CN103166889B - A kind of digital interphone signal demodulation device and chip - Google Patents
A kind of digital interphone signal demodulation device and chip Download PDFInfo
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- CN103166889B CN103166889B CN201310097148.7A CN201310097148A CN103166889B CN 103166889 B CN103166889 B CN 103166889B CN 201310097148 A CN201310097148 A CN 201310097148A CN 103166889 B CN103166889 B CN 103166889B
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Abstract
A kind of digital interphone signal demodulation device and chip, relate to signal receiving field, in order to process the problem of the frequency skew of local oscillations, improve the stability of restituted signal, reduce the distortion factor of restituted signal, described demodulating equipment, comprise baseband chip, phase-locked loop, frequency mixer, frequency discriminator and single-ended transfer difference module, the radiofrequency signal local oscillated signal of generation and antenna received carries out mixing, obtains intermediate-freuqncy signal; Through demodulation of frequency discriminator, export restituted signal; Carry out differential conversion, obtain two-way intermediate-freuqncy signal differential signal; Described baseband chip, the DC component in described restituted signal is calculated according to described two-way intermediate-freuqncy signal differential signal, result of calculation is compared with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then change the reference level outputting to described single-ended transfer difference module, until the DC component of the restituted signal calculated is less than direct current threshold value with the deviation with reference to DC component.
Description
Technical field
The present invention relates to signal receiving field, be specifically related to a kind of digital interphone signal demodulation device and chip.
Background technology
For ground specialty wireless intercom system, within 3 years in future, transfer digital conversion period to by welcoming simulation.Will turn to the digital intercom of low cost in this one-phase major part market, and digital wireless communication agreement DPMR is current business intercommunication best solution of generally acknowledging.Because DPMR have employed 4FSK (Frequency-shiftkeying, frequency shift keying) digital modulation and demodulation replaces traditional FM modulation /demodulation, but corresponding change can be there is along with the change of the objective condition such as time and temperature in the local oscillated signal of radio circuit, cause the signal DC level after demodulation unstable, general baseband chip adopts Differential Input simultaneously, therefore the signal demand after demodulation obtains differential signal by single-ended transfer difference circuit, so when restituted signal DC level changes, single-ended transfer difference signal also changes simultaneously, the differential input signal DC level of baseband chip is caused to offset, single-ended transfer difference circuit can be caused under extreme conditions saturated, and then make restituted signal distortion, increase the error rate.
Existing general processing mode is: reference crystal oscillator adopts temperature complement voltage-control crystal oscillator, and this crystal can compensate the frequency change that a part of Yin Wendu causes, but compensation range is limited.The reference level being supplied to reference crystal oscillator is about 1.5V, thus reference crystal oscillator produces corresponding frequency, this frequency inputs to phase-locked loop circuit (or phase-locked loop chip), as the reference frequency point of phase-locked loop, this reference frequency point and voltage controlled oscillator feed back frequency and compare, produce phase difference between the two, thus make the phase discriminator in phase-locked loop create corresponding pump current/voltage, pump current/voltage changes voltage controlled oscillator frequency through loop low pass filter, thus formation feedback loop, obtain the first required local oscillation frequency point.The radiofrequency signal that this local oscillations frequency and antenna receive carries out mixing, obtains intermediate-freuqncy signal, and intermediate-freuqncy signal is through frequency discriminator demodulation, and the signal after demodulation is through single-ended transfer difference circuit, and final differential signal exports to the restituted signal required for software decode.
Because reference crystal adopts temperature complement voltage-control crystal oscillator, when temperature changes between-30 DEG C to 75 DEG C, crystal oscillator frequency is changed to 5ppm, and every aging one-year age, and crystal oscillator frequency is changed to 2ppm.If used for a long time, again in different environment, frequency may be caused to change 7ppm.Because reference crystal oscillator frequency changes, so local oscillations frequency is with regard to respective change 7ppm, signal DC level after demodulation changes, then the input direct-current component of single-ended transfer difference circuit changes, under extreme conditions, single-ended transfer difference input signal may be caused saturated, thus cause outputing signal serious distortion, ultimately increase the error rate.
When individual digital intercom is in accepting state, the change of the environmental factor such as variations in temperature and device aging can cause local oscillations frequency to change, or when skew occurs the frequency of the radiofrequency signal received.After then local oscillated signal and the radiofrequency signal received carry out mixing, the intermediate-freuqncy signal obtained also can offset, just respective change is there is in intermediate-freuqncy signal through the DC level of the restituted signal that frequency discriminator demodulation exports, the DC component of restituted signal can change, through single-ended transfer difference circuit, the differential signal obtained thus also change, then the DC component generation respective change of the restituted signal collected of baseband chip.
The change of temperature and the aging of device, belong to objective fact, is unavoidable.And use at different temperatures for a long time, can the problems referred to above be caused again.So compensate the reference crystal frequency change because device aging and variations in temperature produce, just seem especially important.
Summary of the invention
In order to process the problem of the frequency skew of local oscillations, improve the stability of restituted signal, reduce the distortion factor of restituted signal, the present invention proposes a kind of digital interphone signal demodulation device and chip.
In order to solve the problems of the technologies described above, the invention provides a kind of digital interphone signal demodulation device, comprise baseband chip, phase-locked loop, frequency mixer, frequency discriminator and single-ended transfer difference module,
Described phase-locked loop, for generation of local oscillated signal;
Described frequency mixer, carries out mixing for radiofrequency signal local oscillated signal and antenna received, obtains intermediate-freuqncy signal;
Described frequency discriminator, for described intermediate-freuqncy signal through demodulation of frequency discriminator, export restituted signal;
Described single-ended transfer difference module, carries out differential conversion for the reference level exported according to baseband chip to restituted signal, obtains two-way intermediate-freuqncy signal differential signal;
Described baseband chip, for calculating the DC component in described restituted signal according to described two-way intermediate-freuqncy signal differential signal, result of calculation is compared with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then change the reference level outputting to described single-ended transfer difference module, until the DC component of the restituted signal calculated is less than direct current threshold value with the deviation with reference to DC component.
Further, described baseband chip comprises DC component computing module and voltage control module,
Described DC component computing module, for calculating the DC component in described restituted signal;
Described voltage control module, DC component for being exported by DC component computing module compares with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then according to this deviation and the relation by described two-way intermediate-freuqncy signal differential signal, to the level of the direction regulation output to described single-ended transfer difference module that reduce input direct-current component and reference DC component deviation, until the DC component of the restituted signal received is less than or equal to direct current threshold value with the deviation with reference to DC component, output level is now input to single-ended transfer difference module as reference level, if described deviation is less than or equal to direct current threshold value, then keep the level being input to single-ended transfer difference module constant.
Further, single-ended transfer difference module is operational amplifier chip.
In order to solve the problems of the technologies described above, present invention also offers a kind of digital handset signal baseband chip, described baseband chip, DC component is calculated according to the two paths of differential signals received, result of calculation is compared with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then change the reference level of output, until the DC component calculated is less than direct current threshold value with the deviation with reference to DC component.
Further, described baseband chip comprises DC component computing module and voltage control module,
Described DC component computing module calculates the DC component of the two paths of differential signals received;
The DC component that DC component computing module exports by described voltage control module compares with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then according to this deviation and the relation by described two paths of differential signals, to the reference level reducing input direct-current component and the direction regulation output with reference to DC component deviation, until the DC component received is less than or equal to direct current threshold value with the deviation with reference to DC component, if described deviation is less than or equal to direct current threshold value, then keep the level of output constant.
Compared with prior art, the present invention is by detecting the DC level of the signal after demodulation in real time, according to the relation of DC level change with intermediate-freuqncy signal differential signal, adjustment outputs to the level of single-ended transfer difference module, compensate single-ended transfer difference module because the skew of environmental change generation, finally obtain the DC level of stable restituted signal, reduce the distortion factor of restituted signal simultaneously.
Accompanying drawing explanation
Fig. 1 is the structural representation of the digital interphone signal demodulation device of the embodiment of the present invention.
Embodiment
For making the object, technical solutions and advantages of the present invention clearly understand, hereinafter will be described in detail to embodiments of the invention by reference to the accompanying drawings.It should be noted that, when not conflicting, the embodiment in the application and the feature in embodiment can combination in any mutually.
The embodiment of the present invention is by detecting the change of the restituted signal received, and dynamic realtime regulates the reference level value of single-ended transfer difference module 7, thus obtains stable differential signal input baseband chip 1.Concrete mode is as follows:
As shown in Figure 1, the digital interphone signal demodulation device of the embodiment of the present invention comprises baseband chip 1, phase-locked loop 4, frequency mixer 5, frequency discriminator 6 and single-ended transfer difference module 7,
Described phase-locked loop 4, for generation of local oscillated signal;
Described frequency mixer 5, carries out mixing for radiofrequency signal local oscillated signal and antenna received, obtains intermediate-freuqncy signal;
Described frequency discriminator 6, for described intermediate-freuqncy signal through demodulation of frequency discriminator, export restituted signal;
Described single-ended transfer difference module 7, carries out differential conversion for the reference level exported according to baseband chip 1 to restituted signal, obtains two-way intermediate-freuqncy signal differential signal;
Described baseband chip 1, for calculating the DC component in described restituted signal according to described two-way intermediate-freuqncy signal differential signal, result of calculation is compared with reference to DC component, if deviation is greater than direct current threshold value, then change the reference level outputting to described single-ended transfer difference module 7, until the DC component of the restituted signal received is less than direct current threshold value with the deviation with reference to DC component.
Wherein, described baseband chip 1 comprises DC component computing module 2 and voltage control module 3,
Described DC component computing module 2, for calculating the DC component in described restituted signal;
Described voltage control module 3, DC component for being exported by DC component computing module 2 compares with reference to DC component, if deviation is greater than direct current threshold value, according to DC component and reference DC component deviation and the relation by described two-way intermediate-freuqncy signal differential signal, to the direction regulation output with reference to DC component to the level of described single-ended transfer difference module 7, until the DC component of the restituted signal received is less than direct current threshold value with the deviation with reference to DC component, output level is now input to single-ended transfer difference module 7 as reference level; If described deviation is less than direct current threshold value, then keep the level being input to single-ended transfer difference module 7 constant.
When the difference that DC component deducts reference DC component is greater than threshold value, to the level of the direction regulation output to described single-ended transfer difference module 7 that reduce DC component;
When the difference deducting DC component with reference to DC component is greater than threshold value, to the level of the direction regulation output to described single-ended transfer difference module 7 that increase DC component, the figure place of the A/D converter outputting to single-ended transfer difference module 7 is depended in the setting of step-length, if A/D is 10, the amplitude of accommodation is 3V, then step-length is 3mV.In other embodiments, the figure place of A/D converter can adopt other value, and the corresponding step-length that regulates can be set as other values as required.
Wherein, single-ended transfer difference module 7 is operational amplifier chip.
Suppose that the scope of baseband chip 1 Differential Input is 1V-2V, first by regulating the reference level of single-ended transfer difference module 7 input, obtain the differential signal that DC component is all 1.5V, differential signal is inputted baseband chip 1, measure the value that the DC component of the restituted signal that now baseband signal collects is corresponding, this value is set as with reference to DC component α.
The process that embodiment of the present invention adjustment is input to the input voltage of single-ended transfer difference module 7 is:
Specify according in individual digital intercom agreement, each communication can send the sine wave of 9 600Hz as each frame head setting up communication, so at receiving terminal, the initially signal received is the sine wave of 9 600Hz, can by receiving the sine wave of 9 600Hz, the DC component calculating current restituted signal is β, regulates direct current threshold value to be Δ.In time receiving the primary sinusoid, the DC component β calculated now compares with reference to DC component α, if | alpha-beta | > Δ, then baseband chip 1 is by regulating the reference level of single-ended transfer difference module 7, regulate local oscillating frequency, until the restituted signal received and the deviation with reference to DC component α are within the scope set, regulate and terminate.Now whole receiver circuit just forms negative feedback loop, and each call can compensate the change of local oscillated signal and received RF signal.Finally obtain stable restituted signal.
Wherein, the precision of baseband chip A/D converter is depended in the setting of direct current threshold value Δ, if adopt the A/D converter of 10, input range is 1V, when then tolerance is set to 1bit, corresponding direct current threshold value is that Δ is about 1mV, then restituted signal level Adjustment precision is about 1mV.In other embodiments, the figure place of A/D converter can adopt other value, and corresponding direct current threshold value can be set as other values as required.
Above embodiment only in order to technical scheme of the present invention and unrestricted to be described, only with reference to preferred embodiment to invention has been detailed description.Those of ordinary skill in the art should be appreciated that and can modify to technical scheme of the present invention or equivalent replacement, and does not depart from the spirit and scope of technical solution of the present invention, all should be encompassed in the middle of right of the present invention.
Claims (5)
1. a digital interphone signal demodulation device, it is characterized in that: described demodulating equipment comprises baseband chip (1), phase-locked loop (4), frequency mixer (5), frequency discriminator (6) and single-ended transfer difference module (7)
Described phase-locked loop (4), for generation of local oscillated signal;
Described frequency mixer (5), carries out mixing for radiofrequency signal local oscillated signal and antenna received, obtains intermediate-freuqncy signal;
Described frequency discriminator (6), for described intermediate-freuqncy signal through demodulation of frequency discriminator, export restituted signal;
Described single-ended transfer difference module (7), carries out differential conversion for the reference level exported according to baseband chip (1) to restituted signal, obtains two-way intermediate-freuqncy signal differential signal;
Described baseband chip (1), for calculating the DC component in described restituted signal according to described two-way intermediate-freuqncy signal differential signal, result of calculation is compared with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then change the reference level outputting to described single-ended transfer difference module (7), until the DC component of the restituted signal calculated is less than direct current threshold value with the deviation with reference to DC component.
2. demodulating equipment as claimed in claim 1, is characterized in that: described baseband chip (1) comprises DC component computing module (2) and voltage control module (3),
Described DC component computing module (2), for calculating the DC component in described restituted signal;
Described voltage control module (3), DC component for being exported by DC component computing module (2) compares with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then according to this deviation and the relation by described two-way intermediate-freuqncy signal differential signal, to the level of the direction regulation output to described single-ended transfer difference module (7) that reduce input direct-current component and reference DC component deviation, until the DC component of the restituted signal received is less than or equal to direct current threshold value with the deviation with reference to DC component, output level is now input to single-ended transfer difference module (7) as reference level, if described deviation is less than or equal to direct current threshold value, then keep the level being input to single-ended transfer difference module (7) constant.
3. demodulating equipment as claimed in claim 1, is characterized in that: single-ended transfer difference module (7) is operational amplifier chip.
4. a digital handset signal baseband chip, it is characterized in that: described baseband chip, DC component is calculated according to the two paths of differential signals received, result of calculation is compared with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then change the reference level of output, until the DC component calculated is less than direct current threshold value with the deviation with reference to DC component.
5. baseband chip according to claim 4, is characterized in that: described baseband chip comprises DC component computing module and voltage control module,
Described DC component computing module calculates the DC component of the two paths of differential signals received;
The DC component that DC component computing module exports by described voltage control module compares with reference to DC component, if DC component is greater than direct current threshold value with the deviation with reference to DC component, then according to this deviation and the relation by described two paths of differential signals, to the reference level reducing input direct-current component and the direction regulation output with reference to DC component deviation, until the DC component received is less than or equal to direct current threshold value with the deviation with reference to DC component, if described deviation is less than or equal to direct current threshold value, then keep the level of output constant.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011026290A1 (en) * | 2009-09-02 | 2011-03-10 | 中兴通讯股份有限公司 | Differential reception system in a cellular receiver and method for realizing signal reception thereof |
| CN202515663U (en) * | 2012-02-17 | 2012-11-07 | 深圳市杰纳瑞医疗仪器有限公司 | Direct-current drifting automatic balance system for impedance breathing detection |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011026290A1 (en) * | 2009-09-02 | 2011-03-10 | 中兴通讯股份有限公司 | Differential reception system in a cellular receiver and method for realizing signal reception thereof |
| CN202515663U (en) * | 2012-02-17 | 2012-11-07 | 深圳市杰纳瑞医疗仪器有限公司 | Direct-current drifting automatic balance system for impedance breathing detection |
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