JP2020014167A - Receiving device and receiving method - Google Patents

Abstract

To provide a receiving device capable of performing appropriate noise suppression processing according to a receiving environment and a receiving method.SOLUTION: The receiving device includes a detection unit and a noise suppression unit. The detection unit detects a radio noise environment on the basis of a fluctuation width of a carrier frequency in a reception signal of a radio wave received by a reception antenna and a U/D level which is a level ratio of an interference wave to a desired wave of the radio wave. The noise suppression unit performs a noise suppression process on the received signal according to the noise environment detected by the detection unit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a receiving device and a receiving method.

  2. Description of the Related Art Conventionally, there has been a receiving apparatus that receives a radio wave such as a radio broadcast wave and performs processing for suppressing noise included in a received signal. For example, in a receiving apparatus, there is a technique of performing noise suppression processing on a received signal when the electric field strength of a received radio wave is weak (for example, see Patent Document 1).

JP 2005-6075 A

  However, depending on the receiving environment, it is necessary to take noise countermeasures even when the electric field strength is strong. However, in the related art, there is a possibility that the noise cannot be sufficiently suppressed.

  The present invention has been made in view of the above, and an object of the present invention is to provide a receiving apparatus and a receiving method capable of performing appropriate noise suppression processing according to a receiving environment.

  In order to solve the above-described problem and achieve the object, a receiving device according to the present invention includes a detecting unit and a noise suppressing unit. The detection unit detects a noise environment of the radio wave based on a fluctuation range of a carrier frequency in a reception signal of the radio wave received by a reception antenna and a U / D level which is a level ratio of an interference wave to a desired wave of the radio wave. I do. The noise suppression unit performs a noise suppression process on the received signal according to the noise environment detected by the detection unit.

  According to the present invention, it is possible to perform appropriate noise suppression processing according to a reception environment.

FIG. 1 is a block diagram illustrating a configuration example of a receiving device according to the embodiment. FIG. 2 is an explanatory diagram for explaining the processing content of the noise suppression unit. FIG. 3 is an explanatory diagram for explaining the processing content of the noise suppression unit. FIG. 4 is an explanatory diagram for explaining the processing content of the noise suppression unit. FIG. 5 is an explanatory diagram for explaining the processing content of the noise suppression unit. FIG. 6 is an explanatory diagram for explaining the processing content of the noise suppression unit. FIG. 7 is a flowchart illustrating a processing procedure of processing performed by the receiving device according to the embodiment.

  Hereinafter, a receiving device and a receiving method according to an embodiment will be described in detail with reference to the accompanying drawings. The present invention is not limited by the embodiments described below.

  First, a configuration example of the receiving device 1 according to the embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration example of a receiving device 1 according to the embodiment.

  As shown in FIG. 1, the receiving device 1 is connected to a receiving antenna 20. The receiving antenna 20 receives, for example, radio waves including a plurality of signals transmitted from various radio broadcasting stations. A reception signal of a radio wave received by the reception antenna 20 includes a carrier wave (a desired wave or an interference wave) of a predetermined frequency (for example, an RF (Radio Frequency) band), a signal wave that is an audio signal, noise, and the like.

  In the receiving method according to the embodiment, the plurality of noise suppression processes are switched according to the noise environment. Specifically, in the receiving method according to the embodiment, a variation in a carrier frequency (frequency of a carrier wave) in a received signal and a level ratio (hereinafter, U / D level) of a desired wave and an interference wave of a radio wave are used. A noise environment of the radio wave is detected, and a noise suppression process corresponding to the detected noise environment is performed on the received signal. The noise environment indicates a reception environment of noise included in a received signal, and various examples of the noise environment will be described later.

  As described above, the receiving apparatus 1 according to the embodiment can perform appropriate noise suppression processing according to the reception environment by switching the noise suppression processing according to the noise environment.

  Hereinafter, a configuration example of the receiving device 1 according to the embodiment will be described with reference to FIG. As shown in FIG. 1, the receiving apparatus 1 according to the embodiment includes an RF / IF unit 2, an AD conversion unit 3, a detection unit 4, a detection unit 5, a noise suppression unit 6, and an output unit 7. Prepare.

  Here, the receiving device 1 includes, for example, a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a data flash, an input / output port, and various circuits.

  The CPU of the computer functions as the RF / IF unit 2, the AD conversion unit 3, the detection unit 4, the detection unit 5, the noise suppression unit 6, and the output unit 7, for example, by reading and executing a program stored in the ROM. I do.

  In addition, at least one or all of the RF / IF unit 2, the AD conversion unit 3, the detection unit 4, the detection unit 5, the noise suppression unit 6, and the output unit 7 are provided by an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable). Gate Array) or other hardware.

  Further, for example, the RAM and the data flash can store information of various programs and the like. The receiving device 1 may acquire the above-described programs and various information via another computer or a portable recording medium connected via a wired or wireless network.

  The RF / IF unit 2 extracts and amplifies a broadcast wave (desired wave) signal to be received from a received signal received by the receiving antenna 20. The RF / IF unit 2 includes a high-frequency signal (RF signal) amplifier circuit, an intermediate frequency signal (IF signal) amplifier circuit, and the like, and an IF signal as a processed signal is output to the AD conversion unit 3.

  The AD converter 3 converts an IF signal input from the RF / IF unit 2 into a digital signal. The digitally converted IF signal is output to each of the detector 4 and the detector 5.

  The detection unit 4 performs detection by a predetermined detection method using the IF signal input from the AD conversion unit 3. The detection unit 4 performs detection using a detection method determined based on an instruction from the noise suppression unit 6 described later, and such a point will be described later. As the detection method, there are, for example, synchronous detection and envelope detection.

  Synchronous detection refers to generating a first detection signal whose phase is synchronized with the carrier frequency and a second detection signal in which the phase of the first detection signal is shifted by π / 2, and respectively generating the first detection signal and the second detection signal. This is a detection method in which an audio signal is extracted by multiplying a received signal.

  Envelope detection is a detection method for extracting an envelope of a received signal that is a modulated signal. As a result, the audio signal that is the envelope of the received signal is extracted.

  The detection unit 5 detects a noise environment of a radio wave received by the reception antenna 20. Specifically, the detection unit 5 detects the noise environment of the radio wave based on the fluctuation width of the carrier frequency in the received signal and the U / D level. The detection unit 5 outputs the detected noise environment to the noise suppression unit 6.

  The noise suppression unit 6 performs a noise suppression process on the received signal according to the noise environment detected by the detection unit 5. Here, switching of the noise suppression processing by the noise suppression unit 6 will be described with reference to FIGS.

  FIG. 2 to FIG. 6 are explanatory diagrams for explaining the processing contents of the noise suppression unit 6. First, the relationship between the carrier frequency fluctuation width (frequency fluctuation) and the U / D level in each noise environment (tunnel environment, tram noise environment and adjacent station interference environment) will be described with reference to FIG. 2 to 6, the U / D level is a decibel (dB) value. In FIG. 2, it is assumed that the electric field level of the radio wave itself is relatively strong (for example, 30 dBμV or more).

  FIG. 2 shows a table showing the relationship between the frequency fluctuation (the fluctuation width of the carrier frequency) and the U / D level in each noise environment. In the table shown in FIG. 2, the frequency variation has items of “large” and “small”, and the U / D level has items of “negative value”, “$ 0”, and “positive value”.

  The frequency fluctuations “large” and “small” indicate whether the fluctuation width of the carrier frequency is equal to or greater than a predetermined threshold (“large”) or less than the threshold (“small”).

  The U / D level “negative value” indicates that the electric field level of the desired wave is higher than the electric field level of the interfering wave. The U / D level “≒ 0” indicates that the electric field level of the desired wave and the electric field level of the interfering wave are substantially the same. The U / D level “positive value” indicates that the electric field level of the desired wave is smaller than the electric field level of the interfering wave.

  In other words, when the U / D level is represented by a dB value, the U / D level “≒ 0” is a reference value of the U / D level, and the “negative value” is a U / D level lower than the reference value. And the “positive value” is a U / D level exceeding the reference value.

  As illustrated in FIG. 2, the detection unit 5 specifies a noise environment based on a combination of “frequency fluctuation” and “U / D level”.

  Specifically, the detection unit 5 separates and detects a noise environment such as a tunnel environment, a tram noise environment, and an adjacent station interference environment (weak and strong). Hereinafter, the noise suppression processing in each noise environment will be described with reference to FIGS.

  FIG. 3 shows the processing contents of the noise suppression unit 6 in a tunnel environment. In a tunnel environment, radio waves can be received by radio rebroadcast of equipment in the tunnel. In this case, however, the frequency of the desired wave may fluctuate due to the characteristics of the equipment, as shown in FIG. That is, in the tunnel environment, the frequency fluctuation is “large” and the U / D level is “negative value” (see FIG. 2).

  Therefore, when such a tunnel environment is detected, the noise suppression unit 6 performs a process of switching from synchronous detection to envelope detection as noise suppression processing. Specifically, the noise suppression unit 6 detects the noise environment (tunnel environment) in which the fluctuation range of the carrier frequency is equal to or more than a predetermined threshold value and the U / D level is less than a predetermined reference value. The detection method of No. 4 is switched from synchronous detection to envelope detection.

  As a result, even when the carrier frequency fluctuates, noise in the audio signal can be suppressed. When the tunnel environment is eliminated, the noise suppression unit 6 changes the detection method of the detection unit 4 from the envelope detection to the synchronous detection.

  Next, FIG. 4 shows the processing contents of the noise suppression unit 6 in a tram noise environment. The tram noise environment is, for example, an environment in which external noise such as tram noise of a tram or a factory radio wave is relatively strong. In such an environment, a relatively large level of external noise is mixed in the radio wave.

  For this reason, in a tram noise environment, relatively large noise occurs over a wide band. That is, in a tram noise environment, the frequency fluctuation is “large” and the U / D level is “≒ 0” (see FIG. 2).

  Therefore, when such a tram noise environment is detected, mute processing is performed as noise suppression processing. Specifically, when a noise environment (tram noise environment) where the fluctuation width of the carrier frequency is equal to or more than a predetermined threshold value and the U / D level is a predetermined reference value is detected, the noise suppression unit 6 Mute processing. When the mute process is performed as a default, the noise suppression unit 6 increases the mute amount with the detection of the tram noise environment as a trigger. This makes it possible to suppress noise derived from extraneous noise in the audio signal.

  Next, FIG. 5 shows the processing contents of the noise suppression unit 6 in the adjacent station interference environment. The adjacent station interference environment is a noise environment in which a desired signal and a radio wave (interfering signal) having a frequency adjacent to the desired signal are mixed in a received signal. FIG. 5 illustrates a noise environment in which the electric field level of the interference wave is higher than the electric field level of the desired wave, that is, the U / D level is a “positive value”.

  In such an adjacent station interference environment, the frequency fluctuation of the desired wave is small, and when the audio signal is extracted by the synchronous detection by the detection unit 4, the interference wave is also removed, so that the influence of the final noise is small. This is the same even when the U / D level is “negative value”.

  For this reason, when an adjacent station interference environment is detected, the noise suppression processing by the noise suppression unit 6 is unnecessary. Specifically, the noise suppression unit 6 prohibits the noise suppression processing when a noise environment in which the variation range of the carrier frequency is less than a predetermined threshold is detected. That is, the noise suppression unit 6 does not perform the noise suppression processing regardless of the U / D level if the frequency variation is small. Accordingly, it is possible to prevent the processing load of the receiving device 1 from increasing due to unnecessary noise suppression processing.

  Note that the noise suppression unit 6 can further distinguish the noise environment in which vehicle noise occurs by combining electric field levels. This will be described with reference to FIG. FIG. 6 is an explanatory diagram for explaining the noise suppression processing in consideration of the electric field level.

  FIG. 6 illustrates an environment in which the electric field level of the desired wave is weak, that is, the electric field level is less than a predetermined threshold (weak electric field environment). In a weak electric field environment, for example, when the vehicle noise shown in FIG. 6 occurs over a wide band, noise may not be detected at normal noise detection sensitivity. The vehicle noise includes, for example, radio waves periodically generated in the vehicle-mounted system.

  When such a weak electric field environment is detected, the noise suppression unit 6 determines the environment based on the fact that the frequency of the desired wave does not fluctuate, and increases the noise detection sensitivity. Specifically, the noise suppression unit 6 performs a noise blanker process when detecting a noise environment (a weak electric field environment) in which the variation range of the carrier frequency is less than the predetermined threshold and the electric field level is less than the predetermined threshold. Increase sensitivity. The noise blanker process is a process of removing a received signal for a very short time (several milliseconds) at regular time intervals.

  That is, the noise suppression unit 6 can reduce noise by removing signals other than the desired wave by the noise blanker process from the received signal.

  As described above, the noise suppression unit 6 performs the noise suppression process on the received signal according to the noise environment, and then outputs the processed signal to the output unit 7.

  Returning to FIG. 2, the output unit 7 will be described. The output unit 7 converts the signal output from the noise suppression unit 6 into an analog signal and outputs the analog signal to an external device such as a speaker.

  Next, a processing procedure of processing executed by the receiving device 1 according to the embodiment will be described with reference to FIG. FIG. 7 is a flowchart illustrating a processing procedure of processing performed by the receiving device 1 according to the embodiment.

  As shown in FIG. 7, first, the detection unit 5 reads a sensor value indicating the electric field level of the received signal, the fluctuation width of the carrier frequency, and the U / D level (step S101). Subsequently, the detection unit 5 determines whether or not the environment is a weak electric field in which the electric field level is less than a predetermined threshold (Step S102).

  When a weak electric field environment is detected by the detection unit 5 (Step S102, Yes), the noise suppression unit 6 increases the sensitivity of the noise blanker process (Step S103). On the other hand, when the weak electric field environment is not detected by the detection unit 5, that is, when the environment is a strong electric field environment (No at Step S <b> 102), the noise suppression unit 6 maintains the sensitivity of the noise blanker process at the normal value (Step S <b> 104). .

  After the processing of step S103 or step S104, the detection unit 5 determines whether or not the noise environment is a tunnel environment (step S105). When the tunnel environment is detected by the detection unit 5 (Yes at Step S105), the noise suppression unit 6 switches the detection method of the detection unit 4 from synchronous detection to envelope detection (Step S106).

  On the other hand, when the detection unit 5 does not detect the tunnel environment (No in Step S105), the noise suppression unit 6 maintains the detection method of the detection unit 4 as the synchronous detection (Step S107).

  After the processing in step S106 or step S107, the detection unit 5 determines whether the noise environment is a tram noise environment (step S108). When the detection unit 5 detects a tram noise environment (Yes at Step S108), the noise suppression unit 6 increases the mute amount as noise suppression processing (Step S109), and ends the processing.

  On the other hand, when the detection unit 5 does not detect the tram noise environment (No at Step S108), the noise suppression unit 6 maintains the mute amount as normal as the noise suppression process (Step S110), and ends the process.

  As described above, the receiving device 1 according to the embodiment includes the detecting unit 5 and the noise suppressing unit 6. The detection unit 5 detects the noise environment of the radio wave based on the fluctuation range of the carrier frequency in the reception signal of the radio wave received by the reception antenna 20 and the U / D level which is the level ratio of the interference wave to the desired wave of the radio wave. . The noise suppression unit 6 performs a noise suppression process on the received signal according to the noise environment detected by the detection unit 5. This makes it possible to perform appropriate noise suppression processing according to the reception environment.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1 Receiving apparatus 2 RF / IF part 3 AD conversion part 4 Detection part 5 Detection part 6 Noise suppression part 7 Output part 20 Receiving antenna

Claims (5)

A detection unit that detects a noise environment of the radio wave based on a variation range of a carrier frequency in a reception signal of the radio wave received by the reception antenna and a U / D level that is a level ratio of a desired wave and an interference wave of the radio wave;
A noise suppression unit that performs a noise suppression process on the received signal according to the noise environment detected by the detection unit. Further comprising a detection unit for detecting the received signal,
The noise suppression unit includes:
When the noise environment in which the fluctuation width is equal to or more than a predetermined threshold value and the U / D level is less than a predetermined reference value is detected, the detection method of the detection unit is switched from synchronous detection to envelope detection. The receiving device according to claim 1, wherein The noise suppression unit includes:
The mute process is performed on the received signal when the noise environment in which the fluctuation width is equal to or more than a predetermined threshold value and the U / D level is a predetermined reference value is detected. Or the receiving device according to 2. The noise suppression unit includes:
The reception device according to any one of claims 1 to 3, wherein the noise suppression process is prohibited when the noise environment in which the fluctuation width is less than a predetermined threshold is detected. A detection step of detecting a noise environment of the radio wave based on a fluctuation range of a carrier frequency in a reception signal of the radio wave received by the reception antenna and a U / D level which is a level ratio of an interference wave to a desired wave of the radio wave;
A noise suppressing step of performing a noise suppressing process on the received signal according to the noise environment detected by the detecting step.

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