JPH10256925A - Acoustic apparatus with radio reception function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent the occurrence of beat with a simple constitution. SOLUTION: This apparatus has a tuner 1 and acoustic units 4 and 5 which are controlled with a system control microcomputer 2 by communication control. The system control microcomputer 2 performs communication control of the tuner 1 by an operation input 14, and a frequency fa of a clock signal between the system control microcomputer 2 and acoustic units 4 and 5 is changed to a frequency fa' to prevent the occurrnece of beat if beat occurs by the frequency nfa of a higher harmonic of this clock signal and a reception frequency f0 of radio broadcasting during reception of radio broadcasting through the tuner 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiver for a compact disk (CD) device and a mini disk (MD).
The present invention relates to an audio device with a radio reception function that is attached to an audio device such as a device or a tape recorder and controls these devices by controlling communication with a built-in system control microcomputer.

[0002]

2. Description of the Related Art For example, a mini-disc (MD) recorder with a radio reception function as an audio device with a radio reception function is an electronic tunable tuner that is a radio reception function section, a system control microcomputer, a tape mechanism control unit, and an MD control. In response to key operations, the system control microcomputer communicates with the electronic tunable tuner to control the reception of AM and FM radio broadcasts, and communicates with the tape mechanism control unit. To control the operation of the tape recorder and communicate with the MD control unit to
In some cases, the operation of the D recorder is controlled.

In such communication control, a system control microcomputer always outputs various basic clock signals to a tape mechanical control unit or an MD control unit even while receiving a radio broadcast by an electronic tuning tuner. doing.

[0004]

The basic frequency of a clock signal for communication control is represented by fa, as shown in FIG. 6, which is a frequency characteristic in which the vertical axis represents the level and the horizontal axis represents the frequency. , A harmonic nfa (n = 1, 2,...) With respect to the fundamental frequency fa
For example, when the system control microcomputer controls communication of the electronic tunable tuner and receives AM radio broadcast from an AM radio broadcast station, and the carrier wave frequency from the broadcast station is f0, The harmonic nf
For example, 8fa of a and the carrier wave f0 generate a beat, and in an audible frequency band having a beat frequency of about 15 kHz or less, an unpleasant sound such as a beep is heard by an operator or the like.

[0005] When the system control microcomputer controls the electronic tuning tuner to receive FM radio broadcasting, the A / D of the MD control unit is controlled.
Assuming that the fundamental frequency of the system clock signal of the D converter and the D / A converter is fm and the carrier frequency of the FM radio signal from the FM radio broadcasting station is f0, as shown in FIG. Among them, for example, 7fm and the carrier wave f0 cause a beat, and in an audible frequency band having a beat frequency of about 15 kHz or less, there is a problem that an operator or the like may hear an unpleasant sound such as a beep.

On the other hand, a system control microcomputer and an M
To attach a capacitor to the clock line for communication with the D control unit and dull the waveform of the clock signal to suppress the generation of harmonics, or to electromagnetically shield the circuit board containing the clock line, There are means such as inserting a filter that suppresses the generation of high frequency. However, such a means has a considerably complicated configuration, and it requires a considerable cost to reliably prevent beat generation. There is a problem that it is not always a fundamental solution.

[0007]

According to a first aspect of the present invention, there is provided a tuner and an audio unit which are communicatively controlled by a system control microcomputer, wherein the system control microcomputer communicatively controls the tuner in response to an operation input. If a harmonic of the frequency of the clock signal between the system control microcomputer and the sound unit and the reception frequency of the radio broadcast cause a beat during reception of the radio broadcast via the tuner, the frequency of the clock signal is changed. The above-mentioned problem has been solved as an acoustic device with a radio reception function characterized by the above.

According to a second aspect of the present invention, there is provided a tuner and an audio unit which are communicatively controlled by a system control microcomputer, and the audio unit includes a converter unit including a D / A converter and an A / D converter. The system control microcomputer controls the communication of the tuner by operation input, and while receiving a radio broadcast via the tuner, the harmonics of the fundamental frequency of the system clock signal of both converters and the reception frequency of the radio broadcast beat. The above-mentioned problem is solved as an acoustic device with a radio receiving function, characterized in that the fundamental frequency is changed in the case of causing the above.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an audio equipment having a radio receiving function according to the present invention. The audio equipment of the present invention is, for example, two audio units, a tape mechanical control unit and an MD control unit, but the present invention is not limited to these two audio units. It should be noted that the unit in the present embodiment is merely a name, and should not be construed as being limited to a device installed in any case, but rather should be interpreted as a broad concept such as means.

Embodiment 1 FIG. 1 is a circuit block diagram of an audio apparatus with a radio reception function according to Embodiment 1 of the present invention. Referring to FIG. 1, reference numeral 1 denotes a tuner as a radio reception function unit, for example, an electronic tuning type tuner;
2 is a system control microcomputer for controlling the entire system, 3 is a display device for displaying various contents in this control, and 4 is a device for controlling a tape recorder mechanism such as recording or playback in accordance with communication control from the system control microcomputer 2. A tape mechanical control unit, 5 is an MD control unit for controlling an MD mechanism such as recording and playback according to communication control from the system control microcomputer 2, 6 is an electronic tunable tuner 1 operated by an operator, and a tape mechanical control unit. An input changeover switch for switching the input from each of 4 and MD control unit 5, 7 is a power amplifier, 8 is a speaker, and 9 is a reproduction volume adjustment volume. In such a system, the system control microcomputer 2 transmits a ready (RDY) signal S as shown in FIG.
1. Clock (CLK) signal S2, key data (KEY
DATA) signal S3, mode data (MODEDAT)
A) Periodic communication is performed using the signal S4. Such communication control will be described. However, this communication control will be described between the system control microcomputer 2 and the MD control unit 5.

First, the ready signal S1 is given from the MD control unit 5 to the system control microcomputer 2. The system control microcomputer 2 can know that the communication control is enabled by the input of the ready signal S1.

The clock signal S2 is output from the system control microcomputer 2 to each unit 4 for MD control. This clock signal S2 is used for transmitting an instruction command from the system control microcomputer 2 to the MD control unit 5 and for reading the state of the MD control unit 5 to the system control microcomputer 2 when setting and reading the data. , And includes the highest frequency among the four communication lines between the system control microcomputer 2 and the MD control unit 5.

The key data signal S3 is a clock signal S2
Is a data signal output from the system control microcomputer 2 to the MD control unit 5 to set communication data at the falling edge of the signal.

The mode data signal S4 is a data signal output from the MD control unit 5 to the system control microcomputer 2, and is data on the state of the MD control unit 5.

If the basic period of the clock signal S2 is T0 among the signals S1 to S4, the frequency (first frequency fa) of the clock signal S2 at this time is 1 / T0. The beat frequency, which is the absolute value of the difference between the harmonic that is an integral multiple of the first frequency fa and the carrier frequency f0 of the radio broadcast received by the electronic tunable tuner 1, is 15 kHz.
When the value is within z, the operator hears the beat as described above. For example, if the basic period T0 is 10 μsec, the first frequency fa of the clock signal S2 is 100 kHz.
Therefore, at the reception frequency of the AM radio broadcast in Japan, 6 to 16 times the first frequency fa becomes a problem regarding the beat. Therefore, the reception frequencies 522 to 16
Radio frequency station reception frequency span of 9 kHz at 29 kHz
z, the first frequency fa of the clock signal S2 becomes 10
When the frequency is 0 kHz, a harmonic that is six times the first frequency fa of the clock signal S2, that is, 600 kHz, will be described as an example.
In this case, the beat frequency between the harmonic and 600 kHz is 15 kHz, the beat frequency is 6 kHz at 594 kHz, the beat frequency is 3 kHz at 603 kHz, and the beat frequency is 12 kHz at 612 kHz. Therefore, when the first frequency fa of the clock signal S2 is 600 kHz, the radio broadcast reception frequency is 15 kHz or less for any of the above.
The audible beat is less than z.

In such a case, in the present embodiment, the basic period T0 of the clock signal S2 is changed from 9 μHz to, for example, 9.09 μHz, and the frequency (second frequency fa ′) of the clock signal S2 is changed from 100 kHz to 110 kHz.
By changing to z, a harmonic that is six times the frequency of the clock signal S2 after the change becomes 660 kHz. Then, in this case, the beat frequency is 75 kHz in the above case.
z, the beat frequency is 66 kHz in the above, the beat frequency is 57 kHz in the above, and the beat frequency is 48 kHz in the above, and no audible beat is generated in any of the above cases. Therefore, by providing some basic periods T0, it is possible to prevent the generation of an audible beat due to the clock signal S2 for communication between the system control microcomputer 2 and the MD control unit 5.

Next, the actual operation will be described with reference to the flowchart of FIG.

At present, it is assumed that the electronic tunable tuner is receiving AM radio broadcast by communication control from the system control microcomputer 2. Then, in step n1, the system control microcomputer 2 determines whether or not it is necessary to change the radio reception frequency f0 of the radio broadcast station by the key operation input of the operator. When it is determined that the radio reception frequency f0 needs to be changed by the key operation of the operator, the system control microcomputer 2 mutes (MUTE) so that the sound is not output from the speaker 8 in step n2. Here, since the muting can be performed by a known method, a detailed description thereof will be omitted. After the mute, the system control microcomputer 2 changes the reception frequency f0 of the electronically tunable tuner 1 in accordance with the above key operation in the communication control with the electronically tunable tuner 1 in step n3.
After this change, the system control microcomputer 2
In step n4, at the current frequency fa of the clock signal S2 for communication with the MD control unit 5, whether the harmonic nfa generates an audible beat of about 15 kHz or less with respect to the reception frequency f0. Is determined. In this determination, the system control microcomputer 2 may refer to the data simulated in advance by the calculation in the internal CPU or the like stored in the memory, or to calculate the data when the reception frequency f0 is changed. It doesn't matter.

If the system control microcomputer 2 determines in step n4 that the reception frequency f0 is the audible beat generation frequency, the system control microcomputer 2 changes the frequency of the clock signal S2 from the first frequency fa to the second frequency fa 'in step n5. change. After this change, the system control microcomputer 2 cancels the mute in step n6 to end the communication control processing.

In the above-described embodiment, the occurrence of a beat is determined when the reception frequency f0 is changed. However, the frequency of the clock signal S2 corresponding to the reception frequency f0 is stored in a memory in advance, and accordingly, It is also possible to receive.

Embodiment 2 FIG. 4 is a circuit block diagram of an audio apparatus with a radio reception function according to Embodiment 2 of the present invention. Parts corresponding to those in FIG. Detailed description of the parts related to the reference numerals is omitted. In the acoustic device according to the second embodiment, the electronic tunable tuner 1 and the MD control unit 5 are combined.

Referring to FIG. 4, 1 is an electronic tuning type tuner, 2 is a system control microcomputer, 3 is a display device, 5 is an MD control unit, 6 is an input changeover switch, 7 is a power amplifier, 8 is a speaker, 9 Is a reproduction volume adjustment volume, and 14 is a key operation unit.

The MD control unit 5
It has an MD control microcomputer 10, an MD audio signal encoding / decoding unit 11, a D / A converter 12a for converting a digital signal to an analog signal during reproduction, and an A / D converter 12b for converting an analog signal to a digital signal during recording. It has a converter unit 12.

Further, the MD control unit 5
Has a 4 mega D-RAM 13 for sound skipping, an MD servo controller 15, an MD high frequency (HF) amplifier 16, a magnetic head driver 17, an MD pickup 18, and an track 19 for compressing and expanding recorded data during recording and reproduction. ing.

In the encode / decode section 11 of the MD control unit 5, the MD control microcomputer 10 controls the converter unit 12
256 fs (where fs is 44.1 kHz) for each of the D / A converter 12a and the A / D converter 12b.
z sampling frequency) and a system clock of 384 fs, and 256 fs or 3 fs.
An operation selection signal of 84 fs can also be output. In this case, the operation selection signal may be directly output from the MD control microcomputer 10 to the D / A converter 12a and the A / D converter 12b.

The D / A converter 12a and the A / D converter 12b have 256 fs and 384 fs, respectively.
It operates with the system clock of.

Next, the operation will be described with reference to the flowchart of FIG. However, the description will be made assuming that recording is performed by the MD control unit 5 of the electronic tuning type tuner 1. Therefore, in order to operate the A / D converter 12b to convert an analog signal into a digital signal, encoding / decoding is performed. The unit 11 has 256f for each of the D / A converter 12a and the A / D converter 12b.
The description will be made assuming that the s clock is input.

At this time, the basic frequency fm of the system clock signal of the A / D converter 12b is 256 fs, that is, 256 × 44.1 kHz = 11.2896 MHz. At the receiving frequency fm of domestic FM radio broadcasting, 7 to 9 times the fundamental frequency fm of the system clock signal is a problem in generating beats. Here, at a receiving frequency of 76 to 90 MHz from the FM radio broadcasting station side, 100
kHz span, and here, 77.0272 MHz, which is 7 times the fundamental frequency fm of the system clock signal.
This will be described with reference to an example.

When the reception frequency is 79.0 MHz, the beat frequency is from 79.0272 MHz to 79.0 MHz.
27.2 KHz, which is the absolute value obtained by subtracting, is the occurrence of a beat (of the frequency indicated therein). The beat of this frequency does not become an audible beat, but this is at the time of non-modulation, and in fact, since the carrier is modulated (± 75)
KHz) In practice, an audio frequency beat occurs.

At this time, assuming that the fundamental frequency of the system clock signal of the A / D converter 12b is 384 × 44.1 kHz = 16.9344 MHz, which is fm to fm ′, the fourth harmonic is 67.7376 MHz and the fifth harmonic is 5 ×. Becomes 84.672 MHz, so that a beat between the reception frequency of 79.0 MHz can be clearly prevented.

The operation will be described with reference to the flowchart of FIG.

It is assumed that the FM radio broadcast is currently being received by the electronically tunable tuner 1 in step n7. Then, in step n8, the system control microcomputer 2 determines whether the reception frequency fm of the FM radio broadcast station needs to be changed by key operation input. If it is determined in this determination that the reception frequency fm needs to be changed, the system control microcomputer 2 changes the reception frequency fm after muting in step n9 in the same manner as described above. Next, in step n10, the current basic frequency fm of the system clock signal of the A / D converter 12a.
In, it is determined whether or not a beat occurs. This can be done by referring to the data simulated in advance in the same manner as in the first embodiment and stored in the memory, or calculating when the reception frequency is changed. If the determination in step n10 is a beat generation frequency, the system control microcomputer 2 sends the converter unit 12
That the fundamental frequency of the system clock signal of the D / A converter 12a and the A / D converter 12b in the needs to be changed from fm to fm ′. Upon receiving this, the MD control microcomputer 10 proceeds to step n.
In the encoding / decoding unit 11, the frequency of the system clock supplied to the D / A converter 12a and the A / D converter 12b is changed from fm to fm ', and while the switching time is waited in step n12, the D / A After the clocks of the A converter 12a and the A / D converter 12b are switched, the mute is released in step n13, and the process ends.

In the second embodiment, the occurrence of a beat is determined when the reception frequency fm is changed. However, the basic frequencies fm and fm 'of the system clock signal of the A / D converter 12b corresponding to the reception frequency are determined in advance. It is also possible to store it in a memory and receive it according to it.

[0034]

As described above, in any of the embodiments of the present invention, the harmonics of the frequency of the clock signal between the system control microcomputer and the sound unit or the system of the two converters during reception of the radio broadcast via the tuner. When the harmonic of the fundamental frequency of the clock signal and the reception frequency of the radio broadcast cause a beat, the frequency of the clock signal or the fundamental frequency of the system clock signal is changed, so that the generation of the beat during the reception of the radio broadcast is prevented. It is possible to surely prevent the occurrence of the beat without using a complicated means as in the related art, and also to prevent the occurrence of a simple beat, thereby reducing the cost of such a device.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an audio device with a radio reception function according to a first embodiment of the present invention.

FIG. 2 is a diagram showing communication signals between a system control microcomputer 2 of FIG. 1 and both units 4 and 5;

FIG. 3 is a flowchart for explaining the operation of the first embodiment.

FIG. 4 is a circuit block diagram of an audio device with a radio reception function according to a second embodiment of the present invention.

FIG. 5 is a flowchart for explaining the operation of the second embodiment.

FIG. 6 is a frequency characteristic diagram for explaining occurrence of a beat during reception of an AM radio broadcast by a conventional audio device with a radio reception function.

FIG. 7 is a frequency characteristic diagram for explaining beat generation during FM radio broadcast reception by a conventional audio device with a radio reception function.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic tuning type tuner 2 System control microcomputer 4 Tape mechanism control unit 5 MD control unit 6 Input changeover switch 7 Power amplifier 8 Speaker 9 Reproduction volume control volume 10 Encode / decode part 12 Converter unit 12a D / A converter

Claims (2)

[Claims] A tuner controlled by a system control microcomputer and a sound unit, wherein the system control microcomputer controls the communication of the tuner by an operation input and receives the radio broadcast via the tuner. With a radio reception function, the frequency of the clock signal can be changed when a harmonic of the frequency of the clock signal between the microcomputer and the sound unit and the reception frequency of the radio broadcast cause a beat. Sound equipment. 2. A system control microcomputer comprising a tuner and an audio unit which are communicatively controlled by a system control microcomputer, wherein the audio unit includes a converter unit including a D / A converter and an A / D converter. If the harmonics of the fundamental frequency of the system clock signal of both converters and the reception frequency of the radio broadcast cause a beat during communication control of the tuner by operation input and reception of the radio broadcast via the tuner, the basic An audio device with a radio reception function, wherein the frequency can be changed.