RECEIVING DEVICE, RECEIVING METHOD AND RECEIVING SYSTEM

Abstract

Receiving device, comprising: a frequency mixer (11) configured to mix a received signal input therein and a local signal generated by a local oscillator (12) in order to convert a frequency of the received signal into a baseband; an envelope demodulator (13) configured to perform an envelope demodulation of an output of the frequency mixer (11); an upper sideband demodulator (14) configured to demodulate only one upper sideband of an output from the frequency mixer (11) by single-sideband demodulation; a lower sideband demodulator (15) configured to demodulate only one lower sideband of the output from the frequency mixer (11) by single-sideband demodulation; a first adder (16) configured to add an output from the envelope demodulator (13) and a first inverted output obtained by inverting an output from the upper sideband demodulator (14); a second adder (17) configured to add the output from the envelope demodulator (13) and a second inverted output obtained by inverting an output from the lower sideband demodulator (15); and a third adder (18) configured to add the output from the envelope demodulator (13), a third inverted output obtained by inverting an output from the first adder, and a fourth inverted output obtained by inverting an output from the second adder to produce a demodulation signal.

Description

[0001] The present disclosure relates to a receiving device, a receiving method and a receiving system that receives a radio signal, such as an AM broadcast wave.

[0002] In a receiving device, such as a car radio receiver, a method can be used to reduce the influence of noise radiated by other electronic devices by employing noise reduction components or circuits, such as filters and noise suppressors. In a car AM radio receiver, the problem is that a desired wave is suppressed by interference from a wave component that differs from a broadcast signal from a radio station. Because AM broadcasting operates at low frequencies, it interferes with various noise signals, such as unwanted emissions from generators, power lines, and devices within the vehicle. If noise is primarily radiated from an electronic device within the vehicle, such as...The noise generated by the vehicle's engine or inverter is mixed in a radio antenna and interferes with a broadcast wave from a radio station. In an AM radio receiver for vehicles, this noise therefore enters the radio audio signal, into which a received signal is demodulated, resulting in a harsh and unpleasant sound.

[0003] Fig. Figure 3 is a diagram showing the operation of an AM radio receiver when noise is mixed. An AM broadcast signal received by an antenna is input to an analog-to-digital converter (ADC) 501 and converted into a digital receive RF signal. The digital receive signal is input to a frequency mixer (Mixer) 502 and multiplied in the mixer by a local signal, which has the same frequency as a received broadcast wave and is output by a local oscillator (LO) 503, and is converted into a receive baseband signal of 0 Hz (baseband). The received baseband signal is input to an AM demodulator 504, is demodulated by detection of an envelope by a corresponding detector, and is then input to a D / A converter (DAC: Digital to Analog Converter) 505, converted into an analog signal, and output as an audio signal of a radio broadcast.

[0004] If a frequency of a pulsed narrowband noise signal has a period close to the frequency of the received broadcast signal, such as hammering noise generated by an inverter or a windshield wiper motor, then another frequency component can be demodulated with a carrier frequency of the received broadcast signal as an audio signal. In the example of the Fig. Figure 3 shows two types of hammer noise, B1 and B2, superimposed on an AM broadcast wave. When the two noise signals are not mixed, an audio signal S is output as the output signal of the D / A converter 505 after demodulation of the received signal. When the hammer noise signals are superimposed, one hammer noise component is mixed into the output of the AM demodulator 504, and (S+B1+B2) is output as the output signal.

[0005] A prior art technique for reducing this type of noise is known in which a noise suppressor includes an analog switch which is fed with an audio signal containing pulse noise as input, is switched on and off by a control signal, is switched off during one period of the pulse noise, and outputs an audio signal in which the pulse noise is blocked, and includes a voltage-holding circuit connected to the analog switch, which holds a voltage immediately before switching off as an interpolation voltage for the off period of the analog switch, and interpolates an audio signal from the analog switch with noise (see, for example, patent document 1).Also known is an AM noise suppressor mounted on a multifunctional tuner IC, wherein noise from an AM signal is removed by focusing on a noise removal power of a noise pulse in a weak electric field which is most disturbing during reception of the AM signal (see, e.g., non-patent document 1).

[0006] In the state of the art, as in Fig. As shown in Figure 4, harsh noise is removed by cutting off a high-frequency component of the pulse noise, which has a shorter period than the hammering noise mixed into the received wave of the AM signal, and which has a predetermined frequency and threshold amplitude, and is replaced by a straight line.

[0007] Patent document 1: JP H03 - 238 929 A

[0008] Non-patent document 1: Fujitsu Ten Technical Journal No. 33, published April 1998, pp. 12-22

[0009] AM radio receivers with functions for reducing interference signals contained in the received signal, especially pulsed interference signals, are also known from JP 2010 - 178 227 A, US 2013 / 0 010 977 A1 and JP 2004 - 254 184 A.

[0010] In recent years, noise sources, such as a PWM signal controlling a motor, have increased, thereby raising the importance of noise reduction measures and increasing the demands on noise suppression performance. To improve the noise reduction effect using state-of-the-art methods, it is necessary to lower the noise reduction threshold. However, since this can also result in the attenuation of audio components along with the noise as a side effect, due to the threshold's amplitude level and a frequency error, distortions occur in the audio signal, and harmonic components are generated. Consequently, a problem arises: defects in the audio information appear in the received audio signal, distortion or crackling noises are produced, and the sound quality is degraded.

[0011] The present disclosure was created in view of the circumstances described above in the prior art and one objective of the present disclosure is to provide a receiving device, a receiving method and a receiving system that is capable of removing noise with minimal impairment of the original audio information, even when the noise occurs.

[0012] The present disclosure specifies a receiving device comprising: a frequency mixer configured to mix a received signal input therein and a local signal generated by a local oscillator in order to convert a frequency of the received signal into a baseband; an envelope demodulator configured to perform envelope demodulation on an output of the frequency mixer; an upper sideband demodulator configured to demodulate only an upper sideband of the output from the frequency mixer by single-sideband demodulation; a lower sideband demodulator configured to demodulate only a lower sideband of the output from the frequency mixer by single-sideband demodulation;a first adder configured to add an output from the envelope demodulator and an inverted output obtained by inverting an output from the upper sideband demodulator; a second adder configured to add the output from the envelope demodulator and an inverted output obtained by inverting an output from the lower sideband demodulator; and a third adder configured to add the output from the envelope demodulator, an inverted output obtained by inverting an output from the first adder, and an inverted output obtained by inverting an output from the second adder to produce a demodulation signal.

[0013] The present disclosure specifies a receiving system comprising: a receiving signal input circuit configured to input a received signal of a radio wave; a demodulation processor configured to perform demodulation processing on the received signal;and an audio signal output circuit configured to output a demodulated signal as audio, wherein the receive signal input circuit includes an antenna configured to receive a radio wave of a desired frequency and an input signal amplifier configured to amplify a received signal, wherein the audio signal output circuit includes an output signal amplifier configured to amplify a demodulated signal and an audio output device configured to output an amplified signal as an audio signal, and wherein the demodulation processor includes: a frequency mixer configured to mix the received signal input from the receive signal input circuit and a local signal generated by a local oscillator in order to convert a frequency of the received signal into a baseband;an envelope demodulator configured to perform envelope demodulation on an output from the frequency mixer; an upper sideband demodulator configured to demodulate only an upper sideband of the output from the frequency mixer by single-sideband demodulation; a lower sideband demodulator configured to demodulate only a lower sideband of the output from the frequency mixer by single-sideband demodulation; a first adder configured to add an output from the envelope demodulator and an inverted output obtained by inverting an output from the upper sideband demodulator; a second adder configured to add the output from the envelope demodulator and an inverted output obtained by inverting an output from the lower sideband demodulator;and a third adder configured to add the output from the envelope demodulator, an inverted output obtained by inverting an output from the first adder, and an inverted output obtained by inverting an output from the second adder to produce the demodulation signal.

[0014] The present disclosure specifies a receiving method comprising: causing a frequency mixer to mix a received signal input therein and a local signal generated by a local oscillator in order to convert a frequency of the input signal into a baseband; causing an envelope demodulator to perform an envelope demodulation on an output from the frequency mixer; causing an upper sideband demodulator to demodulate only an upper sideband of the output from the frequency mixer by single-sideband demodulation; causing a lower sideband demodulator to demodulate only a lower sideband of the output from the frequency mixer by single-sideband demodulation; causing a first adder to add an output from the envelope demodulator and an inverted output obtained by inverting an output from the upper sideband demodulator;To cause a second adder to add the output from the envelope demodulator and an inverted output obtained by inverting an output from the lower sideband demodulator; and to cause a third adder to add the output from the envelope demodulator, an inverted output obtained by inverting an output from the first adder, and an inverted output obtained by inverting an output from the second adder, in order to output a demodulation signal.

[0015] According to the present disclosure, it is possible, even if noise is generated, to remove only the noise without affecting the original audio information. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a block diagram showing a configuration of a receiving device and a receiving system according to one embodiment. Fig. Figure 2 is a diagram showing the operation of the receiving device according to the embodiment. Fig. Figure 3 is a diagram showing the operation when noise is mixed in an AM radio receiver. Fig. Figure 4 is a waveform diagram showing a state-of-the-art noise reduction operation. DESCRIPTION OF THE EXECUTION FORMS

[0016] In the following, embodiments of a receiving device, a receiving method, and a receiving system according to the present disclosure are described in detail, with reference, where appropriate, to the accompanying drawings. Detailed descriptions beyond what is necessary may be omitted. For example, in some cases, the detailed description of a previously known subject matter and redundant descriptions of components that are essentially the same are omitted. This serves to avoid unnecessary redundancies in the following description and to facilitate understanding by the person skilled in the art. The accompanying drawings and the following description are intended to provide the person skilled in the art with a complete understanding of the present disclosure and are not intended to limit the subject matter described in the claims.

[0017] In the present embodiment, the receiving device, the receiving method and the receiving system according to the present disclosure are presented as examples, and, for example, a configuration example applicable to an AM radio receiver installed in a vehicle is shown.

[0018] Fig. Figure 1 is a block diagram showing a configuration of the receiver and the receiving system according to the embodiment. The receiver of the present embodiment includes a demodulation processor 10, which demodulates a radio signal, such as an AM broadcast signal. The receiving system of the present embodiment includes, as a receiving signal input circuit, an antenna 31, an amplifier 32, and an analog-to-digital converter (ADC) 33. The receiving system further includes, as an audio signal output circuit, a digital-to-analog converter (DAC) 34, an amplifier 35, and a loudspeaker 36.

[0019] Antenna 31 receives a radio signal, such as an AM broadcast signal. Amplifier 32 is an example of an input signal amplifier and contains an amplifier that amplifies an RF (radio frequency band) receive signal. A / D converter 33 converts the RF receive signal from an analog signal into a digital signal and inputs the digital signal to the demodulation processor 10. The receive signal input circuit can be formed by an input interface or the like to input a receive signal of a radio wave of the desired frequency.

[0020] The D / A converter 34 converts a demodulation signal from a digital signal output by the demodulation processor 10 into an analog signal. The amplifier 35 is an example of an output signal amplifier and contains an amplifier that amplifies an audio signal obtained by converting the demodulation signal into the analog signal. The loudspeaker 36 is an example of an audio output device that reproduces and outputs an audio signal, such as an AM radio signal. The audio output device is not limited to the loudspeaker 36, and various devices, such as headphones, earphones, and headsets, can be used. The audio signal output circuit can be formed by an output interface or the like for outputting an audio signal from a demodulation signal.

[0021] The demodulation processor 10 includes a frequency mixer 11, a local oscillator (LO) 12, an envelope demodulator (AM DEM) 13, an upper sideband demodulator (USB DEM) 14, a lower sideband demodulator (LSB DEM) 15, adders 16, 17, 18, and inverter circuits 21, 22, 23, 24. The demodulation processor 10 can be implemented as hardware, such as by an integrated circuit on which a signal processing circuit is set up to perform the processing for each unit, or at least partially implemented by a processor, such as a digital signal processor (DSP), and a software program to operate the processor.

[0022] The local oscillator 12 contains an oscillator, e.g., a numerically controlled oscillator (NCO) 12 or the like, and generates a local signal with the same frequency as the carrier frequency of an RF receive signal. The frequency mixer 11 performs a mixing process in which the received signal of the RF digital signal (digital receive signal) input by the A / D converter 33 is multiplied by the local signal output by the local oscillator 12, and the digital receive signal is frequency-converted into a receive signal in a baseband (receive baseband signal). The received baseband signal is input to the envelope demodulator 13, the upper sideband demodulator 14, and the lower sideband demodulator 15.

[0023] The envelope demodulator 13 contains, for example, a demodulation circuit, such as an envelope detector, forming a so-called AM demodulator and demodulating the received signal by envelope detection. The upper sideband demodulator 14 has, for example, a single-sideband (SSB) demodulation circuit and demodulates only one upper sideband of the received signal by SSB synchronous demodulation. The upper sideband demodulator 14 multiplies the received signal by a clock signal, which serves as a synchronization signal and is synchronized with a carrier wave, and shifts the phase by 90 degrees using a 90-degree phase shifter in order to extract and demodulate only the upper sideband. The lower sideband demodulator 15 contains, for example, a single-sideband (SSB) demodulator circuit and demodulates only one upper sideband of the received signal by SSB synchronous demodulation. B. an SSB demodulation circuit and demodulates only a lower sideband of the received signal by SSB synchronous demodulation.The lower sideband demodulator 15 multiplies the received signal by a clock signal, which serves as a synchronization signal and is synchronized with a carrier wave, and shifts a phase by 90 degrees in the opposite direction to the upper sideband demodulator 14 by a 90-degree phase shifter, in order to extract and demodulate only the lower sideband.

[0024] Inverter circuits 21, 22, 23, and 24 each contain, for example, a phase inverter and invert the + / - polarity of an input signal by inverting one phase of the input signal. Inverter circuit 21 inverts the output of the upper sideband demodulator 14. Inverter circuit 23 inverts the output of the lower sideband demodulator 15.

[0025] Adder 16 is an example of the first adder and receives and adds the output from the envelope demodulator 13 and the output from the inverter circuit 21. That is, adder 16 adds the output from the envelope demodulator 13 and the inverted output from the upper sideband demodulator 14. Adder 17 is an example of the second adder and receives and adds the output from the envelope demodulator 13 and the output from the inverter circuit 23. That is, adder 17 adds the output from the envelope demodulator 13 and the inverted output from the lower sideband demodulator 15. Inverter circuit 22 inverts the output from adder 16. Inverter circuit 24 inverts the output from adder 17.The adder 18 is an example of the third adder and receives and adds the output from the envelope demodulator 13, the output from the inverter circuit 22 and the output from the inverter circuit 24 and outputs a demodulation signal.

[0026] Fig. Figure 2 is a diagram illustrating the operation of the receiving device according to the embodiment. The operation of the receiving device and the sequence of the reception procedure according to the present embodiment are described with reference to Fig. 2 described. The following describes an operation for the case where hammering noise is mixed into a radio signal and two types of hammering noise, B1 and B2, are superimposed in a received signal of a receiving wave input received by antenna 31. In the example shown, the hammering noise B1 is mixed into the lower sideband, and the hammering noise B2 is mixed into the upper sideband.

[0027] In the present embodiment, the upper sideband demodulator 14 and the lower sideband demodulator 15 are additionally provided on the output side of the frequency mixer 11, in addition to the envelope demodulator 13, the adders 16, 17, 18 and the inverter circuits 21, 22, 23, 24 for subtracting the output of the upper sideband demodulator 14 and the lower sideband demodulator 15 from the output of the envelope demodulator 13.

[0028] An AM broadcast signal, serving as the desired wave, has a spectrum in which the upper and lower sidebands are symmetrical with respect to a carrier signal on the frequency axis. However, in a radio signal containing noise, the spectrum of the signal is asymmetrical between the upper and lower sidebands. In the present embodiment, a noise component is extracted by removing a component that is asymmetrical between the upper and lower sidebands. Subsequently, only the noise component is suppressed by subtracting it from the envelope demodulation signal of the radio signal.

[0029] In the envelope demodulation of the received signal, performed by the envelope demodulator (AM DEM) 13, the noise contained in the upper and lower sidebands is demodulated along with the broadcast wave of the desired frequency, and a demodulation signal containing the noise is output. Therefore, in a signal D1 processed by the envelope demodulator 13, the hammer noise B1 and the hammer noise B2 are superimposed on an audio signal S obtained by demodulating the two sideband waves, and the signal D1 = (S+B1+B2) is output by the envelope demodulator 13.

[0030] A signal U1, processed by the upper sideband demodulator (USB DEM) 14, contains the audio signal S, obtained by single-sideband demodulation, and the hammering noise B2. Therefore, the signal U1 = (S+B2) is output by the upper sideband demodulator 14. Furthermore, by inverting one phase using the inverter circuit 21, a signal -U1 = (-S-B2) is obtained.

[0031] A signal L1, processed by the lower sideband demodulator (LSB DEM) 15, contains the audio signal S, obtained by single-sideband demodulation, and the hammering noise B1. Therefore, the signal L1 = (S+B1) is output by the lower sideband demodulator 15. Furthermore, by inverting one phase using the inverter circuit 23, the signal -L1 = (-S-B1) is obtained.

[0032] Next, the hammering noise B2 is extracted by adding signal D1 and signal -U1 using adder 16. Additionally, the hammering noise B1 is extracted by adding signal D1 and signal -L1 using adder 17. An output signal U2 from adder 16 is U2 = U1 + D1 = (-S - B2) + (S + B1 + B2) = B1. An output signal L2 from adder 17 is L2 = -L1 + D1 = (-S - B1) + (S + B1 + B2) = B2.

[0033] As described above, by determining a difference between the envelope demodulation signal and the upper sideband demodulation signal or the lower sideband demodulation signal, each demodulated by single sideband demodulation, it is possible to extract only one noise component of the hammering noise of the upper sideband or the lower sideband.

[0034] Furthermore, by inverting one phase using inverter circuit 22, a signal -U2 = -B1 is obtained. By inverting one phase using inverter circuit 24, a signal -L2 = -B2 is obtained. Subsequently, by adding the signal D1, the signal -U2, and the signal -L2 using adder 18, only the audio signal S is extracted. An output signal D2 from adder 18 is D2 = D1 - U2 - L2 = (S+B1+B2) - B1 - B2 = S.

[0035] As described above, the noise components of the upper and lower sidebands, which were extracted as described above, are subtracted from the envelope demodulation signal, and it is thus possible to suppress only the hammering noise from the demodulation signal of the radio signal of the received wave.

[0036] In a case where the configuration of the present embodiment is applied to an actual device, a delay device is required to compensate for a delay in the required processing time in each process, but its description is skipped here because the description is complicated.

[0037] In the processing described above, a demodulation signal, obtained by extracting only the audio signal S of the desired waveform, is output as demodulated audio. According to the present embodiment, it is possible to specify an AM receiver noise suppressor that suppresses only one signal component of the hammering noise without affecting the original audio information.

[0038] According to the present embodiment, the hammering noise can be suppressed provided that other noise is present which interferes with a receiving device, such as an AM radio receiver, to produce hammering noise, such as the motor noise of an electric vehicle and clock noise within the receiver, or the like. If, for example, the motor is driven by a PWM signal, noise mixed into the received signal can even be removed for noise sources whose frequency and amplitude change along with the motor. In a receiving system with an AM radio receiver or the like, it is therefore possible to output a good audio signal of a desired wave with minimal impairment of the sound quality.

[0039] As described above, the receiver of the present embodiment includes the frequency mixer 11, which is configured to mix a received signal received by the antenna 31 and a local signal generated by the local oscillator 12 in order to convert a frequency of the received signal into a baseband. The receiver includes the single-envelope demodulator 13, which is configured to perform single-envelope demodulation on the output of the frequency mixer 11; the upper-sideband demodulator 14, which is configured to demodulate only the upper sideband of the output of the frequency mixer 11 by single-sideband demodulation; and the lower-sideband demodulator 15, which is configured to demodulate only the lower sideband of the output of the frequency mixer 11 by single-sideband demodulation.Furthermore, the receiving device includes the adder 16, which is configured to add the output from the envelope demodulator 13 and the inverted output obtained by inverting the output from the upper sideband demodulator 14; the adder 17, which is configured to add the output from the envelope demodulator 13 and the inverted output obtained by inverting the output from the lower sideband demodulator 15; and the adder 18, which is configured to add the output from the envelope demodulator 13, the inverted output obtained by inverting the output from the adder 16, and the inverted output obtained by inverting the output from the adder 17, and to output a demodulation signal.

[0040] In the configuration described above, the noise component contained in the lower sideband of the received signal can be extracted by adding the envelope demodulation signal and the inverted output of the upper sideband demodulation signal. Furthermore, the noise component contained in the upper sideband of the received signal can be extracted by adding the envelope demodulation signal and the inverted output of the lower sideband demodulation signal. Finally, the noise component contained in the upper and lower sidebands can be suppressed in the envelope demodulation output of the received signal by adding the envelope demodulation signal and the inverted output of the extracted lower and upper sideband noise components.It is therefore possible to output the demodulation signal obtained by removing only the noise component from the received signal in order to extract the audio signal of the desired wave. Thus, it is possible to specify an AM receiver noise suppressor that removes only one signal component of a hammering noise without affecting the original audio information of the received signal, even if the noise is present.

[0041] The receive signal of the present embodiment comprises the receive signal input circuit, which is configured to input a received signal of a radio wave, a demodulation processor 10, which is configured to perform demodulation processing on the received signal, and the audio signal output circuit, which is configured to output a demodulated signal as an audio signal. The receive signal input circuit comprises the antenna 31, which is configured to receive a radio wave of a desired frequency, and an amplifier 32, which is configured to amplify a received signal. The audio signal output circuit comprises the amplifier 35, which is configured to amplify a demodulated signal, and the loudspeaker 36, which is configured to output an amplified signal as an audio signal.The demodulation processor 10 includes a frequency mixer 11, which is configured to mix a received signal input from the receive signal input circuit and a local signal generated by the local oscillator 12 in order to convert a frequency of the received signal into a baseband; the envelope demodulator 13, which is configured to perform an envelope demodulation of the output from the frequency mixer 11; the upper sideband demodulator 14, which is configured to demodulate only the upper sideband of the output from the frequency mixer 11 by single-sideband demodulation; and the lower sideband demodulator 15, which is configured to demodulate only the lower sideband of the output from the frequency mixer 11 by single-sideband demodulation.Furthermore, the demodulation processor 10 includes the adder 16, which is configured to add the output from the envelope demodulator 13 and the inverted output obtained by inverting the output from the upper sideband demodulator 14; the adder 17, which is configured to add the output from the envelope demodulator 13 and the inverted output obtained by inverting the output from the lower sideband demodulator 15; and the adder 18, which is configured to add the output from the envelope demodulator 13, the inverted output obtained by inverting the output from the adder 16, and the inverted output obtained by inverting the output from the adder 17, in order to output a demodulation signal.

[0042] Thus, it is possible to output the demodulation signal obtained by removing only the noise components from the received signal in order to extract the audio signal of the desired waveform. Consequently, it is possible to specify a receiving system in which it is possible to suppress only one signal component of a hammering noise without affecting the original audio information of the received signal, even if the noise is present, and it is possible to output a good audio signal with minimal degradation of sound quality.

[0043] Furthermore, the reception method of the present embodiment includes instructing the frequency mixer 11 to mix the input received signal and the local signal generated by the local oscillator in order to convert the frequency of the received signal into a baseband, and instructing the envelope demodulator 13 to perform envelope demodulation on the output of the frequency mixer 11. The reception method further includes instructing the upper sideband demodulator 14 to demodulate only the upper sideband of the output from the frequency mixer 11 using single-sideband demodulation, and instructing the lower sideband demodulator 15 to demodulate only the lower sideband of the output from the frequency mixer 11 using single-sideband demodulation.The receiving procedure further includes instructing adder 16 to add the output from envelope demodulator 13 and the inverted output obtained by inverting the output from upper sideband demodulator 14, and instructing adder 17 to add the output from envelope demodulator 13 and the inverted output obtained by inverting the output from lower sideband demodulator 15. The receiving procedure further includes instructing adder 17 to add the output from envelope demodulator 13, the inverted output obtained by inverting the output from adder 16, and the inverted output obtained by inverting the output from adder 17, in order to output a demodulation signal.

[0044] Since it is thus possible to output the demodulation signal obtained by removing only the noise component in the received signal to extract the audio signal of the desired wave, and it is possible to suppress only a signal component of a hammering noise without affecting the original audio information of the received signal, even if the noise is present.

[0045] Although various embodiments have been described above with reference to the drawings, it is self-evident that the present disclosure is not limited to these examples. It is obvious that a person skilled in the art can devise various modifications or corrections within the scope of protection defined by the claims, and that such modifications or corrections are to be considered as belonging to the technical scope of the present disclosure. Furthermore, the components according to the embodiments described above can be freely combined with one another without deviating from the scope of the present disclosure.

[0046] This application is based on Japanese patent application no. 2018-066238, filed on March 29, 2018, the contents of which are hereby incorporated by reference. INDUSTRIAL APPLICABILITY

[0047] The present disclosure is useful as a receiving device, receiving method and receiving system which are capable of removing only noise without affecting the original audio information, even when the noise is present. REFERENCE MARK LIST 10 Demodulation processor 11 frequency mixers 12 Local oscillator 13 Envelope demodulator 14 Upper sideband demodulator 15 Lower sideband demodulator 16, 17, 18 Adders 21, 22, 23, 24 Inverter circuit 31 Antenna 32 amplifiers 33 A / D converters 34 D / A converters 35 amplifiers 36 speakers

Claims

[1] Receiving device comprising: a frequency mixer (11) configured to mix a received signal input therein and a local signal generated by a local oscillator (12) in order to convert a frequency of the received signal into a baseband; an envelope demodulator (13) configured to perform an envelope demodulation of an output of the frequency mixer (11); an upper sideband demodulator (14) configured to demodulate only one upper sideband of an output from the frequency mixer (11) by single-sideband demodulation; a lower sideband demodulator (15) configured to demodulate only one lower sideband of the output from the frequency mixer (11) by single-sideband demodulation; a first adder (16) configured to add an output from the envelope demodulator (13) and a first inverted output obtained by inverting an output from the upper sideband demodulator (14); a second adder (17) configured to add the output from the envelope demodulator (13) and a second inverted output obtained by inverting an output from the lower sideband demodulator (15); and a third adder (18) configured to add the output from the envelope demodulator (13), a third inverted output obtained by inverting an output from the first adder, and a fourth inverted output obtained by inverting an output from the second adder to produce a demodulation signal. [2] Receiving device according to claim 1, wherein the upper sideband demodulator (14) comprises a first 90-degree phase shifter configured to shift the phase of a signal by 90 degrees obtained by multiplying the output of the frequency mixer (11) with a synchronization signal synchronized to a carrier wave, and wherein the lower sideband demodulator (15) comprises a second 90-degree phase shifter configured to shift the phase of the signal obtained by multiplying the output from the frequency mixer (11) with the synchronization signal by 90 degrees in a direction opposite to that of the first phase shifter (14). [3] Receiving device according to claim 1 or 2, further comprising: a first inverter circuit (21) configured to invert the output from the upper sideband demodulator (14) to produce the first inverted output; a second inverter circuit (23) configured to invert the output from the lower sideband demodulator (15) to produce the second inverted output; a third inverter circuit (22) configured to invert the output from the first adder (16) to produce the third inverted output; and a fourth inverter circuit (24) configured to invert the output from the second adder (17) to produce the fourth inverted output. [4] Receiving device according to claim 3, wherein the first inverter circuit (21), the second inverter circuit (23), the third inverter circuit (22) and the fourth inverter circuit (24) each comprise a phase inverter configured to invert a phase of an input signal in order to invert a polarity of the input signal. [5] Receiving system, comprising: a receiving signal input circuit designed to input a received signal from a radio wave; a demodulation processor configured to perform demodulation processing on the received signal; and an audio signal output circuit designed to output a demodulation signal as audio output, wherein the receiving signal input circuit comprises an antenna configured to receive a radio wave of a desired frequency and an input signal amplifier configured to amplify a received signal, wherein the audio signal output circuit comprises an output signal amplifier configured to amplify the demodulation signal, and an audio output device configured to output an amplified signal as an audio signal, and the demodulation processor includes: a frequency mixer (11) configured to mix the received signal input from the receive signal input circuit and a local signal generated by a local oscillator (12) in order to convert a frequency of the received signal into a baseband; an envelope demodulator (13) configured to perform an envelope demodulation on an output from the frequency mixer (11); an upper sideband demodulator (14) configured to demodulate only one upper sideband of the output from the frequency mixer (11) by single-sideband demodulation; a lower sideband demodulator (15) configured to demodulate only one lower sideband of the output from the frequency mixer (11) by single-sideband demodulation; a first adder configured to add an output from the envelope demodulator and a first inverted output obtained by inverting an output from the upper sideband demodulator (14); a second adder configured to add the output from the envelope demodulator and a second inverted output obtained by inverting an output from the lower sideband demodulator (15); and a third adder configured to add the output from the envelope demodulator, a third inverted output obtained by inverting an output from the first adder, and a fourth inverted output obtained by inverting an output from the second adder to produce the demodulation signal. [6] Receiving system according to claim 5, wherein the upper sideband demodulator (14) comprises a first 90-degree phase shifter configured to shift the phase of a signal by 90 degrees obtained by multiplying the output of the frequency mixer (11) with a synchronization signal synchronized to a carrier wave, and wherein the lower sideband demodulator (15) comprises a second 90-degree phase shifter configured to shift the phase of the signal obtained by multiplying the output from the frequency mixer (11) with the synchronization signal by 90 degrees in a direction opposite to that of the first phase shifter (14). [7] Receiving system according to claim 5 or 6, wherein the demodulation processor further comprises: a first inverter circuit (21) configured to invert the output from the upper sideband demodulator (14) to produce the first inverted output; a second inverter circuit (23) configured to invert the output from the lower sideband demodulator (15) to produce the second inverted output; a third inverter circuit (22) configured to invert the output from the first adder (16) to produce the third inverted output; and a fourth inverter circuit (24) configured to invert the output from the second adder (17) to produce the fourth inverted output. [8] Receiving procedures, including: Causing a frequency mixer (11) to mix a received signal input therein and a local signal generated by a local oscillator (12) in order to convert a frequency of the received signal into a baseband; Causing an envelope demodulator (13) to perform an envelope demodulation on an output from the frequency mixer (11); Convenience an upper sideband demodulator (14) to demodulate only one upper sideband of the output from the frequency mixer (11) by single-sideband demodulation; Convenience a lower sideband demodulator (15) to demodulate only one lower sideband of the output from the frequency mixer (11) by single-sideband demodulation; Causing a first adder to add an output from the envelope demodulator (13) and a first inverted output obtained by inverting an output from the upper sideband demodulator (14); Causing a second adder to add an output from the envelope demodulator (13) and a second inverted output obtained by inverting an output from the lower sideband demodulator (15); and Causing a third adder to add the output from the envelope demodulator (13), a third inverted output obtained by inverting an output from the first adder, and a fourth inverted output obtained by inverting an output from the second adder to produce a demodulation signal. [9] Receiving method according to claim 8, wherein the single-sideband demodulation performed by the upper sideband demodulator (14) comprises: multiplying the output from the frequency mixer (11) by a synchronization signal synchronized with a carrier wave; and shifting one phase of the multiplied signal by 90 degrees; wherein the single-sideband demodulation performed by the lower sideband demodulator (15) comprises: multiplying the output from the frequency mixer (11) by the synchronization signal; and shifting a phase of the multiplied signal by 90 degrees in a direction opposite to that of the upper sideband demodulator (14). [10] Receiving method according to claim 8 or 9, further comprising: Causing a first inverter circuit (21) to invert the output from the upper sideband demodulator (14) to produce the first inverted output; Causing a second inverter circuit (23) to invert the output from the lower sideband demodulator (15) to produce the second inverted output; Causing a third inverter circuit (22) to invert the output from the first adder (16) to produce the third inverted output; and Causing a fourth inverter circuit (24) to invert the output from the second adder (17) to produce the fourth inverted output.

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