This paper presents a flexible microstrip low-pass filter (LPF) fabricated on a polyimide film substrate. The proposed flexible microstrip LPF with ten cascaded asymmetrical Pi-shaped defected ground structure (DGS) resonators are designed, simulated, manufactured, and measured. The simulation and experiment results demonstrate that the designed flexible microstrip LPF has a very sharp transition band, an ultra-wide stop-band (SB) and high rejection in SB performance compared with the existed microstrip LPFs with symmetrical and asymmetrical DGS. The proposed flexible LPF with ten cascaded resonators is with a compact size of 100 mm $\times2.6$ mm $\times0.254$ mm, a very low insertion loss of less than 1.9 dB under 2.2 GHz, and a wide SB from 2.7 to 12 GHz with the rejection of larger than 50 dB. The proposed flexible LPF has the potential to be used in wireless terminals to replace the traditional RF coaxial cable because it is very thin and has good transmission and filtering functions.

The design and implementation of printed helical spiral antenna (PHSA) and helical printed inverted-F antenna (IFA) are presented for unmanned aerial vehicle (UAV) with global positioning system (GPS) L1 band (1.57 GHz) and telemetry communication frequency band (2.33 GHz) applications. The proposed antenna is miniaturized by co-winding the radiation elements on the same ceramic rod, surface covering by dielectric sealant, inserting a high permittivity dielectric load into the helical structure, turning and meandering the radiation element of PHSA into a spiral parallelogram structure. The PHSA and helical IFA antenna radiation elements are manufactured by silver pasted on the same hollow ceramic cylinder with a diameter of 12 mm and a height of 24.7 mm. The experimental and simulation results show that the proposed PHSA and IFA can achieve the gain of 0.05dB and 1.97 dB respectively and be suitable for GPS L1 band and telemetry communication frequency band (2.33 GHz) applications separately.

A miniaturized ultrawideband active electric probe with high sensitivity for near-field measurement is proposed in this article. The probe is designed with a four-layer printed circuit board (PCB) with mainly two chips, an amplification chip (HMC797APM5E) which can work from dc to 22 GHz and a power management chip (HMC980LP4E). The probe can work from 9 kHz to 18 GHz with 15-dB average gain compared to the passive probe, and the flatness is about ±4 dB in terms of $\vert S_{21}\vert $ (transfer factor) from 2.5 to 18 GHz. The maximum size of the probe is 64 mm $\times41.5$ mm with 1-mm spatial resolution, and the width of the tip is only 4.1 mm, so the probe can handle most test environments. On the whole, the probe is very efficient for near-field measurement to detect weak signals in a wide bandwidth.

This paper proposes a novel air-filled grounded coplanar waveguide (AGCPW) structure for calibrating near-field probes. The structure uses a grounded coplanar waveguide (GCPW) with a cutout ground as the connector taper part to achieve a smoother impedance transition. Additionally, an AGCPW capable of exciting high-purity TEM fields serves as the probe calibration region. The designed cutout ground structure ensures good impedance control for the AGCPW, while a dual-row staggered via array suppresses high-order modes and resonance in the frequency range of 9 kHz to 40 GHz. Subsequently, the field characteristics above the AGCPW structure are analyzed, revealing an undesired electric-field rejection ratio (UERR) and an undesired magnetic-field rejection ratio (UMRR) of 36 dB and 26.5 dB. Applying AGCPW to calibrate an H -field probe with a four-layer PCB structure, the results show that, compared to using other structures, AGCPW yields a smoother and more stable probe calibration factor (CF) and more accurate electric-field rejection ratio (ERR) results.

A broadband pulse injection probe with improved injection efficiency for conducted electromagnetic susceptibility (EMS) is proposed in this paper. Improved injection efficiency is effective and crucial for conducted electromagnetic susceptibility testing of electronic devices. The effect of parameters such as coil material and wire diameter, the number of coil turns, and the distance between the coil and the shielding shell on probe injection efficiency is investigated in this paper. By using low impedance coils, symmetrical winding methods, and size-matched shielded shell, the broadband pulse injection probe with improved injection efficiency is obtained. The proposed broadband pulse injection probe was calibrated, and an injection efficiency comparison test was performed, proving that the proposed probe has improved injection efficiency. Meanwhile, the proposed injection probe performs well in electromagnetic susceptibility testing in the 9KHz to 400MHz frequency range. These results will be of great significance for the effective acquisition of electromagnetic susceptibility test data and the optimal design of electromagnetic compatibility (EMC) of integrated circuits (ICs).