Dorf, R C, Wan, Z, Lindsey Ill, J F, Doelitzsch, D F, Whitaker J, Roden, M.S., Salek, S, Clegg, A.H. " Broadcasting The Electrical Engineering Handbook Ed. Richard C. dorf Boca Raton CRC Press llc. 2000
Dorf, R.C., Wan, Z., Lindsey III, J.F., Doelitzsch, D.F., Whitaker J., Roden, M.S., Salek, S., Clegg, A.H. “Broadcasting” The Electrical Engineering Handbook Ed. Richard C. Dorf Boca Raton: CRC Press LLC, 2000
69 Richard C. Dorf Broadcasting Zhen Wan University of California, davis 69.1 Modulation and Demodulation Jefferson F. Lindsey Ill Modulation· Superhet outhern Illinois University at Modulation. Frequency-Shift Keying. M-ary Phase-Shift Keying. Quadrature Amplitude Modulation Dennis e delitzsch 69.2 Rad Standard Broadcasting(Amplitude Modulation). Frequency Modulation Jerry Whitaker 69.3 Television Systen anning Lines and Fields. Interlaced Scannin Martin s. roden Fields. Synchronizing Video Signals. Television Industry Standards. Transmission Equipment. Television Reception California State University 69.4 High-Definition Television Stanley Salek Proposed Systems Hammett edison 69.5 Digital Audio Broadca The Need for dab·DA Design Almon H. Clegg Background Technical and Source Encoding. System Example: I 69.1 Modulation and demodulation Richard C. Dorf and Zhen Wan Modulation is the process of sing the source information onto a bandpass signal with a carrier frequenc fe This bandpass signal is called the modulated signal s(n), and the baseband source signal is called the nodulating signal m(t). The modulated signal could be represented by (r)=Relg(t)ejo] (69.1) s(t)=R(t)cos [o t+0(t) s(t)=x(t) cos o t-y(t)sin o t (69.3) where O.= 2Tf The complex envelope is g(t)=R(t)eje(n= x(r)+iy(r) (694) and g(t)is a function of the modulating signal m(t). That is, g(t)=gIm(t)] c 2000 by CRC Press LLC
© 2000 by CRC Press LLC 69 Broadcasting 69.1 Modulation and Demodulation Modulation • Superheterodyne Technique • Pulse-Code Modulation • Frequency-Shift Keying • M-ary Phase-Shift Keying • Quadrature Amplitude Modulation 69.2 Radio Standard Broadcasting (Amplitude Modulation) • Frequency Modulation 69.3 Television Systems Scanning Lines and Fields • Interlaced Scanning Fields • Synchronizing Video Signals • Television Industry Standards • Transmission Equipment • Television Reception 69.4 High-Definition Television Proposed Systems 69.5 Digital Audio Broadcasting The Need for DAB • DAB System Design Goals • Historical Background • Technical Overview of DAB • Audio Compression and Source Encoding • System Example:Eureka-147/DAB 69.1 Modulation and Demodulation Richard C. Dorf and Zhen Wan Modulation is the process of impressing the source information onto a bandpass signal with a carrier frequency fc. This bandpass signal is called the modulated signal s(t), and the baseband source signal is called the modulating signal m(t). The modulated signal could be represented by s(t) = Re{g(t)ejwct} (69.1) or, equivalently, s(t) = R(t) cos [wct + q(t)] (69.2) and s(t) = x(t) cos wct – y(t) sin wct (69.3) where wc = 2pfc. The complex envelope is g(t) = R(t)ejq(t) = x(t) + jy(t) (69.4) and g(t) is a function of the modulating signal m(t). That is, g(t) = g[m(t)] Richard C. Dorf University of California, Davis Zhen Wan University of California, Davis Jefferson F. Lindsey III Southern Illinois University at Carbondale Dennis F. Doelitzsch 3-D Communications Jerry Whitaker Technical Press Martin S. Roden California State University Stanley Salek Hammett & Edison Almon H. Clegg CCi
Baseband circuits RF circuits I vo= R(O cos(o t+0(o i Modulated signal out adulation Circuit may e(t) Phase modulator FIGURE 69. 1 Generalized transmitter using the AM-PM generation technique Thus gl] performs a mapping operation on m(t). The particular relationship that is chosen for g(r)in terms of m(r) defines the type of modulation used. In Table 69.1, examples of the mapping function g( m) are given for the following types of modulation AM: amplitude modulation DSB-SC: double-sideband suppressed-carrier modulation FM: frequency modulation SB-AM-SC: single-sideband AM suppressed-carrier modulation SSB-PM: single-sideband PM SSB-FM: single-sideband FM SSB-EV: single-sideband envelope-detectable modulation SSB-SQ: single-sideband square-law-detectable modulation QM: quadrature modulation Modulation In Table 69. 1, a generalized approach may be taken to obtain universal transmitter models that may be reduced to those used for a particular modulation type. We also see that there are equivalent models which correspond to different circuit configurations, yet they may be used to produce the same type of modulated signal at their outputs. It is up to communication engineers to select an implementation method that will optimize perfor mance, yet retain low cost based on the state of the art in circuit development There are two canonical forms for the generalized transmitter. Figure 69. 1 is an AM-PM type circuit as described in Eq (69.2). In this figure, the baseband signal processing circuit generates R(o) and e(r) from m(o). The R and e functions of the modulating signal m(t) as given in Table 69. 1 for the particular modulation type desired. Figure 69.2 illustrates the second canonical form for the generalized transmitter. This uses in-phase and quadrature-phase(IQ)processing. Similarly, the formulas relating x(n) and yr) are shown in Table 69.1, and the baseband signal processing may be implemented by using either analog hardware or digital hardware with software. The remainder of the canonical form utilizes radio frequency(RF)circuits as indicated Any type of signal modulation(AM, FM, SSB, QPSK, etc )may be generated by using either of these two canonical forms. Both of these forms conveniently separate baseband processing from RF processing Superheterodyne Technique Most receivers employ the superheterodyne receiving technique(see Fig 69.3). This technique consists of either down-converting or up-converting the input signal to some convenient frequency band, called the intermediate frequency(IF)band, and then extracting the information(or modulation) by using the appropriate detector. This basic receiver structure is used for the reception of all types of bandpass signals, such as television, FM, AM, satellite, and radar signals. c 2000 by CRC Press LLC
© 2000 by CRC Press LLC Thus g[·] performs a mapping operation on m(t). The particular relationship that is chosen for g(t) in terms of m(t) defines the type of modulation used. In Table 69.1, examples of the mapping function g(m) are given for the following types of modulation: • AM: amplitude modulation • DSB-SC: double-sideband suppressed-carrier modulation • PM: phase modulation • FM: frequency modulation • SSB-AM-SC: single-sideband AM suppressed-carrier modulation • SSB-PM: single-sideband PM • SSB-FM: single-sideband FM • SSB-EV: single-sideband envelope-detectable modulation • SSB-SQ: single-sideband square-law-detectable modulation • QM: quadrature modulation Modulation In Table 69.1, a generalized approach may be taken to obtain universal transmitter models that may be reduced to those used for a particular modulation type. We also see that there are equivalent models which correspond to different circuit configurations, yet they may be used to produce the same type of modulated signal at their outputs. It is up to communication engineers to select an implementation method that will optimize performance, yet retain low cost based on the state of the art in circuit development. There are two canonical forms for the generalized transmitter. Figure 69.1 is an AM-PM type circuit as described in Eq.(69.2). In this figure, the baseband signal processing circuit generates R(t) and q(t) from m(t). The R and q are functions of the modulating signal m(t) as given in Table 69.1 for the particular modulation type desired. Figure 69.2 illustrates the second canonical form for the generalized transmitter. This uses in-phase and quadrature-phase (IQ) processing. Similarly, the formulas relating x(t) and y(t) are shown in Table 69.1, and the baseband signal processing may be implemented by using either analog hardware or digital hardware with software. The remainder of the canonical form utilizes radio frequency (RF) circuits as indicated. Any type of signal modulation (AM, FM, SSB, QPSK, etc.) may be generated by using either of these two canonical forms. Both of these forms conveniently separate baseband processing from RF processing. Superheterodyne Technique Most receivers employ the superheterodyne receiving technique (see Fig. 69.3). This technique consists of either down-converting or up-converting the input signal to some convenient frequency band, called the intermediate frequency (IF) band, and then extracting the information (or modulation) by using the appropriate detector. This basic receiver structure is used for the reception of all types of bandpass signals, such as television, FM, AM, satellite, and radar signals. FIGURE 69.1 Generalized transmitter using the AM-PM generation technique
TABLE 69.1 Complex Envelope Functions for various Types of Modulation Corresponding Quadrature Corresponding Amplitude and Mapping Functions Modulation Phase modulation Modulation x(r) e(r Remarks AM 1+m(t) 0m()> L m(r)>-l required for L Coherent detection required. u80,m()<o cos[D,m(t)] sin[Dm(o) 1 D m(r) NL D, is the phase deviation onstant(radian/volts) D, is the frequency deviation constant(radian/wolt-sec) )2+i(n)2 [m(/m(oI L Coherent detection required SSB-PM siMr画 e"sin(D m(nI Dm(r dD, m(oyo mo)do D, m(oyo SB-EVa ellaI +m(a) i l+mMnl [1+ m(r)] cos In[I +m(oll +[l +m(o]sin(ln[l +m(oll 1+ m(r) ±ln[+m(切 m(r)>-l is required so that the In will have a real value SSB-SQca+臧∥川1+ m(t>-1 is required n1=m( ±v1+m) siny-In(l+mt ±li[+m the In will have a real value m()+m2(t) (r) tarIm (t)/m, o) L Used in NtSC color tele. L=linear, NL=nonlinear, [ is the Hilbert transform(ie, -g0 phase-shifted version)of [-]. The Hilbert transform is x(t=x(* 1_1 aUse upper signs for upper sideband signals and lower signs for lower sideband si bIn the strict sense, AM signals are not linear because the carrier term does not satisfy the linearity(superposition) condition
© 2000 by CRC Press LLC TABLE 69.1 Complex Envelope Functions for Various Types of Modulation Corresponding Quadrature Corresponding Amplitude and Type of Mapping Functions Modulation Phase Modulation Modulation g[m] x(t) y(t) R(t) q(t) Linearity Remarks AM 1 + m(t) 1 + m(t) 0 *1 + m(t)* Lb m(t) > –1 required for envelope detection. DSB-SC m(t) m(t) 0 *m(t)* L Coherent detection required. PM ejDpm(t) cos[Dpm(t)] sin[Dpm(t)] 1 Dpm(t) NL Dp is the phase deviation constant (radian/volts). FM 1 NL Df is the frequency deviation constant (radian/volt-sec). SSB-AM-SCa m(t) ± jmˆ (t) m(t) ± mˆ (t) tan–1[± mˆ (t)/m(t)] L Coherent detection required. SSB-PMa ejDp[m(t)± jmˆ (t)] e7Dpmˆ(t ) cos[Dpm(t)] e7Dpmˆ(t) sin[Dpm(t)] e7Dpmˆ (t) Dpm(t) NL SSB-FMa NL SSB-EVa e{ln[1 + m(t)]± j ln[1 + ˆ m(t )]} [1 + m(t)] cos {ln[1 + ˆ m(t)]} ±[1 + m(t)]sin{ln[1 + ˆ m(t)]} 1 + m(t) ±ln[1 + ˆ m(t)] NL m(t) > –1 is required so that the ln will have a real value. SSB-SQa e(1/2){ln[1 + m(t )]± j ln[1 + ˆ m(t )]} NL m(t) > –1 is required so that the ln will have a real value. QM m1(t) + jm2(t) m1(t) m2(t) tan–1[m2(t)/m1(t)] L Used in NTSC color television: requires coherent detection. L = linear, NL = nonlinear, [ˆ.] is the Hilbert transform (i.e., –90° phase-shifted version) of [·]. The Hilbert transform is a Use upper signs for upper sideband signals and lower signs for lower sideband signals. bIn the strict sense, AM signals are not linear because the carrier term does not satisfy the linearity (superposition) condition. 0 1 180 1 , ( ) – , ( ) – m t m t > ° < Ï Ì Ó ¸ ˝ ˛ 0 0 180 0 , ( ) , ( ) m t m t > ° < Ï Ì Ó ¸ ˝ ˛ e jDf m d t (s s ) Ú-• cos ( ) – D m d f t s s Ú • È Î Í ˘ ˚ ˙ sin ( ) – D m d f t s s Ú • È Î Í ˘ ˚ ˙ D m d f t ( ) – s s Ú • [m t( ) [m t ˆ( )] 2 2 + e jDf m jm d t [ (s)± ˆ(s)] s Ú-• e D m d D m d f t f t m ˆ( ) – – cos ( ) Ú • Ú • È Î Í ˘ ˚ ˙ s s s s e D m d D m d f t f t m ˆ( ) – – sin ( ) Ú • Ú • È Î Í ˘ ˚ ˙ s s s s e D m d f t m ˆ( ) Ú–• s s D m d f t ( ) – s s Ú • 1 1 2 + = 1 Ï Ì Ó ¸ ˝ ˛ m t( ) cos l m t n[ˆ ( )] ± + + Ï Ì Ó ¸ ˝ ˛ 1 1 2 m t( ) sin l 1 m t n[ˆ ( )] 1 + m( )t ± + 1 2 ln[ˆ 1 m t( )] m t m t 1 2 2 2 ( ) + ( ) D ˆ( ) ( ) * ( ) x t x t t x t = = d -• - • Ú 1 1 p p l l l
RF circuits x(tI cos(ot) 力、x(cos(01)-y(s(0。0 y(t) Carrie s(@t) FIGURE 69.2 Generalized transmitter using the quadrature generation technique. 团等 a(intermediate Baseband Detector amplifier (to speaker CRT, etc.) FIGURE 69.3 Superheterodyne receiver. If the complex envelope g(t) is desired for generalized signal detection or for optimum reception in digital systems,the x(n) yt) quadrature components, where x(r)+ iy(t=g(t), may be obtained by using quadrature product detectors, as illustrated in Fig. 69.4. x(n) and yr) could be fed into a signal processor to extract the modulation information. Disregarding the effects of noise, the signal processor could recover m(r)from x(t) and y(t(and, consequently, demodulate the IF signal)by using the inverse of the complex envelope generation functions given in Table 69.1 PCM= pulse-code modulation DM= differential modulation DPCM=differential pulse-code modulation FSK= frequency-shift keying PSK= phase-shift keying DPSK= differential phase-shift keying MPSK= M-ary phase-shift keying QAM= quadrature amplitude modulation c 2000 by CRC Press LLC
© 2000 by CRC Press LLC If the complex envelope g(t) is desired for generalized signal detection or for optimum reception in digital systems, the x(t) and y(t) quadrature components, where x(t) + jy(t) = g(t), may be obtained by using quadrature product detectors, as illustrated in Fig. 69.4. x(t) and y(t) could be fed into a signal processor to extract the modulation information. Disregarding the effects of noise, the signal processor could recover m(t) from x(t) and y(t) (and, consequently, demodulate the IF signal) by using the inverse of the complex envelope generation functions given in Table 69.1. The generalized modulation techniques are shown in Table 69.1. In digital communication systems, discrete modulation techniques are usually used to modulate the source information signal. Discrete modulation includes: • PCM = pulse-code modulation • DM = differential modulation • DPCM = differential pulse-code modulation • FSK = frequency-shift keying • PSK = phase-shift keying • DPSK = differential phase-shift keying • MPSK = M-ary phase-shift keying • QAM = quadrature amplitude modulation FIGURE 69.2 Generalized transmitter using the quadrature generation technique. FIGURE 69.3 Superheterodyne receiver