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This letter presents our study on a millimeter wave (mm-wave) orthomode transducer (OMT) based on novel double-ridged waveguide junction. By reducing the length of ridges in the square waveguide, the ridge width of proposed junction is about three times wider than that of conventional junction. This benefits the fabrication and mechanical performance of double-ridged waveguide OMT in the higher mm-waveband or terahertz band. The simulated reflection coefficients for both orthogonal modes are less than -20 dB over 37% bandwidth. As practical application, an E-band OMT based on the novel junction is fabricated. A smooth-horn is integrated with the OMT as a dual-polarized antenna. The measured results show that reflection coefficients less than -15 dB, isolation better than 39 dB, and cross-polarization discrimination (XPD) higher than 23 dB are achieved from 71 to 86 GHz.

This letter presents our study on a compact and low-loss E-band bandpass filter (BPF) based on multilayer groove gap waveguide (GGW). Different from other reported planar GGW filters and vertically stacked substrate integrated waveguide (SIW) filters, the proposed filter realizes a cross-coupled quadruplet topology by introducing a pair of unique circular capacitive holes across layers, innovative ridges (capacitive iris), and conventional inductive irises on the same layer, which reduces the insertion loss (IL) while having a smaller size. By tuning the dimensions of the coupling structures and cavities, the filter is optimized to exhibit a superior performance in simulation. The designed filter is fabricated using CNC machining and verified in experiment. The measured results agree with the simulated ones quite well, showing an average IL of 0.45 dB and an 8% relative 3-dB bandwidth at a center frequency of 73.65 GHz. Therefore, the proposed multilayer GGW structure opens a new avenue in designing high-performance filters in millimeter-wave bands.

A novel millimeter-wave (mm-wave) wideband circularly polarized (CP) horn antenna using iris polarizer is reported. By introducing the metasurface concept, the electrical contact problem at the mm-wave band for waveguide-separated components of high-performance CP horn antenna is eliminated. The influence of air gaps on polarizer and whole horn antenna loaded and unloaded metasurface is analyzed and explained. According to simulation, small air gaps of the metal-to-metal contacting plane would not harm the horn performance after loading the metasurface, which means the proposed method can achieve a better tolerance of manufacturing and assembly errors and is more suitable for high-frequency CP horn design. For validation, the proposed horn antenna has been fabricated and its performance is evaluated. The measurement results are in good agreement with the simulation results. The experimental results of 37.8% bandwidth from 75 to 110 GHz for both the axial ratio (AR) $\vert S_{11}\vert dB are achieved.

In this letter, a high-efficiency multibeam circularly polarized (CP) antenna array with the groove gap waveguide (GGW) feeding technology for W-band application is proposed. First, a wideband CP septum antenna element based on GGW structure is proposed. The antenna has a simple structure with high tolerance, and the GGW technology reduces the machine difficulty, making the antenna easier to work in the higher frequency. Next, a 4 × 4 GGW Butler matrix is designed to feed the antenna array. Finally, a high-efficiency W-band four-beam CP endfire antenna array is fabricated and measured. Measured results verify that the antenna has a wider impedance bandwidth of 17.6% from 77.5 to 92.5 GHz for | S 11| < −10 dB. The measured AR values of the main lobe range of four beams are almost less than 3 dB. Also, stable radiation patterns are obtained. The maximum gain and radiation efficiency are 15.29 dBic and 89.6%, respectively.

A millimeter-wave (mm-Wave) wideband dual circularly polarized (CP) antipodal septum antenna is proposed. By introducing two antipodal septum blames in widened rectangular waveguide and the corresponding feeding network, the operating bandwidth of the septum antenna is enhanced. The working principle of the generation process of dual CP is explained by a three-port model with three excitation conditions. In addition, the asymmetrical radiation pattern of the classical polarizer consisting of square waveguide and single septum caused by the high-order modes is explained and eliminated. To verify the design, the proposed antenna has been fabricated and measured. An operating bandwidth of 37.4% for reflection coefficients less than −13.8 dB, isolation better than 22 dB, and axial ratio (AR) value less than 3 dB is achieved.

In this paper, a new approach to design terahertz (THz) E-plane crossover coupler is reported. By cascading two symmetrical septum polarizers, a simple structure with wide operating bandwidth and high isolation performance is achieved. The working principle is explained by operating waveguide modes. To simplify the optimization process, the scattering matrix (S-matrix) of the crossover is calculated. Two prototypes loaded and unloaded electromagnetic band gap (EBG) are fabricated and measured. The electrical contact problem at assembly plane is eliminated by the prototype loaded EBG. A measured bandwidth of 17.3% from 92.5 to 110 GHz for reflection and isolation coefficients −2 dB is achieved.

A millimeter-wave (mmW) wideband circularly polarized (CP) antenna based on an air-filled waveguide is proposed. By introducing two symmetrical ridges in the septum antenna, the proposed antenna can obtain a more compact antenna aperture than the septum antenna based on a rectangular waveguide (from 0.99 $\lambda \,\,\times1.25\,\,\lambda $ to 0.66 $\lambda \,\,\times0.91\,\,\lambda $ ). In addition, the high order modes are suppressed to less than −20 dB from 55 to 70 GHz. Then, the sharp corner in the axial-ratio (AR) and gain plots of the septum antenna based on a waveguide are eliminated. A simulated operating bandwidth of 16.4% for both $\vert \text {S}_{11}\vert dB and AR < 3 dB within half-power beamwidth (HPBW) is achieved from 56 to 66 GHz. To verify the design, the proposed antenna has been fabricated and measured. The differences between simulations and measurements caused by flange are evaluated. The measured operating bandwidth of 20.9% is achieved from 60 to 74 GHz

A type of millimeter-wave antenna array with flexible design is proposed for a variety of applications at 60 GHz. The antenna array can be adjusted to be linearly or circularly polarized by simply changing the radiation part of the antenna array. High gain, wideband, and high radiation efficiency characteristics can be achieved by adopting a low insertion loss feeding network and broadband antenna elements. For the linearly polarized antenna array, simulation results show that the impedance bandwidth of the 2×2 antenna subarray reaches 21.6%, while the maximum gain achieves 15.1 dBi and has a fluctuation of less than 0.4 dBi within the working bandwidth. Simulation results of the 8×8 linearly polarized antenna array show a bandwidth of 21.6% and a gain of (26.1±1) dBi with an antenna efficiency of more than 80%. For the 8×8 circularly polarized antenna array, simulation results show that an impedance bandwidth of 18.2% and an axial ratio (AR) bandwidth of 13.3% are obtained. Gain and efficiency of up to 27.6 dBi and 80% are achieved, respectively. A prototype of antenna array is fabricated, and results are compared and analyzed.

This paper presents a wideband dual-circular-polarization (dual-CP) antenna with high port isolation based on a grooved-wall CP horn combined with an orthomode transducer (OMT) in the W-band. A pair of grooves on the inner wall of the horn serves as an inbuilt polarizer within the horn antenna, which is capable of generating both left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) without any septum. The continuous linearly-tapered groove design also allows this multi-section grooved-wall CP horn to achieve low reflection coefficients over a wide bandwidth, thereby realizing wideband dual-CP with high port isolation when it is used together with a wideband OMT. A prototype of the proposed dual-CP antenna is designed in simulation and measured in an experiment. The simulated and measured results agree very well, showing that port isolation > 32.5 dB over 31.6% bandwidth from 80 GHz to 110 GHz is achieved with axial ratio (AR) < 2.8 dB and reflection coefficient < –20 dB for both LHCP and RHCP. Rotationally symmetric radiation patterns over the entire operating bandwidth are also observed with a measured gain of 19.6±2 dBic.

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 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.

A wideband, contactless, coplanar waveguide (CPW) to rectangular waveguide transition integrated with an $E$ -plane bend at a ${W}$ -band is proposed. The transition utilizes a four-step Chebyshev ridge waveguide impedance transformer and a $\lambda _{g}$ /4 matching stub over the quartz CPW to ensure the wider impedance matching and to maintain a good electrical contact, without any soldering or gluing. The novel transition has a simple structure and a low insertion loss. The back-to-back prototype is fabricated and measured, and the measured reflection coefficient remains better than −10-dB over the entire ${W}$ -band, while the insertion loss is on average 1.2 dB in the range of 80–109 GHz (31.5% bandwidth). Also, the design is fully scalable to any other frequency band of interest.

A broadband coplanar-to-rectangular waveguide transition using contactless electromagnetic bandgap (EBG) structure in the form of interdigital-pin bed of nails is introduced in this paper. The electromagnetic (EM) wave propagates from the CPW, and then radiates from the probe into the WR4. The rectangular patch is adopted as the probe to accomplish a broadband performance without an impedance transformer. The presented transition has 41.8% fractional bandwidth, which covers the whole WR4 band (170-260GHz). The insertion loss is less than 0.47dB. In addition, the interdigital-pin EBG structure is added to the machining splitter of the rectangular waveguide which is no need for strict electrical contact. The greatest advantage of the interdigital-pin lattice has a significant pin gap increase and is easy to fabricate for millimeter-wave (mm-Wave) applications.

A high efficient wideband circularly polarized (CP) endfire antenna with groove gap waveguide (GGW) technology for $W$ band applications is proposed. Two symmetrical septum blades filled in the widened rectangular waveguide is employed to achieve the circular polarization characteristics, and two ridges are added on the upper and lower metal plates to improve the polarization purity. The other two ridges in the endfire antenna is used to achieve a more compact antenna aperture. Simulated results verify a −10 dB impedance bandwidth over the whole $W$ band, and a wider 3-dB axial ratio (AR) bandwidth from 75 GHz to 100 GHz (28.6%). Also, an average gain of 8.8 dBic and almost 100% radiation efficiency between 75–100 GHz are obtained.

In this paper, the authors present a broadband transition from the standard WR-10 rectangular waveguide (RW) to a groove gap waveguide (GGW) in the W-band. The transition structure is based on electromagnetic band gap (EBG) technology where two EBG units are used, which are responsible for the transition and forming the transmission line. Metal pins in the E-plane together with the back surface of the transmission line create a forbidden band, which prevents power leakage between the connecting parts. Small air gaps will not harm the transition performance according to the simulation, which means it has a better tolerance of manufacturing and assembly errors and, thus, has advantages for mm-wave contactless connections. A back-to-back transition prototype was designed, fabricated and measured. The length of the GGW is 39.6 mm. The measured |S11| is better than &minus, 13 dB and the measured |S21| is better than &minus, 0.6 dB over 76.4&ndash, 109.1 GHz, covering a bandwidth of 35.3%.

In this paper, a circularly polarized (CP) antenna with a wide bandwidth operating in W-band is presented. The proposed antenna is the combination of semicircular parallel-plate and ridges to achieve low cross polarization, wide axial ratio & impedance bandwidth. The structure was excited by the inclined WR-10 to generate CP field from parallel-plate. The antenna was designed, and simulated by ANSYS HFSS. Simulation results reveal that the antenna achieves an operating bandwidth of 36.18% for both $\vert \mathrm{S}11\vert and $\text{AR} and average CP gain of 7.75 dBic.

This paper introduces a design of large aperture tri-reflector compact antenna test range (CATR) with spherical main-mirror which is working in the Terahertz range. The diameter of the main mirror is 2 m, and the dimensions of the two shaped sub mirrors are about 0.6 m and 0.7 m respectively. The dimensions of the two sub mirrors are far smaller than the aperture side length of the main mirror. According to the characteristics of geometric optics and frequency-independent, we use kinematic and dynamic ray tracing method to design two shaped sub-reflectors. The system of reflectors is configured in a Cassegrain-Gregorian arrangement. Through the above design method, the CATR can generate a regional pseudoplane wave, usually referred to as quiet zone (QZ), and we can get the expected output field distribution in the quiet zone. By numerical analysis and simulation verification, we can see that a peak-to-peak amplitude (phase) ripple 30 dB can be achieved on the principal cuts of the designed quiet zone at 100–300 GHz. At the same time, the QZ usage ratio of the CATR can reach 70%. The proposed tri-reflector CATR has a good quiet zone performance and high QZ usage ratio, so it can be used in large aperture antenna measurements.

Millimeter-wave communications has attracted intensive attention in the recent years. However, this technique suffers from high propagation loss, large rain attenuation and poor capability through wall, which limits its application for outdoor and indoor applications. To overcome these limitations, the surface-wave Goubau line is used for millimeter-wave communication. In this paper, a dielectric resonator antenna (DRA) is proposed to radiate the power transmitted from power line. A coaxial converter is designed to feed to the DRA with the surface-wave Goubau line. The simulation results show the wide impedance bandwidth over 55–65 GHz, omni-directional radiation pattern and high gain performance.

Cloud providers widely deploy FPGAs as application-specific accelerators for customer use. These providers seek to multiplex their FPGAs among customers via virtualization, thereby reducing running costs. Unfortunately, most virtualization support is confined to FPGAs that expose a restrictive, host-centric programming model in which accelerators cannot issue direct memory accesses (DMAs). The host-centric model incurs high runtime overhead for workloads that exhibit pointer chasing. Thus, FPGAs are beginning to support a shared-memory programming model in which accelerators can issue DMAs. However, virtualization support for shared-memory FPGAs is limited. This paper presents Optimus, the first hypervisor that supports scalable shared-memory FPGA virtualization. Optimus offers both spatial multiplexing and temporal multiplexing to provide efficient and flexible sharing of each accelerator on an FPGA. To share the FPGA-CPU interconnect at a high clock frequency, Optimus implements a multiplexer tree. To isolate each guest's address space, Optimus introduces the technique of page table slicing as a hardware-software co-design. To support preemptive temporal multiplexing, Optimus provides an accelerator preemption interface. We show that Optimus supports eight physical accelerators on a single FPGA and improves the aggregate throughput of twelve real-world benchmarks by 1.98x-7x.

A millimeter-wave wideband circularly polarized (CP) horn antenna with no requirement of an orthogonal mode transducer feeding is reported. The horn antenna has a simple structure, which consists of an antipodal curvedly tapered slot antenna and a circular waveguide. The CP principle of the horn is explained. A series of parametric studies was carried out to estimate the effect of key parameters, and the design procedure is also presented. The measured results are in reasonable agreement with the simulation results. The experimental results indicate that the proposed antenna can achieve a bandwidth of 40% (50–75 GHz) for both the axial ratio $S_{11} dB. The proposed antenna is easy to manufacture and is a good candidate for the low-cost wideband CP horn antenna.

A novel millimeter-wave (MMW) endfire wideband circularly polarized (CP) antenna with simple structure is reported. By introducing two symmetrical septum blades filled in the widened rectangular waveguide, the proposed antenna can obtain a 40% bandwidth for both axial ratio (AR) $S_{11} dB. The CP operating mechanism of the antenna has been explained, using a three-port structure. The parametric studies for all of the antenna parameters are carried out to estimate their influences on antenna performance. The sharp corner in the AR plot is also explained by mode analysis. Its influences on the radiation pattern, gain, and reflection coefficient at this frequency point are evaluated. The proposed antenna has been fabricated and measured. The simulation results are in good agreement with the measurement results. Furthermore, this antenna is an appropriate choice for designing a MMW high-efficiency wideband antenna array. An $8 \times 8$ array with 64 equal amplitude and phase wave ports in HFSS has been designed to evaluate the array performance, which shows that the array can achieve 40% operating bandwidth without considering the bandwidth of feeding network. The simulated aperture efficiency of the array is above 85.34% from 50 to 75 GHz.

A method to reduce one direction width of the circularly polarized antipodal curvedly tapered slot antenna, while maintaining the wide axial ratio (AR) and impedance bandwidth and endfire radiation, is proposed in this letter. In this method, the ridge structure in the broad wall of the slotted waveguide is used to increase the current path, which makes the antenna achieving the appropriate phase difference of orthogonal electric fields within narrow antenna width. To validate the proposed method, a prototype of the antenna was fabricated and measured. Experimental results show that the proposed antenna can achieve a bandwidth of 27.6% (50–66 GHz) for both AR S 11

In this paper, a novel circularly polarized end-fire septum antenna based on substrateintegrated-waveguide (SIW) is proposed in the 60-GHz band. By introducing four symmetrical tapered curved air slots in three stacked open-ended SIW layers, the antenna can obtain an operating bandwidth from 57.2 to 63.4 GHz for both AR 11

In this paper, a millimeter-wave multi-folded frequency-dependent progressive phase shifter based on substrate-integrated-waveguide (SIW) is proposed. The equations based on SIW TE10 mode characteristic are applied to design the parameters of the phase shifter. An end-fire magneto-electric dipole with wide beam width is employed as the radiating element. By combining the antenna element and the phase shifter together, a frequency beam scanning antenna array is proposed and analyzed, using mathematical calculation based on phase array theory. A prototype of the proposed array has been fabricated and measured. The theoretical calculation of radiation pattern of the array is verified by full-wave electromagnetic solver Ansys HFSS and measurement. The measurement results show that the array can achieve a wide scanning range from -18° to 32°, gain variation less than 2.9 dBi, and radiation efficiency around 50% from 57 to 63 GHz. With the advantages of simple and compact structure, wide beam scanning range, and low-cost processing, the proposed array would be a good candidate for millimeter-wave wireless communication.

This paper presents and characterizes a novel high gain circularly polarized (CP) antenna array for 5G applications. The array element is an antipodal curvedly tapered slot antenna (ACTSA) generating circularly polarized field. The CP ACTSA fed by substrate integrated waveguide (SIW) is convenient to integrate with substrates. By introducing two sheet metals on the two sides of the rectangular Rogers 6002 substrate, an impedance bandwidth of 18.2%, a wide 3-dB axial ratio (AR) bandwidth of 16.9%, and stable gain of 8 ± 0.6 dBic over the operating band are achieved. By employing the proposed CP ACTSA as radiating elements, a 4 × 4 high-gain wideband antenna array is proposed for 5G $E$ -band and $W$ -band millimeter-wave applications. Fabrications are carried out using wire cutting electrical discharge machine and print circuit board process, which have advantages of low cost. The whole feeding network is realized by SIW with low insertion loss at millimeter-wave band. Benefiting from the wide impedance and AR bandwidth of the new antenna element, good impedance matching and AR characteristics can be achieved over the whole working frequency band from 81 to 95 GHz by this antenna array. Gain up to 18.5 ± 1.3 dBic is also obtained.

A low-cost wideband circularly polarized (CP) tapered slot antenna based on substrate-integrated waveguide (SIW) is presented for millimeter-wave applications. After using two linearly symmetrical slots on the two sides of the SIW, a bandwidth from 80.1 to 108 GHz for both axial ratio

In this paper, a linearly polarized millimeter-wave antenna array in 60 GHz band is proposed. By adopting high-efficiency feeding network and broadband antenna element, high gain, wideband, and high radiation efficiency are achieved. The simulation results show that the impedance bandwidth of the 2 × 2 antenna sub-array reaches 21.6%, the maximum gain achieves 15.1dBi and has a fluctuation less than 0.4 dBi within the working bandwidth. And the 8 × 8 antenna array designed shows a bandwidth of 21.6% and a gain of 26.2 dBi ± 1 dBi. The SLLs of three frequency points within the bandwidth are all less than - 13.4 dB. The overall radiation efficiency of the array is greater than 80%.

In this paper, a wideband end-fire circularly polarized (CP) antenna based on gap waveguide (GWG) is proposed for millimeter-wave (MMW) applications. The proposed CP antenna is composed of three layers of groove GWGs with two anti-symmetric triangular septum blades. The groove width is the same with WR-10, and the middle layer is used for feeding energy. The simulation results show that the antenna can achieve a 69.1% bandwidth for both axial ratio (AR)

The aperture field and radiation characteristics of the wideband circularly polarized (CP) antipodal curvedly tapered slot antenna (ACTSA) is proposed in this paper. The simulated radiation characteristics is in agreement with the measurement, the small simulated differences (less than 7.2°) of the half power beam width (HPBW) between x-z and y-z plane are achieved from 50 to 75 GHz and the measured one are less than 4° at 50, 69 and 75 GHz. The measured results show that the antenna can achieve a 40% bandwidth for both axial ratio (AR)

The authors propose the concept, analysis, and design of frequency tunable band-pass filters operating in the terahertz band. The proposed structure is composed of two metal tapped line and five metal-contacted graphene hairpin resonators transferred onto a dielectric. This structure implements low insertion loss and frequency tunability by adequately controlling DC bias applied on the graphene. An efficient synthesis method has been presented, through combining classical microwave filter theory and the electrical properties of graphene. The theoretical and extracted resonance frequency of resonator (f 0), external quality factor (Q E) and coupling coefficient (Kij ) are utilised to determine the filter circuit dimensions. Then the authors proposed two examples with different operating bandwidths to validate the theoretical design. The potentially high losses of graphene is also evaluated.

This paper presents and characterizes a novel antipodal linearly tapered slot antenna for generating the circularly polarized (CP) field. By introducing two symmetrical slots on the top and bottom layers of a rectangular WR-15 waveguide, we could obtain circular polarization with an axial ratio bandwidth of 34.1%. The waveguide was used to feed the proposed antenna with very wideband impedance matching. The antenna can achieve impedance bandwidth of 40% for S(1,1)

The Fast Fourier Transform is a fundamental tool in scientific and technical computation. The highly parallelizable nature of the algorithm makes it a suitable candidate for GPU acceleration. This paper focuses on exploiting the speedup due to using the half precision multiplication capability of the latest GPUs' tensor core hardware without significantly degrading the precision of the Fourier Transform result. We develop an algorithm that dynamically splits the input single precision dataset into two half precision sets at the lowest level, uses half precision multiplication, and recombines the result at a later step. This work paves the way for using tensor cores for high precision inputs.

The concept and analysis of a graphene-metal beam-reconfigurable terahertz (THz) loop antenna are presented. The hybrid graphene-metal implementation is proposed to combine (i) dynamic surface conductivity tunability using different DC bias voltages and (ii) high radiation efficiency enabled by metal. The loop antenna which employs an artificial mu-negative transmission line provides the horizontally polarised omnidirectional radiation. The graphene-metal loop around the centre ring acts as a reflector. Changing the DC bias of different position of graphene to control the position of resonance can effectively adjust the beam direction. The proposed concept and achieved performance, computed using realistic material parameters, are extremely promising for beam scanning at THz frequencies.

A wideband circularly polarized (CP) antipodal curvedly tapered slot antenna (ACTSA) based on waveguide is presented in this paper. By employing the ridge on the broadwall of the slotted waveguide, the antenna can obtain compact structure. The proposed antenna can achieve a bandwidth of 20.8% (56 GHz–69 GHz) for both axial ratio (AR) < 3 dB and reflection coefficient S(1,1) < −10 dB and a gain varies between 9.0 dBi and 10.3 dBi in simulation.

type="graphical" xml:id="gpol12169-abs-0001"> To perceive Chinese-Western countries’ relations in the developing world through a zero-sum-game prism is one-sided. As their relations become increasingly interdependent, China and Western countries also have a strong motive to cooperate in the developing world.