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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.

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.

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.

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

This paper designs a magnetoelectric (ME) dipole leaky wave antenna (LWA) based on substrate integrated waveguide (SIW) technology for millimeter-wave application. The proposed antenna, which has 24 elements of ME dipoles and transverse slots, is built on a two-layer printed circuit board. The two shorting vias are adopted to load the LWA unit for eliminating the open stopband. The designed antenna works at 28 GHz band with wide impedance bandwidth of 34.5%. The simulation results demonstrate that the beam scanning range is from −39° to +37° at the whole operating band.

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)

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)

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.