Vitaliy Zhurbenko

Terahertz Imaging Systems With Aperture Synthesis Techniques

This paper presents the research and development of two terahertz imaging systems based on photonic and electronic principles, respectively. As part of this study, a survey of ongoing research in the field of terahertz imaging is provided focusing on security applications. Existing terahertz imaging systems are reviewed in terms of the employed architecture and data processing strategies. Active multichannel measurement method is found to be promising for real-time applications among the various terahertz imaging techniques and is chosen as a basis for the imaging instruments presented in this paper. An active system operation allows for a wide dynamic range, which is important for image quality. The described instruments employ a multichannel high-sensitivity heterodyne architecture and aperture filling techniques, with close to real-time image acquisition time. In the case of the photonic imaging system, mechanical scanning is completely obsolete. We show 2-D images of simulated 3-D image data for both systems. The reconstruction algorithms are suitable for 3-D real-time operation, only limited by mechanical scanning.

Coupled Transmission Lines as Impedance Transformer

A theoretical investigation of the use of a coupled line section as an impedance transformer is presented. We show how to properly select the terminations of the coupled line structures for effective matching of real and complex loads in both narrow and wide frequency ranges. The corresponding circuit configurations and the design procedures are proposed. Synthesis relations are derived and provided for efficient matching circuit construction. Design examples are given to demonstrate the flexibility and limitations of the design methods and to show their validity for practical applications. Wideband matching performance with relative bandwidth beyond 100% and return loss RL > 20 dB is demonstrated both theoretically and experimentally. Good agreement is achieved between the measured and predicted performance of the coupled line transformer section.

Design and Realization Aspects of 1-THz Cascade Backward Wave Amplifier Based on Double Corrugated Waveguide

The design and fabrication challenges in the first ever attempt to realize a 1-THz vacuum tube amplifier are described. Implementation of innovative solutions including a slow-wave structure in the form of a double corrugated waveguide, lateral tapered input and output couplers, deep X-ray LIGA fabrication process, and a cascade architecture of the backward wave amplifier are discussed. New knowledge in the field of terahertz vacuum devices brought by intensive simulations and development of advanced fabrication and assembly processes of the micro-structures is highlighted.

A Modified Marchand Balun Configuration With Tunable Phase Balance

In this letter, a novel modified Marchand balun configuration with tunable phase balance is analyzed and verified experimentally. It is proposed to add a shunt susceptance in between the two couplers of the Marchand balun. This allows for a change in the phase balance which, to first order, is linear with the susceptance, while the magnitude balance is kept constant. To verify the proposed configuration, a lumped element Marchand balun has been fabricated using a SiGe BiCMOS technology. The balun design is centered around 9.4 GHz, with an insertion loss of 6.0 dB. The phase difference between the output ports can be changed from 175.8° to 183 ° whereas the magnitude imbalance is kept almost constant at 0.3 dB. The balun performs well in the range from 7 to 11 GHz, where it is possible to tune the phase to exactly 180°.

Broadband Impedance Transformer Based on Asymmetric Coupled Transmission Lines in Nonhomogeneous Medium

A new broadband quarter-wavelength impedance transformer based on an asymmetric coupled line section is presented. The bandwidth of the coupled line transformer is extended with the help of an interconnecting transmission line. An analytical model for the transformer is developed. The analysis of the structure reveals that a fractional bandwidth of more than 100% at -20 dB reflection level can be achieved with such a structure. An experimental transformer circuit has been designed, fabricated and tested. Theoretical and experimental results are fair agreement and confirm the established theory. The achieved bandwidth is almost 3 times larger as compared with standard matching circuits.

European research on THz vacuum amplifiers

The OPTHER (OPtically Driven TeraHertz AmplifiERs) project represents a considerable advancement in the field of high frequency amplification. The design and realization of a THz amplifier within this project is a consolidation of efforts at the international level from the main players of the European research, academy and industry in vacuum electronics. This paper describes the status of the project and progress towards the THz amplifier realization.

Analytical model of planar double split ring resonator

This paper focuses on accurate modelling of microstrip double split ring resonators. The impedance matrix representation for coupled lines is applied for the first time to model the SRR, resulting in excellent model accuracy over a wide frequency range. Phase compensation is implemented to take into account the curved shape of the resonators. The presented results show that the accuracy better than 0.5% for the first four resonances. Analysis of a periodical structure with frequency selective properties is presented.

A model for ferrite-loaded transversely biased coaxial resonators

This work describes a simple model for shortened coaxial cavity resonators with transversely biased ferrite elements. The ferrite allows the resonance frequency to be tuned, and the presented model provides a method of approximately calculating these frequencies to generate the tuning curve in short computation times. A test case resonator is specified, processed by the method, and constructed. Model predictions are compared to the measurement data as well as HFSS simulations. The model is also used for deducing maximum tuneability conditions on resonator parameters.

Reconfigurable diplexer based on switched delay line approach

In this work, a concept for the realization of a reconfigurable microwave multiplexer based on a switched delay-line topology is presented. The multiplexing concept is studied by considering a diplexer example. The topology provides two times reduction in the number of filters in comparison to the conventional directional filter approach. The switched delay-line topology enables the lossy and nonlinear switching elements to be used as a part of the coupling elements rather than within the resonators. Therefore, the diplexer potentially allows for a low insertion loss and high linearity. In addition, independent tuning of channels can be achieved.

A 24 GHz integrated SiGe BiCMOS vital signs detection radar front-end

In this paper a 24 GHz integrated front-end transceiver for vital signs detection (VSD) radars is described. The heterodyne radar transceiver integrates LO buffering and quadrature splitting circuits, up- and down-conversion SSB mixers and two cascaded receiver LNAs. The chip has been manufactured in a 0.25 μm SiGe:C BiCMOS technology and its size is 1390 × 2690 μm2. The transmitter demonstrates a maximum output power at 24 GHz of approximately -30 dBm with an externally applied LO power of 3 dBm. The receiver demonstrates a peak gain of 13.3 dB at 22.15 GHz with >10 dB return loss. The power consumption of the entire transceiver is approximately 164 mW.