JPH05304488A - Radio trnsmitting type voice signal reproducing device - Google Patents

Abstract

PURPOSE:To aboid beat interference due to the mutual modulation among plural oscillators by using a single resonator type oscillator in common for the frequency conversion of a voice signal transmission circuit and the source oscillation of the local oscillation frequency of a control signal reception circuit. CONSTITUTION:A pair of carrier voice signals SL and SR are formed by modulating a pair of the carrier waves of a prescribed frequency interval by a pair of voice signals L and R reproduced from a recording medium MT. A voice signal transmission part 20A is provided to frequency convert these signals SL and SR by each equivalent amount by a pair of mixers 24L and 24R and to transmit the signals. Simultaneously, a superheterodyne constituted control signal reception part 50 is provided to receive a control signal Sct from a remote control part provided on the reception part for receiving the audio signal from the transmittion part 20A. Then, an oscillator 54 is used in common for converting the frequency of the transmission part 20A and for the local oscillation of the reception part 50. Thus, the beat interference due to the mutual modulation among the plural oscillators can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless transmission type audio signal reproducing apparatus suitable for, for example, a headphone type stereo cassette player.

[0002]

2. Description of the Related Art Conventionally, as a headphone type stereo cassette player (hereinafter simply referred to as "player") such as a Walkman (registered trademark), there is known a wireless transmission system between the player and the headphones. ing.

FIG. 3 is a perspective view showing the appearance of an example of a wireless player, 1 is a player, and 6 is a dedicated receiver for the headphones thereof.

In the player 1, when the stereo audio signals L and R of the left and right channels are reproduced from the tape cassette (not shown) during reproduction, the signals L and R use two carriers having a predetermined frequency interval. The converted FM signals SL and SR are converted, and the FM signals SL and SR are transmitted to the receiver 6.

When the receiver receives the FM signals SL and SR from the player 1, the signals S and SR are received.
The audio signals L and R are demodulated from L and SR, and the demodulated audio signals L and R are output to the left and right acoustic units 7L and 7L of the headphones 7.
It is supplied to each 7R.

In this case, the receiver 6 can be half the size of a business card or smaller. Therefore, for example, when playing a cassette tape on a train for commuting, the player 1 puts the receiver 6 in a bag, a bag, etc. and puts the receiver 6 in a chest pocket of a jacket, or attaches it to a collar or a tie with a clip. The cord of the headphone 7 does not get in the way.

Note that the distance at which the receiver 6 can be used away from the player 1 is set in consideration of the Radio Law and the case where nearby people are using the same wireless type player.
It is about 5 m.

References: Japanese Patent Application No. 61-254966 (Japanese Patent Application Laid-Open No. 63-108825) and Japanese Patent Application No. 62-280489.
Issue, etc.

[0009]

By the way, in the above-mentioned wireless player, the player 1 and the receiver 6 are used.
The headphones 7 and the headphones 7 are usually used separately from each other (for that reason, a wireless system is used), and especially when the player 1 is put in a bag, a bag or the like, the operation mode is switched. There was a problem that the button operation of was troublesome.

In order to solve the above-mentioned problems, the applicant of the present application, in Japanese Patent Application No. 1-177404, mounts a commander on the headphone side and transmits a coded control signal from the headphone side to set the operation mode of the player. We have already proposed a "remote control device" for controlling. As shown in FIG. 4, on the player side of this conventional device, an audio signal reproducing circuit 10, an audio signal transmitting circuit 20, a tape running control system 3 are provided.
0, in addition to the system control circuit (microcomputer) 40, a control signal receiving circuit 50 is mounted to receive a remote control signal from the headphone side.

The tape M is formed by the magnetic heads 11L and 11R.
The left and right audio signals reproduced from T are amplified by amplifiers 12L and 1L.
2R is equalized and amplified, and passes through the emphasis circuits 21L and 21R of the transmission circuit 20 and then to the FM modulators 22L and 2L.
It is supplied to 2R. In the FM modulators 22L and 22R, the original carriers generated by the oscillators 23L and 23R are modulated by the left and right audio signals from the emphasis circuits 21L and 21R to form a pair of FM signals SL and SR.

The FM modulators 22L and 22R include, for example, semiconductor elements such as variable capacitance diodes and are integrated with the respective oscillators 23L and 23R.

In the conventional example of FIG. 4, a pair of FM signals SL,
SR frequency shift is, for example, 75k at 100% modulation
While being set to Hz, the original carrier frequencies fLo and fRo of the FM signals SL and SR are considerably lower than the original transmission frequency (carrier frequency), as shown in FIG. 5, for example, fLo = 11.29MHz fRo = 11. .75 MHz Δf = fRo−fLo = 460 kHz.

The FM signals SL and SR are mixed in the mixers 24L and 24L,
The signal Sup for frequency conversion (up conversion) is supplied from the oscillator 25 to the mixers 24L,
It is supplied to 4R. The frequency fup of the signal Sup is set as, for example, fup = 64.00 MHz as shown in FIG.

In the conventional example of FIG. 4, the resonance circuit of the oscillator 25 is composed of a highly stable solid state resonator 26 such as a lithium tantalate resonator, and the solid state resonator is in the fifth harmonic mode, for example. used.

In the mixers 24L and 24R, the frequency conversion signal Sup and the FM signals SL and SR are mixed, respectively, and the carrier frequencies fLh, of the FM signals SL, SR taken out from the bandpass filters 27L, 27R are mixed. fR
As shown in FIG. 5, h is converted to a high value up to near the lower limit of the FM broadcasting band, for example, fLh = 75.29 MHz fRh = 75.75 MHz. Then, such FM signals SL, S
R is transmitted from the antenna At through the high frequency amplifiers 28L and 28R and the filter (not shown).

The tape running control system 30 includes a capstan 3
1, a motor 32, and a control mechanism (not shown) that controls the mechanical state of the player 1 using the rotational force of the motor 32, and is controlled by the system control circuit 40.

The system control circuit 40 includes a decoder 41 for remote control, and a control signal receiving circuit 5 as described below.
A demodulation output of 0 is provided. The control signal output from the decoder 41 or the operation key 42 on the player 1 side
The operation state of the player 1 is controlled based on the control signal from the.

On the other hand, in the control signal receiving circuit 50, the control signal Sct transmitted from the commander (not shown) mounted on the headphone side is received via the antenna Ar. The receiving circuit 50 has a super-heterodyne configuration, the control signal Sct from the antenna Ar is supplied to the mixer 52 via a tuning circuit (not shown) and a high-frequency amplifier 51, and the resonance circuit is a solid resonator. The output of the oscillator 54 constituted by 53 is supplied to the mixer 52 as the local oscillation signal SLO via the frequency multiplier 55. Then, the control signal Sct is converted into an intermediate frequency, is supplied to the FM demodulator 58 through the intermediate frequency filter 56 and the amplifier 57, and is demodulated.

In the conventional example shown in FIG. 4, the transmission frequency fct of the control signal Sct is set near the upper limit of the VHF television broadcasting band, for example, fct = 222.30 MHz, and the control signal receiving circuit 50 controls the transmission frequency fct. Intermediate frequency f
i is set to fi = 10.70 MHz, for example, as in a normal FM broadcast receiver.

Therefore, the frequency fLO of the local oscillation signal SLO
Is set to, for example, fLO = 211.60 MHz.

The frequency multiplier f54 of the output signal S54 of the oscillator 54 is set to, for example, f54 = fLO / 4 = 52.90 MHz as shown by the chain line in FIG. To be done.

However, in the conventional example of FIG. 4, on the player side, a total of four oscillators 23L, 23 are provided in the two systems of the audio signal transmitting circuit 20 and the control signal receiving circuit 50 which are independent of each other.
R, 25; 54 are used, and by the intermodulation (intermodulation), each oscillation frequency fLo, fRo, f
There was a risk of beat interference between up, f54 and their harmonics. In particular, in the control signal receiving circuit 50 having a low input level, the frequency difference (fup between the resonator type oscillator 54 and the resonator type oscillator 25 of the audio signal transmitting circuit 20).
Since −f54) is close to the intermediate frequency fi, this frequency difference component is likely to be mixed in the high-gain intermediate frequency amplifier 57, and beat interference is likely to occur.

In order to suppress such beat interference, in the conventional example shown in FIG. 4, the tuning circuit (not shown) of the control signal receiving circuit 50 and the intermediate frequency filter 56 are made multi-element to have high selectivity. Also in the audio signal transmission circuit 20, the filters (not shown) in the subsequent stages of the amplifiers 28L and 28R are made multi-elements so that only the signal components of the predetermined carrier frequencies fLh and fRh are output, which is expensive. However, there is a problem that the space becomes large.

Further, in the conventional example of FIG. 4, in order to stabilize the transmission frequency of the voice signal transmission circuit 20 and the reception frequency of the control signal reception circuit 50, the resonator type oscillator 25,
There is a problem that it is necessary to use 54 and the cost becomes high.

In view of the above points, the present invention is provided with a transmitter for converting a stereo audio signal into a two-carrier FM signal and then frequency conversion, and a remote control signal receiver, and prevents beat interference due to intermodulation between a plurality of oscillators. It is an object of the present invention to provide a wireless transmission type audio signal reproducing device which avoids the cost and space of the device.

[0027]

In order to solve the above-mentioned problems, a wireless transmission type audio signal reproducing apparatus according to the present invention comprises:
Corresponding reference numerals in the embodiments described later correspond to the recording medium MT.
A pair of carrier signals at predetermined frequency intervals are modulated by a pair of audio signals L and R reproduced from
An SR is formed and this carrier audio signal is mixed with a pair of mixers 24.
An audio signal transmitting unit 20A that converts the upper frequency by L and 24R by equal amounts and transmits the same is provided, and a supermarket that receives the control signal Sct from the remote control unit provided in the receiving unit that receives the audio signal from this transmitting unit. In the wireless transmission type audio signal reproducing device including the control signal receiving unit 50 having the heterodyne structure, the common oscillator 54 is used for frequency conversion of the audio signal transmitting unit and local oscillation of the control signal receiving unit.

[0028]

With this structure, beat interference due to intermodulation between a plurality of oscillators can be avoided, and cost and space can be reduced.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wireless transmission type audio signal reproducing apparatus according to the present invention will be described below with reference to FIGS. The configuration of an embodiment of the present invention is shown in FIG. In FIG. 1, parts corresponding to those in FIG. 4 described above are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1, the mixers 24L and 24R of the audio signal transmitting circuit 20A of this example include modulators 22L and 2L, respectively.
The outputs of 2R are supplied, and the output of the oscillator 54 of the control signal receiving circuit 50 is supplied as the frequency conversion signal Sup.

Since the frequency of the oscillator 54 is different from the frequency of the signal oscillator 25 for frequency conversion of the conventional example of FIG. 4 as described above, in this embodiment, the oscillators 23L and 2L are provided.
The 3R original carrier frequencies fLo and fRo are set as shown in FIG. 2, for example, fLo = 22.39 MHz fRo = 22.85 MHz Δf = fRo−fLo = 460 kHz. The other structure is the same as that shown in FIG.

Next, the frequency conversion operation of the embodiment of the present invention will be described with reference to FIG. In this embodiment, the original carrier frequencies fLo and f of the FM signals SL and SR are used.
Ro is set as described above.

On the other hand, the frequency of the frequency conversion signal Sup is
As shown in FIG. 2, for example, fup = f54 = 52.90 MHz is set.

In the mixers 24L and 24R, the frequency conversion signal Sup and the FM signals SL and SR are mixed, respectively, and the carrier frequencies fLh, of the FM signals SL, SR taken out from the bandpass filters 27L, 27R are mixed. f
As shown in FIG. 2, Rh is converted to a high value up to the vicinity of the lower limit of the FM broadcasting band, as in the above-described conventional example, for example, fLh = 75.29 MHz fRh = 75.75 MHz.

As described above, in this embodiment, the audio signal transmitting circuit 20A and the control signal receiving circuit 50 are provided on the player side.
2 oscillators and 3 oscillators 23
L, 23R, 54 are used for the audio signal transmitting circuit 20.
Since the resonator oscillator 25 of FIG. 2 is omitted, as described above, the frequency difference component (fup−f5
4) cannot exist, and the occurrence of beat interference by these is avoided.

Therefore, various filters of the audio signal transmitting circuit 20 and the control signal receiving circuit 50 are simplified, and cost and space are reduced.

Further, in this embodiment, since the single resonator type oscillator is commonly used for the generation of the frequency conversion signal Sup and the original oscillation of the local oscillation frequency, the cost for frequency conversion is also increased. Be reduced.

In this embodiment, FM signals SL, S
The carrier frequencies fLh and fRh of R are the sum of the original carrier frequencies fLo and fRo in a frequency band lower than the frequency band and the frequency fup of the beat-up signal relatively close to the predetermined frequency band. The difference between the original carrier frequencies fLo and fRo and the frequency conversion signal frequency fup can be used depending on the frequency allocation of the television broadcast.

[0039]

As described above, according to the present invention, a stereo voice signal is used as a two-carrier FM signal, and a frequency conversion is performed by a pair of mixers, and a remote control signal receiver having a superheterodyne structure. In a wireless transmission type audio signal reproducing device including a single resonator type oscillator for frequency conversion of an audio signal transmitting circuit and for original oscillation of a local oscillation frequency of a control signal receiving circuit. Therefore, it is possible to obtain a wireless transmission type audio signal reproducing device which can avoid beat interference due to intermodulation between a plurality of oscillators and can reduce cost and space.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a wireless transmission type audio signal reproducing apparatus according to the present invention.

FIG. 2 is a frequency spectrum diagram for explaining the operation of the embodiment of the present invention.

FIG. 3 is a perspective view showing a configuration example of a conventional wireless transmission type audio signal reproducing device.

FIG. 4 is a block diagram showing an electrical configuration of a conventional example.

FIG. 5 is a frequency spectrum diagram for explaining the operation of the conventional example.

[Explanation of symbols]

10 audio signal reproducing circuit 20A audio signal transmitting circuit 24L, 24R, 52 mixer 30 tape running control system 40 system control circuit (microcomputer) 50 control signal receiving circuit 53 solid state resonator 54 oscillator 55 frequency multiplier

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // G11B 33/12 310 A

Claims (4)

[Claims] 1. A pair of carrier signals having a predetermined frequency interval are modulated by a pair of sound signals reproduced from a recording medium to form a pair of carrier sound signals, and the carrier sound signals are frequency-converted by a pair of mixers. A radio including a voice signal transmitting unit for converting and transmitting, and a control signal receiving unit having a super-heterodyne configuration for receiving a control signal from a remote control unit provided in a receiving unit for receiving the voice signal from the transmitting unit. A transmission type audio signal reproducing apparatus, wherein a common oscillator is used for the frequency conversion of the audio signal transmitting section and the local oscillation of the control signal receiving section. 2. The wireless transmission system according to claim 1, wherein the output of the common oscillator is used for the frequency conversion of the voice signal transmitting section and the local oscillation of the control signal receiving section with different multiplication factors. Audio signal reproduction device. 3. A wireless transmission type audio signal reproducing apparatus according to claim 1, wherein said pair of carrier audio signals are frequency-converted by said pair of mixers to shift the frequencies by equal amounts in the same direction. .. 4. The wireless transmission type audio signal reproducing apparatus according to claim 1, wherein the recording medium is a magnetic tape, and a mechanism for reproducing by a magnetic head is provided.