Wideband CMOS Receiver with Integrated Filtering and a Current-Mode Sigma-Delta Analog-to-Digital Converter

A wideband receiver with tunable integrated filtering that attenuates out-of-band interferers is proposed. This receiver operates in current-mode, has very low power, small area, low cost, and can be fully integrated on a single chip. A key block of the receiver analog front-end, the low-noise amplifier (LNA), is studied in depth. This circuit consists of a widely tunable narrowband balun-LNA, which performs conversion from single-ended to differential, and includes two integrated high-Q bandpass filters that filter undesired interferers at the receiver's input. This circuit is very compact and avoids the use of inductors and of an external balun, which would increase the power consumption and the die area. To convert the IF current signal to the digital domain, avoiding the use of a transimpedance amplifier, which occupies a large die area and increases the receiver noise figure and power consumption, a current-mode sigma-delta analog-to-digital converter is directly connected to the analog front-end output. The receiver is designed for possible use in the wireless medical telemetry service (WMTS) and in ISM bands from 450 MHz to 900 MHz. The complete analog front-end has NF of 8 dB, +11.6 dBm out-of-band IIP3, and has a power consumption of 3 mW. The sigma-delta analog-to-digital converter connected to the proposed receiver analog frontend has a peak SNDR of 43.2 dB, which is equivalent to a resolution of approximately 7 bits. The complete receiver has a DC power consumption of 3.3 mW for a 1 V supply voltage.