We have developed precision micromachining techniques for integration of terahertz quantum cascade lasers (QCLs) with waveguides and feedhorns for use as local oscillators in satellite-borne receivers. We demonstrate these techniques using QCLs at 3.4 THz and 4.7 THz, as well as the first QCL with a monolithically integrated power modulator.

AbstractAntenna-pattern measurements obtained from a double-metal supra-terahertz-frequency (supra-THz) quantum cascade laser (QCL) are presented. The QCL is mounted within a mechanically micro-machined waveguide cavity containing dual diagonal feedhorns. Operating in continuous-wave mode at 3.5 THz, and at an ambient temperature of ~60 K, QCL emission has been directed via the feedhorns to a supra-THz detector mounted on a multi-axis linear scanner. Comparison of simulated and measured far-field antenna patterns shows an excellent degree of correlation between beamwidth (full-width-half-maximum) and sidelobe content and a very substantial improvement when compared with unmounted devices. Additionally, a single output has been used to successfully illuminate and demonstrate an optical breadboard arrangement associated with a future supra-THz Earth observation space-borne payload. Our novel device has therefore provided a valuable demonstration of the effectiveness of supra-THz diagonal feedhorns and QCL devices for future space-borne ultra-high-frequency Earth-observing heterodyne radiometers.

Terahertz-frequency quantum-cascade lasers (THz QCLs) are compact, electrically-driven sources of narrowband radiation in the ~2-5-THz band. Numerous scientifically important gas-phase species within the Earth's upper atmosphere have distinctive spectral features within this band, making QCLs attractive sources for spectroscopic and radiometric atmospheric studies. In this paper, we demonstrate the integration of a QCL with a satellite-compliant cryocooler, precision-micromachined waveguide, a pair of diagonal feedhorns and a Cassegrain telescope, as key steps toward a complete 3.5-THz integrated receiver system.

In this work we describe the design and operation of a scatterometer to be used at the European Space Agency. The instrument has the purpose to characterize smooth as well as rough materials, in transmission and reflection in the 50-750 GHz frequency range. We first discuss some of the design challenges encountered during the design, and later show some of the initial measured results.

This paper describes the detailed electromagnetic modelling and design of a scatterometer to be used at the European Space Agency, for characterization in transmission and reflection of smooth as well as rough materials in the 50–750 GHz region. The scatterometer is analysed with the software GRASP. The initial design based on quasi-optics showed poor performances and was thus modified significantly, obtaining improvements in beam quality, beam displacement and cross-polar performance.

A scatterometer operating in the bands from 50 to 750 GHz has been designed and fabricated. Operation in the different bands is achieved by using a Network Analyser with appropriate frequency extenders and corrugated horns. The beam is propagated using reflective quasi-optics on two levels with the sample being mounted on the lower level. The two levels are connected by a rotating periscope which collects the scattered radiation from the sample and transfers it to the upper level where the phase and amplitude are measured by the Network Analyser. The scatterometer can measure in both reflection and transmission and in VV, HH, VH and HV polarisations. During a measurement the Network Analyser heads and associated cables remain static to prevent drift. Rough reference samples have been developed for testing the scatterometer and preliminary results are reported in the 50–75 GHz band.

This paper presents the results of the antenna pattern measurements conducted on the Ice Cloud Imager 664 GHz feed horn at the ESTEC Sub-mmwave Scanner (SmS) in support to the ICI instrument of the MetOp-SG program. Very good agreement between simulations and measurements was obtained, both in the co- and cross-polar component. The measured peak directivity was 26.28 dBi ± 0.13 dB while the simulated one was 26.35 dB.

This paper provides an overview of the (sub) mm wave testing capabilities at the European Space Agency and contributes the efforts of the community in the estimation of measurement uncertainty for antenna testing in the THz domain.

We present the first antenna power measurements from a double metal terahertz-frequency quantum cascade laser (THz QCL) mounted within a waveguide cavity and incorporating dual diagonal feedhorns that enable directional output coupling of THz radiation from both laser facets. The feedhorn antenna patterns have been measured simultaneously at a frequency of 3.5 THz and with the QCL operating at an ambient temperature of 60 K in continuous wave mode. Comparison with a feedhorn theoretical model shows good pattern correlation and implies that the QCL signal is likely propagating within the waveguide in a fundamental mode.

Single and double layer frequency selective surfaces (FSS) for Circular polarization (CP) operation were designed. The designed FSS provide reflection in the Ku-band (11.7-12.75 GHz) and transmission in the Ka-band (17.3-20.2 GHz). CP is conserved in each of the bands. For the double layer design over the Ku-band the reflection loss was less than 0.05 dB for TE and TM polarizations while the axial ratio was below 0.2 dB. Over the Ka-band transmission loss and axial ratio were each less than 0.25 dB.

This paper will present the status of the high gain antenna currently under development for the European Space Agency Exomars program. The ESA ExoMars program is the first mission in ESA's Aurora Exploration Program and is one of the exploration missions to be undertaken in the near future. The first mission is scheduled to be launched in 2016 and will focus on exobiology studies as it will collect new information on Mars environment in preparation for future human exploration. The second mission will be launched in 2018. The 2016 mission will be launched by a Roscosmos supplied Proton-M/Breeze-M rocket. It will carry a 600 kg Entry, Descent and Landing Demonstrator module with sensors to characterize the entry, descent & landing, and the surface environment at the landing site. A Payload Science package consisting of 4 instruments, from Europe and Russia will be accommodated on the ExoMars Orbiter to support the search and localization of trace gasses including Methane sources on Mars.

In this paper, the accuracy of the Quasi-Optical free-space test bench for reflectivity measurements at W-band and 110-170 GHz is evaluated. A sample from the MADRAS (Microwave Analysis and Detection of Rain and Atmospheric Structures) Spaceborne Radiometer already measured at the Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS) (Nizhniy Novgorod, Russia) was used as reference. Two calibration procedures are considered in order to improve the accuracy of the measurements.

An instrument has been designed which is capable of measuring scattering from 0.075-0.5 THz. This will enable a more accurate determination of the optical properties of materials by correcting for scatter and also the characterisation of the mechanical properties of the surface. Models have been investigated to help in experimental design and in reducing the number of required measurements by extrapolation. The Generalized Harvey Shack (GHS) method has been evaluated for this purpose. Predictions for 40 grit gold coated sandpaper at 37 degrees incidence angle and 0.8 THz are made showing the surface to be almost completely diffuse. The GHS method was compared to the Integral Equation Model (IEM).

The use of capacitive metal-mesh structures on polypropylene substrates is routinely used in far infrared astronomy for the purpose of spectral low-pass filtering. The transmission of these filters well below their cut-off frequency follows the well known behavior of a Fabry-Perot etalon due to the fairly achromatic nature and finite thickness of the embedding substrate. We show how it is possible to reproduce to a good level of precision, the predicted transmission of an embedded stack of layers of a given square-geometry using Transmission Lines when compared to HFSS simulations. We then use the Fabry-Perot etalon model to invert their spectral behavior to extract an effective index of refraction corresponding to the mesh geometry and device thickness. This injective mapping allowed us to design a Gradient Index lens based on a fixed spacing (or grid) while varying the mesh filling factor. Measurements of such a flat lens-filter (or lenster) are shown.

A prototype gradient index lens has recently been produced by using a stack of frequency selective surfaces, based on a square patch unit cell. The lens was modelled using a transmission line method(TLM) and HFSS. Additional measurements have been taken using a VNA which allows for detailed magnitude and phase information at precise frequencies. The lens has a broadband performance due to non resonating metamaterial structure used. A proposed solution is given to increase the performance of the GRIN lens by the use of antireflection coating built into the design of the lens.

A detailed broadband analysis of the resonant absorptions of different common explosives in the range from 0.1-6 THz is presented. Dependencies of the resonance features on different sample parameters are evaluated via spectroscopic investigation of transmission and reflection. A significant dependency on the manufacturing process is observed.

The design of dual-optics circular-polarization offset reflectors has been addressed by using circular polarization selective surfaces (CPSS). A novel design of CPSS based on Pierrot's cells is proposed, and design guidelines and limitations of this technology are given. Manufacture constraints are discussed and a more reliable fabrication process is developed. A 29×29 array has been constructed and measurements are ongoing.

In this paper accurate material measurements at sub-millimetre wave frequencies performed with two different systems are compared. Transmission and reflection results of high quality samples measured with a quasi-optical open resonator and a quasi-optical free-space bench are presented. Based on the comparison between the two results, an accuracy assessment of the transmission set-up is performed.

This contribution analyzes several multi-frequency antenna systems based on meta-surfaces. As it is demonstrated, there is a synergy between the frequency-domain behavior of the meta-surface and multi-frequency antenna architectures. Therefore, the use of the meta-surface is not restricted to enhance the radiation properties of the single-antenna element, but also contributes at system level aspects such us isolation and compactness.

The field of antenna measurements is lacking a Golden Standard, i.e. an antenna of which the pattern is known by definition. To gain confidence in the performance of a range, including the procedures and skills of the operators, range comparison has been a popular tool for over three decades. In the beginning, ad-hoc available antennas were shipped around the various ranges. Soon it became clear that the comparisons were restricted by the properties of the antenna. The European Space Agency (ESA) stimulated and supported the development of a dedicated VAlidation STandard (VAST) antenna, specifically designed for validation campaigns of antenna measurement ranges.