Overview of mobile TV standards and their CMOS tuners

Abstract

The upcoming switch to digital TV in most of the world has renewed interest in terrestrial tuner implementations. More importantly, digital video reception is emerging as the latest feature towards multimedia-enriched handheld devices. Mobile, battery operated devices require small size tuners that consume low power and are amenable to single-chip integration with the baseband demodulator. In broadcast TV, the main standards expected to coexist worldwide are DVB-T (Digital Video Broadcast-Terrestrial) in Europe, ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) in Japan based on OFDM modulation (Orthogonal Frequency-Division Multiplexing) and ATSC-DTV (Advanced Television Systems Committee-Digital TV) in the USA based on 8-VSB (Vestigial Sideband Modulation). In mobile TV, several standards (summarized in Table 5.1) that will enable reception to cell-phones and other hand-held devices such as PDAs and portable music players compete globally. The most popular appears to be DVB-H (DVBHandheld) [1], which is an extension of DVB-T. Its main features are: (a) low-power reception, enabled by operation in bursts ("time-slicing") with a typical 1:10 on/off ratio at the expense of lower resolution and (b) additional error-coding (FEC) for more robust Doppler performance, needed for mobile operation. DVB-H is defined mainly for a portion of the UHF band, 470-750 MHz, since upper range is excluded as it may interfere with cell-phone operation in the 900MHz GSM band in Europe. Deployment in the VHF III band (170-240 MHz) is also discussed, even though it will be hindered by the larger antenna size required for lower frequencies. A significant advantage of DVB-H deployment in VHF/UHF frequencies is that it will allow DVB-T broadcast equipment to be used for DVB-H, with potentially only a software or firmware upgrade. In addition, usage of the 1450-1490MHz L-band is also discussed in Europe, while in the USA a 5MHz channel has been allocated for DVB-H operation in the L-band (1670-1675 MHz). T-DMB (Terrestrial Digital Multimedia Broadcasting) [2] is also OFDM-based and uses the DAB (Digital Audio Broadcasting) physical layer [3] for mobile TV operation. It is defined in the VHF III and 1450-1490MHz bands and has already been deployed in Korea, while it will compete with DVB-H in Europe. In Japan a lower bandwidth, mobile version of ISDB-T will be using 430 kHz channels in UHF. Finally, several more mobile TV standards are emerging worldwide, such as MediaFLO [4] and ATSC-mobile in the USA and DMB-T, CMMB (China Mobile Multimedia Broadcasting) in China. As shown in Table 5.1, the above standards have several common characteristics, such as OFDM modulation and operation in the same or similar bands (VHF III, UHF IV and V, 1450-1490MHz L-band and 1670-1675MHz L-band). Since mobile TV subsystems will be battery operated and will need to fit in the crowded cellular phone case, implementations that are small in size and consume low power are required. In addition, multistandard capability is desirable since it will reduce cost for integrators and will allow users to receive mobile TV in their devices as they travel. The rest of this chapter attempts to address the tuner design for such mobile devices in CMOS. First, an overview of typical tuner architectures used for broadcast TV is given. Subsequently, the specific challenges related to mobile TV standards are presented, with an emphasis to DVB-T/H radio specifications and their implications. The first implementation discussed is a DVB-H dual band tuner on 0.18μm CMOS process [5], which occupies 9.7mm 2. The tuner achieves a 4 dB noise figure (NF) at both UHF and L-band, eliminating the need for an external LNA. By using a fractional-N synthesizer both 470-862MHz and 1.4-1.8 GHz bands are supported, while achieving an integrated phase noise of less than -41 dBc. Sixth-order low-pass filters support channel bandwidths from 4 to 10 MHz. By using this as an example, techniques enabling the design of low-power, high-integration tuners are discussed in more detail. The second implementation example is a triband, multistandard tuner implemented on a 65 nm digital CMOS process [6], which is based on the same architecture. To achieve multistandard operation and coverage of most popular mobile TV bands, it also supports the VHF III band (174-240 MHz) and features additional programmability in the baseband filters to support channel bandwidths from 0.2 to 8 MHz. Compared to the first implementation it achieves better performance at half the power consumption, while it occupies less than 7mm2. The description in the second design case is focused on the additional features added to achieve multistandard operation and the specific challenges related to the 65 nm CMOS process. For both tuners, detailed measurement results are presented, including system-level using a digital demodulator. © 2009 Springer Science+Business Media, LLC.