Left-handed transmission lines at millimetre and sub-millimetre wavelengths

Co-planar strip (CPS) transmission lines, aimed at operating up to sub-millimetre wavelengths, were periodically loaded by lumped capacitances and inductances in series and shunt configuration, respectively. Under this condition, propagation on the line is backward with group and phase velocities of opposite signs. The transmission lines were fabricated onto a quartz substrate by e-beam patterning and thin film deposition, silicon nitride and gold layers, on a deep sub-micron scale (~200 nm). A direct evidence of left-handedness between 160 and 380 GHz was achieved via the tracking of phase advance in a differential phase experiment using electro-optic sampling. The comparison between modelling results by electromagnetic full wave circuit analysis and experiment was performed in the time and frequency domains. It shows a good agreement in the dispersion characteristics and ultra-fast variations in the transmitted signals. At last, we took benefit of a lumped element fitting approach in order to discuss of the frequency capability of this non-resonant approach     

Fabrication and performance of InP-based heterostructure barriervaractors in a 250-GHz waveguide tripler

High-performance InGaAs-InAlAs-AlAs heterostructure barrier varactors (HBV's) have been designed, fabricated, and RF tested in a 250-GHz tripler block. The devices with two barriers stacked on the same epitaxy are planar integrated with coaxial-, coplanar-, and strip-type configurations. They exhibit state-of-the-art capacitance voltage characteristics with a zero-bias capacitance C₃⁰ of 1 fF/μm² and a capacitance ratio of 6:1. Experiments in a waveguide tripler mount show a 9.8-dBm (9.55-mW) output power for 10.7% conversion efficiency at 247.5 GHz. This is the highest output power and efficiency reported from an HBV device at J-band (220-325 GHz)     

Capacitance engineering for InP-based heterostructure barriervaractor

We investigate new schemes of InP-based heterostructure barrier varactors with the aim of enhancing the capacitance nonlinearity of the devices. Starting from a generic step-like InGaAs/InAlAs/AlAs single barrier heterostructure, planar-doped and buried InAs quantum-well barrier heterostructures were successfully fabricated. It is shown that both solutions lead to more efficient screening of electric field near equilibrium and hence to improvement in the capacitance-voltage ratios with values as high as ~7:1. Under bias, the capacitance modulation is governed by an escaping mechanism in contrast to the conventional depletion operation mode observed for conventional varactors     

A taper filtering finline at millimeter wavelengths for broadband harmonic multiplication

The design of a taper filtering finline aimed at simultaneously mode matching and frequency selecting multifrequency signal is presented. Based on the superimposition of a smoothly corrugated taper and a sinusoidal-shaped filter, a low insertion loss (L<0.1 dB) at W band [75:110] GHz and a high rejected stop band in the third harmonic range (R band [225:330] GHz) are demonstrated. Both sections are numerically optimized using chain matrix techniques and assessed by means of full three-dimensional electromagnetic simulations.     

Monolithic coplanar transmission lines loaded by heterostructurebarrier varactors for a 60 GHz tripler

Nonlinear transmission lines (NLTLs) loaded by InP-based heterostructure barrier varactors (HBVs) have been fabricated in a monolithic coplanar technology for the first time. The devices were designed for a tripler with a 60 GHz; output frequency. The single HBV diodes, fabricated in a dual barrier scheme, exhibit a capacitance ratio of 6:1, a normalized capacitance of 1.4 fF/μm² and a voltage breakdown in excess of 10 V. Under moderate pumping (20 dBm), a tripling operation with 30% bandwidth was demonstrated with unsaturated conversion efficiency (1%) for a eight-HBV prototype