Over-the-air (OTA) measurements are the standardized methods to evaluate radio performance in wireless systems. EMC issues such as interference and receiver desensitization are important factors. In this paper, OTA measurement challenges in the upcoming fiftth generation (5G) wireless systems are overviewed. Several key technologies that could be widely used in the 5G OTA measurements are discussed, including near-field to far-field transformation, anechoic chamber absorbers, and sampling antennas. The most important devices under test (DUT) for 5G OTA are chip sets, user equipment, and active array systems. The OTA test challenges for certification, research and development, and mass production for these DUTs are introduced.

With rapid increases in the number of vehicles over recent years, urban parking systems have encountered more and more challenges. In this paper, a dual-lens millimeter wave (MMW) radar antenna is designed for a smart parking system in the context of the Internet of Things (IoT). A flat dielectric punch lens is used to increase the gain of the transmitting antenna in order to compensate for the penetration loss in MMW. In addition, a dielectric rod lens is used to correct beam direction and maintain a wide beamwidth in order to overcome received energy loss due to scattering of the car chassis. The combined dual-lens antenna can improve the accuracy and stability of MMW radar operating at 24 GHz. The measured gain is 15.8 dBi for the transmitting antenna and 7.9 dBi for the receiving antenna, and the 3 dB beamwidth is approximately 65 degrees. The system measurement results show that the proposed antenna has stable measurement effect and is suitable for the MMW radar smart parking system.

A low-cost, wideband PCB manufactured antenna is proposed in this letter for 5G/6G antenna-in-package (AiP) applications with wideband common-mode current (surface-wave) choking characteristics. The antenna is based on a grounded, wideband, high-efficiency electromagnetic structure (WHEMS) and a backing cavity, through both of which a radiating choke is introduced. By changing the choking condition of a quarter wave length widely applied in traditional low frequency baluns, wideband common-mode current suppression is achieved. The enclosing wall of the backing cavity is realized by a combination of isolated grounded vias and connected grounded vias based on current polarizations on the wall. Finally, a 22% impedance bandwidth (60-75GHz), and a relative gain of 8-10 dBi within the band is achieved.

The explosion of applications of Internet of Things (IoT) wireless devices urgently requires over-the-air (OTA) performance evaluations. However, the challenges mainly due to the fact that the ubiquitous IoT device applications have made it necessary for OTA measurements to be operated in accurate, fast, and cost-effective ways. This paper proposes a series of solutions for improving the standard OTA measurements to meet the IoT OTA requirements. For single-input single-output (SISO) terminals, three test techniques are introduced for speeding up their total isotropic sensitivity tests and improving the test accuracy. For IoT multi-input multi-output (MIMO) devices, the radiated two-stage (RTS) method is introduced. The detailed theories are described mathematically, including the pattern measurement error elimination and the inverse matrix auto-solving. The advantages of the RTS on MIMO system diagnosis are outlined. Besides, a smart test system was introduced, which is suitable for a general office building. Both SISO and MIMO can be conducted in this chamber, resulting in great cost saving. Thus, with innovations on hardware and methodologies, the OTA evaluations can be accommodated and helpful for the IoT industry.

A multiband dual-polarized omnidirectional antenna for 2G/3G/LTE mobile communications is proposed in this paper, which consists of horizontal polarization (HP) and vertical polarization (VP) element with separate feeds. The VP element consists of three polygonal radiation patches with three equally-spaced legs shorted to the ground plane. The HP element consists of three wideband slot loop structures, which is nested on the top of the VP elements. Three slot loop structures enhance the bandwidth of HP, and the simulated and measured results both indicate that the frequency bands of 1650-2900 MHz for HP and 780-2700 MHz for VP can be achieved. Nesting improves the gain of the HP element at least 1dBi for the reflection of VP. The gain of HP element is more than 3 dBi for long term evolution (LTE), and the gain of VP element is more than 5 dBi in LTE band and 1.5 dBi in 2G band. Port isolation larger than 30 dB and low gain variation levels are also obtained. The proposed antenna can be applied in mobile communications.

Ultra-wideband (UWB) ranging techniques can provide accurate distance measurement under line-of-sight (LOS) conditions. However, various walls and obstacles in indoor non-LOS (NLOS) environments, which obstruct the direct propagation of UWB signals, can generate significant ranging errors. Due to the complex through-wall UWB signal propagation, most conventional studies simplify the ranging error model by assuming that the incidence angle is zero or the relative permittivities for different walls are the same to improve the through-wall UWB localization performance. Considering walls are different in realistic settings, this article presents a through-multiple-wall NLOS mitigation method for UWB indoor positioning. First, spatial geometric equilibrium equations of UWB through-wall propagation and a numerical method are developed for the precise modeling of UWB through-wall ranging errors. Then, calculated error maps are determined numerically without field measurements. Finally, the determined error maps are combined with a gray wolf optimization algorithm for localization. The proposed method is evaluated via field experiments with four rooms, three walls, and six penetration cases. The results demonstrate that the method can strongly mitigate the multi-wall. NLOS effects on the performance of UWB positioning systems. This solution can reduce project costs and number of power supplies for UWB indoor positioning applications.