JP2001148722A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a receiver which is composed of a small number of components and adaptive to a different transmission and reception system. SOLUTION: The FSK receiver is composed of a comparator 11, a delay unit 12, a multiplier 13, and a low-pass filter 14. The comparator 11 converts a received FSK-modulated signal into a digital signal of 1 or 0 on the basis of a specific level and outputs it and the output of the comparator 11 is inputted to a delay unit 13 and a multiplier 13. The delay unit 12 delays the input signal by a fixed time and outputs it and the delayed output signal from the delay unit 12 is also inputted to the multiplier 13. The multiplier 13 multiplies the output signal of the comparator 11 by the delayed output signal of the delay unit 12. The signal form the multiplier 13 is inputted to a low-pass filter 14 to cut its high-frequency component and then extracts its base-band signal. The receiver is usable even as an ASK receiver.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus for digital communication, and more particularly, to an FSΚ (Frequency Shift Ke
ying) and an ASK (Amplitude Shift Keying) modulated signal receiving apparatus.

[0002]

2. Description of the Related Art There has been a conventional receiving apparatus for receiving an FSΚ modulated signal configured as shown in FIG. Here, the FSK modulated signal input from the antenna 20 is supplied to a band-pass filter 21 that outputs only the component of the frequency f0 of the two carrier components, and a band-pass filter 22 that outputs only the component of the frequency fl. . A series circuit of rectifiers 23 and 24 and low-pass filters 25 and 26 is connected to each of the band-pass filters 21 and 22, and their output signals are compared by a magnitude judgment unit 27.

FIG. 3 is a waveform diagram showing an example of an FSK modulation signal. FIG. 3A shows a sine wave constituting a carrier component of the first frequency f0, and FIG. 3B shows a carrier component of a second frequency fl higher than the first frequency f0. It shows a sine wave. T indicates one cycle of the sine wave of the first frequency f0. FIG. 3C shows a baseband signal and a sine wave having frequencies f0 and fl that are switched and output according to a digital value of 0/1.
5 shows an SK modulation signal. Here, the baseband signals "1" and "0" are modulated into sine waves having frequencies f0 and fl, respectively.

FIG. 4 shows signal waveforms at various parts for explaining the operation of the receiving apparatus. When the FSΚ modulated signal shown in FIG. 3C is input to the band-pass filters 21 and 22 in FIG. 2, the output signals from the band-pass filters 21 and 22 are as shown in FIGS. 4A and 4B, respectively. Become. The output signal from the rectifier 23 has a signal waveform as shown in FIG. 3C, and the output signal from the rectifier 24 has a signal waveform as shown in FIG. However, full-wave rectifiers are used as the rectifiers 23 and 24, for example.

The low-pass filters 25 and 26 connected to the rectifiers 23 and 24 respectively include rectifiers 23 and 24
Is filtered to pass only the baseband signal component to the output signal from. As a result, low-pass filters 25 and 26 output signals from FIGS. 4E and 4F, respectively.
The envelope signal is as shown in FIG. These two envelope signal waveforms are compared by a magnitude determiner 27 and a low-pass filter 25 is used.
If the output signal is smaller than the output signal of the low-pass filter 26, a 1-level signal is output as the determination result. FIG. 4G shows an output signal of the magnitude judging device 27, which is demodulated as a digital signal equal to the baseband signal shown in FIG. 3C.

[0006]

However, in the receiving apparatus having the above-described structure, two each of them are required, such as the band-pass filters 21 and 22, the rectifiers 23 and 24, and the low-pass filters 25 and 26. . Therefore, when this kind of FS @ receiving apparatus is actually configured, there is a problem that the number of parts increases.

By the way, in addition to the above system for transmitting and receiving the FSＦ modulated signal, for example, 1 /
A transmission / reception system of an ASK modulation signal modulated by turning on / off the transmission of one kind of sine wave according to the value of 0 is also applied to digital communication. FIG.
Shows a baseband signal and an ASK modulation signal from which a sine wave of a predetermined frequency is output only when it is 1.

Since the ASK modulation signal receiving apparatus uses only one kind of sine wave as a carrier, the above-mentioned FSＦ
Unlike a receiving device that receives a modulated signal, the problem of an increase in the number of components has been solved. However, in any of the receivers of the ASK modulation and the FSΚ modulation, when the modulation index or the like of the input modulation signal changes, in order to maintain a predetermined reception sensitivity, the hardware of the band-pass filter is required. Configuration must be changed.

There is also a problem that the receiver once assembled is used only in one determined transmission / reception system.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a receiving apparatus which has a small number of components and can support different transmitting / receiving systems.

[0011]

According to a first aspect of the present invention, there is provided a receiving apparatus for receiving an FSK modulated signal modulated by switching a frequency of a carrier according to a 1/0 value of a baseband signal. A comparator for comparing the obtained FSK modulated signal with a predetermined reference level, converting the FSK modulated signal into a 1/0 digital signal, and outputting the digital signal; A multiplier for multiplying an output of the delay unit and an output of the delay unit to output an exclusive OR signal, and demodulating a baseband signal from the exclusive OR signal of the multiplier.

Further, in the receiving apparatus according to the present invention, the delay time of the delay unit is set to a half cycle of a low-frequency sine wave of the two sine waves received as the carrier wave or an odd multiple thereof. Can also be set.

Further, in the receiving apparatus according to the present invention, the FSK modulated signal uses two sine waves, one of which is set to an even multiple wavelength of the other, as a carrier.

According to a fourth aspect of the present invention, there is provided a receiving apparatus for receiving an ASK modulated signal modulated by turning on / off a carrier according to a 1/0 value of a baseband signal. A comparator for comparing with a reference level, converting the output signal to a 1/0 digital signal and outputting the digital signal, a delay device for delaying the output signal of the comparator by a fixed time and outputting the output signal, an output of the comparator and the delay device And a multiplier that outputs an exclusive OR signal by multiplying the output of the multiplier, and demodulates a baseband signal from the exclusive OR signal of the multiplier.

Further, in the receiving apparatus according to the present invention, the delay time of the delay unit can be set to a half cycle of a sine wave received as the carrier or an odd multiple thereof.

The receiving apparatus according to the present invention further includes a low-pass filter for removing a high-frequency component contained in the exclusive OR signal of the multiplier.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

Embodiment 1 FIG. 1 is a block diagram showing an FSK receiving apparatus according to Embodiment 1 of the present invention.
This FSΚ receiving device includes a comparator 11, a delay unit 12, a multiplier 13, and a low-pass filter 14. The comparator 11 converts the received FSK modulated signal into a 1/0 digital signal based on a predetermined reference level and outputs the digital signal.
The modulation signal and the corresponding reference level signal are input. The output signal of the comparator 11 is input to the delay unit 12 and the multiplier 13. The delay unit 12 delays the input signal for a predetermined time and outputs the delayed signal. The delayed output signal from the delay unit 12 is also input to the multiplier 13.

The multiplier 13 multiplies the output signal of the comparator 11 by the delayed output signal of the delay unit 12. The signal from the multiplier 13 is input to the low-pass filter 14, where the high-frequency component is cut to extract the baseband signal.

Next, the operation of the receiving apparatus will be described with reference to FIG.

FIG. 6A shows an FSK modulated signal input to the receiving device as an analog signal. This FSK modulated signal is modulated by switching the frequency of the carrier wave between f0 and f1 according to the 1/0 value of the baseband signal and outputting it. The comparator 11 has, for example, a 0 level,
That is, a signal having a reference level intermediate between the positive peak value and the negative peak value is input. Then, the comparator 11 compares the FSK modulation signal, which is an analog input signal, with the reference level signal, performs level conversion of the FSK modulation signal, and as shown in FIG. The signal is converted into a digital signal and output to the delay unit 12. The delay unit 12 outputs a digital signal delayed by a certain time from the digital signal from the comparator 11.

FIG. 6C shows a digital signal output from the delay unit 12. Here, the delay time of the delay unit 12 is set equal to a half cycle (T / 2) of the sine wave of the first frequency f0. The multiplier 13 multiplies the output signal from the comparator 11 by the output signal from the delay unit 12. However, the operation of multiplying these digital signals is an exclusive OR (EX-OR) operation.

FIG. 6D shows an ideal output signal waveform from the multiplier 13. If the relationship between the frequencies f0 and fl is fl = 2 × f0, and the delay time of the delay unit 12 is set to a half cycle of the sine wave of the first frequency f0, the output from the multiplier 13 becomes As shown in FIG. 6D, a digital signal waveform corresponding to the 1/0 value of the baseband signal is obtained. Therefore, in principle, the digital signal of the multiplier 13 can be directly output as a baseband signal.

However, in reality, the accuracy of the delay unit 12 is low, or the FS
Κ A discontinuous point may occur in the modulated signal, and the actual output signal waveform of the multiplier 13 is, as shown in FIG.
A pulse signal having a narrow width is included. Therefore, a low-pass filter 14 for removing high-frequency components included in the exclusive OR signal is connected to the output side of the multiplier 13. The low-pass filter 14 filters the exclusive OR signal to pass only the baseband signal component to remove a narrow pulse signal.
A baseband signal as shown in FIG.

In the above-described FSK receiving apparatus, the phase difference (delay time) between the output signal from the comparator 11 and the output signal from the delay unit 12 is determined by the half period (T) of the sine wave of the first frequency f0. / 2) is desirable. However, the delay time of the delay unit 12 may be an odd multiple of a half cycle of the sine wave of the first frequency f0. Also, the frequency f
The relationship between 0 and fl does not necessarily have to be fl = 2 × f0. Generally, two frequencies f1 and f2 are
If there is a relationship of fl = 2n × f0 (n = 1, 2, 3,...), a digital signal waveform corresponding to the 1/0 value of the baseband signal as shown in FIG. it can.

As described above, according to the FSK receiving apparatus of the first embodiment, an FSΚ modulated signal can be received only by having one comparator, one delay unit, one multiplier, and one low-pass filter. Therefore, the number of components can be reduced as compared with the conventional receiving device.

In the conventional receiving apparatus, the output is processed as an analog signal until the output of the two low-pass filters 25 and 26 is compared in the magnitude judging device 27. However, in this FSK receiving apparatus, a comparator to which a received FSK modulated signal is input first converts an analog input signal into a digital signal and processes the digital signal. The delay time can easily be changed. For example, a circuit configuration corresponding to a comparator, a delay unit, and a multiplier is replaced with a PLD (Programmable Logic).
If the delay time and the like are rewritten by using a digital circuit such as a device, the transmission / reception system having a different modulation index can be supported without changing the hardware.

Embodiment 2 Embodiment 1 has described an example in which the receiving apparatus shown in FIG. 1 is used as an FSK receiving apparatus. In the second embodiment, the receiving apparatus shown in FIG.
The operation in the case of using as an SΚ receiving device will be described. However, it is necessary to change the reference level of the comparator 11 as described below.

Here, the signal waveform in each block when the {S} modulated signal is first received by the receiving apparatus of FIG. 1 will be described.

FIG. 8A is a diagram showing an example of a baseband signal and its ASΚmodulated signal. In the ASΚ modulation, a sine wave signal having a frequency f0 is output when the baseband signal is “1”, and such a sine wave signal is not output when the baseband signal is “0”. Therefore, when this ASΚmodulated signal is input to the receiving apparatus of FIG. 1, the comparator 11 outputs “0”.
By inputting a reference level signal slightly higher than the level, a digital signal as shown in FIG. Here, T indicates one cycle in the sine wave signal of the frequency f0.

Next, in the delay unit 12, the comparator 11
And outputs a digital signal delayed by a certain time with respect to the digital signal from. In FIGS. 9A and 9B,
The output signal from the comparator 11 and the output signal from the delay unit 12 are shown. The delay time of the delay unit 12 is set equal to a half wavelength (T / 2) of a sine wave having a frequency f0.

The multiplier 13 multiplies the output signal from the comparator 11 by the output signal from the delay unit 12. The multiplication operation of these digital signals is an EX-OR operation,
FIG. 9C shows an ideal output signal waveform from the multiplier 13. Here, since the delay time of the delay unit 12 is a half wavelength (T / 2) of a sine wave of the frequency f0, the digital signal output of the multiplier 13 can be output as a baseband signal in principle.

However, in reality, the waveform of the actual output signal from the multiplier 13 is as shown in FIG. 9D due to the problem of the accuracy of the delay unit 12 or the problem of the discontinuity of the ASΚmodulated signal. Then, a waveform including a narrow pulse signal is obtained. The narrow pulse signal is passed through the low-pass filter 14.
The filtering is performed by passing only the baseband signal component, thereby removing the baseband signal component, whereby a baseband signal as shown in FIG. 9E can be obtained.

In the above-described ASK receiving apparatus, the phase difference between the output signal from the comparator 11 and the output signal from the delay unit 12 only needs to be 180 degrees. It may be set to an odd multiple of the half wavelength (T / 2) of the sine wave of f0.

As described above, the {S} receiving apparatus according to the second embodiment converts the analog input signal into a digital signal and processes it in the comparator to which the received ASK modulation signal is input first, so that the transistor The delay time can be easily changed if the delay device is constituted by the gate delay or the like. Therefore, similarly to the case of the first embodiment, a circuit configuration corresponding to a comparator, a delay unit, and a multiplier is replaced with a PLD (Prog
ASK of different frequency f0 without changing hardware if it is composed of digital circuits such as a rammable logic device) and rewrites the delay time etc.
Modulation signals can also be received.

[0036]

As described above, according to the present invention,
It is possible to provide a receiving device which has a small number of parts and can cope with different transmitting / receiving systems. Further, it is possible to realize either the FS @ receiving apparatus or the AS @ receiving apparatus without changing the hardware.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a receiving device according to Embodiment 1 or an embodiment.

FIG. 2 is a block diagram showing a conventional receiving apparatus for receiving an FSΚ modulated signal.

FIG. 3 is a waveform chart showing an example of an FSK modulation signal.

FIG. 4 is a signal waveform diagram of each unit for explaining the operation of the conventional receiving device.

FIG. 5 is a waveform chart showing an example of an ASK modulation signal.

FIG. 6 is a signal waveform diagram of each unit for describing the operation of the receiving device according to the first embodiment.

FIG. 7 is a diagram showing input / output waveforms of a low-pass filter of the receiving device according to the first embodiment.

FIG. 8 is a diagram showing input / output waveforms of a comparator of the receiving apparatus according to the second embodiment.

FIG. 9 is a signal waveform diagram of each unit for describing the operation of the receiving apparatus according to the second embodiment.

[Explanation of symbols]

11 comparators, 12 delay units, 13 multipliers, 1
4 Low-pass filter.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsuhiko Sugitani 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. F term (reference) 5K004 AA03 AA04 DA01 DF00 EA01 EG09

Claims (6)

[Claims] 1. An FS modulated by switching a frequency of a carrier according to a 1/0 value of a baseband signal.
In a receiving apparatus for receiving a K-modulated signal, the received FSK-modulated signal is compared with a predetermined reference level,
A comparator that converts and outputs a 1/0 digital signal, a delay device that delays the output of the comparator by a fixed time and outputs the same, multiplies the output of the comparator and the output of the delay device and exclusions And a multiplier for outputting a logical OR signal, and demodulating a baseband signal from an exclusive OR signal of the multiplier. 2. A delay time of the delay unit is set to a half cycle of a low frequency sine wave of two sine waves received as the carrier wave or an odd multiple thereof. Item 2. The receiving device according to Item 1. 3. The FSK modulation signal according to claim 1, wherein one of the FSK modulated signals has two sinusoidal waves set to an even multiple wavelength of the other as a carrier. Receiver. 4. A receiving apparatus for receiving an ASK modulated signal modulated by turning on / off a carrier according to 1/0 of a baseband signal, comparing the received ASK modulated signal with a predetermined reference level,
A comparator that converts the signal into a 1/0 digital signal and outputs the signal; a delay device that delays the output signal of the comparator by a predetermined time and outputs the signal; and multiplies the output of the comparator and the output of the delay device. A receiving device, comprising: a multiplier that outputs an exclusive OR signal; and demodulating a baseband signal from the exclusive OR signal of the multiplier. 5. The receiving apparatus according to claim 4, wherein a delay time of the delay unit is set to a half cycle of a sine wave received as the carrier wave or an odd multiple thereof. 6. The receiver according to claim 1, further comprising a low-pass filter that removes a high-frequency component included in an exclusive OR signal of the multiplier.