A compact rectangular monopole with an equal-width ground plane is presented. This novel structural configuration could significantly improve its radiation performance and decrease its size. The feeding structure composed of a trident-shaped strip and a tapered impedance transformer is presented and discussed. Its impedance bandwidth, defined by measured VSWR less than 2, is from 2.75 to 16.2 GHz with a ratio of about 5.9:1. Both numerical and experimental results show that the proposed monopole antenna has stably omni-directional H-plane radiation patterns with low cross-polarization level within its impedance bandwidth. This novel monopole antenna has ultrawide impedance bandwidth, very compact size (30 mm*8 mm), low fabrication lost, and omni-directional H-plane radiation patterns, which are suitable for various broadband applications.

A truly all-dielectric metamaterial absorber, made of subwavelength water-based resonators and free of metallic ground, is designed, fabricated, and characterized. We demonstrate theoretically and experimentally that our metamaterial features a highly uniform perfect absorption for frequencies between 7.74 and 23.56~GHz, perfect thermal stability for temperatures from 0 to 100°C, and excellent absorption performance for large angles of oblique incidence. The proposed metamaterial absorber can be fabricated at low-cost, is environment friendly, and may find potential applications in broadband scattering reduction and electromagnetic energy harvesting.

The direction finding method by the time modulated linear array (TMLA) is analyzed and verified. The direction of arrival (DOA) can be calculated out by analyzing the spectrum characteristic of the received signal after the time modulation. Its principle is as follows. Because of the periodic modulation, the fundamental and harmonic components are generated in each element simultaneously. After the combiner, the harmonic components’ characteristic of the combined signal is influenced by the DOA. Through analyzing their mathematical relationship, the DOA can be calculated out directly. Compared to existing direction finding methods, the proposed method has two main advantages. One is that only a single RF channel is used, the other is that its precision can be improved by the time accumulation. The main calculation amount of the proposed method locates in the spectrum estimation for the received signal and the matrix inversion for the harmonic characteristic matrix (HCM). Numeric simulations are provided to verify the proposed method, and related factors influencing on the direction finding precision is analyzed. A simple S band 8-element TMLA is constructed and tested to verify its effectiveness. Finally, some conclusions are drawn and the further research is sketched out.

A broadband dual circularly polarized patch antenna with wide beamwidth is presented. The patch is excited by four cross slots via a microstrip line with multiple matching segments underneath the ground plane. The four cross slots and the multiple matching segments are optimized simultaneously to obtain the best performance. Measurements show that the antenna has 10-dB return-loss bandwidth of 24%, 10-dB isolation bandwidth of 19%, 3-dB axial-ratio bandwidth of 16%, and beamwidth of 110 ^° . Moreover, the single feed makes it a good candidate for array design.

In this paper, an improvement for comprehensive learning particle swarm optimization (CLPSO) is presented, which is called adaptive comprehensive learning particle swarm optimization (A-CLPSO). Its ability to seek optimal point is verified by some kinds of test functions. Then, the A-CLPSO is used to guide antenna design and a new design model called semiautomatic design is introduced. This model contains two steps: rough design in which A-CLPSO is employed to obtain a digital configuration of an antenna, and precise design in which a continuous externality of the antenna is introduced according to the current distribution of the digital one and then its dimensions are optimized further by A-CLPSO. By the model, the designers' experience is no longer very important and the shape of the antenna is more reasonable than that obtained by traditional grid division. As an example, the design of a small multiband printed monopole antenna is carried out and the experiment results show the validity of the model.