CN103096212A

CN103096212A - Low-voltage single-tube frequency modulation wireless microphone

Info

Publication number: CN103096212A
Application number: CN 201210567883
Authority: CN
Inventors: 周芸
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-12-25
Filing date: 2012-12-25
Publication date: 2013-05-08

Abstract

The invention relates to a low-voltage single-tube frequency modulation wireless microphone which is characterized by comprising a 1.5v battery, an adapterization circuit, a transistor biasing circuit, and a high frequency oscillation and radiating circuit. According to the low-voltage single-tube frequency modulation wireless microphone, the single 1.5v battery and a single NPN type transistor are adopted, oscillation frequency of the high frequency oscillation and radiating circuit is changed, and therefore acoustical signals are modulated to frequency-modulated waves. Due to the fact that the circuits use only one NPN type transistor, the circuits are involved and interfered less by front stages and back stages, the frequency of the frequency oscillation circuit is enabled to be stable, and the low-voltage single-tube frequency modulation wireless microphone is suitable for high-fidelity signal transmission of wireless headphones and the like and for the fields of classroom teaching, travels and the like.

Description

Low-voltage single tube frequency modulation wireless microphone

Technical field

The invention belongs to electronics and communication technique field, is about a kind of low-voltage single tube frequency modulation wireless microphone.

Background technology

The present invention adopts single-unit 1.5V battery, single NPN transistor, by changing the frequency of oscillation of high-frequency oscillating circuits, becomes frequency-modulated wave thereby voice signal is modulated.Because circuit only uses a NPN transistor, circuit is subjected to involving and disturbing less of front and back level, makes the frequency of oscillating circuit more stable, is suitable for the high fidelity signal transmission such as wireless headset, is applicable to the fields such as classroom instruction, tourism.

Evidence: the present invention uses common discrete component to make a low-voltage single tube frequency modulation wireless microphone, has realized that the frequency modulation wireless microphone circuit structure is simple, the targets such as making is easy, higher-order of oscillation frequency stabilization, little power consumption.The transmitting range of low-voltage single tube frequency modulation wireless microphone can reach 30m.

Below describe the correlation technique content that low-voltage single tube frequency modulation wireless microphone of the present invention relates in detail in manufacturing process.

Summary of the invention

Goal of the invention and beneficial effect: the present invention adopts single-unit 1.5V battery, single NPN transistor, by changing the frequency of oscillation of high-frequency oscillating circuits, becomes frequency-modulated wave thereby voice signal is modulated.Because circuit only uses a NPN transistor, circuit is subjected to involving and disturbing less of front and back level, makes the frequency of oscillating circuit more stable, is suitable for the high fidelity signal transmission such as wireless headset, is applicable to the fields such as classroom instruction, tourism.

Technical characterictic: low-voltage single tube frequency modulation wireless microphone, it is comprised of 1.5V battery, pickup circuit, transistor bias circult, the higher-order of oscillation and radiating circuit, and its feature comprises:

The pickup circuit: it is comprised of Electret condenser microphone MIC, resistance R 1, electrochemical capacitor C1, the end of the output D connecting resistance R1 of Electret condenser microphone MIC and the positive pole of electrochemical capacitor C1, the metal shell S of Electret condenser microphone MIC is connected with circuit ground GND, the anodal VCC of the other end connection circuit of resistance R 1;

Transistor bias circult: it is comprised of NPN transistor BG1, resistance R 2, the end of the base stage connecting resistance R2 of NPN transistor BG1, the anodal VCC of the other end connection circuit of resistance R 2;

the higher-order of oscillation and radiating circuit: it is by NPN transistor BG1, capacitor C 2, higher-order of oscillation coil L1 and L2, negative feedback capacitor C 3, negative feedback resistor R3, coupling capacitance C4 and transmitting antenna AT form, the collector electrode of NPN transistor BG1 connects an end of capacitor C 2, the end of higher-order of oscillation coil L2 and an end of negative feedback capacitor C 3, the end of another termination higher-order of oscillation coil L1 of higher-order of oscillation coil L2 and the end of coupling capacitance C4, the anodal VCC of the other end connection circuit of the other end of capacitor C 2 and higher-order of oscillation coil L1, antenna AT is penetrated in the other end sending and receiving of coupling capacitance C4, the emitter of another termination NPN transistor BG1 of negative feedback capacitor C 3 and the end of negative feedback resistor R3, the other end of negative feedback resistor R3 is connected with circuit ground GND.

1.5V anode is connected with circuit anode VCC, the negative pole of 1.5V battery is connected with circuit ground GND.

The circuit working principle: low-voltage single tube frequency modulation wireless microphone changes voice signal into tone currents by Electret condenser microphone MIC, the high-frequency generator that then is comprised of NPN transistor BG1, higher-order of oscillation coil L1, L2 and capacitor C 2 is modulated into FM signal and is radiated the space by transmitting antenna AT.Within this frequency modulation wireless microphone 30m scope, received by FM wave band FM broadcasting broadcast receiver, after amplifying, broadcast receiver is reduced into sound by wireless loud speaker.Transmitting range is relevant with the operating current size of NPN transistor BG1.

Accompanying drawing is said

Accompanying drawing 1 is the embodiment circuit working schematic diagram that the invention provides a low-voltage single tube frequency modulation wireless microphone.

Embodiment

According to circuit working schematic diagram and the description of drawings of the frequency modulation wireless microphone of low-voltage single tube shown in accompanying drawing 1, and implement to realize the present invention according to the described components and parts specification requirement of embodiment.

The selection of components and parts and technical parameter thereof

When selecting NPN transistor BG1, require transistorized characteristic frequency fT greater than 300MHz, select power transistor in 2SC9018, require β 〉=110;

MIC is Electret condenser microphone, and Electret condenser microphone MIC should select the microphone of two ends output type, and its drain D is audio signal output end, connection circuit ground GND after the metal shell of Electret condenser microphone is connected with source S; It is output that field effect transistor is connected into drain D, is conducive to like this improve the output signal voltage gain, and the sensitivity of Electret condenser microphone is increased; Require the metal shell S connection circuit ground GND of Electret condenser microphone MIC for the anti-interference that improves circuit; Electret condenser microphone sensitivity is higher, and the effect of wireless microphone is better; It is CM-18W type (￠ 10mm * 6.5mm) that Electret condenser microphone MIC can select model;

It is 1/8W metalfilmresistor or fixed carbon resister that resistance is selected power, and the resistance of resistance R 1 is 6.2K Ω; The resistance of resistance R 2 is 10K Ω; The resistance of negative feedback resistor R3 is 6.2 Ω;

C1 is electrochemical capacitor, and capacity is 10 μ F/10V; C2 is ceramic disc capacitor, and capacity is 8.2PF; C3 is ceramic disc capacitor, and capacity is 18PF; C4 is ceramic disc capacitor, and capacity is 47PF.

Circuit production main points and circuit debugging

1. higher-order of oscillation coil L makes: higher-order of oscillation coil is divided into two sections coil windings, require around to identical, higher-order of oscillation coil L1 with ￠ 0.5mm enamelled wire on ￠ 5mm skeleton around 4 circles, higher-order of oscillation coil L2 is around 3 circles;

2. transmitting antenna AT is with the long telescopic antenna of 0.6m, or selects the long flexible conductor of 0.8m, and the end of transmitting antenna AT is welded on the end of coupling capacitance C4, and the other end of transmitting antenna AT trails;

3. first check printed circuit board (PCB) and welding quality, should without short circuit and empty, dry joint phenomenon, then can connect the 1.5V battery.With the universal instrument shelves of direct voltage measure between the base stage of NPN transistor BG1 and emitter voltage should＞0.75V, with two terminal shortcircuits of higher-order of oscillation coil L1 once, between the base stage of NPN transistor BG1 and emitter, voltage should change to some extent, and this explanation high-frequency oscillating circuits is started working;

4. the 2 large I of resistance of the resistance R in transistor bias circult change the operating current of NPN transistor BG1;

5. open FM receiver, the transmitting antenna AT of frequency modulation wireless microphone near FM receiver, then to Electret condenser microphone MIC speech, slowly rotated the FM receiver tuning knob simultaneously, be tuned to till FM receiver receives voice signal sound;

6. if FM receiver can not receive the signal of frequency modulation wireless microphone emission in tuning range, can suitably stretch or compress higher-order of oscillation coil L1, change the spacing width of higher-order of oscillation coil L1, more careful tuning modulation broadcast receiver, until can receive voice signal clearly; Then pull open gradually the distance between wireless microphone and FM receiver, until till distance when reaching 30m, still can receive clearly voice signal.

Claims

1. low-voltage single tube frequency modulation wireless microphone, it is comprised of 1.5V battery, pickup circuit, transistor bias circult, the higher-order of oscillation and radiating circuit, and its feature comprises:

Described pickup circuit is comprised of Electret condenser microphone MIC, resistance R 1, electrochemical capacitor C1, the end of the output D connecting resistance R1 of Electret condenser microphone MIC and the positive pole of electrochemical capacitor C1, the metal shell S of Electret condenser microphone MIC is connected with circuit ground GND, the anodal VCC of the other end connection circuit of resistance R 1;

Described transistor bias circult is comprised of NPN transistor BG1, resistance R 2, the end of the base stage connecting resistance R2 of NPN transistor BG1, the anodal VCC of the other end connection circuit of resistance R 2;

the described higher-order of oscillation and radiating circuit are by NPN transistor BG1, capacitor C 2, higher-order of oscillation coil L1 and L2, negative feedback capacitor C 3, negative feedback resistor R3, coupling capacitance C4 and transmitting antenna AT form, the collector electrode of NPN transistor BG1 connects an end of capacitor C 2, the end of higher-order of oscillation coil L2 and an end of negative feedback capacitor C 3, the end of another termination higher-order of oscillation coil L1 of higher-order of oscillation coil L2 and the end of coupling capacitance C4, the anodal VCC of the other end connection circuit of the other end of capacitor C 2 and higher-order of oscillation coil L1, antenna AT is penetrated in the other end sending and receiving of coupling capacitance C4, the emitter of another termination NPN transistor BG1 of negative feedback capacitor C 3 and the end of negative feedback resistor R3, the other end of negative feedback resistor R3 is connected with circuit ground GND.

2. low-voltage single tube frequency modulation wireless microphone according to claim 1, it is characterized in that: the 1.5V anode is connected with circuit anode VCC, and the negative pole of 1.5V battery is connected with circuit ground GND.