Dominik Wrana

Zusammenfassung

This work presents the design and analysis of a low-noise, 24 V input and variable output voltage, 2.1 MHz DC/DC converter based on a 100 V, 70 mOhm Gallium Nitride (GaN) monolithic half-bridge with maximum 1 A converter output current up to 15 V. The converter can be used as variable and highly efficient DC power supply of GaN solid state power amplifiers (SSPA) in E-band as opposed to the conventional low dropout regulators, improving the overall SSPA power efficiency. The converter (0.036 in³) achieves an overall efficiency of above 80 % over nearly the whole output voltage range and a peak efficiency of > 91 %, depending on the gate resistor, at a power density of above 300 W/in³. The achieved voltage peak amplitude varies from below 20 mV to above 200 mV, again strongly depending on the value of the gate resistor. The AC voltage ripple is below 2 mV for all converter designs, making it suitable for low-noise supply of the power amplifiers drain terminals and to replace the conventional inefficient low-dropout voltage regulators. A comprehensive analysis of the tradeoff between switching speed, efficiency and high-/low frequency voltage noise is carried out to highlight the potential of GaN based low-noise DC/DC supplies. Finally, measurements are performed with different DC supplies (LDO, switch-mode power supply unit, and the GaN DC/DC converter from this work) with an E-band transmission chain to demonstrate the usability of this approach. It can be seen that the GaN DC/DC converter supplies the SSPA with no difference to the state-of-the-art solutions and does not cause any oscillations/instabilities, but can increase the efficiency of the power amplifier by 40 %.

Zusammenfassung

This paper presents the sensitivity analysis of a superheterodyne terahertz link specifically designed for applications using the IEEE802.15.3d standard. With its wide frequency range for LO input signals in conjunction with an IF frequency range spanning over the full E-band, frequency-domain multiplexing of RF channels in the frequency range between 285 and 312GHz is implemented in line with the frequency standard. In view of determining optimum operating conditions and performance limitations of the MMIC-based THz transmitter and receiver the link is characterized by a back-to-back operation of the transmitter and receiver modules using WR-3.4 waveguide interconnects. Custom E-band frequency extensions provide the intermediate frequency continuous wave or modulated signals with data rates of up to 32 Gbit/s using 32-QAM modulation. The linearity of the presented THz link enables the use of modulation schemes as high as 256-QAM with reduced bandwidths.

Zusammenfassung

This paper presents experimental results of a shortrange real-time full-duplex wireless link operating at frequencies between 285 and 315GHz. Using modems with integrated E-band frontends in conjunction with H-band transmitters and receivers a super-heterodyne link architecture is implemented. Over a line-of-sight distance of 0.5 meter a maximum troughput of 11.09Gbps is achieved using complex modulation formats as high as 64-QAM. The wide LO input frequency tuning range of the H-band transmitter and receiver modules from 70 to 76.5GHz as well as the availability of multiple modem channels with up to 2GHz bandwidth enable the compatibility of the link with the IEEE802.15.3d frequency standard and its channels 15 through 28. The testbed is operated with two standalone PCs generating, sending, receiving and processing real traffic data over a 10Gbps Ethernet connection to the modems.

Zusammenfassung

Recently it has been demonstrated that an optoelectronic phase-locked loop (OEPLL) using a mode-locked laser as a reference oscillator achieves significantly lower phase noise than conventional electronic frequency synthesizers. In this paper a concept for an OEPLL-based frequency synthesizer is presented and it is investigated how it can be used as a local oscillator (LO) for THz transceivers in order to improve the signal quality in THz wireless communications. The concept of the OEPLL is presented and it's measured phase noise is compared to the phase noise of a laboratory-grade electronic frequency synthesizer. The measured phase noise spectra of both synthesizers at 10 GHz are then used to model LO phase noise at 320 GHz. Based on models of generic zero-IF transmit and receive frontends, THz signals with different modulation formats and Baud rates are simulated at system level using the modeled LO phase noise for the two LO approaches. Finally, the results are compared.