JPH11284506A - Preference oscillation signal output circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reference oscillation signal output circuit which efficiently and easily obtains a signal whose frequency and phase are equal to an inputted reference oscillation signal, in a state in which an unwanted oscillation signal is not included. SOLUTION: This frequency base oscillation signal generation circuit 1 is provided with a crystal oscillator 4, which produces and outputs an oscillation signal 4a of a prescribed frequency, a distributor 5 which distributes the signal 4a and outputs it to a phase comparator 2, the comparator 2 which compares a frequency reference oscillation signal 1a inputted externally with the signal 4a, detects whether or not the phases of the two signals are deviated and outputs a detection result as a phase comparison signal 2a to a low-pass filter 3 and the filter 3 which eliminates an unwanted new synthesized part of a high frequency that is included in the signal 2a and outputs a frequency control signal 3a and is able to obtain an output signal 1b, whose frequency and phase coincide with the signal 1a and also with which an unwanted signal is not mixed by changing and outputting the frequency of the signal 4a to be outputted, based on the signal 3a by the oscillator 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference oscillation signal output circuit for outputting a reference oscillation signal, and more particularly, to a reference oscillation signal having the same frequency and phase as an input reference oscillation signal. And a reference oscillation signal output circuit that outputs an oscillation signal that does not include the unnecessary oscillation signal included in the reference oscillation signal.

[0002]

2. Description of the Related Art Conventionally, in order to extract a necessary signal from a signal in which an unnecessary signal such as noise generated at the time of signal transmission is mixed, an unnecessary oscillation signal removing circuit for removing an unnecessary oscillation signal has been used. This unnecessary oscillation signal removal circuit is used, for example, to remove an unnecessary oscillation signal mixed in a frequency reference oscillation signal which is a reference for the operation of the entire circuit, and is used to prevent unstable operation or malfunction of the circuit. Have been.

FIG. 5 is a block diagram showing a schematic configuration of a specific example of a conventional unnecessary oscillation signal removing circuit.
The unnecessary oscillation signal removing circuit 100 shown in FIG. 5 removes the unnecessary oscillation signal included in the frequency reference oscillation signal 1a by using the n MHz (megahertz) frequency reference oscillation signal 1a.
Is input to a band-pass filter 11 that passes only a signal in a frequency band including n MHz to obtain an output oscillation signal 1b from which unnecessary oscillation signals have been removed.

FIG. 6 is a block diagram showing a schematic configuration of a specific example of a conventional frequency reference oscillation signal switching circuit.
The frequency reference oscillation signal switching circuit 200 shown in FIG.
A switching circuit 6 for switching between a frequency reference oscillation signal 1a and a reference oscillation signal generated by the crystal oscillator 4 is provided, and switches and outputs two types of reference oscillation signals. This frequency reference oscillation signal switching circuit 200
Is similar to the unnecessary oscillation signal removing circuit 100 shown in FIG.
The provision of the band-pass filter 11 allows the output oscillation signal 1b to be obtained in which unnecessary oscillation signals are not mixed as much as possible.

[0005]

However, when the band-pass filter 11 is used to remove the unnecessary oscillation signal, as in the unnecessary oscillation signal removing circuit 100 and the frequency reference oscillation signal switching circuit 200, the unnecessary oscillation signal is eliminated. Is included in the pass band of the band-pass filter,
It was necessary to narrow the pass band of the band-pass filter. However, there is a problem that the range in which the pass band can be narrowed is limited, and it is difficult to realize a band pass filter having a pass band ratio of about 0.001% or less. For this reason, when the frequency of the required oscillation signal and the frequency of the unnecessary oscillation signal are close to each other, it is difficult to efficiently remove the unnecessary oscillation signal by the band-pass filter 11.

The present invention has been made to solve the above problems,
Provided is a reference oscillation signal output circuit that can efficiently and easily obtain a signal having the same frequency and phase as the input reference oscillation signal without including the unnecessary oscillation signal, regardless of the frequency of the mixed unnecessary oscillation signal. The purpose is to do.

[0007]

According to a first aspect of the present invention, when a reference oscillation signal including an unnecessary oscillation signal is input, the reference oscillation signal has the same frequency and phase as the reference oscillation signal. A reference oscillation signal output circuit that outputs an oscillation signal that does not include the unnecessary oscillation signal; an oscillation unit that generates an oscillation signal of a predetermined frequency; an oscillation signal generated by the oscillation unit; A phase detection means for detecting a phase difference from the reference oscillation signal and outputting a phase detection signal; and a filter for passing only a signal in a predetermined frequency band among the phase detection signals output from the phase detection means. And oscillation frequency control means for variably controlling the frequency of the oscillation signal generated by the oscillation means based on the signal passed through the filter. There.

According to the first aspect of the present invention, when a reference oscillation signal including an unnecessary oscillation signal is input, an oscillation having the same frequency and phase as the reference oscillation signal and including no unnecessary oscillation signal is provided. In a reference oscillation signal output circuit that outputs a signal, an oscillation signal is generated by an oscillation unit at a predetermined frequency, and a phase difference between the oscillation signal and a reference oscillation signal input from the outside is detected by a phase detection unit. A phase detection signal is output, and only a signal in a predetermined frequency band among the phase detection signals is passed through a filter. Based on the signal passed through the filter, an oscillation generated by the oscillation unit by the oscillation frequency control unit is performed. Variable control of the signal frequency.

Therefore, a signal having the same frequency and phase as the input reference oscillation signal is newly generated and output by the oscillating means. Therefore, a band-pass filter for removing an unnecessary oscillation signal from the input reference oscillation signal is provided. Without
It is possible to obtain a signal that does not include an unnecessary oscillation signal.
This makes it possible to efficiently and easily obtain a signal having a desired frequency and phase without including an unnecessary oscillation signal.

According to a second aspect of the present invention, in the reference oscillation signal output circuit according to the first aspect, the voltage supply means for supplying a preset voltage and the oscillation frequency control means are provided from the voltage supply means. Switching means for switching between input of the supplied voltage or input of the phase detection signal output from the phase detection means is further provided.

According to the second aspect of the present invention, the voltage supply means supplies a preset voltage, and the switching means inputs the voltage supplied from the voltage supply means to the oscillation frequency control means. Or whether to input the phase detection signal output from the phase detection means.

Therefore, it is possible to arbitrarily switch any one of a signal having the same frequency and phase as the reference oscillation signal and a signal having a preset frequency, and to exclude these signals from unnecessary oscillation signals. Can be obtained in a state. Further, as compared with the case where a circuit for generating a signal of a preset frequency and the reference oscillation signal output circuit according to claim 1 or 2 are separately provided, only one oscillating means is required, so that the cost is reduced. This can be realized by a simple circuit configuration, and a reference oscillation signal that does not include an unnecessary oscillation signal can be easily obtained.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments to which the present invention is applied will be described below with reference to FIGS.

(First Embodiment) FIG. 1 is a block diagram showing a schematic configuration of a frequency reference oscillation signal generation circuit according to a first embodiment of the present invention.

As shown in FIG. 1, a frequency reference oscillation signal generating circuit 1 is composed of a phase comparator 2, a low-pass filter 3, a crystal oscillator 4 and a distributor 5, and a frequency reference oscillation signal from outside the circuit. It has an input terminal for inputting 1a and an output terminal for outputting an output signal 1b to the outside of the circuit. Parts having the same configurations as those of the conventional unnecessary oscillation signal removing circuit 100 and the frequency reference oscillation signal switching circuit 200 shown in FIGS. 5 and 6 are denoted by the same reference numerals.

The phase comparator 2 is connected between an input terminal to which the frequency reference oscillation signal 1a is input from the outside of the frequency reference oscillation signal generation circuit 1 and the low-pass filter 3, and further includes a distributor described later. 5 output terminal.
When the frequency reference oscillation signal 1a is input from outside the frequency reference oscillation signal generation circuit 1 and the oscillation signal 5a is input from the distributor 5, these two signals are compared to detect a difference in frequency and phase, and the comparison is performed. The phase comparison signal 2 a indicating the result is output to the low-pass filter 3.

FIG. 2 is a timing chart showing an example of comparison between the frequency reference oscillation signal 1a and the oscillation signal 5a executed in the phase comparator 2. In the figure,
(A) shows an oscillation signal 5a compared to the frequency reference oscillation signal 1a.
(B) shows a state in which the phase of the oscillation signal 5a is advanced as compared with the frequency reference oscillation signal 1a. 2 (a) and 2 (b), (1) shows the state of the frequency reference oscillation signal 1a, (2) shows the state of the oscillation signal 5a, and (3) shows the output D. (4) shows the state of the output signal.
Shows the state of the signal output as.

As shown in FIG. 2A, when the frequency reference oscillation signal 1a is at the "Hi" level and the oscillation signal 5a is at the "Lo" level, the output U is output as the "Hi" level. . Therefore, when the phase of the oscillation signal 5a is delayed compared to the frequency reference oscillation signal 1a, a pulse of the "Hi" level of the output U is output by the delay, and the output D remains at the "Lo" level. is there.

As shown in FIG. 2B, when the frequency reference oscillation signal 1a is at the "Lo" level and the oscillation signal 5a is at the "Hi" level, the output D is at the "Hi" level. Is output as Therefore, the frequency reference oscillation signal 1a
When the phase of the oscillation signal 5a is advanced as compared with the above, the pulse of the output D at the "Hi" level is output as much as the phase is advanced, and the output U remains at the "Lo" level. Then, the phase comparison signal 2 a is output to the low-pass filter 3 by passing the output D and output U pulses through a differential amplifier (not shown). A differential amplifier (not shown)
May be installed independently of the phase comparator 2 and the low-pass filter 3, or may be provided integrally in the low-pass filter 3.

The low-pass filter 3 is connected between the phase comparator 2 and the crystal oscillator 4, and cuts off a signal having a frequency higher than a predetermined frequency and allows only a signal having a low frequency to pass. The frequency control signal 3a is generated by removing high-frequency components from the components of the phase comparison signal 2a input from the phase comparator 2 and generating the frequency control signal 3a.
Is output to the crystal oscillator 4. As described above, the phase comparison signal 2a input from the phase comparator 2 is a pulse signal output according to a phase shift. However, when the frequency reference oscillation signal 1a includes a large number of unnecessary oscillation signals, the phase comparison signal 2a also includes the unnecessary oscillation signal included in the frequency reference oscillation signal 1a.
Also, due to the influence of other noises included in the frequency reference oscillation signal 1a, the phase comparison signal 2a may include an unnecessary oscillation signal. Therefore, by providing the low-pass filter 3, these unnecessary oscillation signals can be removed. Also, the cut-off frequency of the low-pass filter 3 is
By setting the pass band width lower than the pass band width of the band pass filter used in the above-described conventional technique, it is possible to remove unnecessary oscillation signals in the vicinity of unnecessary oscillation signals. The pass band can be narrowed more easily than the band pass filter.

The crystal oscillator 4 is an oscillator connected between the low-pass filter 3 and the distributor 5, and includes a crystal oscillator,
It has a variable capacitance diode, a capacitor, a transistor and the like. The crystal oscillator 4 includes a low-pass filter 3
It is possible to change the frequency of the signal oscillated by the oscillator by the function of the variable capacitance diode and the capacitor provided inside based on the frequency control signal 3a input from the oscillator. Therefore, the crystal oscillator 4 outputs an oscillation signal 4 a whose frequency changes based on the frequency control signal 3 a to the distributor 5.

FIG. 3 is a block diagram showing the internal configuration of the crystal oscillator 4. As shown in FIG.
Resistance 41, 46, 47, 51, variable capacitance diode 4
2. Capacitors 43, 48, and 49, a coil 44, a transistor 50, and a crystal oscillator 45 are provided therein.
Nodes N1, N2, N3, N4, N5, N6, and N7, an input terminal T1 to which a frequency control signal 3a is input, an output terminal T2 to output an oscillation signal 4a, and a power supply terminal T3 to which a power supply voltage is applied. .

The resistor 41 has one end connected to the input terminal T1 and the other end connected to the node N1. The cathode terminal of the variable capacitance diode 42 is connected to the node N1, and the anode terminal of the variable capacitance diode 42 is grounded. The variable capacitance diode 42
In parallel, a capacitor 43 having one end connected to the node N2 and the other end grounded is connected.

One end of a coil 44 is connected to the node N2, and the other end of the coil 44 is connected to a quartz oscillator 45. The other end of the crystal unit 45 is connected to a node N3.
7 is connected to a node N4. Resistance 46
Is connected to a power supply terminal T3 via a node N7, and the other end of the resistor 47 is grounded.

A capacitor 49 is connected to the node N4. The other end of the capacitor 49 is connected to the node N5.
A capacitor 48 is connected between the capacitor and ground. The base electrode of the transistor 50 is connected to the node N4, and the collector electrode of the transistor 50 is connected to the node N7.
And the emitter electrode is connected to the node N6. The node N6 is connected to the node N5, the output terminal T2, and one end of the resistor 51, and the other end of the resistor 51 is grounded so as to be in parallel with the capacitor.

In the crystal oscillator 4 shown in FIG.
When the frequency control signal 3a is input to the input terminal T1, the frequency control signal 3a is transmitted to the nodes N1 and N2 via the resistor 41, and the reverse voltage applied to the variable capacitance diode 42 changes. , The capacitance between the terminals of the variable capacitance diode 42 changes. Along with this,
The sum of the capacitances of the capacitor 43 and the variable capacitance diode 42 changes, and the crystal oscillator 45 vibrates according to the sum of the capacitances on the input terminal T1 side and the fixed capacitance on the output terminal T2 side,
The voltage waveform generated by this oscillation is
The output signal is amplified by an amplifier circuit constituted by 0, capacitors 48 and 49, and a resistor 51, and output from an output terminal T2 as an oscillation signal 4a.

That is, the frequency of the crystal oscillator 45 provided in the crystal oscillator 4 changes according to the frequency control signal 3a input to the input terminal T1, so that the frequency of the oscillation signal 4a output from the output terminal T2 is changed. Is the frequency control signal 3
It changes according to a.

The distributor 5 distributes the oscillation signal 4a input from the crystal oscillator 4, outputs the oscillation signal 4a to the outside of the frequency reference oscillation signal generation circuit 1 as an output oscillation signal 1b, and outputs the oscillation signal 4a to the phase comparator 2. Output.

According to the frequency reference oscillation signal generation circuit 1, first, the frequency reference oscillation signal 1a is input to the phase comparator 2, and the oscillation signal 4a
Is generated, and the oscillation signal 4a is input to the phase comparator 2 via the distributor 5 as the oscillation signal 5a. Then, the frequency reference oscillation signal 1a and the oscillation signal 5a are compared in the phase comparator 2, and the phase comparison signal 2a indicating the result of the comparison is obtained.
Is output. The phase comparison signal 2a is applied to the low-pass filter 3.
Is input, the low-pass filter 3 outputs the phase comparison signal 2
A high-frequency component is removed from a to generate a frequency control signal 3 a, and this frequency control signal 3 a is output to the crystal oscillator 4.

The crystal oscillator 4 changes the frequency of the oscillation signal 4a based on the frequency control signal 3a input from the low-pass filter 3 and outputs the oscillation signal 4a.
The oscillation signal 4a is input to the phase comparator 2 via the distributor 5 as the oscillation signal 5a. And the phase comparator 2
, The oscillation signal 5a and the frequency reference oscillation signal 1a are compared again, and the result of the comparison is output as the phase comparison signal 2a. By repeating this operation, finally, the frequency and phase of the oscillation signal 4a (oscillation signal 5a) match. Thereby, the frequency and the phase are equal to the frequency reference oscillation signal 1a, and the frequency reference oscillation signal 1a
Oscillation signal 1 not including unnecessary oscillation signal included in
b can be obtained.

As described above, according to the frequency reference oscillation signal generation circuit 1 according to the first embodiment of the present invention, the oscillation signal 4a generated by the crystal oscillator 4 and the frequency reference oscillation signal 1a are compared by the phase comparator. 2, the frequency of the oscillation signal 4a is changed based on the phase comparison signal 2a indicating the comparison result, and the comparison is executed again in the phase comparator 2. Therefore, the frequency reference oscillation signal 1a is finally compared with the frequency reference oscillation signal 1a. And an output oscillation signal 1b having the same phase. Further, even if an unnecessary oscillation signal is included in the phase comparison signal 2a due to the influence of the unnecessary oscillation signal included in the frequency reference oscillation signal 1a, the high frequency component is removed by the low-pass filter 3, so that the output oscillation signal 1b is It is not affected by the unnecessary oscillation signal included in the frequency reference oscillation signal 1a.

(Second Embodiment) FIG. 4 is a block diagram showing a schematic configuration of a frequency reference oscillation signal switching circuit according to a second embodiment of the present invention. As shown in FIG. 4, the frequency reference oscillation signal switching circuit 10 includes a phase comparator 2, a switching circuit 6, a fixed voltage generator 7, a low-pass filter 3, a crystal oscillator 4, and a distributor 5. . That is, the frequency reference oscillation signal switching circuit 10 shown in FIG. 4 is a switching circuit between the phase comparator 2 and the low-pass filter 3 in the frequency reference oscillation signal generation circuit 1 according to the first embodiment. 6 and a fixed voltage generator 7 connected to the switching circuit 6. Portions having the same configuration as the frequency reference oscillation signal generation circuit 1 are denoted by the same reference numerals, and description thereof is omitted. I do.

The switching circuit 6 has three terminals inside, and each terminal is connected to the phase comparator 2, the fixed voltage generator 7, and the low-pass filter 3, respectively. The switching circuit 6 can switch the connection state of each terminal in accordance with a switching signal 10a input from the outside, whereby the phase comparator 2 and the low-pass filter 3 or the fixed voltage generator 7 And the low-pass filter 3 are connected to each other.

That is, when the switching signal 10a is input, the signal input to the low-pass filter 3 is a constant voltage generated by the fixed voltage generator 7 or the phase comparator 2 according to the switching signal 10a. Is switched from the phase comparison signal 2a input from the switch. When the phase comparison signal 2 a is input to the low-pass filter 3, the low-pass filter 3, the crystal oscillator 4, and the distributor 5 become the frequency reference oscillation signal generating circuit 1 according to the first embodiment.
And the output oscillation signal 10b is a signal having the same frequency and phase as the frequency reference oscillation signal 1a. When a constant voltage generated by the fixed voltage generator 7 is applied to the low-pass filter 3, the crystal oscillator 45 inside the crystal oscillator 4 vibrates at a predetermined frequency, and the output oscillation signal 10b is The signal has a predetermined frequency.
This predetermined frequency is variable by adjusting the voltage generated in the fixed voltage generator 7.

Therefore, according to the frequency reference oscillation signal switching circuit 10 shown in FIG.
A signal having the same frequency and phase as the frequency reference oscillation signal 1a can be obtained. Further, by switching the connection state of each terminal provided in the switching circuit 6 by the switching signal 10a, a signal of a predetermined frequency is output as the output oscillation signal 10b. It is possible to obtain Further, since the frequency reference oscillation signal switching circuit 10 uses the crystal oscillator 4 without newly providing a crystal oscillator for obtaining a signal of a predetermined frequency, the conventional frequency reference oscillation signal switching circuit shown in FIG. Compared to the case where the above-mentioned frequency reference oscillation signal generation circuit 1 is connected to the circuit 200, the number of components is small and the circuit 200 can be realized at low cost.

As described above, according to the second embodiment of the present invention, the switching circuit 6 switches between the input of the frequency reference oscillation signal 1a and the input of the constant voltage generated by the fixed voltage generator 7. And the switching circuit 6
(Or a constant voltage) is input to the low-pass filter 3, so that the output oscillation signal 10b is a signal having the same frequency and phase as the frequency reference oscillation signal 1a and from which the unnecessary oscillation signal has been removed. , And a signal of a predetermined frequency. The frequency reference oscillation signal switching circuit 10
Compared to a case where the switching circuit and the circuit for removing the unnecessary oscillation signal are separately connected, the present invention can be easily realized at low cost.

In the above embodiment, the frequency of the oscillation signal 4a is changed by variably controlling the frequency of the crystal oscillator 45 by the variable capacitance diode 42 and the capacitor 43 in the crystal oscillator 4. ,
The present invention is not limited to this, and may be configured to use a variable capacitance capacitor capable of changing the capacitance without using a variable capacitance diode. The switching circuit 6 switches between the voltage input from the fixed voltage generator 7 and the phase comparison signal 2a as a signal to be output to the low-pass filter 3, but four signals are provided inside the switching circuit 6. The above-mentioned terminals may be provided, and a plurality of fixed voltage generators 7 each set to a different voltage may be connected to these terminals, and other details of the configuration may deviate from the gist of the present invention. It can be changed as appropriate within a range that does not exist.

[0038]

According to the first aspect of the present invention, since the oscillating means newly generates and outputs a signal having the same frequency and phase as the input reference oscillation signal, there is no need for the input reference oscillation signal. A signal that does not include an unnecessary oscillation signal can be obtained without providing a band-pass filter that removes the oscillation signal. In addition, unnecessary signals such as noise very close to a required signal can be removed as compared with the case where a band-pass filter is used.

According to the second aspect of the present invention, it is possible to arbitrarily switch any one of a signal having the same frequency and phase as the reference oscillation signal and a signal having a preset frequency, and obtain these signals. A signal can be obtained without including an unnecessary oscillation signal. Further, as compared with the case where a circuit for generating a signal of a preset frequency and the reference oscillation signal output circuit according to claim 1 or 2 are separately provided, only one oscillating means is required, so that the cost is reduced. This can be realized by a simple circuit configuration, and a reference oscillation signal that does not include an unnecessary oscillation signal can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a frequency reference oscillation signal generation circuit according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing a state of comparison performed in the phase comparator of FIG. 1;

FIG. 3 is a circuit diagram showing an internal configuration of the crystal oscillator shown in FIG.

FIG. 4 is a block diagram illustrating a schematic configuration of a frequency reference oscillation signal switching circuit according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional unnecessary oscillation signal removing circuit.

FIG. 6 is a block diagram showing a configuration of a conventional frequency reference oscillation signal switching circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 frequency reference oscillation signal generation circuit 2 phase comparator 3 low-pass filter 4 crystal oscillator 41, 46, 47, 51 resistor 42 variable capacitance diode 43, 48, 49 capacitor 44 coil 45 oscillator 50 transistor 5 distributor 6 switching circuit 7 Fixed voltage generator 10 Frequency reference oscillation signal switching circuit

Claims (2)

[Claims] When a reference oscillation signal including an unnecessary oscillation signal is inputted, a reference oscillation signal output for outputting an oscillation signal having the same frequency and phase as the reference oscillation signal and not including the unnecessary oscillation signal is provided. An oscillating means for generating an oscillation signal of a predetermined frequency; detecting a phase difference between the oscillating signal generated by the oscillating means and the reference oscillation signal input from the outside; and outputting a phase detection signal. And a phase detection signal input from the phase detection means.
A filter that passes only a signal in a predetermined frequency band; and an oscillation frequency control unit that variably controls a frequency of an oscillation signal generated by the oscillation unit based on the signal that has passed through the filter. Characteristic reference oscillation signal output circuit. 2. A voltage supply means for supplying a preset voltage, and a voltage supplied from the voltage supply means is input to the oscillation frequency control means, or the voltage is output from the phase detection means. 2. The reference oscillation signal output circuit according to claim 1, further comprising switching means for switching whether to input the phase detection signal.