ABSTRACT. We report on ongoing technology development activities in the build and testing of a refractive telescope composed of metamaterial Gradient Index (GrIn) lenses based on
photolithographic meshes. This concept is tailored for Earth
Observation, and more precisely limb-scanning in the sub-THz
bands addressing emission lines between 50 and 190 GHz.
A single GrIn lens design which includes in-built anti-reflection
coating layers, allows us to produce sufficient refraction to allow
a optical design of a set of compound lenses to create the first
THz range telescope fully composed of metamaterials.
First lens prototypes have been built and tested spectrally
and spatially and compared to analytical models showing good
agreement. Prediction of telescope performance is discussed as
well as future developments.

ABSTRACT. This paper reports on the design of a WR5 band (140–220 GHz) waveguide bandpass filter based on four oversized spherical resonators operating at TM211 mode. Compared to the fundamental mode TM101, the spherical cavities based on TM211 mode offer appealing advantages including a higher unloaded quality factors (Qu) and a larger size. The filter is designed for 3-D printing technique, and a larger size facilitates the fabrication process and allows larger tolerances in the printing process. The filter is designed to have a generalized Chebyshev response with a centre frequency of 209 GHz, a fractional bandwidth of 4.3% and a passband return loss of 20 dB. An extracted pole resonator is introduced to produce a transmission zero at 215 GHz, for improved rejection at the upper stopband. Simulation results of the filter show good performance, demonstrating that the proposed design could find useful application in the 3-D printed millimetre-wave waveguide filters.

ABSTRACT. Designing a metasurface structure on demand is an extremely time-consuming process. As an efficient machine learning method, deep learning has been widely used for data classification and regression in recent years and in fact shown good generalization performance. We have built a deep neural network for ondemand design of a terahertz (THz) metasuface with split ring resonator. With the required reflectance as input, the parameters of the structure are automatically calculated and then output to achieve the purpose of designing on demand. The results indicate that using deep learning to train the data, the trained model can more accurately guide the design of the structure, thereby speeding up the design process. Compared with the traditional design process, using deep learning to guide the design of metasurface can achieve faster, more accurate, and more convenient purposes.

ABSTRACT. Indoor wireless communications need to move towards Terahertz (THz) frequencies in order to keep up with society’s demand for data transmission, but this change is currently hindered by limited knowledge of material properties and propagation and scattering models at these frequencies. The dielectric properties of common household materials are investigated here with a twofold objective: (1) to extend the library of material properties at THz, and (2) to estimate and disentangle losses in scattering measurements in order to facilitate propagation, scattering and, ultimately, channel models.

ABSTRACT. A wideband dual-polarized filtering antenna is presented in this paper for base station applications. This antenna is composed of the center driven crossed-dipoles and four parasitic stepped split-loop. It is investigated that the center dipole arm can introduce the first radiation null at the lower band-edge, and the width of the stepped split-loop can affect the second radiation null at the upper band-edge. Therefore, by controlling these two parameters, a wideband dual-polarized antenna with quasi-elliptic filtering response can be realized. Finally, this antenna was designed, fabricated, and measured for performance verification. The measured results prove that the presented antenna can have a wide impedance bandwidth covering 1.7-2.9 GHz, and high suppressions of 33.8 dB and 20.6 dB over 0.6-1 GHz and 3.3-5 GHz.

ABSTRACT. In this paper, a rectangular dielectric resonator antenna (RDRA) based on substrate integrated suspended line platform (SISL) is proposed for millimeter-wave applications. The dielectric resonator is embedded in the air cavity and fixed by the substrate 3. The cone feed line of the RDRA is presented in this design to excite the {\mathrm{TE}}_{\mathrm{1\delta1}}^\mathrm{x} radiation mode. By using the SISL structure, the loss is reduced and a high gain is realized. Compared to the traditional DRA fed by microstrip line and coupling slot, the proposed design presents merits of low substrate lost, self-packaging and high efficiency. Simulated results show that the proposed RDRA obtained 10 dB impedance bandwidth of 11.41 % from 24.95 to 27.97 GHz. At 26.03 GHz, the simulated gain is 6.58 dBi.

ABSTRACT. In this paper, a lightweight circularly-polarized waveguide slot antenna array with high efficiency and low axial ratio is demonstrated. The proposed antenna contains a rectangular feeding waveguide, which connects to a radiation cavity through coupling slots. Owing to the unique feed structure, an equal amplitude but opposite phase excitation is generated between adjacent coupling slots, making the metal walls in the rectangular radiation cavity unnecessary. Moreover, a metasurface-based polarization convert chamber is loaded onto the radiation cavity, resulting in an excellent circularly-polarized radiation. The proposed antenna works in K band (center frequency is 21 GHz) with the impedance bandwidth as well as the axial ratio bandwidth is 5.2% and 7%, respectively. In addition, the design of the proposed antenna has a remarkable effect on reducing the weight, showing a great potential for satellite communications.

ABSTRACT. Abstract—A novel method of achieving multi-band shared-aperture antenna with a flexible frequency ratio, high antenna efficiency and excellent cross polarization level is presented. A parallel-plate waveguide (PPW) duplexer is used to feed a broadband continuous transverse stub (CTS) radiator over multiple bands. The duplexer is implemented using a parallel-plate waveguide low pass filter and a shorted stub to suppress the low frequency band. The presented method not only significantly enhances the bandwidths of the antenna but also results in a flexible frequency ratio, reduced loss and high gain. Based on this method, a tri-band shared-aperture CTS array antenna is implemented for Ku/K/Ka-band satellite communications. The simulated results show a wide impedance bandwidth of 22%, 10% and 7%, respectively. The array also exhibits a high antenna efficiency of over 80% and excellent cross-polarisation discrimination of over 66 dB.

ABSTRACT. Dispersion diagram of uniform 20-periods highly overmoded, with average diameter to 75 GHz operating wavelength ratio ≈ 8, slow-wave structure (SWS) designed to operate in E-band frequency range is numerically calculated with SuperFish code. It is shown as a result of calculations that while the lower-order TM01 mode of the SWS is slowed down by the corrugated structure of the E-band SWS, the higher-order TM0n modes are not slowed down.

ABSTRACT. The generation of an electron beam and its interaction with RF wave is a decisive factor for gyrotron operation in the desired mode. Excitation of the desired mode primarily depends upon beam radius in addition to beam current. Therefore, a design investigation of the double beam electron optics system (DB-EOS) is presented here, along with the mode competition study. The radial spread of the dual-beam magnetron injected gun is calculated to avoid the parasitic mode excitation and ensure the isolation between the inner and outer beams. Furthermore, this study is extended to investigate the velocity spread variation over emitter roughness and cathode temperature. This study finds that radial spread should be below 0.04 mm for the internal beam to avoid competition and TE-85 mode is severely competing with operating TE21,4 and TE-15,6 mode for external beam.

ABSTRACT. We have designed a dual-band backward wave oscillator (BWO) using a double staggered grating (DSG) slow-wave structure (SWS) and a pseudospark-sourced sheet electron beam. In the simulation of the high-frequency characteristics, the DSG SWS has been shown a wide operating band of 72-125 GHz and a high coupling impedance. The complete structure of the BWO consists of 10 DSG SWS units, together with a wideband output structure. In the cold-test simulation of the DSG BWO, the transmission is greater than -7 dB in the band 74-100 GHz, and 109-125 GHz. The hot-test performance of the DSG BWO is analysed by particle-in-cell (PIC) simulation, showing dual-band operation in 75-100 GHz (25-GHz bandwidth) and 108-115 GHz (7-GHz bandwidth), with high output power (max. 162 kW).

ABSTRACT. In this paper, a gyroklystorn operating at 36 GHz was designed to drive a harmonic linearizer for the CompactLight X-ray Free electron laser. Linear theory, non-linear theory and Particle-In-Cell simulations were used to design a three cavity 36 GHz gyro-klystron of gain 39 dB that is capable of producing 3.2 MW of power corresponding to an efficiency of 43% at a pulse repetition frequency of 1 kHz. Analysis of the phase stability of the amplifier found that 0.34º phase stability can be achieved for a variation in modulator voltage of 0.01%. When driven by a K100 (150kV, 50A) Scandinova modulator, the 36GHz gyro-klystron was a viable power source for a 6th harmonic linearizer.

ABSTRACT. This paper presents a broadband feed network for dual-fed circularly polarized antenna. The feed network is composed of broadband 90°phase shifter and a Wilkson power splitter. The impedance bandwidth (VSWR 2) is from 2.5 to 4.5 GHz (about 57%), with the 3 dB axial ratio bandwidth from 2.9 to 4.1 GHz, and the maximum gain are 7.0 dB at the center frequency. The simulated results in the 1×2 array shows that the mutual coupling deteriorates the axial ratio from 1.03 dB to 4.37 dB.

ABSTRACT. A novel slow-wave structure(SWS) named domical trapezia double staggered grating waveguide(DTDSGW) has been used to design a 0.22THz travelling wave tube. The slow-wave characteristics of the novel SWS, including dispersion properties and interaction impedance, are analyzed by using the 3-D electromagnetic simulation software. The particle-in-cell (PIC) simulation results reveal that, with the cylindrical electron beam of 18.3 kV and 100 mA, the output power and electron efficiency of the DTDSGW TWT at the typical frequency of 0.22 THz can reach 91 W and 4.97%, respectively. In addition, the 3-dB bandwidth of the DTDSGW TWT exceeds 15 GHz.

ABSTRACT. In this paper, the author introduces a physical method of shaped reflector synthesis technology based on NURBS. By comparing with different shaped reflector technologies, the author tries to convince us the usability and superiority of NURBS. At last, the author shows the application of this method in CATR system.

ABSTRACT. In this paper, an application of Gaussian mode analysis method is discussed. The mode synthesis method is used to realize the synthesis of specified pattern. Taking the ideal radiation function of the feed with the compact field of the biased single mirror as an example, an approximate radiation function is synthesized by using the Gaussian modes of different orders. The difference between the ideal radiation pattern and the synthetic pattern in the central region is less than ±0.2dB. The method is a fast and efficient quasi optical system design technology.

ABSTRACT. This paper presents a Ka-band rectenna which contains a double-port antenna connected with two rectifiers for wireless power transfer. The horn antenna is formed by two stacked apertures to minimize the antenna height. The horn antenna is connected to 1-to-2 power divider to form a double-port antenna. The power divider would be connected to the two same efficient rectifiers. With this rectenna topology, the power handling capability would be enhanced by 2 times. At 34.5 GHz, the designed antenna has a realized gain of 11.1 dBi, the designed power divider has insertion loss of 3.07 dB, and the rectifier has a PCE of 50% when the load is 300 Ω and the input power is 22 dBm. It can be predicted that the rectenna can handle at least 25 dBm input power.

ABSTRACT. In this paper, a 220GHz discontinuous manifold coupled waveguide diplexer is proposed for future terahertz multichannel communication applications .The diplexer consists of two Chebyshev bandpass filters based on metal waveguide technology .Through the co-design of the low order electromagnetic distribution model and the full wave electromagnetic model, the optimization design with high computational efficiency and high design precision is realized .The multiplexer is manufactured using low-cost CNC milling technology, with an in-band insertion loss of 0.8dB per channel filter and an average common-port return loss of 15dB.The measured results are in good agreement with the simulation results, which verifies the correctness of the whole design process.

ABSTRACT. A millimeter-wave triple-band antenna with high isolation for the fifth generation mobile communication network (5G) is proposed. The antenna uses liquid crystal polymer (LCP) as the underlying dielectric substrate and is composed of two hexagonal radiating patches. The thickness is 0.1mm and the antenna size is 47.7mmx20.5mm. The -10dB bandwidth of the simulated S11 of this antenna is 6.22GHz (3.01-9.23GHz), 2.4GHz (26.78-29.18GHz)and 4.03GHz (34.97-39.00GHz),covering sub-6 and millimeter wave bands. The simulated -20dB bandwidths for S21 are covered the entire frequency band.

ABSTRACT. In this paper, a millimeter wave bandpass filter based on substrate integrated waveguide (SIW) is proposed. The filter is loaded with two kinds of defected ground structures (DGS) called complimentary spilt ring resonator (CSRR) and dumbbell-shaped. This mix-loading method not only combines these two DGSs’ advantages, but also increases the flexibility of adjustment. Through analyzing the laws of how the different DGS arrangements will affect the filter’s performance, it can be noticed that upper-band suppression is significantly improved. Meanwhile, an algorithm is studied to speed the design process considering that the SIW and DGS structures’ simulation is time-consuming. The HFSS simulation result shows that the stop-band suppression is greater than 46dB, and the in-band return loss is over 15dB. The transition of upper-band is steep and the width of 25dB suppression is around 7GHz.

ABSTRACT. A slow-wave structure (SWS) with periodic coupling structure and reentrant cavity is proposed for extending the extended interaction klystron (EIK) technology. The conventional higher-order mode single-period cavities allow for larger sizes, corresponding to the G-band (220 GHz), but their low R/Q values are not facilitating the realization of extended interaction klystron (EIK). The newly proposed compact EIK topology is to support millimeter-wave higher-order mode operations. The slow wave structure facilitates the advantages of multi-layered processing.

ABSTRACT. The simulation and design of an oversized, two-dimensional, periodic surface lattice (2D PSL) interaction cavity used within a 0.395 THz, pulsed radiation source is presented. Powerful, pulsed radiation with good spectral purity is demonstrated. The device is well-suited for use in DNP-NMR spectroscopy and has numerous other applications due to the scalability of the interaction cavity allowing for radiation output at different frequencies. The device exploits the coupling of volume and surface fields in the 2D PSL interaction cavity to excite a single cavity eigenmode. The observed output power is 13.5kW and the efficiency of the device is 27%

ABSTRACT. This paper presents a dual-circular-polarization (dual-CP) antenna based on a grooved-wall horn antenna working in the W-band, which shows high port isolation over a wide bandwidth. The grooved-wall horn antenna has a pair of grooves on its wall to serve as an inbuilt polarizer. By connecting the grooved-wall horn to an orthomode transducer (OMT) in such a way that the pair of grooves is aligned at ±45° with respect to the horizontal and vertical polarization of the OMT, left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) can be generated, thereby realizing a dual-CP antenna. High isolation is also achieved due to the low reflection coefficient of the horn and high isolation of the OMT. The simulated results show the proposed dual-CP antenna achieves port isolation > 30 dB over 27.4% bandwidth from 82 to 108 GHz with axial ratio (AR) < 3 dB and |S11| < -15 dB.

ABSTRACT. A high performance terahertz tri-reflector compact antenna test range (CATR) with ultra-large aperture is presented in this paper. The tri-reflector CATR system is composed of a parabolic main reflector and two shaped sub-reflectors. The aperture size of the main reflector is 7 m, while the size of the two sub-reflectors are about 0.55 m * 0.55 m and 0.44 m * 0.44 m respectively. By using B-spline surface reconstruction and dynamic ray-tracing approach, two shaped sub-reflectors are synthesized. The tri-reflector CATR which can generate a regional pseudo-plane wave in a very short distance, is commonly employed to measure electrically large aperture antennas, and this region is generally referred to as a quiet zone (QZ). The designed tri-reflector CATR system is modeled and simulated. The numerical analysis and simulation results demonstrate that a peak-to-peak amplitude (phase) ripple <1 dB (5°) and a cross-polarization isolation >50 dB can be achieved on the principal cuts of the QZ at 100–500 GHz, and furthermore, the QZ usage ratio of the CATR can reach up to 80%. All these show that the tri-reflector CATR system has a high QZ performance, and the effectiveness of the system design has also been verified.

ABSTRACT. This paper presents a broadband millimeter-wave (mm-wave) power amplifier (PA) in 45-nm SOI Technology. Based on the principle of magnetically-coupled resonance (MCR), an asymmetric magnetically-coupled resonator is implemented using a transformer-based structure, which effectively compensates the high-frequency gain of PA, and improves the gain flatness and bandwidth of PA. According to the simulation results, the 3-dB bandwidth of the PA is 11 GHz from 26 to 37 GHz. Besides, the PA achieves gain of 22.7 dB, PSAT of 20.8 dBm, and peak PAE of 34.3%.

ABSTRACT. In this paper, a sheet-beam extended interaction oscillator that can work in the THz frequency band is designed. The working center frequency is 0.104THz, and the working mode is TM11 mode. The EIO can be used for high-power operation. The simulation results show that when the voltage is 43.2kV, the current is 2.4A, under a 0.5T magnetic field, and under a certain surface loss, its output power can reach 2.3kW. This research provides guidance for the study of sheet-beam EIO operating at high frequency and high power.

ABSTRACT. A novel mode composite transmission line (MC-TL) is proposed. The MC-TL integrates spoof surface plasmon polaritons (SSPPs) into half mode corrugated substrate integrated waveguide (CSIW) to realize surface plasmon mode propagated on the corrugated metal surface and TE0.5,0 transmitted in the substrate at the same time. With the dual mode operation, the dual band can also be obtained. For verification, the propose MC-TL based on SSPPs and HMCSIW is fabricated, and good agreement between the measured and simulated results demonstrates the validity of proposed configurations.

ABSTRACT. Because the liquid crystal material has fluidity and electrical control characteristics, it is suitable for conformal phased array design, so this paper designs a cylindrical conformal phased array antenna based on liquid crystal material. The designed conformal phased array antenna has a center frequency of 15GHz, a 5×5 uniform array, and a cylindrical radius of 80mm, which can achieve gradient gain scanning (14.17dB-21.4dB), and the scanning range is ±30°. The designed antenna array has certain practical prospects.

ABSTRACT. The design of wideband slow wave structures (SWS) for millimeter wave travelling wave tubes can be aided by the implementation of gap waveguide technology. Contactless metal walls can alleviate assembly challenges at frequencies above 70 GHz and potentially reduce ohmic losses. The increased design flexibility typical of this technology can lead to the integration of different functionalities into a monolithic design at the power coupling section. A W-band gap waveguide-based SWS is proposed for wideband travelling wave tube operation at the frequency range 88-100 GHz. Preliminary results of the complete SWS are presented.

ABSTRACT. This paper presents the preliminary analysis of a folded waveguide (FWG) slow wave structure (SWS) for 160GHz traveling wave-tube amplifier. Traveling wave-tube amplifiers operational in the D band of the millimeter wave frequencies are the apt candidates for their application in the point-to-point backhaul communication of 5G and above networks, and in the inter-satellite communication in space. The dispersion analysis of the unit cell of the FWG SWS presented in this paper effectively describes the dependence of the critical design parameters, namely the operational frequency range, bandwidth, and phase velocity on the dimensional variables. An operational bandwidth of 20GHz ranging from 155GHz-175GHz has been successfully obtained with a RF phase velocity of 0.3 times velocity of light in this paper.

ABSTRACT. We demonstrate an electrically triggered tunable terahertz (THz) modulator based on vanadium dioxide (VO2) embedded hybrid metasurface. The unit cell of the filter consists of two plates butted together with a split gap and a central bar. The phase transition of VO2 is induced by the ohmic heating of the central bar. The transmission can be modulated by the temperature caused by the ohmic heating. The mechanism of tunability is that the conductivity of the VO2 film changes with the applied currents. The relation between the modulation frequency and the geometries is investigated using finite element method (FEM). The simulation results show that, when the temperature of the VO2 film increases from 65 to 70 ℃, a redshift from 0.65 THz with a 99% modulation depth to 0.3 THz with a 94% modulation depth is obtained. This tunable THz modulator has potential applications in THz communication, imaging, and spectroscopy systems.

ABSTRACT. This work reports on the design and analysis of a folded antenna operating at mm-wave frequencies. Prior to this, several folded antennas operating at 7, 9 and 10GHz frequencies were used to validate the simulation procedure performed. A mm-wave folded antenna with a resonant frequency of 39GHz was then simulated. A relatively small antenna geometry was achieved without sacrificing its gain and other crucial characteristics. A 3.5dB gain and 4.6dBi directivity were obtained with a frequency bandwidth reaching 780MHz. The main and secondary arm widths of the folded antenna are key in determining the real and imaginary parts of the antenna impedance, providing a degree of freedom for the designer to get the antenna well-matched with the subsequent integrated circuit. This provides useful features including the capability of reducing the overall antenna dimensions and avoiding matching circuits.

ABSTRACT. In this paper, the modified quasilinear model of a gyrotron injection locking by an external signal is presented and theoretical study of the scenarios for the transition to the synchronization mode is carried out. We considered the situation when the gyrotron is in the hard excitation mode, since in that case maximum interaction efficiency is provided. Using the developed model, we derive the stability conditions of the synchronization modes and discuss the possibility of reaching maximal interaction efficiency in the mode of synchronization.

ABSTRACT. A broadband circularly polarized (CP) metasurface antenna based on double pentagonal elements is proposed. The antenna is composed of a microstrip coupling feeding I-shaped slot, metasurface and the air layer between them. The I-shaped slot generates linearly polarized (LP) waves, and the metasurface completes the conversion from LP waves to CP waves. The simulated results show that the impedance bandwidth of the antenna is 6.89GHz – 8.92GHz, and the 3dB axial ratio bandwidth is 7.21GHz – 8.50GHz. It has potential applications in wireless communication systems for simple structure and 3dB axial ratio bandwidth.

ABSTRACT. In this paper, a terahertz phase shifter work in F-band (90-140 GHz) is designed based on the continuous tunability of liquid crystal and the excellent electrical properties of non radiative dielectric (NRD) waveguide. The simulation results show that the liquid crystal phase shifter is electrically controlled by the bias electrode network, and the maximum phase shift is 500 degrees. The phase shifter shows excellentl matching, and the return loss is almost less than -10 dB in the bandwidth up to 60 GHz.

ABSTRACT. A planar reflectarray antenna based on liquid crystal materials is presented in this paper. First, a new type of loop dipole miniaturized liquid crystal antenna reflection unit is constructed. The reflector unit can achieve 400° phase shift at 35GHz, and the loss is less than 4.5dB. Then, an 11×11 liquid crystal reflectarray antenna is designed using this unit, and the main beam scanning angle range of the array antenna reached ±20°. When the deflection angle of the array antenna is 20°, the gain of the antenna is 14.9dBi, and the first sidelobe level is -9.1dB.

ABSTRACT. In this paper, a dual-frequency dual-beam antenna loaded with metasurface is proposed. Firstly, the feeding unit composed of two printed dipole antenna is used to provide excitation. And then, by loading the metasurface consisted of periodically arranged square rings, two beams steered to different directions are realized and two wider working frequency bands are obtained. At the same time, the beam gains are improved. The results show that the resonant frequencies of the antenna are at 57 GHz and 66 GHz, and the corresponding maximum radiation beam pointing at (φ, θ) = (164°, 90°), (196°, 90°) and (φ, θ) = (158°, 90°), (202°, 90°), respectively. Also the gain can reach to 8.2 dBi.

ABSTRACT. A high gain differential-feed stacked-patch antenna based on substrate integrated suspended line (SISL) is proposed in this paper. The antenna consists of five substrate layers with two internal air cavities. By etching slots on the driven patch and adding the stacked patch, the simulation results of the antenna can cover the operating band of 26.22-30.14 GHz. The realized gain of the operation band is within 10.76-12.52 dBi. The cross-polarization is less than -45dBi. And the radiation efficiency is higher than 82 %.

ABSTRACT. In the traditional terahertz spatial modulator, the scale of the metamaterial must be equivalent to the area of the terahertz spot in free space to obtain effective terahertz modulation. Large-scale artificial microstructure arrays increase the complexity of metamaterial circuits, which leads to problems such as mode parasitic and impedance mismatches inside the metamaterial. In order to effectively reduce the scale of the metamaterial array, so as to manipulate the terahertz wave more efficiently, in this paper, we propose a technical scheme for loading the spatial modulator with waveguide. By regulating the carrier concentration of 2DEG in metamaterial chip, the efficient control of metamaterial mode to waveguide mode has been realized. Static modulation depth of this device can reach up to 13.5dB. More importantly, in the dynamic test, 8 GHz sinusoidal signals was received by a THz mixer receiver. It may provide a way to achieve high-performance active devices in THz wireless communication system.