CN1581940A - Receiving system for television receiver - Google Patents
Receiving system for television receiver Download PDFInfo
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- CN1581940A CN1581940A CN 03133644 CN03133644A CN1581940A CN 1581940 A CN1581940 A CN 1581940A CN 03133644 CN03133644 CN 03133644 CN 03133644 A CN03133644 A CN 03133644A CN 1581940 A CN1581940 A CN 1581940A
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- noise
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- receiving system
- frequency domain
- equalizer
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Abstract
The receiving system eliminates increment of noise generated in system of using equalizer in frequency domain. The disclosed receiving system is composed of following parts: demodulator for converting and recovering signal in radio frequency received from transmitting system; equalizer in frequency domain for compensating attenuation being occurred between transmitting system and receiving system; noise killer for eliminating increment of noise generated in equalizer in frequency domain.
Description
Technical field
The present invention will be referred to a kind of receiving system, more particularly relates to the receiving system that a kind of elimination occurs in the television set of the noise increase in the frequency domain equalization device.
Background technology
Digital transmission system that generally uses and conduct are towards the ATSC 8VSB transfer system of Digital Television (DTV) load mode of the U.S. now, with the transfer system that utilizes PAM or QAM, when transmitting with aerial ripple or wired mode, these signals that are transmitted will be reflected by a plurality of reflectors, the therefore received a kind of signal that is mixed by these reflections; At this moment, owing to will make original distorted signals through the composition of reflection, thereby only can't obtain original signal with received signal.Therefore, will use equalizer (equalizer) to compensate to make the composition (ghost: ghost image, or fading: decay) of the signal generation distortion that transmits between transmitting end and the receiving terminal.
Equalizer can be divided into time-domain equalizer (time-domain equalizer) and frequency domain equalization device (frequency domain equalizer), and they all play a part to eliminate the composition that makes original distorted signals.Fig. 1 is to use the receiving system figure of common frequencies territory equalizer.As shown in Figure 1, this receiving system is made up of following two parts, the RF signal that receives is passed through carrier wave/processes such as (carrier/timing) recovery synchronously that is:, is demodulated to the demodulator (demodulator) (1) of base band (base-band) signal; The signal that receives is arrived the frequency domain equalization device (2) that the various decay (fading) that take place during the receiver compensate from sender unit.
The frequency domain equalization device is from time-domain signal, infer after the channel impulse response, the channel impulse response of inferring is converted to frequency domain signal, removes the coefficient of territory equalizer of adjusting frequency then, so that make because channel and the frequency domain signal of distortion becomes a desirable frequency domain signal.Thereby make the frequency domain equalization device play the effect of compensating distortion.And the received signal of time-domain is converted to after the frequency domain signal, comes compensate for attenuation (fading) composition by the frequency domain equalization device, so the frequency domain signal that is compensated also will will be converted to time-domain signal again.
Fig. 2 is presented at the channel that mixes decay in the common receiver and the figure of received signal frequency spectrum; (a) show the channel impulse response of 3 deamplifications with main signal and time of delay; (b) show a kind of desirable letter signal frequency spectrum that sender unit sends, the frequency spectrum when existing with decay is the figure that white noise AWGN deepens.As shown in Figure 2, for the channel with decay, if the frequency pulse of channel response is converted to frequency domain signal, having size with desirable channel so is 1 and smooth situation is compared, and can produce to have big or small low-down part (spectrum null).
Signal when Fig. 3 is to use the frequency domain equalization device to come the compensate for attenuation composition and noise spectrum variation diagram.As seen from the figure, (a) be the signal before carrying out equilibrium and the frequency spectrum of noise; At this moment, AWGN will be superimposed upon on the whole wave band with certain size; Then on characteristic frequency, the size of its frequency spectrum is very little for the received signal that mixes decay.And, (b) be the signal spectrum of process frequency domain equalization; Though signal spectrum is with the ideal signal unanimity, before compensation, the noise at the little place of signal spectrum has just become greatly.In the time of will converting time-domain signal to again through the signal of frequency domain equalization,,, cause performance to become bad owing to, make whole signal all increase noise at the interval noise that increases of characteristic frequency though decay has obtained compensation.
Summary of the invention
The present invention develops in order to solve the problem that exists in the above-mentioned conventional art, its purpose be to provide a kind of can be to the equalizing signal in the frequency domain, the receiving system that abates the noise.
In order to realize above-mentioned purpose, the present invention has the architectural feature be made up of following components, is provided with demodulator that is:, and it will receive the RF signal from transmission system, change then, restore; Be provided with the frequency domain equalization device, it will compensate by transmission system and arrive the decay that is taken place during the receiving system; Be provided with noise killer, it will eliminate the noise of the increase that takes place in the frequency domain equalization device.
Noise killer then is made up of following components, is provided with the 1st subtracter that is:, and it can make the reference noise that will compensate; Be provided with the 2nd subtracter, it can deduct the noise of deduction in reference noise, and its difference is used as error; Be provided with the 3rd subtracter, it can deduct the noise of deduction in input signal, so as to eliminate the noise that increases because of the noise that causes in equalizer output; Be provided with the LMS filter, it will use LMS (lowest mean square criterion: the coefficient update mode of mode leastmean square); Be provided with VSB (residual sideband) amplitude limiter.
Advantage of the present invention is that as mentioned above, when only using legacy frequencies territory equalizer, by the increase of noise, though compensated decay, its signal to noise ratio is very poor.But the noise killer of the application of the invention is eliminated after the noise of increase, just can obtain improving after the equilibrium effect of systematic function.
Description of drawings
The present invention is described in further detail below in conjunction with drawings and Examples.
Fig. 1 is common receiving system figure.
Fig. 2 is presented in the common receiving system, is mixed with the figure of the frequency spectrum of the channel of decay and received signal.
Fig. 3 is presented in the common receiving system, balanced front/rear noise pattern.
Fig. 4 is the figure that shows the receiving system among the present invention.
Fig. 5 is the noise killer details drawing in the receiving system of the present invention.
Fig. 6 is in receiving system of the present invention, the details drawing of the noise spectrum that noise eliminating is front/rear.
Fig. 7 is the performance evaluation curve of receiving system of the present invention.
The symbol description of accompanying drawing major part
10: demodulator
11: the frequency domain equalization device
12: noise killer
Embodiment
Fig. 4 is about receiving system figure of the present invention.As shown in Figure 4, receiving system is made up of following components, is provided with demodulator (demodulator) (10) that is:, and it by carrier wave/processes such as (carrier/timing) recovery synchronously, is demodulated to base band (base-band) signal with the RF signal that receives; Be provided with frequency domain equalization device (frequency domain equalizer) (11), the various decay (fading) that it will be taken place between will compensating from the sender unit to the receiver; Be provided with noise killer (12), it is connected on frequency domain equalization device (11), and will eliminate the noise that is taken place in the signal via this frequency domain equalization device (11).
Fig. 5 is the detailed structure view of the receiving system noise killer of Fig. 4.As shown in Figure 5, input value is a signal that is converted to time-domain of frequency domain equalization device (11) output of Fig. 4; Output valve is then exported from noise killer (12); And, by the 1st subtracter (101), from input signal, deduct the output signal of the noise killer of make a strategic decision (decision), generate the reference noise that will compensate whereby; Reference error is used as the input signal of LMS filter (104).In addition, the 2nd subtracter (102) will deduct the deduction noise from reference noise, and fill with its difference and to do error.This error is used as the error input of LMS filter (104); The 3rd subtracter (103) then from the input signal of noise killer, deducts the noise of deduction, so as to eliminating because of increase the noise that noise increases in equalizer (11) output.In addition, LMS filter (104) is to use the filter of LMS (least meansquare) the formula coefficient update mode of tapped delay line (tapped delay-line).
The coefficient update mode is as follows.
C(k，n+1)＝c(k，n)+ue(n)×(k，n)
Here, n represents 0,1,2 ....; K represents the coefficient of k tap.U is with the integer that decides the updating value size; E (n) is the error originated from input value; (k is at n in the time n) to x, the input value of k tap.
LMS filter (104) can also use the filter of other forms that can predict noise (noise prediction).VSB amplitude limiter (105) is the part that is used for judging the VSB signal, therefore can use the algorithm that can judge the VSB signal.
Fig. 6 is the receiver spectrogram of use noise killer of the present invention.As shown in Figure 6, (a) show in signal, through the situation that noise increases in frequency spectrum after the equilibrium through legacy frequencies territory equilibrium; (b) show when reinstating noise killer, abating the noise increases after the composition, dwindles the situation of whole noise level.
Fig. 7 is the performance evaluation curve of receiving system.As shown in Figure 7, receiving system has been used the tapped delay line filter and the VSB amplitude limiter with amplitude limit forecast function of LMS coefficient update mode; There is shown the SNR (signal to noise ratio) of the output signal when using noise killer whether.Do not use noise killer first kind of situation (eqoutl, ncoutl) under, the signal to noise ratio of equalizer output changes in 5～9dB scope with the angle of deamplification; Reinstate under the noise killer situation, can bring up to 22-25dB.Second kind of situation is that the signal to noise ratio of equalizer output is about 19dB in the decay channel; And after reinstating noise killer, then can be improved to about 26dB.
By above explanation, if the professional person, so all as can be known in not breaking away from technological thought scope of the present invention, can carry out numerous variations or correction.And technical scope of the present invention will can not be confined to the content that example is put down in writing, but will decide according to the claim scope of patent.
Claims (2)
1, a kind of receiving system of television set is characterized in that it is provided with demodulator, and it will receive the RF signal from transmission system, change then, restore; Also be provided with the frequency domain equalization device, it will compensate by transmission system and arrive the decay that is taken place during the receiving system; Be provided with noise killer, it will eliminate the noise of the increase that takes place in the frequency domain equalization device.
2, receiving system according to claim 1 is characterized in that described noise killer is provided with the 1st subtracter, and it can make the reference noise that will compensate; Be provided with the 2nd subtracter, it can deduct the noise of deduction in reference noise, and its difference is used as error; Be provided with the 3rd subtracter, it can deduct the noise of deduction in input signal, so as to eliminate the noise that increases because of the noise that causes in equalizer output; Be provided with the LMS filter, it will use LMS (lowest mean square criterion: the coefficient update mode of mode least mean square); Be provided with VSB (residual sideband) amplitude limiter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031336442A CN100362855C (en) | 2003-08-05 | 2003-08-05 | Receiving system for television receiver |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031336442A CN100362855C (en) | 2003-08-05 | 2003-08-05 | Receiving system for television receiver |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1581940A true CN1581940A (en) | 2005-02-16 |
| CN100362855C CN100362855C (en) | 2008-01-16 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB031336442A Expired - Fee Related CN100362855C (en) | 2003-08-05 | 2003-08-05 | Receiving system for television receiver |
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| Country | Link |
|---|---|
| CN (1) | CN100362855C (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR0165507B1 (en) * | 1996-01-09 | 1999-03-20 | 김광호 | Equalizing method and equalizer using standard signal |
| EP0796010B1 (en) * | 1996-03-12 | 2001-08-01 | Matsushita Electric Industrial Co., Ltd. | Noise reduction circuit for a TV receiver |
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2003
- 2003-08-05 CN CNB031336442A patent/CN100362855C/en not_active Expired - Fee Related
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| Publication number | Publication date |
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| CN100362855C (en) | 2008-01-16 |
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Granted publication date: 20080116 Termination date: 20100805 |