JP7175116B2 - Receiving device and receiving method - Google Patents

Description

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

2. Description of the Related Art Conventionally, for example, there are receiving apparatuses that receive radio waves such as radio broadcast waves and perform processing to suppress noise contained in the received signals. For example, in a receiving device, there is a technique of applying noise suppression processing to a received signal when the electric field strength of the received radio wave is weak (see, for example, Patent Document 1).

JP-A-2005-6075

However, depending on the receiving environment, it is necessary to take noise countermeasures even when the electric field strength is strong, but there is a possibility that the conventional technology cannot sufficiently suppress noise.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a receiving apparatus and a receiving method capable of performing appropriate noise suppression processing in accordance with the reception environment.

In order to solve the above problems and achieve the object, a receiver according to the present invention includes a detector and a noise suppressor. The detection unit detects the noise environment of the radio wave based on the fluctuation width of the carrier frequency in the received signal of the radio wave received by the receiving antenna and the U/D level, which is the level ratio of the interference wave to the desired wave of the radio wave. do. The noise suppression unit performs noise suppression processing on the received signal according to the noise environment detected by the detection unit.

ADVANTAGE OF THE INVENTION According to this invention, the suitable noise suppression process match|combined with the receiving environment can be performed.

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

Hereinafter, a receiving device and a receiving method according to embodiments will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown 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 showing a configuration example of a receiving device 1 according to an embodiment.

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

In the receiving method according to the embodiment, a plurality of noise suppression processes are switched according to the noise environment. Specifically, in the reception method according to the embodiment, based on the variation width of the carrier frequency (frequency of the carrier wave) in the received signal and the level ratio of the desired wave and the interference wave of radio waves (hereinafter referred to as U/D level) The noise environment of radio waves is detected, and noise suppression processing is applied to the received signal according to the detected noise environment. The noise environment indicates the reception environment of noise contained in the received signal, and various examples of the noise environment will be described later.

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

A configuration example of the receiving device 1 according to the embodiment will be described below with reference to FIG. As shown in FIG. 1, the receiving device 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 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 by reading and executing programs stored in the ROM, for example. do.

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 may be implemented as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable). Gate Array) can also be configured by hardware.

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

The RF/IF section 2 extracts and amplifies a broadcast wave (desired wave) signal to be received from the 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 outputs an IF signal, which is a processed signal, to the AD conversion unit 3 .

The AD conversion section 3 converts the IF signal input from the RF/IF section 2 into a digital signal. The digitally converted IF signal is output to the detector 4 and the detector 5, respectively.

The detection unit 4 uses the IF signal input from the AD conversion unit 3 to perform detection according to a predetermined detection method. The detection unit 4 performs detection using a detection method determined based on an instruction from the noise suppression unit 6, which will be described later. Detection methods include, for example, synchronous detection and envelope detection.

In synchronous detection, a first detection signal whose phase is synchronized with the carrier frequency and a second detection signal whose phase is shifted by π/2 from the first detection signal are generated. This detection method extracts the audio signal by multiplying the received signal.

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

The detector 5 detects the noise environment of the radio waves received by the receiving antenna 20 . Specifically, the detection unit 5 detects the noise environment of radio waves based on the variation width of the carrier frequency in the received signal and the U/D level. The detector 5 outputs the detected noise environment to the noise suppressor 6 .

The noise suppression unit 6 performs noise suppression processing on the received signal according to the noise environment detected by the detection unit 5 . Here, the switching of noise suppression processing by the noise suppression unit 6 will be described with reference to FIGS. 2 to 6. FIG.

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

FIG. 2 shows a table showing the relationship between frequency fluctuation (variation range of carrier frequency) and 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 fluctuation “large” and “small” indicate whether the carrier frequency fluctuation width is greater than or equal to 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 approximately the same. A U/D level "positive value" indicates that the electric field level of the desired wave is lower than the electric field level of the interfering wave.

In other words, when the U/D level is expressed as a dB value, the U/D level “≈0” is the reference value of the U/D level, and the “negative value” is the U/D level below the reference value. and a "positive value" is a U/D level above the reference value.

As shown in FIG. 2, the detector 5 identifies the noise environment by combining "frequency fluctuation" and "U/D level".

Specifically, the detector 5 separates and detects noise environments such as a tunnel environment, a tram noise environment, and an adjacent station interference environment (weak and strong). Noise suppression processing in each noise environment will be described below with reference to FIGS. 3 to 5. FIG.

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 rebroadcasting of equipment inside the tunnel, but in this case, as shown in FIG. That is, in a tunnel environment, the frequency fluctuation is "large" and the U/D level is "negative" (see FIG. 2).

Therefore, when such a tunnel environment is detected, the noise suppression unit 6 performs processing to switch from synchronous detection to envelope detection as noise suppression processing. Specifically, when the noise suppression unit 6 detects a noise environment (tunnel environment) in which the fluctuation width of the carrier frequency is equal to or greater than a predetermined threshold value and the U/D level is less than a predetermined reference value, the detection unit 4 detection method is switched from synchronous detection to envelope detection.

As a result, noise in the audio signal can be suppressed even when the carrier frequency fluctuates. When the tunnel environment is resolved, the noise suppression unit 6 returns the detection method of the detection unit 4 from envelope detection to 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 from a streetcar or radio waves from a factory is relatively strong.

Therefore, in a tram noise environment, relatively large noise is generated 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, muting processing is performed as noise suppression processing. Specifically, when a noise environment (tram noise environment) is detected in which the fluctuation range of the carrier frequency is equal to or greater than a predetermined threshold value and the U/D level is a predetermined reference value, the noise suppression unit 6 detects that the received signal muting. When muting is performed as a default, the noise suppression unit 6 increases the amount of muting with detection of a tram noise environment as a trigger. As a result, noise derived from external noise in the audio signal can be suppressed.

Next, FIG. 5 shows the processing contents of the noise suppressor 6 in an adjacent station interference environment. The adjacent station interference environment is a noise environment in which a received signal includes a desired wave and a radio wave of a frequency adjacent to the desired wave (interference wave). FIG. 5 shows a noise environment in which the electric field level of the interfering wave is higher than the electric field level of the desired wave, that is, the U/D level is "positive".

In such an adjacent station interfering environment, the frequency fluctuation of the desired wave is small, and when the voice signal is extracted by synchronous detection by the detector 4, the interfering wave is also removed, so the final effect of noise is small. This is the same even when the U/D level is "negative".

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

The noise suppression unit 6 can further combine electric field levels to separate noise environments in which vehicle noise is generated. This point will be described with reference to FIG. FIG. 6 is an explanatory diagram for explaining noise suppression processing that takes into account the electric field level.

FIG. 6 shows an environment (weak electric field 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. In a weak electric field environment, for example, when the vehicle noise shown in FIG. 6 occurs over a wide band, there is a possibility that noise detection may be missed with normal noise detection sensitivity. Vehicle noise includes, for example, radio waves that are periodically generated in an in-vehicle system.

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

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

In this manner, the noise suppressing unit 6 performs noise suppression processing suitable for the noise environment on the received signal, and then outputs the processed signal to the output unit 7 .

Returning to FIG. 2, the output section 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 showing a processing procedure of processing executed by the receiving device 1 according to the embodiment.

As shown in FIG. 7, first, the detector 5 reads sensor values indicating the electric field level of the received signal, the variation 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 environment in which the electric field level is less than a predetermined threshold (step S102).

When the detector 5 detects a weak electric field environment (step S102, Yes), the noise suppressor 6 increases the sensitivity of the noise blanker process (step S103). On the other hand, when the detection unit 5 does not detect a weak electric field environment, that is, the environment is a strong electric field environment (step S102, No), the noise suppression unit 6 maintains the sensitivity of the noise blanker process at a normal value (step S104). .

After the process of step S103 or step S104, the detection unit 5 determines whether the noise environment is a tunnel environment (step S105). When the detector 5 detects a tunnel environment (step S105, Yes), the noise suppressor 6 switches the detection method of the detector 4 from synchronous detection to envelope detection (step S106).

On the other hand, when the tunnel environment is not detected by the detector 5 (step S105, No), the noise suppressor 6 maintains the detection method by the detector 4 as synchronous detection (step S107).

After the process of step S106 or step S107, the detection unit 5 determines whether or not the noise environment is the tram noise environment (step S108). When the detection unit 5 detects a tram noise environment (step S108, Yes), the noise suppression unit 6 increases the amount of muting as noise suppression processing (step S109), and ends the processing.

On the other hand, when the detector 5 does not detect a tram noise environment (step S108, No), the noise suppressor 6 maintains the normal mute amount as noise suppression processing (step S110), and ends the process.

As described above, the receiver 1 according to the embodiment includes the detector 5 and the noise suppressor 6 . The detection unit 5 detects the noise environment of the radio wave based on the carrier frequency variation width in the received signal of the radio wave received by the receiving 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 noise suppression processing on the received signal according to the noise environment detected by the detection unit 5 . As a result, appropriate noise suppression processing can be performed in accordance with the reception environment.

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

1 Receiving Device 2 RF/IF Section 3 AD Conversion Section 4 Detection Section 5 Detection Section 6 Noise Suppression Section 7 Output Section 20 Receiving Antenna

Claims (5)

a detection unit for detecting a noise environment of the radio wave based on a carrier frequency fluctuation range in the received signal of the radio wave received by the receiving antenna and a U/D level, which is a level ratio between the desired wave and the interfering wave of the radio wave;
a noise suppression unit that performs noise suppression processing on the received signal according to the noise environment detected by the detection unit ;
a detector that detects the received signal;
with
The noise suppressor is
switching the detection method of the detection unit from synchronous detection to envelope detection when the noise environment is detected in which the fluctuation width is equal to or greater than a predetermined threshold and the U/D level is less than a predetermined reference value.
A receiving device characterized by: a detection unit for detecting a noise environment of the radio wave based on a carrier frequency fluctuation range in the received signal of the radio wave received by the receiving antenna and a U/D level, which is a level ratio between the desired wave and the interfering wave of the radio wave;
a noise suppression unit that performs noise suppression processing on the received signal according to the noise environment detected by the detection unit;
with
The noise suppressor is
performing muting processing on the received signal when the noise environment is detected in which the fluctuation width is equal to or greater than a predetermined threshold and the U/D level is a predetermined reference value;
A receiving device characterized by: The noise suppressor is
3. The receiving apparatus according to claim 1, wherein the noise suppression processing is prohibited when the noise environment in which the fluctuation range is less than a predetermined threshold is detected. A receiving method executed by a receiving device,
a detection step of detecting a noise environment of the radio wave based on a carrier frequency fluctuation range in the received signal of the radio wave received by the receiving antenna and a U/D level that is a level ratio of the desired wave and the interfering wave of the radio wave;
a noise suppression step of subjecting the received signal to noise suppression processing according to the noise environment detected by the detection step ;
a detection step of detecting the received signal;
including
The noise suppression step includes:
Switching the detection method of the detection step from synchronous detection to envelope detection when the noise environment is detected in which the fluctuation width is equal to or greater than a predetermined threshold and the U/D level is less than a predetermined reference value.
A receiving method characterized by A receiving method executed by a receiving device,
a detection step of detecting a noise environment of the radio wave based on a carrier frequency fluctuation range in the received signal of the radio wave received by the receiving antenna and a U/D level that is a level ratio of the desired wave and the interfering wave of the radio wave;
a noise suppression step of subjecting the received signal to noise suppression processing according to the noise environment detected by the detection step;
including
The noise suppression step includes:
performing muting processing on the received signal when the noise environment is detected in which the fluctuation width is equal to or greater than a predetermined threshold and the U/D level is a predetermined reference value;
A receiving method characterized by

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