An Ultra-Small Area and High-Sensitivity Wireless Receiver for ISM and MICS Band Application

Abstract

In this work, a 0.43mm2 high-sensitivity low-intermediate-frequency (low-IF) receiver under $0.18~\mu \text{m}$ technology is reported for Industrial Scientific Medical (ISM) and Medical Implant Communications Service (MICS) band applications, which supports the 2ASK/GFSK demodulation mode. To reduce the area, a low noise amplifier (LNA) with an active inductor, a compact Gm-C filter, an AC current bleeding technique for controlling the receiver gain and, a ring-VCO LO PLL were used, without any passive inductors. The main methods for improving sensitivity are reducing the receiver noise figure (NF) and improving the signal-to-noise ratio for demodulation. Thus, the LNA adopts a two-stage 40 dB gain to suppress the NF of the subsequent stage. An automatic gain control (AGC) loop is used to control the receiver gain to overcome the large signal nonlinearity from the large LNA gains. Additionally, a Gm-C complex filter rejects image and blocks interference, improving the sensitivity to harsh environments. Under the CSMC $0.18~\mu \text{m}$ process, the die of the receiver is only 0.43 mm2 and covers 300–500 MHz, MICS and some ISM bands. The measurement results show that when the internal 2ASK demodulator is adopted, it has a −115 dBm sensitivity at 2 Kbps; and when the external GFSK digital baseband is adopted, it has a −121 dBm sensitivity at 2 Kbps. At 300 Kbps, only 6.5 mW of power is consumed. It is suitable for low-power wide-area network (LPWAN) applications.

Keywords

• Active inductor load LNA
• AGC loop
• Gm-C filter
• ISM/MICS band
• low-IF receiver
• LPWAN