This paper presents a near-field-focused (NFF) substrate-integrated waveguide (SIW) antenna at a center frequency of 35 GHz with 2-D steerable focus. The proposed antenna is achieved by combining an NFF leaky-wave slot antenna array with a focused multibeam SIW Rotman lens. In most of the existing NFF planar antennas, the total phase distribution on the radiating aperture is separated into two parts with respect to the E-plane and the H-plane, which leads to a large error and deteriorates the NFF performance. Here, a modified NFF planar antenna synthesis method is proposed to calculate the desired phase distribution on the aperture and completely eliminate such an error at the center frequency. The linear NFF leaky-wave slot antenna is designed to scan the focal point in the H-plane with the frequency. The 15 leaky-wave slot antennas are grouped in a special topology and excited by the focused SIW Rotman lens. In this case, multiple focal points can be generated in the E-plane. Moreover, an SIW matching load is developed to improve the NFF beam performance. The whole NFF antenna is integrated into a single-layer substrate. The measured results are in agreement with the simulated ones.

A dual-band shared-aperture variable inclination continuous transverse stub (VICTS) antenna is designed with good port isolation and a low profile. The operation bands, including 19.5 to 20.1 GHz and 28.8 to 29.6 GHz, locate at the regulated bands for K- and Ka-band mobile satellite communication. The design principle is “shared radiating aperture and independent feeding networks,” which means two feeding networks are integrated to share one radiating aperture. At the center frequencies of the two operation bands, that is, 19.8 and 29.2 GHz, the beam-scanning coverage in elevation is 38° × 2 and 60° × 2, respectively. The relative bandwidths in K- and Ka-bands are 3.0% and 2.7%, respectively. The maximal gains for the two bands are 24.33 and 28.52 dBi. Good port isolation greater than 90 dB at the lower band and greater than 20 dB at the higher band is obtained. A low profile of only 10 mm is achieved, that is, 0.65 and 0.97 λ0, at the center frequencies. This work is a good candidate for the K- and Ka-band mobile satellite communication under the restriction of cost and size.

A V-band wideband circularly polarized (CP) end-fire multibeam antenna array with the wide beam coverage is presented in this letter. Firstly, a wideband compact end-fire CP element with the wide axial ratio (AR) beamwidth is proposed. The design procedure and working principle of the element are discussed in detail. Besides, connected holes are used to reduce the mutual coupling and improve the AR performance. After that, a wideband substrate integrated waveguide (SIW) Butler matrix is designed to feed the antenna array. Finally, the multibeam antenna is fabricated, measured and investigated. The measured results demonstrated that the proposed multibeam antenna provides a wide -10 dB impedance bandwidth of 28.5% (55.5 GHz to 74 GHz) and wide 3 dB AR bandwidth of 24.6% (57 GHz to 73 GHz). Additionally, a wide beam coverage ranges from 45°~66° is achieved. Good agreement achieves between measured results and simulated ones.

A wideband air-filled plate array antenna with multistage impedance matching operated in D-band is proposed in this paper. To achieve the wide bandwidth, three stages of impedance matching are introduced in the 2×2 sub-array, including the step-profiled horn element, the step-profiled power divider cavity with two resonant points and a modified E-plane bend transition. The integrated step-profiled horn with simple configuration can realize broadband matching. Wideband T-junctions are combined together to form a corporate feeding network. Essential matching pins are introduced to break through the upper bandwidth restriction of the feeding network. Besides, the square aperture shape of the horn element and the air-filled feeding structure contribute to the high radiation efficiency of the proposed array. To satisfy the fabrication tolerance, the MEMS micromachining technology with a high etching precision is utilized. The experimental results show a wide 1-dB down gain bandwidth of 23.54%. The maximum gain is 33.24 dBi and the peak efficiency is 70.91%.

The analysis and design of a millimeter-wave conical conformal shaped-beam substrate-integrated waveguide (SIW) array antenna is demonstrated in this paper. After investigating the influence of the conical surface on the propagation characteristics of a conformal SIW, a modification for the width of a conical conformal SIW is proposed to obtain the same propagation characteristic along the longitudinal direction. This feature is indispensable to employ the classic equivalent circuit of a planar slot array antenna in the design of a conical conformal antenna. In this case, the design process of the conformal antenna can be simplified. An efficient and accurate model method of the conical conformal SIW antenna is presented as well. Then, a design process of the conical conformal SIW slot array antenna is introduced. Furthermore, to implement the transition between a conical surface and a cylindrical surface, a flexible SIWtransition is designed with a good impedance matching. Finally, two low sidelobe level (SLL) SIW conical conformal antennas with and without the flexible transitions are designed. Both of them have -28 dB SLLs in H-plane at the center frequency of 35 GHz.