CN2487185Y - Fixed frequency receiving radio FM earphone - Google Patents

Abstract

The utility model discloses a fixed frequency receiving radio FM earphone which consists of a frequency selection circuit, a filtering circuit, an oscillation circuit, a frequency discriminating circuit, a low amplification circuit, and IC1 and IC2 circuits; the utility model adopts high frequency stability crystal JT1 and JT2 as a first self-oscillating loop, the integrated circuit IC1 as a narrow brand frequency modulation receiving circuit, IC2 as a low frequency amplifying circuit, the filter 10.7MHz 455D as a ceramic filter. The utility model has simple structure, convenient installation and use, greatest advantage of no tuning, instant use when connected with the power supply, good voice quality, stable circuit and strong anti-jamming performance.

Description

The fixed radio FM earphone that frequently receives

The utility model relates to a kind of Radio earphone renovation technique.

Existing frequency modulation earphone all adopts manual frequency modulation or button search to transfer the platform mode, change frequency and find out and need FM signal by changing the variable capacitance capacitor amount or changing the variable capacitance diode capacity, reach the reception purpose, the accent platform mode of this similar transistor radio, can meet the demands generally speaking, can finely tune in the use, to guarantee volume and to accept accuracy, but in some cases, but do not allow any adjustment in the use.Common frequency modulation earphone in use needs constantly fine setting, reason just has been to use this mode of LC oscillator, though it is simple, but because ambient temperature changes, various spaces Electromagnetic Interference can make the LC oscillator frequency change, need constantly to adjust, make troubles for normal the use to remedy this variation.

For solving the deficiency that above tuning manner exists, the purpose of this utility model provides a kind of fixed radio FM earphone that receives frequently, only needs opening power just can receive clear voice signal or music signal.

The technical solution of the utility model is achieved in that and adopts the special circuit piece in this earphone frequency modulation circuit, uses crystal oscillation in local oscillation circuit, realizes that single channel or many radio frequency channels receive; Secondly satisfying under the technical indicator prerequisite, it is highly integrated to simplify the circuit level to greatest extent, and peripheral circuit is simplified as far as possible, to reach the purpose of high target high-performance and low-cost.

This circuit structure is by frequency selection circuit, filter circuit, oscillating circuit, frequency-discriminating circuit, low discharging circuit and IC ₁, IC ₂Chunk is formed, IC ₁Circuit inside is made up of High Amplifier Circuit, mixting circuit, two mixing, amplifier, frequency discrimination and low discharging circuit, and its structure is shown in block diagram, and its connection is two filter circuits and IC ₁Middle mixing and two mixting circuits directly connect, and antenna is connected with High Amplifier Circuit in the assembly through frequency-selecting, wherein an oscillating circuit and IC ₁Middle mixting circuit connects another oscillating circuit and IC ₁Middle two mixting circuits that amplify connect frequency discrimination loop and IC ₁Middle frequency-discriminating circuit connects IC ₁In the low low piece IC of putting with external promotion loudspeaker of putting ₂Connect power supply V _CCRespectively with IC ₁With the low IC of putting ₂The loop connects, this circuit structure as shown in Figure 2, one of them filter circuit 10.7MHz and IC ₁19,20,21 pin of mixting circuit connect, filter circuit 455kHz and IC ₁Two mixing, 13 pin connect, IC ₁In low putting through divider resistance R ₄, R ₅, R ₇Direct and the low discharging circuit IC of potentiometer ₂Connect, be connected this vibration loop 455kHz and IC through capacitive coupling with loudspeaker ₁7,8,9 pin connect, and oscillation circuit 10.245MHz is through filtering and IC ₁6 pin connect, the antenna receiving loop is through inductance, capacitive coupling and IC ₁22 pin connect, and entire circuit is by IC ₁IC ₂Two block assemblies and other peripheral circuits are formed, be installed in the earphone, Headphone structure is: the outer beam of earphone constitutes with rubber sleeve, the centre comprises one section 65Mn steel band, plastic clip is housed at the steel band two ends and the both sides casing connects together, and steel band can slide up and down to adapt to the head dummy size, on one side casing is equipped with two joint No.5 cells, the casing opposite side is equipped with circuit board and antenna, and lead passes from middle rubber sleeve.Casing one side is equipped with power supply/volume switch, and opposite side is equipped with light-emitting diode and band switch, switches to realize multichannel.

Characteristics of the present utility model, circuit structure is simple, and is easy to install, and great advantage need not be tuning, and energized is used immediately, and acoustical quality is good, and circuit is stable, strong anti-interference performance.

Detailed structure of the present utility model and operation principle have just reached accompanying drawing by following enforcement and have provided.

Fig. 1 is the fixed radio FM earphone circuit block diagram that frequently receives;

Fig. 2 is the fixed radio FM earphone electrical schematic diagram that frequently receives;

Fig. 3 is the fixed radio FM earphone shape assumption diagram that frequently receives.

Its structure is by shown in the circuit, IC ₁Assembly is that MC13135 is a frequency modulation narrow-band reception circuit block, IC ₂Assembly is that 386D is that low frequency, low-voltage are amplified piece, and two filter circuits all adopt ceramic filter.Headphone structure is 1 for outer beam rubber sleeve, and 2 be antenna, and 3 is that loudspeaker, 4 are internal circuit board, and 5 is battery case, and mains switch is equipped with in the side.

The circuit working process is: come in the FM signal process by L from antenna ₃, C ₁₈, C ₁₉Form frequency-selective circuit and directly enter ic chip ₁By L, C, JT ₁Crystal is formed the first local oscillator loop and is also sent into IC simultaneously ₁, the two amplifies the back simultaneously at IC ₁In carry out the mixing difference and go out 10.7 megahertzes, first intermediate-freuqncy signal and continue to amplify, (first local frequency is operating frequency f ₀10.7 megahertz) by crystal JT ₂(10.245 megahertz) formed second local oscillation signal and also entered IC ₁In, the two carries out mixing after amplifying, and difference goes out 455 kilo hertz of second intermediate-freuqncy signal, and first and second intermediate-freuqncy signal enters IC respectively after 10.7 megahertzes and 455 megahertz ceramic filter filtering ₁In.IC ₁After 455 kilo hertzs of continuation amplifications reach the regulation gain to second intermediate-freuqncy signal, by R ₁₁, L ₂Form frequency-discriminating circuit and also insert IC ₁In, constitute frequency discriminator jointly, 455 kilo hertzs of CF signal are carried out frequency discrimination, remove CF signal, detecting needs voice or music signal, by IC ₁R is passed through in the output of 17 pin ₄, R ₅, potentiometer R ₇, C ₁₃, C ₁₄Form voice control circuit and enter ic chip ₂Carrying out low frequency amplifies.

Suitably adjust IC ₂Peripheral circuit can make audio signal output, distortion reach designing requirement.The low IC of putting ₂The output of the 5th pin is through coupling capacitor C ₂₀Directly promote earphone horn SP ₁, SP ₂

Claims (2)

1. a fixed frequency receives radio FM earphone, it is characterized in that this earphone by frequency selection circuit, filter circuit, oscillating circuit, frequency discrimination loop, low discharging circuit and IC ₁IC ₂Circuit is formed; Adopt high frequency stability crystal JT ₁, JT ₂As first vibration loop, integrated circuit (IC) ₁For circuit is accepted in narrow-band FM, IC ₂Be low-frequency amplifier circuit, filter 10.7MHz455D is a ceramic filter; Its connection is two filter circuits and IC ₁Connect, antenna is through frequency-selecting and IC ₁Middle High Amplifier Circuit connects, wherein an oscillation circuit and IC ₁Middle mixting circuit connects another oscillation circuit and IC ₁Middle amplifying circuit connects frequency discrimination loop and IC ₁Middle frequency-discriminating circuit connects IC ₁Middle low discharging circuit and the external low mixting circuit IC of putting ₂Connect.

2. by the described earphone of claim 1, it is characterized in that the outer beam of earphone constitutes with rubber sleeve, the centre comprises one section 65Mn steel band, and the steel band two ends are equipped with plastic clip and are associated in the both sides casing, and steel band can slide up and down, to adapt to the head dummy size; Casing is equipped with two joint No.5 cells on one side, and the casing opposite side is equipped with circuit board and antenna, and lead passes from middle rubber sleeve; Casing one side is equipped with power supply/volume switch, and opposite side is equipped with light-emitting diode and band switch, switches to realize multichannel.

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