JPH0469464B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a receiving device that can be used for data communication. Conventional configurations and their problems In recent years, mobile communication services such as pagers and car phones have become popular. In the mobile communications described above, a transmitting/receiving device is used that transmits data such as dial numbers of the own station or the other station. A conventional transmitting/receiving device will be described below with reference to the drawings. FIG. 1 is a block diagram of a conventional transmitting/receiving device. In FIG. 1, denotes a transmitting device and denotes a receiving device. The transmitting device has a tone generating circuit 2 that generates a frequency corresponding to information from an input circuit 1 consisting of a numeric keypad or the like. This tone generation circuit 2 is, for example, an oscillator 2 that generates different frequencies.
a, 2b, 2c, 2d, . In addition, the above transmitter is FM
It has a modulation circuit 3, a transmission circuit 4, and a transmission antenna 5. On the other hand, the receiving device includes a receiving antenna 6, a high frequency amplification circuit 7, a local oscillation circuit 8, a frequency conversion circuit 9, an intermediate frequency amplification circuit 10, an FM demodulation circuit 11,
It has a frequency analysis circuit 12. This frequency analysis circuit 12 is composed of a group of filters 12a, 12b, . . . . Further, the receiving device has an information decoding circuit 13 and an output circuit 14 consisting of a buzzer, a display, or the like. The operation of the transmitting/receiving device configured as described above will be explained below. When the input circuit 1 consisting of a numeric keypad or the like is operated and information is input, a signal with a frequency corresponding to the input information is output from the tone generation circuit 2.The FM modulation circuit 3 converts the high frequency signal into a signal from the tone generation circuit 2. The frequency is modulated by
The signal is amplified by the transmitting circuit 4 and sent out as an electromagnetic wave from the transmitting antenna 5. The function of the tone generating circuit 2 will be explained in more detail with reference to FIG. FIG. 2a is a spectrum diagram of frequencies that can be generated by the tone generating circuit 2. In FIG. FIG. 2b is an output diagram showing a frequency sequence output from the tone generating circuit 2. In FIG. FIG. 2a shows that there are a total of n oscillators 2a, 2b, . . . . Each oscillator 2
The oscillation frequencies of a, 2b... _{are 1} , ₂ , ₃ ,... _o
It is. These oscillation frequency signals are input to input circuit 1.
It is switched with switch 2e based on the information from
It is output according to the time schedule shown in FIG. 2b. That is, the frequency changes every time T. Now, if the number n of oscillation frequencies is 10, then the numbers 0 to 9
If you send 4 frequencies as shown _in Figure _2b ,
You can send a 4-digit number. Next, the receiving device will be explained. The electromagnetic wave input to the receiving antenna 6 is selectively amplified by the high frequency amplification circuit 7, converted to an intermediate frequency by the frequency conversion circuit 9, further selectively amplified by the intermediate frequency amplification circuit 10, and then sent to the FM demodulation circuit 1.
1 is demodulated, and a frequency sequence signal shown in FIG. 2b is output as the output.
The frequency analysis circuit 12 analyzes frequencies ₁ , ₂ , ₃ , ... _o
It consists of n filters 12a, 12b, . . . which separate signals of n frequencies. Only the signal ₁ is taken out from the filter 12a, and only the signal ₂ is taken out from the filter 12b. The information decoding circuit 13 determines in what order and at what frequency the signals from the frequency analysis circuit 12 come, and drives an output circuit 14 such as a buzzer or a display. However, in the above configuration,
Requires frequency modulation circuit. This is because when the signal shown in Fig. 2b is converted into a high-frequency signal by simple frequency conversion and transmitted, and received by the receiving device, the received signal changes from the signal shown in Fig. 2b due to frequency fluctuations caused by the temperature of the local oscillation circuit 8. The signals are shifted in parallel by the frequency fluctuation Δ of the local oscillation circuit 8. Therefore, a signal of ₂ may be received as a signal of ₃ or ₁ , resulting in incorrect information. Therefore, in order to eliminate the influence of frequency fluctuations due to temperature etc. of the local oscillation circuit 8, as shown in FIG.
It is necessary to modulate the harmonic wave signal with the signal and then demodulate it again on the receiving side. Furthermore, it is necessary to widen the reception bandwidth in consideration of temperature fluctuations in the local oscillation frequency. Therefore, it had the following problems. Since the receiving bandwidth becomes wider than necessary, the S/N ratio of the demodulated output deteriorates. As a result, the limit level at which information can be deciphered deteriorated, and there was also a limit to the communication distance. Purpose of the Invention An object of the present invention is to eliminate the adverse effects of temperature fluctuations in local oscillation frequency on reception performance in a receiving device that performs data communication, and to narrow the reception bandwidth to the required bandwidth of the reception signal. , thereby providing a receiving device that can improve S/N. Configuration of the Invention A receiving apparatus according to the present invention includes a frequency analysis circuit that analyzes the frequency of an information signal including a reference frequency, and a local oscillation circuit that is controlled by a signal from the frequency analysis circuit. According to this configuration, even if the local oscillation frequency fluctuates due to a change in the ambient temperature of the receiving device, the reference frequency is detected by the frequency analysis circuit, and the reference frequency is detected near the center of the reception band by controlling the local oscillation circuit. Since the reference frequency is placed at Therefore, the S/N ratio can be improved and the communicable distance can be expanded. DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 3 shows a block diagram of a transmitting/receiving device in one embodiment of the present invention. Third
In the figure, A is a transmitting device and B is a receiving device. Transmission circuit A includes input circuit 1 and tone generation circuit 1
5, high frequency oscillation circuit 16, frequency conversion circuit 17,
It has a transmitting circuit 4 and a transmitting antenna 5. On the other hand, receiving device B includes a receiving antenna 6, a high frequency amplification circuit 7,
Local oscillation circuit 8, frequency conversion circuit 9, intermediate frequency amplification circuit 10, local oscillation circuit 18, frequency conversion circuit 19, frequency analysis circuit 20, information decoding circuit 21,
It has an output circuit 14. Components having the same functions as those of the conventional example shown in FIG. 1 are given the same numbers. The operation of the transmitter/receiver of this embodiment configured as described above will be described below. First, the transmitter will be explained. An input circuit 1 consisting of a numeric keypad or the like is operated to input information. The function of the tone generating circuit 15 will be explained based on FIG. FIG. 4a is a spectrum diagram of frequencies that can be generated by the tone generator 15. 4b to 4e are output diagrams showing frequency sequences output from the tone generator 15. FIG. The tone generating circuit 15 includes, for example, oscillators 15a, 15b, 15c, 15d, which generate frequencies from _-o/2 to _-o/2 in FIG. 4a.
...and it's coming from switch 15e. The function of the tone generation circuit 15 is fundamentally different from that of the conventional tone generation circuit 2 _.
, and the information corresponds to the difference from the reference frequency ₀ . Table 1 shows an example of the relationship between information and frequency difference.

[Table] In Figure 4 a, n = 10 (hereinafter n
= 10), we are considering numerical information from 0 to 9 as information. An example of the output of the tone generating circuit 15 is shown in FIG. 4b. First, the reference frequency ₀ is output, and then a frequency sequence containing information is output. In the example of Figure 4b, from Table 1, the number 3
→ Information is sent in the order of number 8 → number 9 → number 4. The signal shown in FIG. 4b is converted into a high frequency signal by the frequency conversion circuit 17, amplified by the transmitting circuit 4, and transmitted from the transmitting antenna 5 as an electromagnetic wave. Next, the receiving device will be explained. From the receiving antenna 6 to the center frequency amplification circuit 10
The operations up to this point are the same as in the conventional case. A frequency conversion circuit 19 converts the output of the intermediate frequency amplification circuit 10 to an even lower frequency. This frequency conversion circuit 19 is for converting a signal into a frequency band that can be easily processed by the frequency analysis circuit 20, and may be omitted. The output of the frequency conversion circuit 19 has a spectrum obtained by shifting the spectrum shown in FIG. 4a in parallel on the frequency axis. However, there is no change in the frequency difference between each spectrum. Now, the frequency analysis circuit 20 is composed of a group of filters 20a, 20b, . . . for decomposing the signal from the frequency conversion circuit 19 into each spectrum. The signal shown in FIG.
A signal with a frequency corresponding to ₀ is passed through the filter group 20a,
The signal is output from one of the filters 20b, . . . and input to the information decoding circuit 21. The information decoding circuit 21 recognizes the first input signal as the reference frequency signal ₀ , and controls the local oscillation circuit 8 so that the reference frequency ₀ comes to the center of the intermediate frequency amplification circuit 10. Then, depending on which filter the next signal comes from, the standard frequency _{is 0.}
The output circuit 14 is driven by determining the frequency difference between the two. FIG. 5 is a block diagram showing an example of the structure of the frequency analysis circuit 20, and FIGS. 6a and 6b are functional explanatory diagrams of the frequency analysis circuit 20. Consider the case where the reference frequency ₀ is input as shown in FIG. 6b. At this time, it is assumed that the reference frequency ₀ is at the right end of the band of the filter 20a. Now, if there is no temperature fluctuation in the local oscillation frequency, etc., it is assumed that ₀ is originally at the center of the filter 20e. When the reference frequency ₀ is input, the filter 20a is generated and the local oscillation circuit 8 is controlled so as to change the main body reference frequency by a frequency difference 4 between it and the filter 20e which should output it. Therefore, after the local oscillation circuit 8 is controlled, the reference frequency
₀ is at the right end of the filter 20e. The frequency difference calculation described above can be easily performed using, for example, a microcomputer. Further, the local oscillation circuit 8 may be controlled by, for example, constructing the local oscillation circuit using a variable capacitance diode and applying a DC voltage according to the frequency difference to the variable capacitance diode. Then, as shown in FIG. 5, the filter group 2 is centered around the filter 20e, and the filter group 1 is centered around the filter 20b. It is determined that the signal is Δ. In this way, errors in discrimination can be prevented and the bandwidth of each filter can be narrowed, so the S/N ratio can be improved and the level of information decoding can be lowered. In this example, three filters are used as one group, but by narrowing the bandwidth of each filter and increasing the number of filters in one group, the S/N can be further improved, even at a lower level. Information can be deciphered. As described above, according to this embodiment, the reference frequency _{is 0.}
Since the local oscillation circuit 8 is controlled so that the reference frequency ₀ is at the center of the intermediate frequency amplification circuit 10, information is lost due to frequency fluctuations such as the local oscillation frequency. There is no need to widen the reception bandwidth in consideration of temperature fluctuations, etc. This allows the bandwidth on the receiver side to be extremely narrowed, making it possible to significantly improve the S/N ratio and expand the communicable distance. Next, other embodiments of the present invention will be described with reference to the drawings. FIG. 7 shows a block diagram of a transmitting/receiving device according to another embodiment of the present invention. In FIG. 7, A is a transmitting device and B is a receiving device. Blocks having the same functions as those in the embodiment of FIG. 3 are given the same numbers. The transmitting device A has an input circuit 1 and a tone generating circuit 15.
This tone generation circuit 15 is composed of a D/A converter 22, a high frequency oscillation circuit 24, and a variable capacitance diode 23. The transmitting circuit A is a transmitting circuit 4,
It has a transmitting antenna 5. On the other hand, the receiving device B includes a receiving antenna 6, a high frequency amplification circuit 7, a local oscillation circuit 8, a frequency conversion circuit 9, an intermediate frequency amplification circuit 10,
Local oscillation circuit 18, frequency conversion circuit 19, A/D
It has a converter 25, a frequency analysis circuit 20, and an information decoding circuit 21. Here, the frequency analysis circuit 20 and the information decoding circuit 21 are composed of a microcomputer 26. Further, the receiving device B has an output circuit 1
It has 4. Next, the operation will be explained. Digital information from the input circuit 1 is input to a D/A converter 22 that constitutes the tone generation circuit 15, and is converted into an analog quantity. The capacitance value of the variable capacitance diode 23 is controlled by the analog amount, and the high frequency oscillation frequency of the high frequency oscillation circuit 24 is controlled. When a ten key switch or the like is operated, the input circuit 1 first outputs a digital signal with a reference frequency of ₀ , and then outputs a digital signal corresponding to the input information. The digital signal is converted into an analog quantity by the D/A converter 22, and the high frequency oscillation frequency of the high frequency oscillation circuit 24 is changed in accordance with the information. D/A
Since the analog quantity that is the output of the converter 22 changes stepwise in accordance with the information, the high frequency oscillation circuit 24
The spectrum and output of the high frequency oscillation frequency are as shown in FIGS. 4a and 4b. The signal shown in FIG. 4b is amplified by the transmitting circuit 4 and sent out from the transmitting antenna 5 as an electromagnetic wave. Next, the operation of the receiving device will be explained. The output of the frequency conversion circuit 19 is A/
The D converter 25 converts the input analog signal into a digital signal, the frequency analysis circuit 20 performs frequency analysis using a method such as a Fourier transform method, and the analysis result is sent to the information decoding circuit 21 . The information decoding circuit 21 first decodes the signal corresponding to the reference frequency ₀ , outputs a signal that controls the oscillation frequency of the local oscillation circuit 8, and outputs a signal that controls the oscillation frequency of the local oscillation circuit 8. Controls the oscillation frequency of the circuit 8. Next, the frequencies _-2 → ₄ → _o/2 → _-1 that are sent sequentially thereafter are analyzed, and the information decoding circuit 21 determines the difference from the reference frequency ₀ , and drives the output circuit 14. By configuring the oscillation frequency of the local oscillation circuit 8 to be controlled in this way, it is possible to provide a receiving device that is resistant to frequency fluctuations due to temperature changes and the like. In the above embodiment, the output of the tone generating circuit 15 was explained in the form shown in FIG. 4B, but the signal forms shown in FIGS. FIG. 4c shows a configuration in which a reference frequency is inserted between frequencies for transmission. Figure 4 d is a frequency that deviates from the reference frequency ₀ by, for example, -2Δ.
_-2 is sent, and then a signal of frequency ₂ , which is shifted by a distance of 2Δ and whose sign is reversed, is sent. Figure 4 e
For example, after sending frequency _-2 that is shifted by -2Δ from the reference frequency ₀ , the frequency _-2 is shifted by (n/2+1)Δ
This is a form of sending a signal with a frequency _o/2-1 that is shifted by a distance of . Figure 4 f uses two types _of reference frequencies, ₁ and _{-1 .}
The signal format after is the same as in FIG. 4e. Furthermore, the signal form is shown in Fig. 4 b to f.
The present invention is not limited to this, but any signal format may be used as long as it first transmits a reference frequency and then transmits a signal containing information. For example, signals of several frequencies may be transmitted temporally in parallel, or the reference frequency may be sent again at the very end to indicate the end of communication. Further, the signal after the reference signal may be an FM modulated signal. In short, it is only necessary to detect the reference frequency and control the local oscillation circuit so that the reference frequency is located near the center of the intermediate frequency amplification circuit. The controlled local oscillator circuit is
Either circuit 8 or circuit 18 may be used.
Note that the frequency analysis circuit 20 may be configured with an analog filter, a digital filter, or one using a Fourier transform method. Effects of the Invention As is clear from the above description, the present invention first transmits a signal at a reference frequency, then transmits a signal containing information, detects the first reference frequency by a frequency analysis circuit in a receiving device, and Since the oscillation circuit is controlled so that the reference frequency is near the center of the band of the intermediate frequency amplification circuit, the influence of temperature fluctuations on the local oscillation frequency can be eliminated, and the bandwidth of the intermediate frequency amplification circuit is can be minimized and the S/N ratio can be improved.
This has the excellent effect of making it possible to decode information even in places where the electrolytic strength is weak. As a result, the communicable distance can be dramatically extended.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional transmitter/receiver;
The figure is a functional explanatory diagram of the tone generation circuit of the same device.
4 is a functional explanatory diagram of a tone generation circuit of the transmitting and receiving device in an embodiment of the present invention. FIG. 5 is a block diagram of a transmitting and receiving device in an embodiment of the present invention. A configuration diagram of the frequency analysis circuit of
The figure is a block diagram of a transmitting/receiving device in another embodiment of the present invention. 1...Input circuit, 2...Tone generation circuit, 3...
...FM modulation circuit, 4...Transmission circuit, 5...Transmission antenna, 6...Reception antenna, 7...High frequency amplification circuit, 8...Local oscillation circuit, 9...Frequency conversion circuit, 10...Intermediate frequency Amplification circuit, 11... FM demodulation circuit, 12... Frequency analysis circuit, 13... Information decoding circuit, 14... Output circuit, 15... Tone generation circuit, 16... High frequency oscillation circuit, 17... Frequency conversion Circuit, 18... Local oscillation circuit, 19... Frequency conversion circuit, 20... Frequency analysis circuit, 21...
...Information decoding circuit, 22...D/A converter, 23...
...variable capacitance diode, 24...high frequency oscillation circuit, 25...A/D converter, 26...microcomputer.

Claims (1)

[Claims] 1 A receiving device that receives a signal including at least a reference frequency, which is controlled by a frequency analysis circuit that analyzes the frequency of the received signal, an information decoding circuit that receives the signal from the frequency analysis circuit, and the information decoding circuit. The reference frequency is detected by a frequency analysis circuit and an information confirmation circuit, and the local oscillation circuit is controlled based on the detection result to set the reference frequency near the center of the reception band. A receiving device characterized in that it is configured to receive a frequency.