CN202334879U

CN202334879U - Simple and reliable frequency modulation wireless microphone

Info

Publication number: CN202334879U
Application number: CN2011203536686U
Authority: CN
Inventors: 朱虹
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-09-21
Filing date: 2011-09-21
Publication date: 2012-07-11
Anticipated expiration: 2021-09-21

Abstract

The utility model relates to a simple and reliable frequency modulation wireless microphone which is composed of a direct current power supply DC, a power supply filter circuit, an audio signal input circuit and a high frequency oscillating and emitting circuit, the simple and reliable frequency modulation wireless microphone is characterized in that the high frequency oscillating and emitting circuit comprises an offsetting circuit of an NPN type transistor VT1 and an audio signal input circuit. According to the utility model, a single NPN type transistor and a single battery are used, and the frequency of a high frequency oscillator is changed by changing the junction capacitance between b-c of the NPN type transistor in the high frequency oscillating circuit so as to modulate the oscillating frequency to frequency modulation wave. Only one NPN type transistor is used in the circuit, so that the frequency of the oscillating circuit is stable, and the frequency modulation wireless microphone is suitable for signal transmission with high fidelity demand, for example, television wireless earphone and the like.

Description

Simplest and dependable frequency modulation wireless microphone

Technical field

The utility model belongs to electronics and communication technique field, relates to a kind of simplest and dependable frequency modulation wireless microphone.

Background technology

The utility model adopts single NPN transistor, single battery, and the junction capacitance between transistor b-c changes the frequency that changes high-frequency generator in the high-frequency oscillating circuits through changing, thereby the frequency of oscillation modulation is become frequency-modulated wave.Because of circuit only uses a NPN transistor, the involving and disturb fewly of level before and after circuit receives makes that the frequency of oscillating circuit is more stable, is suitable for the signal transmission that fidelity such as tv wireless earphone is had relatively high expectations, or is used for field such as classroom instruction.Evidence: the utility model uses several common discrete components, has realized that frequency modulation wireless microphone circuit structure is simple, the stable difficult purposes such as easy, with low cost and little power consumption of running frequently, make of frequency of oscillation.

Below specify the correlation technique content that this simplest and dependable frequency modulation wireless microphone relates in manufacturing process.

The utility model content

Goal of the invention and beneficial effect: the utility model adopts single NPN transistor, single battery; The junction capacitance between the NPN transistor b-c changes the frequency that changes high-frequency generator in the high-frequency oscillating circuits through changing, thereby modulation becomes frequency-modulated wave to frequency of oscillation.Because of circuit only uses a NPN transistor, make the circuit oscillation frequency more stable, be well suited for being used for the signal transmission that fidelity such as tv wireless earphone is had relatively high expectations.Evidence: the utility model only uses several common discrete components, has realized that frequency modulation wireless microphone circuit structure is simple, frequency of oscillation stablely is difficult for running frequently, with low cost and little power consumption, make easily.

Technical characterictic: simplest and dependable frequency modulation wireless microphone; Be made up of battery DC, electric source filter circuit, audio signal input circuit, the higher-order of oscillation and radiating circuit, it is characterized in that: the higher-order of oscillation and radiating circuit comprise biasing circuit and the audio signal input circuit of NPN transistor VT1.

Annexation in the composition of other circuit and the circuit between the element

The characteristic of the biasing circuit of NPN transistor VT1 and audio signal input circuit is: the base stage of a termination NPN transistor VT1 of the output D of Electret condenser microphone MIC and resistance R 1; The anodal VCC of the other end connection circuit of resistance R 1, the metal shell end S of Electret condenser microphone MIC links to each other with circuit ground GND.

The higher-order of oscillation and radiating circuit: the base stage of NPN transistor VT1 is with connecing an end of capacitor C 1 and the end of higher-order of oscillation coil L; The other end of the other end of capacitor C 1 and higher-order of oscillation coil L links to each other with the collector electrode of NPN transistor VT1, the end of transmitting antenna TX, the emitter connection circuit ground GND of NPN transistor VT1.

The characteristic of battery DC and electric source filter circuit is: an end of capacitor C 2 and the positive pole of electrochemical capacitor C3 connect the end of mains switch K; The positive pole of another termination battery DC of mains switch K; The negative pole connection circuit ground GND of the other end of capacitor C 2 and electrochemical capacitor C3, the negative pole connection circuit ground GND of battery DC.

The circuit working principle: simplest and dependable frequency modulation wireless microphone changes voice signal into tone currents by Electret condenser microphone MIC; The high-frequency generator of being made up of NPN transistor VT1, higher-order of oscillation coil L and capacitor C 1 again forms FM signal and is radiated the space by transmitting antenna TX.In frequency modulation wireless microphone 10m scope, the broadcast receiver reception by frequency modulation(FM) broadcast band (FM wave band) is reduced into sound through loud speaker, realizes the radio transmission of sound.

Description of drawings

Accompanying drawing 1 is the embodiment circuit working schematic diagram that the utility model provides a simplest and dependable frequency modulation wireless microphone; For reducing the interference of electromagnetic signal, require to use the Electret condenser microphone of two ends output type to Electret condenser microphone MIC.

Embodiment

According to the circuit working schematic diagram and the description of drawings of the wireless microphone of simplest and dependable frequency modulation shown in the accompanying drawing 1, and implement to realize the utility model according to the described components and parts specification requirement of embodiment.

The selection of components and parts and technical parameter thereof

MIC is an Electret condenser microphone, and Electret condenser microphone MIC should select the microphone of two ends output type for use, and its drain D is an audio signal output end, connection circuit ground GND after the metal shell end of Electret condenser microphone links to each other with source S.It is output that FET is connected into drain D, helps improving the gain of output voltage of signals, and the sensitivity of Electret condenser microphone is increased.Require the shell ends S connection circuit ground GND of Electret condenser microphone MIC, to improve the anti-interference of circuit.

Electret condenser microphone sensitivity is high more, and the effect of wireless microphone is good more.Electret condenser microphone MIC can select CM-18W type (the higher Electret condenser microphone of sensitivity of φ 10mm * 6.5mm) for use;

VT1 is a NPN transistor, selects power transistor among the NPN type 2SC9018 for use, requires β >=110;

It is 1/8W metalfilmresistor or fixed carbon resister that resistance is selected power for use, and the resistance of resistance R 1 is 1K Ω;

C1 is a ceramic disc capacitor, and capacity is 10PF; C2 is an electric capacity of the dacron, and capacity is 0.01 μ F; C3 is an electrochemical capacitor, and capacity is 220 μ F/10V;

L is a higher-order of oscillation coil; K is a mains switch.

The making of circuit and subelement

The making of higher-order of oscillation coil L: flat around 10 circles on the ballpoint pen core of ￠ 3.5mm with the enamelled wire of ￠ 0.5mm, extract the ballpoint pen core then out and form air-core inductance, scrape off behind the coat of paint at inductance coil two ends zinc-plated with pocket knife;

TX is a transmitting antenna, and the telescopic antenna that available 60cm is above also can use 90cm multiply plastics flexible cord as transmitting antenna, and an end is welded on the printed circuit board (PCB), and the other end is stretched out naturally.

The debugging of circuit

The printed circuit board (PCB) correspondence position is inserted in the zinc-plated back of each component pin, and each component pin should stay short as far as possible.Can not make higher-order of oscillation coil L distortion when noting the welding coil.

Inspection printed circuit board (PCB) and welding situation should not have short circuit and empty, dry joint phenomenon earlier, can connect DC power supply then.Measure with the universal instrument shelves of direct voltage between base stage and the emitter of transistor VT1 voltage should＞0.7V, with higher-order of oscillation coil L two terminal shortcircuits once, voltage should have certain variation, this explanation circuit vibrates.

Band switch should place the FM wave band, pulls out the antenna of FM receiver, opens FM receiver, with the transmitting antenna of frequency modulation wireless microphone near FM receiver.Slowly rotate the FM receiver tuning knob then, simultaneously to Electret condenser microphone MIC speech, be tuned to FM receiver receive till the voice signal sound.If FM receiver can not receive the signal of frequency modulation wireless microphone emission in tuning range, can change the width of enamelled wire coil through stretching or compression higher-order of oscillation coil L, careful again tuning modulation broadcast receiver is until receiving voice signal clearly.

Then draw back the distance between wireless microphone and the FM receiver gradually, up to distance when reaching 9～10m, still can receive clearly till the voice signal.Attention wireless microphone tranmitting frequency in debugging should be avoided the frequency in the broadcasting station in the local fm band.

No. 5 batteries of 1 joint are as power supply, and the operating current of frequency modulation wireless microphone is about 19mA.Select for use the high-quality alkaline battery about 400mAh of every joint capacity (MAH) to be example, but No. 5 battery running hours of 1 joint were about 40 hours.In actual use, the different times that continue to use of kind because of battery have discrepancy.

Claims

1. simplest and dependable frequency modulation wireless microphone; Be made up of battery DC, electric source filter circuit, audio signal input circuit, the higher-order of oscillation and radiating circuit, it is characterized in that: the higher-order of oscillation and radiating circuit comprise biasing circuit and the audio signal input circuit of NPN transistor VT1.

2. simplest and dependable frequency modulation wireless microphone according to claim 1; It is characterized in that: the base stage of a termination NPN transistor VT1 of the output D of the Electret condenser microphone MIC in the biasing circuit of NPN transistor VT1 and the audio signal input circuit and resistance R 1; The anodal VCC of the other end connection circuit of resistance R 1, the metal shell end S of Electret condenser microphone MIC links to each other with circuit ground GND.

3. simplest and dependable frequency modulation wireless microphone according to claim 1; It is characterized in that: the base stage of the NPN transistor VT1 in the higher-order of oscillation and the radiating circuit is with connecing an end of capacitor C 1 and the end of higher-order of oscillation coil L; The other end of the other end of capacitor C 1 and higher-order of oscillation coil L links to each other with the collector electrode of NPN transistor VT1, the end of transmitting antenna TX, the emitter connection circuit ground GND of NPN transistor VT1.

4. simplest and dependable frequency modulation wireless microphone according to claim 1; It is characterized in that: an end of the capacitor C 2 in the electric source filter circuit and the positive pole of electrochemical capacitor C3 connect the end of mains switch K; The positive pole of another termination battery DC of mains switch K; The negative pole connection circuit ground GND of the other end of capacitor C 2 and electrochemical capacitor C3, the negative pole of battery DC links to each other with circuit ground GND.