In this letter, we proposed an approach to construct multiple-input-multiple-output (MIMO) channel in line-of-sight (LOS) environment. It could be a potential technique for high-speed data transmission in fixed broadband wireless access (BWA). Based on Ricean fading channel model, our research is focused on the characteristics of the channel matrix such as the condition number. The initial discussion starts from a 4 times 4 MIMO scheme that the four antennas formed a square array on each side. A design constraint for antenna arrangement as a function of frequency and distance is derived for the LOS MIMO communication. Since rigorous constraint is difficult to achieve in practice, simulation results of the acceptable deviation from optimal design in different cases are presented. Smart geometrical arrangement and multipolarization may also weaken this constraint

This article investigates flexibly using mixed coupling in substrate integrated waveguide (SIW) filters to efficiently improve selectivity. To this end, a mixed coupling structure is proposed, which can be used as a universal coupling module to efficiently produce transmission zeros (TZs) in an inline/conventional SIW filter without degrading the superiority of SIW. On this basis, a trisection with mixed cross-coupling is further proposed, which encloses all the structures inside two general SIW cavities and can be used as a universal cavity module to efficiently produce a quasi-elliptic response in an inline/conventional SIW filter without degrading the superiority of SIW. Three prototypes are designed, fabricated, and measured, and the results agree with the expectations well. The proposed techniques should facilitate the development of high-performance SIW filters in microwave/wireless circuits and systems.

This letter presents a wideband circularly polarized (CP) magneto-electric (ME) dipole antenna array for millimeter-wave (mmW) applications. According to the design evolution, the proposed antenna element comes from a linearly polarized ME-dipole fed by an H-shaped slot, in which the microstrip patches work as electric dipoles, and the widths of the patches are first tuned to achieve an elliptically polarized wave. Then the L-shaped strips are loaded on the patches to further deflect currents, and two CP ME-dipole modes are generated by electric and magnetic currents in parallel. Next, some perturbations, including the conversion of L-shaped strips to F-shaped strips and the partial truncation of a pair of patches, are adopted to further improve the AR performance. The proposed CP ME-dipole antenna finally achieves an overlapped operating bandwidth of 32%. For verification, a 1-to-64 microstrip feeding network is designed to build a corporate-fed 8×8 array. The measured results indicate that the proposed CP array achieves an overall bandwidth of 31.7% covering 30.2 to 41.6 GHz, a peak gain of 22 dBic, and a radiation efficiency of greater than 64%. With outstanding CP performance and compact size, the proposed CP array is an attractive candidate for mmW and satellite communications.

A high aperture efficiency endfire antenna based on odd mode spoof surface plasmon polaritons (SSPPs) is proposed in this paper. First, a pair of symmetrical SSPPs transmission lines are applied to an endfire antenna. To realize an endfire antenna, the SSPPs transmission lines are supported by a balun with a 180° phase shifter, and this makes each pair of SSPPs units work as a dipole. Next, we study the dispersive curve of this dipole-shaped SSPPs unit and get its relationship between phase constant and frequency. Then, the Hansen-Woodyard condition is used to get a maximum gain at endfire direction. Moreover, in order to excite a radiation into the free space, we compose a tapered structure with this pair of SSPPs transmission lines. As a result, an endfire antenna with zero tilted angle operates in the frequency range of 9-11GHz and achieves an average gain of 11.51 dBi. Besides, this SSPPs antenna realizes a high aperture efficiency up to 13.26 dBi /λ ₀ ² . The simulated and measured results are in good agreements over the operating band. The proposed SSPPs endfire antenna holds a low profile, small aperture and it is promising for application in satellite and radar communication systems.

A wideband and high-gain planar endfire antenna based on spoof surface plasmon polaritons (SSPPs) at millimeter-wave (MMW) band is presented. First, a unilaterally corrugated surface antenna is demonstrated to radiate endfire beam tilted up from the flat plane of the corrugated metal teeth due to the effect of finite ground plane. Then, a SSPPs endfire antenna is designed with two symmetrically corrugated surfaces on the double sides of a metal strip. To excite the desired beam, the feeding network is comprised of a power divider and two L-shaped slots, so as to simultaneously produce oppositely tangential electric fields and identically normal electric fields. Moreover, the two equivalent identically tangential magnetic current sources above the corrugated surfaces are excited by flared feeding slot transitions. As a result, a synthetic endfire beam with zero-tilted angle is achieved. In final, such an antenna, operating in a range from 30 to 50 GHz with 50% fractional bandwidth, is designed with maximum gain of 16 dBi, as well confirmed in the experiment. The proposed SSPPs endfire antenna holds a very low profile and it is promising for application in MMW communication systems.

In this paper, a complementary glide symmetric spoof surface plasmon polaritons leaky-wave antenna (SSPP-LWA) with high scanning rate and full-angle scanning capability is presented. The novelty of this design is attributed to the combination of the complementary glide symmetric cell SSPP structure with the odd-mode feeding, so as to achieve the purpose of increasing the scanning rate and full-angle scanning. A larger gradient of dispersion is obtained by gliding the symmetric cell structure with odd-mode excitation, and the space harmonics are excited to form radiation by periodically loading the upper and lower symmetric metal branches on both sides of the SSPP transmission line (TL). A theoretical approach on the full-angle continuous scanning is presented to analyze the conditions of single-harmonic operation, the effect of the current distribution of odd and even modes on the radiation in the endfire direction, and predict its radiation direction pattern by theoretical calculations. In order to verify the proposed method, we processed and fabricated the prototype of the proposed LWA, and the theoretical calculation, simulation and measurement results are in good agreement. The total length of the proposed LWA is 5.36 wavelengths, and it is able to achieve a full-angle scanning from -90° to +90° over a bandwidth of 2.1 GHz (4.35 to 6.45 GHz), with a high scanning rate of 4.6 °/%. It also has the advantages of low profile, high average gain (10.8dBi), high average radiation efficiency (90%), low sidelobe (<-10dB) and easy fabrication.