A differential IR-UWB transmitter using PAM modulation with adaptive PSD

Abstract

The current state of the telecommunications market exhibits a high potential to absorb efficient innovations in wireless connectivity, especially those that can be applied to the Internet of Things and similar domains. Contributing in that direction, this paper describes the design and implementation of a fully differential impulse-radio ultra-wideband (IR-UWB) transmitter using pulse-amplitude modulation, with an adaptive power spectrum density (PSD). The architecture can produce up to eight differential monocycles per clock pulse at its output. The number of monocycles controls the bandwidth (thus the PSD) in the mask of IR-UWB technologies, allowing adaptation to multiple standards. The complete transmitter has four main blocks: (a) a pulse generator, comprising two pulse generating circuit groups, to modulate and create a rectangular waveform; (b) an active balun with two amplifiers, to generate differential signals; (c) a digital demultiplexer, to alternate data to the pulse generating circuit groups; (d) a binary-to-thermometer decoder, to control the amount of generated monocycles per pulse. Simulations demonstrate an output pulse amplitude of 120 mV for the high logic level and of 70 mV for the low logic level, both at a 100 MHz Pulse Repetition Frequency. This produces a mean pulse duration of 277 ps, a mean central frequency of 3.8 GHz, and a mean power consumption 6.7 mW. The transmitter takes the form of an intellectual property core in a 130 nm CMOS technology. The complete transmitter area is 0.067 mm $$^2$$ , without I/O pads. The outcomes suggest that the proposed circuit can narrow or widen the output signal bandwidth, providing adaptability to different emission requirements.