JP2737115B2 - Oscillation frequency non-adjustable oscillation circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillation frequency non-adjustable oscillation circuit whose oscillation frequency is not adjusted.

[Conventional technology]

FIG. 7 shows the configuration of a conventional oscillation circuit which requires adjustment of the oscillation frequency, wherein 1 is a voltage controlled oscillator (VCO) for controlling the output oscillation frequency f ₀ by the input voltage V _cont , and 2 is a voltage controlled oscillator 1 This is a variable voltage source that _{supplies the} voltage V _cont .

FIG. 8 shows the configuration of a conventional non-adjusted oscillation circuit, and 3 shows the output signal of the voltage controlled oscillator 1 as 1 / n (n is a positive integer, that is, n = 1, 2,...). Divided n divider, 4 is n
A phase comparator (PD) for detecting a phase difference between the output signal f ₀ / n of the frequency divider 3 and the reference signal f _ref and outputting a voltage V _err according to the phase difference, This is an adder for adding the reference voltage _Vref so as to be controllable by the output of the comparator 4.

Next, the operation will be described. First, in the oscillation circuit shown in FIG. 7 which requires adjustment, an arbitrary oscillation frequency f ₀ can be obtained from the output of the voltage controlled oscillator 1 by adjusting the output voltage V _cont of the variable voltage source 2.

Next, in the non-adjusted oscillation circuit of FIG.
The output signal f ₀ of the voltage controlled oscillator 1 is divided by the n frequency divider 3 into 1 / n
The phase comparator 4 outputs a voltage V _err corresponding to the phase difference between the frequency- _divided signal f ₀ / n and the reference signal f _ref , and the adder 5
, The reference voltage V _ref is added and input to the voltage controlled oscillator 1 as the variable voltage V _cont . As a result, the control is performed so that f ₀ / n and the reference frequency f _ref match, and f ₀ = n × f _ref , so that the oscillation frequency n times the reference signal can be oscillated without adjustment.

[Problems to be solved by the invention]

The conventional oscillation circuit is configured as described above.
In the case of the figure, it is necessary to adjust the oscillation frequency.
In the case shown in the figure, the oscillation frequency obtained without adjustment is limited to n times the frequency of the reference signal. To obtain an arbitrary oscillation frequency without adjustment, the frequency of the signal that requires the frequency of the reference signal is one time. / n, and it was not possible to obtain signals of several frequencies from a reference signal of an arbitrary frequency without adjustment.

The present invention has been made in order to solve the above-described problems, and has an oscillation frequency non-adjustable oscillation circuit capable of easily obtaining a signal of an arbitrary oscillation frequency from a reference signal of an arbitrary frequency without adjustment. The purpose is to gain.

[Means for solving the problem]

An oscillation frequency non-adjustment oscillation circuit according to the present invention has a voltage-controlled oscillator that receives a variable voltage signal as an input and generates an output signal having a frequency corresponding to the voltage of the input signal. A first frequency-to-voltage converter to generate, a device for multiplying or dividing the frequency of the reference signal to generate two sub-reference signals of different frequencies, and a voltage signal corresponding to the frequency of each of the above-mentioned sub-reference signals. Output second and third frequency-to-voltage converters,
And the output of the third frequency-to-voltage converter are combined to produce a divided voltage output, and the output of the first frequency-to-voltage converter is compared with the output of this voltage divider as a reference voltage. And a comparator which uses a voltage signal corresponding to the difference as an input signal of the voltage control transmitter.

[Action]

In the present invention, while the output of the voltage controlled oscillator is converted into a voltage signal by the first frequency-voltage converter,
The frequency of the reference signal is doubled or divided to create two sub-reference signals of different frequencies, and the second and third frequency-to-voltage converters generate voltage signals corresponding to the frequency of each sub-reference signal. . A voltage divider that combines the outputs of the second and third frequency-to-voltage converters generates a divided voltage output that serves as a reference voltage, and generates a reference voltage and a voltage signal that is the output of the first frequency-to-voltage converter. Are compared by a comparator, and a voltage signal corresponding to the difference is input to the voltage-controlled oscillator, whereby the output of the voltage-controlled oscillator is controlled to an output corresponding to the reference voltage. Since the reference voltage can be set to an arbitrary value by changing the voltage dividing ratio of the voltage divider, the output of the voltage controlled oscillator can be set to an arbitrary frequency.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of an oscillation frequency non-adjusted oscillation circuit according to this embodiment. Reference numeral 6 denotes a multiplier or a frequency divider which multiplies or divides a reference signal _fref. is there. However, in the case of a multiplier, a is a positive integer and a = 1, 2,..., And in the case of a frequency divider, a is a positive integer. Becomes 7 is a multiplier or a frequency divider which multiplies or _{divides the} reference signal by _fref, and the multiple or frequency division number is b, and b = 1, 2,. It is. However, it is assumed that b> a. 8a to 8c are frequency-voltage converters (F-VCO) that output voltages corresponding to the input frequencies.
NV), the characteristics are the same, and an example is shown in FIG. 9 is the output voltage V of the frequency-voltage converters 8a and 8b
_a, by applying a V _b min, voltage divider to obtain a voltage corresponding to the frequency of the output signal, R _a, consists R _b, is output from the connection point It is. A comparator 10 compares the output of the voltage divider 9 with the output of the frequency-voltage converter 8c, and outputs the potential difference.

Next, the operation will be described. First, any reference signal
The Empire multiplier or divider 6 and 7 f _ref, is frequency-converted so as to sandwich any output frequency f ₀ to the desired. That is, it is assumed that the values of a and b are determined so that a × f _ref <f ₀ <b × f _ref . The sub-reference signals a × f _ref and b × f _ref thus frequency-converted are input to frequency-voltage converters 8a and 8b, respectively.
V _a and V _b are output. Relationship between the input frequency and the output voltage in this case is linear characteristics as shown in FIG. 2, a × f _ref
The linearity is sufficiently maintained from to b × f _ref . Voltage V _a, V _b is input to a voltage divider 9, the partial pressure ratio R _a;
Output voltage according to R _b Is output, but by appropriately selecting the division ratio, a voltage corresponding to an arbitrary frequency between the two sub-reference signals a × f _ref and b × f _ref can be obtained. On the other hand, the output signal f ₀ of the voltage controlled oscillator 1 is frequency - is input to the voltage converter 8c, the output voltage V ₀ corresponding to the frequency is outputted. Therefore, the frequency - the output of the output V ₀ voltage divider 9 of the voltage converter 8c _Are compared by a comparator 10, and the error voltage V _Err is added to a reference voltage V _ref by an adder 5 and input to the voltage controlled oscillator 1 as a variable voltage V _cont to control the output frequency. For this reason, the output voltage V ₀ of the frequency-voltage converter 8 c is equal to the output voltage of the voltage divider 9. Is controlled so that the output frequency f ₀ of the voltage controlled oscillator 1 is equal to the voltage Frequency corresponding to Becomes Therefore, the desired oscillation frequency f ₀ can be obtained without adjustment by appropriately determining a, b, R _a , and R _b from an arbitrary reference signal f _ref .

In the above embodiment, the frequency of the desired output signal is between the two sub-reference signals a × f _ref and b × f _ref (a × f _ref <f ₀ <b × f _ref ). Doubler or divider
6, 7 are set, but if the oscillation circuit is configured as shown in FIGS. 3 (a) and 4 (a), the frequency-voltage converter 8a
In the range where the linearity of ~ 8c is satisfied, the multiplier or the frequency divider 6,7 is always set to have the relationship as in the above embodiment.
There is no need to set. That is, in the case of FIG. 3A, the setting is made so that a × f _ref <b × f _ref <f ₀ as shown in FIG. 3B. Further, comparators 11 and 12 are inserted between the voltage divider 9 and the comparator 10, and the output of the comparator 11 is And the output of comparator 12 is So, Becomes In the case of FIG. 4 (a), as shown in FIG. 4 (b), f ₀ <a × f _ref <b × f _ref is set, and the voltage divider 9 and the comparator 10 And comparators 13 and 14 are inserted between them, and the output of the comparator 13 is And the output of comparator 14 is So, Becomes

In each of the above embodiments, the case where one reference signal is used has been described. However, two signals having different frequencies are used as the reference signal.
Even when f _ref1 and f _ref2 (f _ref1 <f _ref2 ) are given, the configuration shown in FIG. 5 provides the same effects as the above embodiments. That is, the reference signals f _ref1 and f _ref2 are input to the multiplier or the frequency dividers 6 and 7, respectively. Becomes In this example, the sub-reference signals a × f _ref1 and b × f
magnitude relationship between _ref2 and the output signal f ₀ good either case.

Further, in each of the above embodiments, the output signal is described as a single frequency signal. However, even when a video signal is modulated into an FM signal by a modulator like a VTR, a specified signal portion (in the case of a VTR, a synchronization signal If the output signal is subjected to frequency-to-voltage conversion only during the time of the front end portion, and the voltage is maintained during the other times, the adjustment of the oscillation frequency of the FM modulator can be eliminated. The configuration in this case is shown in FIG. In the figure, reference numeral 1a denotes an FM modulator, which is considered to be a kind of voltage controlled oscillator in that an output frequency corresponding to an input voltage is obtained. 15 is a clamp circuit for a constant DC potential of the distal end portion of the synchronization signal of the video signal, the DC potential V _ref
It is. Reference numeral 16 denotes a sample-and-hold circuit that holds the voltage at the leading end of the synchronization signal among the voltages obtained by converting the output signal f _out of the FM modulator 1a by the frequency-voltage converter 8c.
6 is operated by a clamp and sample hold pulse. C ₁ is a capacitor that removes the DC component of the video signal input to the clamp circuit 15 and holds the clamp voltage, and C ₂ is a capacitor that holds the voltage at the tip of the synchronization signal of the sample and hold circuit 16 and serves as a reference signal. A color carrier _fsc is used. The basic operation is the same as the above embodiments,
This embodiment is the same as the above embodiments except that the frequency-to-voltage conversion is performed only at the time of the leading end of the synchronizing signal of the video signal, and the voltage is maintained at other times.

〔The invention's effect〕

As described above, according to the present invention, the frequency of an arbitrary reference signal is multiplied or divided to generate two sub-reference signals of different frequencies, and a voltage corresponding to the frequency of each sub-reference signal is divided by a voltage divider. To generate a divided output as a reference voltage, and a signal corresponding to a difference signal between the reference voltage and a voltage signal corresponding to the output of the voltage controlled oscillator is used as an input of the voltage controlled oscillator. Therefore, it is possible to determine an oscillation frequency without being restricted by the reference signal, and to obtain an unadjusted oscillation circuit that can easily change the oscillation frequency only by changing the voltage division ratio.

[Brief description of the drawings]

FIGS. 1 and 2 are a circuit configuration diagram and a frequency-voltage conversion characteristic diagram according to a first embodiment of the present invention, and FIGS.
4B is a circuit diagram and a frequency-voltage conversion characteristic diagram according to a second embodiment of the present invention, and FIGS. 4A and 4B are a circuit diagram and frequency-voltage diagram according to a third embodiment of the present invention. FIG. 5 and FIG. 6 are circuit configuration diagrams according to the fourth and fifth embodiments of the present invention, and FIG. 7 and FIG. 8 are configuration diagrams of a conventional circuit. 1 ... voltage controlled oscillator, 1a ... FM modulator, 6,7 ... multiplier or frequency divider, 8a-8c ... frequency-voltage converter, 9 ...
... voltage divider, 10-14 ... comparator, 15 ... clamp circuit, 16
…… Sample hold circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A voltage controlled oscillator that receives a variable voltage signal as input and generates an output signal having a frequency corresponding to the voltage of the input signal, and a first signal that generates a voltage signal corresponding to the output signal of the voltage controlled oscillator. A frequency-to-voltage converter, a device that doubles or divides the frequency of the reference signal to generate two sub-reference signals of different frequencies, a second and a second device that respectively output voltage signals corresponding to the frequencies of the respective sub-reference signals Third frequency-
A voltage converter, a voltage divider that combines the outputs of the second and third frequency-to-voltage converters to generate a divided voltage output, and a variable voltage-dividing ratio; An oscillation frequency non-adjustable oscillation circuit comprising: a comparator that compares outputs of converters and uses a voltage signal corresponding to the difference as an input signal of the voltage-controlled oscillator.