CN1592369B

CN1592369B - Apparatus and method for detecting and selectively filtering co-channel interference

Info

Publication number: CN1592369B
Application number: CN2004100593412A
Authority: CN
Inventors: 金敏镐
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2003-06-19
Filing date: 2004-06-18
Publication date: 2011-08-31
Anticipated expiration: 2024-06-18
Also published as: JP4806170B2; CN1592369A; JP2005012803A

Abstract

To provide an apparatus and a method for detecting cochannel interference and selectively filtering it. In detecting the existence of an analog TV signal (for example, NTSC signal), which is in the same channel as a DTV signal and causes interference, is verified by detecting the existence of the analog SYNC signal in a received signal bandwidth. When the SYNC signal of an adequate frequency is detected, an analog TV signal removing filter is inserted into a processing path of the DTV signal.

Description

Detect and the apparatus and method disturbed of filtering co-channel optionally

Related application

The application requires to benefit from the korean patent application No2003-0039898 of application on June 19th, 2003, and its open text here is incorporated herein by reference.

Technical field

The present invention relates to be used for the co-channel interference filter of digital television signal, and relate in particular to and be used to detect method and apparatus that co-channel interference exists optionally to use co-channel interference filter.

Background technology

Traditional broadcast television signal is actually strict simulation.These traditional signals meet a kind of in three kinds of broadcast systems of extensive employing usually: NTSC (NTSC) standard that the U.S. and some other countries adopt, and most of other countries PAL (line-by-line inversion) and SECAM ("systeme electronique couleur avec memoire") standard that adopt.

High definition TV (HDTV) or more generally be called Digital Television (DTV) standard and abandon traditional anolog TV signals form is supported digitally encoded signal.Owing to find bulk redundancy in most of vision signals, digital compression video sequence is in one way visually discovered less than (or almost discover less than) and is changed when not compressing.So such DTV signal can send more details than the suitable analog signal of same bandwidth.The current HDTV standard of carrying out in the U.S., HDTV bandwidth are set to roughly take with a simulation NTSC broadcasts having from the channel of the channel allocation of space identical with the NTSC channel of identical bandwidth.

Although long-term plan is progressively to stop the NTSC channel, most TV user also do not have the HDTV receiver and conversion can very fast appearance completely.In a period of transition, the TV station of broadcasting HDTV signal may have the spectators that receive the relative strong NTSC signal with undesired but signal of the HDTV signal wanted on same channel simultaneously.In this case, NTSC and HDTV signal interfere with each other, and produce known what is called " co-channel " and disturb.

With reference to Fig. 1, the frequency spectrum 100 of NTSC signal has been described.Envelope 110 is represented when the DTV signal takies the channel space identical with the NTSC signal, the DTV information that sends in NTSC signal channel space.The video carrier V that is positioned at the lower boundary 1.25MHz of the frequency spectrum that distance distributes is used for the luminance component of the original NTSC signal of demodulation.Be arranged in the NTSC quadrature chrominance signal that is used for the demodulation color TV set than the colour subcarrier C of the high 3.58MHz of video carrier V.The sound carrier A that is positioned at than the high 4.5MHz of video carrier is used for demodulation NTSC frequency modulation (FM) audio signal, and this audio signal is launched at the quite little frequency band that is arranged in carrier wave A center.

When HDTV signal and NTSC signal took identical channel space, the NTSC signal can produce strong jamming.Therefore be desirable to the HDTV signal filtering that receives in advance with the NTSC rejects trap, the NTSC rejects trap can be removed the predictable component of NTSC signal, i.e. video, colour and sound carrier.Typically, comb filter is as the NTSC rejects trap.As shown in Figure 1, comb filter 120 has spaced apart 57f _HThe zero-signal of Hz, wherein f _HIt is the horizontal frequency (is 15.734kHz to ntsc video) of analog video signal.A comb filter zero-signal is aimed at video carrier V is approaching, and another comb filter zero-signal is aimed at colour subcarrier C is approaching, and the 3rd comb filter zero-signal aimed at sound carrier A is approaching.

Can recognize that from Fig. 1 comb filter comprises other zero-signals in HDTV channel space, they can not improve co-channel interference probably.In fact, when not having the NTSC signal, the NTSC rejects trap reduces the about 3dB of signal to noise ratio (snr) of HDTV signal.Therefore, when the co-channel interference of NTSC is lower than 3dB, preferably do not use this filter.Thereby recommendation is not when existing the NTSC signal, and the NTSC rejects trap switches to outside the HDTV signal path.

Used several method to determine in the HDTV channel, whether there is the NTSC signal.U.S. the patent No. 6,201, and 576 have given advice two noise powers calculating on the received signal estimates that has a NTSC rejects trap in position, and one does not have.When the difference between two noise powers are estimated surpasses a threshold value, detect the NTSC signal.When detecting the NTSC signal, the NTSC rejects trap is switched to HDTV handle in the stream.

U.S. the patent No. 6,421, and 077 has given advice a kind of slightly different method that is used to determine whether to exist the co-channel interference of NTSC.The error rate of the error in the HDTV receiver/digital signal that the output of detection correcting circuit is used to receive.This error rate is compared with two conditions--and one is that the NTSC rejects trap is arranged in position, and one does not have.The structure that produces lowest bit error rate is elected the HDTV signal processing path as.

Description of drawings

How the comb filter that Fig. 1 has illustrated the interference spectrum that comprises the ntsc television signal that takies identical frequency band and DTV channel and has been used for the NTSC signal suppressing aims at frequency spectrum;

Fig. 2 has illustrated the DTV receiver according to some embodiments of the present invention;

Fig. 3 comprises the flow chart of filtering/not filtering decision process that expression uses in some embodiments of the invention;

Fig. 4 represents to have the television receiver of DTV and simulated television receiver components, and wherein filtering/not filtering judgement is made in simulated television receiver and the cooperation of DTV receiver; With

Fig. 5 and two DTV receiver embodiment of 6 expressions are exclusively used in the co-channel interference of NTSC and PAL respectively and suppress.

Embodiment

The present invention includes by the property feature that detects anolog TV signals determines to disturb NTSC (or other simulations) TV signal whether to take the embodiment of same channel with the DTV signal.For example, the NTSC signal comprises vertical sync pulse that repeats with the 59.94Hz field frequency and the horizontal synchronization pulse that repeats with the 15.734kHz line frequency.The PAL signal comprises vertical sync pulse that repeats with the 50Hz field frequency and the horizontal synchronization pulse that repeats with 15.625kHz.These synchronizing signal features determine with in certain embodiments whether given simulated television standard signal appears in the current tuning HDTV frequency space.

With reference to Fig. 2, the first television receiver embodiment 200 is described.DTV handles path 210, and to comprise a tuner 220, demodulator 230, Port Multiplier (MUX) 260 and other known and to the unessential DTV function blocks of the present invention (not shown).In addition, when detecting the simulated television that mates with filter 240, anolog TV signals rejects trap 240 can be placed on DTV and handle in the path 210.

Tuner 220 receiving inputted signal IN, according to this signal, tuner 220 is selected a channel.The channel of selecting is provided to demodulator 230, and restoring signal regularly and synchronously and carry out the operation of other preceding filtering.Demodulator output directly is provided to first input of MUX 260 and the input of analog tv signal rejects trap 240.The output of analog tv signal rejects trap 240 is provided to second input of MUX 260.Select signal to be used to switch the output that first or second of MUX 260 is input to MUX 260, handle to carry out further DTV.

Handle the outside in path 210 at DTV, synchronized signal detector 250 receives output and attempts to detect one or more analog TV synchronizing signals tuning channel from tuner 220.If there is interested synchronizing signal, then synchronized signal detector 250 selects to switch input to MUX 260 expressions, handles in the path thereby analog tv signal rejects trap 240 is put into DTV; Otherwise synchronized signal detector 250 is not represented to select to switch input, thereby MUX 260 makes the output of demodulator 230 handle by coming descending DTV.Alternatively, synchronized signal detector 250 enables to export and can close it when not needing the analog tv signal rejects trap.

Fig. 3 shows the usual method 300 of for example handling the DTV signal with the receiver 200 of Fig. 2.In method 300, attempt to carry out the detection of one or more analog TV synchronizing signals.If do not detect synchronizing signal, not to the DTV signal filtering.Otherwise, measurement synchronization pulse repetition rate (PRR) and with the expection PRR compare.If PRR is wrong speed, analog tv signal may exist, but is not can be by the type of rejects trap filtering.If PRR has a unsettled speed, may there be weak analog tv signal, at this moment can make the decision of the DTV signal not being carried out filtering.Finally, if the PRR that measures satisfies the PRR of expection, then use 240 pairs of DTV signal filterings of rejects trap.

Fig. 4 has illustrated second television receiver 400 according to other embodiments of the invention.Receiver 400 comprises tuner 420, and the output of tuner 420 is shared by DTV receiver 410 and analog TV receiver 470, and they all provide video output signals.The DTV receiver comprises demodulator 430, analog tv signal rejects trap 440, MUX 460, and is for example identical with the annexation and the function of same parts in the receiver of Fig. 2.In addition, signal controller 450 provides the selection signal to MUX 460.

As a processed conventionally part, analog TV receiver 470 comprises sync separator, detects the vertical and horizontal synchronization pulse in the analog tv signal when having analog tv signal.In Fig. 4, when DTV receiver video output is selected as from receiver output, the sync separator of analog TV receiver 470 partly starts at least.Therefore, the lock-out pulse that is detected by analog TV receiver 470 is provided to the signal controller 450 in the DTV receiver 410.The synchronization pulse that signal controller 450 uses from analog TV receiver 470 is to determine whether to represent its selection output.In some implementations, analog-and digital-TV receiver can coexist as in the integrated circuit.During other are realized at some, can use obtainable analog TV receiver circuit on the market.

Fig. 5 has illustrated the DTV receiver 500 of some embodiment that are exclusively used in the co-channel interference of NTSC.DTV receiver 500 comprises tuner 520, demodulator 530, NTSC rejects trap 540 and MUX560, and is for example identical with the annexation and the function of same parts in the receiver 200 of Fig. 2.Also show descending several other typical DTV processing unit (equalizer 570 and forward error correction circuit 580) at MUX 560.

Demodulator 530 comprises other sub-piece details.The output of tuner 520 is connected to AD converter 532, and it carries digital sampling to clock recovery and synchronization timing recovery block 534.Matched filter 536 is then operated this sampling, to detect the binary code stream of correct timing.This binary code stream is provided to MUX 560 and NTSC rejects trap 540.

The output of tuner 52 is also supplied to sync separator 552.Sync separator 552 attempts to detect the vertical and/or horizontal synchronization pulse of NTSC in the tuning signal.When detecting lock-out pulse, pulsing is to signal controller 554.Signal controller 554 bases whether detect lock-out pulse and their repetition rate determines whether to select the output of the output of NTSC rejects trap 540 as MUX 560.

Fig. 6 has illustrated the DTV receiver 600 of some embodiment that are exclusively used in the co-channel interference of PAL.DTV receiver 600 comprises tuner 620, demodulator 630, PAL rejects trap 640 and MUX660, and is for example identical with the annexation and the function of same parts in the receiver of Fig. 2.Also show the descending forward error correction circuit of MUX660 680.

Demodulator 630 comprises other sub-piece details.The output of tuner 620 is connected to AD converter 632, and it carries digital sampling to clock recovery and synchronization timing recovery block 634.Fast fourier transform 636 and equalizer/mapper 638 provide the frequency domain representation of binary system inlet flow.This frequency-region signal is provided to MUX 660 and PAL rejects trap 640.

The output of tuner 620 is also supplied to sync separator 652.Sync separator 652 attempts to detect the vertical and/or horizontal synchronization pulse of NTSC in the harmonic ringing.When detecting lock-out pulse, pulsing is to signal controller 654.Signal controller 654 determines whether to select the output of the output of PAL rejects trap 640 as MUX 660 according to whether detecting lock-out pulse and their repetition rate.

In the above-described embodiments, various synchronizing signal analytical technology can be used in and determines whether use NTSC or PAL rejects trap.Might be under the simplest situation, the horizontal synchronization pulse string with repetition rate of the repetition rate that approaches to expect can be used in the decision of making filtering/not filtering.Can substitute the existence of using vertical sync pulse, perhaps may to need level and vertical sync pulse be tangible to signal controller.In certain embodiments, signal controller is also counted the horizontal pulse between continuous vertical sync pulse.

Also can use more complicated method.For example, the AGC in sync separator (automatic gain control) functional block can be represented the relative level about the output point lock-out pulse of tuner.The AGC output level can be provided to signal controller as other criterion.When the AGC output level is represented quite weak NTSC or PAL signal, promptly allow to detect lock-out pulse faint or that be interrupted, signal controller 654 also can select to cancel selected rejects trap.

Sync separator also can be operated the digital sampling that produces in the HDTV demodulator.For example, sync separator can carry out low-pass filtering to ADC output, and then analyzes the low-pass filtering scheme (for example, employing FFT) that is used for corresponding to the frequency content of the horizontal line frequency of analog tv signal and vertical field frequency.Whether the relative intensity of such signal can suitable with the insertion of determining rejects trap by the signal controller analysis.

Use any one in these technology, all might form can program detection and the system of selecting one co-channel interference from several analog TV standards (for example NTSC, NTSC mutation, PAL, SECAM etc.).If a system can insert polytype rejects trap, this system also can design and detect with the interference of multiple analog TV standard and insert suitable rejects trap.

Although comb filter has been described, also can use other filtering techniques to remove one or more spectrum components of interference simulation TV signal.

Those skilled in the art will recognize that and can imagine much other apparatus structure conversion, discussion does not much relate to parameter.Equally, function also can use the circuit of a plurality of cooperations or module to realize that vice versa in functional block.So little modification and realization details comprise in an embodiment of the present invention, and intention falls within the scope of the claims.

Previous embodiment is exemplary.Although specification can be called " one ", " another ", " some " embodiment in some positions, this must not mean that or not is same embodiment that each such quoting is described, and perhaps this feature only is applied among the embodiment.

Claims

One kind can receiving digital television (DTV) signal television receiver, this receiver comprises:

The DTV received signal is handled the path, is configured to produce be used for the output that DTV handles, and described DTV received signal is handled the path and comprised:

Anolog TV signals rejects trap, the one or more spectrum component filtering in the frequency spectrum to received signal; With

Commutation circuit, it is in response to existing or do not exist the anolog TV signals lock-out pulse in received signal, the anolog TV signals rejects trap is switched into the DTV received signal handle in the path or the anolog TV signals rejects trap handled the path from the DTV received signal and switch; And

Synchronized signal detector is positioned at described DTV received signal and handles outside the path, detects the existence of the interior anolog TV signals lock-out pulse of frequency spectrum of received signal.
2. the television receiver of claim 1, wherein commutation circuit comprises the signal controller circuit, the pulse repetition rate of perception anolog TV signals lock-out pulse meets a kind of anolog TV signals rejects trap to its effective broadcast system to verify detected anolog TV signals.
3. the television receiver of claim 2, relatively pulse repetition rate and predetermined pulse repetition rate of commutation circuit wherein is to carry out checking.
4. the television receiver of claim 3, wherein Yu Ding pulse repetition rate is programmed for TSC-system formula pulse repetition rate or pal mode pulse repetition rate.
5. the television receiver of claim 1, wherein the anolog TV signals lock-out pulse of Jian Ceing comprise vertically, level or vertical and horizontal synchronization pulse.
6. the television receiver of claim 1, wherein the anolog TV signals rejects trap is the NTSC rejects trap, wherein synchronized signal detector detects the NTSC lock-out pulse.
7. the television receiver of claim 1, wherein the anolog TV signals rejects trap is the PAL rejects trap, and wherein synchronized signal detector detects the PAL lock-out pulse.
8. the television receiver of claim 1, wherein commutation circuit comprises:

Port Multiplier, be inserted in first data input that the DTV received signal is handled the path and had the output that is connected to the anolog TV signals rejects trap, selection input in second data input of bypass anolog TV signals rejects trap and the input of selection data as Port Multiplier output; With

Signal controller, have and be connected to the output that Port Multiplier is selected input, the pulse repetition rate of signal controller perception anolog TV signals lock-out pulse, and when receiving the anolog TV signals lock-out pulse of predetermined pulse repetition rate, export a signal to select the input of Port Multiplier first data.
9. the television receiver of claim 8, wherein Yu Ding pulse repetition rate is able to programme between corresponding to first pulse repetition rate of NTSC broadcast system and second pulse repetition rate corresponding to the PAL broadcast system.
10. the television receiver of claim 1 also comprises the anolog TV signals processing path that is used to receive anolog TV signals, and wherein synchronized signal detector comprises the part in anolog TV signals processing path.
11. the television receiver of claim 1, wherein synchronized signal detector is represented the relative intensity of the lock-out pulse in the frequency spectrum of received signal, and wherein commutation circuit required before commutation circuit comprises that the DTV received signal is handled anolog TV signals rejects trap in the path, and the anolog TV signals lock-out pulse of detection has minimum at least relative intensity.
12. one kind can receiving digital television (DTV) signal television receiver, receiver comprises:

Tuner is selected television channel and is exported a channel signals;

Demodulator, the receiving channels signal is also exported the channel signals of demodulation;

Sync separator, the receiving channels signal detects the anolog TV signals lock-out pulse in the channel signals, and output sync pulse signal;

Signal controller receives synchronization pulse and produces the control signal that whether has anolog TV signals the expression channel signals from sync separator;

The anolog TV signals rejects trap leaches one or more spectrum components and exports filtered demodulation channel signal from the frequency spectrum of the channel signals of demodulation; With

Port Multiplier according to control signal, is selected the channel signals of demodulation or the demodulation channel signal of filtering,

Wherein anolog TV signals rejects trap and Port Multiplier are included in the DTV receiver, and wherein sync separator is included in the analog TV receiver, and are wherein shared by DTV receiver and analog TV receiver from the channel signals of tuner output, and

Wherein, in the time of among anolog TV signals are present in channel signals, Port Multiplier is optionally exported filtered demodulation channel signal in response to control signal.
13. the integrated circuit that can handle Digital Television (DTV) signal, integrated circuit comprises:

Demodulator, the receiving channels signal is also exported the channel signals of demodulation;

Signal controller receives the anolog TV signals synchronization pulse and produces the control signal that whether has anolog TV signals the expression channel signals from the channel signals sync separator;

The simulated television rejects trap leaches one or more spectrum components and exports filtered demodulation channel signal from the frequency spectrum of the channel signals of demodulation; With

Port Multiplier according to control signal, is selected the channel signals of demodulation or the demodulation channel signal of filtering,

Wherein signal controller, simulated television rejects trap and Port Multiplier are included in the DTV receiver, and wherein the channel signals sync separator is included in the analog TV receiver, and

Wherein, in the time of among anolog TV signals are present in channel signals, Port Multiplier is optionally exported filtered demodulation channel signal in response to control signal.
14. the integrated circuit of claim 13 also comprises the channel signals sync separator.
15. the integrated circuit of claim 14 also comprises anolog TV signals processing path, is used to receive anolog TV signals, wherein the synchronization channel signal separator comprises the part in anolog TV signals processing path.
16. a method of handling Digital Television (DTV) signal, this method comprises:

In the time in the frequency band of DTV signal, can detecting the simulated television synchronizing signal, detect the interior such synchronizing signal of frequency band of DTV signal;

From the simulated television synchronizing signal that detects, determine in the frequency band of DTV signal, whether there are anolog TV signals; With

When determining to have anolog TV signals, before to the DTV signal decoding, pass through the anolog TV signals rejects trap to the DTV signal filtering,

Wherein in the analog TV receiver, carry out detection, wherein in the DTV receiver, carry out filtering, and the testing result in the analog TV receiver is provided for the DTV receiver the DTV signal to the simulated television synchronizing signal.
17. the method for claim 16, whether wherein definite anolog TV signals exist comprises:

Measure the pulse repetition rate of detected simulated television synchronizing signal;

The pulse repetition rate of the pulse repetition rate that compares and measures and the expection of the simulated television synchronizing signal of the anolog TV signals standard that is used to be scheduled to; With

When the pulse repetition rate of measuring mated with the pulse repetition rate of expecting basically, there were anolog TV signals in statement.
18. the method for claim 17, wherein the simulated television synchronizing signal of Jian Ceing comprises vertical synchronizing signal, and the pulse repetition rate of expection is the expection vertical synchronization speed of the anolog TV signals standard of being scheduled to.
19. the method for claim 17, wherein the simulated television synchronizing signal of Jian Ceing comprises horizontal-drive signal, and the pulse repetition rate of expection is the expection horizontal synchronization speed of the anolog TV signals standard of being scheduled to.
20. the method for claim 19, wherein the simulated television synchronizing signal of Jian Ceing also comprises vertical synchronizing signal, and the pulse repetition rate of expection also comprises the vertical synchronization speed of the expection of predetermined anolog TV signals standard, wherein:

The pulse repetition rate of measuring the simulated television synchronizing signal that detects comprises measuring vertical no-load speed and horizontal synchronization speed;

The pulse repetition rate that compares and measures and the pulse repetition rate of expection comprise vertical synchronization speed and the vertical synchronization speed of expection and the horizontal synchronization speed of horizontal synchronization speed that compares and measures and expection that compares and measures; With

The statement analog signal exists and to comprise making during basically with the horizontal synchronization rate-matched of expection with the horizontal synchronization speed of the vertical synchronization rate-matched of expection and measurement basically when the vertical synchronization speed of measuring and state and show.
21. the method for claim 17, wherein Yu Qi pulse repetition rate can be selected between at least two speed of the different anolog TV signals standard of expression.
22. the method for claim 16, wherein extract anolog TV signals comprise measurement with the corresponding frequency of synchronous signal impulse repetition rate on the relative signal energy that exists.
23. the method for claim 22, whether wherein definite anolog TV signals exist comprises, before definite anolog TV signals exist, need with the corresponding frequency of synchronous signal impulse repetition rate on the relative signal energy that occurs have at least one minimum relative intensity.