In this letter, a compact dual-band MIMO antenna, consisting of four antenna pairs, is presented for 5G mobile terminal applications. Each pair includes two tightly-arranged monopoles. By folding the L-shaped monopoles into U-shaped structures, both the 3.5 GHz band and 4.9 GHz band can share the same decoupling inductor. By adding stop-band filter on the monopole, dual-band operation can be provided by a single branch. The size of the dual-band antenna pair is merely 19×4 mm ² . The measured -6 dB bandwidth can cover 3.4-3.6 GHz and 4.8-5.0 GHz, with port isolation higher than 12 dB. The measured radiation efficiency varies from 41% to 59% in the lower band, and varies from 38% to 62% in the upper band.

A sparse antenna array with flat-top and sharp cut-off radiation patterns is presented in this work. The array consists of sixteen antenna elements, which is realized by applying a symmetrical sparse configuration with uniform excitation phase. This configuration simplifies the excitations of the array while maintaining excellent radiation performance. The dual-band dual-polarized base station antenna based on the proposed sparse antenna arrays in the bands of 1.71 GHz ~ 2.17 GHz and 2.30 GHz ~ 2.69 GHz is fabricated and measured. The measured results are in very good agreement with the predicted ones, showing that the port reflection coefficient is less than -15.0 dB, and the isolation is greater than 28.5 dB. In addition, the array has a gain of 10.1 to 12.3 dB, a half-power beamwidth (HPBW) of 45° ± 5° in both the horizontal and vertical planes, a cut-off transition of less than 17.4° from -3 dB to -20 dB between the main beam and the sidelobe area, and a sidelobe level suppressed to below -21.1 dB. Apart from the good radiation performance, the proposed sparse antenna array has a compact size with very few antenna elements, which is very suitable for communication in a crowded scene.

Non-contact vital sign detection technology has brought a more comfortable experience to the detection process of human respiratory and heartbeat signals. Ensemble empirical mode decomposition (EEMD) is a noise-assisted adaptive data analysis method which can be used to decompose the echo data of frequency modulated continuous wave (FMCW) radar and extract the heartbeat and respiratory signals. The key of EEMD is to add Gaussian white noise into the signal to overcome the mode aliasing problem caused by original empirical mode decomposition (EMD). Based on the characteristics of clutter and noise distribution in public places, this paper proposed a static clutter filtering method for eliminating ambient clutter and an improved EEMD method based on stable alpha noise distribution. The symmetrical alpha stable distribution is used to replace Gaussian distribution, and the improved EEMD is used for the separation of respiratory and heartbeat signals. The experimental results show that the static clutter filtering technology can effectively filter the surrounding static clutter and highlight the periodic moving targets. Within the detection range of 0.5 m~2.5 m, the improved EEMD method can better distinguish the heartbeat, respiration, and their harmonics, and accurately estimate the heart rate.

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.

Non-periodic body movements is one of the most challenging issues in non-contact vital sign detection. The considerable and irregular displacements of the human body could corrupt the vital sign signals, drastically reducing detection accuracy. In this paper, an adaptive motion noise cancellation scheme based on Frequency-Modulated Continuous Wave (FMCW) virtual antenna array radar is proposed for real-time monitoring of vital signs with large body movements. This scheme suppresses the nonlinear noise caused by body motion and extracts accurate vital sign data. The proposed method is validated through simulation using a model of the vital sign detection system. Experiments were then carried out using a 77 GHz non-contact vital sign detection system, and the results were compared with data from a wearable device (MI6). The static experimental outcomes show that the errors in respiratory rate (RR) and heart rate (HR) are within 2 bpm and 3 bpm, respectively. The results of exercise test, with a velocity range of 0 to 0.5 m/s, show that the error of RR and HR is kept within 5bpm. The experimental results demonstrate the high efficiency of the algorithm in suppressing motion noise and accurately extracting RR and HR.

This paper presents a realization of a D -band multibeam lens antenna based on 3D printing. It extends all-metal Luneburg lens to terahertz band for the first time, and demonstrates the application potential of 3D-printed antenna in the associated communication and radar systems. Compared with the traditional D -band antenna, the structure of our antenna is simple, which is only composed of a Luneburg lens and a waveguide feeder array. On this basis, we manufacture an antenna prototype through the process of projection micro-stereolithography 3D printing combined with magnetron metal sputtering for verification. It has the advantages of low cost, high precision and integrated processing. The measured results of the prototype indicate that the reflection coefficients are below –10dB within 110GHz to 170GHz, and its bandwidth is 42.8%. Also, a gain higher than 20dBi is obtained at the center frequency, and multiple beams scan loss is lower than 1.6dB from –45°to +45°, which agree well with the simulation results.