CN102938747A - Digital interphone signal demodulation device - Google Patents
Digital interphone signal demodulation device Download PDFInfo
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- CN102938747A CN102938747A CN2012104735328A CN201210473532A CN102938747A CN 102938747 A CN102938747 A CN 102938747A CN 2012104735328 A CN2012104735328 A CN 2012104735328A CN 201210473532 A CN201210473532 A CN 201210473532A CN 102938747 A CN102938747 A CN 102938747A
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Abstract
The invention relates to a digital interphone signal demodulation device, relates to the field of signal demodulation and solves problems that demodulation signals are poor in stability and high in distortion degree due to device ageing and temperature changes. The digital interphone signal demodulation device comprises a voltage-controlled oscillator, a mixer, a frequency discriminator and a voltage output module, and the voltage-controlled oscillator produces local oscillation signals according to control levels output by the voltage output module; the mixer mixes the local oscillation signals with radio-frequency signals received by antennas to obtain intermediate frequency signals; the frequency discriminator performs frequency discrimination and demodulation to the intermediate frequency signals and outputs the demodulation signals; and the voltage output module outputs the control levels according to the demodulation signals, calculates direct current components in the demodulation signals and compares calculating results with reference direct current components, and if deviation is larger than a direct current threshold value, the control levels output to the voltage-controlled oscillator are changed till the deviation is smaller than the direct current threshold value. The digital interphone signal demodulation device is used for improving stability of the demodulation signals and reducing the distortion degree of the demodulation signals.
Description
Technical field
The present invention relates to signal demodulation field, be specifically related to a kind of digital handset signal demodulating equipment.
Background technology
For ground specialty wireless intercom system, 2008 to 2013 is the conversion period that simulation transfers numeral to.Will turn to cheaply digital intercom in the most of market of this one-phase, and DPMR is current commercial intercommunication best solution of generally acknowledging.Because DPMR has adopted 4FSK (Frequency-shiftkeying, frequency shift keying) digital modulation and demodulation replaces traditional FM modulation /demodulation, receiver in the part solution adopts the secondary down-conversion, the first local oscillated signal and the second local oscillated signal all are the signals that produces from the reference crystal, so the stability of reference crystal output signal frequency just directly has influence on the performance of whole receiver.Yet corresponding change can occur along with the variation of the objective condition such as time and temperature in the frequency of oscillation of reference crystal, causes the signal DC level after the demodulation unstable, may produce saturatedly under maximum conditions, causes the restituted signal distortion, has improved the error rate.
Existing general processing mode is: the reference crystal oscillator adopts the 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 that offers the reference crystal oscillator is about 1.5V, thereby the reference crystal oscillator produces corresponding frequency, this frequency inputs to phase-locked loop circuit (perhaps phase-locked loop chip), reference frequency point as phase-locked loop, this reference frequency point and voltage controlled oscillator feedback frequency compare, produce phase difference between the two, thereby make the phase discriminator in the phase-locked loop produce corresponding pump current/voltage, the pump current/voltage changes the voltage controlled oscillator frequency through loop low pass filter, thereby the formation feedback loop obtains our the needed first local oscillation frequency point.This local oscillations frequency and antenna reception to radiofrequency signal carry out mixing, obtain intermediate-freuqncy signal, intermediate-freuqncy signal is finally exported to the needed restituted signal of software decode through the frequency discriminator demodulation.
Because reference crystal adopts the temperature complement voltage-control crystal oscillator, when temperature changed between-30 ℃ to 75 ℃, crystal oscillator frequency was changed to 5ppm, and the one-year age that whenever wears out, and crystal oscillator frequency is changed to 2ppm.If long-time the use in different environment, may cause frequency to change 7ppm again.Because reference crystal oscillator frequency changes, so the local oscillations frequency finally causes with regard to respective change 7ppm, the signal DC level after the demodulation changes, and has also increased the distortion factor of restituted signal simultaneously.
Wearing out of the variation of temperature and device belongs to objective fact, is unavoidable.And under different temperatures, use for a long time, can cause the problems referred to above again.So compensation is because the reference crystal frequency change that device aging and variations in temperature produce just seems especially important.
Summary of the invention
Because the reference crystal frequency change that device aging and variations in temperature produce improves the stability of restituted signal, the distortion factor of reduction restituted signal, the present invention proposes a kind of digital handset signal demodulating equipment in order to compensate.
In order to solve the problems of the technologies described above, the invention provides a kind of digital handset signal demodulating equipment, described demodulating equipment comprises voltage controlled oscillator, frequency mixer, frequency discriminator and Voltage-output module,
Described voltage controlled oscillator is used for producing local oscillated signal according to the control level of Voltage-output module output;
Described frequency mixer, be used for local oscillated signal and antenna reception to radiofrequency signal carry out mixing, obtain intermediate-freuqncy signal;
Described frequency discriminator is used for described intermediate-freuqncy signal process demodulation of frequency discriminator, output restituted signal;
Described Voltage-output module, be used for according to described restituted signal output control level, calculate the DC component in the described restituted signal, with result of calculation with compare with reference to DC component, if deviation is greater than the direct current threshold value, then change and output to the control level of described voltage controlled oscillator, until the restituted signal that receives with reference to the deviation of DC component less than the direct current threshold value.
Further, described Voltage-output module comprises DC component computing module and voltage control module,
Described DC component computing module is for the DC component of calculating described restituted signal;
Described voltage control module, be used for the DC component of DC component computing module output with compare with reference to DC component, if deviation is greater than the direct current threshold value, according to DC component and relation with reference to the frequency departure of DC component deviation and voltage controlled oscillator, arrive the level of described voltage controlled oscillator to the direction regulation output of reference DC component, until the restituted signal that receives with reference to the deviation of DC component less than the direct current threshold value, the output level of this moment is input to voltage controlled oscillator as control level; If described deviation is less than the direct current threshold value, the control level that then keeps being input to voltage controlled oscillator is constant.
Further, described Voltage-output module also comprises reference crystal oscillator and phase discriminator,
Described reference crystal oscillator is used for producing reference frequency point according to the level of described voltage control module output;
Described phase discriminator is used for the feedback frequency of described reference frequency point and described voltage controlled oscillator is compared, and according to phase difference between the two, produces the pump current/voltage, and described pump current/voltage is input to voltage controlled oscillator as control level.
Further, the Voltage-output module also comprises low pass filter,
Described low pass filter is used for producing the filtering level according to described pump current/voltage, and described filtering level is input to voltage controlled oscillator as control level.
Further, described low pass filter is loop low pass filter.
Further, described reference crystal oscillator is the temperature complement voltage-control crystal oscillator.
Further, the process that produces the pump current/voltage is: the phase difference that calculates described reference frequency point and described feedback frequency, if described phase difference is greater than phase threshold, relation according to the frequency departure of the phase difference of described reference frequency point and described feedback frequency and voltage controlled oscillator, produce the pump current/voltage, until the phase difference of described reference frequency point and described feedback frequency less than phase threshold, is input to voltage controlled oscillator with pump current/voltage at this moment as control level; If described phase difference is less than phase threshold, the control level that then keeps being input to voltage controlled oscillator is constant.。
Compared with prior art, the present invention passes through the DC level of the signal after the in real time detection demodulation, the corresponding frequencies of computing reference crystal oscillator changes, control voltage by adjusting the reference crystal oscillator after the radio frequency output, the compensate for reference crystal oscillator is because the frequency shift (FS) that environmental change produces, finally obtain the DC level of stable restituted signal, reduce simultaneously the distortion factor of restituted signal.
Description of drawings
Fig. 1 is the structural representation of the digital handset signal demodulating equipment of the embodiment of the invention.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, hereinafter in connection with accompanying drawing embodiments of the invention are elaborated.Need to prove that in the situation of not conflicting, the embodiment among the application and the feature among the embodiment be combination in any mutually.
The embodiment of the invention has proposed a kind of digital handset signal demodulating equipment, the radiofrequency signal that receives by tracking, the control voltage of voltage controlled oscillator 4 is dynamically in real time regulated in the variation of the restituted signal that detection receives, and it is flat to make signal after the demodulation remain on galvanic current.Specific implementation is as follows:
Described voltage controlled oscillator 4 is used for producing local oscillated signal according to the control level of Voltage-output module 7 outputs;
Described frequency mixer 5, be used for local oscillated signal and antenna reception to radiofrequency signal carry out mixing, obtain intermediate-freuqncy signal;
Described frequency discriminator 6 is used for described intermediate-freuqncy signal process demodulation of frequency discriminator, output restituted signal;
Described Voltage-output module 7, be used for according to described restituted signal output control level, calculate the DC component in the described restituted signal, with result of calculation with compare with reference to DC component, if deviation is greater than the direct current threshold value, then change and output to the control level of described voltage controlled oscillator 4, until the restituted signal that receives with reference to the deviation of DC component less than the direct current threshold value.
Wherein, described Voltage-output module 7 comprises DC component computing module 7-1 and voltage control module 7-2,
Described DC component computing module 7-1 is for the DC component of calculating described restituted signal;
Described voltage control module 7-2, be used for the DC component of DC component computing module 7-1 output with compare with reference to DC component, if deviation is greater than the direct current threshold value, according to DC component and relation with reference to the frequency departure of DC component deviation and voltage controlled oscillator 4, arrive the level of described voltage controlled oscillator 4 to the direction regulation output of reference DC component, until the restituted signal that receives with reference to the deviation of DC component less than the direct current threshold value, the output level of this moment is input to voltage controlled oscillator 4 as control level; If described deviation is less than the direct current threshold value, the control level that then keeps being input to voltage controlled oscillator 4 is constant.
Described Voltage-output module 7 can further include reference crystal oscillator 1 and phase discriminator 2, low pass filter 3,
Described reference crystal oscillator 1 is used for producing reference frequency point according to the level of described voltage control module 7-2 output;
Described phase discriminator 2 is used for the feedback frequency of described reference frequency point and described voltage controlled oscillator 4 is compared, and according to phase difference between the two, produces the pump current/voltage.
The process that produces the pump current/voltage is: the phase difference that calculates described reference frequency point and described feedback frequency, if described phase difference is greater than phase threshold, relation according to the frequency departure of the phase difference of described reference frequency point and described feedback frequency and voltage controlled oscillator 4, produce the pump current/voltage, until the phase difference of described reference frequency point and described feedback frequency less than phase threshold, is input to voltage controlled oscillator 4 with pump current/voltage at this moment as control level; If described phase difference is less than phase threshold, the control level that then keeps being input to voltage controlled oscillator 4 is constant.
Described low pass filter 3 is used for producing the filtering level according to described pump current/voltage, and exports described filtering level to described voltage controlled oscillator 4;
Wherein reference crystal oscillator 1 and phase discriminator 2, low pass filter 3 compensate because the variation of the voltage controlled oscillator 4 local oscillated signal frequencies that device aging and variations in temperature produce to a certain extent by the mode of feedback.
Described low pass filter 3 can be loop low pass filter, and described reference crystal oscillator 1 is the temperature complement voltage-control crystal oscillator.
Before carrying out the signal demodulation, need to demarcate digital handset, at first by voltage-regulation reference crystal oscillator 1 output frequency, adjust to the needed frequency of output always, this frequency inputs to phase discriminator 2 as the reference frequency, the signal that feeds back with voltage controlled oscillator 4 carries out the phase bit comparison, because phase place has deviation, so phase discriminator 2 produces the pump current/voltage, regulate voltage controlled oscillator 4 by the low low pass filter of loop, until the frequency of voltage controlled oscillator 4 outputs is stabilized in the frequency that sets in advance.This frequency when receiving, as local oscillator signal and antenna reception to radiofrequency signal utilize frequency mixer 5 to carry out mixing, obtain intermediate-freuqncy signal after the mixing, intermediate-freuqncy signal is passed through frequency discriminator 6 again, demodulates needed restituted signal.
Hardware environment is depended in the setting of voltage control module 7-2 threshold value, for example adopts 10 D/A, and the input voltage interval is the hardware platform of 2V, and then minimum direct current threshold value can be set as 2mV, and Threshold is less, and DC component is with less with reference to the DC component deviation.DC component and with reference to the deviation of DC component, also change simultaneously the size of the voltage of exporting to voltage controlled oscillator 4, proportionate relationship also depends on the external hardware environment, for example detecting DC component and reference component deviation is 10mV, the frequency departure of corresponding voltage controlled oscillator 4 is 150Hz, the frequency proportions of the frequency of reference crystal oscillator 1 and voltage controlled oscillator 4 is 1: 10, then the frequency change of reference crystal oscillator 1 is 15Hz, so inputing to the change in voltage of reference crystal oscillator 1 is 15mV, by this rule adjustment, until the restituted signal that receives with reference to the deviation of DC component less than the direct current threshold value.
This rule is also followed in adjusting for the pump current/voltage.
In individual digital intercom agreement, stipulate, there is the sine wave of 9 600Hz the front as each frame head of setting up communication, so at receiving terminal, the initially signal that receives is the sine wave of 9 600Hz, can be by receiving the sine wave of 9 600Hz, calculate the DC component of current restituted signal, record this DC component as the reference DC component.
The process that embodiment of the invention adjustment is input to the input voltage of voltage controlled oscillator 4 is:
Because the variation of the environmental factors such as variations in temperature and device aging causes the local oscillations frequency to change, the frequency of the radiofrequency signal that perhaps receives is offset.After local oscillated signal and the radiofrequency signal that receives are carried out mixing, the intermediate-freuqncy signal that obtains also can be offset, respective change just occurs through the DC level of the restituted signal of frequency discriminator demodulation output in intermediate-freuqncy signal, and the DC level of the sine wave of 9 600Hz that receive this moment changes too.When receiving the primary sinusoid, calculate the DC component of this moment, result of calculation with compare with reference to DC component, if there is deviation, then by changing the control level of reference crystal oscillator 1, regulate local oscillating frequency, until the restituted signal that receives with reference to the deviation of DC component within the scope of setting, regulate and finish.This moment, whole receiver circuit just formed negative feedback loop, and each conversation can compensate the variation of local oscillated signal and received RF signal.Finally obtain stable restituted signal.
Above embodiment is only unrestricted in order to technical scheme of the present invention to be described, only with reference to preferred embodiment the present invention is had been described in detail.Those of ordinary skill in the art should be appreciated that and can make amendment or be equal to replacement technical scheme of the present invention, and do not break away from the spirit and scope of technical solution of the present invention, all should be encompassed in the middle of the claim scope of the present invention.
Claims (7)
1. digital handset signal demodulating equipment, it is characterized in that: described demodulating equipment comprises voltage controlled oscillator (4), frequency mixer (5), frequency discriminator (6) and Voltage-output module (7),
Described voltage controlled oscillator (4) is used for producing local oscillated signal according to the control level of Voltage-output module (7) output;
Described frequency mixer (5), be used for local oscillated signal and antenna reception to radiofrequency signal carry out mixing, obtain intermediate-freuqncy signal;
Described frequency discriminator (6) is used for described intermediate-freuqncy signal process demodulation of frequency discriminator, output restituted signal;
Described Voltage-output module (7), be used for according to described restituted signal output control level, calculate the DC component in the described restituted signal, with result of calculation with compare with reference to DC component, if deviation is greater than the direct current threshold value, then change and output to the control level of described voltage controlled oscillator (4), until the restituted signal that receives with reference to the deviation of DC component less than the direct current threshold value.
2. decoding circuit as claimed in claim 1, it is characterized in that: described Voltage-output module (7) comprises DC component computing module (7-1) and voltage control module (7-2),
Described DC component computing module (7-1) is for the DC component of calculating described restituted signal;
Described voltage control module (7-2), be used for the DC component of DC component computing module (7-1) output with compare with reference to DC component, if deviation is greater than the direct current threshold value, according to DC component and relation with reference to the frequency departure of DC component deviation and voltage controlled oscillator (4), arrive the level of described voltage controlled oscillator (4) to the direction regulation output of reference DC component, until the restituted signal that receives with reference to the deviation of DC component less than the direct current threshold value, the output level of this moment is input to voltage controlled oscillator (4) as control level; If described deviation is less than the direct current threshold value, the control level that then keeps being input to voltage controlled oscillator (4) is constant.
3. decoding circuit as claimed in claim 2, it is characterized in that: described Voltage-output module (7) also comprises reference crystal oscillator (1) and phase discriminator (2),
Described reference crystal oscillator (1) is used for producing reference frequency point according to the level of described voltage control module (7-2) output;
Described phase discriminator (2), be used for the feedback frequency of described reference frequency point and described voltage controlled oscillator (4) is compared, according to phase difference between the two, produce the pump current/voltage, and described pump current/voltage is input to voltage controlled oscillator (4) as control level.
4. decoding circuit as claimed in claim 3, it is characterized in that: Voltage-output module (7) also comprises low pass filter (3),
Described low pass filter (3) is used for producing the filtering level according to described pump current/voltage, and described filtering level is input to voltage controlled oscillator (4) as control level.
5. decoding circuit as claimed in claim 4, it is characterized in that: described low pass filter (3) is loop low pass filter.
6. decoding circuit as claimed in claim 3, it is characterized in that: described reference crystal oscillator (1) is the temperature complement voltage-control crystal oscillator.
7. decoding circuit as claimed in claim 3, it is characterized in that: the process that produces the pump current/voltage is: the phase difference that calculates described reference frequency point and described feedback frequency, if described phase difference is greater than phase threshold, relation according to the frequency departure of the phase difference of described reference frequency point and described feedback frequency and voltage controlled oscillator (4), produce the pump current/voltage, until the phase difference of described reference frequency point and described feedback frequency less than phase threshold, is input to voltage controlled oscillator (4) with pump current/voltage at this moment as control level; If described phase difference is less than phase threshold, the control level that then keeps being input to voltage controlled oscillator (4) is constant.
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| CN201210473532.8A CN102938747B (en) | 2012-11-20 | 2012-11-20 | A kind of digital interphone signal demodulation device |
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| CN201210473532.8A CN102938747B (en) | 2012-11-20 | 2012-11-20 | A kind of digital interphone signal demodulation device |
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| CN102938747B CN102938747B (en) | 2016-01-20 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105898163A (en) * | 2016-06-20 | 2016-08-24 | 深圳创维数字技术有限公司 | Television signal frequency deviation processing method and system |
| CN106227031A (en) * | 2016-05-25 | 2016-12-14 | 广州市国飞信息科技有限公司 | A kind of receiver module and single-chip realize satellite and tame and punctual method |
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| CN1845542A (en) * | 2005-04-08 | 2006-10-11 | 美国博通公司 | Signal processing method and system |
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| US20050052261A1 (en) * | 2003-09-09 | 2005-03-10 | Samsung Electronics Co., Ltd. | Thin film resonator, method for making thin film resonator and filter having thin film resonators |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106227031A (en) * | 2016-05-25 | 2016-12-14 | 广州市国飞信息科技有限公司 | A kind of receiver module and single-chip realize satellite and tame and punctual method |
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| CN102938747B (en) | 2016-01-20 |
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