JPH063946B2 - Receiver - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver that can be used for data communication.

Configuration of Conventional Example and Problems Thereof In recent years, mobile communication services such as pagers and car phones have become popular. In the above mobile communication, a transmission / reception device is used which is accompanied by data transmission of identification information such as a dial number of its own station or a partner station.

A conventional transmitting / receiving apparatus will be described below with reference to the drawings. FIG. 1 is a block diagram of a conventional transceiver.
In FIG. 1, I indicates a transmitter and II indicates a receiver. The transmitting device I has a tone generating circuit 2 which generates a frequency corresponding to information from the input circuit 1 which is a ten-key pad or the like. The tone generating circuit 2 is composed of, for example, oscillator groups 2a, 2b, 2c, 2d ... Which generate different frequencies.
The switch 2e is switched according to the information from the input circuit 1,
It is configured to output a signal having a frequency corresponding to information. Further, the transmitting device I has an FM modulating circuit 3, a transmitting circuit 4, and a transmitting antenna 5. On the other hand, the receiver II has a receiving antenna 6, a high frequency amplifier circuit 7, a local oscillator circuit 8, a frequency conversion circuit 9, an intermediate frequency amplifier circuit 10, an FM demodulation circuit 11, and a frequency analysis circuit 12. The frequency analysis circuit 12 is composed of filters 12a, 12b .... Further, the receiving device II has an information decoding circuit 13 and an output circuit 14 composed of a buzzer, a display or the like.

The operation of the transmitter / receiver configured as described above will be described below. When the input circuit 1 including a numeric keypad is operated to input information, a signal having a frequency corresponding to the input information is output from the tone generation circuit 2 and a high frequency signal is output from the tone generation circuit 2 by the FM modulation circuit 3. The signal is frequency-modulated, the transmission circuit 4 amplifies it, and the transmission antenna 5
More electromagnetic waves are transmitted. The function of the tone generating circuit 2 will be described in more detail with reference to FIG. Fig. 2
(a) is a spectrum diagram of frequencies that can be generated by the tone generating circuit 2. FIG. 2b shows the tone generation circuit 2
It is an output figure which shows the frequency series output from. FIG. 2a shows that there are n oscillators 2a, 2b ... In total. The oscillation frequencies of the oscillators 2a, 2b ... Are f ₁ , f ₂
……… It is f _n . The signals of these oscillation frequencies are switched by the switch 2e according to the information from the input circuit 1
It is output at the time interval shown in FIG. That is, the frequency switches every time T. Now, if the number n of oscillation frequencies is 10, then the numbers 0 to 9 can be associated with f ₁ to f ₁₀ , respectively, and if 4 frequencies are sent as shown in FIG. You can send numbers. Next, the receiving device will be described. In FIG.
The electromagnetic wave input to the receiving antenna 6 is selectively amplified by the high frequency amplifier circuit 7, converted to an intermediate frequency by the frequency conversion circuit 9, further selectively amplified by the intermediate frequency amplifier circuit 10, and FM
The demodulated circuit 11 demodulates the frequency-converted signal, and outputs the signal of the frequency sequence shown in FIG. The frequency analysis circuit 12 includes n filters 12a, 1 for selectively separating n frequencies of frequencies f ₁ , f ₂ ... F _n.
It consists of 2b ... From the filter 12a, f
Only the signal of _{1 and} the signal of f ₂ are taken out from the filter 12b. The information decoding circuit 13 determines the order and the frequency of the signals from the frequency analysis circuit 12, and drives the output circuit 14 such as a buzzer or a display.

However, in the above configuration, since the frequency modulation circuit is used, if the C / N of the receiver input deteriorates to some extent, the S / N of the demodulation circuit output starts to rapidly deteriorate, a so-called threshold point. Existed and was not practical at input levels below this.
Further, it is necessary to widen the reception bandwidth considering the temperature fluctuation of the local oscillation frequency. Therefore, it had the following problems. Since the reception bandwidth becomes wider than necessary, the S / N of the demodulation output deteriorates. Therefore, the limit level at which information can be decoded deteriorates, and the communication distance is also limited.

An object of the present invention is to provide a receiving device for performing data communication,
To provide a receiving device capable of preventing deterioration of reception performance due to temperature fluctuation of a local oscillation frequency, narrowing a reception bandwidth to a required bandwidth of a reception signal, and improving S / N. is there.

The receiver according to the present invention is a receiver for receiving a signal including preset reference frequency information near the center of a frequency band used for information transmission, and a local oscillating circuit for determining a receiving frequency. A frequency analysis circuit for frequency-analyzing the received signal, the center frequency of analysis being changeable by control, and an analysis frequency control circuit for controlling the frequency analysis circuit,
The signal from the frequency analysis circuit is input, and the information transmitted from the frequency sequence obtained as a result of the frequency analysis is controlled while controlling the local oscillation circuit based on the difference between the frequency of the signal received at the start of signal reception and the reference frequency. It has an information decoding circuit for decoding.

According to such a configuration, even if the local oscillation frequency of the receiving device fluctuates due to a change in ambient temperature, the signal corresponding to the reference frequency is detected by the frequency analysis circuit and the information decoding circuit, and the local portion is detected based on the detection result. By controlling the oscillator circuit and frequency analysis circuit, the reference frequency is configured to come near the center of the reception band.
It is not necessary to widen the reception bandwidth in consideration of temperature fluctuation, and the band can be narrowed. Therefore, the S / N can be improved, and thus the communicable distance can be expanded.

Description of Embodiments Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram of a transmitter / receiver according to an embodiment of the present invention. In FIG. 3, A is a transmitter and B is a receiver. The transmission circuit A includes an input circuit 1, a tone generator 15, a high frequency oscillation circuit 16, a frequency conversion circuit 17, a transmission circuit 4, and a transmission antenna 5. On the other hand, the receiving device B includes a receiving antenna 6, a high frequency amplifier circuit 7,
It has a local oscillation circuit 8, a frequency conversion circuit 9, an intermediate frequency amplification circuit 10, a local oscillation circuit 18, a frequency conversion circuit 19, a frequency analysis circuit 20, an information decoding circuit 21, an analysis frequency control circuit 22, and an output circuit 14. The same numbers are given to those having the same functions as those of the conventional example shown in FIG. The operation of the transmission / reception device of this embodiment configured as described above will be described below. First, the transmitter will be described. Information is input by operating the input circuit 1 including a numeric keypad. The function of the tone generator 15 will be described with reference to FIG. FIG. 4a is a frequency spectrum diagram that can be generated by the tone generator 15. Fig. 4b
5e are output diagrams showing examples of frequency sequences output from the tone generator 15. FIG. The configuration of the tone generator 15 is, for example, oscillators 15a, 15b, 15c, 15d ... Which generate respective frequencies from f _{−n / 2} to f _{n / 2 in} FIG. 4a.
... and a switch 15e. Tone generator 1
5 is basically different from the function of the conventional tone generating circuit 2 in that it has a preset reference frequency f ₀ in the vicinity of the center of the frequency band used for information transmission, and the information is stored at the reference frequency f. It is defined in relation to ₀ . The table shows an example in which information is defined in relation to the frequency difference from the reference frequency.

However, in FIG. 4a, the intervals between adjacent frequencies are all Δf. In FIG. 4a, the case is n = 10 (hereinafter, treated as n = 10), and numbers 0 to 9 are given as information. Fourth example of output of tone generator 15
Shown in Figure b. First, the reference frequency f ₀ is output for a time necessary and sufficient for performing operations such as frequency analysis and frequency correction of the local oscillator on the receiving side, and then a frequency string containing information is also required for frequency analysis. Output only time. In the example of FIG. 4b, from the table, the numeral 3 → the numeral 8 →
The information is transmitted in the order of number 9 (fn / 2 = f ₅ when n = 10) → number 4. Fourth
The signal of FIG. B is converted into a high frequency signal by the frequency conversion circuit 17, amplified by the transmission circuit 4, and transmitted from the transmission antenna 5 as an electromagnetic wave. Next, the receiving device will be described.
The operation from the receiving antenna 6 to the intermediate frequency amplifier circuit 10 is the same as the conventional case. The output of the intermediate frequency amplifier circuit 10 is converted to a lower frequency by the frequency conversion circuit 19. The frequency conversion circuit 19 includes a frequency analysis circuit 20.
The signal is converted to a frequency band that can be easily processed by
Set the conversion frequency as required. Frequency conversion circuit 19
Is an output having a spectrum obtained by moving the spectrum of FIG. 4a in parallel on the frequency axis. Therefore, there is no change in the frequency difference of each spectrum. Now, the frequency analysis circuit 20 has filter groups 20a, 20b ... For separating the signal from the frequency conversion circuit 19 into each spectrum.
It consists of ... Here, the filter groups 20a and 20b
.. is further composed of a plurality of filters as shown in FIG. 5, each of which is (20a ₁ , 20a ₂ , 20a
₃ ...), (20b ₁ , 20b ₂ , 20b ₃ ...), (2
0c ₁ , 20c ₂ , 20c ₃ ...) .... The signal of FIG. 4b is input to the frequency analysis circuit 20 in a frequency-converted form, and when the signal corresponding to the reference frequency f ₀ arrives first, the filter groups 20a, 20
An output starts to be output from a filter in one of the filter groups b, 20c, .... In the case of an original signal, since a signal required for frequency analysis is transmitted, it is output as signal detection from the filter after the time constant required for detection and input to the information decoding circuit 21. Information decoding circuit 21
Is a signal corresponding to the reference frequency from the above-mentioned input signal f
₀ , first, the local oscillator circuit 8 is controlled so that the received signal comes near the center of the band of the intermediate frequency amplifier circuit 10.
Next, the filter group of the frequency analysis circuit 20 is rearranged by the analysis frequency control circuit 22 so that a signal corresponding to the reference frequency is obtained as an output from the filter at the center of the filter group, and the intermediate frequency amplification circuit 10
The received signal is made to come to the center of the filter group near the center within the band. A more detailed description will be given with reference to FIGS. 6 and 7. First, when the receiving device shown in FIG. 3B, in which the oscillation frequency of the local oscillation circuit 8 is controlled so that the reference frequency f ₀ becomes the center of the intermediate frequency amplification circuit 10, receives the signal, the local oscillation circuit 8 When the oscillation frequency fluctuates due to temperature fluctuation or the like, as shown in FIG. 6A, the band of the intermediate frequency amplifier circuit 10 and the frequency band for information transmission are deviated.

The filter group 20 is arranged within the band of the intermediate frequency amplifier circuit 10 as shown in FIG. 6b. When the receiving device has such a shift, the frequency analysis circuit 2 outputs a signal corresponding to the reference frequency f ₀ that arrives when signal reception is started.
0 is obtained as an output from one filter group of the filter groups 20a, 20b, ...
To the reference frequency f ₀ .

In this case, the output is not from the filter group near the center of the intermediate frequency amplifier circuit 10, but from the filter group located off the center as shown in FIG. 6c.

With this as the reference frequency f ₀ , the oscillation frequency of the local oscillation circuit 8 is controlled, and the signal corresponding to the reference frequency f ₀ is given in FIG.
As shown in FIG. 5, the intermediate frequency amplifier circuit 10 is set to come near the center of the band.

By doing so, the filter group of the frequency analysis circuit 20 can correct the parallel movement of the spectrum on the frequency axis due to the temperature change of the local oscillation frequency. The filter groups 20a, 20b ... Are arranged on the frequency axis as shown in FIG. 7a. By controlling the local oscillation circuit 8, the reception band can be translated in parallel on the frequency axis, and the filter group and the reception band can be roughly matched.
Next, the analysis frequency control circuit 22 is arranged so that f ₀ corresponding to the reference frequency comes to the center of the filter group near the center of the reception band.
The filter group is rearranged by, for example, after controlling the local oscillation circuit 8, a signal corresponding to the reference frequency received after the local oscillation frequency correction is output from 20b _{3 of the} filter group 20b as shown in FIGS. lever, the received signal to the filter 20 'b ₂ as shown in FIG c controls the frequency analysis circuit 20 to come. That is, the filter 20b ₃ before the control, after control is treated as a filter 20 'b ₂ of the center of the filter group 20' b. Then, the information decoding circuit 21 obtains the information by determining the relationship with the reference frequency f ₀ , for example, in the case of a table, by determining the frequency difference, depending on which filter group the next signal comes from, and the output circuit 1
Drive 4 Now, in the frequency analysis circuit 20, the frequency f ₋₁ of the difference between the reference frequency f ₀ and −Δf as shown in FIG.
Consider the case where is input sequentially. At this time, the reference frequency f ₀
Is at the left end of the band of the filter 20b _{2 at} the center of the filter group 20b, when the frequency f ₋₁ is input next, f ₋₁ comes to the left end of the band of the filter 20a _{2 at} the center of the filter group 20a. However, the filter bandwidth, center frequency, etc. slightly change due to changes in temperature, etc., and as shown in FIGS. 8A and 8B, f is added to the right end of the band 20a ₁ in the filter group 20a. It may be detected as ′ ₋₁ . However, as shown in FIG. 5, since a plurality of filters are grouped together and one frequency is assigned, the filter group 20a having a frequency difference of −Δf is selected, and there is no error in signal discrimination. . Also,
According to the present embodiment, since the frequency drift is automatically corrected, the filter of the frequency analysis circuit 20 shown in FIG. 5 can be narrower in band than the filter of the frequency analysis circuit 12 shown in FIG. Can be improved. Therefore, the input signal level required to decode the information can be further lowered. Although the filter group shown in FIG. 5 constitutes one group with three filters, if the bandwidth of each filter is narrowed and the number of filters in one group is increased, the S / N ratio is further increased. It enables improvement and decoding of information at a lower level, increasing the communication range. The local oscillator circuit 8 may be controlled by using a variable capacitance diode as the local oscillation circuit and applying a DC voltage to the variable capacitance diode according to the frequency difference between the frequency of the incoming signal and the reference frequency. Good. Further, in FIG. 5, the filter 20a
Filter group 20a around the _2, although classified filter group 20b around the filter 20b _2, information decoding circuit 2
At 1, the frequency analysis circuit 20 can be controlled by controlling the arrangement of the group and the center filter. For example, if a signal is present in the filter 20a ₃ , the filter group 20
The center of a is 20a _3, and 20a ₂ , 20a ₃ , 20a
₁ may be defined as the constituent filter. According to this embodiment, as described above, the reference frequency difference between f ₀ transmitted as information, and the reference frequency f ₀ is the center frequency amplifier circuit the local oscillation circuit 8 and the frequency analyzing circuit 20 to center of 10 Since it is controlled, it is not possible to receive information due to the influence of the fluctuation of the local oscillation frequency, and it is not necessary to widen the reception bandwidth even for temperature fluctuations. As a result, the bandwidth on the receiver side can be made very narrow, the S / N can be greatly improved, and the communicable distance can be expanded.

Next, another embodiment of the present invention will be described with reference to the drawings. FIG. 9 shows a block diagram of a transmitting / receiving apparatus in another embodiment of the present invention. In FIG. 9, A is a transmitter and B is a receiver. The same numbers are given to blocks having the same functions as those in the embodiment of FIG. The transmitter A has an input circuit 1 and a tone generator 35. The tone generator 35 includes a D / A converter 23, a high frequency oscillation circuit 25, and a variable capacitance diode 24. The transmitter A has a transmitter circuit 4 and a transmitter antenna 5. On the other hand, the receiving device B includes a receiving antenna 6, a high frequency amplifier circuit 7, a local oscillation circuit 8, a frequency conversion circuit 9, an intermediate frequency amplification circuit 10, a local oscillation circuit 18, a frequency conversion circuit 19,
A / D converter 26, analysis unit 2 having a frequency analysis function
8. An information decoding unit 29 having an information decoding function and an analysis frequency control unit 30 having an analysis frequency control function are included.

Here, the frequency analysis unit 28, the information decoding unit 29, and the analysis frequency control unit 30 are composed of a microcomputer 27. Further, the receiving device B has an output circuit 14. Next, the operation will be described. The digital information from the input circuit 1 is input to the D / A converter 23 which constitutes the tone generator 35 and converted into an analog quantity. The capacitance value of the variable capacitance diode 24 is controlled by the analog amount,
The high frequency oscillation frequency of the high frequency oscillator circuit 25 is controlled. When the numeric keypad switch is operated, the input circuit 1
First, the digital signal of the reference frequency f ₀ is output,
Then, a digital signal corresponding to the input information is output.
The digital signal is converted into an analog quantity by the D / A converter 23, and the high frequency oscillation frequency of the high frequency oscillation circuit 25 is changed according to the information. Since the analog quantity output from the D / A converter 23 changes stepwise in accordance with the information, the spectrum and output of the high frequency oscillation frequency of the high frequency oscillation circuit 25 are as shown in FIGS. 4A and 4B. The signal shown in FIG. 4b is amplified by the transmission circuit 4 and transmitted as an electromagnetic wave from the transmission antenna 5. Next, the operation of the receiver B will be described. The output of the frequency conversion circuit 19 is the A / D converter 26.
Is converted into a digital signal according to the input analog signal by the frequency analysis unit 28 included in the microcomputer.
Then, frequency analysis is performed by a method such as the Fourier transform method, and the analysis result is sent to the information decoding unit 29. The information decoding unit 29 first controls the oscillation frequency of the local oscillation circuit 8 when a signal corresponding to the reference frequency f ₀ is obtained, and controls the filter group of the frequency analysis unit 28. As a result, the filter group in the frequency analysis unit 28 is rearranged by the analysis frequency control unit 30 after the center of the analyzable frequency band of the frequency analysis unit 28 is reached. After the arrival of the reference frequency f ₀ , the frequencies f ₋₂ → f ₄ → f _{n / 2} → fn / 2, which are sequentially transmitted thereafter as shown in FIG.
The information decoding unit 29 discriminates the difference from the reference frequency f ₀ and drives the output circuit 14. By thus controlling the oscillation frequency of the local oscillation circuit 8 and the rearrangement of the filter of the frequency analysis unit 29, it is possible to obtain 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 generator 35 is described in the form of FIG. 4b.
The signal forms shown in FIGS. C to e may be used. Fig. 4c
Is a form in which the reference frequency f ₀ is inserted between the frequencies of the information and the information is transmitted. In FIG. 4d, after the frequency f _−n deviated from the reference frequency f _{0 by} −nΔf is transmitted, In this mode, a signal of f _n shifted by the inverted distance nΔf is transmitted. FIG. 4e shows 2 of f ₁ and f ₋₁ as reference frequencies.
It uses types. The signal form after the reference frequencies f ₁ and f ₋₁ are the same as in FIG. 4c. Further, the signal form is not limited to b to e in FIG. 4, and the point is that the signal form is such that the reference frequency is first transmitted and then the signal containing information is transmitted. For example, signals of several kinds of frequencies may be transmitted in parallel in time, or the reference frequency may be sent again at the end for the purpose of ending communication. The controlled local oscillation circuit may be either the circuit 8 or the circuit 18. The frequency analysis unit 28 may be a Fourier transform by a program of the microcomputer 27, or may be an externally connected analog or digital filter group.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, the reference frequency is first transmitted, and then the signal containing the information is transmitted, and the first reference frequency is detected by the frequency analysis circuit in the receiving device, and the local oscillation is performed. Control circuit and frequency analysis circuit,
Since the reference frequency is located near the center of the band of the intermediate frequency amplifier circuit, it is possible to eliminate the influence of temperature fluctuations of the local oscillation frequency, and to minimize the bandwidth of the intermediate frequency amplifier circuit. It is possible to obtain an excellent effect that the S / N is improved and the information can be decoded even in a place where the electric field strength is weak. As a result, the communicable distance can be dramatically increased.

[Brief description of drawings]

FIG. 1 is a block diagram of a conventional transmitter / receiver, FIG. 2 is a functional explanatory diagram of a tone generation circuit of the same, FIG. 3 is a block diagram of a transmitter / receiver in one embodiment of the present invention, and FIG. FIG. 5 is a functional explanatory diagram of a tone generating circuit of a transmitter / receiver in one embodiment of the present invention, FIG. 5 is a block diagram of a frequency analysis circuit of the transmitter / receiver in one embodiment of the present invention, and FIG. 6 is a transmitter / receiver in one embodiment of the present invention. 7 is a functional explanatory diagram relating to the control of the local oscillation circuit of FIG. 7, FIG. 7 is a functional explanatory diagram relating to the control of the frequency analysis circuit of the transmitting / receiving device according to an exemplary embodiment of the present invention, and FIG. 8 is a frequency of the transmitting / receiving device according to the exemplary embodiment of the present invention. FIG. 9 is a block diagram of a transmission / reception 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 ...
Receiving 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 generator, 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 ... analysis frequency control circuit, 23 ... D / A converter, 24 ... variable capacitance diode, 25 ... high frequency oscillation circuit, 26 ... A / D conversion Instrument, 27 ... Microcomputer, 28 ... Frequency analysis section, 29 ... Information decoding section,
30 ... Analysis frequency control unit, 35 ... Tone generator.

Claims (2)

[Claims] 1. A receiving device for receiving a signal including preset reference frequency information in the vicinity of the center of a frequency band used for information transmission, comprising a local oscillating circuit for determining the receiving frequency and a frequency of the receiving signal. A frequency analysis circuit that analyzes and can change the center frequency of analysis by control, an analysis frequency control circuit that controls the frequency analysis circuit, and a signal received from the frequency analysis circuit as an input, and received at the start of signal reception. And the information decoding means for decoding the information transmitted from the frequency sequence obtained as a result of the frequency analysis while controlling the local oscillation circuit on the basis of the difference between the frequency and the reference frequency. It is detected by the frequency analysis circuit and the information decoding circuit, and based on the detection result, the local oscillation circuit and the frequency analysis circuit are controlled to center the reception band. A receiving apparatus, characterized in that the received signal is near. 2. The receiver according to claim 1, wherein the frequency analysis circuit is composed of a filter group.