Design of Circuits to enhances the performace of high frequency planar Gunn diodes

The project contains adventurous research, with an aim to understand and design a planar Gunn diode with a novel integrated circuit configuration to extract the 2nd harmonic. This will potentially enhance the Gunn diode as a high frequency source towards frequencies in excess of 600 GHz. The RF performance from the above integrated circuit was achieved by design and simulation of radial and diamond stub resonators, which were used to short the fundamental oscillation frequency while allowing the second harmonic frequency to pass through to the load. The diamond stub resonator is a new configuration offering a number of advantages which include a higher loaded quality factor and occupies 55% less chip area than a comparable radial stub resonator. The designed novel circuits with integrated planar Gunn diode were fabricated using microwave monolithic integrated circuits (MMIC) technology at the James Watt Nanofabrication centre in Glasgow University. Full DC and microwave characterisation of the diodes and integrated circuits with diodes was carried out using a semiconductor analyser, network analyser (10 MHz to 110GHz) and spectrum analyser (10 MHz to 125GHz). The microwave measurements were carried out at the high frequency RF laboratories in Glasgow University. Both GaAs and InP based Gunn diodes were characterised and RF characterisation work showed that higher fundamental frequencies could be obtained from Gunn diodes fabricated on InGaAs on a lattice matched InP substrate. Planar Gunn diodes with an anode to cathode spacing of 4 microns giving a fundamental frequency of oscillation of 60 GHz were fabricated as an integrated circuit with coplanar waveguide (CPW) circuit elements to extract the second harmonic. A second harmonic frequency of 120 GHz with an RF output power of -14.11 dBm was extracted with very good fundamental frequency suppression. To the authors knowledge this was the first time second harmonic frequencies have been extracted from a planar Gunn diode technology. Aluminium gallium arsenide (AlGaAs) planar Gunn diodes were also designed with an integrated series inductor to match the diode at the fundamental frequency to obtain higher RF output powers. Devices with a 1 micron anode to cathode separation gave the highest fundamental oscillation frequency of 121 GHz the highest reported for a GaAs based Gunn diode and with an RF output power of -9 dBm. These circuits will have potential applications in secure communications, terahertz imaging etc. The research programme was in collaboration with the University of Glasgowwould like to thank the staff of the James Watt Nanofabrication Centre at the University of Glasgow for help in fabricating the devices which is reported in this thesis. ‘Part of this work was supported by ESPRC through EP/H011862/1, and EP/H012966/1

Experimentally estimated dead space for GaAs and InP based planar Gunn diodes

The authors would like to thank the staff of the James Watt Nanofabrication Centre at the University of Glasgow for help in fabricating the devices which is reported in this paper. ‘Part of this work was supported by ESPRC through EP/H011862/ 1, and EP/H012966/1.Peer reviewedPublisher PD

Prototype for multidisciplinary research in the context of the Internet of Things

The Internet of Things (IoT) poses important challenges requiring multidisciplinary solutions that take into account the potential mutual effects and interactions among the different dimensions of future IoT systems. A suitable platform is required for an accurate and realistic evaluation of such solutions. This paper presents a prototype developed in the context of the EPSRC/eFutures-funded project “Internet of Surprise: Self-Organising Data”. The prototype has been designed to effectively enable the joint evaluation and optimisation of multidisciplinary aspects of IoT systems, including aspects related with hardware design, communications and data processing. This paper provides a comprehensive description, discussing design and implementation details that may be helpful to other researchers and engineers in the development of similar tools. Examples illustrating the potentials and capabilities are presented as well. The developed prototype is a versatile tool that can be used for proof-of-concept, validation and cross-layer optimisation of multidisciplinary solutions for future IoT deployments

An electrical equivalent circuit to simulate the output power of an AlGaAs/GaAs planar Gunn diode

The planar Gunn diode offers the potential of microwave, milli-metric and THz based oscillator which can be fabricated as part of a microwave monolithic integrated circuit (mmic). To-date the RF output power has been too low for many applications. This paper looks at a simple electrical equivalent circuit model representation of an aluminium gallium arsenide (AlGaAs) based planar Gunn diode with an active channel length of approximately 4μm and width of 120μm. The model indicated a maximum RF output power of +5dBm compared with published experimental results of –19dBm for similar diodes

Analysis of a near field MIMO wireless channel using 5.6 GHz dipole antennas

Understanding the impact of interference upon the performance of a multiple input multiple output (MIMO) based device is of paramount importance in ensuring a design is both resilient and robust. In this work the effect of element-element interference in the creation of multiple channels of a wireless link approaching the near-field regime is studied. The elements of the 2-antenna transmit- and receive-arrays are chosen to be identical folded dipole antennas operating at 5.6 GHz. We find that two equally strong channels can be created even if the antennas interact at sub-wavelength distances, thus confirming previous theoretical predictions

Analysis of a near field MIMO wireless channel using 5.6 GHz dipole antennas

Understanding the impact of interference upon the performance of a multiple input multiple output (MIMO) based device is of paramount importance in ensuring a design is both resilient and robust. In this work the effect of element-element interference in the creation of multiple channels of a wireless link approaching the near-field regime is studied. The elements of the 2-antenna transmit- and receive-arrays are chosen to be identical folded dipole antennas operating at 5.6 GHz. We find that two equally strong channels can be created even if the antennas interact at sub-wavelength distances, thus confirming previous theoretical predictions

Analysis of nonstationary emissions for efficient characterization of stochastic EM fields

A statistical approach using field-field correlation functions which is obtained from two-probe time domain measurement is used to characterize the radiation from complex devices. The time-frequency analysis provided by the measurement data has shown that significant emissions may only occur for a few percent of the time and a piecewise stationary model of emissions may be most appropriate. In this paper, a sorting technique is applied to short time segments of the nonstationary time-domain data provided by the measurements. These short time segments are sorted into groups according to the characteristics of the emissions, i.e. different emission processes, with the assumption that the stochastic emissions is stationary within each group (process). The ensemble of time segments associated with each group may then be used to obtain the fieldfield correlations for each process. Results of the analysis give promising insights into how to characterize complex and time dependent systems

An electrical equivalent circuit to simulate the output power of an AlGaAs/GaAs planar Gunn diode

The planar Gunn diode offers the potential of microwave, milli-metric and THz based oscillator which can be fabricated as part of a microwave monolithic integrated circuit (mmic). To-date the RF output power has been too low for many applications. This paper looks at a simple electrical equivalent circuit model representation of an aluminium gallium arsenide (AlGaAs) based planar Gunn diode with an active channel length of approximately 4μm and width of 120μm. The model indicated a maximum RF output power of +5dBm compared with published experimental results of –19dBm for similar diodes

Analysis of nonstationary emissions for efficient characterization of stochastic EM fields

A statistical approach using field-field correlation functions which is obtained from two-probe time domain measurement is used to characterize the radiation from complex devices. The time-frequency analysis provided by the measurement data has shown that significant emissions may only occur for a few percent of the time and a piecewise stationary model of emissions may be most appropriate. In this paper, a sorting technique is applied to short time segments of the nonstationary time-domain data provided by the measurements. These short time segments are sorted into groups according to the characteristics of the emissions, i.e. different emission processes, with the assumption that the stochastic emissions is stationary within each group (process). The ensemble of time segments associated with each group may then be used to obtain the fieldfield correlations for each process. Results of the analysis give promising insights into how to characterize complex and time dependent systems

Analysis of a near field MIMO wireless channel using 5.6 GHz dipole antennas

Understanding the impact of interference upon the performance of a multiple input multiple output (MIMO) based device is of paramount importance in ensuring a design is both resilient and robust. In this work the effect of element-element interference in the creation of multiple channels of a wireless link approaching the near-field regime is studied. The elements of the 2-antenna transmit- and receive-arrays are chosen to be identical folded dipole antennas operating at 5.6 GHz. We find that two equally strong channels can be created even if the antennas interact at sub-wavelength distances, thus confirming previous theoretical predictions