CN1106116C - Method for transmitting VSB digital TV - Google PatentsMethod for transmitting VSB digital TV Download PDF
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- CN1106116C CN1106116C CN 99101247 CN99101247A CN1106116C CN 1106116 C CN1106116 C CN 1106116C CN 99101247 CN99101247 CN 99101247 CN 99101247 A CN99101247 A CN 99101247A CN 1106116 C CN1106116 C CN 1106116C
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本申请在35U.SC111(a)下提出，根据35U.SC119(e)(1)要求临时申请，序号为60/075424的申请日，其根据35U.SC111(b)在1998年2月20日申请。 In the present application 35U.SC111 (a) made, (e) (1) according to 35 USC 119 to provisional application, Serial No. 60/075424 filed, which according 35U.SC111 (b) on 20 February 1998 Application.
本发明一般涉及电视信号发射系统，特别涉及一种发射残留边带(VSB)数字电视信号的方法，它不易受NTSC同频道干扰。 The present invention generally relates to a television signal transmission system, particularly to a method for transmitting a vestigial sideband (VSB) digital television signal, it is less susceptible to co-channel NTSC interference.
1992年2月11日发布授与RWCitta等人的美国专利，号码为5087975的说明书和附图结合在这里作为参考，其名称为“减少NTSC同频道干扰的VSBHDTV发射系统”。 February 11, 1992 release granted RWCitta et al. US Patent Number 5,087,975 for the specification and drawings incorporated herein by reference, entitled "Reducing NTSC co-channel interference VSBHDTV launch system." Citta等人描述了一种用于广播电视的电视信号发射信号，它包括一个抑制载波，一个VSB信号和一个导频信号，VSB信号在6MHz带宽的电视频道的上、下频率边缘各有一个Nyquist斜率，该频道下频率边缘的Nyquist斜率的中心频率基本与抑制载波的频率一致，导频信号与抑制载波相差90°。 Citta et al describes a television signal transmission method for broadcast television signals, comprising a suppressed carrier, VSB signal and a pilot signal a, the VSB signal in the bandwidth of 6MHz television channel, each lower edge of a Nyquist frequency the slope of the center frequency, the frequency of the lower edge of the Nyquist slope of the channel substantially coincides with the frequency of the suppressed carrier, the carrier pilot signal to suppress a difference of 90 °. 该电视信号发射信号易受视频载波在该频道下频率边缘上面1.25MHz、彩色副载波在视频载波频率上面3.58MHz、和音频载波在该频道上频率边缘下面0.25MHz的NTSC电视信号的同频道干扰。 The television signal transmitting video signal susceptible to carrier frequency at the edge of the upper channel of 1.25 MHz, the color subcarrier frequency above the video carrier 3.58MHz, and below the edge of the audio carrier frequency 0.25MHz for NTSC television signals on the same channel interference channel . 抑制载波由N级数字编码信号调制，该数字编码信号的采样速率fs基本等于NTSC彩色副载波频率的3倍，抑制载波的频率比同频道NTSC图像载波更接近频道的下频率边缘约fs/12。 Suppressed carrier from the N-level digitally encoded signal modulation, the sampling rate fs of the digital encoded signal is substantially equal to three times the NTSC color subcarrier frequency, suppressing frequency carriers closer to the band edge by about fs channel than the co-channel NTSC picture carrier / 12 . 接收到的信号由同步检测器响应接收到的导频信号解调，而干扰NTSC拍频分量由一个在fs/12、5fs/12和fs/2处具有陷波的线性滤波器衰减。 Received by the synchronization signal detector in response to the received pilot signal demodulation, the beat frequency component NTSC interference filter having a linear attenuation notch at / at fs / 12,5fs / 12 and fs 2 by one.
由高级电视系统委员会(ATSC)在1995年9月16日公布的数字电视标准规定了以例如在美国当前用于广播国家电视系统委员会(NTSC)空中广播模拟电视信号的6MHz带宽电视频道发射数字电视(DTV)信号的VSB信号。 By the Advanced Television Systems Committee (ATSC) digital television standard in 1995 September 16 announced the launch of the provisions of the order, for example, the bandwidth of 6MHz television channel in the United States is currently used for broadcast National Television System Committee (NTSC) analog-air broadcast television signals of digital television VSB signal (DTV) signals. 这些VSB信号与Citta等人描述的信号的不同之处在于，每一信号使用与其抑制载波同相的一个导频信号，而不是相差90°。 These difference signals VSB signal and Citta et al described that each pilot signal using a carrier with its inhibition of the pilot signal phase, rather than a difference of 90 °. 这些VSB信号中每一个包括一个接近电视广播频道的较低上频率边缘的残留边带，和从其频率向上延伸到该频道的上频率边缘的全边带。 The VSB signal each comprises a vestigial sideband frequency close to a lower edge of the television broadcast channel, and the frequency of the full sideband frequency edge extending upwardly therefrom to the channel.
本发明针对电视信号发射信号的发射，该发射信号包括一个抑制载波，一个与抑制载波同相的导频信号，和一个VSB信号，该VSB信号残留边带接近电视广播频道的上频率边缘，而其全边带接近该频道的下频率边缘。 The present invention is directed to transmit television signals transmitted signal, the transmitted signal comprising a suppressed carrier, guiding a same with a suppressed carrier phase pilot signal, and a VSB signal, the VSB signal is vestigial sideband approaching the television broadcast frequency of the channel edge, while the full frequency sideband of the channel closer to the lower edge. 抑制载波由一个N级数字编码信号调制，该数字编码信号具有基本等于NTSC彩色副载波频率3倍的采样速率fs，抑制载波的频率比同频道NTSC图像载波远离该频道下频率边缘大约5fs/12。 Suppressed carrier consists of a N-level digitally encoded signal modulation, the digitally encoded signal having substantially equal to the NTSC color subcarrier frequency three times the sampling rate fs, inhibition frequency of the carrier away from the frequency of the lower edge of the channel about 5fs / 12 ratio of co-channel NTSC picture carrier . 接收到的信号可以由一个同步检测器响应接收到的导频信号解调，而干扰NTSC拍频分量由一个在fs/12、fs/4、和5fs/12处具有陷波的线性滤波器衰减。 The signal received by the response received by a synchronous detector demodulating a pilot signal, and the beat frequency component in the interfering NTSC fs / 12, fs / 4, and at 5fs / 12 linear notch filter having the attenuation of a .
因此，根据本发明，提供一种通过一个经常出现同频道NTSC模拟电视信号的频道发射数字电视信号的方法，所述同频道NTSC模拟电视信号具有一个调制视频载波、一个调制彩色副载波、和一个调制音频载波，所述方法包括步骤：以基本等于3倍NTSC彩色副载波频率的一个符号速率fs提供一个N级数字编码信号，N是一个复整数(plural integer)；产生一个频率在NTSC音频载波几百千周内的载波信号；用所述N级数字编码信号调制所述载波信号的振幅，产生第一和第二调幅边带；响应所述调幅边带形成发射信号，其中所述形成发射信号的步骤包括子步骤：抑制所述发射信号中所述调幅边带延伸出所述频道的任何部分，从而使所述第一调幅边带成为一个残留边带，只为频率接近所述载波信号的所述第二调幅边带的部分提供一个图像；相对于所述第二调幅边带在频率上离 Thus, according to the present invention, there is provided a frequent by a co-channel NTSC analog television channel signals transmitting digital television signals, said modulated video carrier having a co-channel NTSC analog television signal, a modulated color subcarrier, and a modulated audio carrier, said method comprising the steps of: substantially equal to three times the symbol rate of a NTSC color subcarrier frequency fs to provide a N-level digitally encoded signal, N being a plural integer (plural integer); generating a frequency in the NTSC audio carrier several hundred one thousand carrier signals weeks; the amplitude of the N-level digitally encoded signal modulating the carrier signal, generating first and second sideband AM; AM sideband formed in response to the transmit signal, wherein the transmitter is formed signal comprises the substeps of: transmitting signals in the suppression of the sideband amplitude any portion extending out of the channel so that the amplitude of the first sideband as a vestigial sideband, only a frequency close to the carrier signal the second amplitude modulation sidebands of a part image; relative to the second sideband amplitude modulated in frequency from 所述载波信号的剩余部分的振幅响应，对分所述残留第一边带和所述第二调幅边带频率接近所述发射信号中的所述载波信号的所述部分的振幅响应。 Amplitude response of the remaining portion of the carrier signal, to the remaining portion of said first sideband amplitude modulation and the second sideband frequency amplitude response of the proximity of the carrier signal portion of the transmit signal.
图1是根据本发明构造的一个电视信号发射系统的方框图；图2表示根据本发明发射DTV时6MHz的DTV电视频道的频谱图；图3表示根据本发明发射DTV时DTV接收机对同频道DTV和NTSC发射的响应；图4是用于图1的DTV接收机中的一个逆Hilbert变换滤波器的方框图。 FIG. 1 is a block diagram of a television signal transmission system constructed in accordance with the present invention; FIG. 2 shows the emission spectrum when the present invention DTV DTV 6MHz television channel; Figure 3 shows a DTV transmitter in accordance with the present invention, when the DTV receiver to co-channel DTV and in response to the transmitted NTSC; FIG. 4 is a block diagram showing a DTV receiver in FIG. 1 an inverse Hilbert transform filter is used.
本发明说明的问题在图1的方框图中一般表示出来。 Problem of the present invention is illustrated in FIG. 1 is a block diagram generally represented. 用参考标号10总体表示的DTV发射机通过一个选择的6MHz宽的电视频道广播一个DTV编码信号，用于调谐到该选择频道的一个相应DTV接收机100接收和重放。 DTV transmitter indicated generally by the reference numeral 10 through 6MHz television channel is broadcasting a wide choice of encoding a DTV signal receiver 100 for tuning to a corresponding DTV receiver and playback of the selected channel. 同时，一个NTSC发射机200通过在附近的电视服务区域内的同一频道广播一个NTSC编码信号。 At the same time, an NTSC transmitter 200 through an NTSC encoded signal in the vicinity of the service area of the television channel broadcasting the same. 取决于各种因素，包括其物理位置，DTV接收机100因此可能接收到除从DTV发射机10的发射天线20接收希望的信号之外还从NTSC发射机200的发射天线201接收具有相当强度的不希望的干扰分量。 Depends on various factors including its physical location, thus DTV receiver 100 may receive from the DTV transmitter other than the transmitting antenna 10 receives the desired signal 20 is also transmitted by the transmitter antenna 200 from NTSC 201 received considerable strength unwanted interference components. 由于不希望的干扰信号在和希望的DTV信号同一频道上发射，因此通常称为“同频道干扰”。 Since the undesired interfering signal is transmitted on the same DTV signal and a desired channel, it is often referred to as "co-channel interference." 在DTV接收机中的同频道干扰信号特别在使用全数字DTV发射标准的场合引起问题。 Co-channel interference in a DTV signal receiver of particular use in the case of transmitting digital DTV standards cause problems. 特别是，如果同频道干扰信号具有足够强度压倒接收机中的数字DTV信号的话，则接收机重放任何质量图像的能力完全受损。 In particular, if a digital signal of sufficient strength overwhelm DTV receiver co-channel interference signals, then the ability of any receiver replay image quality is completely damaged. 此外，DTV接收机的这一损害随干扰NTSC同频道信号的强度变化可能相当突然地发生。 In addition, the damage of the DTV receiver with co-channel NTSC interference signal intensity variations may occur quite suddenly. 这与模拟DTV系统不同，在模拟DTV系统中干扰NTSC同频道信号的强度变化引起接收机的信噪比性能上逐渐改变。 This DTV analog systems, analog DTV system co-channel interfering NTSC signal intensity variation cause gradual changes in signal to noise performance of the receiver.
如所周知，干扰NTSC同频道信号的频谱占据一个6MHz宽的电视频道，它包括一个亮度分量，一个色度分量和一个音频分量。 As is known, co-channel interfering NTSC spectrum signal occupies a 6MHz wide television channels, comprising a luminance component, a chroma component and an audio component. 亮度分量的带宽大约为4.2MHz并调制在距该频道一端1.25MHz的一个图像载波上。 The bandwidth of the luminance component is about 4.2MHz and modulated on a picture carrier of 1.25MHz from one end of the channel. 色度分量的带宽大约1MHz，调制在距图像载波3.58MHz的一个副载波上。 The bandwidth of the chrominance component of approximately 1MHz, the modulated subcarriers from a picture carrier of 3.58MHz. 音频分量调制在距该频道另一端0.25MHz(亦即距图像载波4.5MHz)的一个载波上。 Modulation on an audio component from the other end of 0.25MHz channel (i.e. 4.5MHz from the picture carrier) of a carrier. 同频道干扰的主要来源是相对大的NTSC图像载波及其编码同步信息的边带，以及高亮度图像分量彩色突发脉冲串，在高色度图像分量期间的色度副载波边带和FM音频载波。 The main sources of co-channel interference are the relatively large NTSC picture carrier and its sidebands code synchronization information, and a high-luminance image component of the color bursts, during high-chrominance image components and chrominance subcarrier FM audio sidebands carriers.
在同步间隔期间的NTSC图像载波尖峰提供最大能量的同频道干扰。 Providing the maximum energy peak in the NTSC picture carrier during a sync interval co-channel interference. 当使用梳状滤波抑制NTSC同频道干扰时，希望把梳状滤波设计为最佳抑制NTSC视频载波及其15734Hz的边带的假像(artifacts)。 When using comb filtering to suppress NTSC co-channel interference, it is desirable to design the optimum comb filtering to suppress NTSC video carrier and 15734Hz sideband of artifacts (artifacts). 色度突发脉冲只有NTSC图像载波尖峰在同步间隔期间能量的20％或更少。 Chroma burst is only 20% NTSC picture carrier energy spikes during synchronization interval or less. 梳状滤波可以抑制描述大面积图像的NTSC亮度和色度信号的假象。 Comb filtering to suppress artifacts may be described in a large area of the image NTSC luminance and chrominance signals. 由描述图像运动边缘的NTSC亮度和色度信号的假象引入的误差必须使用误差修正码修正。 Error introduced by the edge of the image motion artifacts described NTSC luminance and chrominance signals using the error correction code must be corrected.
虽然视频载波峰值调制的振幅被限制为大约7-10％，FM音频载波的振幅不变。 Although the amplitude modulated video carrier peak is limited to about 7-10%, FM audio carrier amplitude is unchanged. 这使得很难使用误差修正码修正由FM音频载波引入的误差。 This makes it difficult to error correction using an error correction code introduced by the FM audio carrier. NTSC音频载波的调频和调相使梳状滤波使用多个符号固定相位延迟的微分延迟，这对抑制NTSC音频信号的假象不实际。 NTSC audio carrier frequency modulation and phase modulation so that a plurality of comb filtering using a fixed symbol delay differential phase delay, which suppress NTSC artifacts of the audio signal is not practical. 调制信号在音频处改变和低超声速率提供在仅相距几个信号固定相位延迟的样本之间足够相关这一事实允许为ATSC信号使用12符号微分延迟梳状滤波器，使抑制NTSC音频信号的假象获得一定的成功。 Modulated audio signal and the change rate between a low ultrasound signal are only a few samples of a fixed phase delay associated fact sufficient to allow the use of 12 symbol differential delay comb filter is an ATSC signal, so that an audio signal to suppress NTSC artifacts with some success.
图2表示根据本发明的一个DTV发射频道的频谱。 Figure 2 shows the emission spectrum of a channel of the DTV of the present invention. 该频道6MHz宽，相应于一个发射VSB信号的NTSC发射频道，如图所示。 The channel 6MHz wide, corresponding to an NTSC transmission channel transmitting VSB signal, as shown in FIG. 更特别的是，在低于第一断点频率f1bp不大于距该发射频道的下频率边缘353KHz左右，发射频道显示振幅响应滚降22。 More particularly, the transmitting frequency channel at an edge below the first breakpoint frequency f1bp distance no greater than about 353KHz, transmission channel amplitude response rolls off the display 22. VSB信号具有基本平坦的振幅响应部分24，它从第一断点频率f1bp延伸到第二断点频率f2bp，距发射频道的下频率边缘略小于5,643KHz左右。 VSB signal having a substantially flat amplitude response part 24, which extends from the first breakpoint breakpoint frequency to a second frequency f1bp f2bp, from the edge of the transmission channel at a frequency slightly less than about 5,643KHz. 距发射频道下频率边缘1,250,00Hz处的一个同频道干扰NTSC信号的图像载波频率fpix处于由该基本平的振幅响应部分24包括的频率范围内。 A transmit frequency from a channel at the edge of 1,250,00Hz co-channel interfering NTSC signal picture carrier frequency fpix portion 24 is within a frequency range that includes a substantially flat amplitude response. 距发射频道下频率边缘4,829,545.5Hz的同频道干扰NTSC信号的色度副载波fsc也最好处于该频率范围内。 From a transmit frequency channel edge co-channel interfering NTSC 4,829,545.5Hz chrominance subcarrier signal fsc is also preferably within the frequency range. 在第二断点频率f2bp和第三断点频率f3bp之间，发射频道显示振幅响应滚降26，到基本平振幅响应部分24的振幅响应的一半，而从第三断点频率f3bp到第四断点频率f4bp作为另一基本平振幅响应部分28平分基本平振幅响应部分24。 Between the second and third breakpoint frequency f2bp f3bp breakpoint frequency, amplitude response of the transmission channel roll-off display 26, a substantially flat amplitude response to the amplitude response of the half portion 24, from the third to the fourth break point frequency f3bp as another f4bp breakpoint frequency amplitude substantially flat portion 28 substantially bisecting the flat section 24 in response to the amplitude response. 这一平分指的是调制程度，而不是能量。 This means that bisects the degree of modulation, rather than energy.
DTV信号的抑制载波频率fc和导频信号频率fp两者都在距发射频道下频率边缘略小于5734KHz处，将它们定位于NTSC图像载波频率fpix上面略小于285倍NTSC水平扫描频率fh处。 Suppressed carrier frequency fc and both the pilot signal DTV pilot signal frequency fp edges are slightly less than the frequency at 5734KHz from the transmission channel, they are positioned above the NTSC picture carrier frequency fpix slightly less than 285 times the NTSC horizontal scanning frequency fh. 之所以这样做是为了最好地容纳接收机100中的梳状滤波以抑制同频道干扰NTSC信号的图像载波频率fpix和色度副载波fc的假象。 This is done in order to best accommodate the receiver 100 comb filtering to suppress co-channel interference artifacts picture carrier fpix and chrominance subcarrier frequency fc NTSC signal. DTV信号的抑制载波频率fc和导频信号频率fp位于相应于基本平振幅响应部分28的频率范围的中心。 Carrier frequency fc and suppressed conductivity DTV signal frequency fp of the pilot signal is located substantially corresponding to the amplitude level of the center portion of the frequency range of 28 response. 基本平振幅响应部分28延伸以包括同频道干扰NTSC信号的调频音频载波fa及其相当大能量的调频边带。 Portion 28 extends substantially in response to the amplitude of the FM audio carrier fa comprises co-channel interference of the NTSC signal and the FM sideband considerable energy level. 相应地，第四断点频率f4bp位于距发射频道下频率边缘5,825,000Hz或稍高处。 Accordingly, the fourth break point frequency f4bp located slightly higher frequency or at a lower edge 5,825,000Hz from the transmission channel. 在第四断点频率f4bp之上，发射频道显示振幅响应滚降30。 Over the fourth breakpoint frequency f4bp, transmission channel amplitude response rolls off the display 30. 第三断点频率f3bp低于抑制载波频率fc的频率正如第四断点频率高于抑制载波频率fc。 F3bp third breakpoint frequency below fc is a carrier frequency suppressed as a fourth breakpoint frequency is higher than the carrier frequency fc suppressed. 在第二断点频率f2bp和第三断点频率f3bp之间的振幅响应滚降26设计为补全振幅响应倾斜30，使得当电视信号发射信号在接收机100中解调时，基带DTV信号具有一个从0频率向上到Nyquist采样频率fs的一半-亦即5,381,118.9的平振幅响应。 Amplitude between the second and third breakpoint breakpoint frequency f2bp f3bp frequency response roll-off 26 is designed to complement the amplitude response 30 is inclined, so that when the television signal is demodulated in the transmitting signal receiver 100, the baseband DTV signal having from 0 up to a half of the Nyquist frequency of the sampling frequency fs - i.e. flat amplitude response of 5,381,118.9. 发射机相位响应在从距发射频道下频率边缘低于353KHz左右处到振幅响应滚降30在高频能量减少到可忽略的频率之间的范围内保持为直线，使得分散的(absent)多路径现象在由接收机100解调的DTV信号分量中有一致的组延迟。 At a transmitter from the phase response from the transmission channel frequencies below about 353KHz edge roll-off in response to the amplitude is reduced to 30 to maintain a straight line within a range between the frequency of the high-frequency energy may be negligible, so that the dispersion (Absent) multipath phenomenon delay component 100 by the demodulated DTV signal receivers have the same group.
如美国专利，号码为5,087,975指出，频道的Nyquist带宽fs/2可以认为被等分为6部分，在同频道NTSC图像载波fpix和彩色副载波fsc之间的间隔相应于6部分中的4部分，亦即fsc-fpix＝(4/6)(fs/2)＝(4/12)fs＝(1/3)fs。 U.S. Patent Number 5,087,975 is indicated, the Nyquist bandwidth of fs channel / 2 may be considered to be divided into six parts, the spacing between the co-channel NTSC picture carrier fpix and color subcarrier fsc portion 6 corresponding to the portion 4, i.e. fsc-fpix = (4/6) (fs / 2) = (4/12) fs = (1/3) fs. Nyquist信号频率开始时假定为3倍的(fsc-fpix)＝3*3,579,545.5Hz＝10,738,636.4Hz。 Nyquist frequency is assumed at the beginning of the signal 3 times (fsc-fpix) = 3 * 3,579,545.5Hz = 10,738,636.4Hz.
与美国专利5,087,975所示的不同，在DTV信号的抑制载波频率fc和同频道NTSC图像载波fpix之间的间隔相应于6部分中的5部分，而不只是6部分中的1部分，在DTV信号的抑制载波频率fc和同频道NTSC彩色副载波fsc之间的间隔只相应于6部分中的1部分，而不是6部分中的5部分，亦即fc-fpix＝(5/6)(fs/2)＝(5/12)fs，和fc-fsc＝(1/6)(fs/2)＝(1/12)fs。 Unlike shown in U.S. Patent 5,087,975, the spacing between the carrier frequency fc and suppressing co-channel NTSC picture carrier FPIX DTV signal corresponding to the portion 6 of the section 5, rather than just a portion of the section 6, the DTV signal the suppression interval between the carrier frequency fc and a co-channel NTSC color subcarrier fsc only a portion corresponding to the portion 6, instead of 5 parts of section 6, i.e., fc-fpix = (5/6) (fs / 2) = (5/12) fs, and fc-fsc = (1/6) (fs / 2) = (1/12) fs.
图3表示DTV接收机100的基带响应。 3 shows a DTV receiver 100 the baseband response. 如图所示，DTV接收机的标称响应40在频道内基本是平坦的，容纳了fs/2的Nyquist带宽，而无衰减。 Nominal DTV receiver shown in FIG. 40 in response to the channel is substantially flat, receiving a Nyquist bandwidth of fs / 2, and without attenuation. 基带DTV信号最好由一个“同相”同步检测器响应于一个具有相应于抑制DTV载波fc的频率和相位的再生成载波而产生。 The baseband DTV signal is preferably by a "phase" in response to a synchronous detector corresponding to suppress regenerated carrier frequency and phase of the carrier wave fc DTV has generated. 在NTSC同频道信号出现时，检测器响应于再生载波也可提供一对干扰拍频信号，其频率基本相应于分别来自同频道NTSC干扰的色度副载波和视频载波的fs/12和5fs/12。 When co-channel NTSC signal is present, the detector responsive to the reproduced carrier also may provide an interference beat signal whose frequency substantially corresponds to the co-channel NTSC interference are from the fs chrominance subcarrier and the video carrier / 12 and 5 fs / 12. 干扰拍频信号在图3中分别用参考标号42和44表示。 Interference beat signal, respectively in FIG. 3 by reference numerals 42 and 44 represent. 另一个拍频信号46稍微高于0频率处，它作为NTSCFM音频载波的假象出现在“同相”同步检测器响应中。 Another beat signal 46 at a frequency slightly higher than 0, it appears as artifacts in the audio carrier NTSCFM "in-phase" sync detector response. 附加结合具有合适微分延迟的基带DTV信号的梳状滤波器，其响应为50，其内具有零点52、54和56。 Combined with suitable additional differential delay comb filters the baseband DTV signal in response to 50, 52, 54 and the inner 56 having a 0:00. 零点54接近中频道，它把中频道振铃响应减少到脉冲噪声。 0:54 close the channel, the channel in which the reduced ringing in response to impulse noise. 作为同频道NTSC干扰的色度副载波和视频载波假象的拍频信号42和44被梳状滤波器响应50中的零点52和56抑制。 As the co-channel NTSC interference and the video carrier chrominance subcarrier artifacts beat signals 42 and 44 are comb filter response and 0:52 56 50 inhibition. 后面还要详细说明，接收机100包括一个具有响应50的梳状滤波器，用以减少同频道干扰拍频的效果。 Also described in detail later, receiver 100 includes a comb filter 50 has a response, to reduce the effect of co-channel interference beat frequency.
ATSC数字电视标准使符号速率fs为NTSC水平扫描速率fh的684倍，以方便在NTSC和DTV编码信号之间的变换，如美国专利，号码为5,087,975所建议的。 ATSC digital television standard that the symbol rate fs 684 times the NTSC horizontal scanning rate fh to facilitate conversion between NTSC and DTV signal encoding, as described in U.S. Patent Number 5,087,975 is recommended. 相应地，附加结合微分延迟为6符号间隔的采样信号的线性梳状滤波器提供分别在接近拍频信号42和44频率处的陷波52和56。 Accordingly, in conjunction with additional differential delay is a linear comb filter 6 sampled signal symbol interval, respectively, provided near the notch frequency beat signals 42 and 44 at a frequency of 52 and 56. 由于NTSC水平扫描行精确具有684个符号，因此6符号延迟将比一个NTSC扫描行短114倍。 Since the NTSC horizontal scanning line having exactly 684 symbols, so a 6-symbol delay than 114 times NTSC scan line short. 具有频率为114*fh的假象在6符号期间具有一个完整周期，所以附加结合微分延迟6符号间隔的采样信号的梳状滤波器以1793706.3Hz的间隔出现陷波。 114 * fh having the frequency of the illusion of having a full cycle during a 6 symbols, the comb filter in conjunction with an additional sample signal 6 symbol interval differential delay occurred at intervals 1793706.3Hz the notch.
如果视频载波频率fpix准确落入位于(5/2)*1,793,706.3Hz的陷波，则DTV载波频率fc将在视频载波频率fpix上面(5/2)*1,793,706.3Hz处，亦即在该频道的下频率极限上面1,250,000Hz。 If the video carrier frequency fpix accurately dropped into the (5/2) * 1,793,706.3Hz notch, the DTV video carrier frequency fc at carrier frequency fpix the above (5/2) * 1,793,706.3Hz place, i.e. at the channel frequency limit above 1,250,000Hz. 这就是说，DTV载波频率fc将在该频道的下频率极限上面5,734,265.7Hz和在6MHz宽频道的上频率极限下面265,734.3Hz处。 That is, DTV carrier frequency fc the frequency limit above 5,734,265.7Hz at the channel frequencies and limits on the following 265,734.3Hz 6MHz wide channels. 这将把DTV信号载波频率fc置于和NTSC音频载波频率fa相距fh的水平频率处，以致即使其声音电路的调幅(AM)抑制很差，DTV信号载波在NTSC电视信号接收机中也听不见。 This will put the DTV signal carrier frequency fc and fa away from NTSC audio carrier frequency fh of the horizontal frequency, so that even if the sound amplitude modulation circuit (AM) poor inhibition, the DTV signal carrier not hear the NTSC television signal receiver . 解决这一问题的办法是，如果DTV信号载波频率fc具有和NTSC音频载波频率fa相距fh水平频率位移的话，则在NTSC同频道干扰信号中的立体声导频载波的第一上边带有助于影响DTV载波频率在DTV接收机中获得。 The solution to this problem is the first top if the DTV signal carrier frequency fc and has the NTSC audio carrier frequency fa fh apart horizontal frequency shift, then the stereo pilot in the NTSC co-channel interference signal carrier frequency with help influence DTV carrier frequency in the DTV receiver.
优选DTV载波频率fc稍低于例如6MHz宽频道下频率极限上面5,733,500Hz和该频道上频率极限下面266,500Hz处。 DTV preferably slightly below the carrier frequency fc e.g. channel frequency 6MHz wide frequency upper limit below an upper limit 5,733,500Hz 266,500Hz and the channel. 这使得在DTV载波频率fc和在NTSC同频道干扰信号的立体声导频载波的第一上边带之间的拍频约为765Hz，使其可以被载波再生电路的AFPC信号中的一个窄带滤波器抑制。 This makes the Sign in carrier frequency fc between the DTV and the upper band in a first stereo pilot signal of NTSC cochannel interference frequency carrier frequency of about 765Hz, it can be suppressed AFPC signal carrier reproduction circuit in a narrow band filter . DTV信号载波在NTSC电视信号接收机中仍然听不见，即使其声音电路的调幅(AM)抑制很差。 DTV signal carrier remain inaudible in the NTSC television signal receiver, even if the sound amplitude modulation circuit (AM) poor suppression.
DTV载波频率fc可以置于同频道NTSC色度副载波频率之下57*fh处，其为6MHz宽频道上频率极限下273,602Hz处。 DTV carrier frequency fc can be placed in the same channel at 57 * fh under the NTSC chrominance subcarrier frequency, which at the lower limit frequency is 6MHz wide track 273,602Hz. 如果立体声NTSC电视信号接收机的声音电路的调幅(AM)抑制很差的话，则DTV信号载波可能在具有立体声声音的NTSC电视信号接收机内引起7867Hz的音调。 7867Hz tone caused in the NTSC television signal receiver circuit if the stereo sound NTSC television signal receiver of amplitude modulation (AM) inhibition poor, then the DTV signal carrier may have a stereo sound. DTV接收机内的DTV载波频率的获得不受同频道NTSC立体声导频信号的影响，而色度边带被最好抑制。 DTV carrier frequency is obtained within a DTV receiver is not affected by co-channel NTSC signal is a stereo pilot chrominance sideband suppression is the best. 同频道NTSC视频假象距用于抵制NTSC假象的梳状滤波器的陷波频率fh/2。 Notch frequency fh artifacts of co-channel NTSC video artifacts from NTSC to counteract comb filter / 2. 使用6符号微分延迟的梳状滤波器在包括陷波频率的71kHz范围提供-18dB衰减，使同频道NTSC视频载波假象的衰减仍然相当好。 6 using symbol differential delay in the comb filter comprises a notch frequency range 71kHz -18dB attenuation provided, so that co-channel NTSC video carrier attenuation artifacts is still quite good. 然后同频道NTSC视频载波假象也可以由除梳状滤波器以外的方法清除，因为到750KHz的NTSC双边带特性允许其从VSB DTV信号中分离。 Then also be cleared by a method other than the comb filter of the co-channel NTSC video carrier artifacts, because the NTSC double-sideband characteristic allows it to be separated from 750KHz VSB DTV signal.
按照上述并回过来参考图1，DTV发射机10包括一个视频信号源11，它从时钟发生器12接收时钟信号fs以符号速率fs提供一个数字视频信号，该数字视频信号的带宽达到37MHz，fs标称为3fsc。 Comprising a video signal source 11, which provides according to 1, DTV transmitter 10 described above with reference to FIG from and back to clock generator 12 receives a clock signal at a symbol rate fs fs a digital video signal, the bandwidth of the digital video signal reaches 37MHz, fs nominal 3fsc. 符号速率假定为NTSC水平速率fh的684倍。 684 times the symbol rate is assumed to the NTSC horizontal rate fh. 作为一个例子，由视频信号源11提供的视频信号包括每祯787.5条逐次扫描线，其中720条表示活动视频，其具有相应于NTSC场速率的垂直重复速率和相应于NTSC水平扫描速率3倍的水平重复速率。 As an example, the video signal supplied from the video signal source 11 includes every Zhen 787.5 successive scan lines, where 720 represents the active video, with corresponding to the NTSC field rate vertical repetition rate and corresponding to the NTSC horizontal scanning rate of 3 times the level of repetition rate. 由视频信号源11产生的视频信号输入到一个视频压缩器13上，它充分压缩37MHz的视频信号使其能够通过一个6MHz带宽的电视频道发射。 Input video signal generated by the video signal source 11-1 13, it is fully compressed 37MHz video compressor so that it can transmit the video signal through a 6MHz television channel bandwidth. 然后被压缩的视频信号可以在误差修正编码(ECC)电路14中经受前向误差修正编码，而其ECC结果供给预编码电路15。 Then the compressed video signal may be corrected coding (ECC) circuit 14, the error correction coding before subjected to the error, while the ECC circuit 15 supplies the result of precoding. 根据在ATSC数字电视标准下接受的实践，ECC电路14包括一个Reed-Solomon编码器，其后有一个格栅编码器，并且预编码输入到在格棚编码结果中选择的符号。 According to accepted practice in the ATSC digital television standard, the ECC circuit 14 includes a Reed-Solomon coder followed by a trellis encoder and pre-encoded input to the symbol selected in the grid shelf coding results. 视频压缩器13、ECC电路14和预编码器电路15响应从时钟发生器12来的时钟信号fs而操作。 Video compressor 13, ECC circuit 14 and the pre-encoder circuit 15 operates from a clock generator 12 in response to a clock signal fs. 预编码电路15提供部分预编码的误差修正编码结果作为调制信号给残留边带调幅器16。 Pre-coding circuit 15 to provide some error correction coding the pre-coded result as a modulation signal to a vestigial sideband amplitude modulator 16. 载波和导频信号发生电路17给VSB调制器16供给一个载波信号，具有标称频率fh水平频率偏移低于相应的NTSC音频载波频率fa。 Supplying a carrier and a pilot signal generating circuit 17 to the VSB modulator 16 a carrier signal having a nominal horizontal frequency fh frequency offset lower than the corresponding NTSC audio carrier frequency fa. 载波和导频信号发生电路17还供给具有和载波信号同一频率和相位的一个频率fp的导频信号。 Carrier and a pilot signal generating circuit 17 is also supplied and a pilot signal having a same frequency and a phase of the carrier signal frequency fp. 导频信号与来自VSB调制器16的残留边带调幅输出信号在一个结合电路18中结合以形成一个加在末级放大电路19上的一个信号，用于驱动发射天线20。 Pilot signal vestigial sideband AM output signal from VSB modulator 16 is incorporated in a circuit 18 to form a combined signal applied to a last stage of the amplifier circuit 19, for driving the transmitting antenna 20. 视频信号作为一个N级数据采样序列发射，这一发射优选使用图2所示抑制载波、VSB信号的形式实现，其同相导频信号fp与其结合以便利在DTV接收机100内再生该载波。 Video signal as a sequence of N-level data samples emission, the emission is preferably used as shown in FIG. 2 suppressed carrier, VSB signal form of realization, with the relative conductivity in connection with the pilot signal fp to facilitate regeneration in the DTV receiver 100 of the carrier. 当然，时钟和载波信号的频率可以从上述标称值稍微调整。 Of course, the clock frequency of the carrier signal and can be adjusted slightly from the nominal value.
DTV接收机100包括一个接收天线101的调谐器和IF级102，它调谐到发射DTV信号的6MHz电视频道。 DTV receiver 100 includes a receiving antenna 101, a tuner and IF stage 102, which is tuned to transmit DTV signal 6MHz television channel. 被调谐的DTV信号，连同由在附近电视服务区域的发射机200在同一频道广播的同频道NTSC信号一起在102阶段中变换为中频，作为输入信号供给同相同步检测器103和90°相差同步检测器104。 Tuned DTV signal, along converted together with co-channel NTSC signal by the transmitter in the vicinity of the TV service area 200 in the same channel broadcasting in stage 102, an intermediate frequency, as an input signal supplied to the phase difference in-phase synchronous detector 103 and 90 ° synchronous detection 104. 载波再生电路105分别供给同相同步检测器103同相再生的载波和90°相差同步检测器104以90°相差的再生的载波。 The carrier reproducing circuit 105 is supplied with the carrier reproduction phase difference of 90 ° and the carrier sync detector 104 to a phase difference of 90 ° with the regeneration phase synchronous detector 103, respectively. 同步检测器103和104的基带响应供给频道均衡滤波电路106，它对从DTV发射机10接收的DTV信号抑制多路径响应，并均衡该频道以减少符号间误差。 Synchronization detector 103 and 104 in response to the supplied baseband channel equalization filter circuit 106, it suppressed DTV DTV signal received from the transmitter 10 in response to multipath, and equalize the channel in order to reduce inter-symbol errors. 来自频道均衡滤波电路106的延迟的、均衡的同相同步检测器103的响应供给时钟再生电路107，它再生符号时钟信号fs为整个DTV接收机100使用。 Delay from channel equalization filtering circuit 106, in response to supply of the clock-phase balanced synchronous detector 103 reproducing circuit 107 which is reproduced symbol clock signal fs entire DTV receiver 100 used.
低通滤波器108响应来自频道均衡滤波电路106的均衡的90°相差同步检测器104的响应以产生一个误差信号，该误差信号指示任何与由载波再生电路105提供给同相同步检测器103同相再生的载波和90°相差同步检测器104以90°相差再生的载波的正确频率和相位的偏离。 90 ° phase difference in response to the synchronous detector 104 to generate an error signal lowpass filter 108 response equalizer from the channel equalization filtering circuit 106, the error signal indicates any provided to and from the carrier reproducing circuit 105 with the phase synchronous detector 103 inphase reproduction 90 ° and the phase difference of the carrier sync detector 104 to a carrier reproduction phase difference 90 ° correct frequency and phase deviation. 这一误差信号进一步由AFPC滤波器109滤波，作为用于包含在载波发生电路105中的一个受控振荡器的自动频率和相位控制(AFPC)信号。 This error signal is further filtered by the AFPC filter 109, for containing as automatic frequency and phase control (AFPC) signal circuit 105 occurs in a controlled oscillator in a carrier wave.
来自频道均衡滤波电路106的均衡的90°相差同步检测器104的响应包含对VSB DTV信号的所有单边带分量的响应，其为对包含在来自频道均衡滤波电路106的均衡的同相同步检测器103响应中的VSB DTV的所有单边带(SSB)分量响应的Hilbert变换。 90 ° from the channel equalization filter in response to the equalization circuit 106 of the phase difference detector 104 comprises a synchronous response to all single sideband VSB DTV signal component, which is in-phase synchronous detector comprises a channel equalization in the equalizer from the filter circuit 106 103 in response to all of the VSB DTV SSB (SSB) in response to the Hilbert transform component. 低通滤波器108对来自频道均衡滤波电路106的均衡90°相差同步检测器104响应的响应供给逆Hilbert变换滤波器110，该逆Hilbert变换滤波器110相应于给VSB DTV信号的低频率SSB分量提供响应，除由逆Hilbert变换滤波器110引入的滞后或延迟外，其相似于均衡同相同步检测器103响应对低频率SSB分量的响应。 A low-pass filter 108 from equalization channel equalization filter circuit 106 is supplied in response to the phase difference of 90 ° in response to the sync detector 104 is an inverse Hilbert transform filter 110, the inverse Hilbert transform filter 110 corresponds to a low frequency component of the SSB signal to the VSB DTV provide a response, in addition to the inverse Hilbert transform filter 110 lag or delay introduced outside, which is similar to the same equilibrium phase synchronous detector 103 in response to the low frequency response SSB component. 来自频道均衡滤波电路106的均衡同相同步检测器103响应由延迟线111延迟，它补偿由滤波器108和110引起的滞后或延迟。 Equalization circuit 106 from the channel equalization filtering in-phase synchronous detector 103 in response to the delay by the delay line 111, which compensates for the lag or delay caused by the filter 108 and 110. 级联滤波器108和110的响应与延迟线111的响应在线性组合器112中结合以消除来自延迟的均衡同相同步检测器103响应的同频道NTSC音频信号的假象，延迟的均衡同相同步检测器103响应从线性组合器112供给梳状滤波电路和符号解码器电路113。 Cascade in response filter 108 and the delay line 111 in response to the linear combiner 112 110 binding to eliminate co-channel NTSC artifacts of the audio signal from the delayed equalized in-phase synchronous detector 103 in response to the delay equalizer with phase synchronous detector comb filter 103 in response to the supply circuit and a symbol decoder circuitry 113 from a linear combiner 112.
从线性组合器112供给的延迟均衡同相同步检测器103响应包括希望的DTV分量，在图3中用曲线40表示，和不希望的NTSC同频道视频和色度拍频分量，在图3中分别用信号42和44表示。 Supplied from the delay equalization of the linear combiner 112 in-phase synchronous detector 103 in response to the desired DTV components comprise, in FIG. 3 by curve 40 represents, and the undesired NTSC co-channel beat frequency and the chrominance component video, respectively, in FIG. 3 42 and 44 is represented by the signal. 如前所述，拍频分量在基本相应于fs/12和5fs/12频率处出现，并作为分别用NTSC视频载波和NTSC色度副载波差拍再生的DTV载波的结果。 As described above, the beat frequency component / 5 fs and 12/12 appeared at frequencies substantially corresponding to fs, and the results are as DTV carrier regenerated shoot the NTSC video carrier and the NTSC chrominance subcarrier difference. 符号解码器电路113中的数据切分由时钟发生电路107产生的符号时钟信号fs定时。 A data symbol decoder circuit 113 slicing symbol clock signal from the clock generation circuit 107 generates a timing of fs. 在确定NTSC同频道干扰存在时，符号解码器电路113可以在数据切分前用具有图3曲线48表示的响应的线性滤波器先行滤波。 In determining the presence of NTSC co-channel interference, the symbol decoder circuitry 113 may be a linear filter having a first filter response represented by curve 48 of FIG. 3 in the data before the segmentation. 该响应包括在相应于fs/12和5fs/12两者频率处的零响应以消除或基本消除NTSC干扰视频和色度拍频。 The response includes the corresponding fs / 12 and zero at both frequencies 5fs / 12 in response to eliminate or substantially eliminate the NTSC interference in the video and chroma beat frequency. 由这种在数据切分前使用的滤波引入的符号间干扰可以在由数据切分恢复的数据中补偿。 Inter-symbol interference introduced by the filtering used in such data before the data segmentation can be compensated by the recovery of data segmentation. 梳状滤波和符号解码器电路113最好是由发明人在其被许可的美国专利申请，序号为08/882539，申请日为1997年6月25日，名称为“检测和抑制NTSC同频道干扰的数字TV接收机电路”，中说明的类型，上述专利申请结合在此作为参考。 Comb filtering and symbol decoder circuit 113 is preferably by the inventor thereof is permitted in U.S. Patent Application Serial No. 08/882539, filed June 25, 1997, entitled "detect and suppress NTSC co-channel interference digital TV receiver circuit, "type described in the patent applications incorporated herein by reference.
由梳状滤波和符号解码器电路113恢复的数据供给误差修正电路114，它包括一个格栅解码器，其后接着一个Reed-Solomon解码器。 Error data supplied by the comb filtering and symbol decoder circuitry 113 to recover correction circuit 114, which includes a trellis decoder, which is followed by a Reed-Solomon decoder. 在梳状滤波和符号解码器电路113中的数据切分可以响应格栅解码器调整以实现最优Viterbi解码。 Comb filtering and data symbol decoder circuit 113 may be responsive to the segmentation trellis decoder adjusted to achieve optimum Viterbi decoder. 误差修正电路114提供修正的数据给扩展电路115以重建表示原来37MHz源视频信号的宽带视频信号。 Error correction circuit 114 provides the correction data to spreading circuit 115 to reconstruct the original signal indicates 37MHz broadband video source of the video signal. 重建的信号供给显示器116显示重建的图像。 The reconstructed signal is supplied to the display 116 displays the reconstructed image. 使用ATSC标准的视频压缩器13和扩展电路115遵循MPEG-II标准。 Using the ATSC standard video compressor 13 and the expansion circuit 115 follows the MPEG-II standard.
图4详细表示逆Hilbert变换滤波器110的一个特定结构，它包括部件1101-1107，该结构是优选结构，因为其滞后时间可以保持相当短。 FIG 4 shows in detail a specific structure an inverse Hilbert transform filter 110, which comprises components 1101-1107, the structure is a preferred structure because it can be kept relatively short lag time. 如果希望构建一个在基带处的逆Hilbert变换滤波器，则与获得90°低频相移关联的延迟长到不能接受。 If you want to build a long delay inverse Hilbert transform filter at baseband, and to obtain the 90 ° phase shift associated to low unacceptable. 因此，把低通滤波器108的响应在逆Hilbert变换滤波前在频率上向上变换，然后把逆Hilbert变换滤波的结果在频率上向下变换以提供在基带处的逆Hilbert变换的低通滤波器响应。 Thus, the response of the low pass filter 108 before the inverse transform Hilbert transform filtering in frequency direction, then the result of the inverse Hilbert transform filtering the down-converted in frequency to provide a low-pass filter at baseband inverse Hilbert transform response. 符号恒定相位延迟由地址计数器1101计数，以产生以模余算术表示的顺序地址来寻址一个正弦表只读存储器1102和一个余弦表只读存储器1103。 Symbol epoch counted by the address counter 1101 to generate sequential addresses to mold than an arithmetic expression of addressable sine table ROM 1102 and a cosine table ROM 1103. 正弦表ROM 1102响应其寻址产生一个频率大于6MHz(例如8071678Hz＝513/286倍4.5MHz)的数字载波波作为乘数输入信号供给数字乘法器1104。 ROM 1102 in response to the sine table to generate a digital address which is larger than a 6MHz frequency (e.g. 8071678Hz = 513/286 times 4.5MHz) as a multiplier of the carrier wave input signal supplied to the digital multiplier 1104. 连接数字乘法器1104以接收作为被乘数的低通滤波器108的响应，并向上变换该信号为双边带调幅数字载波波的调幅边带。 In response to a connection digital multiplier 1104 receives the multiplicand is the low-pass filter 108, the signal is converted to the carrier wave amplitude modulated double-sideband amplitude modulation sidebands numbers. 连接数字乘法器1104把该DSB AM数字载波供给有限脉冲响应(FIR)低通数字滤波器105作为输入信号。 Digital multiplier 1104 connected to the digital carrier DSB AM supplied finite impulse response (FIR) low-pass digital filter 105 as an input signal. 滤波器1105设计用于响应低频率AM边带以提供一个单边带调幅(SSB AM)数字载波波，但基本不响应上频率AM边带。 Filter 1105 is designed for low-frequency response to provide AM sideband amplitude modulated single sideband (SSB AM) digital carrier wave, the frequency response but does not substantially AM sidebands. 余弦表ROM 1103响应其寻址产生一个和从正弦表ROM 1102产生的数字载波波同频率的数字载波波，但相差为90°。 Cosine table ROM 1103 in response to its address and generate a digital sine table generated from the carrier wave ROM 1102 with a digital carrier wave frequency, but the difference is 90 °. 连接数字乘法器1106接收从余弦表ROM 1103产生的数字载波波作为其乘数输入信号和来自滤波器1105的SSBAM数字载波波响应作为被乘数输入信号。 Digital multiplier 1106 connected to receive the digital cosine table generated from the carrier wave ROM 1103 as its multiplier input signal from the digital filter 1105 and SSBAM carrier wave as a response to the multiplicand input signals. 连接数字乘法器1106将其积输出信号作为输入信号加在有限脉冲响应(FIR)低通数字滤波器1107，它响应积信号的一个基带下变换结果部分，同时抑制积信号的图像上变换结果部分到由余弦表ROM 1103供给的数字载波波的二次谐波的边带。 Digital multiplier 1106 is connected to the product output signal as an input signal is applied to a finite impulse response (FIR) low-pass digital filter 1107, responsive to a baseband down conversion result of the partial product signals, while suppressing the image conversion product signal results section supplied to the digital cosine table ROM 1103 by the carrier of the second harmonic wave of the sideband. 低通滤波器1107的基带响应是作为输入信号加在结合器112上的逆Hilbert变换低通滤波器110的响应。 A low pass filter 1107 baseband response is applied as an input signal in an inverse Hilbert transform combiner 112 in response to the low pass filter 110.
由ATSC数字电视标准规定的12个平行格栅码最好由6个平行格栅码代替。 Defined by the ATSC digital television standard code 12 is preferably replaced by a parallel grid 6 parallel grid codes. 然而，即使保持12个平行格栅码并使用具有12符号微分延迟的梳状滤波电路以抑制NTSC同频道干扰假象，但是把DTV载波放置在广播电视频道上极限频率附近利用VSB DTV信号接近其载波频率的双边带特性，允许更好抑制同频道NTSC声音信号假象。 However, even if the holding grid 12 parallel code using a filter circuit 12 having a comb symbol differential delay to suppress NTSC co-channel interference artifacts, but the carrier is placed on the DTV broadcast television channels using the VSB DTV signal is close to its limit near the carrier frequency double-sideband frequency characteristics, allowing for better suppression of co-channel NTSC sound signal artifacts.
在本发明优选实施例之外的一个实施例中，残留边带和全调幅边带频率接近发射信号中载波信号的部分的振幅响应相似于全调幅边带频率离开载波信号的剩余部分的振幅响应。 In a preferred embodiment of the present invention, embodiments other than the embodiment, and the vestigial sideband amplitude modulation sideband frequencies close to the full amplitude of the transmission signal part of the amplitude of the response in response to the carrier signal similar to leave the remaining portion of the carrier signal in the whole frequency sideband AM . 为获得为DTV基带信号的平振幅响应，可以把90°相差同步检测器响应的逆Hilbert变换的高频部分与同相同步检测器响应结构性结合。 To obtain a flat amplitude response DTV baseband signal, the high frequency portion may be 90 ° phase difference in response to the sync detector in combination with an inverse Hilbert transform in response to the same structural phase synchronous detector. 在该方法中遇到的频道均衡问题通过发射VSB DTV信号的优选方法避免。 Channel equalization problems encountered in the process is preferably avoided by VSB DTV signal transmitting method. 更多的滤波以修改频道响应的形状在广播发射机中进行，可以使在DTV接收机中的滤波更简单。 More filtering to modify the shape of the channel in response to a broadcast transmitter, the filter can be made in the DTV receiver easier.
上面叙述的是一个高清晰度电视发射系统，它大大减少NTSC同频道干扰而不明显影响DTV接收机性能。 Described above is a high definition television transmission system, which greatly reduces NTSC co-channel interference without significantly affecting the performance of the DTV receiver. 所示系统可用于高清晰度电视系统的多种类型数字处理格式。 The system shown may be a plurality of types of digital processing formats for high definition television system.
- 1.一种通过一个经常出现同频道NTSC模拟电视信号的频道发射数字电视信号的方法，所述同频道NTSC模拟电视信号具有一个调制视频载波、一个调制彩色副载波、和一个调制音频载波，所述方法包括步骤：以基本等于3倍NTSC彩色副载波频率的一个符号速率fs提供一个N级数字编码信号，N是一个复整数(plural integer)；产生一个频率在NTSC音频载波几百千周内的载波信号；用所述N级数字编码信号调制所述载波信号的振幅，产生第一和第二调幅边带；响应所述调幅边带形成发射信号，其中所述形成发射信号的步骤包括子步骤：抑制所述发射信号中所述调幅边带延伸出所述频道的任何部分，从而使所述第一调幅边带成为一个残留边带，只为频率接近所述载波信号的所述第二调幅边带的部分提供一个图像；相对于所述第二调幅边带在频率上离开所述载波信号的剩余部 1. A method of transmitting a digital television signal channel often a co-channel NTSC analog television signal, the modulated video carrier having a co-channel NTSC analog television signal, a modulated color subcarrier, and a modulated audio carrier, the said method comprising the steps of: substantially equal to three times the symbol rate of a NTSC color subcarrier frequency fs to provide a N-level digitally encoded signal, N being a plural integer (plural integer); generating a frequency in the NTSC audio carrier hundred one thousand weeks carrier signal; an amplitude of said N-level digitally encoded signal modulating the carrier signal, generating first and second amplitude modulation sideband; sideband amplitude modulated in response to said step of forming a transmission signal, wherein the transmitted signal comprises the sub-forming step: inhibit said transmission signal of said amplitude modulated sidebands extend any portion of the channel so that the amplitude of the first sideband as a vestigial sideband, only a frequency close to the second carrier signal a sideband amplitude modulated image portion; the remaining portion relative to the second sideband amplitude modulated on the carrier signal away from a frequency 分的振幅响应，对分所述残留第一边带和所述第二调幅边带频率接近所述发射信号中的所述载波信号的所述部分的振幅响应。 Amplitude response points, the remaining points of the first and second sideband amplitude modulation sideband frequencies close to the amplitude response of the carrier signal portion of the transmit signal.
- 2.根据权利要求1的方法，其中，产生的所述载波信号在频率上离开所述NTSC彩色副载波基本等于NTSC彩色副载波频率的四分之一以及离开所述NTSC彩色副载波基本等于NTSC彩色副载波频率的四分之五。 2. The method of claim 1, wherein said carrier signal generated in frequency away from the NTSC NTSC color subcarrier equal to substantially one-quarter and away from the NTSC color subcarrier frequency of the color subcarrier equal to substantially NTSC five quarters of the color subcarrier frequency.
- 3.根据权利要求1的方法，其中所述N级数字编码信号以684倍NTSC水平扫描频率的符号速率提供。 3. The method according to claim 1, wherein said N-level digitally encoded signal at a symbol rate 684 times the NTSC horizontal scanning frequency.
- 4.根据权利要求1的方法，其中所述形成发射信号的步骤进一步包括步骤：在所述发射信号中包括一个固定振幅的所述载波信号作为导频信号。 4. A method according to claim 1, wherein said forming step further comprises the step of transmitting a signal: said carrier signal comprises a constant amplitude as a pilot signal in the transmit signal.
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|Application Number||Priority Date||Filing Date||Title|
|US09047475 US6184921B1 (en)||1998-02-20||1998-03-25||Method for transmitting VSB digital TV with carrier frequency near co-channel NTSC audio carrier frequency|
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|CN1237064A true CN1237064A (en)||1999-12-01|
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|CN 99101247 CN1106116C (en)||1998-02-20||1999-01-26||Method for transmitting VSB digital TV|
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