This article proposes an 8×8 high-efficiency low-sidelobe slot antenna array operating at Ka-band frequencies with a feeding network designed by a new printed ridge gap waveguide (PRGW). The device consists of a slot antenna element, a PRGW unequal feeding network and a strip-line to PRGW transition. The substrate integrated waveguide (SIW) slot antenna element fed by the PRGW through a coupling aperture has a wide bandwidth, and the isolation is also increased by adding metallized holes to the array. Compared with other gap waveguide (GWG) antenna arrays, our work realizes an antenna element fed separately due to the use of a PRGW with a compact mushroom cell size, which helps improve the properties of the unequal feeding network. In addition, the transition between the PRGW and strip-line is also designed with a wide band and low insertion loss. The measured reflection coefficient is less than -10 dB over a 6 GHz bandwidth (16%), the gain is more than 23.5 dBi in the working band, and the sidelobe level is -18 dB. In addition, the measured radiation efficiency of the array with a two-dimensional Taylor distribution is 41.69%.

In this article, a compact low-sidelobe 2-D monopulse antenna array has been proposed based on mixed gap waveguide (GWG)/hollow waveguide (HW) multilayer feeding network and a GWG monopulse comparator. The proposed antenna array is arranged and divided into multilayers based on the function for miniaturization and low losses. First, slot antenna elements, unequal power divider based on the GWG, and layers transition between different ridge GWGs are proposed. Then, monopulse comparator composed by groove GWG 3 dB 90° coupler and 90° phase shifter is proposed according to the network diagram for forming $\sum $ , $\Delta _{\text {E}}$ , $\Delta _{\text {H}}$ beams. By vertically integrating the above functional elements, the compact low-sidelobe 2-D monopulse antenna array is obtained. The measurement results show its impedance fractional bandwidth (FBW) is 12.6%, antenna gain is greater than 29 dBi, and the efficiency is 35%. Moreover, the levels of the sidelobe and null depth are about −25 and −35 dB, respectively.

It is of vital importance to stitch the two images into a panorama in many computer vision applications of motion detection and tracking and virtual reality, panoramic photography, and virtual tours. To preserve more local details and with few artifacts in panoramas, this article presents an improved mesh-based joint optimization image stitching model. Since the uniform vertices are usually used in mesh-based warps, we consider the matched feature points and uniform points as grid vertices to strengthen constraints on deformed vertices. Simultaneously, we define an improved energy function and add a color similarity term to perform the alignment. In addition to good alignment and minimal local distortion, a regularization parameter strategy of combining our method with an as-projective-as-possible (APAP) warp is introduced. Then, controlling the proportion of each part by calculating the distance between the vertex and the nearest matched feature point to the vertex. This ensures a more natural stitching effect in non-overlapping areas. A comprehensive evaluation shows that the proposed method achieves more accurate image stitching, with significantly reduced ghosting effects in the overlapping regions and more natural results in the other areas. The comparative experiments demonstrate that the proposed method outperforms the state-of-the-art image stitching warps and achieves higher precision panorama stitching and less distortion in the overlapping. The proposed algorithm illustrates great application potential in image stitching, which can achieve higher precision panoramic image stitching.

In this article, a six-port network using double ridge gap waveguide based on the multi-via mushroom (M-DRGW) is proposed at millimeter-wave frequency band, which covers the 5G N260 frequency range. First, the stopband of the multi-via mushroom unit cell has been analyzed. Then, simplified schematic of the six-port network is given, and the power divider/coupler based on the M-DRGW is designed to form the six-port junction. For measurement, the peripheral test circuit of the M-DRGW six-port junction is added, and the transitions between the ridge gap waveguide (RGW) and hollow waveguide are added. For the comparison with the performances of the proposed M-DRGW six-port network, the one based on the traditional metallic double RGW (DRGW) has also been designed, fabricated, and measured. The simulated and measured results show that the phase differences between port 1/2 and four output ports are within ±2.5° and ±5°, respectively, and the average value of transmission coefficient is around −8 dB.

This paper proposes a novel image large rotation and scale estimation method based on the Gabor filter and pulse-coupled neural network (PCNN). First, the Gabor features of the template image and its rotated one are extracted by performing the Gabor filter. Second, we present a modified PCNN model to measure the similarity between the Gabor features of the image and its rotated one. Finally, the rotation angle is calculated by searching the global minimum of the correlation coefficients. Besides rotation estimation, we also propose a scale estimation method based on the max-projection strategy. The Gabor feature image is projected along the estimated rotation angle, and the scale is calculated by searching the peak of this projection result. Moreover, experiments illustrate that the proposed method has high accuracy on rotation and scale estimation and is robust to noise. Compared with the state-of-the-art methods, the proposed approach has a more stable performance.