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A miniaturized broadband dual-polarized magnetoelectric (ME) dipole antenna with extremely high isolation and bandpass filtering response is proposed. A miniaturized $\Pi $ -shaped folded ME dipole antenna is presented to introduce extra capacitor and inductance for achieving a wide bandwidth. Then, a special feed network, which includes a microstrip-to-slot feed scheme and a $\Gamma $ -shaped feeding probe, is utilized to excite the ME dipole antenna for realizing current cancellation between the two ports, thus resulting in extremely high isolation.In addition, good filtering performance is generated by using the $\Pi $ -shaped folded ME dipole radiator and low-pass filters in the feed network. By employing this new structure, a wideband ME dipole antenna having high isolation, excellent out-of-band suppression, and small size is designed. It achieves very high isolation of beyond 45 dB over a wide bandwidth of 47.7% (1.68–2.73 GHz) and small size of $0.38\lambda _{0} \; \times \; 0.38\lambda _{0} \; \times \; 0.15\lambda _{0}$ ( $\lambda _{0}$ is the wavelength at the center frequency). Our antenna also achieves a good bandpass filtering response and the out-of-band sup(pression level) is beyond 18 dB.

An artificial intelligence deep learning algorithm is proposed to analyze a dual-polarized high-isolation antenna effectively. The method is a building model of multi-input target characteristics and multioutput dimensional variables based on a backpropagation algorithm (MIMO-BP). The inputs are defined as the desired targets of the two-port impedance bandwidths, average isolations, and maximum gains, and the outputs are described as the antenna's dimensional variables. A demonstrated antenna prototype verifies the method's effectiveness and the predicted antenna's performance. The experimental results show that the proposed MIMO-BP method has the advantage in terms of convergence speed (i.e., the total electromagnetic simulated number to obtain the desired design) and time costs, high isolation of better than 40 dB over the bandwidth of 3.47–3.58 GHz, and a maximum gain of 4.3 dBi for both ports, which was obtained in about 22.7 h. These features make it a competitive candidate for antenna optimization design.

This letter presents a hybrid decoupling technique to realize high isolation for dual-polarized dipole antennas. The proposed antenna consists of a cross-dipole on two horizontal layers, one in the x-axis direction directly fed by a coaxial line and its extended strip and another in the y-axis direction differentially excited by a wideband power divider. A wideband hybrid decoupling method is applied, and the designed antenna has a simulated port-to-port isolation of more than 52.4 dB in the overlapped −10 dB impedance wideband of 1.69–2.73 GHz (47.1%). The fabricated prototype obtains a high port-to-port isolation of more than 48.3 dB over the 1.73–2.73 GHz (44.8%) frequency band. At the same time, the antenna has a stable radiation pattern, realized gains of 8.6 ± 0.7 dBi at Port 1 and 8.7 ± 0.6 dBi at Port 2, and an average radiation efficiency of 86.2%. The above characteristics indicate that the proposed antenna qualifies as a candidate for the base station antenna system in the 1.7–2.7 GHz frequency band.

An enhanced isolation technique between two low-profile patch antennas is proposed. Two identical antennas are configured with two printed circuit boards (PCBs) spaced at 0.206λ0, where λ0 is the free-space wavelength at 3.5 GHz. Every antenna is a rectangular patch with four slots and two vias, vertically fed with a coaxial probe. A decoupling strip embedded between two antennas and a slot on the ground improves isolation, which would not deteriorate the cross-polarization and backward radiation levels. Two-port impedance match and isolation characteristics are analyzed when the two-antenna spacing varies from 0.159λ0 to 0.252λ0. The proposed antenna has a size of 0.817λ0 × 0.448λ0 × 0.038λ0. The fabricated prototype is measured, and the results demonstrate that the −10 dB impedance bandwidths are 3.37–3.61 GHz (6.88%), the port-to-port isolation is more than 45.2 dB, the realized gains are 4.53 ± 0.35 dBi, and the average radiation efficiencies are more than 70%. Therefore, the measured results agree well with the simulated, making it a promising candidate for in-band full-duplex applications in 5G terminal scenes.

A novel wideband circularly polarized (CP) dipole antenna is presented. The proposed antenna is configured with three horizontal layers of an electrical dipole, two parasite Π-strips, and a ground, where the electrical dipole is fed by a vertical microstrip balun, resulting in three CP modes. The 180° rotationally symmetric dipole generates two CP modes in the middle- and high-frequency bands. In order to improve the CP bandwidth, two 180° rotationally symmetric Π-strips are introduced and excite the third CP mode in the low-frequency band. The antenna prototype is fabricated, and the measured results show that the −10 dB impedance bandwidth is 1.63–3.98 GHz (83.78%), the 3 dB axial ratio bandwidth (ARBW) is 1.70–3.11 GHz (58.63%), the realized gain is 7.34 ± 0.32 dBi, and the average radiation efficiency is 80.61%. As a result, the 1 dB gain bandwidth is overlapped with the ARBW, and the realized gain has a high flatness over the ARBW. Therefore, the proposed antenna is a promising candidate for broadband CP wireless communication system applications.

The near-field magnetic probe ( ${H}$ -probe) is an essential diagnostic tool for analyzing electromagnetic interference in electronic products. Many types of ${H}$ -probes have been designed and manufactured in recent years. Nevertheless, the performance of these probes in practical magnetic field ( ${H}$ -field) measurement is not clear. In this article, six typical ${H}$ -probes with the same loop area, labeled as UHP11, SHP11, UHP12, SHP12, UHP22, and SHP22, are designed and fabricated. The key parameters that can evaluate the performance of ${H}$ -probes include frequency response (FR), intrusion of the probe to the device under test (DUT), spatial resolution (SR), common-mode electric field ( ${E}$ -field) suppression, and differential ${E}$ -field suppression. To analyze the key parameters of these probes, full-wave models of these ${H}$ -probes are simulated and compared with measurements. Meanwhile, the equivalent circuit models of these ${H}$ -probes are established to analyze ${E}$ -field suppression in ${H}$ -field measurement. The measurement results indicate that the shielded one-loop ${H}$ -probe with differential output ports (SHP12) achieves the best differential ${E}$ -field suppression, which is 26 dB at 5 GHz. In addition to the outstanding suppression performance on differential ${E}$ -field, its common-mode ${E}$ -field suppression is also the best and greater than 30 dB within 14.3 GHz. The SR of six ${H}$ -probes is basically consistent in the measurement. Except for the higher sensitivity of the two-loop ${H}$ -probes (UHP22 and SHP22), SHP12 shows the best comprehensive ${H}$ -field measurement performance.

A dual-band vertical polarization omnidirectional antenna is proposed with the same three substrates in a low profile. The design is configured with four horizontal layers, a wheel-shaped patch (Patch 1) with an outer loop strip on the upper of the top printed circuit board (PCB) (Sub1), a fan-shaped patch (Patch 2) on the top of the mid PCB (Sub2), a four-sector patch on the upper of the bottom PCB (Sub3), and a ground with a ring slot on the lower of Sub3. The four vertical layers are a central coaxial probe from Sub3 to Patches 1 and 2, four inner posts from Patch 1 to Patch 2, four mid posts from the ground to Sub1, and four outer posts from the ground to Patch 1. Based on the new structure, five resonant modes in the passband and one stopband are produced for omnidirectional radiation with vertical polarization. The measured results demonstrate that the impedance bandwidths are 1.62–2.8 GHz (53.4%) and 3.18–4.3 GHz (30%). Therefore, the dual-band operation with a profile as low as 0.053λL (λL is the wavelength at the lowest frequency of operation) makes the proposed antenna suitable for indoor mobile communications in the bands of DCS1800/PCS1900/UMTS2000/LTE2300 /LTE2500 and 5G NR n77.

Microstrip line (MS) is commonly used as a calibrator for probe calibration. However, some issues need to be addressed for high-frequency applications, such as ripple and attenuation caused by the embedded part of the calibrator. In this article, an ultrawideband de-embedding calibration method (DCM) for magnetic field probes is proposed. Two symmetric nonsoldering grounded coplanar waveguide (GCPW) calibrators, including Through and Line standards, are used to solve the de-embedded $S$ -parameter matrix of a three-port calibration system. Compared with the traditional calibration method (TCM), the proposed method can reduce the influence of the reflection and attenuation caused by the embedded part and preserve the intrinsic properties of the probe itself. By using the DCM with a symmetric and good matched GCPW calibrator, the ripples of the DCM decrease by 6.57 dB, which is 82% of the TCM with an MS, and the attenuation has been compensated by about 0.7 dB at 10 GHz. In addition, a new characterization method of common mode electric field suppression ratio (CMSR) for $H$ -field probe is also presented, and it is applicable to conduct emissions measurement in which a probe can detect signals without 90° rotation.

A compact dual-polarized patch antenna with L-shaped short pins is proposed. The proposed antenna is configured with two substrates of 1.524 and 1.5 mm thickness, stacked by two prepregs of 2 × 95 µm thickness. The top layer is a rectangle patch with a T-shaped slot, two T-shaped branches, and two L-shaped short pins, which are shorted to the bottom layer of the metallic ground with the same size pins, and is fed by two vertical coaxial probes. In total, two L-shaped short pins achieve high isolation between the two ports by introducing three rectangular slots etched on the ground, two L-shaped strips in the middle layer connected with the short pins, and two T-shaped branches. Moreover, a wider bandwidth is realized by two L-shaped strips. A prototype of 0.16 λ0 × 0.16 λ0 × 0.04 λ0 has been fabricated, where λ0 is the free-space wavelength at the center frequency. The measured isolation of better than 35 dB is obtained over the operating bandwidth of 3.46–3.58 GHz. The experimental results agree well with the simulation results, making it a competitive candidate for 5G applications in the indoor and terminal scene.