Fayu Wan

Time Lag of Secondary ESD in Millimeter-Size Spark Gaps

This study relates to the delay of secondary electrostatic discharges (ESDs). The first motivation for this study is the fact that the delay value is a required input parameter for the simulation of the secondary ESD. The second motivation is that this delay is one limiting factor for the usage of spark gaps as protection devices. The objective is to determine the delay for different intended and unintended spark gap structures as this time delay will influence the peak current and rise time of the secondary ESD across these gaps. The intended application is ESD protection in consumer products, for that reason 0.5-3 mm gap distances and voltages up to 14 kV are considered at different humidity levels. Very long time lags are observed for clean sphere-to-sphere gaps requiring average field strengths >200 kV/cm to achieve a breakdown in a few nanoseconds in dry air. Humidity is shown to strongly reduce the time lag. However, if printed circuit board (PCB) spark gap geometries are considered the time lags are much smaller. Similar shorter lag times have been found in geometries that resemble more unintentional breakdown locations in a product.

Stub-Loaded Theory and Its Application to Balanced Dual-Band Bandpass Filter Design

Novel stub-loaded theory is presented and applied to design balanced dual-band bandpass filter with independently controlled passband frequencies and bandwidths. According to the presented stub-loaded theory, the first differential-mode resonance can be independently designed by the loaded stubs, while not affecting the second one. Besides, except for the main coupling path, one more coupling path between the loaded stubs can be used to independently control the coupling coefficient of the first passband. Therefore, both the passband frequencies and bandwidths of each differential passband can be easily designed. To validate the proposed idea, the balanced dual-band BPF is designed, simulated and measured. Simulated and measured results are well agreed.

Pulsed Power Combining System for W-Band Traveling Wave Tube Amplifiers With a Waveguide Combiner

A W-band high power combining system was designed to enhance the transmitter power for increasing weather radars detection ability to small cloud particles and detection distance. The high power combiner with high isolation between the input ports was designed and manufactured. The effects of amplitude and phase differences on the combining efficiency were examined. The W-band pulse power combining experiment for two home-made traveling wave tube (TWT) amplifiers were carried out with the high power combiner at the frequency range of 93.5-94.5 GHz. The output pulse power from the two TWTs are about 100 W and 120 W, respectively, with duty cycle 4%, and the combining efficiency is above 79%, with the maximum efficiency 84.6% at 94 GHz. The maximum output power of the combining system reaches 194 W at 94.3 GHz.

Canonical Transfer Function of Band-Pass NGD Circuit

This study introduces the generalised canonical transfer function (TF) of the band-pass negative group delay (NGD) circuit. The principle to identify the unfamiliar band-pass NGD circuits is suggested. Similar to the filter theory, the band-pass NGD TF can be established from low-pass to band-pass frequency transform. The fundamental characteristics of the NGD topology are described. The canonical TF feasibility is concretised with the second-order equivalent impedance constituted by passive elements. The synthesis formulas in function of the desired NGD level and bandwidth are analytically established. Application examples of band-pass NGD impedance synthesis, designed and fabricated are proposed as a proof of concept. Prototypes of band-pass NGD circuits with centre frequencies 1 and 1.5 MHz for the targeted group delay optimal values, respectively, −1 and −1.5 µs are designed and fabricated. As expected, band-pass NGD results in good agreement with the theoretical prediction were obtained with simple lumped circuits. In the future, thanks to theory simplicity, the NGD band-pass cell can be potentially useful for the signal delay correction.

A Novel W-Band Dual-Polarized Cassegrain Antenna for Cloud Radar

A W-band dual-polarized Cassegrain antenna for cloud radar is proposed. The aperture diameter of the main reflector of the antenna is 50 cm. By using a modified Magic-T structure in the feed horn, the antenna is dual-polarized with high port isolation. The measured results show that the port isolation is 44.7 dB. The gains are 47.3 dB and 49.5 dB for the two ports at 94 GHz, respectively, and the efficiency of the antenna is better than 87%.

75–110 GHz integrated active sextupler module

An integrated active sextupler module covering 75-110 GHz is developed and described in this paper. Discrete Schottky devices, commercial MMICs and self-designed passive circuits are included in this module. Multi-chip packaging technology is adopted to greatly simplify inter-stage interconnection, so the characteristics of compact and high reliability are achieved. In the aspect of circuit topology, considering the performance of each device and circuit, an technical route of frequency multiplying - pre-amplifying - power dividing - driving amplifying - frequency multiplying - power amplifying - power combining is chosen. Inconsistency between the final-stage PA MMICs is solved. Finally, the following results have been achieved: while pumped with 0 dBm input signal in the range of 12.5-18.4 GHz, output signal with a typical power of 14 dBm can be produced over the 75-110 GHz band. This performance is comparable to the foreign commercial products.

Improved Immunity Measurement of a Microcontroller to Conducted Continuous Wave Interference

This paper discusses an improved in-situ immunity mea- surement test bench of a microcontroller | PIC18F458 to conducted continuous wave interference (CWI). The updated measurement algo- rithm gives more accurate measurement result. Compared with nor- mal failure criterion, the DC shift failure criterion is adopted because it gives better description of the immunity behavior of the microcon- troller. Finally, the susceptibility results are explained in detail.

CONDUCTED EMISSION MEASUREMENT OF A CELL PHONE PROCESSOR MODULE

This paper discusses a conducted emission measurement of a cell phone integrated circuit. The industry standard measurement method is used to compare the measurement result to the deflned limit line. A data analysis method- short time fast Fourier transform (STFFT) is presented to help to analyze the result. The data consistency and repeatability is also analyzed.

The derivation of scaling relationship between acoustic and electromagnetic scattering by spheres

The rigorous theory of the conversion between the scattering of uniform plane electromagnetic wave by a perfectly conducting sphere and the scattering of uniform plane acoustic wave by a rigid sphere is studied in this paper. The conversion formula between these two different scattering based on two calibration curves is derived, which describes the quantitative relationship between acoustic and electromagnetic wave scattering at arbitrary frequencies by spheres of arbitrary sizes. In addition, the scaling relationship of the sizes of those two spheres and the corresponding frequencies are discussed in detail, and an indirect method of measurement of electromagnetic scattering by the spheres is proposed.