JP5006084B2 - Receiving apparatus and receiving method - Google Patents

Description

  The present invention relates to a receiving apparatus and a receiving method for receiving a broadcast wave, and more particularly to a technique for adjusting a tuning characteristic of a tuning circuit.

Conventionally, a receiving device including a tuning circuit in an RF stage is known. In this type of receiving apparatus, in order to receive weak radio waves satisfactorily, the tuning circuit is set so that the receiving sensitivity of the tuning circuit is maximized in a predetermined receiving frequency band, that is, the received electric field intensity is maximized. (For example, refer to Patent Document 1).
Japanese Patent No. 3486443

However, when various interference signals such as adjacent interference, intermodulation interference, and strong input interference signals are generated and the original signal is suppressed to noise, so-called signal suppression occurs, The received signal quality is not always optimal.
The present invention has been made in view of the above-described circumstances, and provides a receiving apparatus and a receiving method capable of maintaining the received signal quality satisfactorily even when signal suppression is caused by an interference signal. Objective.

In order to achieve the above object, the present invention provides a receiving apparatus comprising a tuning circuit, a tuner circuit connected to the tuning circuit, and a demodulation circuit that demodulates a signal output from the tuner circuit. A control unit that controls the tuning characteristics of the receiver , the control unit is received with a predetermined tuning characteristic corresponding to the reception frequency band, and when the degradation of the received signal quality due to the high frequency noise included in the demodulated signal is detected, Alternatively, when the reception frequency band or the reception frequency is changed after reception with the predetermined tuning characteristic, the tuning frequency is changed by a predetermined step, and the received electric field strength of the received signal is received with the predetermined tuning characteristic. The frequency is set to a frequency that is larger than the time and lower than that when the high-frequency noise is received with the predetermined tuning characteristic .

The present invention, in the receiver, the control unit, during receiving operation, characterized in that you intermittently detect deterioration of the received signal quality due to the high frequency noise.

In order to achieve the above object, the present invention provides a receiving method of a receiving apparatus including a tuning circuit, a tuner circuit connected to the tuning circuit, and a demodulation circuit that demodulates a signal output from the tuner circuit. When reception is performed with a predetermined tuning characteristic corresponding to the reception frequency band and deterioration of the received signal quality due to high frequency noise included in the demodulated signal is detected, or after reception with the predetermined tuning characteristic, When the reception frequency is changed, the tuning frequency is changed by a predetermined step so that the received electric field strength of the received signal becomes larger than that when the signal is received with the predetermined tuning characteristic, and the high frequency noise is the predetermined frequency. Set to a frequency that is lower than when receiving with tuning characteristics.

According to the present invention, the received electric field strength and the amount of noise included in the demodulated signal are detected while changing the tuning characteristics of the tuning circuit by predetermined steps, and the received electric field strength increases and the noise decreases. A tuning characteristic is identified and this tuning characteristic is set in the tuning circuit. Thereby, even if signal suppression is generated by various interference signals, both the reception sensitivity and the reception signal quality can be maintained well.
Even if the tuning characteristics are set incorrectly for some reason, or even if the tuning characteristics setting optimum value changes due to changes in the tuning characteristics over time, the reception sensitivity and the received signal quality are similarly set. Both can be maintained well.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to an in-vehicle broadcast receiving device mounted on a vehicle is illustrated.
FIG. 1 is a block diagram illustrating a configuration of an in-vehicle broadcast receiving apparatus 1 according to the present embodiment.
In this figure, the tuning circuit 3 is provided in the RF stage of the in-vehicle broadcast receiving apparatus 1, and via an antenna (ANT) 2, for example, radio waves in a predetermined frequency band used by broadcasts such as AM broadcasts and FM broadcasts. Tuning is performed, and a high-frequency signal in the predetermined frequency band is output to the tuner circuit 4.
The tuning circuit 3 includes a resonance circuit including a coil and a variable capacitance element (so-called varicap), and the resonance frequency of the resonance circuit is varied by varying the capacitance of the variable capacitance element, thereby tuning. The tuning frequency of the circuit 3 is varied.

  The tuner circuit 4 extracts a signal corresponding to the reception frequency from the high-frequency signal output from the tuning circuit 3 and outputs the signal to the detection circuit 13 described later. The tuner circuit 4 includes a high-frequency amplifier (RF-Amp) 5 and a frequency conversion circuit. 6, a first intermediate frequency transformer (IFT) 7, an intermediate frequency amplifier (IF-Amp) 8, and a D / A converter 9.

The high frequency amplifier 5 amplifies the high frequency signal output from the tuning circuit 3 and outputs the amplified signal to the frequency conversion circuit 6.
The frequency conversion circuit 6 mixes a local oscillation circuit (OSC) 10 that outputs a frequency instructed by the control unit 20 described later, a signal output from the local oscillation circuit 10 and a high-frequency signal output from the high-frequency amplifier 5. A mixer (MIX) 11 that outputs an intermediate frequency (IF) signal having a constant intermediate frequency to the first intermediate frequency transformer 7 is provided.

The first intermediate frequency transformer 7 functions as a filter that extracts the signal of the intermediate frequency component from the intermediate frequency signal output from the frequency conversion circuit 6, and outputs the extracted intermediate frequency signal to the intermediate frequency amplification circuit 8.
The intermediate frequency amplifier circuit 8 has a gain controlled by an AGC circuit (not shown), amplifies the intermediate frequency signal output from the first intermediate frequency transformer 7 to a predetermined level that can be demodulated, and a second intermediate frequency transformer (IFT). 12 is output.
The D / A converter 9 converts a digital tuning characteristic control signal Cd output from the control unit 20 described later into an analog signal and outputs the analog signal to the tuning circuit 3. The analog signal has a DC tuning voltage corresponding to the tuning characteristic control signal Cd, and the tuning circuit 3 varies the tuning frequency according to the tuning voltage, thereby controlling the tuning characteristic of the tuning circuit 3. Is called.

The second intermediate frequency transformer 12 functions as a filter in the same manner as the first intermediate frequency transformer 7, extracts an intermediate frequency signal of an intermediate frequency component from the intermediate frequency signal output from the intermediate frequency amplifier circuit 8, and detects a detection circuit (DET). ) Is output to 13.
The detection circuit 13 detects and demodulates an audio signal, which is a modulation signal, from the intermediate frequency signal output from the second intermediate frequency transformer 12, and outputs it to the stereo separation circuit (MPX) 14. Further, the intensity of the output signal of the detection circuit 13 is input to an AGC circuit (not shown), and the gain of the intermediate frequency amplifier circuit 8 is feedback-controlled by the AGC circuit so that the output of the detection circuit 13 has a constant intensity. Yes.

The stereo separation circuit 14 separates the audio signal output from the detection circuit 13 into, for example, left and right channel stereo audio signals, and outputs the stereo audio signal to the low-frequency amplifier circuit (Audio-Amp) 15 for each channel.
The low frequency amplifier circuit 15 is provided corresponding to the number of channels of the stereo audio signal, and each amplifies the power of the stereo audio signal and outputs it to the speaker 16 provided in the vehicle for each channel. To output sound.

The control unit 20 centrally controls each unit of the in-vehicle broadcast receiving device 1 and includes, for example, a microcomputer that includes a program execution circuit and a memory 21 that stores data.
The control unit 20 also includes an S (signal) meter signal Sm indicating the received electric field strength of the received signal at the current reception frequency, and high frequency band noise (hereinafter referred to as “high frequency band” included in the demodulated signal). A noise signal Ns indicating the amount of noise) is input from the detection circuit 13.

And the control part 20 controls the tuning characteristic of the tuning circuit 3 based on these S meter signal Sm and the noise signal Ns at the time of reception of a broadcast wave, and maintains the received signal quality favorably.
When the tuning characteristic of the tuning circuit 3 is controlled, the control unit 20 outputs the digital tuning characteristic control signal Cd described above. The tuning characteristic control signal Cd defines a tuning voltage by its digital value, and a value corresponding to the number of variable steps of the tuning frequency of the tuning circuit 3 is assigned.

FIG. 2 is a flowchart of the tuning characteristic control process.
When the broadcast reception apparatus 1 is turned on and starts receiving broadcasts, the control unit 20 sets the tuning characteristic of the tuning circuit 3 to a preset default value ( Step S1). This default value is set so that the sensitivity is maximized with respect to the received frequency band.
Next, the control unit 20 detects whether or not the reception band (reception frequency band) such as FM broadcast to AM broadcast has been changed, or whether or not the reception frequency has been changed by changing the broadcast channel (step S2). ) If either the reception band or the reception frequency has been changed (step S2: Yes), the tuning characteristic optimum to be described later is set to be the optimum tuning characteristic for the reception frequency band or the reception frequency. (Step S3).
If neither the reception band nor the reception frequency is changed (step S2: No), the noise signal Ns is monitored to detect deterioration of the received signal quality currently received, and is included in the demodulated signal. It is determined whether or not the high frequency noise that is present has become equal to or greater than the noise threshold Nth (step S4). This noise threshold value Nth is a threshold value indicating whether or not the received signal quality is good based on the amount of noise.

Therefore, when the high frequency noise is less than the noise threshold value Nth (step S2: No), the control unit 20 returns the processing procedure to step S2 to indicate that the received signal quality is well maintained.
On the other hand, when the high frequency noise is equal to or higher than the noise threshold Nth (step S2: Yes), when the high frequency noise exceeds the noise threshold Nth, various interferences such as adjacent interference, intermodulation interference, and strong input interference signal are used. The signal indicates that the original received signal is disturbed by the signal and the received signal quality is degraded. Therefore, the control unit 20 performs tuning characteristic optimization processing to be described later (step S3), and optimizes the tuning characteristics so that the received signal quality is good.

  As described above, in this embodiment, when the reception frequency band or the reception frequency is changed while receiving a broadcast, the tuning characteristic is optimized to optimize the tuning characteristic so that the reception signal quality is improved. Processing is performed. In addition, the reception signal quality deterioration is monitored by detecting the amount of high-frequency noise included in the demodulated signal, and the tuning characteristic optimization process is also performed when the reception signal quality deterioration is detected. .

  In the tuning characteristic optimization process in step S3, the tuning frequency defining the tuning characteristic of the tuning circuit 3 is changed for each predetermined step, and the received electric field strength of the received signal becomes larger than the current value (that is, the receiving sensitivity is improved). In addition, the high frequency noise included in the demodulated signal is set to a frequency that is lower than the current value, and details of the processing are shown in FIG.

  In the tuning characteristic optimization process, the control unit 20 firstly, the control value (digital control value) of the tuning characteristic control signal Cd indicating the current tuning frequency, the voltage value of the S meter signal Sm indicating the received electric field strength, and The voltage value of the noise signal Ns indicating the amount of high frequency noise is stored in the memory 21 as an initial value (step S10).

Next, the control unit 20 sequentially increases the tuning frequency for each predetermined step, measures the received electric field strength and high-frequency noise at each tuning frequency, and the tuning frequency at which the received signal quality is better than the present around the current tuning frequency. Explore.
First, the control unit 20 searches for a frequency range higher than the current tuning frequency. Therefore, the control unit 20 increases the control value of the tuning characteristic control signal Cd by “one step” in order to increase the tuning frequency by one step (step S11). Then, the control unit 20 inputs the tuning characteristic control signal Cd to the tuning circuit 3 via the D / A converter 9, and calculates the voltage value of the S meter signal Sm and the voltage value of the noise signal Ns at that time. Compared with the value before the control value of the tuning characteristic control signal Cd increases by “one step”, it is determined whether or not the voltage value of the S meter signal Sm has decreased or the high frequency noise has increased (step S12). ).
If the voltage value of the S meter signal Sm is not decreased or the high frequency noise is not increased (step S12: No), the reception signal quality can be improved by further increasing the control value of the tuning characteristic control signal Cd. Therefore, the control unit 20 returns the processing procedure to step S11.

  On the other hand, when the voltage value of the S meter signal Sm decreases or the high frequency noise increases (step S12: Yes), the reception setting before the deterioration is set to indicate that the reception signal quality has deteriorated. In order to return, the control unit 20 decreases the control value of the tuning characteristic control signal Cd by “one step” (step S13), the control value of the tuning characteristic control signal Cd at that time, the voltage value of the S meter signal Sm, and Then, the voltage value of the noise signal Ns is stored in the memory 21 as a first candidate for reception setting that makes the received signal quality better than the present one (step S14).

Next, the control unit 20 returns the control value of the tuning characteristic control signal Cd to the initial value stored in step S10 and outputs it to the tuning circuit 3 (step S15). This time, a frequency range lower than the current tuning frequency is set. Explore. Therefore, the control unit 20 decreases the control value of the tuning characteristic control signal Cd by “one step” in order to decrease the tuning frequency by one step (step S16). Then, the control unit 20 inputs the tuning characteristic control signal Cd to the tuning circuit 3 via the D / A converter 9, and calculates the voltage value of the S meter signal Sm and the voltage value of the noise signal Ns at that time. It is determined whether or not the voltage value of the S meter signal Sm is decreased or the high frequency noise is increased as compared with the value before the control value of the tuning characteristic control signal Cd is decreased by “one step” (step S17). ).
If the voltage value of the S meter signal Sm is not decreased or the high frequency noise is not increased (step S17: No), the received signal quality can be improved by further reducing the control value of the tuning characteristic control signal Cd. Therefore, the control unit 20 returns the processing procedure to step S16.

  On the other hand, when the voltage value of the S meter signal Sm decreases or the high frequency noise increases (step S17: Yes), the reception setting before the deterioration is set to indicate that the reception signal quality has deteriorated. In order to return, the control unit 20 increases the control value of the tuning characteristic control signal Cd by “1 step” (step S18), the control value of the tuning characteristic control signal Cd at that time, the voltage value of the S meter signal Sm, and Then, the voltage value of the noise signal Ns is stored in the memory 21 as a second candidate for reception setting that makes the received signal quality better than the current value (step S19).

Next, the control unit 20 specifies a control value having a higher voltage value of the S meter signal Sm and a smaller voltage value of the noise signal Ns among the first candidate and the second candidate, and determines the control value. The tuning characteristic control signal Cd is set and output to the tuning circuit 3 (step S20).
As a result, the tuning circuit 3 can be matched with the tuning characteristics in which the reception sensitivity is maintained well, the high frequency noise is small, and the signal suppression is suppressed.

  As described above, according to the present embodiment, the received electric field intensity and the amount of noise included in the demodulated signal are detected while changing the tuning frequency, which is the tuning characteristic of the tuning circuit 3, by predetermined steps. Since the tuning characteristic having high strength and low noise is specified and this tuning characteristic is set in the tuning circuit 3, even if signal suppression is caused by various interference signals, the reception sensitivity and Both the received signal quality can be maintained well.

  Further, according to the present embodiment, the noise level is intermittently detected during the reception operation, and when the noise level exceeds a predetermined threshold, the received electric field strength is high as described above, and Since the tuning characteristic with less noise is specified and the tuning characteristic is set in the tuning circuit 3, the tuning characteristic can be quickly adjusted according to the reception situation. For example, in a place where the reception condition of the radio wave is bad Even when the vehicle moves, it is possible to quickly adjust the tuning characteristics so that both the reception sensitivity and the reception signal quality are good.

  Further, according to the present embodiment, every time the reception frequency or the reception frequency band (reception band) is changed, the tuning characteristics are adjusted to improve both the reception sensitivity and the reception signal quality. Without being limited to the set value of the set tuning characteristic, it is possible to always maintain good reception sensitivity and reception signal quality.

The above-described embodiment is merely an aspect of the present invention, and can be arbitrarily modified and applied within the scope of the present invention.
For example, in the above-described embodiment, a station detector signal (so-called SD signal) may be used instead of the S meter signal Sm as a signal indicating the received electric field strength.

It is a block diagram which shows the structure of the vehicle-mounted broadcast receiver which concerns on embodiment of this invention. It is a flowchart of a tuning characteristic control process. It is a flowchart of a tuning characteristic optimization process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 In-vehicle broadcast receiver 3 Tuning circuit 4 Tuner circuit 9 D / A converter 13 Detection circuit (demodulation circuit)
20 control unit 21 memory Cd tuning characteristic control signal Sm S meter signal Ns noise signal

Claims (3)

In a receiving device including a tuning circuit, a tuner circuit connected to the tuning circuit, and a demodulation circuit that demodulates a signal output from the tuner circuit,
A control unit for controlling the tuning characteristics of the tuning circuit;
The controller is
When reception is performed with a predetermined tuning characteristic corresponding to the reception frequency band and deterioration of the received signal quality due to high frequency noise included in the demodulated signal is detected, or after reception with the predetermined tuning characteristic, When the reception frequency is changed, the tuning frequency is changed by a predetermined step so that the received electric field strength of the received signal becomes larger than that when the signal is received with the predetermined tuning characteristic, and the high frequency noise is the predetermined frequency. A receiving apparatus, wherein the frequency is set to be lower than that when receiving with tuning characteristics . The receiving device according to claim 1,
Wherein, during the receiving operation, the receiving apparatus characterized by you intermittently detect deterioration of the received signal quality due to the high frequency noise. In a receiving method of a receiving apparatus, comprising: a tuning circuit; a tuner circuit connected to the tuning circuit; and a demodulation circuit that demodulates a signal output from the tuner circuit.
When reception is performed with a predetermined tuning characteristic corresponding to the reception frequency band and deterioration of the received signal quality due to high frequency noise included in the demodulated signal is detected, or after reception with the predetermined tuning characteristic, When the reception frequency is changed, the tuning frequency is changed by a predetermined step so that the received electric field strength of the received signal becomes larger than that when the signal is received with the predetermined tuning characteristic, and the high frequency noise is the predetermined frequency. A receiving method, wherein the frequency is set to be lower than that when receiving with tuning characteristics .

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