340 4-900784-01-X 2005 Symposium on VLSI Circuits Digest of Technical Papers 22-1 A Dual-Conversion Tuner for Multi-Standard Terrestrial and Cable Reception Iuri Mehr, Steve Rose, Sergei Nesterenko, Donald Paterson, Richard Schreier, Hassan L’Bahy, Sunder Kidambi, Michael Elliott, and Scott Puckett Analog Devices, USA Abstract A multi-purpose TV tuner front-end implemented in 0.35� m BiCMOS technology is presented. It employs a dual-conversion topology and a fully integrated RF automatic gain control loop. The tuner front-end achieves � 68dB composite-triple beat (CTB) distortion and a noise figure of 6.8 � 7.4dB in a 50 � 870Mhz input frequency range. In addition, the front-end is interfaced with a companion chip, which contains a high dynamic range ADC combined with programmable digital filters to accommodate multi-standard operation. Introduction Modern TV receivers and set-top boxes require universal tuners capable of processing analog and digital, terrestrial and cable broadcast. There are several digital standards in existence throughout the world. The ATSC standard (North America) is based on 6-MHz channels using single-carrier QAM (SCQAM). The DVB-T standard (Europe) employs 7-MHz or 8-MHz channels using COFDM. Similarly, the ISDB standard (Japan) uses OFDM and allows splits within a channel of up to 13 segments to facilitate reduced specifications for mobile reception. In addition, there is a new DMB-T standard emerging in Asia. Although digital broadcast is becoming more ubiquitous, it is the legacy analog broadcast which constrains specifications (particularly linearity and image rejection). Combining the dynamic range requirements for the aforementioned modes and standards, Table 1 shows a summary of major specifications for a “universal” TV receiver. TABLE 1 MULTI-STANDARD SPECIFICATIONS Min./Max. Input Power/Channel �85/�20dBm Max. Total Input 5dBm Noise Figure 7dB IIP3 28dBm CTB, CSO �63dBc Image Rejection 70dB Ph.n. @ 10kHz/100kHz/1MHz �85/�110/�125dBc/Hz An important specification for terrestrial reception is the system sensitivity (ability to receive signals as low as -85dBm). The noise figure (NF) of the receiver directly impacts the ability to demodulate the signal with a given bit-error rate (BER). For example, a noise figure of 8dB allows an achievable SNR = 174 � 10log 10 (6MHz) + P in,min � NF = 14.2dB, although it doesn’t leave any margin for degradation due to phase noise or other impairments. On the other hand, adjacent channels could be broadcast at significantly higher power. Therefore, distortion performance (IIP3) needs to allow desired channel reception while dealing with interferers or adjacent channels up to 50dB higher (in total power). Cable reception linearity requirements are specified as composite triple beat (CTB) and composite second order (CSO) distortion. Analog reception (cable or terrestrial) demands a higher carrier-to-noise ratio of about 55dB for a “perfect picture”. Phase noise (Ph.n.) matters at low offsets from the carrier as it increases the EVM (error vector magnitude), and at offsets larger than 1MHz as well, due to the possibility of reciprocal mixing. This paper presents a dual-conversion tuner, which provides sufficient sensitivity and selectivity to accommodate all aforementioned modes and standards. Tuner Description Some recent tuner implementations employ single- conversion [1], or dual-conversion to DC [2] topologies to address specific applications, trading off external components for specific performance. Dual-conversion to low IF architectures [3,4] are more robust with respect to image rejection and interferers, although they still require sufficient dynamic range in the front-end (or a tracking band-pass filter). To achieve multi- purpose functionality, the tuner front-end employs a dual-conversion architecture in conjunction with a broadband RF AGC, quadrature mixing [5], and fractional LO synthesis. The back-end consists of a complex �� band-pass ADC, followed by decimation, down-conversion to base-band, and programmable