Measurement Functions for North-American Digital TV Standard

Articles

ATSC Test Receiver EFA All measurement functions for North-American digital TV standard

Following North America‘s decision in favour of ATSC/VSB (Advanced Television Systems Committee) for digital TV broadcasting, Rohde & Schwarz started to develop the necessary instrumentation and transmitters (see overview on page 13). After the successful launch of test receivers for analog TV signals and European digital TV standards, a new member for ATSC has now joined the EFA family. Compact in design and with extensive automatic test functionality, this receiver (FIG 1) is ideal for applications in the development and production of transmitter modulators as well as acceptance testing of large transmitter systems and monitoring the quality of digital TV signals.

EFA – characteristics

ATSC Test Receiver EFA, fully compatible with the ATSC Doc. A/53 standard, receives, demodulates, decodes and analyzes VSB (vestigial sideband) signals. All major parameters for demod- ulating the receive signal can be selected automatically or manually: • 8VSB modulation, • trellis decoder (code rate 2/3), • variable symbol rate for special modulator tests and lab analysis, • Reed-Solomon error correction 207/187/10, FIG 1 ATSC Test Receiver EFA joins EFA Photo 43482/1 instrument family, adding measurements in • filter bandwidth 6 MHz, option- digital TV systems to North-American ATSC/VSB ally 2 MHz and 8 MHz. standard The operating principle of the new receiver is largely identical with that of the other receivers of the EFA family [*] except for standard-specific functions. Full ATSC coverage by 2002 simultaneously on digital and analog channels during the transition period. Singular versatility Key features of the North-American digital TV standard are the use Another milestone was the definition The new test receiver features a multi- of MPEG2 (Moving Pictures Experts of a tight time frame by the legislation, tude of innovative measurement func- Group) to compress video and audio compelling stations to start broadcast- tions right from the basic version, allow- signals, and 8VSB modulation (see ing digital TV signals in good time. The ing comprehensive, in-depth signal box, pp 12–13). first digital programs were transmitted analysis. In addition to measurement on schedule in November 1998. To of general parameters such as bit error A decisive factor for fast, nationwide date (May 2000) some 120 stations ratio (BER) (FIG 2), more thorough introduction of digital TV in the United are on air with digital programs, provid- analysis includes: States was the allocation of additional ing coverage for about 60% of the US- • I/Q constellation diagrams with 6 MHz channels for the parallel trans- American population. By late 2002 all selectable number of symbols to mission of digital TV programs by all commercial TV stations are to follow. be represented, the approximately 1600 broadcast sta- It is planned to shut down all analog • eye aperture and modulation error tions. This made it possible to operate channels by the end of 2006. (MER/EVM) versus time,

News from Rohde & Schwarz Number 167 (2000/II) 11 Articles

• calculation of transmission param- of its rapid data acquisition, the test 8VSB – ATSC modulation for terrestrial eters like pilot carrier, receiver is an ideal choice not only broadcasting of digital TV signals • amplitude spectrum of user in R&D but also in production monitor- channel, ing, where high measurement speed The ATSC standard employs 8VSB (8-level trellis- • linearity analysis from histogram is called for. coded vestigial sideband) discrete amplitude mod- of amplitude distribution, ulation. Here the incoming data stream at the • complex channel transmission transmitter is applied to a data randomizer, Reed- function, EFA-ATSC as monitoring Solomon encoder and data interleaver, divided into • received echo signals (ghost pat- receiver packets of two bits and, because of the 2/3 code tern). rate, coded to produce data packets of three bits Monitoring receivers permanently moni- in a Viterbi convolutional encoder (trellis encoder). Any failures and degradations are vis- tor the major parameters of broadcast Each group of three bits (symbol) represents a ible straight away from the constella- signals directly at the transmitting sta- tion diagram (FIG 3). Effects of interest tion (FIG 6). EFA-ATSC is tailor-made can be located more precisely by vary- for this application. Six parameters ing the number of symbols represented. with separately selectable alarm thresh- A particularly effective method here olds can be configured for monitor- Captions to FIGs 2 through 6 is presentation of eye aperture as a ing. Particularly worth emphasizing is FIG 2 Measurement menu: all important data visible function of time. Eye apertures plus BER monitoring ahead of and after the at a glance FIG 3 Constellation diagram, here representing decision thresholds are displayed on various error-protection blocks, allow- 10000 symbols a largely user-selectable scale reveal- ing early detection of any problems. FIG 4 Spectral analysis of 8VSB signal by means ing, for example, periodic transmis- Detected transmission errors are saved of FFT sion errors or individual interferers in the test receiver together with the FIG 5 Display of calculated 8VSB transmission parameters in corresponding measurement at a glance and allowing immediate date and time in error reports compris- menu identification. Trend analyses, too, are ing up to 1000 entries. In addition, it FIG 6 Simultaneous analysis/measurement of key possible with this method. triggers an acoustic alarm. parameters – ideal for monitoring tasks

The integrated spectral analysis function enables simple examination of the Use as relay receiver signal type and its spectrum. You can see immediately, for example, whether For this special application, EFA is there is a marked frequency offset, or simply optimized for reception at a if the pilot-carrier level matches the keystroke. This allows reception even specification (FIG 4). An optional filter under adverse operating conditions. with 8 MHz channel bandwidth covers The user is also able to configure the spectral components outside the 6 MHz bandwidths of the main amplitude- and user channel while effectively suppress- phase-control loops. ing more distant components. Christoph Balz; Mathias Leutiger; Ernst Polz

Realtime signal analysis 2 The powerful digital signal processing of EFA provides fast and in-depth analysis of 8VSB signals (FIG 5). Analysis is simultaneous with and independent of demodulation and decoding, so the MPEG transport stream is permanently available for vision and sound repro- duction. Thanks to this realtime analysis capability, the large number of measured values necessary for the complex calculation and display processes are produced fast for subsequent mathe- Further articles on Test Receivers EFA on pages matical-statistical processing. Because 32 and 37 of this issue. 3 12 News from Rohde & Schwarz Number 167 (2000/II) Articles

specific amplitude level (eight levels). Synchroniza- Everything for ATSC from Rohde&Schwarz tion data (segment sync, field sync) are added to the coded signal for data recovery in the receiver TV Test Transmitter SFQ

TV Test Transmitter SFQ (News 166) (error correction, channel equalizer). For carrier SFQ goes North American – with digital TV standard ATSC recovery in the receiver, the unmodulated carrier TV Test Transmitter SFQ has proven itself as a platform for the new digital TV modulation methods introduced in Europe [1]: as a universal test signal source in the development, production, quality control and servicing of all components employed in video and audio data transmission. The transmitter generates standard modulation signals for all the digital methods involved, for terrestrial emission (DVB-T), cable transmission (DVB-C) and transmission via satellite (DVB-S). The UHF is added to the 8VSB signal as a pilot. To make new model 30 (FIG 1) includes yet another standard: the digital terrestrial TV transmission standard ATSC recently introduced in North America. UHF Transmitter Family NV/NH7000 Transmitter the most efficient use of the available bandwidth, Liquid-cooled TV transmitters for terrestrial digital TV Family Rohde & Schwarz is launching a new generation of liquid-cooled UHF transmitters only one sideband of the AM-modulated signal is perfectly timed for the startup of regular operation of terrestrial digital TV (DVB-T) by many countries. The compact design facilitates the installation of new DVB transmitters at existing sites where space normally is very restricted. Thanks to NH/NV7000 modular design, transmitter systems for both digital and analog TV can be created, meeting future requirements and featuring high economy and reliability. transmitted (vestigial-sideband suppression). Prior (News 165) Latest technology with special Modular not only for output features power Photo 42 592 to emission, the modulated signal is shaped by a The new water-cooled UHF Transmit- The modular transmitters chiefl y consist FIG 1 Model 30 of TV Test Transmitter SFQ ter Family NV/NH7000 in LDMOS of: generates signals complying with the North- (lateral diffused metal oxide silicon) • digital exciter American TV standard ATSC technology meets all requirements of • power amplifi er with integrated terrestrial TV standard DVB-T to ETS power supply root-cosine rolloff filter (r = 0.115). 300744 and those of the familiar PAL, • transmitter rack (with vision/sound SECAM and NTSC standards by suit- diplexer for analog TV) able confi guration of the digital exciter. All ATSC signals in excellent SFQ supplies signals of excellent qual- Transmission immune to The family of equipment is dual-sound The transmitters with maximum output quality ity in full compliance with specifi ca- interference compatible to IRT or NICAM and can power of 2.5 kW for DVB (FIG 1) tion ATSC DOC. A/53 (8VSB) (FIG 2). also be confi gured to comply with the or 10 kW for analog TV require very In 1996 the Federal Communications The standard parameters can be modi- The ATSC standard employs 8T VSB American ATSC standard for digital little space. They are accommodated Commission (FCC) selected the TV fi ed as required for a given measure- (eight-level trellis-coded vestigial side- TV. in a 630 mm wide rack together with standard of the Advanced Television ment task. The test data sequences band) amplitude modulation, which other components such as fi lters, power Systems Committee (ATSC) as the new delivered by SFQ allow convenient has eight discrete levels and is immune Transmitters are available for DVB-T couplers and water distribution system. digital terrestrial TV standard for the measurement of bit error rates at the to interference. Vestigial sideband fi lter- from 400 W to 5 kW (seven power To produce higher power, a second United States of America. Allocation of receiving equipment. To simulate real ing of the signal (rolloff characteristic) classes) and for analog TV from 2 kW rack with amplifi ers is simply added the frequency ranges was completed transmission conditions, the quality of reduces the bandwidth to the US chan- to 40 kW (fi ve power classes). Their and combined via 3 dB couplers. a year later. The transition from the the RF signal from SFQ can be modi- nel spacing of 6 MHz and makes for main characteristics are: 50-year-old analog NTSC system to fi ed and degraded. minimum symbol interference in the • latest LDMOS technology for The transmitters are therefore ideal the new digital transmission standard receiver. power amplifi ers (high gain, high for setting up new DVB networks at has since rapidly taken place. linearity) existing sites where space often is • very compact design (low space very restricted. On the one hand, this News from Rohde & Schwarz Number 166 (2000/I) 13 requirements) through liquid cool- reduces the costs for the network opera- ing tor. On the other, it is also very impor- • digital equalization (accurate tant for the acceptance of the new reproducibility of settings) medium, because all household roof • high redundancy for high avail- antennas would have to be realigned ability if the new system were to be installed • low installation outlay at a new site. • simple swap of modules during operation Photo 43 410/3 Despite the compactness of the new transmitter family all its modules are easy to access and service. The ampli- Photo 43 392/1 Photo 43 FIG 2 DVRM – specialist for blanket monitor- to central monitoring software both REFERENCES ing of broadcast networks locally (COM) and via a data network [1] Fischbacher, Michael; Rohde, Werner: FIG 1 Space-saving DVB transmitter for MPEG2 measurement generators and decoders 2.5 kW accommodated in a single rack link (DCOM). PC software for MPEG2 dream team DVG/DVMD. News from Rohde & Schwarz the TS_ID to identify the correct TS, it Let's go west: (1997) No. 154, p 29 News from Rohde & Schwarz Number 165 (1999/V) 11 continuously compares its complete Apart from comprehensive measured- [2] Finkenzeller, Richard; Fischbacher, Michael: ATSC ready for takeoff structure with a template that defi nes value acquisition via the remote-control MPEG2 transport stream analysis in net- all programs contained in the TS as interface, DVRM offers hardware sig- worked DVB monitoring system using Stream Explorer software. News from A special standard complying with national requirements is used in the US for well as the associated services for each nalling capability via relay contacts. Rohde & Schwarz (1998) No. 159, terrestrial broadcasting of digital TV signals: ATSC (Advanced Television Systems program. Each of the twelve contacts can be pp 24 – 25 Committee). Same as the European DVB standard, ATSC is based on MPEG2 coding assigned one error parameter or any but it differs in some essential features. Several countries in South America and combination of them. Closed or open Asia are about to adopt this standard. So Rohde & Schwarz has integrated the ATSC DVRM integration into network- contact signalling of errors is selectable. standard in all its measuring instruments concerned. wide monitoring systems DVRM thus ensures complete monitoring of complex networks. All instrument settings and the polling of Michael Fischbacher results are remotely controlled. The sup- plied Windows™ program allows fast confi guration of DVRM, clearly presents Condensed data of DVRM measurement results and the transport Input signals transport stream to ISO/IEC 1-13818 stream structure together with the data Length of transport stream packets 188/204 bytes (DVB), 188/208 bytes (ATSC) rates and offers special functions such Data rates of transport stream 0.6 to 54 Mbit/s Signal inputs 1 x TS parallel (to DVB-A010), as continuous recording of comprehen- 2 x TS-ASI (to DVB-A010) for DVB sive measurement reports on a storage 1 x SMPTE 310 and 1 x TS-ASI for ATSC medium of the controller. DVRM further Measurements – parameters to ETR290 (adjusted for ATSC) supports Stream Explorer™ software, – TS structure monitoring which allows in-depth analysis of the – data rates of overall stream, programs and transport stream [1]. substreams (PID) – monitoring of TS_ID – monitoring of “other_tables” (only DVB) Both the control software under – paradigm condition (only ATSC) MPEG2 Realtime FIG 1 Windows™ and Stream Explorer™ MPEG2 Measurement Generator DVG and – trigger on error MPEG2 Measurement offerDecoder COM DVMD (component with object model) Interfaces RS-232-C, 12 relay contacts optional software nowand also supportDCOM the (distributed North COM) soft-

Photo 42 499/3 Reader service card 165/04 American ATSC standardware interfaces [2]. This means that Monitor DVRM all functions can be made available

News from Rohde & Schwarz Number 165 (1999/V) 15 For the last three years Rohde & MPEG2 Measurement Generator DVG With the aid of the optional software ™ (News 165) Schwarz has been accompanying the is a versatile transport stream signal Stream Combiner DVG-B1, other worldwide introduction of digital TV source especially suited for continuous external elementary streams can also with its “dream team” made up of operation. It is able to provide a com- be integrated and multiplexed to a MPEG2 Measurement Generator prehensive range of test patterns continuous seamless transport stream DVG, MPEG2 Measurement Decoder (bounce, sweep, colorbars, etc), test for DVG (FIG 2). This function was DVMD [1] and the optional software tones (CCITT.033) and moving picture enhanced particularly for the use of packages Stream Combiner ™ and sequences in a seamless loop. This Dolby AC-3-coded audio and 4:2:2 Stream Explorer ™ [2]. The instruments makes it an ideal instrument for pro- or HDTV video sequences of up to are now multistandard units and sup- duction testing of set-top boxes and 25 Mbit/s. An ATSC setup ensures that port the North American ATSC stand- for testing modulators and transmis- the program paradigm is adhered to ard which differs from the European sion links. The generator has been re- and that all required ATSC tables and standard in some essential features: vised and upgraded and the follow- descriptors are added. The compre- · High-resolution formats ing enhancements have been added: hensive editor enables modification of (480, 720, 1080 lines) · ATSC sequences with HDTV video ATSC tables (STT, MGT, TVCT, CVCT, · Progressive scanning (60 Hz) and audio elementary streams RRT, EIT, ETT, PIT) and their extension · 6-channel Dolby surround AC-3- (Dolby AC-3) by other descriptors. The editor also coded audio · Faster hardware uses Huffman coding for information REFERENCES · Other tables · Larger memory in plain text within the tables. Also · Data-compressed table contents · Expansion of SPI and ASI new is the possibility of including com- interfaces to 208 bytes/packet [*] Balz, Christoph; Leutiger, Mathias: DVB-T 20 News from Rohde & Schwarz Number 164 (1999/IV) 4 Test Receiver EFA-T. The test reference: now MPEG2 signal genera- for terrestrial digital TV too. News from tors and analyzers Rohde&Schwarz (1999) No. 164, pp (News 164) 4–7

Condensed data of EFA-ATSC Frequency range model 50: 48 MHz to 862 MHz model 53: 43 MHz to 1000 MHz model 53 with option EFA-B3: 5 MHz to 1000 MHz Input level range model 50: –77 dBm to +10 dBm model 53: –47 dBm to +14 dBm model 53 with option EFA-B3: –77 dBm to +14 dBm Bandwidths 6/8/2 MHz 5 Modulation 8VSB Symbol rate 2 to 11 Msymbol/s Equalizer auto/freeze/off BER analysis ahead of and after Reed-Solomon decoder, ahead of Viterbi decoder Measurement functions level, BER, MER, EVM, SNR, pilot-carrier level, pilot-carrier frequency, symbol rate Graphical displays I/Q constellation, amplitude spectrum, echo signals (ghost pattern), complex channel transmission function, amplitude distribution, eye pattern, history Output signals SMPTE 310, MPEG-TS: SPI, ASI Options RF preselection (EFA-B3), SAW filter 8 MHz/2 MHz (EFA-B13/-B14)

Reader service card 167/03

6 News from Rohde & Schwarz Number 167 (2000/II) 13