JP2731600B2 - Wireless microphone method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a wireless microphone system. In particular, a voice conference system uses a large number of wireless microphones in a teleconference system such as a video conference system or a decision room system of an executive conference system. The present invention relates to a wireless microphone system suitable for use.

[Conventional technology]

In this type of conventional wireless microphone system, an FM modulator (frequency modulator) is used in a transmitting device, and an FM demodulator is used in a receiving device.

[Problems to be solved by the invention]

In the conventional wireless microphone system described above, since the FM modulation / demodulation system is used, the frequency bandwidth of the modulation signal is widened and the number of communication channels cannot be increased. Further, the number of modulations must be suppressed to a sufficiently small value so that the frequency bandwidth per channel is not widened and mixed into adjacent channels to prevent noise interference. Therefore, on the receiving side, the signal-to-noise (S / N) ratio deteriorates. Further, in the FM modulation / demodulation system, when two or more signals are transmitted simultaneously at the same carrier frequency, they interfere with each other and it is difficult to faithfully reproduce the audio signal of each wave. As a result, there is a problem that it is difficult to realize a wireless microphone system that can use many microphones at the same time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a wireless microphone system that can solve the above-mentioned problems and can use many microphones at the same time.

[Means for solving the problem]

The wireless microphone system according to the present invention includes a balanced modulation unit that generates a modulated signal in which a carrier for transmission is amplitude-modulated by an audio signal emitted from a microphone for transmission to generate a carrier-suppressed modulated signal, and an antenna that transmits the modulated signal to the air. A plurality of transmitting devices, an antenna for receiving the modulated signal from the air, and a demodulating means for demodulating the modulated signal received on a receiving carrier having substantially the same frequency as the transmitting local carrier to reproduce the audio signal. In a wireless microphone system having at least one receiving device each having: a receiving device and a multiplying means for frequency-multiplying a fundamental frequency signal to generate the receiving local carrier, and a transmitting carrier with the fundamental frequency signal. One master station device having transmitting means for transmitting a signal obtained by modulation from the antenna to the air,
Receiving means for receiving the modulated signal transmitted to the air from the antenna of the transmitting apparatus and the master station by the antenna, demodulating and reproducing the fundamental frequency signal, frequency-multiplying the reproduced signal, and generating the transmitting local carrier; This is a wireless microphone system including a plurality of slave station devices.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. Each of the plurality of transmitting devices 1A and 1B has an amplifier 5, a balanced modulator 6, an oscillator 7, a band-pass filter (BPF) 8, an output amplifier 9, and a transmitting antenna 10 for amplifying an audio signal transmitted by the microphone 4. It is configured. The receiving device 2 includes a receiving antenna 11, a high-frequency amplifier 12, a demodulator 1
3, oscillator 7, low pass filter (LPF) 14, audio output amplifier 1
5, it has a speaker 16 and an audio output terminal 17.

In the transmission devices 1A and 1B, the audio signal is amplified by the amplifier 5 and then sent to the balanced modulator 6. Balanced modulator 6
Performs amplitude modulation of the carrier generated by the oscillator 7 with a voice signal, generates a carrier-suppressed double-sideband modulation (DSB) signal, and sends the signal to the band pass filter (BPF) 8. The BPF 8 extracts one of the single-sideband modulated signals from the carrier-suppressed double-sideband modulated signals and sends the extracted single-sideband modulated signal to the output amplifier 9. The output amplifier 9 amplifies the single sideband modulated signal and sends it to the transmitting antenna 10. The transmitting antenna 10 transmits the modulated signal to the aerial transmission path 3 as a radio wave.

In the receiving apparatus 2, the receiving antenna 11 sends the modulated signal received from the aerial transmission line 3 to the high-frequency amplifier 12. The high frequency amplifier 12 amplifies the received modulation signal and sends it to the demodulator 13. The demodulator 13 demodulates with the carrier wave generated by the oscillator 7 to reproduce the audio signal component. This reproduced audio signal is transmitted by the transmitter 1A.
And 1B, and does not include mutual interference. The audio signal from the demodulator 13 is sent to a reducing wave (LPF) 14, where an unnecessary signal component is removed, and sent to an audio output amplifier 15. The audio output amplifier 15 outputs the audio signal
A10 and A20 are amplified, branched into two, and sent to the speaker 16 and the audio output terminal 17. The speaker 16 reproduces audio, and the audio output terminal 17 is an output terminal for supplying the audio signal to an audio conference system of a teleconference system, an audio system of a decision room system, or the like.

In this embodiment, since the carrier modulation single-sideband amplitude modulation / demodulation method is used, even if transmission is performed by a plurality of transmitters using the same frequency carrier, the audio signal of each wave is faithfully reproduced without mutual interference. it can.

FIG. 2 is a block diagram showing a second embodiment of the present invention, in which a carrier wave of each transmitting apparatus in the first embodiment is frequency-synchronized from a master station. Master station device 20
Is an oscillator circuit (OSC) that generates the fundamental frequency of the local carrier.
1. A modulation path including a modulator 22 for modulating a carrier at this fundamental frequency and a band-pass filter (BPF) 23. A phase-locked loop (PLL) for generating a local carrier by frequency-doubling the fundamental frequency generated by the OSC 21. ) 28, a demodulation path including a band-pass filter (BPF) 26 and a demodulator 27, and a coupling circuit 24 for guiding a transmission signal of the modulation path to the antenna 25, and a reception signal of the antenna 25 to the demodulation path, It is configured with 25.

Each of the slave station devices 30A and 30B is an antenna 34 coupled to the antenna 25 via the aerial transmission line 3,
A distribution circuit 33 for transmitting and receiving a signal between 34 and a demodulation path and a modulation path, a demodulation path including a band-pass filter (BPF) 35 and a demodulator 36, and a frequency-multiplied transmission signal of the demodulation path generates a local carrier. It comprises a phase locked loop (PLL) 37, a balanced modulator 31 for modulating a local carrier with a microphone audio signal (A) or (B), and a bandpass filter (BPF) 32.

In the master station device 20, the OSC 21 sends the fundamental frequency to the PLL 28 and the modulator 22. The modulator 22 is an amplitude modulator, and modulates the amplitude of a carrier having a predetermined frequency with the fundamental frequency sent from the OSC 21 and sends it to the BPF 23. The BPF 23 suppresses out-of-band components other than the double-sideband components included in the amplitude modulation signal, and sends them to the coupling circuit 24. In the demodulation path, after the signal sent from the coupling circuit 24 passes through the BPF 26, the signal is demodulated by the local carrier sent by the PLL 28 in the demodulator 27, and the superimposed signal of the microphone audio signals (A) and (B) is Will be played. The above-described amplitude modulation signal is sent from the coupling circuit 24 to the antenna 25 and sent out to the aerial transmission line 3 as a radio wave.

The BPFs 35 of the slave station devices 30A and 30B are bandpass filters for passing the amplitude modulated signal received from the master station device 20 and suppressing other unnecessary components. The demodulator 36 is an envelope detector, and performs envelope detection on the received amplitude modulation signal to reproduce the fundamental frequency of the local carrier. The transmission signal on the demodulation path, that is, the fundamental frequency, is frequency-multiplied by the PLL 37 to become a local carrier having the same frequency as that of the master station device 20.
Sent to 31. The microphone audio signal (A) or (B) is sent to the balanced modulator 31 and performs amplitude modulation with carrier suppression on the subcarrier. The BPF 32 blocks an unnecessary sideband component included in the amplitude modulation signal, passes a required single sideband component, and sends it to the distribution circuit 33.

As described above, in the present embodiment, the fundamental frequency for obtaining the local carrier is transmitted from the master station device 20 to the slave station devices 30A and 30A.
By wirelessly transmitting to the base station 0B, the local station apparatus 30A and 30B can generate a local carrier having the same frequency as that of the base station apparatus 20, even if the fundamental frequency fluctuates. First
In this embodiment, as compared with the case where each device must use an oscillator having a high accuracy of the oscillation frequency (for example, a temperature-compensated crystal oscillator), the frequency accuracy of the OSC21 in this embodiment is lower than that of the first embodiment. An oscillator (for example, a crystal oscillator without temperature compensation) may be used, and the local carrier oscillating means can be made smaller and less expensive than in the past.

In the present embodiment, the case where the amplitude modulation is performed as the modulation method of the fundamental frequency has been described. However, it is clear that the wireless transmission of the fundamental frequency can be performed even if the frequency modulation or the frequency transition modulation is applied. An effect similar to that of the embodiment can be obtained.

〔The invention's effect〕

As described above, according to the present invention, by using the amplitude modulation method, the required bandwidth can be reduced, interference with other systems can be reduced, and a large number of microphones can be used simultaneously at the same frequency. There is an effect that a wireless microphone system that can be realized can be realized.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are block diagrams showing an embodiment of the present invention. 1A, 1B: transmitting apparatus, 2: receiving apparatus, 3: aerial transmission path, 4: microphone, 5: amplifier, 6, 31 ... balanced modulator, 7: oscillator, 8, 23, 26 , 32,35 …… BPF, 9 ……
Output amplifier, 10: transmitting antenna, 11: receiving antenna, 12: high-frequency amplifier, 13, 27, 36 ... demodulator, 14 ...
LPF, 15 …… Audio output amplifier, 16 …… Speaker, 17 ……
Audio output terminal, 20: master station device, 30A, 30B: slave station device, 21: OSC, 22: modulator, 24: coupling circuit, 25, 34
... antenna, 28, 37 ... PLL, 33 ... distribution circuit.

Claims (1)

(57) [Claims] 1. A plurality of balanced modulation means for generating a modulated signal having a carrier suppressed by amplitude-modulating a carrier for transmission with an audio signal emitted from a microphone for transmission, and an antenna for transmitting the modulated signal into the air. A transmitting device, an antenna for receiving the modulated signal from the air, and a demodulating means for demodulating the modulated signal received on a receiving carrier having substantially the same frequency as the transmitting local carrier to reproduce the audio signal. In a wireless microphone system having at least one receiving device, the receiving device and a frequency multiplier for frequency-multiplying a fundamental frequency signal to generate the receiving local carrier, and modulating a transmitting carrier with the fundamental frequency signal. One master station device having transmission means for transmitting a signal to be obtained from the antenna to the air, and an antenna of the transmission device and the antenna of the master station device. And a plurality of slave stations each having receiving means for receiving the demodulated signal transmitted in the air by an antenna, demodulating the signal, reproducing the fundamental frequency signal, frequency-multiplying the signal, and generating the transmission local carrier. A wireless microphone system characterized by that.