Articles TV Test Receiver Family EFA multiplied by the sound carrier and the intercarrier thus obtained is select- ed and frequency-demodulated. The Top fit for advantage of this is that incidental phase modulation from local oscillators digital television as provided in every TV receiver does not appear in the demodulated audio Small-size, compact, future-oriented, upgradable – this is how TV Test Receiver signal, whereas that from the vision Family EFA shows its true self. With this family Rohde & Schwarz has created modulator is reflected in the demodulat- a test platform that can easily keep pace with rapid developments in television. ed audio signal. TV Test Receiver EFA Before the official start of digital video broadcasting, Rohde & Schwarz can detects this interference and is therefore already offer the world’s first demodulator for QAM signals which is able to suitable for measuring and monitoring perform all the measurements required on cable digital channels. An analog the sound quality of received signals. TV test receiver – either broadband or selective – is available for monitoring The frequency-demodulated audio sig- the previous TV channels. Digital and analog functions can also be combined in a nals are brought out at balanced out- single unit, which can be expanded by adding options. puts. For measuring incidental carrier With its modular design the compact 12-kg TV Test Receiver EFA (FIG 1) is extremely versatile and made for easy upgrading. In addition to the micropro- cessor module fitted as standard and the modules of the respective basic EFA model, another five functional modules can be accommodated (FIG 2). Every user can thus configure a model to suit his specific requirements or upgrade the basic model at a later date. Basic models The first member of the EFA family is the analog TV test receiver with selective receiver section. It receives amplitude- modulated TV signals to all common standards, selects the TV channel and converts it to IF. Picture and sound signals are then demodulated by the analog demodulator. Sound is demod- ulated according to the intercarrier method, where the vision carrier is FIG 1 TV Test Receiver EFA, allround specialist for measurements on analog and digital TV signals – seen here in headend station Photo 42 575 News from Rohde & Schwarz Number 152 (1996/III) 17 Articles Receiver section with tracking selection IF input IF vision Analog demodulator Video Selective Attenuator Selective IF sound for vision and Audio (FM) RF input 0 to 55 dB receiver section intercarrier sound Receiver section of broadband demodulator model IF input NICAM IF demodulator Broadband Attenuator Broadband RF input switch receiver section MPEG2 DSP analysis IF transport QAM demodulator stream RS-232-C Micro- IEC/IEEE bus LCD processor Printer IF output FIG 2 Block diagram of TV Test Receiver EFA An optional NICAM demodulator is Further functional modules can be add- (basic models shown in blue, functional modules available for decoding the digital ed to the broadband TV test receiver in yellow). Receivers can be configured to suit specific application. QPSK-modulated sound carrier to just as to the selective one. NICAM 728 standard. Further options (functional modules) are in develop- Another member of the EFA family is the ment. DVB test receiver with QAM demod- ulator. It is used for measurements on In addition to the model with selective digital channels in cable-TV networks. receiver section, the analog TV test re- Instead of an analog demodulator, a phase modulation (ICPM), TV Test ceiver is also available with a broad- demodulator for quadrature amplitude- Receiver EFA provides a quadrature- band receiver section. In single-chan- modulated (QAM) signals – fully com- demodulated vision carrier signal. In nel applications it is used for measure- patible with the DVB standards [1] – is conjunction with an internal or external ments directly on the source. Typical used in this case for processing the zero reference pulse and an oscillo- examples are measurement of the DVB-C channel converted to IF. The out- scope or video analyzer, it allows quality data of TV transmitters and put signal is then in the form of a serial quantitative determination of ICPM. transposers in single-channel mode as or parallel MPEG2 transport stream [2]. well as monitoring radiated RF sig- The analog TV Test Receiver EFA meas- nals. A Nyquist demodulator ensuring The QAM demodulator measures the ures all important RF transmission pa- system-compatible demodulation of the following parameters separately, per- rameters and displays them on an generated signals is used for these forms calculations [3] and outputs LCD (FIG 3): applications. the results on its display in line with re- • power and voltage of vision carrier quirements of the DVB Measurement in dBm, dBpW or µV/mV, dBµV, Group [4]: • vision carrier frequency, • constellation diagram, • vision/sound carrier level ratio, • RF level, • vision/sound carrier frequency spac- • signal/noise ratio, ing, • bit error rate, • FM sound carrier deviation, • amplitude imbalance, • FM pilot deviation, • carrier suppression, • pilot frequency. • phase error and phase jitter, • modulation error ratio (MER). Depending on the model, Test Receiver EFA demodulates TV signals of stan- The constellation diagram (FIG 4), dards B/G, D/K, K1, I or M/N. In ad- which is graphically displayed and dition to a constant video group delay, mathematically evaluated by a signal implemented in each receiver model, processor, supplies the most important TV Test Receiver EFA features group- information on QAM signals. To ensure delay correction that depends on the the required statistical reliability for respective standard and is available FIG 3 Screen display for analog TV test receiv- the evaluated parameters, about for all worldwide TV standards. er mode 1,000,000 I/Q values are considered. 18 News from Rohde & Schwarz Number 152 (1996/III) Articles The QAM demodulator can be fitted Uses REFERENCES with up to three SAW filters so that not [1] European Telecommunications Standards In- only 8-MHz QAM packets can be pro- The broadband TV test demodulator is stitute ETSI: Digital broadcasting systems for television, sound and data services; framing cessed with 64QAM which is almost ideal for the precise measurement and structure, channel coding and modulation standard today, but also packets of monitoring of the quality data of TV cable systems. Draft prETS 300 429 (1994) 4 or 2 MHz. Thanks to the versatile transmitters and transposers. The selec- [2] DVB Technical Module’s Ad-hoc Group Phys- configuration possibilities of the QAM tive receiver model is required for ical Interfaces: Interfaces for CATV/SMATV demodulator, 4QAM to 256QAM can measurements in cable-TV networks. headends and similar professional equip- ment. 10th working draft DVB-PI-154 (1995) be selected for all current methods. For this application the combinational [3] Balz, C.: Effiziente Ermittlung von Qualitäts- Among many other features, error pro- unit with analog and QAM demodula- parametern quadraturamplitudenmodulierter tection can be switched off and the roll- tor is recommended. The powerful test Signale beim Digitalen Fernsehen (DVB). off factor selected. A built-in noise receiver family is of course also suitable Fernseh- und Kinotechnik No. 5 (1996), generator is available for determining for applications in development labs, pp 249–252 the noise margin. quality management and production [4] DVB Technical Module’s Ad-hoc Group on Test and Measurement: MG 66 Rev. 4 monitoring. (04/1996) It is of course possible to equip the test receivers for the measurement of both With TV Test Receiver Family EFA from analog and digital TV signals. The mod- Rohde & Schwarz an enormous step has been made towards digital video broadcasting, whilst taking full account of previous TV standards. The program will be continuously expanded by new functional modules to open up further sectors of digital television. Christoph Balz; Ernst Polz; Walter Fischer FIG 4 Constellation diagram in QAM demod- ulator mode; result hold time adjustable from 2 ms to infinite Condensed data of TV Test Receiver Family EFA Frequency range 47 to 862 MHz Inputs RF, IF Input impedance, RF 50 or 75 Ω ular design allows optimum customiza- Input voltage range tion and the configurations described Selective analog TV test receiver 30 µV to 1000 mV above are only a few among many. Selective QAM receiver 100 µV to 700 mV Broadband analog TV demodulator 10 to 2500 mV Outputs IF, controlled Interfaces Loudspeaker, headphones adjustable volume, can be switched off Interfaces IEEE 488, RS-232-C, Centronics EFA features a large LCD for display of Nyquist test receiver user information, measured values and Inputs external zero reference pulse graphs. Hardkeys and softkeys ensure Outputs video, Q signal, audio balanced, audio unbalanced, headphones great ease of operation. The micropro- QAM demodulator cessor module provides a variety of Specifications compatible with DVB guidelines interfaces; the receivers can be remote- Order of QAM 4, 16, 32, 64, 128 or 256 ly controlled via IEEE bus or RS-232-C Rolloff factor 0.15 to 0.30, selectable Internal noise generator 12 to 62 dB C/N, adjustable interface and come with a printer con- Outputs parallel or serial MPEG2 transport stream, nector. The demodulated sound can serial data/clock before error correction be monitored via a built-in loudspeaker Reader service card 152/06 or headphones. News from Rohde & Schwarz Number 152 (1996/III) 19.