Millimeter-Wave Impulse Radio

Abstract: This thesis investigates the opportunity of wireless multi-gigabit per second communication at the millimeter-wave (mmW) frequencies around 60 GHz by using impulse radio and nanoelectronics. Today most wireless communication take place in the microwave region, where several different systems and applications are crowding the narrow-band channels. Complicated schemes are applied in order to avoid interference and still provide good performance in terms of bit rate. Many regulatory associations have allocated a wide unlicensed frequency band around 60 GHz, which may offer the possibility to build short-range wireless systems that provide high throughput. Wireless high definition multimedia interface (HDMI) and fast synchronization of mobile devices are some of the intended applications. Furthermore, remote sensing applications such as radar, imaging and localization may be considered due to the wide bandwidth, which may offer high resolution. The impulse radio front-ends that are presented in this thesis are monolithic microwave integrated circuit (MMIC) designs in compound semiconductor materials, such as GaAs and InGaAs, compounds built from groups III-V of the periodic system. By choosing such compound materials, it is possible to design devices with high performance such as III-V metal-oxide-semiconductor field-effect transistors (MOSFETs) with mmW cut-off frequency and high transconductance. Moreover, it is possible to utilize bandgap-engineered devices with unique properties such as resonant tunneling. The presented transmitters incorporate resonant tunnel diodes (RTDs) that provide negative differential conductance, and may be used to generate substantial amount of mmW signal power by integrating the device in a resonance circuit, an oscillator. Furthermore, the addition of a third gating terminal to the RTD will present control over both the magnitude and the sign of the differential conductance. By switching the differential conductance of the RTD device between positive and negative magnitudes in a resonance circuit, it is possible to turn the oscillator on and off to generate wavelets, short pulses of radio frequency oscillation. This design offers sub-period start-up time, which is due to the kick-start action of the oscillator. Also, rapid decay is provided since the RTD device actively helps to quench the oscillations when set to positive differential conductance. The best wavelet generator operation was achieved with a MOSFET/RTD combination, where 41 ps long wavelets were generated with 7 dBm peak output power up to a rate of 15 GHz. The wavelet generator was used to investigate the properties of mmW impulse radio and studies show the possibility to obtain 4 Gbps links over short distances using low-level modulationon-off keying. The wavelet generator may also be used as a super-regenerative oscillator by modifying the control signal. Instead of switching the RTD device rapidly into negative differential conductance, it is tuned slowly. Through this action the oscillation may be started from noise or received signal energy. A 400 Msamples/ super-regenerative oscillator is presented, which may be an interesting candidate for implementation in a low-power mmW impulse radio receiver.