CN101183877B - DC offset calibration method and apparatus - Google Patents
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Abstract
本发明公开了一种直流偏移校准方法，该方法包括：根据数字信号接收的时间点位置选择进行偏移量获取处理或校准处理；偏移量获得处理，通过使射频输入信号为零来获得直流偏移量；校准处理，根据获得的直流偏移量来对接收的数字信号进行校准。此外，本发明还公开了一种直流偏移校准装置。通过使用本发明，能够在不增加额外的复杂的模拟电路且不影响基站的正常业务情况下，实时跟踪并校准由于温度变化以及电路参数等变化而引起的直流偏移分量的变化，并且还具有实现简单的优点。
The invention discloses a method for calibrating DC offset, which includes: selecting and performing offset acquisition processing or calibration processing according to the time point position of digital signal reception; the offset acquisition processing is obtained by making the radio frequency input signal zero DC offset; calibration processing, the received digital signal is calibrated according to the obtained DC offset. In addition, the invention also discloses a DC offset calibration device. By using the present invention, it is possible to track and calibrate changes in DC offset components caused by changes in temperature and circuit parameters in real time without adding additional complex analog circuits and without affecting the normal business of the base station, and also has The advantage of simplicity is achieved.
Description
Technical field
The present invention relates to the communications field, and especially, relate to a kind of DC offset calibration method and device.
Background technology
The zero intermediate frequency technology is that it has only adopted single-conversion for traditional double conversion technology.At radiating portion, digital inphase quadrature (IQ) signal after the mapping becomes orthogonal simulation IQ signal through DAC (Digital-to-Analog Conventer, digital to analog converter), then directly is modulated to radio frequency, not by the intermediate frequency filtering part; At receiving unit, use a frequency mixer, directly will change to the analog I/Q signal with interior radiofrequency signal, then pass through ADC (Analog-to-Digital Conventer, analog to digital converter) becomes digital IQ signal, carry out again afterwards the digital base band processors such as demodulating and decoding.
The zero intermediate frequency technology mainly contains with following advantage with respect to traditional double conversion technology: (1) is with respect to traditional double conversion scheme, save intermediate frequency filtering circuit, intermediate frequency mixer and intermediate frequency local oscillator, simplify passage, reduced the cost of passage, dwindled area; (2) with respect to present popular high intermediate frequency scheme, can save digital frequency converter and high-speed AD, reduce the requirement to the numerical portion circuit; (3) because zero intermediate frequency scheme does not need digital sample clock at a high speed, thus digital circuit can be reduced to the impact of radio frequency, and for radio circuit, both are more or less the same, all need to be by local oscillator and frequency mixer (directly modulator); (4) because the zero intermediate frequency technology directly is converted to base band by radio frequency, so also just do not have the problem of image signal.
Be not difficult to find out that from cost and volume and realization difficulty, zero intermediate frequency scheme all more has superiority.
But zero intermediate frequency scheme also has the inevitable problem of himself.Mainly be to have carrier leak and suppress sideband problem at transmitting terminal; Mainly be DC offset problem at receiving terminal.Wherein, in zero intermediate frequency reciver, the generation of direct current signal mainly contains following three reasons: the intrinsic DC component that (1) modulation signal produces (for example, Manchester code), this component is useful direct current signal, does not belong to the direct current offset part, therefore needs protection; (2) because the frequency of the carrier signal of local oscillation signal and receiving terminal is identical, can cause local oscillation signal to leak into the input of receiver, thereby form the certainly mixed of local oscillation signal, produce larger direct current signal, this direct current signal is the main cause of zero intermediate frequency reciver direct current offset; (3) circuit itself is owing to the asymmetric common mode direct current offset that causes of mixer output, and this also is a reason of zero intermediate frequency reciver direct current offset.
The direct current offset of zero intermediate frequency reciver can produce larger impact to whole receiver, particularly when receiving small-signal, so must calibrate this direct current offset.
Traditional method is to come every straight (filtering) with a large electric capacity, but this needs larger electric capacity, be difficult to integrated, and this method can produce larger distortion, approximately be the 100us level settling time, so settling time is very long, and a GSM base station conventional burst (Normal Burst) only has 577us, so this method more is not suitable for being used on the GSM base station.
Application number is 200510136595.4, title has proposed a kind of method and circuit that solves the zero intermediate frequency reciver direct current offset in the patent application of " a kind of method and circuit that solves the zero intermediate frequency reciver direct current offset ".Wherein, frequency mixer at receiver uses the principle realization of analog feedback to the inhibition of direct current offset, utilize a differential mode feedback network to eliminate the differential mode direct current offset, and utilize the common-mode feedback network to suppress the asymmetric common mode direct current offset that causes of mixer output, the process of the direct current offset calibration of this scheme realizes with analog circuit.The advantage of this method is that real-time performance is relatively good, can follow the tracks of because the variation of the direct-flow offset weight that variations in temperature causes, its shortcoming is not mask the intrinsic DC component that modulation signal produces, differ surely and to follow the tracks of owing to can direct current offset that circuit parameter variations causes (be followed the tracks of and the frequency of DC offset change has relation, namely the frequency of circuit parameter variations has relation), and the extra analog circuit that increases can reduce the linearity, thereby affect gain and the noise of receiver, and the circuit more complicated of this scheme.
In patent 99800691.2 (title is " DC-offset compensation of Zero-IF demodulator device "), provide a kind of DC-offset compensation circuit.This scheme is at first introduced a frequency shift (FS) in local oscillator, in order to (for example mask the intrinsic DC component of the bad student of institute from modulation signal, Manchester code), only extract differential mode direct current offset and the asymmetric common mode direct current offset that causes of output device that the leakage owing to local oscillator causes.By the DC component of extracting is carried out certain processing, obtain a direct current offset value and store.After a period of time, control loop can be freezed, and the frequency shift (FS) of local oscillator can be canceled.Thereby then in normal the reception, cut the compensating circuit that the direct current offset value that stores realizes direct current offset.The process digital circuit of direct current offset calibration.The advantage of this mode is the intrinsic DC component that can protect modulation signal to produce; and do not increase extra analog circuit; its shortcoming is that real-time performance is poor, can not follow the tracks of the variation of the direct-flow offset weight that causes owing to variations in temperature and circuit parameter variations.
Yet, not only simple and easy to do but also zero intermediate frequency direct current offset calibration program with good real-time is not yet proposed so far.
Summary of the invention
Consider the problems referred to above and make the present invention, for this reason, main purpose of the present invention is to provide a kind of direct current offset calibration program, to solve complicated, the poor problem of real-time of the circuit that exists in the middle of the direct current offset calibration in the correlation technique.
According to embodiments of the invention, provide a kind of DC offset calibration method.
The method comprises: select to carry out side-play amount according to the time point position of digital signal reception and obtain processing or calibration process, wherein, be in the situation of burst signals of global system for mobile communications base station in the digital signal that receives, when being positioned at the section start of protection bit of burst signals in the position of time of reception point, beginning to carry out side-play amount and obtain processing; Be positioned in the position of time of reception point in the situation of non-protection bit of burst signals, then carry out calibration process; Side-play amount is obtained processing, is the zero dc offset that obtains by making radio-frequency input signals; Calibration process is come the digital signal that receives is calibrated according to the dc offset that obtains.
Wherein, be positioned in the position of the time of reception point of digital signal in the situation of initial time of the time period that does not receive valid data, begin to carry out side-play amount and obtain processing; Be positioned in the situation that receives the valid data time period in the position of the time of reception point of digital signal, carry out calibration process.
In addition, side-play amount is obtained to process and comprised: making radio-frequency input signals is zero, to the output of FIR filter sample, cumulative and average, and the value that obtains after will be average is as dc offset.
In addition, in calibration process, calibrate by deducting dc offset with the digital signal that receives.
The method can further include: upgrades and processes, and after executing side-play amount acquisition processing, the dc offset that obtains before the dc offset renewal with this acquisition, thereby realization real time calibration.
In addition, when receiving digital signal, at first digital signal is carried out the preliminary treatment of filtering quantization error and interchannel noise, determine afterwards the time point position of digital signal reception.
According to another embodiment of the present invention, provide a kind of direct current offset calibrating installation.
This device comprises: select module, be used for selecting to carry out side-play amount according to the time point position of digital signal reception and obtain processing or calibration process, wherein, be in the situation of burst signals of global system for mobile communications base station in the digital signal that receives, when being positioned at the section start of protection bit of described burst signals in the position of time of reception point, beginning to carry out described side-play amount and obtain processing; Side-play amount obtains module, is used for carrying out side-play amount and obtains processing, and wherein, it is the zero dc offset that obtains by making radio-frequency input signals that side-play amount obtains module; And calibration module, be used for carrying out calibration process, wherein, calibration module comes the digital signal that receives is calibrated according to the dc offset that obtains.
Wherein, be positioned in the position of the time of reception point of digital signal in the situation of initial time of the time period that does not receive valid data, select module to select to begin to carry out side-play amount and obtain processing; Be positioned in the position of the time of reception point of digital signal in the situation of the time period that receives valid data, select module to select to carry out calibration process.
In addition, this device can further comprise: update module is used for after executing side-play amount acquisition processing the dc offset that obtains before the dc offset renewal with this acquisition, thereby realization real time calibration.
By technique scheme of the present invention, can and not affect in the regular traffic situation of base station at the analog circuit that does not increase extra complexity, real-time tracking and the variation of calibrating the direct-flow offset weight that causes owing to variations such as variations in temperature and circuit parameters, and have the simple advantage of realization.
Description of drawings
Accompanying drawing described herein is used to provide a further understanding of the present invention, consists of the application's a part, and illustrative examples of the present invention and explanation thereof are used for explaining the present invention, do not consist of improper restriction of the present invention.In the accompanying drawings:
Fig. 1 is the flow chart according to the DC offset calibration method of the inventive method embodiment;
Fig. 2 is that realization is according to the block diagram of the structure example of the zero intermediate frequency reciver of the DC offset calibration method of the inventive method embodiment;
Fig. 3 is the structural representation according to the adjustable normal burst pulse of the DC offset calibration method of the inventive method embodiment;
Fig. 4 is that zero intermediate frequency reciver is realized the schematic diagram according to the DC offset calibration method of the embodiment of the invention; And
Fig. 5 is the block diagram according to the direct current offset calibrating installation of apparatus of the present invention embodiment.
Embodiment
Embodiment of the method
In the present embodiment, provide a kind of DC offset calibration method.
As shown in Figure 1, comprise according to the DC offset calibration method of present embodiment: step S102, the time point position that receives according to digital signal (for example, IQ digital signal) is selected to carry out side-play amount and is obtained and process or calibration process; Step S 104, and side-play amount obtains to process, and are the zero dc offset that obtains by making radio-frequency input signals; Step S106, calibration process is come the digital signal that receives is calibrated according to the dc offset that obtains.
Wherein, be positioned in the position of the time of reception point of digital signal in the situation of initial time of the time period that does not receive valid data, begin to carry out deviant and obtain processing; Be positioned in the position of the time of reception point of digital signal in the situation of the time period that receives valid data, carry out calibration process.Be in the situation of burst signals of global system for mobile communications base station in the digital signal that receives, the begin column side-play amount obtains to process when as shown in Figure 3, being positioned at the section start of protection bit (8.25) of burst signals in the position of time of reception point; Be positioned in the position of time of reception point in the situation of non-protection bit of burst signals, then carry out calibration process.
In addition, side-play amount to be processed and to be comprised: making radio-frequency input signals is zero, to the output of FIR filter sample, cumulative and average, and the value that obtains after will be average is as dc offset.
In addition, in calibration process, calibrate by deducting dc offset with the digital signal that receives.
The method can further include: upgrades and processes, and after executing side-play amount acquisition processing, the dc offset that obtains before the dc offset renewal with this acquisition, thereby realization real time calibration.
In addition, when receiving digital signal, at first digital signal is carried out the preliminary treatment of filtering quantization error and interchannel noise, determine afterwards the time point position of digital signal reception.
The present invention is both at the scene upper realizations of programmable gate array (FPGA) specifically, also can realize at digital signal processor (DSP).Below just carry out specific description as an example of FPGA example.
Fig. 2 is the fundamental block diagram of zero intermediate frequency reciver, wherein, only shows the I passage among Fig. 2, and the Q passage is the same with the I Channel Perfect.The signal that antenna reception arrives is at first through a radio-frequency filter, the noise that the filtering band is outer; Then through a LNA, carry out radio frequency and amplify; Pass through again frequency mixer, obtain the analog I/Q signal; And then difference is that I+, I-and Q+, Q-are input to low pass filter, the noise that the filtering base band is outer; Carry out differential amplification through a baseband amplifier again; Then be input to ADC by a frequency overlapped-resistable filter difference, become digital IQ signal, be input at last FPGA and process accordingly, the processing that FPGA carries out can comprise calibration and some other base band signal process of the direct current offset shown in Fig. 1, for example, demodulating and decoding etc.Here the form with difference also is in order to reduce common mode direct current offset (null offset).
Fig. 3 is the data format of the normal burst pulse (NB) in the global system for mobile communications (GSM).For NB, its information is divided into two groups of each 58 symbols, and wherein 57 is data, and another one is for stealing flag of frame, and these data of expression are user data or signaling in the CS business.Between this two segment data, insert 26 training sequence, be used for estimating channel parameter and Timing Advance.The tail bit of 3 " 0 " is added on the both sides of message segment.The NB data time of 8.25 arranged at last; do not send out information any; protection section as adjacent time-slots; the calculating of dc offset of the present invention is carried out in this time period exactly; so can not affect regular traffic, and can realize a real time calibration that frequency ratio is higher, namely; each NB time span (577us) can be done primary calibration, thereby can effectively follow the tracks of dc offset with the variation of temperature and circuit parameter.
Fig. 4 shows the schematic diagram of real time calibration of direct current offset that the present invention realizes the zero intermediate frequency reciver of GSM base station.
As shown in Figure 4, from the IQ data of ADC at first through a FIR filter, the quantizing noise of filtering ADC and interchannel noise; Then judge whether the current time is the beginning of 8.25 protection bits, if so, then carries out the calculation process of direct current offset, otherwise normally receives flow process; When carrying out the calculation process of direct current offset, at first making radio-frequency input signals is " zero ", thus the intrinsic DC component of protection modulation signal; Then the output of FIR filter is sampled, added up, then average, mean value just can be thought the direct current offset value under the current circuit parameter, all is white noise because other non-direct current signals can be thought, average is zero; At last the direct current offset value is stored and upgrade the direct current offset value that the last time calculates, use when receiving flow process in order to normal; When the protection bit finishes, then enter normal reception flow process, the digital IQ signal from the output of FIR filter that samples is deducted corresponding direct current offset value, just finished the calibration of direct current offset.Signal after the calibration is proceeded other Base-Band Processing such as demodulating and decoding.
Should be noted that needs in whole calibration process to guarantee that the flow process of calculating direct current offset carries out within the time of protection bit, it is professional normally so just can not affect the base station.
Device embodiment
In the present embodiment, provide a kind of direct current offset calibrating installation.
As shown in Figure 5, the direct current offset calibrating installation according to present embodiment comprises: select module 502, be used for selecting to carry out side-play amount according to the time point position of digital signal reception and obtain processing or calibration process; Side-play amount obtains module 504, obtains to process for carrying out side-play amount, and wherein, it is the zero dc offset that obtains by making radio-frequency input signals that side-play amount obtains module 504; And calibration module 506, be used for carrying out calibration process, wherein, calibration module 506 comes the digital signal that receives is calibrated according to the dc offset that obtains.
Wherein, be positioned in the position of the time of reception point of digital signal in the situation of initial time of the time period that does not receive valid data, select module 502 to select to begin to carry out deviant and obtain processing; Be positioned in the position of the time of reception point of digital signal in the situation of the time period that receives valid data, select module 502 to select to carry out calibration process.
In addition, this device can further comprise: the update module (not shown) is used for after executing side-play amount acquisition processing the dc offset that obtains before the dc offset renewal with this acquisition, thereby realization real time calibration.
Can find out that advantage of the present invention is as follows:
(1) real time calibration: because the dc-bias of receiver not only has relation with temperature, also the relating to parameters with circuit is, so circuit parameter changes each time, just must do the primary calibration operation, just must realize the higher real time calibration of calibration frequency for changing circuit parameter very frequently (for example each time slot needs the circuit parameter that changes) in the GSM base station, and the present invention can carry out primary calibration to each NB, therefore has good real-time;
(2) digital calibration: do not increase complicated analog circuit, can not reduce the receiver linearity, can not bring extra noise, implement fairly simple;
(3) do calibration at the protection bit in the time, can not affect the GSM BTS service;
(4) be " zero " by in the calibration flow process, making input signal, the intrinsic DC component that can effectively protect modulation signal to produce.
In sum; the present invention is directed to the DC offset problem of the zero intermediate frequency reciver that is applied to the GSM base station; a kind of calibration steps real-time, numeral has been proposed; namely; during the protection bit of each NB of GSM base station, calculate the direct current offset value and store, realize real time calibration thereby deduct this direct current offset value at the normal time of reception of next NB.By means of technical scheme of the present invention, can and not affect in the regular traffic situation of base station at the analog circuit that does not increase extra complexity, real-time tracking and the variation of calibrating the direct-flow offset weight that causes owing to variations such as variations in temperature and circuit parameters, and have the simple advantage of realization.
The above is the preferred embodiments of the present invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (9)
1. a DC offset calibration method is characterized in that, comprising:
Select to carry out side-play amount according to the time point position of digital signal reception and obtain processing or calibration process, wherein, be in the situation of burst signals of global system for mobile communications base station in the digital signal that receives, when being positioned at the section start of protection bit of described burst signals in the position of time of reception point, beginning to carry out described side-play amount and obtain processing; Be positioned in the position of time of reception point in the situation of non-protection bit of described burst signals, then carry out described calibration process;
Described side-play amount is obtained processing, is the zero dc offset that obtains by making radio-frequency input signals;
Described calibration process is come the digital signal that receives is calibrated according to the dc offset that obtains.
2. method according to claim 1 is characterized in that, is positioned in the position of the time of reception point of digital signal in the situation of initial time of the time period that does not receive valid data, begins to carry out described side-play amount and obtains processing; Be positioned in the position of the time of reception point of described digital signal in the situation of the time period that receives valid data, carry out described calibration process.
3. method according to claim 1 is characterized in that, described side-play amount is obtained to process and comprised: making radio-frequency input signals is zero, to the output of FIR filter sample, cumulative and average, and the value that obtains after will be average is as described dc offset.
4. method according to claim 1 is characterized in that, in described calibration process, calibrates by deducting dc offset with the digital signal that receives.
5. method according to claim 1 is characterized in that, further comprises:
Upgrade and process, after executing side-play amount acquisition processing, the dc offset that obtains before the dc offset renewal with this acquisition, thereby realization real time calibration.
6. each described method in 5 according to claim 1, it is characterized in that, when receiving described digital signal, at first described digital signal is carried out the preliminary treatment of filtering quantization error and interchannel noise, determine afterwards the time point position of described digital signal reception.
7. a direct current offset calibrating installation is characterized in that, comprising:
Select module, be used for selecting to carry out side-play amount according to the time point position of digital signal reception and obtain processing or calibration process, wherein, be in the situation of burst signals of global system for mobile communications base station in the digital signal that receives, when being positioned at the section start of protection bit of described burst signals in the position of time of reception point, beginning to carry out described side-play amount and obtain processing; Be positioned in the position of time of reception point in the situation of non-protection bit of described burst signals, then carry out described calibration process;
Side-play amount obtains module, is used for carrying out described side-play amount and obtains processing, and wherein, it is the zero dc offset that obtains by making radio-frequency input signals that described side-play amount obtains module;
Calibration module is used for carrying out described calibration process, and wherein, described calibration module comes the digital signal that receives is calibrated according to the dc offset that obtains.
8. device according to claim 7 is characterized in that, is positioned in the position of the time of reception point of digital signal in the situation of initial time of the time period that does not receive valid data, and described selection module is selected to begin to carry out described side-play amount and obtained processing; Be positioned in the position of the time of reception point of described digital signal in the situation of the time period that receives valid data, described selection module selects to carry out described calibration process.
9. device according to claim 7 is characterized in that, further comprises:
Update module is used for after executing side-play amount acquisition processing the dc offset that obtains before the dc offset renewal with this acquisition, thereby realization real time calibration.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101616125B (en) * | 2008-06-26 | 2012-06-27 | 大唐移动通信设备有限公司 | Zero intermediate frequency transmitter and method for calibrating zero intermediate frequency transmitting signals |
| CN101299616B (en) * | 2008-07-08 | 2011-08-17 | 北京天碁科技有限公司 | Radio frequency receiver as well as electronic apparatus containing the same |
| CN101299615B (en) * | 2008-07-08 | 2012-05-16 | 北京天碁科技有限公司 | Method and device for eliminating direct current drift of radio frequency receiver |
| CN102244523B (en) * | 2011-06-23 | 2014-07-16 | 中国科学院上海高等研究院 | Zero intermediate frequency receiver and method for eliminating DC offset of same |
| CN102916659B (en) * | 2011-08-04 | 2015-11-25 | 联芯科技有限公司 | Inductance capacitance automatic calibrating method and circuit |
| CN103095320A (en) * | 2011-10-28 | 2013-05-08 | 京信通信系统（中国）有限公司 | Zero intermediate frequency receiver and direct current leakage suppression method thereof |
| CN103532891B (en) * | 2012-07-06 | 2016-09-07 | 展讯通信（上海）有限公司 | Receiver and direct current estimation method and device, direct current elimination method and device |
| CN104237942B (en) * | 2013-06-17 | 2019-06-14 | 英洛瓦(天津)物探装备有限责任公司 | Offset is removed from seismic signal |
| CN104253780B (en) * | 2013-06-27 | 2017-07-28 | 鸿富锦精密工业（深圳）有限公司 | Direct-current offset calibration circuit |
| US20150201384A1 (en) * | 2014-01-10 | 2015-07-16 | Qualcomm Incorporated | Method for transmitter direct current offset compensation |
| KR101464373B1 (en) * | 2014-04-22 | 2014-12-04 | 김종태 | Sensor module for setting up operating reference by measured value |
| CN109274627B (en) * | 2018-11-19 | 2021-05-11 | 上海航天测控通信研究所 | Ka frequency band QPSK direct modulation device and communication equipment |
| CN111310522A (en) * | 2018-12-12 | 2020-06-19 | 航天信息股份有限公司 | Method and equipment for removing direct current |
| CN113346903B (en) * | 2021-06-18 | 2023-07-14 | 重庆吉芯科技有限公司 | On-line self-adaptive direct current offset correction circuit and receiver |
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| CN1223030A (en) * | 1996-08-02 | 1999-07-14 | 齐尼思电子公司 | DC offset compensation method and apparatus |
| CN1536770A (en) * | 2003-05-15 | 2004-10-13 | 威盛电子股份有限公司 | Direct conversion receiver with DC offset compensation function and compensation method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1223030A (en) * | 1996-08-02 | 1999-07-14 | 齐尼思电子公司 | DC offset compensation method and apparatus |
| CN1536770A (en) * | 2003-05-15 | 2004-10-13 | 威盛电子股份有限公司 | Direct conversion receiver with DC offset compensation function and compensation method thereof |
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