CN100367781C - Control Method of Digital Automatic Level Gain - Google Patents
Control Method of Digital Automatic Level Gain Download PDFInfo
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- CN100367781C CN100367781C CNB2006100259878A CN200610025987A CN100367781C CN 100367781 C CN100367781 C CN 100367781C CN B2006100259878 A CNB2006100259878 A CN B2006100259878A CN 200610025987 A CN200610025987 A CN 200610025987A CN 100367781 C CN100367781 C CN 100367781C
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Abstract
一种数字自动电平增益的控制方法，属于数字信号传输技术领域。本发明通过一个自动电平增益控制环路来实现，所述自动电平增益控制环路，包括两个复乘器，一个平方根检波器、对数运算器、实数减法器、实乘器、积分器，和反对数运算器；信号经过解调后处理得到的复信号由I路和Q路组成，为(XI(n)+jXQ(n))，经过与数字AGC的控制信号M相乘，得到输出信号(YI(n)+jYQ(n))；将其送入一个信号功率检测器，虚实部各取平方后相加，取对数；再与一个预先设置的参考值R相减，得到误差信号ERR；将其乘上一个增益值K；再作平均；对输出取反对数后得到AGC的控制信号M；本方法对所接收的信号电平进行有效控制和补偿，减少了信号功率的波动范围。并可广泛用于系统各模块的数据电平控制。
A digital automatic level gain control method belongs to the technical field of digital signal transmission. The present invention is realized by an automatic level gain control loop, and the automatic level gain control loop includes two complex multipliers, a square root detector, a logarithmic operator, a real number subtractor, a real multiplier, an integral device, and antilog operator; the complex signal obtained after signal demodulation is composed of I road and Q road, which is (XI(n)+jXQ(n)), and multiplied by the control signal M of the digital AGC, Obtain the output signal (YI(n)+jYQ(n)); send it to a signal power detector, take the square of the virtual and real parts, add them up, and take the logarithm; then subtract it from a preset reference value R, Get the error signal ERR; multiply it by a gain value K; average again; take the logarithm of the output to get the AGC control signal M; this method effectively controls and compensates the received signal level, reducing the signal power range of fluctuations. And can be widely used in the data level control of each module of the system.
Description
Technical field
The present invention relates to a kind of method of digital signal transmission technique field, relate in particular to a kind of control method that is applicable to the digital automatic electric-level gain of Digital Television Terrestrial Broadcasting receiver.
Technical background
In the high-speed digital signal wireless transmitting system, such as digital high-definition television (HDTV), signal is subjected to the influence of transmission channel in the wireless transmission process, and the influences such as employing of reception antenna have a fluctuation on a large scale in the signal power of receiving terminal.In actual conditions, such as under vehicle-mounted situation of movement, enter and leave blocking of a mansion, the just very possible appearance of receiver receives that at a time signal level is 3uV, and at another constantly, may just in time leave blocking of mansion and the signal received just may be 1V.Therefore the adjusting range that just needs a nearly 110dB scope to received signal.Fig. 1 has shown that ADTB-T OQAM system data adds the spectrogram of double pilot, has illustrated the relative amplitude size of frequency spectrum among the figure.But problem is that in receiver, because the limited quantified precision of A/D converter, the range of signal that can represent is less than the dynamic change scope of received signal amplitude.Therefore automatic electric-level gain control agc circuit commonly used comes to received signal level to control and compensate in receiver.
In general, AGC can be divided into two kinds by the form of control signal: promptly simulate AGC and digital AGC, in actual applications, what often adopt is that the mode that simulation AGC and digital AGC interosculate is carried out work.AGC carries out coarse adjustment with simulation, carries out fine tuning with digital AGC.The present invention is adjusted to the basis with the digital AGC as the fine tuning link.
Finding through the literature search to prior art, is in the Chinese patent " agc circuit " of " CN200410056346.X " in the disclosed patent No. of 2005.02.16, has proposed a kind of circuit of AGC control.Control signal is an analog signal among the AGC that this patent proposes, and can carry out adjusting in a big way, but if be applied to ADTB-T advanced digital terrestrial broadcast system, then precision may be not enough.
ADTB-T advanced digital terrestrial broadcast system, its transmission system is based on OQAM offset quadrature amplitude modulation(PAM).Because OQAM coherent demodulation reprocessing output I and Q two-way can co-extracted control informations from I and Q road signal.And in fact VSB has only I one road signal to use, and available information is few.And the I of QAM modulating system and Q road are mutually independently, do not become the Hilbert variation relation.Therefore in application, might make full use of the performance that I and Q two-way information improve the AGC control circuit at ADTB-T advanced digital terrestrial broadcast system.
Summary of the invention
The present invention is directed to the deficiencies in the prior art, the digital automatic electric-level gain control method of receiver in a kind of Digital Television Terrestrial Broadcasting is provided.The invention solves digital signal in the wireless transmission process, be subjected to channel effects, receiving end signal power has large-scale fluctuation, thereby influences the problem of the quality of reception.
The present invention realizes that by the following technical solutions a kind of digital automatic electric-level gain control method of Digital Television Terrestrial Broadcasting receiver that is applicable to comprises: realize received signal is regulated by an automatic electric-level gain control loop; Wherein, described automatic electric-level gain control loop comprises: two multipliers, and a square root wave detector, a logarithm operation device, a real substract musical instruments used in a Buddhist or Taoist mass, a reality is taken advantage of device, an integrator and an antilogarithm arithmetic unit; The OQAM signal is made up of two paths of signals through the complex signal that the demodulation reprocessing obtains in receiver, and they are respectively I road and Q road, and complex signal is expressed as (XI (n)+jXQ (n)); Above-mentioned complex signal is respectively through a multiplier, multiplies each other with the control signal M of digital AGC, obtains output signal (YI (n)+jYQ (n)); This signal is sent into a signal power detector, and to real part and each squared back addition of imaginary part, what obtain basically is signal power; Above-mentioned signal power is taken the logarithm; Signal power after taking the logarithm and a reference value R who sets in advance are subtracted each other, obtain an error signal ERR; Above-mentioned error signal is sent into a reality take advantage of device, be multiplied by a yield value K; Above-mentioned reality is taken advantage of device output to send into an integrator again and is done on average, to cut down noise jamming; To obtaining the control signal M of this digital AGC after the operation of above-mentioned integrator output negate logarithm; The control signal M of digital AGC is sent back to the multiplier on I and Q road, make the signal level of output (YI (n)+jYQ (n)) keep stable.
In ADTB-T advanced digital terrestrial broadcast system, in the receiver of OQAM offset quadrature amplitude modulation(PAM) branch system, after the A/D sampling, pass through a digital automatic electric-level gain control loop, the size of the quantized data after the A/D is carried out estimation based on statistical average, promptly to square (being the power of signal) of sampled data, and with the direct estimation of this average as signal power.
Described automatic electric-level gain control loop (AGC loop) both can be to after the receiver down-conversion and the data after the A/D sampling carry out automatic electric-level gain control, also can be that the data in the A/D sampling back institute tool carrier recovery loop are carried out automatic electric-level gain control.
Digital automatic electric-level gain control method of the present invention, its reference value R that sets in advance can select the average power signal of the data message of system transmissions.This reference value R that sets in advance also may be selected to be 20.
The present invention program's beneficial effect is that given digital automatic electric-level gain control device can effectively be controlled and compensate the signal level that is received, and reduces the fluctuation range of signal power, adopts digital controlled signal simultaneously, has higher precision.And the data level that can be widely used in each module of system is controlled.
Description of drawings
Fig. 1 adds the double pilot spectrogram for ADTB-T OQAM system data
The digital AGC loop of Fig. 2 for adopting in the inventive method
Embodiment
Below in conjunction with embodiment the present invention is further described.
The present invention realizes received signal is regulated by an automatic electric-level gain control loop, and Fig. 2 has shown a kind of digital AGC loop that adopts in the inventive method.Described AGC loop comprises two multipliers, a square root wave detector, and a logarithm operation device, a real substract musical instruments used in a Buddhist or Taoist mass, a reality is taken advantage of device, an integrator and an antilogarithm arithmetic unit, control method is specially:
In based on the OQAM communication system for modulation, the OQAM signal arrives after the receiver, at first passes through demodulation, is made up of I and Q two paths of signals through the complex signal that the demodulation reprocessing obtains, and represents with (XI (n)+jXQ (n)); I that (XI (n)+jXQ (n)) forms and Q two paths of signals be respectively through a multiplier, multiplies each other with the control signal M of digital AGC, obtains output signal (YI (n)+jYQ (n)), and this control signal M is from the output of AGC loop; (YI (n)+jYQ (n)) sends into a signal power detector with signal, to real part and each squared back addition of imaginary part.What obtain basically is signal power; Above-mentioned signal power is taken the logarithm; Signal power after taking the logarithm and a reference value R who sets in advance are subtracted each other, obtain an error signal ERR; Above-mentioned error signal is sent into a reality take advantage of device, be multiplied by a yield value K; Above-mentioned reality is taken advantage of device output to send into an integrator again and is done on average, to cut down noise jamming; To obtaining the control signal M of this digital AGC after the operation of above-mentioned integrator output negate logarithm; The control signal M of digital AGC is sent back to the multiplier on I and Q road, make the signal level of output (YI (n)+jYQ (n)) keep stable.
In above-mentioned flow process, if the detected input signal power of receiver less than the power of expection, obtains a positive number after result after taking the logarithm so and preset reference value R subtract each other.Through after taking advantage of device and integrator in fact, remain a positive number.Positive number finally becomes one greater than 1 digital M through the operation of negate logarithm, and this M will increase the energy of input signal as the signal multiplication of control signal and input.
Otherwise, if the detected input signal power of receiver greater than the power of expection, obtains a negative after result after taking the logarithm so and preset reference value R subtract each other.Through after taking advantage of device and integrator in fact, remain a negative.Negative finally becomes one less than 1 digital M through the operation of negate logarithm, and this M will reduce the energy of input signal as the signal multiplication of control signal and input.
Finally, by the continuous adjusting of loop, if being provided with of loop parameter is suitable, the input signal power power that will equal to expect so, after the result after taking the logarithm so subtracts each other with preset reference value R zero.Through after taking advantage of device and integrator in fact, remain zero.Control signal M becomes 1, and the energy of input signal keeps constant on the average meaning.
Use take the logarithm device and the operation of negate logarithm in the loop, purpose is to make control signal M to regulate input signal by multiplication.Device and the negate logarithm operation if do not take the logarithm, control signal will be regulated input signal by plus and minus calculation so.In general, the use of multiplication can make the convergence rate of loop and convergence result all improve greatly.
Integrator in the loop is equivalent to the function of an averager.Because signal is a random distribution, actual Research Significance is just arranged so be averaged energy.Also help improving the convergence rate of loop.
Claims (4)
1. the control method of a digital automatic electric-level gain, it is characterized in that: realize received signal is regulated by an automatic electric-level gain control loop, in communication system based on the offset orthogonal amplitude modulation(PAM), the offset orthogonal am signals arrives after the receiver, at first pass through demodulation, form by I and Q two paths of signals through the complex signal that the demodulation reprocessing obtains, represent with (XI (n)+jXQ (n)); I that (XI (n)+jXQ (n)) forms and Q two paths of signals are respectively through a multiplier, multiply each other with the control signal M of digital Auto Gain control, obtain output signal (YI (n)+jYQ (n)), this control signal M is from the output of automatic gain control loop, (YI (n)+jYQ (n)) sends into a signal power detector with signal, to real part and each squared back addition of imaginary part;
What obtain is signal power, and above-mentioned signal power is taken the logarithm, and the signal power after taking the logarithm and a reference value R who sets in advance are subtracted each other, and obtains an error signal ERR; Above-mentioned error signal is sent into a reality take advantage of device, be multiplied by a yield value K; Above-mentioned reality is taken advantage of device output to send into an integrator again and is done on average, to cut down noise jamming, to obtaining the control signal M of this digital Auto Gain control after the operation of above-mentioned integrator output negate logarithm, the control signal M of digital Auto Gain control is sent back to the multiplier on I and Q road, make the signal level of output (YI (n)+jYQ (n)) keep stable.
2. the control method of digital automatic electric-level gain according to claim 1, it is characterized in that, described automatic electric-level gain control loop, be to after the receiver down-conversion and the data after the A/D sampling carry out automatic electric-level gain control, or the data in the A/D sampling back institute tool carrier recovery loop are carried out automatic electric-level gain control.
3. the control method of digital automatic electric-level gain according to claim 1 is characterized in that, the average power signal of the data message of the reference value R selective system transmission that sets in advance.
4. according to the control method of claim 1 or 3 described digital automatic electric-level gains, it is characterized in that the reference value R that sets in advance is chosen as 20.
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| CN101977392A (en) * | 2010-10-26 | 2011-02-16 | 三维通信股份有限公司 | Method for detecting input and output power of digital repeater |
| CN105490653A (en) * | 2015-11-24 | 2016-04-13 | 西安烽火电子科技有限责任公司 | Quick digital automatic gain control method based on orthogonal detection |
| CN107086859B (en) * | 2017-04-17 | 2020-11-20 | 东南大学 | Digital Automatic Gain Control Circuit for Wireless Communication Receiver |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1043236A (en) * | 1988-11-30 | 1990-06-20 | 莫托罗拉公司 | Digital automatic gain control |
| JPH05122264A (en) * | 1991-09-26 | 1993-05-18 | Nec Eng Ltd | Automatic gain control circuit |
| CN1200848A (en) * | 1995-09-15 | 1998-12-02 | 夸尔柯姆股份有限公司 | Linear digital automatic gain control |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1043236A (en) * | 1988-11-30 | 1990-06-20 | 莫托罗拉公司 | Digital automatic gain control |
| JPH05122264A (en) * | 1991-09-26 | 1993-05-18 | Nec Eng Ltd | Automatic gain control circuit |
| CN1200848A (en) * | 1995-09-15 | 1998-12-02 | 夸尔柯姆股份有限公司 | Linear digital automatic gain control |
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