A 2.4 GHz ULP OOK Single-Chip Transceiver for Healthcare Applications

Abstract

This paper describes an ultra-low power (ULP) single chip transceiver for wireless body area network (WBAN) applications. It supports on-off keying (OOK) modulation, and it operates in the 2.36-2.4 GHz medical BAN and 2.4-2.485 GHz ISM bands. It is implemented in 90 nm CMOS technology. The direct modulated transmitter transmits OOK signal with 0 dBm peak power, and it consumes 2.59 mW with 50% OOK. The transmitter front-end supports up to 10 Mbps. The transmitter digital baseband enables digital pulse-shaping to improve spectrum efficiency. The super-regenerative receiver front-end supports up to 5 Mbps with -75 dBm sensitivity. Including the digital part, the receiver consumes 715 μW at 1 Mbps data rate, oversampled at 3 MHz. At the system level the transceiver achieves PER=10 (-2) at 25 meters line of site with 62.5 kbps data rate and 288 bits packet size. The transceiver is integrated in an electrocardiogram (ECG) necklace to monitor the heart's electrical property.

Introduction to Ultra Low Power Transceiver Design

“…One possible method to utilize a PLL in an energy-constrained system is to duty-cycle its operation as shown in [12,13]. Figure 3 shows a representative binary FSK (BFSK) transmitter topology where a PLL is locked to an oscillator only prior to transmitting data [12].…”

“…Duty-cycling, however, still does not address the issue that low output power designs naturally achieve superior E bit . To facilitate a more fair comparison between competing designs, E bit can be normalized by the radiated output power to create the following normalized energy-per-bit figure of merit [13,45]:…”

“…Receivers are categorized into three architectures: Clocked-demodulators [13,[34][35][36][46][47][48][49][50][51][52][53][54], envelope-detectors [3,22,23,30,39,55], and super-regenerative [19,26,32,41,56,57]. Figure 17 shows that some clocked-demodulator-based receivers consume just as low power as envelope-detector-based and super-regenerative receivers by replacing a PLL with a high-Q resonator [34], or turning off the PLL during the receiver operation [13]. Figure 18 shows that super-regenerative receiver and clocked demodulator architectures attain similar levels of performance given the trade-off between sensitivity and energy-per-bit.…”

A 78 pW 1 b/s 2.4 GHz radio transmitter for near-zero-power sensing applications

“…Most recent work in low-power RF circuits describe excellent RF performance while requiring only on the order of a few tens to hundreds of picojoules to send or receive a bit of information [3]- [5]. Such radios are, however, typically optimized for sensor networks and body-area networks at data rates greater than 100 kb/s.…”

Ultra-low power sensor platform with wireless charging system

“…Super-regenerative receiver is one of promising candidates for ultra-low power architecture [8], [9]. In the super-regenerative receiver, signals are injected to an amplification circuit which has a frequency selective filter in its positive-feedback loop.…”