JP4861773B2 - Long wave detection circuit and apparatus thereof - Google Patents

Description

  The present invention relates to a long wave detection circuit and a device thereof, and more particularly to a long wave detection circuit and a device for detecting a long wave reception state of a predetermined frequency.

  Today, so-called radio timepieces that calibrate time by periodically receiving standard radio waves are in widespread use. Radio clocks use long-wave (30 kHz to 300 kHz) radio waves because surface waves of large aerial power can reach a relatively long distance, but Japan's standard radio waves are Fukushima Prefecture (40 kHz) and Fukuoka. It is transmitted at two places on the prefectural border (60 kHz) between the prefecture and Saga prefecture.

  Since the standard radio wave is a long wave of 40/60 kHz, there is a wraparound in a building or the like, but since there is little reflection, the actual situation is that it does not reach the back of the reinforcing bar building sufficiently. In addition, the standard radio wave reception antenna has directivity and various noises exist in this band. Therefore, in order to receive the standard radio wave reliably, use a time zone with low noise (such as midnight). In addition, it is necessary to receive the antenna of the radio timepiece by installing it in the reception environment (reception position and direction) with the strongest radio wave.

In this regard, conventionally, a radio timepiece that displays that the standard radio wave has been correctly received is displayed under the second hand or the like. Patent Document 1 describes a radio timepiece that stores a reception result indicating whether or not a standard radio wave has been received and a reception time in association with each other and displays them on a screen.
JP 2001-324583

  However, in any of the above cases, it is merely informed that reception is possible, and it is impossible to know whether or not the radio timepiece is installed in an optimal reception environment (reception position and direction). Moreover, since the state of the radio wave changes with time, it is more difficult to confirm. Although a method for finding an optimal reception environment by changing the reception location and direction of the standard radio wave little by little can be considered, it requires complicated work and a lot of time, and is not practical.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a simple support tool for determining an optimal installation environment (installation position and direction) of a radio timepiece.

  In order to solve the above-described problem, the long wave detection circuit according to the first aspect of the present invention causes an oscillation wave of a predetermined frequency to act on a long wave that is an input signal, and generates a beat having a frequency corresponding to the frequency difference. Generating circuit, operational amplifier for amplifying the output of the beat generating circuit, first and second diodes connected in the forward direction between the input and output of the operational amplifier, and the output of the second diode as the operational amplifier And an RC parallel circuit that negatively feeds back to the input of the operational amplifier, envelope detection is performed on the output of the operational amplifier to generate a beat, a gain of the circuit for the beat is 1 or more, and a gain for the long wave band is less than 1 Is.

According to the present invention, when a long wave is present in the input signal, an oscillation wave having a predetermined frequency is applied to the long wave (for example, addition or subtraction), so that a frequency corresponding to the frequency difference (for example, 1 kHz) is obtained. Generate a beat. Further, the combined wave as the beat is amplified by the operational amplifier, and at the same time, the operational amplifier output is envelope-detected by the action of the first and second diodes and the RC negative feedback circuit. In that case, the gain of the circuit with respect to the beat (low frequency) is 1 or more (for example, about 12 to 20 times), and the gain with respect to the long wave band (high frequency) is less than 1 (preferably sufficiently small), With such a simple circuit configuration, beats can be generated stably and reliably without causing the circuit to oscillate. On the other hand, if no long wave exists in the input, no beat is generated.

  According to a second aspect of the present invention, there is provided a long wave detection device including a directional antenna, a receiving circuit that extracts and amplifies a long wave having a predetermined frequency from a radio wave received by the antenna, and a predetermined oscillation wave is applied to the long wave. A beat generation circuit for generating an audible band beat; an operational amplifier for amplifying the output of the beat generation circuit; first and second diodes connected in a forward direction between the input and output of the operational amplifier; An RC parallel circuit that negatively feeds back the output of the second diode to the input of the operational amplifier, generates an beat by envelope detection of the output of the operational amplifier, and sets a gain of the circuit with respect to the beat to 1 or more, and The gain for the long wave band is less than 1.

  In the present invention, when this device (directional antenna) is installed in an optimal reception environment (reception position and direction), a beat having a relatively large amplitude is generated, and in other cases, a beat is not generated. Or small enough. Therefore, the optimal reception environment (reception position and direction) of the radio timepiece can be easily detected.

  In a third aspect of the present invention, the long wave detection device further comprises means for converting the generated beat into sound. ADVANTAGE OF THE INVENTION According to this invention, the advanced judgment about an electromagnetic wave reception state can be easily performed by the structure which converts a beat into a sound and listens. For example, the difference between standard radio waves and noise can be easily heard. In addition, changes in the strength of the received electric field strength can be easily heard, so that the optimum installation position and direction can be easily determined.

  In the long wave detection device according to the fourth aspect of the present invention, the long wave is a standard radio wave of 40 kHz or 60 kHz.

  As described above, according to the present invention, the optimum reception environment (reception position and direction) of the radio timepiece can be detected easily and surely, which greatly contributes to the improvement of the reliability and the spread of the radio timepiece.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings.

FIG. 1 is a diagram showing a configuration of a long wave detection device according to an embodiment. In the figure, 11 is a bar antenna having directivity in a direction perpendicular to a coil (winding direction), and 12 is a long wave band received by the bar antenna 11. A receiving circuit that tunes and amplifies the frequency of 40 kHz or 60 kHz, VR1 is a volume for adjusting reception sensitivity (GAIN), 13 is a frequency close to the receiving frequency 40/60 kHz to generate a beat of a required audible frequency (for example, 1 kHz). (For example, 41/61 kHz) an oscillation circuit that generates a signal, VR2 is a volume (TONE) for adjusting the oscillation frequency (and hence beat frequency), SW is a changeover switch (FREQENCY) for switching the reception frequency 40/60 kHz, 14 is Multiple functions for detecting long waves that are input signals (beat generation, amplification and detection, and long wave attenuation) Is a long wave detection circuit realized by a single operational amplifier circuit, 15 is a low frequency amplification circuit for amplifying the detected beat, VR3 is a volume for adjusting the volume of the beat (VOLUME), and 16 is for converting the beat into sound. An earphone (or a speaker).

  In the following description, the case where a 40 kHz standard radio wave is detected will be mainly described, but the same applies to the case where a 60 kHz standard radio wave is detected.

When this apparatus is directed to the arrival direction of a 40 kHz standard radio wave, the long wave band 40 kHz long wave is extracted and amplified by the receiving circuit 12 and input to the long wave detection circuit 14. In the long wave detection circuit 14, the long wave 40 kHz which is an input signal and the 41 kHz oscillation wave from the oscillation circuit 13 are added through resistors R 5 and R 6. An audible beat of 1 kHz can be created by adding a 41 kHz oscillation wave to the 40 kHz long wave input to the long wave detection circuit. This is explained as follows. In other words, a long wave of 40 kHz is represented by y ₁ , and an oscillation wave of 41 kHz is represented by y _2, and these are represented by equations (1) and (2), respectively.

Here, A ₁ and A ₂ are amplitudes, and the angular frequency has a relationship of frequency f with ω = 2πf ₁ and ω + Δω = 2πf ₂ . At this time, the composite wave is given by superposition of these,

It becomes. However,

It is. The amplitude term in equation (3)

Represents a beat, and the beat frequency f is
f = f ₂ −f ₁ (4)
Given in. As a result, a 1 kHz beat is generated as a synthesized wave.

  Further, the synthesized wave is inverted and amplified by the operational amplifier OA1, and at the same time, the output of the operational amplifier OA1 is envelope-detected by the action of the negative feedback circuit in which the diodes D1 and D2 whose characteristics are improved by the operational amplifier and R4 and C1 are connected in parallel. As can be seen from equation (3), the magnitude of the beat varies depending on the magnitude of the oscillation wave to be added and the long wave that is the input signal. Although it is difficult to specify an approximate beat gain, the gain when 1 kHz is input to the long wave detection circuit 14 is sufficiently large (for example, 12 times or more) as compared to the long wave gain. On the other hand, in the capacitor C1, a sufficiently large value that works as a high-pass filter is selected for the long wave (40 kHz), so that the gain of the long wave detection circuit 14 for the long wave is set to a sufficiently small value of less than 1. ing. The beat of the output thus obtained is amplified by the low frequency amplifier circuit 15 and added to the earphone 16.

  The long wave detection circuit 14 according to the present embodiment oscillates a circuit based on a wraparound to a long wave input by a simple circuit configuration in which the above-described composite function is realized by a single-stage operational amplifier circuit and effective gain control. Beats can be generated stably and reliably while being effectively suppressed.

  FIG. 2 shows a beat waveform diagram. When this apparatus is directed in the direction of arrival at the position where the standard radio wave arrives, a beat having an amplitude corresponding to the received electric field strength is generated, and the earphone 16 can faithfully listen to the reception status of the standard radio wave. On the other hand, no beat is generated when a standard radio wave of 40/60 kHz is not received or when noise is received. According to the present embodiment, it is possible to effectively distinguish between beats and other noises by sound, so that the reliability of radio wave detection is greatly improved.

  FIG. 3 is a circuit diagram of a long wave detection circuit 14 'according to another embodiment, and shows another case where diodes D1 and D2 are connected in the forward direction between the input and output of the operational amplifier OA1. In the figure, the diodes D1 'and D2' in this case are connected in the opposite direction to the case of FIG. Other configurations may be the same as in FIG. In this example, when the synthesized wave swings to the higher side with reference to the potential V1 of the + input terminal of the operational amplifier OA1, the output of the operational amplifier OA1 swings to the lower side than V1. It is obvious that this circuit also functions as a long wave detection circuit similar to FIG.

  FIG. 4 is an external view of a long wave detection device (time wave locator) according to the embodiment, and a method for detecting a standard radio wave using this device will be described below. After turning on the power (POWER), hold the device horizontally or vertically, change the direction, adjust the reception sensitivity (GAIN) and volume (VOLUME), and use the earphone to meet the beat (about approx. Listen to 1kHz intermittent sound.

  If the intermittent sound of the beat sounds loud regardless of the orientation of the device, adjusting the reception sensitivity to make it easier to understand the strength of the sound and the direction of arrival of the radio wave. Conversely, if the beat intermittent sound is small in any direction, increasing the reception sensitivity makes it easier to understand the strength of the sound and the direction of arrival of radio waves.

  If necessary, the tone (TONE) can be adjusted so that the tone is easy to hear. Furthermore, depending on the area and location, select the frequency with the loudest sound (FREQ: 40/60 kHz), and adjust the reception sensitivity and volume so that it is easy to judge the strength of the sound while changing the orientation of the device. It is possible. If the noise is high, move the device to a place where the noise is low and check the direction of the radio wave. Thus, when the beat intermittent sound is maximized while changing the direction of the device, the direction in which the device is facing (arrow direction) is the arrival direction of the standard radio wave.

  In the above embodiment, an audible band beat is generated and listened to with an earphone. However, the present invention is not limited to this. In addition, the reception state may be displayed with light. In this case, in order to distinguish between beat and noise, a filter circuit, a DSP process, and the like are preferably added.

 Moreover, although the said embodiment was demonstrated with the specific numerical example, this invention is not limited to these numerical examples.

  Further, although the preferred embodiment of the present invention has been described, it goes without saying that various changes in the configuration, control, processing, and combination of each part can be made without departing from the spirit of the present invention.

It is a figure which shows the structure of the long wave detection apparatus by embodiment. It is a wave form diagram of the long wave detection circuit by embodiment. It is a circuit diagram of the long wave detection circuit by other embodiment. It is an external view of the long wave detection apparatus (time wave locator) by embodiment.

Explanation of symbols

10 Long wave detector (time wave locator)
11 Bar antenna 12 Reception circuit 13 Oscillation circuit 14 Long wave detection circuit 15 Low frequency amplification circuit 16 Earphone SW changeover switch VR1 to VR3 Volume

Claims (4)

A beat generation circuit that causes an oscillation wave of a predetermined frequency to act on a long wave that is an input signal and generates a beat having a frequency according to the frequency difference;
An operational amplifier for amplifying the output of the beat generation circuit;
First and second diodes connected in the forward direction between the input and output of the operational amplifier and the output;
An RC parallel circuit for negatively feeding back the output of the second diode to the input of the operational amplifier;
A long wave detection circuit characterized in that the output of the operational amplifier is envelope-detected to generate a beat, the gain of the circuit for the beat is 1 or more, and the gain for the long wave band is less than 1. A directional antenna;
A receiving circuit that extracts and amplifies long waves of a predetermined frequency from radio waves received by the antenna;
A beat generation circuit that causes a predetermined oscillating wave to act on the long wave and generates an audible beat;
An operational amplifier for amplifying the output of the beat generation circuit;
First and second diodes connected in the forward direction between the input and output of the operational amplifier and the output;
An RC parallel circuit for negatively feeding back the output of the second diode to the input of the operational amplifier;
A long wave detection device characterized in that an envelope is detected from the output of the operational amplifier to generate a beat, a gain of the circuit for the beat is 1 or more, and a gain for a long wave band is less than 1. 3. The long wave detection device according to claim 2, further comprising means for converting the generated beat into sound. 3. The long wave detection device according to claim 2, wherein the long wave is a standard radio wave of 40 kHz or 60 kHz.

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