JPS6416741U - - Google Patents

Description

[Brief explanation of the drawing]

Figure 1 shows a configuration example of a conventional direct modulation frequency synthesizer, Figure 2 shows modulation sensitivity characteristics depending on the oscillation frequency of the VCO, and Figure 3 shows a configuration example of a direct modulation frequency synthesizer that cancels modulation sensitivity deviations according to the present invention. , FIG. 4 is a characteristic diagram showing the operation in which the modulation sensitivity deviation is canceled out in the configuration shown in FIG. 3. 1: Reference signal generator, 3: Phase comparator, 5: Voltage controlled oscillator, 7: Audio circuit, 8: Variable gain circuit.

Claims (1)

[Scope of utility model registration request] It is equipped with a reference signal generator, a phase comparator, a loop filter, a voltage controlled oscillator (hereinafter referred to as VCO), and a variable frequency divider that divides the output signal of the VCO, and the output of the reference signal generator and the output of the variable frequency divider are A gain whose gain is configured to be compared by the phase comparator and to apply the comparison output to the VCO via the loop filter, and whose gain can be varied by the signal output from the phase comparator is connected to the modulation terminal of the VCO. In a direct modulation frequency synthesizer in which the output of a variable circuit is connected and a modulation signal is input to the input of the variable gain circuit to obtain a frequency modulated wave as the output signal of the VCO, a VCO corresponding to the oscillation frequency of the VCO is used.
A direct modulation method characterized in that the gain of the variable gain circuit is varied by a signal output from the phase comparator so that the product of the modulation sensitivity of the CO and the gain of the variable gain circuit is constant. frequency synthesizer.