CMMB (China Mobile MulTImedia BroADCasTIng), China Mobile Multimedia Broadcasting, is China's first mobile broadcast TV standard with independent intellectual property rights for mobile terminals. It is also a portable mobile multimedia broadcast TV product jointly launched by China Mobile Communications Corporation and China Broadcasting Corporation. It mainly provides broadcast TV services for small-screen portable handheld terminals such as mobile phones and PDAs, as well as terminals such as car TVs. As a basic communication device, mobile phones are required to be able to complete basic communication functions and even multimedia processing functions, so integrating CMMB on mobile phones has become an inevitable trend. The system uses a combination of satellite and terrestrial supplemental forwarding technology. The broadcast frequency band is U-band (1.55-3.4 GHz and S-band (470-860 MHz). Because the system uses the broadcast transmission of the radio broadcast network The way, so it does not generate any traffic charges, which is essentially different from traditional streaming TV. Therefore, this kind of mobile TV terminal has a high market demand. This paper proposes a CMMB dedicated chip IF228 to realize mobile multimedia broadcast TV reception. The design of the terminal.
1 CMMB chip selectionWhen choosing CMMB mobile TV chip, we should consider its technical development trend. There are two aspects of this technology trend. On the one hand, it is the improvement of the function index of the chip itself, such as anti-interference ability, power consumption, size, various interfaces provided, etc. On the other hand, it is to reduce the overall cost and development difficulty of the chip, and facilitate the rapid entry of CMMB terminal solution manufacturers and the mass promotion of products. Considering that the SIP products packaged together are the most standard-compliant, the performance is the most stable, and the supply is also the most secure. In the long run, the all-in-one single chip that integrates functions such as tuner, demodulator, decoding and decryption is integrated. The solution will be the technical development trend of CMMB chip. Based on the above factors, choose the latest IF228 launched by Creative Video to design the mobile multimedia broadcast TV receiving terminal. The performance advantages of IF228 chip are reflected in the following aspects.
IF228 chip with high integration, small size IF228 set tuner, demodulator, UAM conditional integration, using 65 nm process, TFBGA 5 mm & TImes; 5 mm package, is the industry's smallest package CMMB demodulation chip, and solder balls The spacing is still 0.65mm, which greatly facilitates the customer's PCB design. The IF228-based CMMB solution can be implemented in areas up to 50 mm2. The highly integrated chip design and ultra-small chip package reduce the development difficulty and overall cost of the terminal product.
The IF228 chip has super demodulation performance to support the terminal's maximum moving speed of more than 800 km per hour, making it easy to adapt to high-speed mobile vehicles such as EMUs, magnetic levitation and even aircraft. At the same time, it is also excellent in low-speed mobile urban multi-path environments of tens of kilometers per hour. Under the standard TU6 channel of 20 Hz Doppler shift and 6 different intensities and delays, the actual demodulation threshold of QPSK is less than 7.3 dB. Another indicator that fully demonstrates performance is the adaptation of the equal-delay two-path maximum delay. When the two-path delay reaches 75μs, the IF228 still has a demodulation-to-noise ratio threshold of 12.5 dB in the QAM 16 modulation mode. Such performance metrics are sufficient to ensure seamless reception in any situation of single frequency networking.
The IF228 chip has strong resistance to single-frequency interference. Single-frequency interference is a key factor affecting its receiving performance and user experience for CMMB, a broadband system that uses time domain synchronization. The IF228 can still receive successfully when the in-band single-frequency interference exceeds 15 dB of the received signal. It is worth emphasizing that, in the case that the interference signal is too strong to receive, the interference signal is gradually weakened, and the IF228 can quickly resume normal reception. There is no so-called Schmitt reception effect (that is, interference from a weak interference environment). After a strong environment, the interference signal needs to be weakened more to restore normal reception). This feature can greatly enhance the user's reception experience in today's increasingly crowded electromagnetic environment. Moreover, the additional benefit of this feature is that the PCB EMI requirements are greatly reduced, and the customer does not have to worry about the harmonic interference that may be caused by the application processor and the baseband chip, which greatly simplifies the layout of the CMMB part.
The IF228 chip has low power consumption. The chip is based on CMMB's time slot receiving technology. Under 1/10 turn-on time (4 time slots, normally receiving a QPSK modulated program), the average power consumption is as low as 36 mW, average. Each time slot consumes less than 10 mW. In addition, the ultra-low current in Power down mode greatly simplifies the customer's power system design. Customers do not need to configure a separate LDO for the IF228/IF206 power supply, just plug in the existing I/O and core voltages from the system board. The peak current does not exceed 100 mA, and there is little need to consider the impact on the system power supply. The I/O voltage of the IF2 28 directly supports the range of 1.6 to 3.6 V, does not require any adjustment measures, and has a PWM output pin to facilitate the application of the subsequent built-in antenna.
IF228 chip supports multiple clock frequency inputs. In the CMMB terminal scheme design, the same industry demodulator in the past generally only supports a single clock frequency. If it is inconsistent with the clock frequency required by AP/BB, it will result in a terminal design scheme. Two crystals are supported. The newly released IF228/IF206 supports a variety of mainstream clock frequency inputs, including 10/12/13/18/19.2/20/24/26/27/30 MHz. Therefore, the IFMB/IF206 CMMB terminal solution can share a crystal with the AP/BB, which can save cost for the solution manufacturer and save space for the PCB design of the terminal solution.
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