A single-chip wide-band tuner with an active splitter for cable data modems and set-top boxes is realized in a 0.5µm, 30GHz BiCMOS technology [1]. The IC employs a single down-conversion, low-IF architecture and can receive signals in the 48-860MHz frequency range. Fully integrated selectivity is obtained in combination with a channel decoder. Power consumption is 1.5W with a 3.3V supply.Existing dual-conversion architectures like [2-4], remove the need for tuner alignment, but still use external fixed frequency filters. The goal of this work is to fully integrate the TV front-end selectivity and make external RF and filter components (like coils, SAW and ceramic filters) obsolete, without compromising performance.The IC (Fig. 25.3.1) contains a splitter amplifier, RF AGC amplifier, switchable RF band-pass filter, RF polyphase filter, double quadrature down-conversion mixer, IF polyphase filter, groupdelay correction filter, low-pass filter, IF AGC amplifier, fully integrated voltage controlled oscillator (VCO), synthesizer and a received signal strength indication (RSSI) circuit.

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This paper describes a 48-860 MHz TV splitter amplifier with three outputs, based on a negative feedback design. The amplifier is intended for TV, VCR and set-top box (STB) applications, where multiple tuners have to be connected to the same cable outlet. The amplifier compromises high linearity and low noise figure by controlling its gain. At a frequency of 850 MHz, the input IP2 and IP3 are 94 dBm V and 73 dBmV respectively for the lowest gain setting while the noise figure is 7 dB for the highest gain setting. The design is fabricated in a 0.5 pin, 30 GHz BiCMOS technology [ I ] and dissipates 130 m W from a 3.3 Volt supp/y.channel. For low input levels, a high gain and a low noise figure are required. For high input levels, the gain should be low and linearity high. This combination of requirements can best be realized with a switched gain amplifier. By switching the amount of feedback, the gain is set to -2, +2 or +6 dB. Compared to state of the art discrete splitters, the presented splitter can change its gain according to the offered signal level resulting in the optimum trade-off between linearity and noise figure. NEGATIVE FEEDBACKFor reasons of linearity inverting negative feedback amplifiers ( Figure 2) are widely used in receiver architectures.