Robin Dahlbäck

A System for THz Imaging of Low-Contrast Targets Using the Born Approximation

A THz imaging system, operating at 346 GHz and tailored for implementation of an imaging algorithm based on the Born approximation, is presented. The imaging algorithm provides focusing by compensating for the antenna footprint. This allows for using a more simple antenna system without optical focusing. Several aspects of implementing an imaging algorithm based on the Born approximation in THz imaging are discussed and key system properties are highlighted. The performance of the imaging algorithm is verified by imaging two simple dielectric targets. The results indicate that this approach provides a qualitative indication of the distribution of contrast in the samples complex permittivity and is a potential complement to existing imaging techniques.

Compact 340 GHz homodyne transceiver modules for FMWC imaging radar arrays

We present a solution where one single LO chain is used to feed a homodyne FMCW radar transceiver. An InGaAs pHEMT active frequency multiplier MMIC (x8) and a Schottky diode frequency doubler make up the LO chain. The novel Schottky diode based transceiver operates both as a frequency multiplier (x2) and as a sub-harmonic mixer. The modules operate at a center frequency of 340 GHz with a 30 GHz modulation bandwidth. An output power of 0 dBm, an IF noise level of -168 dBm/Hz and a receiver conversion loss of 18 dB is achieved in the band. The form factor of the modules is adapted to build one- or two-dimensional FMCW radar arrays. State of the art system performance is achieved while system complexity, size and cost is significantly reduced.

Comparison of Full 3D and Unit Cell Models for Waveguide-Embedded Frequency Multiplier Arrays

We present a full wave, large-signal analysis of a waveguide-embedded frequency multiplier array, solving the entire geometry using FEM EM modeling and including every nonlinear element in a Harmonic Balance simulation. The full 3D model employed provides the exact field distribution across the array, thus enabling us to account for substrate resonances, higher order mode excitation, instabilities, and diode yield. The model is compared with measurements on a 247 GHz fixed tuned 72-diode HBV tripler. In this example, higher order mode excitation was found due to the interaction between the filter and the diode array. This can only be observed using a full 3D model, which more accurately predicts the output power versus input power and frequency. Finally, the pros and cons of a full 3D model and a unit cell model for waveguide embedded multiplier arrays are discussed.

Integrated terahertz electronics for imaging and sensing

We present the development of integrated submillimeter wave receivers and transmitters based on Schottky- and HBV-diode technology at Chalmers University of technology.

A single-channel THz imaging system for biomedical applications

Due to technological advances, imaging in the THz-range of the electromagnetic spectrum is currently emerging as an interesting tool for security, safety, and biomedical applications. In this paper, a THz imaging system designed for biomedical analysis is described. The system consists of a pair of antennas operating in transmission mode at 335 GHz. The antennas can be moved independently of each other and a tomographic imaging algorithm is used to reconstruct the images.

A 340 GHz CW non-linear imaging system

A CW sub-millimetre wave imaging system is presented. The system operates around 340GHz with a 6.5% relative bandwidth and uses a non-linear imaging algorithm.