In this paper, an open transverse electromagnetic (TEM) cell for electro-optic (EO) probe calibration is designed. The simulated and measured $S$-parameter results are in good agreement, indicating an operational frequency range from DC to 1.9 GHz. Meanwhile, the performance of the TEM cell has been validated through probe calibration, including both frequency response and input/output performance. The results demonstrates that the proposed compact TEM cell is well suitable for the low-frequency characterization of EO probe.

Stirring efficiency is a key metric for evaluating the performance of stirring technique. However, traditional mechanical stirrers offer limited efficiency. In order to improve the efficiency, we replace two mechanical stirrers with three circular turn-table platforms with randomly distributed rectangular elements. Several characteristics, including correlation coefficient, independent samples, K-factor and field uniformity (FU) have been quantified to assess the performance. The measurement results indicate that the proposed platform stirring outperforms mechanical stirring.

Dynamic electromagnetic environment demands real-time, multidimensional awareness, which drives the development of reconfigurable intelligent antennas. In this paper, a compact frequency and pattern reconfigurable monopole antenna is proposed. The antenna is composed of a serpentine-shaped reflecting patch and a defected ground structure (DGS) fabricated on an FR4 substrate. By controlling five PIN diodes, the effective radiator length will be changed, which can tune the frequency bands operated at 2.9 GHz and 3.2 GHz. Simultaneously, by altering the asymmetric surface current distribution, the radiation pattern can be switched among three distinct modes: +100 degrees directional, -100 degrees directional, and omnidirectional. The operation bands of the antenna range from 2.70 GHz to 3.13 GHz in the first mode and 2.87 GHz to 3.53 GHz in the second mode. The bandwidths of the antenna are 14.8% and 20.6%, respectively. This design offers significant potential for adaptive wireless systems requiring simultaneous optimization of operating frequency and spatial coverage in dynamic environments. Experimental results confirm the antenna's successful realization of both frequency agility and radiation pattern diversity.

A compact spherical dipole antenna (SDA) is proposed for cabinet shielding effectiveness (SE) testing. Constrained to a 150-mm diameter and operating from 30 MHz to 1 GHz, the antenna is electrically small at the low frequencies, which inherently limits broadband impedance matching and radiation efficiency. To enhance practical radiation performance, two cone-sphere radiators are introduced to form a quasi-TEM conical transition for geometry-based impedance improvement. In addition, a metallic feeding cavity is designed and optimized to suppress feed-cable radiation and maintain omnidirectional patterns. A 3-D-printed prototype is fabricated and measured, showing good agreement with simulations. Across the test band, the minimum VSWR is 1.92 and the peak total efficiency reaches 84%, demonstrating that the proposed SDA is a compact and repeatable radiation source for cabinet SE measurements.

Specific absorption rate (SAR) measurements for the human exposure in vehicles generally follow the standards such as IEC 62209 series, but these standards do not account for the in-vehicle propagation environment, including reflections, multipath effects, and cavity resonances. In recent years, an increasing number of studies have focused on evaluating SAR in realistic scenarios. Numerical simulations have indicated that enclosed vehicle cabins significantly affect the SAR distribution. However, systematic measurement results and analyses of in-vehicle SAR have not been sufficiently reported. To address this gap, this paper proposes an in-vehicle SAR measurement system capable of estimating the local SAR on a full-body phantom under realistic vehicular conditions. Compared with conventional planar phantoms, a seated human phantom is designed to better represent in-vehicle postures. Tissue-equivalent liquids covering 0.2-6 GHz are developed to satisfy the requirements of IEC 62209-3. An E-field monitoring module interfaces with the phantom to enable local SAR measurements at different depths within the liquid. A three-antenna method is used to calibrate the E-field probe in the liquid. Simulation and measurement results demonstrate consistent local SAR evaluations with good agreement. Furthermore, the in-vehicle local SAR is measured and compared with existing numerical in-vehicle local SAR assessments. The proposed measurement system provides a practical and convenient approach for in-vehicle local SAR estimations.

The total scattering cross section (TSCS) of a perfect electric conductor (PEC) sphere in a reverberation chamber (RC) is investigated with analytical derivations, numerical simulations, and experimental validations. Based on Mie theory and statistical properties of the field in an RC, analytical expressions for the TSCS and its approximations are derived. The numerical TSCS is evaluated using the proposed full-wave simulation spherical integral method and the conventional Monte Carlo method. Comparisons between the analytical and numerical results validate the derived expression and demonstrate the efficiency and accuracy of the proposed method. Finally, the TSCS of a PEC sphere with a radius of 75 mm is measured and compared with both the proposed analytical TSCS model and previously reported results, showing good agreement over a range of electrical sizes. The proposed analytical model provides a useful reference for quantifying scattering effects of the object in an RC.

The transmission cross section (TCS) of an electrically large dielectric interface is evaluated. By computing the plane wave reflection coefficients from both sides of the aperture, the corresponding TCSs are obtained using numerical integral. It is interesting to find that the average TCS can be derived analytically, and the ratio of the average TCSs from two sides of the interface equals the ratio of the dielectric permittivities. Both integral representations and analytical expressions of the average TCS are derived, and full-wave simulations are conducted in dielectric-filled reverberation chambers (RCs) for validation.

With the development of mobile communication technology, radiated signals from wireless devices have become increasingly complex. Waveform duration can extend to the millisecond range, making conventional full-wave (FW) specific absorption rate (SAR) simulations computationally intensive and time-consuming. To address this challenge, this article proposes a two-step method for local SAR evaluation under complex excitations. First, the magnitude of the transfer function |H(f)| between the input signal and the E-field at a specified location is extracted. Second, the input power spectrum P-in(f) is combined with |H(f)| to reconstruct the E-field and calculate the local SAR. For a given scenario, |H(f)| can be efficiently obtained using a Gaussian pulse excitation and then reused to evaluate local SAR for different modulated signals without repeating FW simulations. For other configurations, |H(f)| is re-extracted once for the new scenario. Dipole and two-peak antennas are used to simulate |H(f)| and demonstrate signal reusability. Measurements are performed at 2.45 GHz using a two-peak antenna excited by modulated signals (M5, M6, and M10). Measured peak local SAR agrees well with the proposed method, with a mean absolute error of 3%-10%. Overall, the proposed method provides an accurate and efficient approach for estimating the local SAR for different complex excitations.

This paper exploits the random field gain of a reverberation chamber (RC) to study how the RC affects the power difference between the carrier component and the third-order intermodulation component in passive intermodulation scenarios. By comparing the power difference before and after a single RC section and three cascaded RC sections, models are designed to evaluate both the theoretical and empirical probabilities of the power difference distribution. The results show that the probability of reducing the power difference by 10 dB is about 10 percent for a single RC section and about 22 percent for three cascaded sections. The probability of reducing the power difference by 20 dB is about 1 percent for a single section and about 8 percent for three cascaded sections. These results indicate that an RC can be used to enhance the dynamic range in PIM measurement. They also provide practical insight for PIM mitigation and filter selection in engineering applications.

A hardware-decoded latch control system is presented in the paper. The digital phase shifter controller serves as the control unit of the phased array beamforming network. It converts the phase difference commands calculated by the beam steering computer into executable control signals (logic levels or analog voltages) for digital phase shifters, implementing synchronized loading and precise control of phase states across 64 antenna elements. This system enables accurate beam steering.

A circularly polarized (CP) patch antenna array with an oblique beam is proposed, which can effectively broaden the satellite-ground communication link area as the satellite rotates mechanically. The array consists of six subarrays with 12 antenna elements, covering the typical L1 frequency band of Global Navigation Satellite Systems (GNSSs) from 1.544 to 1.615 GHz. Three main issues are mainly addressed, including the array axis-ratio (AR) bandwidth enhancement, the array tilted beam design, and the environment suitability in aerospace. The sequential feeding with a 90 degrees phase shift is preferred in the subarray to improve the 3-dB AR bandwidth (ARBW). To realize a 30 degrees oblique radiated beam with specified gains, the trust region framework-aided beamforming technique is applied to optimize the phase differences between adjacent subarrays. The high-temperature alumina ceramic and WL-CT300 dielectric substrates are integrated to extend the array working temperature from -50 degrees C to 260 degrees C. Both simulations and measurements are conducted. It is demonstrated that the maximum realized gain is 10.56 dBi at 1.575 GHz, and the 3-dB ARBW is 110 MHz or 7% in fraction. The proposed CP patch antenna array shows excellent performance in terms of high gain, wide ARBW, lightweight, and environment suitability, making it a promising candidate for satellite wide scanning coverage applications.

This paper presents an X-band frequency-reconfigurable antenna fabricated by 4D printing technology. NiTi shape memory alloy radiating units in the proposed antenna exhibit dimensional changes in response to temperature variations, thereby enabling frequency tunability. Experimental results demonstrate a broad frequency tuning range from 8 GHz to 12 GHz, with a peak gain exceeding 6 dBi. The compact design of the antenna, with dimension of 50 mm × 50 mm × 5 mm (1.67 λ × 1.67 λ × 0.17 λ at 10 GHz), offers enhanced frequency reconfigurability, reduced size, and increased design flexibility. These characteristics makes the proposed design a promising candidate for X-band satellite communication applications.

This paper presents a liquid HF antenna fed by a detached feeding structure. The feeding structure consists of a ferrite core, coil windings and shielding shell, which provides an inductive coupling for the monopole antenna. By dynamically tuning the water tube height, the antenna covers a wide range from 13 MHz to 18 MHz ($\mathrm{S}_{11}<-10 ~\text{dB}$), and achieves 25 % total efficiency. Simulations are performed and results show that the permittivity and the coling widings of ferrite core are important for the antenna efficiency. The proposed antenna exhibits omnidirectional radiation patterns and requires no soldering during installation.

In this paper, a fast and efficient permeability measurement method for ferrite core is presented. By measuring the reflection coefficient of the short-circuited coaxial cavity, the permeability of the ferrite core can be determined. Precise analytical expressions for the ferrite permeability are derived through the equivalent transmission line model. Both simulations and measurements are conducted, the operational range of the relative error below 10% has been established. It can be used for precise permeability measurement of ferrite core.

Identifying the power difference and phase shift of a phased array antenna (PAA) is essential in the PAA calibration. In this article, the ability of calibrating a PAA in a reverberation chamber (RC) is explored. Based on the proposed RC calibration system, the power and phase of each array element are measured in an RC. The relative power difference and phase shift are also calculated. The role of the mechanical stirrer is discussed. To verify the accuracy of the proposed method, we compare the calibration results with those obtained from the direct link method, and the measurement results are consistent. The proposed method validates the feasibility of PAA calibration in an RC, particularly when performing measurements of phase.

This article proposes an alternative method to estimate the total isotropic sensitivity (TIS) of a device under test (DUT) in a reverberation chamber (RC). To improve the measurement efficiency of the conventional TIS RC method, we fully utilize the received status (connected or failed status) of DUT and the statistical properties of received power to obtain the TIS without power-tuning and repeating measurements. Additionally, a multiprobe RC is used to accelerate the measurement process. Compared with the conventional method in the RC, the proposed method achieves a mean error of 0.34 dB and reduces measurement time greatly. The Monte Carlo method is used to solve the essential correction coefficient. Estimated values and relative standard deviations are provided for different output powers from the vector signal generator.

AbstractAn S‐band near‐field focused array is designed and implemented. Consisting of 4 × 4 metallic Vivaldi elements, the array is designed for focusing the E‐field of several kilovolts per metre within its near‐field region. To minimise the power loss and enhance the synthesis effectiveness, elements are arranged on a sphere surface and oriented towards the sphere centre. When exciting the elements, the waves will be focused to a specific area on the observation plane. By adjusting the excitation phase, the focus position can be tuned. A systematic analysis has been carried out to illustrate the focus scanning process across the entire observation plane. Near‐field two‐dimensional scanning is performed to measure the E‐field distribution of the array. While scanning the focus, the diameter of 3 dB focal area is about 0.3 m, and the maximum field strength in the focus ranges from 1184 to 2129 V/m, which can be used for the radiated susceptibility testing.

Based on the long-short term memory (LSTM) network, a novel approach to obtain the quality factor ( Q factor) of reverberation chambers (RCs) is proposed and validated in this article. We compare the predicted results obtained from the LSTM network with that from the conventional coherence bandwidth method and give their corresponding relative errors. Results demonstrate that the LSTM-based Q factor estimation method can be applied for RCs with different dimensions and loadings. The proposed network shows advantages for estimating the Q factor of RCs, particularly when the number of stirrer positions is limited.

A liquid-loaded frequency tunable cavity bandpass filter (BPF) is presented.A dielectric fluidic material, dimethyl silicone oil (DSO) with excellent thermophysical characteristics (working temperature from -50 ℃ to 180 ℃) and extremely low loss tangent is employed as a dielectric loading.The frequency reconfigurability of the proposed design is realized by altering the liquid level inside the cavity resonator.The filter achieves a wide frequency tuning range as well as a high Q factor.Moreover, this design shows significantly improved environmental suitability in extreme temperature cases, outperforming the existing microfluidic-based RF devices using water or liquid metals.A four-pole tunable cavity bandpass filter is designed and verified.A cross-coupling structure comprising a metal loop structure is used to introduce transmission zeros in the proposed filter, which enhances the skirt selectivity and out-of-band rejections.We demonstrate that the center frequency of the proposed BPF can be tuned from 4.92 GHz to 6.16 GHz, and the filter achieves a high Q factor between 521 and 1527.The measured results agree well with simulated results.

This paper shows that the received power and E-field in a reverberation chamber (RC) can be shaped by tuning the statistical properties of input signals. For a given probability density function (PDF) of an RC response, the Fourier transform method can be applied to find the PDF of the input signal. Numerical and measurement verifications are given to validate the theory. Limitations are also analyzed and discussed.