JP5044343B2 - Radio correction clock - Google Patents

Description

  The present invention relates to a radio-controlled timepiece capable of receiving a plurality of standard radio waves, and more particularly to a radio-controlled timepiece having a filter circuit.

  Currently, standard radio waves with time information are being sent out in countries such as Japan, the United States, and Germany. Radio correction clocks that correct timekeeping time have been put to practical use as a type of time receiver that receives these standard radio waves. Yes.

Standard radio waves are sent serially in binary code as time data from the cumulative number of days since January 1 to hours and minutes, with one frame being one minute. Specifically, the carrier wave is amplitude-modulated by one rectangular pulse per second, and “0”, “1”, etc. are expressed by the pulse width of the rectangular pulse. (Hereafter, this rectangular pulse is called a time code.)
Since the time information is represented by a combination of “0”, “1”, etc., the radio-controlled timepiece receives the standard radio wave and extracts the time code from it to obtain accurate time information. Can do.

  Standard radio waves have different time code pulse widths and carrier wave frequencies depending on the country. For example, standard radio waves in Japan have three types of time code pulse widths of 200 ms, 500 ms, and 800 ms, and two carrier frequencies of 40 kHz and 60 kHz are used. On the other hand, standard radio waves in Germany have three types of time code pulse widths of 100 ms, 200 ms, and 1000 ms, and the carrier frequency is 77.5 kHz.

A straight system is generally used for the reception circuit of the radio-controlled timepiece. The block diagram is shown in FIG. Reference numeral 1 denotes an antenna, 2 denotes a tuning unit, 3 denotes an amplifier circuit, 5 denotes a filter circuit, and 6 denotes a detection circuit.
Tuning is performed by the antenna 1 and the tuning unit 2, and a standard radio wave is received. The received standard radio wave is amplified by the amplifier circuit 3, and only the necessary frequency component is passed by the filter circuit 5, and then the envelope is extracted by the detector circuit 6 to obtain a time code.
In order to obtain high reception sensitivity, the filter circuit 5 is required to have a high Q value. Therefore, a so-called crystal filter circuit using a crystal resonator is used for the filter circuit 5.
The Q value represents a state of vibration and is known as a value indicating a resonance peak. The higher the Q value, the sharper the peak.

The straight receiving circuit can receive standard radio waves with a simple configuration. However, when a crystal filter circuit is used for the filter circuit 5, a high Q value can be obtained, but standard radio waves having a plurality of frequencies can be received. Is unsuitable.
This is because the frequency that the crystal filter circuit passes is determined to be one by the characteristics of the crystal resonator to be used. Therefore, when using for a plurality of frequencies, the same number of crystal resonators are used. This is necessary.
That is, in order to receive standard radio waves having a plurality of frequencies, it is necessary to install as many crystal resonators as the number of the frequencies, resulting in an increase in circuit scale.

Therefore, the superheterodyne method is used as a method for efficiently receiving standard radio waves having a plurality of frequencies. The superheterodyne system is a system that converts signals of multiple frequencies into the same frequency and handles them by performing frequency conversion using a mixing circuit.
Various techniques have been devised (for example, see Patent Document 1).

  Here, the prior art shown in Patent Document 1 will be described with reference to FIG. FIG. 10 is a diagram obtained by simplifying the prior art disclosed in Patent Document 1 within a range in which the gist of the related art does not change so that it can be easily explained. Reference numeral 4 denotes a mixing circuit, 7 denotes a control unit, and 8 denotes a local oscillation circuit. The same numbers are assigned to the configurations already described.

  The receiving circuit shown in FIG. 10 receives standard radio waves having two different frequencies (frequency f1 or f2). The control unit 7 outputs a channel selection command signal to the tuning unit 2 according to the frequency of the received standard radio wave. The tuning unit 2 sets a tuning frequency according to the input channel selection command signal. In this way, the antenna 1 and the tuning unit 2 receive standard radio waves having a plurality of frequencies.

The amplifier circuit 3 amplifies the received signal and outputs it to the mixing circuit 4. The mixing circuit 4 mixes the signal input from the amplifier circuit and the signal input from the local oscillation circuit 8, and outputs a signal having a frequency corresponding to the sum and difference of those frequencies. One of these components is used as a signal, but according to the prior art shown in Patent Document 1, by setting the oscillation frequency f0 of the local oscillation circuit 8 to (f1 + f2) / 2, A signal having a constant intermediate frequency can be output regardless of the frequency to be received. (Hereinafter, the intermediate frequency is represented by fi, and the signal of frequency fi is called the intermediate frequency signal.)
After that, only the necessary frequency components are passed through the filter circuit 5, and then the envelope is extracted by the detection circuit 6 to obtain a time code.

Thus, by performing frequency conversion using the mixing circuit 4 and converting signals of a plurality of frequencies into substantially equal frequencies, one filter circuit 5 can be used for standard radio waves of all frequencies. it can. Of course, a crystal filter circuit may be used for the filter circuit 5, and even in that case, a plurality of crystal resonators are not necessary.
Such a configuration has a great merit in the super-heterodyne method particularly in the reception circuit of a high-sensitivity radio-controlled timepiece in terms of simplifying the circuit and reducing the number of external parts.

Japanese Unexamined Patent Publication No. 2004-80073 (Section 5, FIG. 2)

The conventional technique shown in Patent Document 1 can obtain a high Q-value filter with a single crystal resonator even when a standard radio wave having a plurality of frequencies is received by using a crystal filter circuit for the filter circuit 5. Although a high signal-to-noise ratio can be realized, it has been found that the reception sensitivity varies depending on the received time code.
That is, when the pass bandwidth of the filter circuit is not sufficiently wide with respect to the frequency bandwidth of the input signal, the spectral components necessary for reception are cut off, and the detection waveform that is the envelope of the carrier wave is extracted. This is because the envelope is rounded.

Here, the reason why the envelope is rounded will be described.
FIG. 11 schematically shows a time code spectrum 61, a standard radio wave spectrum in which a carrier wave is amplitude-modulated by the time code, and a spectrum 63 of an intermediate frequency signal. In the figure, the horizontal axis represents frequency and the vertical axis represents power.
The carrier wave frequencies are, for example, 40 kHz and 60 kHz. If the frequencies are fc, the spectrum of the standard radio wave has the same spectrum shape as the time code spectrum, centered on fc.

When the frequency conversion is performed by the mixing circuit 4, the center frequency of the spectrum changes, but the spectrum shape does not change. Therefore, the spectrum of the intermediate frequency signal has the same spectrum shape as that of the time code spectrum, centering on the intermediate frequency fi.
A time code can be obtained by extracting an envelope from an intermediate frequency signal having such a spectral shape by a detection circuit or the like. Considering the frequency axis, this operation corresponds to an operation for returning the center frequency to 0 Hz without changing the shape of the spectrum of the standard radio wave. By this operation, the intermediate frequency signal has the same spectrum as the original time code, and the waveform thereof is naturally the same waveform as the time code.
However, if a filter circuit having a high Q value is passed to improve the S / N ratio, the spectrum shape of the intermediate frequency signal shown in FIG. 11 will change. That is, even the frequency component of the intermediate frequency signal that is originally required for reception is removed. Even if the center frequency of the spectrum is returned to 0 Hz by a detection circuit or the like, the spectrum shape is different from the spectrum shape of the original time code, and the waveform at that time is also different from the original time code.

  As a result, since the restored time code has a higher frequency component mainly removed than the original time code, the waveform has rounded corners and becomes distorted.

  That is, in order to increase the S / N ratio, it is better that the Q value of the filter circuit is high. However, if the Q value of the filter circuit is too high, the response of the circuit deteriorates and the time code is lost. The SN ratio and responsiveness are in a trade-off relationship.

In general, in a radio timepiece, a time code is obtained by shaping a detected waveform with a comparator. As described above, the time information is obtained by reading the pulse width of the time code. However, if the detected waveform is lost, the pulse width of the time code is changed, and the reception sensitivity is deteriorated. That is, there is a best Q value with the highest reception sensitivity due to the relationship between the SN ratio and the responsiveness.
The best Q value depends on the bandwidth of the received signal, that is, the time code. When a time code with a narrow pulse width is received, a wider pass bandwidth is required for the filter circuit than when a time code with a wide pulse width is received. The Q value with the highest reception sensitivity differs depending on the time code.

  However, in the prior art shown in Patent Document 1, the Q value of the filter circuit 5 is constant regardless of the time code to be received. Therefore, when a certain time code is received, the Q value is too high. When another time code is received, the Q value is too low, resulting in a decrease in reception sensitivity.

  The present invention solves the above-mentioned problems, and the object is to optimize the Q value of the filter circuit according to the received time code in an environment where a plurality of time codes are received by the same radio-controlled timepiece. The present invention is to provide a radio-controlled timepiece that can realize high reception sensitivity even when receiving any standard radio wave by switching to a different value.

  In order to solve the above problems, the radio-controlled timepiece of the present invention employs the following configuration.

An antenna for receiving radio signals,
Tuning unit to tune the radio signal, the control unit sends a tuning command signal for setting the tuning data of the tuning unit, a filter circuit for extracting a predetermined signal pass band from the radio wave signal, detecting for detecting a signal extracted by the filter circuit circuit, a receiving circuit for receiving a plurality of standard radio waves consisting of,
In the radio-controlled watch with
The filter circuit can change the Q value, and changes the Q value of the filter circuit according to the type of the pulse width of the time code to be received by a selection command signal from the control unit .

The receiving circuit is configured by a superheterodyne system.

The filter circuit is characterized in that the amplification factor is substantially equal even in each signal passband.

  A reference oscillator, a local oscillation circuit that oscillates using the output frequency of the reference oscillator as an oscillation output reference frequency, and a mixing circuit that mixes the local oscillation frequency generated by the local oscillation circuit and a radio signal, The center frequency of the signal passband is substantially the same as the intermediate frequency created by the mixing circuit.

  The plurality of signal passbands included in the filter circuit are characterized in that their center frequencies are substantially equal.

  It has an external input means, and a control part outputs a channel selection command signal based on information from an external input means.

The filter circuit used in the radio-controlled timepiece of the present invention has a plurality of components for creating a plurality of signal pass bands and a switching means for switching the connection between these components.
With such a configuration, when receiving a plurality of standard radio waves, it is possible to obtain an optimum Q value corresponding to the time code, and it is possible to obtain good reception sensitivity in any time code.

  Hereinafter, embodiments of the radio-controlled timepiece of the present invention will be described with reference to the drawings. In the embodiment of the present invention, the operation of converting the received time code into time information will be described using a microcomputer as an example. In the following description, the same constituent elements are denoted by the same reference numerals, and the description thereof is omitted or simplified.

[Description of Overall Configuration: FIGS. 1 to 7]
A first embodiment of the radio-controlled timepiece of the present invention will be described with reference to FIGS. First, FIG. 1 shows a block diagram of a radio-controlled timepiece according to the present invention. Reference numeral 1 denotes an antenna, 11 denotes a receiving circuit, 12 denotes a microcomputer, and 13 denotes a time display unit.
The standard radio wave is received by the antenna 1 and the receiving circuit 11, and a time code is obtained. Then, the microcomputer 12 converts the time code into time information and controls the time display unit 13 to display an accurate time.
The radio-controlled timepiece of the present invention will be described on the assumption that it receives two types of standard radio waves, 60 kHz which is a Japanese standard radio wave and 77.5 kHz which is a German standard radio wave.

[Overall description of receiving circuit: FIG. 2]
FIG. 2 is a block diagram for explaining the inside of the receiving circuit 11 shown in FIG. 1 and its connection. In FIG. 2, 2 is a tuning unit, 3 is an amplifier circuit, 4 is a mixing circuit, 5 is a filter circuit, 6 is a detection circuit, 7 is a control unit, and 8 is a local oscillation circuit. Reference numeral 9 denotes a switch.
Tuning is performed by the antenna 1 and the tuning unit 2, and a standard radio wave is received. Then, the standard radio wave received by the antenna is amplified by the amplifier circuit 3 and output to the mixing circuit 4. The mixing circuit 4 mixes the signal from the amplifier circuit 3 and the signal input from the local oscillation circuit 8 and outputs the mixed signal to the filter circuit 5. After passing only the necessary frequency components in the filter circuit 5, the detection circuit 6 extracts the envelope, restores the time code superimposed on the carrier wave, and outputs the restored time code to the microcomputer 12. The microcomputer 12 extracts time information from the time code input from the receiving IC and controls the time display unit 13.

In order to obtain high reception sensitivity, the filter circuit 5 is required to have a high Q value. Therefore, a so-called crystal filter circuit using a crystal resonator is used for the filter circuit 5.
The switch 9 is a receiving station changing means by an external operation, and normally outputs “L” level. Only when the switch is inserted, an “H” level signal is output to the control unit 7. Here, the “H” level and the “L” level of the signal respectively represent a state where the voltage level of the signal line is high and a state where it is low.

  The control unit 7 outputs a channel selection command signal to the tuning unit 2, the filter circuit 5, and the local oscillation circuit 8 according to the frequency of the received standard radio wave. The channel selection command signal is at the “H” level when receiving a Japanese standard radio wave, and at the “L” level when receiving a German standard radio wave.

When the “L” level signal is input from the switch 9, the same signal as the previous reception is output as the channel selection command signal, and when the “H” level signal is input from the switch 9 The signal opposite to the previous reception is output as a channel selection command signal.
For example, if the Japanese standard radio wave was received last time, if the signal from the switch 9 is “L” level, the same “H” level as the previous time is output, and the signal from the switch 9 is “H” level. “L” level is output.

[Description of tuning unit: FIGS. 2 and 3]
The tuning unit 2 performs tuning with the antenna 1 in accordance with a channel selection command signal. A circuit example of the tuning unit 2 is shown in FIG. In FIG. 3, 21 and 22 are capacitive elements, 23 and 24 are switches, and 10 is ground (GND level, for example, 0 V).
Capacitance elements 21 and 22 have capacitance values set so as to resonate with antenna 1 at 60 kHz which is a Japanese standard radio wave and at 77.5 kHz which is a German standard radio wave.
When an “H” level channel selection command signal is received, the standard radio wave of 60 kHz is received by closing the switch 23 and opening the switch 24. When receiving a channel selection command signal of “L” level, the standard radio wave of 77.5 kHz is received by opening the switch 23 and closing the switch 24.
In this way, a standard radio wave having a predetermined frequency is received by inputting a tuning command signal to the tuning unit 2.

The mixing circuit 4 mixes the signal input from the amplifier circuit 3 and the signal input from the local oscillation circuit 8, and outputs a signal having a component corresponding to the sum and difference thereof. One of these components is used as a signal, but here, the difference component is used.
At this time, the frequency of the signal output from the local oscillation circuit 8 is set according to the channel selection command signal input from the control unit 7. That is, when a “H” level channel selection command signal is input, a signal having a frequency of 60 kHz + Δf is output, and when an “L” level channel selection command signal is input, a frequency of 77.5 kHz + Δf is output. Output a signal.
As a result, a signal having a constant frequency Δf is output from the mixing circuit 4 to the filter circuit 5 regardless of the frequency of the received standard radio wave.

[Description of Filter Circuit: FIGS. 2, 4, 5, and 6]
The filter circuit 5 removes unnecessary frequency components and outputs only the necessary frequency components to the detection circuit 6. A circuit example of the filter circuit 5 is shown in FIG. In FIG. 4, 51 is a crystal resonator, 5
Reference numeral 2 denotes a resistance element for Q value attenuation, which is called a damping resistance. 53 is a feedback resistor, and 54 is an operational amplifier. 55 denotes a Q-value adjusting resistor, 56 denotes an amplification factor adjusting resistor, and 57 and 58 denote switches. In the operational amplifier 54, 541 indicates a positive input terminal (hereinafter referred to as INP), and 542 indicates a negative input terminal (hereinafter referred to as INN).

The filter circuit 5 has a plurality of components for creating a plurality of signal pass bands. Moreover, it has the switching means which switches those components. In the example of the filter circuit 5 shown in FIG. 4, the damping resistor 52, the Q value adjusting resistor 55, the feedback resistor 53, and the amplification factor adjusting resistor 56 are a plurality of components for creating a signal pass band.
As a switching means for switching whether or not the damping resistor 52 and the Q value adjusting resistor 55 are connected in parallel, a switch 57 is provided, and switching for switching whether or not the feedback resistor 53 and the amplification factor adjusting resistor 56 are connected in parallel. As a means, a switch 58 is provided.

FIG. 5 shows an equivalent circuit of the crystal unit 51. Reference numeral 511 denotes an equivalent series resistance, 512 denotes an equivalent series capacitance, 513 denotes an equivalent series inductance, and 514 denotes an electrode capacitance.
The equivalent series resistance 511, the equivalent series capacitance 512, and the equivalent series inductance 513 are connected in series, and the electrode capacitance 514 is connected in parallel with this.

  FIG. 6 is a diagram schematically showing the equivalent inductance characteristics of the crystal unit 51. In FIG. 6, the horizontal axis indicates the frequency, and the vertical axis indicates the equivalent inductance of the crystal unit 51. The equivalent inductance of the crystal unit 51 becomes zero at the series resonance point of the equivalent series capacitance 512 and the equivalent series inductance 513, and the frequency at that time is expressed as fr. The impedance at both ends of the crystal resonator 51 at the frequency fr is substantially equal to the value of the equivalent series resistance 511.

  At a frequency higher than the frequency fr, the equivalent series inductance 513 is dominant in the series combined inductance of the equivalent series capacitance 512 and the equivalent series inductance 513 and becomes inductive. The equivalent inductance of the crystal unit 51 becomes infinite at the parallel resonance point between the series combined inductance and the electrode capacitance 514. The frequency at that time is represented as fa.

  At a frequency higher than the frequency fa, the electrode capacitance 514 is dominant, and the equivalent inductance of the crystal unit 51 is capacitive.

  That is, the crystal unit 51 has singular points at the frequency fr and the frequency fa, but the frequency fa is easily affected by parasitic capacitance generated during mounting or wiring. Therefore, in the present embodiment, the characteristic of the frequency fr is used.

[Description of operation: Fig. 7]
First, the operation when receiving a German standard radio wave will be described. When receiving a German standard radio wave, an "L" level channel selection command signal is input from the control unit 7, and the switch 57 and the switch 58 are opened.
Since the operational amplifier 54 has a very high input impedance and a very large amplification factor, no current flows into the operational amplifier 54 and operates so that the potentials of INP and INN are substantially constant. . For this reason, INN becomes the ground potential.

When the current flowing through the crystal resonator 51 and the damping resistor 52 is I1, the equivalent impedance of the crystal resonator 51 is Zc, and the resistance value of the damping resistor 52 is Rd, the current I1 can be expressed by the following equation.
I1 = Vin / (Zc + Rd)

Since no current flows into the operational amplifier 54, all of the current flowing through the crystal resonator 51 and the damping resistor 52 flows to the feedback resistor 53. Therefore, if the resistance value of the feedback resistor 53 is Rf, the voltage generated in the feedback resistor 53 is Rf * I1.
As a result, the output voltage of the operational amplifier 54 can be expressed by the following equation.
− (Rf / (Zc + Rd)) Vin

  That is, the amplification factor of the operational amplifier 54 shown in FIG. 4 is given by −Rf / (Zc + Rd). Here, the sign is negative because it indicates that the phase of the output voltage is 180 ° behind the phase of the input voltage.

Since the equivalent inductance of the crystal unit 51 is as shown in FIG. 6, the amplification factor frequency characteristic of the operational amplifier 54 shown in FIG. 4 is as shown in FIG. FIG. 7 schematically shows the amplification factor frequency characteristic of the operational amplifier 54. In FIG. 7, the horizontal axis indicates the frequency, and the vertical axis indicates the amplification factor of the operational amplifier 54.
The amplification factor takes the maximum value at the frequency fr of the series resonance point between the equivalent series capacitance 512 and the equivalent series inductance 513, and the resistance value of the equivalent series resistance 511 is R1, the amplification factor at that time is expressed by the following equation: Can do.
Rf / (R1 + Rd)
Since the frequency fr is determined only by the characteristics of the crystal unit 51, it is possible to obtain very accurate filter characteristics.
Further, the amplification factor is minimum at the frequency fa, but since this frequency is sufficiently separated from the frequency of the standard radio wave, the influence is small.

At this time, when the Q value of the filter circuit 5 is QDCF77 and the inductance value of the equivalent series inductance 513 is L1, QDCF77 can be expressed by the following equation.
QDCF77 = (2πf0 * L1) / (R1 + Rd)
The Q value in the absence of the damping resistor 52 is determined by the characteristics of the crystal resonator 51, and the value is a very large value. By inserting a damping resistor 52 having an appropriate resistance value therein, an optimum Q value for receiving a standard German radio wave can be obtained.

If the amplification factor of the operational amplifier 54 is ADCF77, ADCF77 can be expressed by the following equation.
ADCF77 = Rf / (R1 + Rd)
That is, by adjusting the resistance value of the feedback resistor 53, the gain of the filter circuit can be adjusted independently of the Q value of the filter circuit.

Next, the case of receiving Japanese standard radio waves will be described. When receiving a Japanese standard radio wave, an “H” level channel selection command signal is input from the control unit 7. Accordingly, the switch 57 and the switch 58 are closed, and a Q value adjusting resistor 55 is inserted in parallel with the damping resistor 52, and an amplification factor adjusting resistor 56 is inserted in parallel with the feedback resistor 53, respectively.
At this time, when the Q value of the filter circuit 5 is QJJY and the parallel combined resistance value of the Q value adjusting resistor 55 and the damping resistor 52 is Ra, QJJY can be expressed by the following equation.
QJJY = (2πf0 * L1) / (R1 + Ra)
That is, by setting the resistance value of the Q value adjusting resistor 55 to an appropriate value, it is possible to obtain an optimum Q value for receiving Japanese standard radio waves.

When the amplification factor of the operational amplifier 54 when the switch 57 and the switch 58 are closed is AJJY, and the parallel combined resistance value of the amplification factor adjusting resistor 56 and the feedback resistor 53 is Rb, AJJY can be expressed by the following equation. it can.
AJJY = Rb / Ra
That is, by setting Rb, which is the resistance value of the amplification factor adjusting resistor 56, to an appropriate value, a state in which an “L” level channel selection command signal is input, that is, a case where a German standard radio wave is received. An equal amplification factor can be obtained.

  As described above, by switching the Q value of the filter circuit 5 to the optimum value in accordance with the time code to be received, good reception sensitivity can be obtained regardless of the time code.

  In the above description, the case where the standard radio wave of Japan and the standard radio wave of Germany are received has been described as an example. However, the present invention is not limited to this. What is important is that the Q value of the filter circuit 5 is changed to an optimum value corresponding to the received standard radio wave, and the type of the received standard radio wave is appropriately changed according to the specification of the radio wave correction watch of the present invention. It is what is done.

[Description of Overall Configuration: FIG. 8]
Next, a second embodiment of the radio-controlled timepiece of the invention will be described. In the second embodiment, a plurality of filter circuits are provided. This will be described with reference to FIG. In FIG. 8, reference numerals 30 and 40 denote filter circuits. Reference numerals 31 and 41 denote crystal oscillators, 32 and 42 denote damping resistors, 33 and 43 denote feedback resistors, and 34 and 44 denote operational amplifiers. 61 and 62 are switches.

In the filter circuit 30, a crystal resonator 31 and a damping resistor 32 are connected in series, and the damping resistor 32 is connected to the INN of the operational amplifier 34. The INP of the operational amplifier 34 is connected to the ground (GND level, for example, 0 V). A feedback resistor 33 is connected between the output terminal of the operational amplifier 34 and INN.
Since the configuration of the filter circuit 40 and the connection form of each configuration are the same as those of the filter circuit 30, description thereof will be omitted.

  The filter circuit 30 is a filter circuit used when receiving a Japanese standard radio wave of 60 kHz. The series resonance frequency of the crystal unit 31 is 60 kHz, and the damping resistance 32 has a relatively small value. It has become.

  The filter circuit 40 is a filter circuit used when receiving a German standard radio wave of 77.5 kHz. The series resonance frequency of the crystal unit 41 is 77.5 kHz, and the damping resistor 42 is a damping circuit. The value is larger than that of the resistor 32.

As described above, the filter circuit according to the second embodiment of the radio-controlled timepiece of the present invention is composed of two filter circuits, and the filter circuit 30 and the filter circuit 40 are used to create a plurality of signal pass bands. It has multiple components.
In addition, there are also switching means for switching these components, which are switches 61 and 62. In the example of the filter circuit shown in FIG. 8, it is provided as switching means for switching which one of the filter circuit 30 and the filter circuit 40 is used.

  The feedback resistor 33 and the feedback resistor 43 are set to values such that the amplification factor of the filter circuit 30 and the amplification factor of the filter circuit 40 are equal.

When the “H” level channel selection command signal is input, the switch 61 is closed and the switch 62 is opened. Thereby, the signal passes through the filter circuit 30.
When the “L” level channel selection command signal is input, the switch 62 is closed and the switch 61 is opened. As a result, the signal passes through the filter circuit 40.

  In this way, the Q value can be switched to an optimum value by switching between the filter circuit 30 and the filter circuit 40 constituting the filter circuit according to the received time code. For this reason, high receiving sensitivity can be obtained irrespective of the time code.

  The radio-controlled timepiece of the present invention can obtain an optimum Q value corresponding to the received time code by switching the Q value of the filter circuit. Therefore, it is suitable for a radio wave correction watch that receives a plurality of standard radio waves.

It is a block diagram for demonstrating the electromagnetic wave correction timepiece of this invention. It is a block diagram for demonstrating the receiving circuit in the electromagnetic wave correction timepiece of this invention. It is a circuit diagram for demonstrating the tuning part in the radio wave correction timepiece of the present invention. It is a circuit diagram for demonstrating the filter circuit in the radio wave correction timepiece of the present invention. It is an equivalent circuit diagram of a crystal resonator. It is a figure which shows typically the equivalent inductance characteristic of a crystal oscillator. It is a figure explaining the frequency characteristic of the filter circuit in the electric wave correction timepiece of the present invention. It is a circuit diagram explaining the different filter circuit in the radio wave correction timepiece of the present invention. It is a block diagram explaining a prior art. It is a block diagram explaining the prior art shown in patent document 1. FIG. It is the figure which showed the frequency spectrum of the standard radio wave typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Tuning part 3 Amplifying circuit 4 Mixing circuit 5 Filter circuit 6 Detection circuit 7 Control part 8 Local oscillation circuit 9 Switch 11 Receiving circuit 12 Microcomputer 13 Time display part 51 Crystal oscillator 52 Damping resistance 53 Feedback resistance 54 Operational amplifier 55 Q Value adjustment resistor 56 Gain adjustment resistors 57 and 58 are switches 541 Positive input terminal (INP)
542 Negative input terminal (INN)
61 Spectrum of time code 62 Spectrum of standard radio wave 63 Spectrum of intermediate frequency signal

Claims (6)

An antenna for receiving radio signals,
A tuning unit for tuning the radio signal,
Controller sends a tuning command signal for setting the tuning data of the tuning unit,
A filter circuit for extracting a predetermined signal passband from the radio signal;
A detection circuit for detecting the signal extracted by the filter circuit;
A receiving circuit for receiving a plurality of standard radio waves consisting of,
In the radio-controlled watch with
The filter circuit can change the Q value,
A radio-controlled timepiece , wherein the Q value of the filter circuit is changed according to the type of pulse width of a received time code in accordance with a selection command signal from the control unit . The radio wave correction timepiece according to claim 1, wherein the receiving circuit is configured by a superheterodyne system. 3. The radio-controlled timepiece according to claim 1, wherein the filter circuit has substantially the same amplification factor even in each signal pass band. A reference oscillator;
A local oscillation circuit that oscillates with an output frequency of the reference oscillator as an oscillation output reference frequency;
A mixing circuit for mixing the local frequency generated by the local oscillation circuit and the radio signal;
Have
The center frequency of the signal pass band of the filter circuit, radio-controlled timepiece according to any one of claims 1 to 3, characterized in that the substantially the same frequency as-made intermediate frequency in the mixing circuit.   The radio-controlled timepiece according to claim 4, wherein the plurality of signal passbands of the filter circuit have substantially the same center frequency. Having external input means,
6. The radio-controlled timepiece according to claim 1, wherein the control unit outputs the channel selection command signal based on information from the external input unit.

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