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A new method for pattern reconfigurable antenna (PRA) design is introduced on the basis of a two-element dipole array model in this communication. Firstly, a two-element dipole array loaded with varactor diodes is analyzed in detail. The two dipoles of the array are folded to form a square and the reconfigurable pattern characteristics of the array can be still explained by the phased array theory. And then, based on the two-element dipole array model, a patch top-loaded monopole antenna is proposed to design the PRA (denoted as PTMPRA). Applying the field equivalence principle, the antenna radiation can be analyzed with two couples of magnetic dipoles. The phase of the magnetic dipoles may be adjusted by the loaded varactor diodes, and the antenna can reconfigure the patterns in two orthogonal planes. The antenna is fabricated and measured. The studies validate that the new method for designing pattern reconfigurable patch antenna is simple and efficient.

This communication introduces a hybrid invasive weed optimization and particle swarm optimization (IWO/PSO) algorithm dedicated to pattern synthesis of conformal arrays. A 3 $\, \times \,$ 9 cylindrical conformal microstrip array is studied to demonstrate the proposed algorithm. The active element pattern of each element in the conformal array is extracted and the phase and amplitude of each excited voltage are optimized to achieve the required goals using the hybrid IWO/PSO algorithm. The results indicate that, compared with standard IWO and PSO algorithms, the introduced hybrid algorithm maintains the respective advantages of the IWO and PSO algorithms while excluding their respective deficiencies. Moreover, the hybrid algorithm is very reliable in achieving global optimality.

A wideband circular polarized (CP) switched-beam patch antenna array is presented in this communication. The switched-beam system consists of four two-section branch-line couplers, two wideband 45 phase shifters and 1 × 4 proximity-coupled L-probe feeding CP microstrip patch antenna array. With such an arrangement, the proposed array can obtain a wide axial ratio (AR) bandwidth than that of conventional switched-beam CP antenna array. Measured results showed this array has an impedance bandwidth over a frequency range of 4.04-5.78 GHz (~36%) for |S11

An ultrathin and broadband radar absorber comprising single-layer resistive frequency selective surface (FSS) is investigated in this letter. The resistive FSS layer constructed from resistive/low-conductivity treble-square loops is backed by a grounded foam material. Numerical results show that the proposed absorber can provide a 10-dB radar cross section (RCS) reduction for the conducting plate over the frequency range of 10.7-29 GHz, which is equivalent to a relative bandwidth of 92.2%. Moreover, the structure has the thickness of 2 mm (only 0.071 to 0.193 at lowest and highest frequencies, respectively). The equivalent circuit model is then used to introduce the working principles of the proposed absorber.

A novel phased array is presented to extend array scanning range by using pattern reconfigurable antenna elements and weighted thinned synthesis technology in this paper. The pattern reconfigurable microstrip Yagi antenna element is used as a basic element in array and it is capable of reconfiguring its patterns from broadside to quasi-endfire radiation by shifting states of the PIN diode switches integrated on parasitic strips. A weighted thinned linear array synthesis technique is analyzed and some interesting conclusions have been made. A linear array composed of eight pattern reconfigurable antenna elements is manufactured to demonstrate the excellent performance of the array. The active element pattern of each element is measured and pre-stored. Based on active element patterns and weighted thinned linear array synthesis technique, the pattern scanning performance of the novel array is synthesized. The results indicate that the array can scan its main beam from φ = -60° to φ = 60° in H-plane with gain fluctuation less than 3 dB while maintaining low side lobes, and the -3 dB beam width coverage is about from φ = -68° to φ = 68°. The performance is superior to the traditional phased array made of wide-beam elements.

A circularly polarized switched-beam patch antenna array with butler matrix is designed and experimentally demonstrated in this letter. With suitable rotation technique, circular polarized radiation can be improved for beam steering. Also, this technique enhances the axial-ratio (AR) bandwidth within its scanning angle. Measured results showed this array has an impedance and AR bandwidth over a frequency range of 5.75-6.2 GHz when the main beam of array is scanned to different directions. Good agreement is observed between simulation and measurement.