A novel mode-stirred reverberation chamber (RC) is designed and analyzed for millimeter wave bands. The size of the proposed RC with dimensions of 0.9 m $\times0.9$ m $\times1.1$ m is suitable for user equipment (UE) tests. Two Z-shaped mode-stirrers are applied to generate a uniform field. To fulfill the communication and test requirements for user equipment, reference, measurement and link antennas with a large bandwidth are utilized, which can support both the frequency range (FR) 1 and FR2 bands of the 5G spectrum. The lowest usable frequency (LUF) and mode density were first calculated and examined. Then, the power transfer function (PTF) from 2 GHz to 40 GHz was obtained to verify the path loss. Three measurement campaigns were carried out to verify the accuracy of the RC. Firstly, the transmission power of the passive antenna for a conductive test was compared with the RC over the air (OTA) total radiated power (TRP) for single-tone signals. Then, signals with bandwidths of 100 MHz and 400 MHz were applied. A maximum power difference of only 0.8 dB was found in the above two experiments. Furthermore, the TRP for the same commercial 5G UE in both RC and compact antenna test range (CATR) systems was measured and compared. To the best of the authors’ knowledge, this is the first work to provide TRP results for 5G millimeter wave bands in a RC. The test results show that the TRP values for the two systems are almost the same with a maximum deviation of 0.5 dB, while the time required to carry out tests using the RC is lower than that for the CATR system.

With the development of communication technology has come several measurement applications requiring plane-wave conditions for wireless-device characterizations in anechoic chambers. In this paper, a metasurface lens with a 2 × 2 feeding-antenna array is proposed and characterized to synthesize a plane wave in a near field for a fifth-generation (5G) millimeter-wave radio-frequency (RF) devices test. The metasurface lens, based on Jerusalem-cross elements printed on a printed circuit board (PCB) substrate, is used for controlling the phase-shift distribution of incident spherical waves. The lens has a size of 0.4 × 0.4 m and is designed to operate at a range from 24.25 GHz to 27.5 GHz, and its feeding-antenna array is located at a focal plane of the lens, which is parallel to the metasurface lens. The lens is studied and verified through simulations and experiments, and a uniform amplitude and phase-field distribution at a reduced distance of 1.2 m generated by the metasurface lens throughout a QZ are achieved. The worst-case amplitude and phase variation of the designed metasurface lens are ±0.75 dB and ±7.5°, respectively. The results show a plane-wave condition can be achieved in 5G millimeter bands through the proposed compact and effective metasurface lens. Moreover, the proposed metasurface lens is shown to be capable of reducing the plane-wave synthesizing distance compared to the compact antenna test range (CATR) with a significantly reduced system cost, making it an attractive alternative to antenna testing in 5G millimeter-wave frequency bands.

Conformal antennas have been widely used in many fields due to their advantages of low air resistance and better visual appearance. In this paper, an arced conformal leaky-wave antenna (LWA) for a designable directional beam is proposed. The antenna is achieved based on a substrate-integrated waveguide (SIW). On the upper surface, a series of non-uniform transverse slots are etched. In order to guide the design of the antenna, as another key contribution of this work, a theoretical model for the traveling-wave structure is established. Using the model, the radiation property of the LWA is analyzed. In addition, by inputting the desired beam direction, the structural parameters of the LWA can be generated through the model. To verify the performance of the antenna and the model, an LWA prototype working at 28 GHz was fabricated and tested in a microwave anechoic chamber. The experimental results are in good agreement with the simulation results. The antenna achieved a gain of 9.96 dBi with cambered surface area of 1.89 λ₀². The proposed method may be a promising candidate for conformal wireless communication applications.

With the rapid development and commercialization of 5G technology, calibration and RF testing using over-the-air (OTA) is becoming increasingly important. Due to the large size of the massive MIMO base station, it is very challenging to fulfill direct far-field (DFF) conditions in OTA tests. Conventional near-field (NF) testing methods suffer from long measurement times due to the stringent sampling requirements (e.g. NF to far-field (FF) transformation) or the requirement for expensive test equipment (e.g. compact antenna test range). In this paper, we propose a simplified extrapolation technique (ET) strategy to reconstruct FF radiation pattern based on mid-field (MF) phaseless measurements, with high measurement efficiency. The traditional ET uses polynomials with many terms to fit the radiated power of an arbitrary antenna at the radial direction, while the simplified ET only use few terms to fit the power variation in the MF, taking into account the structure and element excitation characteristics of common arrays such as base stations. The relationship between the element excitation mode and the coefficients of each fitted term is determined by detailed theoretical derivations. Then, the best-fitting polynomials are determined for different excitation modes. The antenna pattern of the base station is successfully reconstructed in an anechoic chamber by power measurements at two or three different distances of less than 1/4 of the FF distance. The robustness and effectiveness of the proposed method is experimentally verified by comparing the accuracy of the antenna pattern reconstruction with different fitting polynomials in the anechoic chamber for a practical base station antenna.

In millimetre wave (mmWave) frequency band, radio resource management (RRM) performance is characterised in plane wave conditions using radiated over‐the‐air test method, which is a challenging combination of protocol and radio frequency performance measurement. This article presents a novel design of multiple lens‐based compact antenna test ranges (CATRs) to simulate multiple angles of arrival from different base‐stations in RRM measurement. Only four lens‐based CATRs are proposed to create plane wave conditions at the device under test with six different angles of arrival and capable of accurately constructing the wireless propagation condition and minimising the diffraction and scattering between adjacent CATRs. The lens‐based CATR is the key element in the RRM measurement system, which is composed of a metasurface lens for phase alignment and a 2 × 2 feed array antenna for the emission of electromagnetic signals. The function and capability of the proposed lens‐based CATR is validated through simulation and measurement, that the worst‐case amplitude variation in the quiet zone region is lower than ±0.8 dB at 26 GHz, and phase variation is lower than ±7.5° in the designed quiet zone, which could be used in the fifth‐generation mmWave RRM measurement.

This paper proposes array antennas based on half Tyler (HT) distribution that can realize omnidirectional null-free (ONF) beams. Array 1 employs the usual edge feeding approach, working at 3.5 GHz with a bandwidth of 0.25 GHz, whereas array 2 operates at 26 GHz with a bandwidth of 3 GHz. We evaluated the far-field performance of linear arrays consisting of 6, 8, 12, and 16 elements. The simulation and measurement results show that the proposed HT approach can achieve a near-ONF pattern and cover a broad area of ±42° on an eight-element linear array. The ONF beam reduces community power fluctuations and increases power by 20 dBm in surrounding areas of the base station (BS). The fluctuation treatment effect can be influenced by adjusting the weighting of sidelobe depression (dp): compared to the uniformly excited one, for example, the maximum ONF gain of an eight-element linear operating at 3.5 GHz is only reduced by 0.5 dB when dp = −30 and by 1–2 dB when dp = −60.