Transmitter, receiver, and transmission / reception system

Abstract

The purpose of the present invention is to suppress the generation of a noise component in a voice signal.　This transmitter transmits a composite modulated signal in which a composite signal of a carrier modulation signal and a voice signal is analog-modulated. The carrier modulation signal is generated on the basis of a serial data signal in which prescribed information is stored and a carrier signal. The voice signal is generated on the basis of a sound wave from a sound source. The transmitter includes a storage unit that stores the prescribed information and a control unit that generates the serial data signal. The serial data signal includes a preamble in which specific bits and non-specific bits are alternately arranged, and when the bit width of the non-specific bit is a reference bit width, the bit width of the specific bit is M.N times (M, N: an integer of any one of 1 to 9) the reference bit width.

Description

Transmitter, receiver and transmission / reception system

[0001] The present invention relates to a transmitter, a receiver and a transmitting / receiving system.

[0002] Among conventional transmission / reception systems, there is known a transmission / reception system (hereinafter referred to as a "conventional transmission / reception system") that transmits and receives a data signal together with an audio signal (see, for example, Patent Document 1). A transmitter of the conventional transmission / reception system (hereinafter referred to as a "conventional transmitter") first generates a data signal and an audio signal.

[0003] Here, the data signal is generated based on predetermined information and a serial data signal (so-called data frame). The data frame includes a preamble and a payload. Within the data frame, the preamble includes a repeating pattern of a specific bit string, such as "101010...". The bit width of each bit constituting the specific bit string is equal. A receiver of a conventional transmission / reception system (hereinafter referred to as a "conventional receiver") identifies the start position of the payload within the data frame based on the repeating pattern of the specific bit string. In other words, the repeating pattern of the specific bit string functions as an identification flag for the payload.

[0004] The conventional transmitter then generates a composite signal based on the data signal and the voice signal, which is then analog-modulated and transmitted to the conventional receiver.

[0005] The conventional receiver demodulates the received composite signal to extract the data signal and the voice signal, and then extracts predetermined information stored in the payload from the received data signal based on the repeating pattern of a specific bit sequence.

[0006] In recent years, there has been a demand for larger data signals to be transmitted and received together with audio signals. When a conventional transmission / reception system transmits or receives a large-capacity data signal, it requires a device conforming to a communication standard such as Bluetooth (registered trademark) Low Energy (BLE). Therefore, additional costs are required to install the device. On the other hand, when a conventional transmission / reception system transmits or receives a large-capacity data signal without using the device, the data signal may contain noise components based on the high-frequency components of the data signal. The noise components contained in the data signal affect the audio signal. As a result, the noise components may appear in the audio signal.

[0007] Japanese Patent Application Laid-Open No. 2004-128566

[0008] An object of the present invention is to suppress the occurrence of noise components in an audio signal.

[0009] A transmitter according to the present invention is a transmitter that transmits a composite modulated signal obtained by analog-modulating a composite signal of a carrier modulated signal and an audio signal, wherein the carrier modulated signal is generated based on a serial data signal that stores predetermined information and a carrier signal, and the audio signal is generated based on sound waves from a sound source, and the transmitter comprises: a memory unit that stores the predetermined information; and a control unit that generates the serial data signal, wherein the serial data signal includes a preamble in which specific bits and non-specific bits are arranged alternately, and when the bit width of the non-specific bits is a reference bit width, the bit width of the specific bits is M.N times the reference bit width (M, N: any integer from 1 to 9).

[0010] The present invention can suppress the occurrence of noise components in an audio signal.

[0011] FIG. 1 is a schematic diagram showing an embodiment of a transmission / reception system according to the present invention. FIG. 1 is a schematic diagram showing the relationship between a serial data signal, a carrier signal, and an audio signal generated by a transmitter according to the present invention. FIG. 2 is a schematic diagram showing the structure of the serial data signal (data frame). FIG. 3 is a functional block diagram showing an embodiment of the transmitter. FIG. 4 is a functional block diagram showing an embodiment of a receiver according to the present invention. FIG. 5 is a flowchart showing an example of the operation of the transmitter. FIG. 6 is a schematic diagram showing changes in the waveforms of the serial data signal and carrier signal generated by the transmitter. FIG. 7 is a flowchart showing an example of the operation of the receiver. FIG. 8 is a schematic diagram showing changes in the waveform of a carrier modulated signal extracted by the receiver.

[0012] Embodiments of a transmitter (hereinafter referred to as "the transmitter"), a receiver (hereinafter referred to as "the receiver"), and a transmission / reception system (hereinafter referred to as "the system") according to the present invention will be described below with reference to the drawings.

[0013] Configuration of the System FIG. 1 is a schematic diagram showing an embodiment of the system.

[0014] This system 1 transmits and receives a composite modulated signal S6 obtained by FM modulating (analog modulating) a composite signal S5 of a carrier modulated signal S3 and an audio signal S4. This system 1 includes this transmitter 2 and this receiver 3. Details of the carrier modulated signal S3, the audio signal S4, the composite signal S5, and the composite modulated signal S6 will be described later.

[0015] The transmitter 2 generates a serial data signal S1, a carrier signal S2, a carrier modulated signal S3, an audio signal S4, a composite signal S5, and a composite modulated signal S6. The transmitter 2 transmits the generated composite modulated signal S6 to the receiver 3. The transmitter 2 includes a storage unit 21, a control unit 22, a filter unit 23, a carrier signal generation unit 24, a carrier signal modulation unit 25, an audio signal generation unit 26, a synthesis unit 27, a composite signal modulation unit 28, and a transmission unit 29. The serial data signal S1 and the carrier signal S2 will be described in detail later.

[0016] The receiver 3 receives the composite modulated signal S6 from the transmitter 2. The receiver 3 includes a receiving unit 31, a signal extracting unit 32, an A / D converting unit 33, a data signal output unit 34, an audio signal processing unit 35, and an audio signal output unit 36.

[0017] Relationships Between Signals FIG. 2 is a schematic diagram showing the relationships between the serial data signal, carrier signal, and audio signal generated by this transmitter.

[0018] The serial data signal S1 is a data frame that stores predetermined information. The serial data signal S1 is, for example, a digital signal in a frequency band of 30 kHz to 40 kHz. The serial data signal S1 (data frame) includes a preamble, a payload, and a checksum.

[0019] The predetermined information is, for example, information indicating the results of detection by a sensor (not shown) provided in the transmitter 2, or information input by a switch (not shown) provided in the transmitter 2, or the like.

[0020] The carrier signal S2 is a carrier wave for carrying the serial data signal S1. The carrier signal S2 is modulated by the linearly processed serial data signal S1. The carrier signal S2 is an analog signal.

[0021] Carrier modulation signal S3 is generated based on serial data signal S1 and carrier signal S2. Specifically, carrier modulation signal S3 is generated by modulating carrier signal S2 with serial data signal S1, which has been linearly processed. Predetermined information is stored in serial data signal S1. Therefore, carrier modulation signal S3 includes the predetermined information. Carrier modulation signal S3 is an analog signal.

[0022] The audio signal S4 is a signal generated based on sound waves from a sound source, and is, for example, an analog signal in the frequency band of 20 Hz to 20 kHz.

[0023] The composite signal S5 is a signal generated by combining the carrier modulation signal S3 and the audio signal S4, and is an analog signal.

[0024] The composite modulated signal S6 is a signal generated by FM modulating (analog modulating) the composite signal S5. The composite modulated signal S6 is an analog signal.

[0025] Generation of Noise Components The serial data signal S1 generated by the transmitter 2 has a large capacity. That is, the serial data signal S1 includes high-frequency components. Therefore, the serial data signal S1 may include noise components based on the high-frequency components of the serial data signal S1.

[0026] The system 1 transmits and receives a composite modulated signal S6 generated based on a serial data signal S1 and an audio signal S4. When a noise component is included in the serial data signal S1, the system 1 may fail to transmit and receive the composite modulated signal S6. Furthermore, the noise component included in the serial data signal S1 may affect the audio signal S4. As a result, the noise component may appear in the audio signal S4.

[0027] ●Data Frame Structure● Figure 3 is a schematic diagram showing the structure of a serial data signal (data frame). This figure shows that the data frame includes a preamble, a payload, and a checksum. In the figure, the scale from "0" to "X (X is an integer greater than or equal to 13)" indicates the size of the bit width. One scale (for example, the length from "0" to "1") is the size of one non-specific bit width. Details of the non-specific bit width will be described later. In the figure, the double-headed arrow at the top of the page indicates the range of the data frame. In the figure, the three double-headed arrows at the bottom of the page indicate the range of the preamble, the range of the payload, and the range of the checksum. In the figure, the figure surrounded by a dashed rectangle shown between the scale and the double-headed arrows indicating the range of the preamble indicates the specific pattern P. Within the specific pattern P, the thin line indicates the non-specific bit B2. The thick line indicates the specific bit B1. In the figure, the figure shown between the scale and the double-headed arrow indicating the range of the payload indicates the bit string of the payload. In the figure, the double wavy line indicates that part of the bit string of the payload is omitted. In the figure, the figure shown between the scale and the double-headed arrow indicating the range of the checksum indicates the bit string of the checksum.

[0028] In the following description, "head" refers to the first position of a data frame read into the receiver 3. "tail" refers to the last position of a data frame read into the receiver 3.

[0029] Preamble The preamble is a predetermined bit string that is read into the receiver 3 so that the receiver 3 can identify the start position of the payload within the data frame. Each bit constituting the predetermined bit string contains information indicating either "0 (Low)" or "1 (High)." The preamble is placed at the beginning of the data frame. The predetermined bit string (specific pattern P) of the preamble is composed of a specific bit B1 and a non-specific bit B2. In the specific pattern P, the specific bit B1 and the non-specific bit B2 are alternately arranged. In other words, the preamble is a bit string composed of the specific bit B1 and the non-specific bit B2 alternately arranged.

[0030] Here, the receiver 3 identifies the start position of the payload within the data frame from two or more specific bits B1. In the specific pattern P, the specific bits B1 and non-specific bits B2 are alternately arranged. Therefore, the number of specific bits B1 and non-specific bits B2 that make up the specific pattern P is two or more. That is, for example, the specific pattern P is composed of two specific bits B1 and three non-specific bits B2.

[0031] The specific bit B1 is a bit having a specific bit width, which is the time it takes for the receiver 3 to read from the start of the rising edge to the start of the falling edge of one specific bit B1.

[0032] The non-specific bit B2 is a bit whose bit width is the non-specific bit width. The non-specific bit width is the time it takes for the receiver 3 to read one non-specific bit B2 from the start of its falling edge to the start of its rising edge. When the non-specific bit width is the reference bit width (reference bit width), the specific bit width is M.N times the reference bit width (M, N: any integer from 1 to 9).

[0033] In this embodiment, M is 1 and N is 5. That is, the specific bit width is 1.5 times the non-specific bit width (reference bit width).

[0034] The receiver 3 reads the preamble. The receiver 3 recognizes a specific pattern P from the read preamble. When the receiver 3 recognizes the specific pattern P, the receiver 3 identifies the start position of the payload within the data frame. In other words, the preamble within the data frame functions as an identification flag for the start position of the payload.

[0035] Payload The payload is a bit string that stores predetermined information. The payload is placed between the preamble and the checksum.

[0036] Checksum The checksum is a value calculated by the transmitter 2 based on the payload included in the transmitted data frame. The checksum is placed at the end of the data frame.

[0037] Here, the receiver 3 calculates a checksum value based on the payload included in the received data frame. The receiver 3 determines whether the calculated value matches the checksum value included in the received data frame. If the calculated value matches the checksum value, the receiver 3 determines that the information stored in the received payload is the same as the predetermined information stored in the payload transmitted by the transmitter 2.

[0038] Configuration of the Present Transmitter FIG. 4 is a functional block diagram showing an embodiment of the present transmitter.

[0039] The storage unit 21 stores predetermined information. The storage unit 21 may be, for example, a portable storage medium such as a hard disk drive (HDD), a solid state drive (SSD), or a flash memory, or another non-transitory storage medium, or a random access memory (RAM) or another temporary storage medium.

[0040] The control unit 22 generates a serial data signal S1 containing the predetermined information based on the predetermined information stored in the storage unit 21. The control unit 22 transmits the generated serial data signal S1 to the filter unit 23.

[0041] The filter unit 23 is a linear processing filter. The filter unit 23 receives the serial data signal S1 from the control unit 22. The filter unit 23 performs linear processing on the rising and falling edges of the serial data signal S1. The filter unit 23 transmits the serial data signal S1 that has undergone linear processing to the carrier signal modulation unit 25.

[0042] Here, the waveforms of the rising and falling edges of the serial data signal S1 that has been linearly processed are rounded, resulting in gentler slopes of the rising and falling edges of the serial data signal S1.

[0043] Rising Edge / Falling Edge A rising edge is a portion of the serial data signal S1 where the voltage level transitions from "Low" to "High". A falling edge is a portion of the serial data signal S1 where the voltage level transitions from "High" to "Low". When the voltage exceeds a predetermined threshold, the voltage level is "High". When the voltage does not exceed the predetermined threshold, the voltage level is "Low". When the voltage level is "High", the control unit 22 outputs a signal with a voltage level of "1". When the voltage level is "Low", the control unit 22 outputs a signal with a voltage level of "0".

[0044] The carrier signal generator 24 generates a carrier signal S2 and transmits the generated carrier signal S2 to the carrier signal modulator 25.

[0045] The carrier signal modulation unit 25 receives the linearly processed serial data signal S1 from the filter unit 23. The carrier signal modulation unit 25 receives the carrier signal S2 from the carrier signal generation unit 24. The carrier signal modulation unit 25 modulates the carrier signal S2 with the linearly processed serial data signal S1 to generate a carrier modulated signal S3. The carrier signal modulation unit 25 transmits the generated carrier modulated signal S3 to the combiner unit 27.

[0046] The audio signal generating unit 26 generates an audio signal S4 based on sound waves from a sound source, and transmits the generated audio signal S4 to the synthesis unit 27.

[0047] A sound source is a person or object that is emitting some kind of sound.

[0048] The synthesis unit 27 receives the carrier modulated signal S3 from the carrier signal modulation unit 25. The synthesis unit 27 receives the audio signal S4 from the audio signal generation unit 26. The synthesis unit 27 synthesizes the carrier modulated signal S3 and the audio signal S4 to generate a synthesized signal S5. The synthesis unit 27 transmits the generated synthesized signal S5 to the synthesized signal modulation unit 28.

[0049] The combined signal modulation unit 28 receives the combined signal S5 from the combiner 27. The combined signal modulation unit 28 performs FM modulation (analog modulation) on the combined signal S5 to generate a combined modulated signal S6. The combined signal modulation unit 28 transmits the generated combined modulated signal S6 to the transmitter 29.

[0050] The analog modulation in the present invention is not limited to FM (Frequency Modulation), and may be, for example, AM (Amplitude Modulation) or PM (Phase Modulation).

[0051] The transmitter 29 receives the composite modulated signal S6 from the composite signal modulator 28. The transmitter 29 transmits the received composite modulated signal S6 to the receiver 3.

[0052] Configuration of the Receiver FIG. 5 is a functional block diagram showing an embodiment of the receiver.

[0053] The receiver 31 receives the composite modulated signal S6 from the transmitter 2. The receiver 31 transmits the received composite modulated signal S6 to the signal extractor 32.

[0054] Signal extraction unit 32 receives composite modulated signal S6 from receiving unit 31. Signal extraction unit 32 extracts carrier modulated signal S3 and composite signal S5 from composite modulated signal S6. Signal extraction unit 32 transmits the extracted carrier modulated signal S3 to A / D conversion unit 33. Signal extraction unit 32 transmits the extracted composite signal S5 to audio signal processing unit 35. Signal extraction unit 32 includes a demodulation unit 321, a first extraction filter unit 322, and a second extraction filter unit 323.

[0055] The demodulator 321 receives the composite modulated signal S6 from the receiver 31. The demodulator 321 demodulates the composite modulated signal S6 into a composite signal S5. The demodulator 321 transmits the demodulated composite signal S5 to the first extraction filter 322. The demodulator 321 transmits the demodulated composite signal S5 to the audio signal processor 35.

[0056] The first extraction filter unit 322 is a band-pass filter and receives the demodulated combined signal S5 from the demodulation unit 321.

[0057] Here, the frequency band of demodulated combined signal S5 includes the frequency band of carrier modulation signal S3 and the frequency band of audio signal S4. First extraction filter unit 322 passes (extracts) the frequency band of carrier modulation signal S3 from the frequency band of demodulated combined signal S5. That is, first extraction filter unit 322 extracts the frequency band of carrier modulation signal S3 from the frequency band of demodulated combined signal S5. That is, first extraction filter unit 322 extracts carrier modulation signal S3 from demodulated combined signal S5. First extraction filter unit 322 transmits the extracted carrier modulation signal S3 to second extraction filter unit 323.

[0058] The second extraction filter unit 323 is a low-pass filter and receives the extracted carrier-modulated signal S3 from the first extraction filter unit 322.

[0059] Here, the frequency band of extracted carrier modulated signal S3 includes the frequency band of noise components. In other words, extracted carrier modulated signal S3 includes noise components. Second extraction filter unit 323 does not pass (attenuates) the frequency band of noise components from the frequency band of extracted carrier modulated signal S3. In other words, second extraction filter unit 323 removes the frequency band of noise components from the frequency band of extracted carrier modulated signal S3. Second extraction filter unit 323 transmits carrier modulated signal S3 from which the noise components have been removed to A / D conversion unit 33.

[0060] The settings of the first extraction filter unit 322, which is a band-pass filter, and the second extraction filter unit 323, which is a low-pass filter, can be adjusted as appropriate. Therefore, the first extraction filter unit 322 and the second extraction filter unit 323 are each set so as to remove noise components.

[0061] The A / D conversion unit 33 is an analog-to-digital converter that converts an analog signal into a digital signal. The A / D conversion unit 33 receives the carrier modulation signal S3 extracted by the signal extraction unit 32, i.e., the carrier modulation signal S3 from which the noise component has been removed by the second extraction filter unit 323. The A / D conversion unit 33 converts the carrier modulation signal S3 extracted by the signal extraction unit 32, i.e., the carrier modulation signal S3 from which the noise component has been removed by the second extraction filter unit 323, into a digital signal. The carrier modulation signal S3 converted into a digital signal (hereinafter referred to as the "converted signal") is a linearly processed serial data signal S1. In other words, the linearly processed serial data signal S1 is restored by the A / D conversion unit 33. The converted signal includes the preamble, payload, and checksum contained in the serial data signal S1. The A / D conversion unit 33 transmits the converted signal to the data signal output unit 34.

[0062] The data signal output unit 34 receives the converted signal from the A / D conversion unit 33. The data signal output unit 34 reads the converted signal. The data signal output unit 34 recognizes a specific pattern P from the preamble included in the read converted signal. The data signal output unit 34 identifies the start position of the payload based on the specific bit width included in the recognized specific pattern P. The data signal output unit 34 extracts predetermined information stored in the payload whose start position has been identified. In other words, the data signal output unit 34 extracts the predetermined information from the converted signal based on the specific bit width. The data signal output unit 34 transmits the extracted predetermined information to the data output device 5.

[0063] The data output device 5 is, for example, a monitor that displays predetermined information.

[0064] The data signal output unit 34 is an example of an information extraction unit in the present invention.

[0065] The audio signal processing unit 35 receives the demodulated composite signal S5 from the demodulation unit 321.

[0066] Here, the audio signal processing unit 35 includes an audio signal extraction filter unit (not shown). The audio signal extraction filter unit is a band-pass filter. The frequency band of the demodulated synthetic signal S5 includes the frequency band of the carrier modulation signal S3 and the frequency band of the audio signal S4. The audio signal extraction filter unit passes (extracts) the frequency band of the audio signal S4 from the frequency band of the demodulated synthetic signal S5. That is, the audio signal extraction filter unit extracts the frequency band of the audio signal S4 from the frequency band of the demodulated synthetic signal S5. That is, the audio signal extraction filter unit extracts the audio signal S4 from the demodulated synthetic signal S5. In other words, the audio signal processing unit 35 extracts the audio signal S4 from the demodulated synthetic signal S5. That is, the audio signal processing unit 35 restores the audio signal S4. The audio signal processing unit 35 transmits the extracted audio signal S4 to the audio signal output unit 36.

[0067] The audio signal output unit 36 ​​receives the extracted audio signal S4 from the audio signal processing unit 35. The audio signal output unit 36 ​​transmits the received audio signal S4 to the audio output device 4.

[0068] The audio output device 4 is, for example, a speaker that outputs an audio signal S4.

[0069] Operation of the System The operation of the system 1 will be explained below.

[0070] Operation of the Transmitter In the following description, predetermined information is stored in advance in the storage unit 21.

[0071] FIG. 6 is a flowchart showing an example of the operation of the transmitter.

[0072] 7 is a schematic diagram showing waveform changes of the serial data signal and carrier signal generated by this transmitter. This diagram shows that serial data signal S1 is transmitted to filter unit 23. This diagram shows that linearly processed serial data signal S1 and carrier signal S2 are transmitted to carrier signal modulation unit 25. This diagram also shows that carrier modulation signal S3 is transmitted from carrier signal modulation unit 25. In the diagram, the waveform of serial data signal S1 on the right side of the page represents the waveform of serial data signal S1. In the diagram, the waveform of linearly processed serial data signal S1 on the right side of the page represents the waveform of linearly processed serial data signal S1. In the diagram, the waveform of carrier signal S2 at the top of the page represents the waveform of carrier signal S2. In the diagram, the waveform of carrier modulation signal S3 on the right side of the page represents the waveform of carrier modulation signal S3.

[0073] In the following description of FIG. 6, FIG. 7 will be referred to as appropriate.

[0074] The composite signal generation process (ST1) is a process in which the transmitter 2 generates a composite signal S5 based on the serial data signal S1, carrier signal S2, and audio signal S4. The transmitter 2 transmits a composite modulated signal S6, which is analog-modulated from the composite signal S5, to the receiver 3.

[0075] First, the control unit 22 generates a serial data signal S1 (ST11). Specifically, the control unit 22 reads predetermined information stored in the storage unit 21 from the storage unit 21. After reading the predetermined information, the control unit 22 generates a digital serial data signal S1 (data frame) based on the predetermined information. That is, the control unit 22 generates a preamble, a payload, and a checksum that constitute the data frame. At this time, the predetermined information is stored in the payload of the data frame.

[0076] Next, the control unit 22 transmits the generated serial data signal S1 to the filter unit 23 (ST12).

[0077] Next, the filter unit 23 performs linear processing on the serial data signal S1 (ST13). Specifically, the filter unit 23 receives the serial data signal S1 from the control unit 22. The filter unit 23 performs linear processing on the rising and falling edges of the received serial data signal S1. At this time, the waveforms of the rising and falling edges of the serial data signal S1 that have undergone linear processing are rounded. As a result, the slope angles of the rising and falling edges of the serial data signal S1 become gentler (see FIG. 7). The filter unit 23 transmits the serial data signal S1 that has undergone linear processing to the carrier signal modulation unit 25.

[0078] Here, the steeper the slope angle between the rising and falling edges of the serial data signal S1, the more likely it is that noise components based on the high frequency components of the serial data signal S1 will be included in the serial data signal S1. In other words, the linearly processed serial data signal S1 is less likely to include noise components than the non-linearly processed serial data signal S1.

[0079] Meanwhile, the carrier signal generator 24 generates a carrier signal S2 (ST14). Specifically, the carrier signal generator 24 generates the carrier signal S2 (carrier wave), which is an analog signal. The carrier signal generator 24 transmits the generated carrier signal S2 to the carrier signal modulator 25.

[0080] Next, the carrier signal modulation unit 25 modulates the carrier signal S2 (ST15). Specifically, the carrier signal modulation unit 25 receives the serial data signal S1 that has been linearly processed from the filter unit 23. The carrier signal modulation unit 25 receives the carrier signal S2 from the carrier signal generation unit 24. The carrier signal modulation unit 25 modulates the received carrier signal S2 with the received serial data signal S1 to generate a carrier modulated signal S3, which is an analog signal (see FIG. 7). The carrier signal modulation unit 25 transmits the generated carrier modulated signal S3 to the combiner 27.

[0081] Meanwhile, the audio signal generation unit 26 generates an audio signal S4 (ST16). Specifically, the audio signal generation unit 26 generates the audio signal S4, which is an analog signal, based on sound waves from a sound source. The audio signal generation unit 26 transmits the generated audio signal S4 to the synthesis unit 27.

[0082] Next, the synthesis unit 27 generates a synthesized signal S5 (ST17). Specifically, the synthesis unit 27 receives the carrier modulated signal S3 from the carrier signal modulation unit 25. The synthesis unit 27 receives the audio signal S4 from the audio signal generation unit 26. The synthesis unit 27 synthesizes the received carrier modulated signal S3 and the received audio signal S4 to generate a synthesized signal S5, which is an analog signal. The synthesis unit 27 transmits the generated synthesized signal S5 to the synthesized signal modulation unit 28.

[0083] Next, the composite signal modulation unit 28 modulates the composite signal S5 (ST18). Specifically, the composite signal modulation unit 28 receives the composite signal S5 from the combiner 27. The composite signal modulation unit 28 performs FM modulation (analog modulation) on the received composite signal S5 to generate a composite modulated signal S6, which is an analog signal. The composite signal modulation unit 28 transmits the generated composite modulated signal S6 to the transmitter 29.

[0084] Next, the transmitter 29 transmits the composite modulated signal S6 to the receiver 3 (ST19). Specifically, the transmitter 2 receives the composite modulated signal S6 from the composite signal modulator 28. The transmitter 29 transmits the received composite modulated signal S6 to the receiver 3.

[0085] Operation of the Receiver FIG. 8 is a flowchart showing an example of the operation of the receiver.

[0086] 9 is a schematic diagram showing changes in the waveform of a carrier-modulated signal extracted by this receiver. This diagram shows that demodulated combined signal S5 is transmitted to first extraction filter unit 322. This diagram also shows that extracted carrier-modulated signal S3 is transmitted to second extraction filter unit 323. This diagram also shows that carrier-modulated signal S3 from which noise components have been removed is transmitted from second extraction filter unit 323. In the diagram, the waveform of extracted carrier-modulated signal S3 at the top of the page represents the waveform of extracted carrier-modulated signal S3. In the diagram, the waveform of carrier-modulated signal S3 from which noise components have been removed at the left of the page represents the waveform of carrier-modulated signal S3 from which noise components have been removed. In the diagram, dashed circles represent waveforms that include noise components.

[0087] In the following description of FIG. 8, reference will be made to FIG. 9 as appropriate.

[0088] The restoration process (ST2) is a process in which the receiver 3 restores the linearly processed serial data signal S1 and the audio signal S4 from the received composite modulated signal S6. The receiver 3 extracts predetermined information from the restored linearly processed serial data signal S1 (hereinafter referred to as the "restored data signal"). The receiver 3 transmits the extracted predetermined information to the data output device 5. The receiver 3 transmits the restored audio signal S4 to the audio output device 4.

[0089] First, the receiver 31 receives the composite modulated signal S6 (ST21). Specifically, the receiver 31 receives the composite modulated signal S6 from the transmitter 2. The receiver 31 transmits the received composite modulated signal S6 to a demodulator 321 included in the signal extractor 32.

[0090] Next, the demodulator 321 demodulates the composite modulated signal S6 (ST22). Specifically, the demodulator 321 receives the composite modulated signal S6 from the receiver 31. The demodulator 321 demodulates the received composite modulated signal S6 into a composite signal S5. The demodulator 321 transmits the demodulated composite signal S5 to the first extraction filter 322 included in the signal extractor 32. The demodulator 321 transmits the demodulated composite signal S5 to the audio signal processor 35.

[0091] Next, first extraction filter unit 322 extracts carrier-modulated signal S3 from demodulated combined signal S5 (ST23). Specifically, first extraction filter unit 322 receives demodulated combined signal S5 from demodulator 321. First extraction filter unit 322 passes the frequency band of carrier-modulated signal S3 from the frequency band of received combined signal S5. That is, first extraction filter unit 322 extracts carrier-modulated signal S3 from received combined signal S5. First extraction filter unit 322 transmits the extracted carrier-modulated signal S3 (see FIG. 9 ) to second extraction filter unit 323 included in signal extraction unit 32.

[0092] As described above, the extracted carrier modulated signal S3 contains a noise component (see FIG. 9).

[0093] Next, second extraction filter unit 323 removes noise components from extracted carrier modulated signal S3 (ST24). Specifically, second extraction filter unit 323 receives extracted carrier modulated signal S3 from first extraction filter unit 322. Second extraction filter unit 323 does not pass the frequency band of the noise components in extracted carrier modulated signal S3. In other words, second extraction filter unit 323 removes the noise components from extracted carrier modulated signal S3. Second extraction filter unit 323 transmits carrier modulated signal S3 (see FIG. 9 ) from which the noise components have been removed to A / D conversion unit 33.

[0094] Next, the A / D conversion unit 33 restores the linearly processed serial data signal S1 (ST25). Specifically, the A / D conversion unit 33 receives the carrier modulation signal S3 from which the noise component has been removed from the second extraction filter unit 323. The A / D conversion unit 33 converts the carrier modulation signal S3 from which the noise component has been removed by the second extraction filter unit 323 into a digital signal. In other words, the linearly processed serial data signal S1 (converted signal) is restored. The A / D conversion unit 33 transmits the converted signal to the data signal output unit 34.

[0095] As described above, the converted signal includes the preamble, payload, and checksum contained in the serial data signal S1.

[0096] Next, the data signal output unit 34 extracts predetermined information from the converted signal (ST26). Specifically, the data signal output unit 34 receives the converted signal from the A / D conversion unit 33. The data signal output unit 34 reads the received converted signal. As a result, the data signal output unit 34 extracts the predetermined information stored in the payload from the converted signal based on the specific bit width of the specific bit B1 that constitutes the specific pattern P of the preamble.

[0097] Next, the data signal output unit 34 transmits the extracted predetermined information to the data output device 5 (ST27).

[0098] Meanwhile, the audio signal processing unit 35 restores the audio signal S4 (ST28). Specifically, the audio signal processing unit 35 receives the demodulated synthetic signal S5 from the demodulation unit 321. The audio signal extraction filter unit included in the audio signal processing unit 35 passes the frequency band of the audio signal S4 from the frequency band of the demodulated synthetic signal S5. That is, the audio signal extraction filter unit extracts the audio signal S4 from the demodulated synthetic signal S5. That is, the audio signal S4 is restored. The audio signal processing unit 35 transmits the extracted (restored) audio signal S4 to the audio signal output unit 36.

[0099] Next, the audio signal output unit 36 ​​transmits the extracted (restored) audio signal S4 to the audio output device 4 (ST29). Specifically, the audio signal output unit 36 ​​receives the extracted (restored) audio signal S4 from the audio signal processing unit 35. The audio signal output unit 36 ​​transmits the received audio signal S4 to the audio output device 4.

[0100] Summary As explained above, the transmitter 2 transmits a composite modulated signal S6 obtained by analog-modulating a composite signal S5 of a carrier modulated signal S3 and an audio signal S4. The receiver 3 receives the composite modulated signal S6 from the transmitter 2. The carrier modulated signal S3 is generated based on a serial data signal S1 containing predetermined information and a carrier signal S2. The audio signal S4 is generated based on sound waves from a sound source. The transmitter 2 includes a memory unit 21 that stores the predetermined information and a control unit 22 that generates the serial data signal S1. The serial data signal S1 includes a preamble in which specific bits B1 and non-specific bits B2 are alternately arranged. When the non-specific bit width is a reference bit width, the specific bit width is M.N times the reference bit width (M, N: any integer from 1 to 9). In other words, the specific bit width and the non-specific bit width are different from each other. Therefore, the receiver 3 that receives the composite modulated signal S6 from the transmitter 2 can identify the start position of the payload within the data frame based on the specific bit width. In other words, the specific bit width can function as an identification flag for the payload.

[0101] Furthermore, the specific bit width included in the preamble in this transmitter 2 is larger than the non-specific bit width. The larger the bit width, the lower the preamble frequency. The lower the preamble frequency, the less likely it is that noise components based on high-frequency components will be included in the preamble. Therefore, the preamble generated by this transmitter 2 is less likely to include noise components than a preamble in a transmission / reception system consisting only of non-specific bits B2. In other words, noise components are less likely to occur in the serial data signal S1 generated by this transmitter 2. In other words, noise components are less likely to occur in the audio signal S4 demodulated from the composite modulated signal S6 transmitted by this transmitter 2.

[0102] As described above, the transmitter 2 includes a carrier signal generator 24 that generates a carrier signal S2, a filter 23 that performs linear processing on the rising and falling edges of the serial data signal S1, and a carrier signal modulator 25 that modulates the carrier signal S2 with the linearly processed serial data signal S1 to generate a carrier-modulated signal S3. That is, the serial data signal S1 in the transmitter 2 is linearly processed. The waveforms of the rising and falling edges of the linearly processed serial data signal S1 are rounded. As a result, the slope angles of the rising and falling edges become gentler. Generally, the steeper the slope angles of the rising and falling edges, the more likely noise components based on high-frequency components are to be included. Therefore, the serial data signal S1 that has been linearly processed by the transmitter 2 is less likely to include noise components than a serial data signal S1 that has not been linearly processed. That is, noise components are less likely to be included in the audio signal S4 demodulated from the composite modulated signal S6 transmitted by the transmitter 2.

[0103] Furthermore, as described above, the receiver 3 receives a composite modulated signal S6 obtained by analog-modulating a composite signal S5 of a carrier modulated signal S3 and an audio signal S4. The carrier modulated signal S3 is generated based on a serial data signal S1 storing predetermined information and a carrier signal S2. The audio signal S4 is generated based on sound waves from a sound source. The receiver 3 includes a demodulator 321 that demodulates the composite modulated signal S5 from the composite modulated signal S6, a first extraction filter 322 that extracts the carrier modulated signal S3 from the demodulated composite signal S5, and a second extraction filter 323 that removes noise components from the extracted carrier modulated signal S3. The demodulated composite signal S5 in the receiver 3 may include noise components based on high-frequency components. By passing the composite signal S5 through the first extraction filter 322 and the second extraction filter 323, the carrier modulated signal S3 from which the noise components have been removed is extracted. The serial data signal S1 is demodulated based on the extracted carrier modulation signal S3. Therefore, the serial data signal S1 demodulated by the receiver 3 is less likely to contain noise components than the serial data signal S1 demodulated based on the carrier modulation signal S3 that has not passed through the first extraction filter unit 322 and the second extraction filter unit 323. In other words, the transmission and reception of the composite modulation signal S6 by the system 1 is less likely to fail.

[0104] ●Features of the present transmitter, the present receiver, and the present system● The features of the present transmitter, the present receiver, and the present system that have been explained so far are summarized below.

[0105] Features of the present transmitter The present transmitter (for example, the present transmitter 2) is a transmitter that transmits a composite modulated signal (for example, composite modulated signal S6) obtained by analog-modulating (for example, FM-modulating) a composite signal (for example, composite signal S5) of a carrier modulated signal (for example, carrier modulated signal S3) and an audio signal (for example, audio signal S4), wherein the carrier modulated signal is generated based on a serial data signal (for example, serial data signal S1) that stores predetermined information and a carrier signal (for example, carrier signal S2), and the audio signal is generated based on sound waves from a sound source, and the transmitter comprises: a storage unit (for example, storage unit 21) that stores the predetermined information; and a control unit (for example, control unit 22) that generates the serial data signal, wherein the serial data signal includes a preamble in which specific bits (for example, specific bit B1) and non-specific bits (for example, non-specific bit B2) are alternately arranged, and when the bit width of the non-specific bits (for example, non-specific bit width) is a reference bit width, The bit width of the specific bit (for example, the specific bit width) is M.N times the reference bit width (M, N: any integer from 1 to 9).

[0106] In the transmitter, M may be any of 1 to 3, and N may be 5.

[0107] The transmitter may include a carrier signal generating unit (e.g., carrier signal generating unit 24) that generates a carrier signal, a filter unit (e.g., filter unit 23) that performs linear processing on the rising and falling edges of the serial data signal, and a carrier signal modulating unit (e.g., carrier signal modulating unit 25) that modulates the carrier signal with the serial data signal that has been linearly processed to generate a carrier modulated signal.

[0108] Features of the Receiver The receiver (for example, the receiver 3) receives a composite modulated signal (for example, composite modulated signal S6) obtained by analog-modulating (for example, FM-modulating) a composite signal (for example, composite signal S5) of a carrier modulated signal (for example, carrier modulated signal S3) and an audio signal (for example, audio signal S4), wherein the carrier modulated signal is generated based on a serial data signal (for example, serial data signal S1) storing predetermined information and a carrier signal (for example, carrier signal S2), and the audio signal is generated based on sound waves from a sound source, and the receiver comprises: a signal extraction unit (for example, signal extraction unit 32) that extracts the carrier modulated signal from the composite modulated signal; an A / D conversion unit (for example, A / D conversion unit 33) that converts the extracted carrier modulated signal into a digital signal; and an information extraction unit (for example, data signal output unit 34) that extracts predetermined information from the converted digital signal, and the serial data signal is The digital signal includes a preamble in which specific bits (e.g., specific bit B1) and non-specific bits (e.g., non-specific bit B2) are alternately arranged, and when the bit width of the non-specific bits (e.g., non-specific bit width) is a reference bit width, the bit width of the specific bits (e.g., specific bit width) is M.N times the reference bit width (M, N: any integer from 1 to 9), and the information extraction unit extracts predetermined information from the digital signal based on the bit width of the specific bits.

[0109] In the receiver, M may be any of 1 to 3, and N may be 5.

[0110] In this receiver, the signal extraction unit may include a demodulation unit (e.g., demodulation unit 321) that demodulates a composite signal from a composite modulated signal, a first extraction filter unit (e.g., first extraction filter unit 322) that extracts a carrier modulated signal from the demodulated composite signal, and a second extraction filter unit (e.g., second extraction filter unit 323) that removes noise components from the extracted carrier modulated signal.

[0111] In the receiver, the first extraction filter unit may be a band-pass filter, and the second extraction filter unit may be a low-pass filter.

[0112] ●Features of the present system The present system (for example, the present system 1) comprises: a transmitter that transmits a composite modulated signal (for example, the composite modulated signal S6) that is obtained by analog-modulating (for example, FM-modulating) a composite signal (for example, the composite signal S5) of a carrier modulated signal (for example, the carrier modulated signal S3) and an audio signal (for example, the audio signal S4); and a receiver that receives the composite modulated signal, wherein the carrier modulated signal is generated based on a serial data signal (for example, the serial data signal S1) that stores predetermined information and a carrier signal (for example, the carrier signal S2), and the audio signal is generated based on sound waves from a sound source, the transmitter is the present transmitter (for example, the present transmitter 2), and the receiver is the present receiver (for example, the present receiver 3).

[0113] REFERENCE SIGNS LIST 1 Transmission / reception system 2 Transmitter 21 Memory unit 22 Control unit 23 Filter unit 24 Carrier signal generation unit 25 Carrier signal modulation unit 26 Audio signal generation unit 27 Synthesis unit 28 Synthesis signal modulation unit 29 Transmission unit 3 Receiver 31 Receiving unit 32 Signal extraction unit 321 Demodulation unit 322 First extraction filter unit 323 Second extraction filter unit 33 A / D conversion unit 34 Data signal output unit 35 Audio signal processing unit 36 ​​Audio signal output unit 4 Audio output device 5 Data output device S1 Serial data signal S2 Carrier signal S3 Carrier modulated signal S4 Audio signal S5 Synthesis signal S6 Synthesis modulated signal P Specific pattern B1 Specific bit B2 Non-specific bit

Claims

1. A transmitter that transmits a composite modulation signal obtained by analog-modulating a composite signal of a carrier modulation signal and an audio signal, wherein the carrier modulation signal is generated based on a serial data signal storing predetermined information and a carrier signal, the audio signal is generated based on a sound wave from a sound source, the transmitter includes a storage unit that stores the information and a control unit that generates the serial data signal, the serial data signal includes a preamble in which specific bits and non-specific bits are alternately arranged, and when the bit width of the non-specific bit is a reference bit width, the bit width of the specific bit is M.N times (M, N: any integer from 1 to 9) the reference bit width.

2. The transmitter according to claim 1, wherein M is any one of 1 to 3 and N is 5.

3. The transmitter according to claim 1, further including a carrier signal generation unit that generates the carrier signal, a filter unit that performs linear processing on a rising edge and a falling edge of the serial data signal, and a carrier signal modulation unit that modulates the carrier signal with the serial data signal on which the linear processing has been performed to generate the carrier modulation signal.

4. A receiver that receives a composite modulation signal obtained by analog-modulating a composite signal of a carrier modulation signal and an audio signal, wherein the carrier modulation signal is generated based on a serial data signal storing predetermined information and a carrier signal, the audio signal is generated based on a sound wave from a sound source, the receiver includes a signal extraction unit that extracts the carrier modulation signal from the composite modulation signal, an A / D conversion unit that converts the extracted carrier modulation signal into a digital signal, and an information extraction unit that extracts the information from the converted digital signal, the serial data signal includes a preamble in which specific bits and non-specific bits are alternately arranged, and when the bit width of the non-specific bit is a reference bit width, the bit width of the specific bit is M.N times (M, N: any integer from 1 to 9) the reference bit width, and the information extraction unit extracts the information from the digital signal based on the bit width of the specific bit.

5. The receiver according to claim 4, wherein M is any one of 1 to 3 and N is 5.

6. The receiver according to claim 4, wherein the signal extraction unit includes a demodulation unit that demodulates the composite signal from the composite modulation signal, a first extraction filter unit that extracts the carrier modulation signal from the demodulated composite signal, and a second extraction filter unit that removes noise components from the extracted carrier modulation signal.

7. The receiver according to claim 6, wherein the first extraction filter unit is a band-pass filter and the second extraction filter unit is a low-pass filter.

8. A transmission and reception system comprising a transmitter that transmits a composite modulation signal obtained by analog-modulating a composite signal of a carrier modulation signal and an audio signal, and a receiver that receives the composite modulation signal, wherein the carrier modulation signal is generated based on a serial data signal storing predetermined information and a carrier signal, the audio signal is generated based on a sound wave from a sound source, the transmitter is the transmitter according to claim 1, and the receiver is the receiver according to claim 4.

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