JP2005129974A - Unidirectional wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an one-way wireless communication system for realizing downsizing and low cost, while ensuring communication distance, in a specified low power wireless system. <P>SOLUTION: The unidirectional wireless communication system employs a specified low power wireless transmitter for a transmitter, since the transmitter transmits mainly digital data and the digital data have characteristic immune strong with respect to the S/N, the system employs a super-regeneration detecting receiver for a receiver by taking into account that no hindrance is caused, even if the quality of the receiver side is lowered. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to a wireless system that achieves a reduction in size and cost while ensuring a communication distance equivalent to that of a specific low-power wireless system in a wireless data communication system.

Conventionally, in the radio law in Japan, there are weak wireless and specific low-power wireless as wireless communication that can be operated without qualification. In particular, the specified low-power radio can ensure communication quality even at a communication distance of 100 m indoors or more than 300 m outdoors. However, an expensive circuit configuration is required at the cost, and the bandwidth for each purpose of use of the radio system is low. The communication system is specified and does not cause communication failures such as interference. The weak wireless system can be used only for simple communication means that may cause a communication failure at a distance of 10 m or less even in the best environment, but is a very low-cost communication means. For this reason, wireless communication has been started for analog communication and has been carried out for a long time. Generally, in order to ensure the quality of communication, specific low-power wireless is applied, and the receiver side accordingly Superheterodyne receivers with good reception quality have been used. Such an example can be seen in US Pat.
Japanese Patent Laid-Open No. 6-120853

FIG. 4 is an example of a conventional unidirectional wireless communication system using a specific low power wireless transmission unit and a superheterodyne reception unit. 4-a is a specific low-power wireless transmission unit, and 4-b is a superheterodyne reception unit. Hereinafter, these operations will be described. 4a-1 is a frequency setting unit, and 4a-2 is a power amplification unit. First, the frequency setting unit will be described. As control signals, power ON 401, modulation signal 402, transmission frequency data 403, and AM modulation signal 404 are input to the frequency setting unit. These input signals are output from a control computer described later. The frequency setting unit creates a carrier wave of AM modulation or FM modulation, and determines its frequency. The reference oscillator 405 creates a reference oscillation signal by using a crystal oscillator or a crystal oscillator and a synthesizer. The oscillation signal is given to the frequency divider and frequency-divided corresponding to the transmission frequency data 403 sent from the control computer, and a carrier wave having a desired frequency is output from the frequency divider 406. The phase detector 407, the LPF (low pass filter) 408, the modulator 409, and the VCO (voltage controlled oscillator) 410 return the output of the VCO 410 to the phase detector 407, and the input and phase from the frequency divider 406. By comparing, negative feedback is applied so as to stabilize the frequency. That is, the signal from the VCO 410 is in a state of being synchronized with the carrier wave. Since the modulator 409 contains the modulation signal 402 (analog voltage value) for FM modulation, the oscillation frequency of the VCO changes corresponding to the output voltage, and the FM modulated wave modulated by the modulation signal 402 is Generated from VCO 410. When there is no modulation signal 402, no modulation is performed, so that a signal synchronized with the carrier wave output from the frequency divider 406 is generated. In this case, the carrier wave is used for AM modulation. The FM modulated wave or the AM modulation carrier wave is input to the buffer amplifier 411 of the power amplification unit 4a-2. The buffer amplifier 411 also has an effect of suppressing noise propagation from the antenna side. In the case of AM modulation, AM modulation is performed at the buffer amplifier or the power amplifier by the AM modulation signal 404 (analog voltage value) sent from the control computer. In FM modulation, there is no AM modulation signal 404, and an FM modulated wave is amplified. Finally, unnecessary high frequency spurs are removed and transmitted from the transmission antenna 414. Of course, the transmission output is within 10 mW corresponding to the specific low-power radio standard, and other functions such as an interference prevention function, a transmission time limit function, a carrier sense function, and the like are prepared.

The radio wave transmitted from the transmission antenna 414 propagates in the air and is input to the reception antenna 415 of the 4-b superheterodyne reception unit. Since the power is attenuated during propagation, the power is amplified by the buffer amplifier 416 and enters the SH detector (superheterodyne receiver) 417 to obtain a signal wave. The demodulator 418 determines the voltage level of the signal wave with reference to the threshold determined by the threshold reproduction, and converts the analog signal into a digital signal. The output of the demodulator 418 has data for seeing a match of the individual code that identifies the individual communicator and data to be transmitted. Data to be transmitted is output as demodulated data 422. In the individual identification 420, the coincidence output 423 is output, and only the receivers that coincide with the value set in the individual identification code setting 421 can receive data. The demodulated data 422 and the coincidence output 423 are sent to a data processing device such as a receiving computer.

As described above, in order to ensure reception quality, the configuration of the SH detector 17-a that has been conventionally used is specifically as shown in FIG. 5-a is a functional block display, and 5-b is a circuit diagram display. The received radio wave that has passed through the receiving antenna 415 and the buffer amplifier 416 enters the frequency mixing circuit 501 and is mixed with the oscillation signal of the local oscillation circuit 502 to output an intermediate frequency having a frequency difference between the two waves. In this way, since the input and output frequencies are different, there is no instability even if there is feedback. The intermediate frequency output is put in a filter 503 to remove unnecessary spurious, then amplified by the intermediate frequency amplifier 504, and then detected by the detection circuit 505 to obtain a detection output. The detection output is input to the AGC circuit 506 and controlled by the intermediate frequency amplifier 504 to ensure the amplitude level of the signal. An example of a circuit diagram of 5-a-1 is 5-b-1, where a portion 507 is an input portion for a received signal, a portion 508 corresponds to the local oscillation circuit 502, and a portion 509 is , Corresponding to the filter 503. A frequency mixing circuit for creating a frequency difference is formed by utilizing the nonlinear characteristic between the base and emitter of the transistor. An example of a circuit diagram of 5-a-2 is 5-b-2. The intermediate frequency amplifier 504 is formed by one stage of the transistor 510. The detection circuit 505 is formed by using the non-linear characteristic of the Zener diode 511. The output of the detection circuit controls the base of the transistor 510 through two resistors 512 and 513 to control the gain. The superheterodyne receiver having such a configuration has been used for a long time because it is stable, has little noise, and provides high quality reception characteristics. However, since the circuit configuration is complicated at the price of high quality, there is an inconvenience in downsizing and there is an inconvenience of high cost. Details of the superheterodyne receiver can be found in Non-Patent Document 1.
Kenji Suzuki “Radio & Wireless Circuit Design and Production” CQ Publishing 2003 p138-p146

As described above, the weak wireless system is inexpensive, but has a potential factor that a communication failure occurs when the communication distance becomes long because the transmission power is weak. The conventional specific low-power radio system can perform stable communication even at a distance of several tens of meters or more, but the electronic circuits of the transmitter and the receiver are complicated, and it is difficult to reduce the size and cost. Therefore, it has been desired to realize downsizing and cost reduction while maintaining a communication distance.

The present invention uses a specific low-power wireless transmitter as a transmitter to ensure a communication distance, and the transmitted data is mainly digital. Considering that there is no problem even if it is lowered, a super regenerative detection receiver is used as a receiver.

The invention according to claim 1 is a unidirectional wireless communication system, a specific low power wireless transmitter as a transmitter, a microcomputer for supplying and controlling data to the specific low power wireless transmitter, and the specific small power wireless transmitter. A super regenerative detection receiver is included in the configuration as a receiver that receives radio waves transmitted by the power wireless transmitter.

According to a second aspect of the present invention, in the unidirectional wireless communication system according to the first aspect, the specific low-power radio transmitter and the super regenerative detection receiver are FM modulation of at least one radio wave format among F1D and F2D. An FM detection circuit for demodulating waves is provided.

According to a third aspect of the present invention, in the unidirectional wireless communication system according to the first or second aspect, the microcomputer is pre-assigned to the individual receiver in response to application of a data transmission start signal. And it has the function to send out the individual identification code memorize | stored beforehand as a modulation signal to the said transmitter.

According to a fourth aspect of the present invention, in the unidirectional wireless communication system according to the first, second, or third aspect, the receiver receives the radio wave modulated by the individual identification code, and the individual identification code The demodulated data is generated, and when a match between the demodulated data and the individual identification code dedicated to the receiver set in advance in the receiver is detected, a matching output is output.

In this way, a unidirectional wireless communication system having a small and low-cost receiver with a small amount of constituent materials while ensuring a communication distance obtained by the specific low-power radio can be obtained.

In wireless data communication, it is important to be able to reproduce data with a transmitter that is stable and secures communication of a desired distance, and with a simple configuration, and it is best that the receiver is simple. Therefore, this requirement can be achieved by making the receiver a super regenerative receiver. Hereinafter, the present invention will be described using examples.

FIG. 1 shows an embodiment of a unidirectional wireless communication system according to the present invention. 1-a is a specific low-power wireless transmission unit, which is exactly the same as 4-a in FIG. The description is omitted.
Reference numeral 1-b denotes a super regenerative detection receiving unit. In contrast to 4-b, the SH detector 417 is a super regenerative detector 117. Therefore, in order to clarify the difference, the super regenerative detector 117 will be described.

The super regenerative detector 117 is as shown in FIG. 3-a is a block circuit, and 3-b is an example of an actual circuit. A reception signal from the reception antenna 115 or the buffer amplifier 116 is input to the terminal 301 and amplified by the high frequency amplifier circuit 302. The output passes through the feedback circuit 303 and part of the output is positively fed back to the input of the high-frequency amplifier circuit 302. When positive feedback is applied, the signal increases and eventually oscillates. However, in the state immediately before oscillation, the sensitivity is most improved, and detection should be performed in that state. This is regenerative detection, and the state immediately before oscillation is unstable, so in order to improve this, in super regenerative detection, a signal of several tens of kHz is generated by the blocking oscillator block 304 and the power supply of the regenerative detection block 305 is shaken small. Like that. In this way, the state just before the oscillation and the state of the oscillation are repeated, so that a highly sensitive state can be passed without fail. Thus, the sensitivity can be obtained stably. Since the oscillation state always passes, there is a disadvantage that oscillation noise is generated and the S / N is bad, but there is an advantage that the circuit is simplified as follows. The portion of the regenerative detection block 305 corresponds to the transistor and feedback capacitance of the regenerative detection circuit 306, and the blocking oscillator block 304 corresponds to a component in the LCR of the blocking oscillator circuit 307. The detection unit uses a non-linear portion of the transistor. In this way, the super regenerative detection circuit can basically be based on one transistor, and thus can be reduced in size and cost. Compared to FIG. 5, it can be seen that FIG. 3 has a fairly simple configuration. The super regenerative detection circuit is basically AM detection using the square characteristics of the base-emitter voltage of the transistor and the base current. However, an FM modulation wave is applied to the slope portion of the resonance characteristics by attaching a resonance circuit to the input. Since the frequency change is converted into the amplitude change by adding, AM detection is performed thereafter, and FM modulation wave can also be detected after all. Therefore, super regenerative detection can deal with FM modulated waves with a simple circuit configuration, and can also deal with radio wave formats F1D and F2D. These are the cases where a single channel is used with frequency (angle) modulation and there is no subcarrier.

FIG. 2 shows a computer unit that creates and sends a signal for controlling the unidirectional wireless communication system. The microcomputer 200 stores, as an input, a solid identification code register 201 that stores a number corresponding to each receiver as an input. And a frequency code register 202 for specifying a transmission frequency (channel) and a data transmission start signal 203 for controlling data transmission. On the other hand, the output is modulated signal 204 (analog) for FM modulation, AM modulated signal 205 for AM modulation, transmission frequency (channel) data 206, and power ON / OFF 207, and connected to the transmitter. Will be. This part is the same in the conventional example.

Since the unidirectional wireless communication system according to the present invention can be reduced in size and cost in a receiver, when used for one transmitter having a large number of receivers and mobile receivers. , You can enjoy the benefits. For example, it can be used for control of lines in a factory, monitoring, and simultaneous signal transmission in a traffic system by installing a receiver in each vehicle.

It is a block diagram which shows one embodiment of a structure of the unidirectional radio | wireless communications system which concerns on this invention. It is a figure of the computer control part which controls the unidirectional radio | wireless communications system based on this invention or the conventional. It is a figure which shows one embodiment of the super regenerative detector of FIG. It is a block diagram which shows the structure of the conventional unidirectional radio | wireless communications system. It is a figure which shows an example of the SH detector of FIG.

Explanation of symbols

101, 401 ... Power ON (input), 102, 402 ... Modulation signal (input)
103, 403 ... Transmission frequency data (input)
104, 404 ... AM modulation signal (input)
105,405 ... reference oscillator 106,406 ... frequency divider 107,407 ... phase detector 108,113,408,413 ... LPF
109, 409 ... modulator, 110, 410 ... VCO
111, 116, 411, 416 ... buffer amplifier 112, 412 ... power amplifier, 114, 414 ... transmitting antenna 115, 415 ... receiving antenna, 117 ... super regenerative detector 118, 418 ..Demodulators, 119, 419 ... Threshold regeneration 120, 420 ... Solid identification, 121,421 ... Solid identification code setting 122,422 ... Demodulated data output, 123,423 ... Match output DESCRIPTION OF SYMBOLS 200 ... Microcomputer, 201 ... Solid identification code register 202 ... Frequency code register, 203 ... Data transmission start signal 204 ... Modulation signal (output), 205 ... AM modulation signal (output) )
206 ... Transmission frequency data (output), 207 ... Power ON / OFF (output)
DESCRIPTION OF SYMBOLS 301 ... Terminal, 302 ... High frequency amplifier circuit, 303 ... Feedback circuit 304 ... Blocking oscillator block, 305 ... Reproduction detection block 306 ... Reproduction detection circuit, 307 ... Blocking oscillator circuit 417 ... SH detector 501 ... frequency mixing circuit, 502 ... local oscillation circuit, 503 ... filter 504 ... intermediate frequency amplifier, 505 ... detection circuit, 506 ... AGC circuit 507・ ・ ・ Receiving signal input unit, 508 ... Local oscillation circuit corresponding unit 509 ... Filter corresponding unit, 510 ... Transistor 511 ... Zener diode, 512,513 ... Resistance

Claims (4)

  Super regenerative detection as a specific low power radio transmitter as a transmitter, a microcomputer for supplying and controlling data to the specific low power radio transmitter, and a receiver for receiving radio waves transmitted from the specific low power radio transmitter A unidirectional wireless communication system comprising: a receiver.   2. The specific low-power radio transmitter and the super regenerative detection receiver each include an FM detection circuit that demodulates an FM modulated wave of at least one radio wave format among F1D and F2D. Unidirectional wireless communication system.   The microcomputer has a function of transmitting an individual identification code pre-assigned to the individual receiver and stored in advance as a modulation signal to the transmitter in response to application of a data transmission start signal. The unidirectional wireless communication system according to claim 1 or 2, characterized in that The receiver receives a radio wave modulated with the individual identification code, generates demodulated data of the individual identification code, and the demodulated data and an individual identification code dedicated to the receiver set in the receiver in advance. The unidirectional wireless communication system according to claim 1, wherein the unidirectional wireless communication system has a function of outputting a coincidence output when a coincidence is detected.

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