JPS58182902A - Frequency modulator under frequency synchronization control - Google Patents

Abstract

PURPOSE:To obtain a modulator of small-scale circuit constitution by detecting the polarity of a difference frequency between a reference frequency and the mean frequency of a frequency-modulated wave, and performing frequency synchronization. CONSTITUTION:A frequency difference polarity detector 7 detects whether the difference of the frequency of a voltage-controlled oscillator 6 from the frequency of a reference frequency oscillator 1 is positive or negative by making a comparison between both. Binary pulses from this detector 7 are sent to a up/ down counter 8 to output binary pulses based upon whether the shift in the mean frequency of the oscillator 6 from the reference frequency and they are converted into an analog value by a D/A converter 9. The output of this converter 9 is converted almost into a direct current by a loop filter 4' to obtain a control voltage, which is fed back to the oscillator 6 to synchronize the mean frequency with the reference frequency of the oscillator 1. Thus, the need for a frequency divided of large-scale circuit constitution is eliminated to reduce the circuit constitution.

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a frequency modulator (frequency synchronization control frequency modulator) that synchronizes the average frequency of a frequency-modulated wave with a reference frequency, and is particularly applicable to broadband audio transmission. This invention relates to a frequency synchronization control frequency modulator that can be realized with a small-scale circuit when used.

(b) Prior Art and Attractive Points FIG. 1 is a block diagram of a conventional frequency synchronization control frequency variation vj4 gain.

In the figure, 1 is a reference frequency oscillator, 2. 2' is a 1/N branch counter, 3 is a phase comparator, 4 is a loop filter, 5 is an adder circuit, 6 is a voltage controlled oscillator, and V is the amplitude of the variable a14.

In operation, the output frequencies of the voltage-controlled oscillator 6 and the reference frequency oscillator 1, which oscillate at a constant frequency, are set to 1/N by the 1/N frequency division counters 2', 2', and the modulation index, metal processing, and phase are adjusted. Compare the phase with comparator 3? l! lI masu range all 2
Within π radians, the 1 difference voltage due to the phase difference is passed through the loop filter 4 to become almost a 1u current component, and is fed back to the voltage controlled oscillator 6 via the adder circuit 5, and the average frequency of the voltage controlled oscillator 6 is used as a reference. It is synchronized with the frequency of oscillator 1.

When frequency modulation is used, the amplitude V of the modulation signal is added to the adder circuit 5.
In addition to this, frequency modulation is performed by increasing or decreasing the frequency from the center leg mantissa (average frequency) of the voltage controlled oscillator 6 depending on the magnitude of the amplitude.However, in the case of broadband audio transmission, the minimum frequency is about 30Hz. Since the first harmonic of the reed-shaped V-furrow harmonic is generally 75 kHz, the rock index is 75000/
30 = 2500 radians, and in order to make this t2π radians, N of the 1/N frequency division counters 2 and 2' must be
There is a need to set it to t-400, 1/N frequency division counter 2,
There is a drawback that the circuit scale of 2' becomes very large, and the circuit scale of the frequency synchronization control frequency modulator becomes large.

(c) Object of the Invention An object of the present invention is to provide a frequency synchronization control frequency modulator that can be realized with a small-scale circuit when used for broadband audio transmission.

(d) Structure of the Invention In order to achieve the above object, the present invention detects the polarity of the running frequency between one reference frequency and the average frequency of the frequency-modulated wave, and the phase difference between the two frequencies is 2π radian or more. time, lI
It controls the center wave number of the voltage controlled oscillation which outputs all +14 control pulses and the Ml wave number variable PLV, which eliminates the need for a frequency divider which increases the circuit scale, and allows the frequency synchronization side to be achieved with a small circuit configuration. It is characterized by making it possible to realize the Goshu Kaikai Hen W4 book.

(cl Embodiments of the Invention Below, embodiments of the present invention will be explained according to the drawings.
The figure is a block diagram of a frequency control frequency adjuster according to an embodiment of the present invention.

In the figure, those having the same functions as those in FIG.

7 is a frequency difference polarity detector, 8 is an up/down counter,
9 is a digital-to-analog converter (hereinafter referred to as a D/A converter), and 4' is a loop filter' (11-bore).

The operation is based on the frequency of the reference frequency oscillator 1,
The frequency difference polarity detector 7 compares and detects whether the difference with the M1 wave number of the voltage controlled oscillator 6 is positive or negative, and JI! Binary pulse according to Ll wave number difference (represents whether the frequency difference is stopped or negative)
is sent to the up/down counter 8 to output a binary pulse depending on the positive or negative difference between the average frequency of the voltage 111# oscillator 6 and the reference frequency, which is converted into an analog value by the D@A converter 9.

In this case, if the voltage Ill 111 is equal to the average frequency of the oscillator 6 and the reference frequency number, the output of the A converter 9 is 12
Set it to the center value of the values (l and 0). The output of the D-A converter 9 is reduced to almost 11 currents by suppressing interfrequency components and inactive waves by the loop filter 4', and is set to 11 so as not to affect the amplitude V of the modulation signal, and the control voltage is The average frequency is fed back to the voltage controlled oscillator 6 so that the average frequency is synchronized with the reference frequency of the reference frequency oscillator 1. Of course, when frequency modulation is performed, in addition to adding the amplitude modulation of the variable leg signal to the frequency modulation path 5, the frequency is increased or decreased from the center frequency (average frequency) of the voltage controlled oscillator 6 depending on the width of the amplitude. perform a portrait. In this case, the frequency difference polarity detector 7 is the frequency difference polarity detector 7 of Frequency Comparison No.
A counter that counts signals with a frequency n-fI (n = natural number), a latch circuit that latches at least 2 bits of the counter according to the pulse f0 signal, and a transition of the latch output signal of the latch circuit that is identified as described above. A transition identification circuit that detects the polarity of the frequency difference between frequency f and frequency f, and a complete circuit that detects the beat of the analog 2-chest wave that is used to determine whether it is positive or negative. There are many ways to do this, but in either case, the circuit scale is the phase comparator 3bi shown in FIG. 1, and the circuit scale of the up/down counter 8 and the DA converter 9 is much smaller than that of a 1/400 frequency division counter. Therefore, the frequency synchronous control frequency modulator of the present invention has a considerably smaller sea path scale than the conventional frequency modulator using a 1/N frequency division counter.

(f) Effects of the Invention As explained in detail above, according to the present invention, when a high frequency frequency synchronous control chest frequency IP device is used for wideband audio transmission,
Has the effect of reducing the circuit scale0

[Brief explanation of drawings]

FIG. 1 is a block diagram of a frequency synchronization control frequency modulator according to the example #'i, and FIG. 2 is a block diagram of a frequency IWJ synchronization frequency modulator according to an embodiment of the present invention. In the figure, 1 is a reference frequency oscillator, 2 and 2' are 1/N frequency division counters, 3 is a phase comparator, and 4. 4' is loop hilta,
5F'i addition circuit, 6fi voltage adjustment @ oscillator, 7 is frequency difference polarity detector, 8 is up/down counter, 9 is D-A
Converter, ■ is the award word I6, the width of the t-boss.

Claims (1)

[Claims] In a frequency positioner that synchronizes the average frequency of a frequency-modulated wave with a reference 8 mantissa, an alternative method is to detect the polarity of the difference frequency between the cough reference frequency and the average frequency of the frequency-modulated wave and synchronize the frequencies. Frequency synchronous control frequency modulator.