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This paper deals with the development of a four-channel low-power Phased Array Front-End (PhA-FE) at 24 GHz, targeting both low-power radar sensors and battery powered transceiver applications. Typically, PhA-FEs are power hungry architectures due to multiple parallel RF channels in the FE and complex algorithms for beam steering or high bit-rate demodulation in the digital part. In contrast, we target in this paper applications where both beam steering algorithms and data demodulation are relatively simple and hence achievable with low-power digital signal processing. More specifically, we report on four significant building blocks of the architecture, a Low Noise Amplifier (LNA), a Vector Modulator Phase Shifter (VMPS), a Quadrature Voltage Controlled Oscillator (QVCO) and an Analogue to Digital Converter (ADC) that have been designed the first three in 90nm and the last in 180nm CMOS technology. The LNA shows 24.4 dB gain, 3.4 dB NF and −24.4 dBm input P1dB. The single quadrant VMPS has more than 90° of phase control range and shows less than 0.7 dB of gain variation over phase shifting. The QVCO which consumes less than 32mW, buffer included, has a tuning range of 8%. The 6bit 20 MS/s ADC consumes 1.8mW. [ABSTRACT FROM PUBLISHER]

Piezoelectric harvesters are considered an alternative power source for applications that can support low to medium data rate transmissions in wireless sensor networks where ambient vibrations can provide microwatts to milliwatts of power. In this paper, we report the design and performance of a proof-of-concept (POC) autonomous sensor-node prototype including: an in-house piezoelectric harvester; a power management unit (PMU) made of discrete components; and an in-house ultra-wide band impulse radio (UWB-IR) transmitter. The piezoelectric harvester provides 54µW at 3.3Vrms at 450 milli-g and resonant frequency of 160 Hz. In these conditions, it was observed that the sensor node is capable of sending 1 burst of 100 pulses every 110 seconds consuming an average of 8.2µW, which is much less than the generated energy. The POC sensor node using kinetics energy harvester shows energy autonomy, thus opening range of possibilities for sub 100µW energy harvesting wireless sensor nodes. [ABSTRACT FROM PUBLISHER]