A Novel TV/FM Front-end For Multimedia Applications

Abstract

This paper describes a new ,front-end technology for high performance TV and FM radio signal processing in multimedia applications. I t presents the principles of the combined video signal (TV) and sound signal (W and radio) demodulation using PLL techniques. This novel front-end demonstrates that FM radio and television I reception can be successfilly merged into one module , resulting in applications with reduced size and lower cost. INTRODUCTION tion, gain control, demodulation, switching, limiting and two PLLs are implemented on a single chip in an SSOP28 or SSOP20 package. The high level of integration achieved with the new advanced circuit design has resulted in a dramatic reduction of IC pin count, peripheral components, and factory alignments. On-chip functions of the IC (Fig.1) include: A vision IF (VIF) section with PLL for true synchronous demodulation of the video modulated IF signal A sound IF (SIF) section for QSS signal processing, together with an AM demodulator for the AM sound and a PLL for demodulating the FM sound IF signals Additional stages for FM radio detection which are combined with the TV sound IF circuit. This paper describes a novel RF concept which is capable of receiving both broadcast television and FM radio signals, and is intended for applications in desktop personal computers. Compared to solutions using separate-radio and TV tuners, the module allows for a considerable reduction in total cost and board space. The cost saving is achieved by sharing key components and other circuitry needed for channel selection and demodulation of broadcast television and FM radio. Multistandard true synchronous VIF-detection ( p o d Major features of the IC include: 5 V supply voltage and low power consumption in power-down mode Small SSOP20 or SSOP28 SMD package neg. modulation) [I] Multistandard SIF demodulation (AM/FM); optional QSS Alignment-free, highly linear, low noise PLL FM demodulator, switchable between TV FM IF and radio IF Alignment-free AM detector (Secam L). Receiving FM radio with a television tuner has been demonstrated before, but always with mediocre performance. In this respect the novel TV/FM front-end can be considered a breakthrough; the quality of the FM audio delivered is more than adequate, and competes with that of * an average Mini HiFi system and or separate radio modules available on the market. A novel feature of the RF module design is a new IC2 with circuitry for both radio and television demodulation. The front-end is designed for a single 5 v Power SUPPlY using an internal D C D C COnverter to generate the tuning voltage. TV/FM FRONT-END The complexity of the circuitry and the number of components used were minimized by merging TV and FM signal processing in a single module (Fig.2). The key functions, and the specific implementation problems and solutions which were covered include: IF PLL FOR TV/FM-RADIO FM receiver concept choice Local oscillator spectral purity A new IC using an advanced multistandard IF PLL has been developed for vision and sound IF signal processing in this multimedia application. All the stages for amplificaMerger of TV and FM RF-selectivity Choice of FM radio IF frequency and filtering. These will be described in the full paper in more detail, as will aspects like module size, immunity against unwanted RF signals, EMC and power supply (with the new DCIDC converter). I . The module is available commercially as FM1200. 2. The IC is available commercially as TDA9816M or TDA9809M.