Technical Overviews
The CMMB measurement application provides one-button standard-based power and modulation analysis capabilities to help your design, evaluation and manufacturing of CMMB modulators, transmitters, amplifiers, tuners and gap-fillers/repeaters. With the optional analog baseband IQ inputs in the PXA or MXA signal analyzer, it can also provide the flexibility of measuring signal quality and modulation accuracy with the RF input or analog IQ input
Key parameter setup
The CMMB measurement application is just one in a common library of more than 25 measurement applications in the Keysight Technologies, Inc. X-Series, an evolutionary approach to signal analysis that spans instrumentation, measurements, and software. The X-Series analyzers, with upgradeable CPU, memory, disk drives, and I/O ports, enable you to keep your test assets current and extend instrument longevity. Proven algori-thms, 100% code-compatibility, and a common UI across the X-Series create a consistent measurement framework for signal analysis that ensures repeatable results and measurement integrity so you can leverage your test system software through all phases of product development. In addition to fixed, perpetual licenses for our X-Series measurement applications, we also offer transportable licenses which can increase the value of your investment by allowing to you transport the application to multiple X-Series analyzers.
CMMB Standards Overview
China multimedia mobile broadcasting (CMMB) is a mobile digital video standard developed in China by the State Administration of Radio, Film, and Television. Announced in 2006, CMMB network has been deployed in more than hundreds of cities in China.
The core part of CMMB is satellite and terrestrial interactive multiservice infrastructure (STiMi). It uses both satellite and terrestrial signals to obtain effective coverage both in densely populated cities and in sparsely populated rural areas. CMMB system supports single-frequency network (SFN) and multiple-frequency network (MFN).
CMMB physical layer can support N (1~39) data streams at the same time (Fig 1). Each data stream is configurable on channel coding, constellation and timeslots allocation. That means CMMB signal can broadcast up to 39 services (e.g., SDTV, HDTV), giving each service different error protections.
The CMMB broadcasting system uses physical logical channels (PLCH) to transmit the upper-layer services. The allocation of PLCH is shown in Fig 2. The PLCHs include one control logical channel (CLCH) and 1~39 service logical channels (SLCH). CLCH contains CMMB broadcast system control information and occupies only time slot 0. SLCH can be configured to contain one or more time slots to transmit one broadcasting service.
RF Transmitter Tests
The RF transmitter test requirements for CMMB transmitter and exciter are efined in GD/J020-2008 technical specification and methods of mea-surement for mobile multimedia broadcasting transmitters and tech-nical specification and method of measurement for mobile multimedia broadcasting exciters (draft) standards. Table 1 shows RF transmitter and exciter tests defined by the specs along with the corresponding measurements provided by the CMMB measurement application
Measurement details
Measurements as defined by the CMMB standard, as well as a wide range of additional measurements and analysis tools, are available with a press of a button (Table 2). These measurements are fully remote controllable via the IEC/IEEE bus or LAN, using SCPI commands.
Analog baseband measurements are available on the PXA or MXA signal analyzer equipped with BBIQ hardware. Supported baseband measurements include all of the modulation quality plus I/Q wave-form and CCDF measurements.
Definitions
Specifications describe the performance of parameters.
95th percentile values indicate the breadth of the population (≈2σ) of performance tolerances expected to be met in 95% of cases with a 95% confidence.
Typical values are designated with the abbreviation "typ." These are performance beyond specification that 80% of the units exhibit with a 95% confidence.
Nominal values are designated with the abbreviation "nom." These values indicate expected performance, or describe product performance that is useful in the application of the product.
PXA specifications apply to analyzers with frequency options of 526 and lower. For analyzers with higher frequency options, specifications are not warranted but performance will nominally be close to that shown in this section.
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