Melusine Pigeon

Design of a Super Directive Four-Element Compact Antenna Array Using Spherical Wave Expansion

In this paper, a super directive four-element compact parasitic antenna array has been designed and optimized using an ad hoc procedure based on the Harrington maximum directivity definition and spherical wave expansion. The complete design procedure (i.e., calculation of the optimum excitation coefficients and equivalent impedance loads associated to each parasitic element) is presented and validated through full-wave electromagnetic simulations. The proposed array has been designed at 868 MHz; its electrical size is 0.45λo × 0.36λo (diameter of minimum sphere circumscribing the antenna equal to 0.57λo). A prototype has been built and tested to demonstrate the effectiveness of this design. A maximum directivity of 11.7 dBi has been measured at 871 MHz in satisfactory agreement with theoretical results and electromagnetic simulations.

Super directive compact antenna design using spherical wave expansion

This contribution presents a method for the design of super directive compact antenna arrays and parasitic antenna arrays based on spherical wave expansion. The optimization procedure has been derived starting from the maximum directivity formula demonstrated by Harrington (D = N2 + 2N) and has been applied for the optimization of a three- and a five-element compact antenna array of 0.4λ0×0.25λ0 constant maximum size. A maximum directivity of 10.4 and 14.5 dBi has been obtained by full-wave simulations in excellent agreement with theoretical results.

Comparative Study of Sub-THz FSS Filters Fabricated by Inkjet Printing, Microprecision Material Printing, and Photolithography

This paper reports a comparative study of sub-THz frequency-selective surface (FSS) filter performance in relation to its method of fabrication. Three techniques are considered: conventional inkjet printing, microprecision inkjet printing, and photolithography. The complete design process is presented highlighting steps from substrate selection through to electromagnetic modeling and finally broadband THz filter characterization. Electromagnetic modeling is performed using the CST full-wave frequency-domain solver. Experimental characterization of substrate material, ink, and final FSS designs is done both by THz time-domain spectrometry and quasi-optically at WR-10 and WR-3 waveguide bands using PNA-X vector network analyzer. The center frequencies for bandpass FSS filters are 100 and 300 GHz, which enables prospective utilization in a quasi-optical multiplier system.

Planar quasi-optic THz source: The multenna

The design of a planar quasi-optical frequency multiplier to 300 GHz is described. This source is formed from slot ring antenna on a PTFE substrate loaded with a Schottky diode operating as a tripler. The antenna simultaneously receives at 100 GHz, transmits at 300 GHz and provides the appropriate impedance matching at both frequencies. This combination of an innovative receive antenna, a frequency multiplier and an output antenna is termed a multenna.

Measurements of non-linear sub-THz quasi-optical devices

The paper presents recent developments in designing quasi-optical multipliers in the sub-THz frequency domain. An extensive measurement campaign is described in detail in which issues are addressed concerning the non-trivial nature of the problems met. In particular, attention is paid to impedance measurements of the core element, the integrated antenna-multiplier (dubbed the ‘multenna’), together with the associated experimental apparatus for detection of its higher-order harmonics. Finally, use of a light-sensitive semiconducting organic polymer is demonstrated as a tuneable dielectric that will enable elements of a multenna array to be phase-locked for generation of coherent emission.

Higher harmonic generation: Coupling two radiating elements at two different frequencies

This paper describes how two radiating elements designed for two different resonating frequencies can be coupled to properly radiate a higher harmonic frequency. The placement of the higher frequency resonating element is chosen by considering the electric filed distribution in the lower frequency antenna. This combination establishes enhanced radiation efficiency at 300 GHz (i.e. the third harmonic of the fundamental).