Unified probe launch pattern design and methodology of differential probe characterization

Differential probe is wildly used in the signal integrity area to do the accuracy signal measurement in frequency domain or time domain. Comparing with traditional SMA connector measurement, the probe measurement has several advantages such as the high flexibility and measurement efficiency. Nevertheless, the probe has some disadvantages such as multiple design patterns and the difficulty of fast landing. In this thesis, a unified probe landing pattern is provided to solve the con of probes and a probe testing fixture is designed for characterize probe and extract the probe model. In the first portion, a unified differential probe launching pattern is proposed for universal usage of different types of differential probes. Full wave-modeling of the transition with the unified probe launching pattern is developed for optimization of dimensions. For the unified probe launching pattern evaluation, 16-layer test vehicles were designed with engineered transitions for performance up to 40 GHz. Four-port measurement results of different differential pairs from the test vehicle are used as the 2x thru reference and DUT for de-embedding. By using GSSG probe, accurate DK and DF along with frequency can be extracted. In the second portion, a probe testing fixture is designed based on the unified probe launch pattern design to characterize the performance of probe based on the smart fixture de-embedding method. The full wave model is extracted from the fixture design to server future probing measurement design and the circuit model is extracted to study the effectiveness from the specific portion behavior --Abstract, page iii

Spatial resolution study for magnetic near-field probe

Spatial resolution is an important factor of near-field probe, which represents the ability to distinguish two close radiation sources. Traditional definition of spatial resolution is the distance between peak point and -6dB point when measuring microstrip line. The definition has disadvantage and limitation. In this topic, spatial resolution for magnetic near-field probe is studied, and three dimensions of spatial resolution are put forward. An optimized measurement setup is presented to reflect spatial resolution of probe properly. Then, an example is given to show how spatial resolution affects field distribution in near-field measurement --Abstract, page iv

Passive harmonic generation at spring contacts

In the first paper, the RF passive harmonic generation phenomenon on the spring contact is studied. A spring contact harmonic generation measurement system is developed. The factors that may have an impact on the spring contact harmonic generation, such as contact material, contact force, and contact resistance are characterized by the measurement system. The gold-to-gold contact is found to be much superior to the stainless-steel contacts. It is also found that the passive nonlinearity at the spring contact is the semiconductor-like junction formed by the surface oxide film. In the second paper, we show that the maximum E-field coupling occurs at a location slightly offset from the trace center. The E-field coupling to a shielded H-field probe at such a position leads to differential mode coupling which the standard shield of an H-field probe is unable to suppress. The coupling mechanism is investigated and a differential E-field coupling suppression approach is proposed. In the third paper, a measurement system which uses acoustic vibration to locate passive intermodulation (PIM) sources in base station antennas is presented. This measurement system uses mechanical vibration to modulate the PIM signal. By introducing the acoustic vibration at different locations in the base station antenna and observing if the PIM signal is modulated by the acoustic frequency, the most likely location of the PIM source is identified --Abstract, page iv

Design and Study of a Wide-Band Printed Circuit Board Near-Field Probe

Magnetic near-field probes (NFP) represent a suitable tool to measure the magnetic field level from a small electromagnetic interference (EMI) source. This kind of antenna is useful as a magnetic field probe for pre-compliance EMC measurements or debugging tasks since the user can scan a printed circuit board (PCB) looking for locations with strong magnetic fields. When a strong H-field point is found, the designer should check the PCB layout and components placement in that area to detect if this could result in an EMI source. This contribution focuses on analyzing the performance of an easy to build and low-cost H-field NFP designed and manufactured using a standard PCB stack-up. Thereby, the frequency range and sensitivity of the NFP-PCB are analyzed through a Finite Element Method (FEM) simulation model that makes it possible to evaluate its sensibility and effective frequency range. The numerical results obtained with the FEM models are validated against measurements to verify the design and performance of our NFP. The FEM model reproduces the experimental procedure, which is used to evaluate the performance of the NFP in terms of sensitivity by means of the simulated near-field distribution. The NFP-PCB has almost a flat response from 180 MHz to 6 GHz, with an almost perfect concordance between numerical and experimental S21 results. The numerical results show an average transmission loss of −27.9 dB by considering the flat response bandwidth, whereas the experimental one is −29.7 dB. Finally, the designed NFP is compared to two high-quality commercial probes in order to analyze its performance

Optimization and modeling of ESD protection devices

“Transient voltage suppressors (TVS) are used to protect ICs (integrated circuits) against overvoltage, ESD (Electrostatic Discharge), inductive load switching, and even lightning strikes. In this research, a transient behavior model framework for ESD protection devices is used for modelling four different types of TVS (non-snapback, snapback, spark gap like device and varistor). The System-Efficient ESD Design (SEED) methodology is utilized to strengthen the trust in the model framework by efficient simulation of ESD interaction of the off-chip ESD protection devices with the IC ESD protection device and associated measurement data. Improvements in the TVS transient response, accounting for conductivity modulation, voltage overshot at the snapback voltage, etc., are required to accurately model the ESD protection device. With this in mind, the unimproved model is presented for various ESD protection device where their transient behavior of single component can be fully described by a quasistatic very fast transmission line pulse (VF)-TLP. The improved model is validated within a sub-system consisting of an off-chip ESD protection device, an IC on-chip protection and a PCB trace in between. Multiple solutions to avoid convergence issues are also proposed for effective simulation”--Abstract, page iv

Contactless, high resolution characterization of current and voltage waveforms within high power communication amplifiers

Characterisation of high-power communications-based amplifiers (PAs) has generated many thousands of research papers and much of this work assumes the transistors at the heart of these (PAs) to be a ‘large’ holistic entity. Given that high-power communications-based transistors are made up of multiple, parallel transistors on a single substrate, it is this intermediate scale range, within the periphery of the device, but much larger than the geometrical scale of the epitaxy and the lithography, that requires deeper investigation. Raman-based thermography may add a dimension of spatially varying heat dissipation but ‘lifting the bonnet’ of the transistor and making internal contactless measurements of current and voltage is the only way to fully account for the myriads of parasitic effects that have been observed by countless researchers. To date, however, very little research has been conducted on quantifying the individual spatial voltages within the transistor in order to fully characterise it. Miniaturised contactless current and voltage probes are theorised, designed, characterised and optimised in this thesis to deliver a robust and reliable means of transistor characterisation at these internal spatial dimensions. The contactless voltage probe presented in this work has a spatial resolution four times finer than the previously reported voltage probe, with a useful bandwidth up to 7 GHz and a controllable passive gain up to 20 dB at the desired operating frequency. The pinnacle of this thesis delivers a novel shielded contactless current probe, capable of high-resolution scanning, culminating in a ‘quasi-calibrated’ measurement of the distributed currents within a multi-finger LDMOS transistor operating at high power and high frequency. The spatial resolution of this shielded contactless current probe is 62.5 μm with 22.7 dB average rejection ratio to the electric field, and it has a broad bandwidth up to 9 GHz. To date, this type of contactless current measurement has not been reported elsewhere

A multiple scattering method to study the cable harness inside a vehicle shell

This dissertation contains three major parts. In the first part, a generalized multi-conductor transmission line (GMTL) method is proposed to model a cable harness. In the GMTL method, all wires of the cable harness take the infinity as the reference. In such a way, the GMTL method takes into account not only the transmission-line mode but also the antenna-mode current on the cable harness. Further, by employing the GMTL method and the mixed-potential integral equations (MPIE) method in a multiple scattering (MS) procedure, it enables an efficient and accurate approach to evaluate the current distribution on a cable harness with a nearby metal surface. Notice that the cable harness is not grounded to the metal surface in this part. In the second part, a hybrid algorithm called the generalized multiple scattering (GMS) method is proposed to efficiently and accurately calculate the current distribution on a cable harness which has several ground connections to a nearby metal surface. This is a simplified case to mimic a cable harness routed inside a vehicle shell. The GMS method uses the GMTL method for the cable harness part and the MPIE method for the rest of the structure including the metal surface and the grounding wires. Neither the GMTL nor the MPIE method alone takes into account the mutual interactions between the cable harness and the rest of the structure. Therefore, an iterative scheme is arranged in the GMS method to compensate the abovementioned interactions. These interactions occur via not only field couplings, but also current conducting through the grounding points on the cable harness. In the third part, the GMTL method is reformulated to cover both straight and bent cable harnesses. The extraction of the per-unit-length inductance and capacitance is also simplified compared to the extraction method described in the first part. Besides, the steepest descent method is utilized to compute the radiation of a cable harness based on the obtained current through the GMTL method. The capability and limitations of the GMTL method are also carefully examined --Abstract, page iv

High efficiency planar microwave antennas assembled using millimetre thick micromachine polymer structures

Communication systems at microwave and millimetre wave regimes require compact broadband high gain antenna devices for a variety of applications, ranging from simple telemetry antennas to sophisticated radar systems. High performance can usually be achieved by fabricating the antenna device onto a substrate with low dielectric constant or recently through micromachining techniques. This thesis presents the design, fabrication, assembly and characterisation of microstrip and CPW fed micromachined aperture coupled single and stacked patch antenna devices. It was found that the micromachining approach can be employed to achieve a low dielectric constant region under the patch which results in suppression of surface waves and hence increasing radiation efficiency and bandwidth. A micromachining method that employs photolithography and metal deposition techniques was developed to produce high efficiency antenna devices. The method is compatible with integration of CMOS chips and filters onto a common substrate. Micromachined polymer rims (SU8 photoresist) was used to create millimetre thick air gaps between the patch and the substrate. The effect of the substrate materials and the dimensions of the SU8 polymer rims on the performance of the antenna devices were studied by numerical simulation using Ansoft HFSS electromagnetic field simulation package. The antenna structures were fabricated in layers and assembled by bonding the micromachined polymer spacers together. Low cost materials like SU8, polyimide and liquid crystal polymer films were used for fabrication and assembly of the antenna devices. A perfect patch antenna device is introduced by replacing the substrate of a conventional patch antenna device with air in order to compare with the micromachined antenna devices. The best antenna parameters for a perfect patch antenna device with air as a substrate medium are ~20% for bandwidth and 9.75 dBi for antenna gain with a radiation efficiency of 99.8%. In comparison, the best antenna gain for the simple micromachined patch antenna device was determined to be ~8.6 dBi. The bandwidth was ~20 % for a microstrip fed device with a single patch; it was ~40 % for stacked patch devices. The best bandwidth and gain of 6.58 GHz (50.5%) and 11.2 dBi were obtained for a micromachined sub-array antenna device. The simulation results show that the efficiency of the antenna devices is above 95 %. Finally, a novel high gain planar antenna using a frequency selective surface (FSS) was studied for operation at ~60 GHz frequency. The simulation results show that the novel antenna device has a substantial directivity of around 25 dBi that is required for the emerging WLAN communications at the 60 GHz frequency band

Microwave Sensing and Imaging

In recent years, microwave sensing and imaging have acquired an ever-growing importance in several applicative fields, such as non-destructive evaluations in industry and civil engineering, subsurface prospection, security, and biomedical imaging. Indeed, microwave techniques allow, in principle, for information to be obtained directly regarding the physical parameters of the inspected targets (dielectric properties, shape, etc.) by using safe electromagnetic radiations and cost-effective systems. Consequently, a great deal of research activity has recently been devoted to the development of efficient/reliable measurement systems, which are effective data processing algorithms that can be used to solve the underlying electromagnetic inverse scattering problem, and efficient forward solvers to model electromagnetic interactions. Within this framework, this Special Issue aims to provide some insights into recent microwave sensing and imaging systems and techniques