November 27, 2020

High integration and low power CMMB solutions and typical applications

The China Mobile Multimedia Broadcasting and Television (CMMB) standard is a mobile multimedia standard developed by China and fully controlled by independent intellectual property rights. Compared with other foreign mobile TV technologies, CMMB's many technologies are at the international advanced level. Compared with traditional broadcasting, the main features of CMMB are: (1) Provide all-digital TV / digital broadcasting programs, comprehensive information and emergency broadcasting services, and achieve seamless coverage of the integration of satellite and ground networks. (2) The frame structure based on time slots greatly improves the use time of the receiving terminal. (3) The use of OFDM modulation technology, LDPC / Reed-Solomon coding and deep interleaving technology greatly improves the high-quality mobile reception performance in complex wireless environments. At present, CMMB has reached a stable reception of broadcast and television signals at a speed of 250 kilometers per hour. (4) Adopt unified technical standards and unified operation to support users roaming nationwide. CMMB provides some public welfare free radio and television programs, and also has an encryption authorization control management system to provide paid services.

Main features of CMMB receiver solution

A basic CMMB receiving terminal includes four main parts: an RF tuner, a baseband demodulator, a multimedia processor, and a display screen and speaker that finally output signals. The main application areas include: mobile phones, portable TVs, handheld navigators, PDAs, MP4, notebook computers and other small-screen portable handheld terminals, and mobile information terminals on cars, trains, ships, and aircraft.

In response to market demand, Quantum Microelectronics has launched a highly integrated CMMB receiver solution, including a complete CMMB RF tuner and baseband demodulator. The internal functional block diagram is shown in Figure 2. The main features of the program are as follows.

CMMB RF tuner

Compliant with CMMB GY / T 220 standard; adopts zero-IF tuner architecture without external SAW filter; single-chip tuner supports both VHF / UHF bands of ground towers and L1, L2 and S bands of satellite live broadcasting; AGC dynamic range : -102dbm ~ -10dbm; built-in fractional frequency division PLL frequency synthesizer; built-in low phase noise broadband VCO; built-in bandwidth adjustable image suppression low-pass filter; built-in RF and baseband analog adjustable gain amplifier (PGA); integrated low voltage Differential voltage regulator (LDO) requires only 3.3V single power supply; provides standard I2C control interface; high component integration, reducing external components; 70mA ultra-low operating power consumption; ultra-small QFN package, suitable for portable applications

CMMB baseband demodulator

Compliant with CMMB GY / T 220 standard; built-in high-speed 10-bit digital-to-analog converter; supports all 8MHz BPSK / QPSK / 16QAM modulation methods; built-in 4096-point FFT unit, and LDPC / Reed-Solomon forward error correction (FEC) decoder ; Built-in multiplexing function. Can simultaneously receive one control channel and up to 4 business channels; support flexible and convenient time slot allocation; business channel time slot allocation can be arbitrarily configured; provide universal SDIO and SPI interface output MFS code stream received; provide I2C interface and Programmable I / O and interrupts simplify the interface with external multimedia processors; built-in high-speed MCU, which can initialize, control and schedule the working state of the device, and signal quality monitoring; provide for TV mobile phones, PMP, and USB TV sticks Application development SDK greatly speeds up product development; ultra-low working power consumption and standby power consumption. Built-in power management module, supporting multiple standby modes; can be used as a single module with Quantum CMMB tuner in the form of SiP; ultra-small BGA package.

Block diagram of CMMB receiving terminal

Figure 1 CMMB receiving terminal block diagram

Working principle of each module

RF signal processing: For the VHF, UHF, and satellite direct broadcast frequency bands used by CMMB, there are corresponding low noise amplifiers (LNA) and RF adjustable gain amplifiers (mixers: mixers with zero-IF single-stage conversion architecture, no External SAW filter.

Baseband signal processing: including an image suppression low-pass filter with adjustable bandwidth and a baseband signal PGA.

Single-chip integration: Integrated low-noise VCO and fractional frequency division PLL reduce in-band phase noise.

ADC: Built-in a high-performance 10-bit ADC, directly sample the input I / Q two differential baseband analog signals.

AGC control: There are two AGC controls for RF PGA and analog baseband signal PGA. The AGC loop generates the AGC output by sampling the signal and the reference value.

Frequency tracking / frequency correction: This module completes the frequency tracking of the signal, frequency offset correction, and sampling rate conversion.

FFT: The FFT module performs Fast Fourier Transform to change the time-domain signal modulated by OFDM to the frequency domain for demodulation.

Beacon processing: the module performs synchronization and channel parameter estimation.

OFDM symbol processing: This module completes the processing of OFDM symbols. Including symbol descrambling, channel estimation and equalization, transmission instruction information demodulation, etc. Among them, the transmission instruction information is used to indicate the current time slot information and to indicate the change of the configuration parameters of the physical layer of the broadcast channel. The frequency domain signal after descrambling and equalization is sent to the next module for demodulation.

De-mapping and FEC decoding: This module completes BPSK / QPSK / 16QAM constellation de-mapping. The output after de-mapping is sent to LDPC and RS decoders for decoding. First, the LDPC decoder completes the decoding of the LDPC codeword and fills the load data into the RS byte interleaver. Then, the RS decoder completes the decoding work of the RS.

MFS code stream extraction: According to the selection of the external multimedia processor, it can simultaneously receive a control channel and up to 4 traffic channels. The data stream is output as an MFS code stream. Output interfaces include: SPI and general-purpose interface SDIO. Can support up to 100Mbps instantaneous data rate.

Peripheral interface: There are two I2C interfaces. One interface serves as an I2C slave controller, which is used to accept the control and setting of the demodulator by an external multimedia processor; the other interface serves as an I2C master controller to control the tuner.

Embedded MCU: a high-performance MCU is embedded to control all internal modules, as well as the collection and processing of related signal quality.

Quantum Microelectronics CMMB receiving terminal functional module block diagram

Figure 2 Quantum Microelectronics CMMB receiving terminal functional module block diagram.

typical application

Quantum's CMMB receiving solution has a highly integrated and flexible and universal interface. Only need to add a general multimedia processor, user interface and a small number of external components to form a complete CMMB receiving system. In the first-generation CMMB solution, the tuner, demodulator and multimedia processor are all separated. As technology advances, solutions with higher integration levels begin to appear.

In mobile phone applications, some mobile phone platforms have integrated powerful multimedia processing capabilities. Quantum's CMMB SiP solution and such a platform can be seamlessly connected. Quantum's RF tuner and baseband demodulator provide RF and baseband signal processing, and the mobile phone platform processes CMMB multimedia information. Another development trend is that some mobile phone platforms have begun to integrate baseband processors. Quantum's single-chip CMMB RF tuner provides an RF processing capability covering the whole world, which is very suitable for such a platform.

Summary of this article

Currently, the State Administration of Radio, Film and Television is building a CMMB network nationwide. It is expected that by the end of this year, the network construction of 333 prefecture-level cities will be completed. Quantum Microelectronics has launched a highly integrated RF tuner and baseband demodulator chip for the CMMB market, which meets all CMMB RF and baseband processing requirements. Claim.

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