frequency% divided by the first frequency divider 3 N times, is fed to another input of the phase detector 4. In this case, the intermediate frequency is formed as fn).

With equal frequencies at the inputs of the phase. detector 4 in the ring of the synthesizer of the synthesizer is set to synchronization mode. The operating point of the phase detector 4. is located in that portion of its static characteristic that is programmed in the gating device 11 by a control signal and a sequence of pulses coming from the second frequency divider 7. In this case, the signal from the output of the gating device 11 in the form of a constant voltage allows the normal operation of the frequency detector 8.

The frequency detector 8 and the code-voltage converter form an injector search circuit and operate only in the transition mode of the PLL (for example, if the output frequency of the synthesizer is less, i.e. when the dividing factor of the primary divider changes 3 frequencies). In this case, with you, the stroke of the frequency detector 8 is removed a sequence of pulses, the frequency of which is proportional to the difference of the frequencies arriving at its inputs. In code-converter 9, it is converted into stepwise variable voltage. This voltage tunes the generator 1 until the frequency difference at the inputs of the phase detector 4 becomes zero, i.e. until synchronization occurs.

In the process of tuning the oscillator 1. or at the moment the synthesizer f is turned on, fap fj can be formed for and synchronization is possible on the channel that is mirrored in the intermediate frequency. In this case, the operating point of the phase detector 4 must be on the opposite part of the characteristic , as the transfer ratio of the mixer 2 changed the sign. However, this will not happen as the other current of the characteristics of the phase detector 4 is gated, and a pulse signal will come from the output of the gating device 11 to the input of the frequency detector 8.

At the same time, even at equal frequencies at the inputs of the frequency detector 8, coming from dividers 3 frequencies and 7 at the output of converter 9, the voltage is generated by a step voltage, which tunes generator 1 until synchronization occurs at fnb ft-f iw. Then again there will be equality of frequencies at the inputs of the frequency detector 8 and phase detector 4, and at the output of code-voltage converter 9 and gating device 11 there will be a constant voltage level. Thus, the possibility of false synchronization is eliminated.

From the control signal to the gating device 11, we can program one or the other part of the characteristics of the phase detector 4.

Thus, the proposed synthesizer eliminates false frequency jumps when operating in the frequency range, while greatly simplifying and increasing reliability.

Claims (1)

1. Hughes R. J., Sacha R. L, "The Lohap Freguency Synthesizen" Frequence, 1968, V 6, No. 8, tj. 12-21.