SAW IF Filters Research Articles

A CMOS TV tuner/demodulator IC with digital image rejection

Superheterodyne TV tuners have been implemented in discrete forms using tunable RF and SAW IF filters. Integrating TV tuners in CMOS technology without them is a challenging task to cope with technical issues such as harmonic mixing and image. The image rejection in low- or zero-IF systems has been limited to 30-40 dB by analog imperfections such as I/Q path gain and phase mismatches. A single-chip low-IF TV tuner solution is proposed so that the image can be suppressed digitally using an image cancellation technique based on a complex one-tap LMS signal decorrelation algorithm. Programmable digital filtering and video/sound demodulation make a multistandard TV tuner feasible in the 48-860 MHz VHF/UHF band. The chip has a maximum gain of 63 dB and an input automatic gain control (AGC) range from -15 to 25 dB with 0.85-dB steps. It achieves an image and IF rejection of 60 dB, a peak carrier-to-noise ratio (CNR) of 55 dB, and a peak sound signal-to-noise ratio (SNR) of 44 dB without frequency modulation (FM) de-emphasis. The prototype occupies 6/spl times/6 mm/sup 2/ in 0.25-/spl mu/m CMOS and consumes 1 W at 2.5 V.

Low-loss SAW IF filters with new unidirectional IDTs used in digital mobile radios

A new type of unidirectional IDT having both excitation and reflection electrodes within each section of one wavelength (λ o ) was developed. High-performance SAW IF filters used in digital mobile radios with low insertion losses of 3.6 dB at 70 MHz and 3.8 dB at 250 MHz centre frequencies were realised using ST-cut quartz substrates

400 MHz SAW IF Filter for Satellite Broadcast Receiver without Any Adjustments

A UHF SAW filter for satellite broadcast receivers has been developed. Features are high center frequency to suppress the image interference, sufficiently flat group delay for linear FM detection and unnecessary any adjustments for tuning. The influence of electrode resistance on the insertion loss, and the triple transit echo caused by wave reflection is investigated in extended Smith's equivalent circuit model, and is effectively applied as an independent design parameter of the radiation and the load conductance. In cosequence the interdigital transducers with the wide aperture stretched nonoverlapped electrodes are efficiently verified to suppress undesired surface wave diffraction and reflection effects without any increase in the insertion loss, and to be able to omit the conventional tuning coils and the intentional impedance mismatching.