CN101312352B

CN101312352B - Common control circuit for audio signal wire and frequency modulation antenna

Info

Publication number: CN101312352B
Application number: CN 200710074597
Authority: CN
Inventors: 李景林
Original assignee: Shenzhen ZTE Mobile Telecom Co Ltd
Current assignee: Nubia Technology Co Ltd
Priority date: 2007-05-25
Filing date: 2007-05-25
Publication date: 2012-12-26
Anticipated expiration: 2027-05-25
Also published as: CN101312352A

Abstract

The invention discloses a control circuit for an audio frequency signal wire and a frequency-modulated antenna, which comprises an antenna port circuit of a frequency-modulated receiver and an audio frequency signal wire circuit of a wireless controller. In the antenna port circuit of a frequency-modulated receiver, a ceramic capacitor is disposed between a radio-frequency signal input and an oscillatory circuit. In the audio frequency signal wire circuit of a wireless controller, a bead is disposed at the front end of a filter circuit in a second audio frequency signal wire. The second audio frequency signal wire at the front end of the bead is connected with a radio-frequency signal output. The radio-frequency signal output in the audio frequency signal wire circuit of a wireless controller is connected with the radio-frequency signal input of the antenna port circuit of a frequency-modulated antenna. The control circuit realizes that an audio frequency signal wire not only can be used as an antenna of a frequency-modulated receiver, but maintain the prior audio frequency functions, thereby reducing cost and further beautifying a wireless fixed terminal.

Description

The control circuit that a kind of audio signal wire and frequency-modulated antenna are shared

Technical field

The present invention relates to wireless terminal, related in particular to wireless terminals such as the FWT (fixed wireless terminal, wireless fixed terminal) of FM (frequency modulation, frequency modulation) radio function, mobile phone integrated.

Background technology

At present, because the wireless chip of FM is highly integrated, can be made in the chip piece, the wireless function of integrated FM has become a kind of fashion on various wireless terminals.

The used frequency range of FM broadcast receiver is 76～108MHz.When frequency range was 100MHz, antenna length needed 0.75 meter; When frequency range was 80MHz, antenna length reached 0.9375 meter especially.And the employed frequency range of wireless terminal is a kind of among 450MHz, 800MHz, 900MHz, 1800MHz, the 1900MHz, and its antenna is all very short.Because frequency range is different, obviously the wireless antenna of FM be can not sharing wireless terminal antenna.Therefore on wireless terminal, find single line to make the wireless antenna of FM in addition.

At present, adopt following method usually:

For FWT, when its integrated FM radio function, owing to be to export the wireless sound of FM mainly, therefore can draw single line separately from the FWT and use as the wireless antenna of FM with the hands-free loudspeaker on the FWT.

This method owing to increased single line, has not only influenced the attractive in appearance of FWT, and has increased cost.

For mobile phone, when its integrated FM radio function,, therefore can from earphone, draw single line more separately as the wireless antenna use of FM owing to mainly be to listen to the FM broadcast receiver with earphone in addition.

This method has also increased the cost of earphone.

Summary of the invention

Technical problem to be solved by this invention provides a kind of audio signal wire and the shared control circuit of frequency-modulated antenna, and not needing increases antenna on FWT or earphone, reduce cost.

For solving the problems of the technologies described above, the present invention realizes through following technical scheme:

The control circuit that a kind of audio signal wire and frequency-modulated antenna are shared comprises the antenna interface circuit and the handle audio signal line circuit of FM receiver;

The antenna interface circuit of said FM receiver comprises RF signal input end mouth FM_ANTENNA1, oscillating circuit, FM radio machine chip FM Circuit, audio output port Audio Output, and four are chained together successively;

Said handle audio signal line circuit comprises audio signal wire 1, audio signal wire 2, is connected with filter network between the two, and filter network comprises C17, C72, C19, C68, C28, C69, and audio signal wire 2 can be done the holding wire of virtual earth;

In the said FM receiver antenna interface circuit, also comprise a ceramic condenser C139 between RF signal input end mouth FM_ANTENNA1 and the oscillating circuit;

In the said handle audio signal line circuit, on audio signal wire 2, the filter circuit front end also comprises a magnetic bead L15;

On the audio signal wire 2 of said magnetic bead front end, also be connected with radiofrequency signal output port FM_ANTENNA2;

Radiofrequency signal output port FM_ANTENNA2 in the handle audio signal line circuit is connected with the RF signal input end mouth FM_ANTENNA1 of FM receiver antenna interface circuit.

Wherein, in the said handle audio signal line circuit, all be connected in series an identical magnetic bead on other audio signal wire.

Wherein, said ceramic condenser C139 is 100PF.

The present invention has following beneficial effect:

1) through increasing simple circuit, realized that audio signal wire can make the wireless antenna of FM, can keep the function of its original audio frequency effect again.

2) owing to need not increase antenna, reduced cost.

3), increased the attractive in appearance of FWT for the terminal of FWT and so on.

Description of drawings

Fig. 1 is FM radio antenna interface circuit schematic diagram among the present invention;

Fig. 2 is handle audio signal wire circuit theory diagrams among the present invention;

Fig. 3 is the FM radio antenna interface circuit schematic diagram of the embodiment of the invention;

Embodiment

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

The present invention realizes with audio signal wire as the wireless radio-frequency antenna of FM through simple circuit, and keeps original audio-frequency function, circuit to comprise FM radio antenna interface circuit and handle audio signal line circuit two parts.

As shown in Figure 1; FM radio antenna interface circuit comprises RF signal input end mouth FM_ANTENNA1, oscillating circuit, FM radio machine chip FM Circuit, audio output port Audio Output; Four are chained together successively, also comprise a ceramic condenser C139 between RF signal input end mouth FM_ANTENNA1 and the oscillating circuit, and this electric capacity is used to intercept audio signal; Audio signal can not leaked on the spot, and do not influence passing through of radiofrequency signal.

As shown in Figure 2; Handle audio signal line circuit comprises audio signal wire 1, audio signal wire 2; Be connected with filter network between the two; The right-hand member of audio signal wire 1 and audio signal wire 2 is connected source of sound electrode input end MICIP and source of sound negative input MICIN respectively, connects audiogenic device between this two-stage input; And on the audio signal wire that can do virtual earth 2, the filter circuit front end also comprises a magnetic bead L15, and this magnetic bead is used for radiofrequency signal is attenuated, and does not influence passing through of audio signal.

Shown in Figure 3 is one embodiment of the present of invention; The FM broadcast receiver chip that adopts is the Si4700 that the research and development of Silicom company are produced; This is the integrated FM broadcast receiver chip of a height, and the frequency range of its support is 76MHz～108MHz, interior band frequency synthesizer, automatic frequency control (AFC), automatic gain control (AGC); And its control simple and flexible, can adopt two wires or three-way mode with software interface.In order to adapt to low power supply power supply, its inside has also carried a LDO (Low-dropout regulator, low pressure differential calibration output).The FM_LOUT end is three-dimensional sound left side passage among this figure, and FM_ROUT is the right passage of three-dimensional sound, and FM_MONO is a single channel.

During circuit working; In the audio signal line circuit, select the audio signal wire that to do virtual earth as the wireless radio-frequency antenna of FM; As shown in Figure 2; Present embodiment is selected audio signal wire 2 for use, and the radiofrequency signal output port FM_ANTENNA1 of audio signal line circuit is connected with the RF signal input end mouth FM_ANTENNA2 of radio antenna interface circuit.

When the FM radio function is opened; Radiofrequency signal gets into RF signal input end mouth FM_ANTENNA2 from audio signal 2; And inflow broadcast receiver chip reaches function of radio receiver; But this moment, audio signal also can leak on the spot through inductance L 4, made that the microphone (Microphone) on the handle can not sent out sound, promptly can not realize the call function of handle.Thereby the present invention has increased a capacitor C 139:100PF before oscillating circuit; Because this electric capacity is less, and range of audio signals is 300Hz～3400Hz, is low frequency; Therefore can enough audio signal be separated, make audio signal be unlikely to leak on the spot through L4; Simultaneously again because the wireless radiofrequency signal scope of FM is higher, up to 76MHz～108MHz, so this electric capacity do not influence passing through of the wireless radiofrequency signal of FM again, realized the needed antenna function of FM broadcast receiver.

Generally, Microphone is last to have a filter network, is used for elimination common mode noise and wireless noise, and this network is made up of C17, C72, C19, C68, C28, C69, and is as shown in Figure 2.If this filter network is directly received the FM radio antenna, then the radiofrequency signal on the antenna can leak into ground through this network, makes the wireless function of FM realize not.In addition, radiofrequency signal can be that MIC1N goes here and there into through voice-grade channel also, causes the phenomenon that very big white noise is arranged in the communication process.Thereby the present invention has been connected in series a magnetic bead L15:BLM11B102S at the front end of MIC1N, and the characteristic of this magnetic bead is impedance: 1000 Ω ± 25% (100MHz0.1V), when promptly signal was near the 100MHz frequency, its impedance was up to 1000 Ω ± 25%.At this moment, as the wireless radiofrequency signal of FM (76MHz～when 108MHz) coming in, can run into very big impedance so that be attenuated, and audio signal can not received influence, because the frequency of audio signal is very low, is 300Hz～3400Hz, can pass through fully.And because this magnetic bead is placed on the front that filter network is C17, C72, C19, C68, C28, C69, radiofrequency signal can not leak into ground from filter network, has realized the wireless function of FM.

In practical application,, there is the possibility of audio frequency coupling each other because that four audio signal wires on the handle paste is too near; It is crosstalk phenomenon; The audio signal wire that the wireless radiofrequency signal of FM still possibly be crosstalked into other gets on, so the present invention all has been connected in series a same magnetic bead on each root holding wire, like the L16:BLM11B102S among Fig. 2; But the elimination white noise, and do not disturb normal audio communication.

The above is merely preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of within spirit of the present invention and principle, being done, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.

Claims

1. audio signal wire and the shared control circuit of frequency-modulated antenna comprise the antenna interface circuit and the handle audio signal line circuit of FM receiver;

The antenna interface circuit of said FM receiver comprises RF signal input end mouth (FM_ANTENNA1), oscillating circuit, FM radio machine chip (FM Circuit), audio output port (Audio Output), and four are chained together successively;

Said handle audio signal line circuit comprises audio signal wire one (1), audio signal wire two (2); Be connected with filter network between the two; Filter network comprises filter capacitor C17, ceramic condenser C72, filter capacitor C19, filter capacitor C68, ceramic condenser C28 and filter capacitor C69, and audio signal wire two (2) is done the holding wire of virtual earth;

It is characterized in that: in the said FM receiver antenna interface circuit, also comprise a ceramic condenser C139 between RF signal input end mouth (FM_ANTENNA1) and the oscillating circuit; Said ceramic condenser C139 is 100PF;

In the said handle audio signal line circuit; On audio signal wire two (2), the filter circuit front end also comprises a magnetic bead L15, and the characteristic of this magnetic bead is impedance: 1000 Ω ± 25% (100MHz 0.1V); Signal is near the 100MHz frequency time, and its impedance is up to 1000 Ω ± 25%;

On the audio signal wire two (2) of said magnetic bead front end, also be connected with radiofrequency signal output port (FM_ANTENNA2);

Radiofrequency signal output port (FM_ANTENNA2) in the handle audio signal line circuit is connected with the RF signal input end mouth (FM_ANTENNA1) of FM receiver antenna interface circuit.

2. audio signal wire as claimed in claim 1 and the shared control circuit of frequency-modulated antenna is characterized in that, in the said handle audio signal line circuit, all are connected in series an identical magnetic bead on other audio signal wire.