Recent advancement of communication system requires low cost, minimal weight, low profile and high-performance antenna to execute the demand of the future realization. A high gain novel microstrip patch antenna design is proposed, based on the photonic crystal for terahertz (THz) spectral band applications. This antenna is mounted on polyimide substrate that employs Photonic Band Gap (PBG) crystal and the Gain of 7.934 dB, Directivity 8.612 dBi and VSWR close to unity at resonant frequency of 0.6308 THz. The proposed antenna model is compared with homogeneous polyimide substrate structure based microstrip patch antenna and analyzed the radiation characteristics. Moreover, the performance of designed antenna is investigated with different PBG cylindrical distance, PBG hole radius, curvature radius of patch and substrate heights. The projected design antenna has a bandwidth of 36.25 GHz and −10 dB impedance with operating frequency range varying from 0.6152 THz to 0.6514 THz, hence it can be utilized for detection of explosive and material characterization applications.

Design and analysis of novel microstrip patch antenna on photonic crystal in THz

Energy harvesting is well established as one of the prominent enabling technologies [along with radio-frequency identification (RFID), wireless power transfer, and green electronics] for the pervasive development of Internet of Things (IoT). This paper focuses on a particular, yet broad, class of systems that falls in the IoT category of large area electronics (LAE). This class is represented by “smart surfaces.” The paper, after an introductory overview about how smart surfaces are collocated in the IoT and LAE scenario, first deals with technologies and architectures involved, namely, materials, antennas, RFID systems, and chipless structures; then, some exemplifying solutions are illustrated to show the present development of these concurrent technologies in this area and to stimulate further solutions. Conclusions and future trends are then drawn.

Smart Surfaces: Large Area Electronics Systems for Internet of Things Enabled by Energy Harvesting

Terahertz wave radar offers a higher resolution and smaller aperture compared with microwave radar. However, despite the emergence of terahertz sources and detectors suitable for radar front ends, the integration of a phased-array radar system remains challenging due to the lack of phase shifters and circulators, the basic components for beam steering and input–output isolation. Here we show that leaky-wave coherence tomography, which can integrate a terahertz radar system using a pair of reverse-connected leaky-wave antennas, can be used to implement beam steering and homodyne detection in one package. Our approach can detect direction and range without using phase shifters, circulators, half-mirrors, lenses or mechanical scanners, providing a compact, penetrating and high-resolution radar system suitable for mobile devices and drones. To illustrate the capabilities of the technique, we use it to create a remote heartbeat detector that can measure the chest displacement of a person through their clothes. A pair of leaky-wave antennas can be used to make a compact, integrated terahertz radar detection system without phase shifters or circulators.

Integrated terahertz radar based on leaky-wave coherence tomography

Ultrawideband elliptical microstrip antenna for terahertz applications

Terahertz technology is a hotspot in the current academic research. In this study, a 400 GHz broadband multi-branch waveguide hybrid coupler is designed, but it is very difficult to fabricate. In order to release the processing difficulty, a modified five-branch hybrid coupler has also been designed, fabricated and measured. The hybrid coupler consists of five modified branches and has been optimised to a great performance, which increases the operation bandwidth. Compared to the traditional five-branch hybrid coupler design, this structure has a wider operation bandwidth and the bandwidth is almost the same as traditional seven-branch hybrid coupler. Based on this model, the performance of the coupler is optimised by HFSS software. The measurement results show good performance that >18 dB return loss (S
 11
) and isolation (S
 23
), 90° ± 2° phase difference and 0.3 dB amplitude imbalance are obtained in the frequency range of 380-460 GHz, agreeing well with the simulation results.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-map.2020.0090

Four‐hundred gigahertz broadband multi‐branch waveguide coupler

Corrugated horns are the feed of choice at millimeter and submillimeter wavelengths for quasi-optical systems in applications, which require high beam quality and low cross polarization over wide bandwidths, such as radio astronomy. However, this kind of feeds is difficult to manufacture at terahertz frequencies due to technological limits. Using the heritage established during Atacama Large Millimeter/Submillimeter Array band 10 (0.79–0.95 THz) production, some prototype corrugated horns for the 1.25–1.57 THz band have been designed and fabricated by direct machining. Two different kinds of corrugated horns with similar performance have been considered: long conical-profile corrugated horns and shorter profiled corrugated horns. A new modeling method has been proposed to obtain the quasi-optical parameters of the resulting horns and realize frequency independent quasi-optical designs. Patterns of the fabricated corrugated horns have been measured and results agree well with simulations. To the best of our knowledge, this is the first time corrugated horns have been successfully fabricated by direct machining for use up to 1.57 THz.

Terahertz Corrugated Horns (1.25${\hbox{--}}$ 1.57 THz): Design, Gaussian Modeling, and Measurements

Development of local oscillator (LO) sources based on amplifier multiplier chains (AMC) have steadily progressed in recent years, with more power and more bandwidth available at mm and sub-mm wavelengths. Recent radio astronomy receiver projects are, however, aiming at duplicating the RF bandwidth, with fractional bandwidth around 60%, even at frequencies as high as 500 GHz. In particular, National Astronomical Observatory of Japan (NAOJ) is developing wideband SIS mixers for a combined Atacama Large Millimeter/Submillimeter Array (ALMA) band 7 and 8 receiver, extending from 275 to 500 GHz. Currently, LO sources are not available for such a wide frequency band. To solve this problem, we have developed a waveguide diplexer to combine the output power of two different LO sources for ALMA band 7 (275-373 GHz) and band 8 (385-500 GHz). The proposed waveguide diplexer is based on hybrid couplers and waveguide filters. Two units of the designed component have been fabricated and S-parameters have been measured with good agreement with simulations. Initial tests to combine the LO power of band 7 and 8, LO sources at cryogenic temperature to pump a wideband 275-500 GHz SIS mixer have been successful.

275–500 GHz Waveguide Diplexer to Combine Local Oscillators for Different Frequency Bands

This paper describes a waveguide hybrid-coupled multiplexer for frequencies around 400 GHz. The designed multiplexer has three bands with 25-GHz bandwidth and no frequency gap between channels. The multiplexer is composed of two identical waveguide branch-line quadrature hybrid couplers and two identical bandpass filters based on waveguide inductive iris windows. In order to find the critical element of the multiplexer, network analysis was carried out using signal flow graphs. The multiplexer was fabricated based on direct machining technology with machining accuracy in the order of a few microns. S -parameters measured with a vector network analyzer show excellent agreement with simulations.

Design and Development of a Hybrid-Coupled Waveguide Multiplexer for a Multiband Receiver

ALMA Band 10 tertiary optics

We report on a 275–500 GHz heterodyne receiver system in combination with a wideband intermediate-frequency (IF) backend to realize 17 GHz instantaneous bandwidth. The receiver frontend implements a heterodyne mixer module that integrates a superconductor-insulator-superconductor (SIS) mixer chip and a cryogenic low-noise preamplifier. The SIS mixer is developed based on high-current-density junction technologies to achieve a wideband radio frequency (RF) and IF bandwidth. The IF backend comprises an IF chain divided into two channels for 4.0–11.5 GHz and 11.3–21.0 GHz and an analog-to-digital converter (ADC) module that is capable of high-speed sampling at 32 Giga samples per second with 12.5 GHz bandwidth per channel and an effective number of bits of 6.5. The IF backend allows us to simultaneously cover the full 4–21 GHz IF range of the receiver frontend. The measured noise temperature of the receiver frontend was below three times the quantum noise (hf /k B ) over the entire RF band. A dual-polarization sideband-separating receiver based on this technique could provide up to 64 GHz of instantaneous bandwidth, which demonstrates the possibility of future wideband radio astronomical observations with advanced submillimeter-wave heterodyne receivers.

/pdf/demonstration-of-a-wideband-submillimeter-wave-low-noise-2gegd3z2he.pdf

Alvaro Gonzalez

Papers

Terahertz Corrugated Horns (1.25${\hbox{--}}$ 1.57 THz): Design, Gaussian Modeling, and Measurements

275–500 GHz Waveguide Diplexer to Combine Local Oscillators for Different Frequency Bands

Design and Development of a Hybrid-Coupled Waveguide Multiplexer for a Multiband Receiver

ALMA Band 10 tertiary optics

Demonstration of a wideband submillimeter-wave low-noise receiver with 4-21 GHz IF output digitized by a high-speed 32 GSps ADC