JPH08139773A - Fsk reception device - Google Patents

Abstract

PURPOSE: To detect deviation of an intermediate frequency signal with simple constitution and control a local oscillation frequency by correcting an oscillation frequency in the direction wherein the difference between the counting result of a pulse quantity measuring means and the predetermined reference number of pulses becomes 0. CONSTITUTION: When the output of a band-pass filter 14 is larger than a specific level, a detection means 17 generates an output and the pulse quantity measuring means 18 is actuated. Then the number of pulses outputted from a pulse waveform shaping means 15 is measured for a certain predetermined time. Here, the shaping means 15 amplifies the output of the band-pass filter 14 and converts it into a pulse waveform by using a comparator. A frequency-voltage converting means 16 converts the frequency variation of the input into voltage variation and imposes FSK demodulation, and the demodulated signal is outputted to an output terminal 20. The number of pulses measured by the measuring means 18, on the other hand, is inputted to a frequency correcting means 19 to calculate an error in the predetermined reference number of pulses. Then a control voltage corresponding to the error is generated at the filter 14 to eliminate the error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a direct conversion type FSK receiver.

[0002]

2. Description of the Related Art Generally, a single superheterodyne system or a double superheterodyne system in which an FSK modulated signal received is converted into an intermediate frequency signal and then demodulated is used as an FSK receiving system in wireless communication. Further, there is a direct conversion system as a reception system in which a band filter for removing an image frequency and a band filter for removing an adjacent channel signal can be configured by an IC. As an example of the direct conversion system, the received signal is converted into two orthogonal baseband signals by respectively mixing two orthogonal local oscillation signals having a frequency substantially equal to the center frequency of the received signal and the received signal, and the desired filter is used. There is a method in which only the signal is taken out, and then converted to an intermediate frequency of several tens of kHz and demodulated.
In any of the receiving methods, if the oscillation frequency stability of the local oscillating means is poor, the receiving characteristics deteriorate. Therefore, the FSK receiving configured to control the oscillating frequency of the local oscillating means so that the intermediate frequency signal comes to the center of the bandpass filter There is a device.
As an example of a conventional FSK receiver for controlling such a local oscillation frequency, the received reference frequency is frequency analyzed as shown in "Receiver" of Japanese Patent Application No. 58-230807, and the result of the frequency analysis is shown. There is a configuration for controlling the local oscillating means based on the above. As another example, as shown in "AFC system for FSK receiver" in Japanese Patent Publication No. 55-37131, a frequency discriminating circuit (= frequency-voltage) is used by using a front signal transmitted prior to the information code. AFC closed loop is formed by using the output of the conversion means), the oscillation frequency of the local oscillation means is controlled, the control voltage of the AFC closed loop is stored when the reception of the front signal is completed, and the stored control voltage is opened loop. There is a configuration in which it is applied to the local oscillating means by means of.

[0003]

However, in the above-mentioned conventional FSK receiving apparatus, a method using the Fourier transform method or a method in which a plurality of filters are arranged is used as the frequency analyzing means. An analog filter was required and it could not be constructed at low cost. Also, since a single frequency signal is required as the reference frequency or the front signal, an unnecessary single frequency signal must be sent before the bit synchronization signal which consists of repeated 1s and 0s and is transmitted prior to the information. However, there is a problem that the transmission efficiency is deteriorated. Further, the timing of starting the operation of the frequency analysis means and the timing of starting the control of the local oscillation frequency are not clear in the above two cited examples, and it is necessary to always perform the frequency analysis operation and the reception operation of the reference frequency and the front signal. The conventional method could not be adopted for the intermittent FSK receiving system.

The present invention solves the above problems and has a simple structure and detects the deviation of the intermediate frequency signal from the center of the band-pass filter without adding an unnecessary additional signal before the bit synchronization signal to detect the local oscillation frequency. F that can control
The purpose is to realize an SK receiver.

[0005]

In order to achieve the above object, the FSK receiving apparatus of the present invention is a FSK that is frequency-modulated with a signal including a bit synchronization signal that is made up of repeating 1s and 0s and that is transmitted prior to information. An FSK receiving device for converting a modulated signal into an intermediate frequency signal and then demodulating the signal, wherein a local oscillating means for outputting a local oscillating signal, and the local oscillating signal and the FSK modulated signal are mixed to output an intermediate frequency signal. Mixing means, pulse waveform shaping means for converting the intermediate frequency signal into a pulse waveform, pulse number measuring means for measuring the number of pulses from the pulse waveform shaping means for a predetermined time, and pulse number measuring means A signal for correcting the oscillation frequency of the local oscillating means is output in a direction in which the difference between the measurement result in step 1 and the predetermined reference pulse number is set to 0. And a wave number correction means.

Further, local oscillating means for outputting a local oscillating signal, and mixing means for mixing the local oscillating signal and the FSK modulated signal to output an intermediate frequency signal,
Pulse waveform shaping means for converting the intermediate frequency signal into a pulse waveform, time measuring means for measuring the time until the number of pulses from the pulse waveform shaping means reaches a predetermined number, and measurement by the time measuring means It is also provided with frequency correction means for outputting a signal for correcting the oscillation frequency of the local oscillation means in a direction in which the difference between the result and the predetermined reference time is set to zero.

Further, level detecting means for detecting whether or not the reception level of the FSK modulated signal is above a certain level, local oscillating means for outputting a local oscillating signal, and the local oscillating signal and the FSK modulated signal are mixed. Then, a mixing means for outputting an intermediate frequency signal, a pulse waveform shaping means for converting the intermediate frequency signal into a pulse waveform, and the level detecting means when the reception level of the FSK modulated signal is above a certain level. The difference between the pulse number measuring means for measuring the pulse number from the pulse waveform shaping means for a predetermined time and the difference between the measurement result by the pulse number measuring means and the predetermined reference pulse number is 0.
And a frequency correction means for outputting a signal for correcting the oscillation frequency of the local oscillation means.

Further, level detecting means for detecting whether or not the reception level of the FSK modulated signal is above a certain level, local oscillating means for outputting a local oscillating signal, and the local oscillating signal and the FSK modulated signal are mixed. Then, a mixing means for outputting an intermediate frequency signal, a pulse waveform shaping means for converting the intermediate frequency signal into a pulse waveform, and the level detecting means when the reception level of the FSK modulated signal is above a certain level. In a direction in which the time measuring means for measuring the time until the number of pulses from the pulse waveform shaping means reaches a predetermined number and the difference between the measurement result by the time measuring means and the predetermined reference time are set to 0. And a frequency correction means for outputting a signal for correcting the oscillation frequency of the local oscillation means.

Further, level detecting means for detecting whether or not the reception level of the FSK modulated signal is above a certain level, local oscillating means for outputting a local oscillating signal, and the local oscillating signal and the FSK modulated signal are mixed. And a frequency-voltage converting means for outputting a voltage corresponding to the frequency of the intermediate frequency signal, and a level of the FSK modulated signal received by the level detecting means. When it is determined that the average voltage output means outputs the average voltage of the output voltage from the frequency-voltage conversion means during a certain period, the difference between the voltage from the average voltage output means and a predetermined reference voltage is set to 0. Direction correction means for outputting a signal for correcting the oscillation frequency of the local oscillation means.

Further, the FSK receiving apparatus includes a first local oscillating means, a signal from the first local oscillating means and the FSK.
First mixing means for extracting a signal having a frequency of a difference between modulated signals, and second mixing means for extracting a signal having a frequency of a difference between an FSK modulated signal and a signal obtained by phase-shifting the signal from the first local oscillation means. Means, a first low-pass filter that receives the signal from the first mixing means, a second low-pass filter that receives the signal from the second mixing means, and temporally Second local oscillation means for generating a continuous rectangular wave signal, first switching means for switching the signal from the first low-pass filter by the rectangular wave signal from the second local oscillation means, Second switch means for switching the signal from the second low-pass filter by a rectangular wave signal obtained by phase-shifting the rectangular wave signal from the second local oscillation means, and the first switch Arithmetic means for adding or subtracting the output signal of the second stage and the output signal of the second switch means, a bandpass filter provided in a stage before or after the arithmetic means, and a frequency of the output signal of the bandpass filter And a frequency-voltage converting means for generating a voltage according to the above, and the output of the band pass filter is an intermediate frequency signal.

[0011]

According to the present invention, the average frequency error of the intermediate frequency signal with respect to the FSK modulation signal modulated by the bit synchronization signal can be measured by the above configuration, and the local oscillation frequency can be controlled by this.

Further, since the frequency correction operation can be started when the FSK modulation signal modulated by the bit synchronization signal of a certain level or more is input, it can be easily introduced into the intermittent reception operation system.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 is an antenna, 2 is a high frequency amplifying means, 3 is a first mixing means, 4 is a first low pass cutoff filter for cutting off a DC component, 5 is a first switch means, 6 is a first local oscillation Means, 7 is a 90 ° phase shifter, 8 is a second mixing means, 9 is a second low pass cutoff filter for cutting off a DC component, 10 is a second local oscillating means, and 11 is a 9
0 ° phase shift means, 12 is second switch means, 13 is arithmetic means for performing addition / subtraction, 14 is a third band pass filter, 1
5 is a pulse waveform shaping means, 16 is a frequency-voltage converting means, 17 is a level detecting means, 18 is a pulse number measuring means,
Reference numeral 19 is frequency correction means, and 20 is a demodulation output terminal. The first and second low pass cutoff filters 4 and 9 are band pass filters for the purpose of removing adjacent channels. The FSK receiver shown in FIG. 1 is a direct conversion type receiver.

Now, let us consider a case where a carrier of 400 MHz band is FSK-modulated with 2400 bps data as an FSK modulated signal. When the FSK modulated signal is input to the antenna 1, it is amplified by the high frequency amplification means 2 and mixed down with the signals oscillated by the first local oscillation means by the first mixing means 3 and the second mixing means 8. The oscillation frequency of the first local oscillation means is FS input to the antenna 1.
The frequency is set to be substantially equal to the carrier frequency of the K modulation signal. The first mixing means 3 outputs an I signal which is a low frequency signal, and the second mixing means 8 outputs a Q signal which is a low frequency signal. The I signal and the Q signal are orthogonal to each other, and the frequency modulation information of the FSK modulated signal appears as the phase lead / lag information of the I signal and the Q signal. The I signal and the Q signal are generated by the oscillation signal of the second local oscillation means 10, and the first switching means 5 and the second switching means 1 are used.
Mix up with 2. And the calculating means 13
The phase lead / lag information of the I signal and the Q signal is extracted again as a frequency-modulated intermediate frequency signal by adding or subtracting. The oscillation frequency of the second local oscillating means is, for example, 16 kHz, so that the intermediate frequency signal from the computing means 13 is approximately 16 kHz. The third band pass filter 14 removes the interfering signal and extracts the intermediate frequency signal which is the desired signal. When the output of the third bandpass filter 14 is above a certain level, an output is generated from the level detecting means 17 and the pulse number measuring means 18 is activated. When the pulse number measuring means 18 is activated, the number of pulses output from the pulse waveform shaping means is measured for a predetermined time (for example, 10 msec). The pulse waveform shaping means amplifies the output of the third bandpass filter and converts it into a pulse waveform using a comparator.
The frequency-voltage conversion means 16 performs FSK demodulation by converting the input frequency change into a voltage change. F
The SK demodulated signal is output to the output terminal 20. The number of pulses measured by the pulse number measuring means 18 is input to the frequency correction means 19. The frequency correcting means 19 calculates an error between the predetermined reference pulse number and the pulse number measured by the pulse number measuring means 18, and generates a control voltage corresponding to the error. The oscillation frequency of the first local oscillation means 6 is controlled by the control voltage, and the average frequency of the intermediate frequency signal output from the third band pass filter 14 becomes approximately 16 kHz. The frequency correction operation described above will be explained in more detail. The oscillation frequency of the first local oscillation means 6 is 3k from the carrier frequency of the FSK modulated signal input to the antenna 1.
Consider the case where there is a Hz offset. Then, the center frequency of the intermediate frequency signal output from the third bandpass filter 14 is 1
It shifts from 6 kHz by 3 kHz to 19 kHz. Since the pulse number measuring means 18 measures an intermediate frequency signal pulse of 19 kHz for 10 msec, 190 pulses are counted, and 160 pulses are stored as a reference pulse, and 30 is output to the frequency correcting means 19 as a pulse number error. To do. The frequency correction means 19 generates a DC voltage corresponding to 30 by D / A conversion, and controls the first local oscillation means so that the center frequency of the intermediate frequency signal becomes approximately 16 kHz. The FSK receiver of FIG. 1 is intermittently turned on for a short time of about 20 msec at a certain fixed interval, for example, 30 sec interval. When no output is generated from the level detecting means 17 while the power is on, it is considered that there is no signal from the communication partner and the power is turned off until the next 30 seconds. If an output is generated from the level detecting means 17, the power is kept on and the pulse number measuring means 18 measures the number of pulses. This is a method for operating the FSK receiving apparatus on a battery for a long time. The synchronization of the transmission / reception timing every 30 seconds with the communication partner can be achieved, for example, by always transmitting from one side every 10 minutes, the other side receiving the radio wave, and adjusting the clock to the transmission partner. Therefore, it is possible to detect the level and measure the number of pulses in the portion of the FSK modulated signal from the communication partner that is modulated by the bit synchronization signal. The pulse number measuring means 18 can be simply composed of a counter and a timer for controlling the start and end of the operation of the counter. The timer starts its operation in response to the signal from the level detecting means 17, for example, 10
It is a 10-msec timer that ends the operation after msec. Further, the frequency correction means 19 can be simply constructed by a microcomputer having a storage means for storing the reference pulse number and a D / A conversion means.

Another embodiment of the present invention will be described with reference to FIG. In FIG. 2, the same numbers are assigned to those having the same functions as those in FIG. The difference between the embodiment of the present invention shown in FIG. 1 and the embodiment of the present invention shown in FIG. 2 is that in the embodiment shown in FIG. 2, the pulse waveform shaping means 15 replaces the pulse number measuring means 18 shown in FIG. The point is that time measuring means 21 is provided for measuring the time until the number of pulses of the converted intermediate frequency signal reaches a predetermined value. When the input of the FSK modulated signal to the antenna 1 is detected,
The level detecting means 17 outputs a signal. The time measuring means 21 is activated by this signal. The time measuring means 21
For example, the time from the activation until the intermediate frequency signal pulse reaches 160 is measured. If the center frequency of the intermediate frequency signal is 16 kHz, the time measured by the time measuring means 21 is 10 ms. When the center frequency of the intermediate frequency signal is 19 kHz, the time measured by the time measuring means 21 is 8.42 msec. The time information measured by the time measuring means 21 is input to the frequency correcting means 19. The frequency correction means 19 stores 10 ms as a reference time, and calculates a time error from the input time information. If the input time information is 10 msec, the time error is 0, and the frequency correction operation is not performed. If the input time information is 8.42 msec, the time error is 1.58 msec, and the control voltage corresponding to 1.58 is output. Then, the oscillation frequency of the first local oscillation means is controlled by the control voltage from the frequency correction means 19 so that the intermediate frequency signal becomes approximately 16 kHz. The time measuring means 21 can be simply configured with a counter that generates a carry when counting up to 160 pulses from the pulse waveform shaping means 15 and a timer that ends the time measurement when a carry occurs from the counter. The counter and the timer are initially activated by a signal from the level detecting means 17. The advantage of the embodiment shown in FIG. 2 is that if the accuracy of the timer that constitutes the time measuring means 21 is improved, the accuracy of measurement of the center frequency of the intermediate frequency signal can be improved, so that the frequency can be corrected more accurately. is there.

Next, another embodiment of the present invention will be described with reference to FIG. In FIG. 3, components having the same functions as those in FIG. 1 are given the same numbers. The difference between the embodiment of the present invention shown in FIG. 3 and the embodiment of the present invention shown in FIG. 1 is that in the embodiment of FIG. 3, the frequency-voltage converting means 16 is used instead of the pulse number measuring means 18 of FIG. The average voltage output means 22 for taking out the voltage output corresponding to, averaging the voltage output for a certain period, and outputting the averaged average voltage is provided. When detecting that the FSK modulated signal is input to the antenna 1, the level detecting means 17 outputs the signal. The average voltage output means 22 is activated by this signal. The average voltage output means 22 is, for example, 1 after being activated.
Average the voltage up to 0 ms. The frequency-voltage conversion means 16 outputs a voltage proportional to the input frequency. For example, when the intermediate frequency which is the input frequency is 16 kHz, it is 1 volt, and the output of 0.1 volt changes every time the frequency changes by 1 kHz. Therefore, the output is 1.3 V when the intermediate frequency is 19 kHz. The voltage information averaged by the average voltage output means 22 is input to the frequency correction means 19. The frequency correction means 19 stores 1 volt as a reference voltage, and calculates an error from the input voltage information. If the input voltage information is 1 volt, the error is 0, and the frequency correction operation is not performed. If the input voltage information is 1.3 volts, the error is 0.3 volts, and the control voltage corresponding to 0.3 is output. Then, the oscillation frequency of the first local oscillation means is controlled by the control voltage from the frequency correction means 19 so that the intermediate frequency signal becomes approximately 16 kHz.
It is conceivable that the output voltage of the frequency-voltage converting means 16 may change momentarily due to the influence of temperature or the like even if the input frequency is the same. Therefore, it is necessary to change the reference voltage stored in the frequency correction means 19 from time to time. There is the following method as the method. When there is no signal input to the antenna 1, the intermediate frequency signal is only a noise signal. Therefore, the center frequency of the noise signal is the third bandpass filter 14
The center frequency is 16 kHz. Further, the first switching means 5 and the second switching means 12 perform the switching operation using the second local oscillation frequency of 16 kHz. The first switch means 5 and the second switch means 12 have a balanced switch configuration in which a local oscillation frequency of 16 kHz does not occur in the output, but a 16 kHz signal is generated due to variations in transistors forming the balanced switch. There is a slight leak in the output. Therefore, when no signal is input to the antenna 1, the center frequency of the intermediate frequency signal is approximately 16 kHz. Therefore, when the level detection means 17 does not detect the signal input to the antenna 1, the output signal of the frequency-voltage conversion means 16 is changed to the average voltage output means 2 for a certain period (for example, 10 msec).
2 and the averaged voltage is taken into frequency correction means 19
Stored in the storage means. This storage operation is performed, for example, every 10 minutes, which is an integral multiple of every 30 seconds. It is also possible to break the balance of the switches by changing the bias of the first switch means 5 and the second switch means 12 in order to positively leak the 16 kHz signal, and to leak the second local oscillation signal.

FIG. 4 shows an example of the configuration of the frequency-voltage converting means 16. In FIG. 4, 23 is an input terminal to which the signal from the pulse waveform shaping means 15 is input, 24 is edge detection means, 25 is a monostable multivibrator, 2
6 is a low-pass filter, and 20 is an output terminal. FIG. 5 shows a signal waveform diagram of each terminal in FIG. In FIG. 5, a is a signal waveform of the terminal 23, b is an output waveform of the edge detecting means 24, c is an output waveform of the monostable multivibrator 25, and d.
Is the output waveform of the low-pass filter 26. Input terminal 2
The rising edge of the pulse of the intermediate frequency signal pulse (a in FIG. 5) input to 3 is detected by the edge detecting means 24. The detected rising edge (b in FIG. 5) activates the monostable multivibrator 25, and a pulse having a constant pulse width (c in FIG. 5) is output to the output of the monostable multivibrator 25. Therefore, the demodulated signal is output to the output of the low pass filter 26 (d in FIG. 5). Output of monostable multivibrator 25 (c in FIG. 5)
Is a pulse signal having the same frequency as the intermediate frequency signal pulse (a in FIG. 5) output from the pulse shaping means 15. Therefore, up to the monostable multivibrator 25 can be regarded as the pulse waveform shaping means 15, and the output signal of the monostable multivibrator 25 can be input to the pulse number measuring means 18 of FIG. 1 or the time measuring means 21 of FIG. Further, although the edge detecting means 24 has been described as detecting only the rising edge, both the rising edge and the falling edge may be detected. In this case, the output of the monostable multivibrator 25 is twice the output of the intermediate frequency signal.
Therefore, when considering up to the monostable multivibrator 25 as the pulse waveform shaping means 15, the pulse number measuring means 18 and the time measuring means 2 are taken into consideration in consideration of the doubled frequency.
1. It is necessary to change the constants such as the number of reference pulses and the number of pulses to be taken in by the frequency correction means 19.

[0018]

As described above, according to the FSK receiver of the present invention, the local oscillating means for generating the intermediate frequency signal, the pulse waveform shaping means for converting the intermediate frequency signal into the pulse waveform, and the pulse The pulse number measuring means for measuring the number of pulses from the waveform shaping means for a predetermined time, and the local portion in a direction in which the difference between the measurement result of the pulse number measuring means and the predetermined reference pulse number is zero. Since it is composed of frequency correction means for outputting a signal for correcting the oscillation frequency of the oscillation means, it is possible to accurately identify the frequency error with a simple timer or counter and a microcomputer and correct the local oscillation frequency.

Further, instead of measuring the number of pulses for a certain time, which is the pulse number measuring means 18, the time measuring means 2
By measuring the time until the number of pulses of the intermediate frequency signal reaches a certain value at 1, the frequency error can be more accurately identified.

Further, since the level detecting means 17 is provided, it is possible to perform the frequency error detection and the frequency correction only when the reception signal is detected in the receiving device which performs the intermittent reception. Therefore, when the reception signal is not detected, the frequency correction is performed. Since it is not necessary to turn on the power supply to the circuit for an extra time for, there is an effect that the current consumption can be reduced.

Further, the first local oscillating means, the first mixing means for taking out a signal having the frequency of the difference between the signal from the first local oscillating means and the FSK modulated signal, and the first local oscillating means. And the signal obtained by phase-shifting the signal from
Second mixing means for extracting a signal having a frequency that is the difference between the SK modulated signals, a first low-pass cutoff filter for receiving the signal from the first mixing means, and a signal from the second mixing means. A second low-frequency cutoff filter, a second local oscillating means for generating a rectangular wave signal continuous in time, and a rectangular wave signal from the second local oscillating means for the first low-pass filter. First switching means for switching the signal from the band cut-off filter, and a signal from the second low-frequency cut-off filter is switched by a rectangular wave signal obtained by phase-shifting the rectangular wave signal from the second local oscillation means. A second switch means, an arithmetic means for adding or subtracting an output signal of the first switch means and an output signal of the second switch means, and a stage before or after the arithmetic means. Band-pass filter and a frequency-voltage converting means for generating a voltage corresponding to the frequency of the output signal of the band-pass filter, the output of the band-pass filter is an intermediate frequency signal, by the intermediate frequency signal Since the frequency can be set to a low frequency, the processing speed of the pulse number measuring means 18 or the time measuring means 21 can be slowed down, which not only simplifies the circuit configuration, but also
The effect is that the current consumption can be reduced.

In particular, in the case of incorporating a wireless transmission / reception device in a gas meter in an automatic meter reading system such as a gas meter, it is necessary to have a small-sized receiving device which can be operated by a battery for 10 years. Since it is installed outdoors, temperature conditions are severe, and there is a problem that the frequency of the crystal oscillator that defines the local oscillation frequency varies greatly. Therefore, it is necessary to use the direct conversion receiving method for downsizing and the intermittent operation method for reducing current consumption, and to perform frequency correction to cope with the frequency fluctuation of the crystal oscillator. Further, not only in the automatic meter reading system, but also in a wireless remote control device used for a housing equipment system such as a remote control device for wirelessly connecting a gas water heater and a kitchen, small size and battery drive are essential conditions. The present invention satisfies the above three requirements and can provide a very effective FSK receiving apparatus.

Further, according to the structure for detecting the frequency error by using the output of the frequency-voltage converting means 16, the circuit structure can be further simplified.

[Brief description of drawings]

FIG. 1 is a block diagram of an FSK receiver according to an embodiment of the present invention.

FIG. 2 is a block diagram of an FSK receiver according to another embodiment of the present invention.

FIG. 3 is a block diagram of an FSK receiver according to still another embodiment of the present invention.

FIG. 4 is a block diagram of frequency-voltage conversion means in the embodiment of the present invention.

5 is a signal waveform diagram of each part of the frequency-voltage converting means in FIG.

[Explanation of symbols]

 1 Antenna 2 High Frequency Amplifying Means 3 First Mixing Means 4 First Band Pass Filter 5 First Switch Means 6 First Local Oscillating Means 7 90 ° Phase Shifter 8 Second Mixing Means 9 Second Band Pass Filters 10 Second Local Oscillating Means 11 90 ° Phase Means 12 Second Switching Means 13 Computing Means 14 Third Bandpass Filters 15 Pulse Waveform Shaping Means 16 Frequency-Voltage Converting Means 17 Level Detecting Means 18 Pulse Count Measuring Means 19 Frequency Correction means 20 Output terminal 21 Time measurement means

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Terue Matsumura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. An FSK receiver for converting an FSK modulated signal, which is frequency-modulated with a signal including a bit synchronizing signal transmitted before information by repeating 1s and 0s, into an intermediate frequency signal and then demodulating it. Local oscillating means for outputting an oscillating signal; mixing means for mixing the local oscillating signal and the FSK modulated signal to output an intermediate frequency signal; pulse waveform shaping means for converting the intermediate frequency signal into a pulse waveform; In a direction in which the difference between the pulse number measuring means for measuring the number of pulses from the pulse waveform shaping means for a predetermined time period and the measurement result of the pulse number measuring means and the predetermined reference pulse number is zero. An FSK receiving device comprising a frequency correction means for outputting a signal for correcting the oscillation frequency of the local oscillation means. 2. An FSK receiving apparatus for converting an FSK modulated signal, which is frequency-modulated with a signal including a bit synchronizing signal transmitted before information by repeating 1s and 0s, into an intermediate frequency signal and then demodulating the converted signal. Local oscillating means for outputting an oscillating signal; mixing means for mixing the local oscillating signal and the FSK modulated signal to output an intermediate frequency signal; pulse waveform shaping means for converting the intermediate frequency signal into a pulse waveform; In a direction in which the time measuring means for measuring the time until the number of pulses from the pulse waveform shaping means reaches a predetermined number and the difference between the measurement result by the time measuring means and the predetermined reference time are set to 0. An FSK receiving device comprising a frequency correction means for outputting a signal for correcting the oscillation frequency of the local oscillation means. 3. An FSK receiving apparatus for converting an FSK modulated signal, which is frequency-modulated with a signal including a bit synchronizing signal transmitted before information by repeating 1s and 0s, into an intermediate frequency signal and then demodulating the converted signal. Level detecting means for detecting whether or not the reception level of the FSK modulated signal is above a certain level, local oscillating means for outputting a local oscillating signal, and the intermediate frequency signal by mixing the local oscillating signal with the FSK modulated signal. And a pulse waveform shaping means for converting the intermediate frequency signal into a pulse waveform, and the pulse waveform shaping means when the level detection means determines that the reception level of the FSK modulated signal is above a certain level. Pulse number measuring means for measuring the number of pulses from a certain period of time, and measurement by the pulse number measuring means Results with a predetermined FSK receiving apparatus is composed of a frequency correction means for the difference and outputs a signal for correcting the oscillation frequency of said local oscillation means in a direction to 0 of the reference pulse number. 4. An FSK receiving apparatus for converting an FSK modulated signal, which is frequency-modulated with a signal including a bit synchronization signal transmitted before information by repeating 1s and 0s, into an intermediate frequency signal and then demodulating the converted signal. Level detecting means for detecting whether or not the reception level of the FSK modulated signal is above a certain level, local oscillating means for outputting a local oscillating signal, and the intermediate frequency signal by mixing the local oscillating signal with the FSK modulated signal. And a pulse waveform shaping means for converting the intermediate frequency signal into a pulse waveform, and the pulse waveform shaping means when the level detection means determines that the reception level of the FSK modulated signal is above a certain level. And a time measuring means for measuring the time until the number of pulses from Results with a predetermined reference time and FSK receiving apparatus is composed of a frequency correction means for the difference and outputs a signal for correcting the oscillation frequency of said local oscillation means in a direction to zero. 5. An FSK receiving apparatus for converting an FSK modulated signal, which is frequency-modulated with a signal including a bit synchronizing signal transmitted before information by repeating 1s and 0s, into an intermediate frequency signal and then demodulating the converted signal. Level detecting means for detecting whether or not the reception level of the FSK modulated signal is above a certain level, local oscillating means for outputting a local oscillating signal, and the intermediate frequency signal by mixing the local oscillating signal with the FSK modulated signal. Of the intermediate frequency signal, a frequency-voltage converting means for outputting a voltage corresponding to the frequency of the intermediate frequency signal, and the level detecting means for FSK.
An average voltage output means for outputting an average voltage for a certain period of the output voltage from the frequency-voltage conversion means when it is determined that the reception level of the modulation signal is equal to or higher than a certain level; An FSK receiving device comprising a frequency correction means for outputting a signal for correcting the oscillation frequency of the local oscillation means in a direction in which the difference from a predetermined reference voltage is zero. 6. An FSK receiving apparatus, comprising: first local oscillating means; first mixing means for extracting a signal having a frequency of a difference between the signal from the first local oscillating means and the FSK modulated signal; A second mixing means for extracting a signal having a frequency difference between the signal obtained by phase-shifting the signal from the one local oscillating means and the FSK modulated signal, and a first low-frequency inputting the signal from the first mixing means. Band cutoff filter, a second low band cutoff filter which receives the signal from the second mixing means, a second local oscillating means for generating a rectangular wave signal continuous in time, and the second First switching means for switching the signal from the first low-pass cutoff filter by a rectangular wave signal from the local oscillating means,
Second switch means for switching the signal from the second low-pass filter by a rectangular wave signal obtained by phase-shifting the rectangular wave signal from the second local oscillation means, and an output signal of the first switch means. And an output means of the second switch means for adding or subtracting, a bandpass filter provided in the preceding stage or the latter stage of the computing means, a voltage according to the frequency of the output signal of the bandpass filter 6. The FSK receiving apparatus according to claim 1, wherein the FSK receiving apparatus comprises a frequency-voltage converting means for generating a signal, and the output of the band pass filter is an intermediate frequency signal.