A circularly polarised (CP) antenna with highly symmetrical radiation patterns and wide operating bandwidth is presented for millimetre‐wave (mm‐wave) applications. By loading four parasitic inverted‐F components around a SIW‐fed S‐dipole antenna, better axial ratio (AR) performance and higher gain performance are realised. Furthermore, the proposed antenna can achieve highly symmetrical radiation patterns in different elevation planes within a wide operating band. This unique feature makes it advantageous to more uniform signal coverage. To verify the effectiveness of the antenna, a prototype is fabricated and measured. The experimental results validate that the antenna covers the impedance bandwidth of 49.1% (21.2–35 GHz) and the AR bandwidth of 51.3% (20–33.8 GHz). Besides, the antenna peak gain can reach 10.42 dBic at 28.5 GHz. More importantly, the antenna can radiate extremely symmetrical and uniform waves in different elevation planes within a wide operating band (21–29 GHz). Attributed to these merits, the presented antenna shows great potential in various mm‐wave systems.

Electronic prostheses require a communication link to other on‐body nodes, for example, for control signal extraction. This link can be made wireless to improve user experience compared to wired solutions. Even though ample on‐body communication techniques have been described for wireless body area networks, in prosthetics, the efficiency of wireless links is often neglected, in particular when radio frequency (RF) antennas are used. This work aims to show the benefit of on‐body RF antenna design for prosthetics, by developing a dedicated antenna for use in a lower arm prosthesis. Additionally, this work tries to fill a gap in literature, where some antennas for dedicated on‐body RF communication are presented, but no antennas specific for communication along the arm exist. To this aim, numerical simulations are performed using a cylindrically layered arm model to design a novel, electrically small, capacitively loaded, meandered, 2.45 GHz monopole antenna. The antenna is fabricated using 3D printed polylactic acid and validated both in a static human arm channel and in a dynamic setting, where the human subject performs various tasks. This antenna outperforms an off‐the‐shelf printed circuit board (PCB) antenna by 18 dB and a rectangular patch antenna by 4 dB in terms of link budget at a separation distance of 20 cm, both in line of sight and non‐LOS path loss experiments. Additionally, while performing four commonplace activities, the average power received increased by 20 dB in an on‐body link established between two of our novel antennas rather than two of the PCB antennas. These results will aid in the development of wireless prostheses used by a growing number of amputees.

In order to quantitatively evaluate the influence of the aberration of the antenna radiation pattern of airborne radar on clutter feature, the range‐azimuth two dimensional (2D) model of the airborne radar clutter is established. Then the theoretic modelling and simulation analysis are proposed in three aspects, including the Doppler, power spectrum and space‐time 2D characteristics of the clutter. Finally, the processing of moving target indication, pulse Doppler and space‐time adaptive processing are used to suppress the clutter of the echo signals before and after the aberration. The results of the simulations indicate the aberration would elevate the sidelobe level, extend the power spectrum and bend the space‐time trajectory of the clutter Doppler spectra. And the residual clutter would be elevated nearly 5 dB after STAP processing. Then the pattern preserving and fast time cancel combined space‐time adaptive processing method is proposed, which can obtain narrow clutter notch and large improvement factor, and effectively suppress clutter. The modelling and quantitative analysis study have important theoretical and engineering significance for the detection capability of the airborne radar installed on the fuselage of the aircraft platform, the tactical and technical performance index, and improving the signal processing ability of airborne radar.

imageIn order to quantitatively evaluate the influence of the aberration of antenna radiation pattern on clutter feature and the performance of the airborne radar, firstly, the range‐azimuth two dimensional model of the airborne radar clutter is established. Secondly, the theoretic modelling and simulation analysis, including the three aspects of Doppler, power spectrum and space‐time two dimensional characteristics of the clutter are proposed. Finally, MTI, PD and STAP processing's are used to suppress the clutter of the echo signals before and after the aberrance of the antenna radiation pattern.

A miniature quad‐band filtering power divider (FPD) based on a quad‐mode stub loaded resonator (SLR) is presented. The quad‐band FPD is formed by a proper coupling topology between the open‐ended microstrip line and two pairs of quad‐mode SLRs. Moreover, to achieve good isolation, two resistors are mounted between the symmetrical SLRs with respect to the open‐ended microstrip line properly. The proposed SLR is analysed by the odd‐ and even‐mode analysis method, and four passbands are accordingly introduced. For demonstration, a quad‐band FPD centred at 1.20, 1.66, 1.89 and 2.16 GHz is designed, simulated, fabricated and measured. The measured results have good agreement with simulated ones, which validates the proposed design concept.

A simple wideband planar antenna with a separated fence structure is presented in this study for 4/5G base station application. To improve the front‐to‐back ratio (FBR) and half‐power beamwidth (HPBW) of the proposed antenna, five parasitic separated fence structures are designed. This design can effectively suppress the surface wave propagating along the metal ground and increase the radiation performance of the proposed antenna in the low elevation area. After integrating the fence, the FBR of the proposed antenna is improved by 6 dB on average. And the HPBW is increased by on average above 3 GHz. Furthermore, a linear antenna array is designed and analysed. The measured results display that the proposed antenna achieves a wideband of 47.3% (2.22–3.64 GHz) for |S₁₁|≤ −10 dB with an isolation higher than 30 dB, which are in agreement with the simulations. The average HPBW, FBR, and gain of the proposed antenna is about , 22 dB, and 6.9 dBi in the operating band.

imageInverted Concave Separated Fence for 4G/5G Base Station Antenna Front‐to‐Back Ratio and Half‐Power Beamwidth Improving.