JP2001285094A - Radio receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem where overall noise elimination is difficult because a signal, processing circuit becomes complicated, even though the control of treble, bass, etc., is made according to the electric filed intensity, etc., of receiving radio wave in a conventional manner. SOLUTION: A parametric EQ selecting part 11 in a DSP 4 for radio signal processing detests a received radio wave signal, an electric field strength detecting part 12, a multi-path noise detecting part 13 and a 100 kHz adjacent noise detecting part 14 detects noise itself or data related to noise, a composite EQ curve selecting part 15 selects a preliminarily set composite EQ curve from the composite EQ curve selection table 17 of a parametric EQ selection table 16 according to an instruction of a microcomputer 20 for control, and the characteristic coefficient of an element EQ curve constituting the composite EQ curve is selected from among a selection table 19. It coefficient value is outputted to the EQ-adjusting part 9 of a DSP for audio signal processing and is subjected to prescribed equalizer processing, on the basis of the composite waveform data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for controlling electric field strength of received radio waves, multipath noise, adjacent noise, and the like.
The present invention relates to a radio receiver capable of adjusting a parametric EQ of a digital signal processor (DSP) to perform appropriate noise removal.

[0002]

2. Description of the Related Art Conventionally, in FM radio receivers and the like,
At the time of a weak electric field where the noise level is large, the low-frequency component and the high-frequency component are difficult to hear in terms of hearing. Therefore, when the input signal level is low, the gain is increased to cope with this. Conversely, when the input signal level increases, the gain is reduced to prevent the sound from being distorted. Such a function can also be performed by using an auto equalizer. In addition, when various noises increase, a stereo adjustment is made to monaural, a blend adjustment for adjusting the degree of monaural, or a channel separation adjustment is performed.
Further, a high-cut adjustment for attenuating harsh high-frequency noise may be performed. In addition, noise adjustment is performed by tone adjustment by adjusting a treble portion and a bass portion (bass) of the output audio signal, and various unpleasant noises are reduced by selecting and adjusting such various functions. .

[0003] When the radio receiver is mounted on a vehicle, the above-mentioned noise due to the electric field strength is likely to cause the received radio waves to be affected by surrounding buildings, mountains, and the like due to the movement of the vehicle. Since the noise changes every moment, the above-mentioned noise is particularly annoying. If the noise processing is not performed properly, the characteristics of the sound and the like output by the noise removal processing greatly change with the movement of the vehicle, and this must be annoying. It is necessary to perform an appropriate noise removal process.

In order to more appropriately perform the above-described noise removing function, an FM radio receiver or the like may be provided with a channel separation circuit or a high-cut circuit.
When the received electric field strength is equal to or less than the first predetermined value, the channel separation degree is weakened to make it monaural, and when the received electric field strength is equal to or lower than the second predetermined value, the high cut amount is increased as the received electric field strength becomes weak. There has also been proposed a device in which soft mute is comprehensively controlled when the received electric field intensity becomes lower than a third predetermined value. Further, a technology has been developed which converts a received audio signal into a digital signal and performs noise suppression processing when performing various signal processing by a digital signal processor (DSP).

[0005] As such a receiver, for example, a receiver as shown in FIG. 10 has been proposed. In this receiver, a radio wave such as an FM broadcast from an antenna 30 is received by a front end 31, amplified by an intermediate frequency amplifying circuit 32, detected by a detection circuit 33, and then received.
In the case of a stereo broadcast such as a stereo broadcast, a stereo demodulator 34 converts the signal into a stereo signal. On the other hand, the level meter (S-meter) 40 detects the electric field strength of the received radio wave based on the signal of the intermediate frequency amplifier circuit 32, and the separation control circuit 35 converts the signal from the stereo demodulator 34 according to the electric field strength. On the other hand, the degree of monaural is adjusted, and in the high cut circuit 36, the degree of decreasing the output level of the high frequency part of the audio signal is adjusted by the signal of the level meter 40. The signal is input to a digital signal processor (D) via an input switching circuit 37 for switching the input to another audio source.
SP) 38, and various digital signal processes are performed.

Further, from a signal of the intermediate frequency amplifying circuit 32, multi-path noise due to, for example, a reflected wave reflected in a group of high-rise buildings is detected by a noise detector 41, and a microcomputer 42 detects a multipath noise corresponding to the noise. Calculate the numerical value,
The coefficient is converted to a digital signal processor (DSP) 38
To thereby remove the noise by adjusting the frequency characteristics according to the multipath noise.

At that time, for example, as shown in FIG.
At first, for example, the signal before being processed by the digital signal processor as shown in the frequency characteristic of FIG. By obtaining an equalizer waveform for audio signal correction as shown in FIG. 1 and adding and subtracting the two signals, a signal output having characteristics as shown in FIG. At this time, the waveform for audio signal correction in FIG. 3B has a center frequency fa arbitrarily determined according to the detected noise with respect to the basic waveform Fa whose center frequency is fa and the maximum peak height (Level) is La. Go to
By setting the maximum wave height La arbitrarily, it is possible to obtain a predetermined waveform at an appropriate frequency, thereby giving a dip characteristic to the input signal as shown in the illustrated embodiment. So that it can be reduced.

[0008]

As described above, various types of noise removal in a conventional radio receiver are used. For example, as shown in FIG. 10, a separation control circuit, a high cut circuit, and the like are used. Various noise reduction circuits had to be provided. Also,
Even when the DSP is used, the waveform that can be processed by one processing portion is limited to the waveform Fa having the predetermined waveform height La of one frequency fa as described above, so that a noise adjustment of a specific portion is performed. Therefore, it was not possible to cope with various noises in a wide frequency range.

Therefore, as shown in FIG. 10 described above, even in the case where noise is removed using a DSP,
It is necessary to take countermeasures such as combining with another noise removal circuit or providing a plurality of signal processing parts in the DSP as described above, which complicates the circuit configuration and enables comprehensive noise adjustment over the entire signal waveform. There was a problem that it was difficult.

Accordingly, the present invention is capable of comprehensively removing various noises in a DSP for processing an audio signal, and can easily cope with various frequency characteristics with a simple configuration. The purpose is to provide a machine.

[0011]

According to the present invention, in order to solve the above-mentioned problems, a noise-related signal detecting section for detecting a signal related to noise and a plurality of component waveforms corresponding to the noise-related signal are synthesized. A synthesized waveform data storage unit having waveform data, a control device for obtaining data corresponding to a signal of the noise-related signal detection unit from the synthesized waveform data storage unit, a digital signal processor for digitally processing an audio signal, and the control device. A radio receiver characterized in that the frequency characteristics of an audio signal are processed by the digital signal processor using the obtained synthesized waveform data.

In another aspect, the coefficient values defining the component waveform include a center frequency, a wave height, a sharpness,
At least one of the polarities of the waves.

In another aspect, the noise-related signal detector is at least one of an electric field intensity detector, a multipath noise detector, and an adjacent noise detector.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a radio receiver according to an embodiment of the present invention, and is a functional block diagram mainly showing characteristic functional portions of the present invention. In this radio receiver as well, the AM and FM broadcast radio waves received by the antenna 1 are amplified by the intermediate frequency amplifier circuit 3 and enter the radio signal processing unit 5 of the radio signal processing DSP 4 in the same manner as in the conventional example. And various digital signal processings including the AM broadcast signal. The signal from the intermediate frequency amplifier circuit 3 enters the parametric EQ selection unit 11 and obtains a characteristic coefficient value for forming a combined EQ curve as described later.

The signal of the radio signal processing unit 5 is input to an input switching unit 6, for example, a CD player, a CD changer,
Input switching is performed with a signal from an audio source 10 other than the radio signal from devices such as a cassette tape precoder, MD player, and telephone. As a functional component of the radio receiver, a radio signal is selected by the input switching section 6, and the signal enters the various signal processing sections 8 of the audio signal processing DSP 7, where various signal processing such as compressor processing is performed. This signal enters the EQ adjusting unit 9 and the parametric EQ selecting unit 1 of the DSP 4 for radio signal processing.
The parametric EQ is adjusted based on the composite EQ curve forming characteristic coefficient value selected in step 1, signal processing is performed in response to received radio wave noise as described later, and output to the next audio signal processing unit.

The parametric EQ selector 11 includes:
Electric field intensity detector 12, multipath noise detectors 13, 1
A 00 kHz adjacent noise detection unit 14 is provided, and each receives a signal of a radio wave received from the intermediate frequency amplification circuit 3. The electric field strength detecting section (S-meter) 12 of the above detecting sections detects the intensity of the input RF signal of the received radio wave, and the signal is, for example, the output signal of the electric field strength sensor shown in FIG. As shown in the graph, when the electric field is strong, the output is large, and when the electric field is weak, the output is small, and the output characteristics can be arbitrarily set.

In the multipath noise detector 13,
An AC component superimposed on a signal line is detected, and the strength of multipath noise due to a reflected wave from a surrounding building or the like, that is, the strength of multipath noise is detected. In this case, for example, a filter having a filter characteristic for multipath noise detection as shown in FIG. 2B can be used. In the filter shown here, 20k
With respect to the center frequency of HZ, noise within a range of about ± 10 kHz is detected.

The 100 kHz adjacent noise detection unit 14 detects a frequency around 100 kHz on the multiplex signal line as an FM composite signal, and for example, uses a filter having a filter characteristic of 100 kHz adjacent noise detection shown in FIG. The noise is detected within a range of ± 50 kHz around 100 kHz.

The noise signal detected by each detection unit as described above in the parametric EQ selection unit 11 of FIG.
The data is input to the composite EQ curve selection unit 15 and serves as basic data for selecting a composite EQ curve as described later. The combined EQ curve selection unit 15 fetches data of a parametric EQ selection table 16 to be described later according to an instruction from the control microcomputer 20, and finally obtains a combined EQ curve forming characteristic coefficient value. The data is output to the EQ adjustment unit 9 of the processing DSP 7. The output of this coefficient value can also be output from the control microcomputer 20.

The EQ adjusting section 9 basically forms an equalizing curve as shown in FIG. 3, for example, based on the characteristic coefficient value for forming the composite EQ curve, and performs processing corresponding to this characteristic. That is, FIG. 6 shows an example of adjustment of the equalizing curve which is simplified so that its function can be easily understood. The equalizing curve when the electric field intensity is weak and the multipath value is large is shown in FIG. Adjustments are made so that the output is low in both the low frequency region and the high frequency region. In particular, the output is suppressed more in the high frequency region, and the same processing as the conventional high cut processing is performed to suppress the output of harsh sound. On the other hand, when the electric field strength is strong and the multipath value is small, the output of the low frequency region and the high frequency region is increased, as shown in FIG. I have.

The above example illustrates noise and parametric EQ.
Is shown in a simplified manner, but actually, the output audio characteristics are adjusted in consideration of various factors. For example, as shown in the FM input / output characteristic diagram of FIG.
Indicates the characteristics of the electric field strength sensor, solid line B indicates an audio signal level whose output increases as the electric field of the radio wave received from the state of inter-station noise increases,
As shown in the figure, the maximum value is suppressed to a predetermined value by soft mute control by adjacent noise, setting of inter-station noise, and the like. Further, the solid line C indicates a noise signal whose output decreases as the electric field of the received radio wave increases, in contrast to the solid line B.

The dashed line D in the figure is a blend ratio between stereo and monaural, and is adjusted by multipath noise and by adjacent noise as shown in the figure. The maximum separation is also set. Two point difference line E in the figure
Indicates a high-cut characteristic, which is also adjusted by multipath noise and by adjacent noise as described above.

As described above, in the audio device, it is necessary to comprehensively control the characteristics according to various factors. As described above, in the conventional device, such a large number of parameters are comprehensively controlled. It could not be adjusted. On the other hand, the present invention can be easily adjusted using a plurality of parametric EQ correction waveforms as shown in FIG. 5, for example.

That is, an example is shown in which n waveforms whose center frequencies are from f1 to fn are used along the frequency f on the horizontal axis in the figure. For example, as shown in the waveform F1 of the center frequency f1, the center frequency is used. f1 itself is variable, the height of the waveform, that is, the level L1, is variable, and the sharpness Q of the waveform is
1 is also variable. Thereby, as will be described later in detail, a predetermined combined EQ curve can be obtained by arbitrarily setting these variable values. Such a variable amount can be represented as a coefficient for deforming the reference waveform. Therefore, arbitrary waveform data can be obtained by merely indicating the coefficient, and the load on signal processing can be reduced.

In the present invention, arbitrary n waveforms as shown in FIG. 5 can be used, and in the simplest form, two waveforms can be used in combination, and more waveforms are required to form a more complicated waveform. Are used in combination. When using the waveform, for example, the polarity of the waveform data can be set to a minus value as shown by a broken line waveform in the waveform of the center frequency f2. By using data of negative polarity in this way,
More EQ curves can be easily formed.

When a parametric EQ curve is formed by combining the above-described waveforms, the curves are combined, for example, as shown in FIG. That is, by using four basic waveforms whose center frequencies are f1 to f4 as shown in FIG. 2B and arbitrarily setting the above-described coefficient values for each waveform, FIG. A composite EQ curve (E
Q) Modified element EQ curves F1-F for forming
Get 4. By combining the element EQ curves F1 to F4 by a known method, a combined EQ curve (EQ) as shown by a thick solid line in the figure is obtained. According to the composite EQ curve, the characteristic of increasing the output in the low frequency region and increasing the output in the high frequency region is similar to the characteristic in the state where the electric field strength is large.

Similarly, as shown in FIG. 7 (b), using the same basic waveform as described above, the coefficient of each waveform is arbitrarily set to form an element EQ curve obtained by modifying the basic waveform of F1 to F4. A composite EQ curve (EQ) by combining them
Can be obtained. In the illustrated embodiment, the waveforms of the element EQ curves F1 and F4 are used in the state shown by the broken line in the figure in which the polarity of the basic waveform shown in FIG. In this way, by inverting the polarity of the basic waveform, it is possible to obtain more various combined EQ curves.

In the formation of the modified element EQ curve by setting the basic waveform and the coefficient for the basic waveform as described above, and the formation of the composite EQ curve obtained by synthesizing the same, for example, the means shown in FIGS. Parametric EQ selection table 1 of FIG. 1 using various tables shown in FIG.
6 can be easily implemented.
In the illustrated example, as shown in FIG. 8A, an example is shown in which five basic waveforms having center frequencies f1 to f5 are used.

The parametric EQ selection table 1 of FIG.
As the combined EQ curve selection table 17 in FIG. 6, for example, the one shown in FIG. 9A is used. In this example, the electric field intensity detection signal having the characteristic shown in FIG. 2A obtained by the electric field intensity detection unit 12 in FIG.
The magnitude of the multipath noise obtained by the multipath noise detector 13 of FIG. 1 using the filter shown in FIG.
The magnitude obtained by the 100 kHz adjacent noise detection unit 14 in FIG. 1 using the filter shown in FIG.
The table is divided into three stages of small and four types including neglect, and a table is created as shown in the figure, which shows the mode that occurs when the device is normally used.

As described above, the most appropriate setting of the parametric EQ can be obtained in advance by calculation in accordance with each of the modes that occur when the apparatus is normally used. Parametric E
The characteristic curve of Q was obtained by calculating the element EQ curve by variously modifying the five basic waveforms as shown in FIG. In the embodiment shown in FIG. 8 which approximates the characteristic curves, six characteristic curves as shown in FIGS. 8B to 8G are obtained. In this way, as shown in FIG. 9A, seven types of combined EQ curves for selection of EQ1 to EQ7 are associated with each mode. In the example shown in FIG. 9A, EQ5 and EQ6 have the same noise condition,
As shown in (f), both have the same combined EQ curve.

As described above, the combined EQ curve selected in accordance with each mode is predetermined, and what kind of element EQ curve each combined EQ curve combines is shown in FIG. This is made clear by the element EQ curve selection table shown in FIG. This table is a table for facilitating selection of a coefficient value in a characteristic coefficient selection table of an element EQ curve described below. This table is shown as an element EQ curve selection table 18 in FIG. In this table, for example, it is shown that the composite EQ curve EQ1 is composed of the element EQ curves of F1-1 to F5-1 which are modified from the basic waveforms of F1 to F5, and similarly, the composite EQ curve EQ2 Indicates that it is composed of element EQ curves of F1-2 to F5-2. Similarly, it is shown that the combined EQ curves EQ3 to EQ7 are also composed of the illustrated element EQ curves, and in each of the modes shown in FIG.
It can be seen that the composite waveform shown in (g) is a composite of the elemental EQ curve shown in FIG. 9 (b), which is a modification of the basic waveform of FIG. 8 (a).

Such an element EQ curve is modified from the basic waveform by the coefficient values shown in the characteristic coefficient selection table of the element EQ curve as shown in FIG. Therefore, for each of the element EQ curves, the above-described coefficient values constituting the waveform can be obtained from this table. This table is shown as the characteristic coefficient selection table 19 of the element EQ curve in FIG. Regarding F1-1 which is the first element EQ curve of the combined EQ curve EQ1 shown in FIG. 9B, the center frequency f is f1-1, the sharpness Q is Q1-1, and the level L
Is L1-1, and the direction of the waveform, that is, the waveform polarity is on the + side, that is, the erect side, can be obtained from this table. Similarly, the first element E of the composite EQ curve EQ2
For F1-2 which is a Q curve, the center frequency f is f
1-2, the sharpness Q is Q1-2, the level L is L1-2, and the polarity of the waveform is required to be on the + side, that is, on the erect side.

As described above, the synthesized waveform having a predetermined frequency characteristic for adjusting the parametric EQ has the characteristic coefficients of the element EQ curves constituting the synthesized EQ curve as described above as shown in the table of FIG. , It is possible to cope with various noise states.
Therefore, when storing a curve of a predetermined frequency characteristic for removing noise, it is not necessary to directly store the curve data, and only the coefficient value for deforming the basic waveform is stored. Can be stored. Also, the burden of accessing this memory and outputting this data to the audio signal processing DSP can be reduced.

By using the table as described above, a composite EQ curve is selected from FIG. 9A based on the detection values of the respective detectors 12 to 14 in the parametric EQ selector 11 shown in FIG. (B) from its synthesis E
A plurality of element EQ curves constituting the Q curve are obtained,
From FIG. 9C, the respective element EQ curve coefficient values, that is, the characteristic coefficient values for forming the combined EQ curve shown in FIG. 1 are obtained. The composite EQ curve selector 15 in FIG. 1 outputs this coefficient value to the EQ adjuster 9 of the audio signal processing DSP 7 and, based on the coefficient, generates a composite EQ as shown in FIGS.
After obtaining the Q curve, the audio signal subjected to various signal processings by the various signal processing units 8 is corrected by parametric EQ. Further, another digital signal processing or the like can be performed on the output signal.

The control microcomputer 20 shown in FIG.
DSP4 for radio signal processing, DS for audio signal processing
Outputs control signals for various signal processing used in P7,
Further, it is possible to access the parametric EQ selection table 16. Further, data from a vehicle speed detection unit 22 that takes in a signal from the traveling meter system of the vehicle 21, a noise detection unit 23 that detects the state of the noise in the vehicle from a microphone 24 provided in the room, and data from the navigation device 25 and the like can also be taken in. The display can be appropriately displayed on the display device 26.

In the above embodiment, the description has been given of an example of an on-vehicle radio receiver which is susceptible to the electric field strength which changes every moment. However, the present invention can be applied to other ordinary fixed radio receivers. Of course, the present invention can also be applied to a portable radio receiver. Also, DSP
DSP for audio signal processing and DS for radio signal processing
Although an example in which P is provided separately is shown, this can be combined as one DSP.
P can be processed without using such a DSP.

Furthermore, an example has been shown in which the combined EQ curve forming characteristic coefficient value is output from the combined EQ curve selection unit 15.
This can be set to be output from the control microcomputer 20. Also, an example has been described in which the access to the parametric EQ selection table 16 is performed from the composite EQ curve selection unit 15, but all of these accesses can be performed via the control microcomputer 20, and the present invention is not limited to this. In addition to the embodiment, the configuration can be appropriately changed and implemented as needed.

[0038]

Since the present invention is constructed as described above, various noises can be totally removed in the DSP for processing the audio signal, and an arbitrary composite waveform can be formed by selecting a plurality of component waveforms. By doing so, it is possible to easily cope with various frequency characteristics with a simple configuration.

Further, the coefficient value defining the element waveform is
For at least one of the center frequency, wave height, sharpness, and wave polarity, by arbitrarily selecting any of these coefficients, a composite waveform conforming to a desired frequency characteristic is obtained. It can be easily formed.

The noise-related signal detector may be at least one of an electric field intensity detector, a multipath noise detector, and an adjacent noise detector, and may be obtained by any of these detectors. Using a signal related to the noise, it is possible to easily form a composite waveform suitable for frequency characteristics for removing the noise with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of an embodiment of the present invention.

FIG. 2 is a graph showing characteristics of various detection units used in the present invention.

FIG. 3 is a diagram showing a basic mode of adjusting an equalizing curve according to the present invention.

FIG. 4 is an FM input / output characteristic diagram showing a relation between electric field intensity and noise adjustment;

FIG. 5 is an explanatory diagram of a basic waveform for parametric EQ correction according to the present invention.

FIG. 6 is a diagram showing an example of a composite waveform forming a composite EQ curve according to the present invention.

FIG. 7 is a diagram showing another example of a combined waveform forming a combined EQ curve according to the present invention.

FIG. 8 is a diagram showing an example of a combined EQ curve for parametric EQ adjustment according to the present invention.

FIG. 9 is a diagram illustrating an example of a selection of a composite EQ curve and a characteristic coefficient selection table of an element EQ curve according to the present invention.

FIG. 10 is a functional block diagram of a conventional radio receiver.

FIG. 11 is a diagram showing processing by an audio signal correction waveform in a conventional DSP.

[Explanation of symbols]

 Reference Signs List 4 DSP for radio signal processing 6 Input switching unit 7 DSP for audio signal processing 9 EQ adjustment unit 11 Parametric EQ selection unit 12 Electric field strength detection unit 13 Multipath noise detection unit 14 100 kHz adjacent noise detection unit 15 Combined EQ curve selection unit 16 Parametric EQ selection table 17 Composite EQ curve selection table 18 Element EQ curve selection table 19 Element EQ curve characteristic coefficient selection table 20 Control microcomputer

Claims (3)

[Claims] 1. A noise-related signal detection unit for detecting a signal related to noise, a composite waveform data storage unit including waveform data obtained by synthesizing a plurality of component waveforms corresponding to the noise-related signal, and the composite waveform data A control device for obtaining data corresponding to the signal of the noise-related signal detection unit from the storage unit,
A radio receiver, wherein a digital signal processor for digitally processing an audio signal and a frequency characteristic of the audio signal are processed by the digital signal processor based on synthesized waveform data obtained by the control device. 2. The radio reception according to claim 1, wherein the coefficient value defining the element waveform is at least one of a center frequency, a wave height, a sharpness, and a wave polarity. Machine. 3. The radio according to claim 1, wherein the noise-related signal detection unit is at least one of an electric field strength detection unit, a multipath noise detection unit, and an adjacent noise detection unit. Receiving machine.