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This communication proposes a novel fully metallic multibeam Luneburg lens antenna that can simultaneously support the radiation of horizontal polarization (H-pol) and vertical polarization (V-pol). The proposed Luneburg lens consists of a parallel plate waveguide with varying spacing and a series of loaded metallic nails with graded heights. Seven OMTs are employed as the feeder. The measured results show that H-pol/V-pol peak gain is higher than 10.9 dBi/13.8 dBi from 28 GHz to 32 GHz. The dual-polarized beam scan loss is lower than 1.1 dB from −48° to +48°. The results show its potential for application in the MMW multibeam and multipolarization system. [ABSTRACT FROM AUTHOR]

A fully metallic partially open corrugated waveguide (CW) is employed to construct the Ka-band linearly polarized (LP) and circularly polarized (CP) frequency-scanning (FS) periodic leaky-wave antennas (PLWAs) with the spatial coverages from backward ($\theta < 0$) to forward ($\theta > 0$). The waveguide structure is obtained by cutting a conventional CW in half along its longitudinal symmetry plane. The $n =-1$ space harmonic is generated effectively by the half-wavelength radiating slots on the corrugations. The broadside frequency is about 31.5 GHz. The LP and CP radiations are realized by rotating the radiating slots to different angles. The measured scanning ranges of the LP and CP PLWAs are from −42.7° to 16.5° in the band of 26.5–33.5 GHz and from −48° to 22.7° in the band of 26.5–34 GHz, respectively. The measured axial ratio of the CP PLWA is below 3 dB in the mainlobe directions varied with frequency. The prototypes and experimental results make contributions to the polarization control, scanning rate improvement, and profile reduction in the frequency-controlled millimeter-wave imaging and radar systems. [ABSTRACT FROM AUTHOR]

This article presents a Ka-band fully metallic crossover-in-antenna based on an anisotropic lens. The crossover-in-antenna is a multifunction device simultaneously acting as a waveguide crossover and a multibeam antenna. The anisotropic lens performs like a Maxwell fish-eye (MFE) lens and a Luneburg lens in different incident directions, supporting the transmission and radiation, respectively. The lens consists of a parallel plate waveguide (PPW) with gradient spacing loaded with periodic uniform cuboid posts, which can be treated as an array of anisotropic subwavelength unit cells with gradient equivalent refractive indices. The WR28 waveguides are employed as the input–output ports. A flare is added to improve the radiation and impedance matching of antenna channels. According to the experimental results, a waveguide crossover is well realized with the reflection coefficients lower than −15 dB and insertion losses mostly lower than 1.4 dB from 28.7 to 38.2 GHz. Meanwhile, a multibeam antenna with four independent beams is obtained in the whole Ka-band, showing the gains higher than 12.5 dBi and the radiation efficiencies higher than 87.8%. The results indicate that the proposed crossover-in-antenna has application potential in the high-density multifunction integration of millimeter-wave (mmW) systems. [ABSTRACT FROM AUTHOR]

A compact fully metallic millimeter-wave (MMW) periodic leaky-wave antenna (LWA) based on corrugated parallel-plate waveguides with high radiation efficiency and low machining complexity is presented in this letter. The LWA consists of a smooth plate and a corrugated plate that integrates the corrugation for slow-wave transmission line and the radiating slots. By introducing two different elements into one radiating unit, the open stopband effect is improved and the broadside scanning is realized. As an experimental verification, a prototype in Ka-band is designed, fabricated, and measured. The scanning beams with an angular range of 48° (from −42.5° to 5.5°) and the peak gains between 11.9 and 16.0 dBi are obtained in the frequency range from 28 to 40 GHz. The radiation efficiency is higher than 85%. The results indicate its application potential in the MMW imaging and radar systems. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive active ${N}\,\,+ 4$ coupling matrix approach for the design of integrated filter–amplifier. The feedback between gate and drain, which is neglected in a previous work, is considered, which improves the accuracy of the coupling matrix model for transistors. More importantly, the relationship between the coupling matrix and the noise figure is also established, which extends the coupling matrix method to tackle noise-related circuit functions. Substrate integrated waveguide (SIW) filters are used to implement an integrated $X$ -band filter–amplifier design and to validate the design approach in terms of return loss, gain, and noise. Compared with rectangular waveguide, SIW is utilized for its appealing advantages, such as lower production cost, easier fabrication, and most importantly easier integration with active components. A second-order filtering circuit is applied to simultaneously match the input and output of the transistor. The integration reduces the losses from the intermediate networks in conventional designs, which is particularly important when the frequencies go higher. The measurements agree very well with the simulations in terms of S-parameters, gains, and noise figures. [ABSTRACT FROM AUTHOR]

A novel waveguide-fed antipodal exponential tapered slot antenna (AETSA) is investigated to achieve wideband circular polarization. The proposed AETSA is fed by double-ridge waveguide and loaded with antipodal exponential tapered slots. The wideband axial ratio (AR) performance is discussed in detail. It is noted that this AETSA has a right-hand circularly polarized AR lower than 3 dB in 94.5% bandwidth, from 12.4 to 34.6 GHz, illustrating AETSAs potential in a wideband application. The measured VSWR is lower than 2.1 in the operating band. Gain varies from 8.3 to 18.3 dBi. This AETSA is suitable for millimeter-wave and terahertz wideband circular polarization applications. [ABSTRACT FROM AUTHOR]