Common-mode noise reduction schemes for weakly coupled differential serpentine delay microstrip lines

This paper proposes design schemes to reduce the common mode noise from weakly coupled differential serpentine delay microstrip lines (DSDMLs). The proposed approach is twofold: we leverage strongly coupled vertical-turn-coupled traces (VTCTs) instead of weakly coupled VTCTs (conventional pattern) and add guard traces. Time- and frequency-domain analyses of the proposed schemes for reducing the common-mode noise are performed by studying the transmission waveform and the differential-to-common mode conversion using the circuit solver HSPICE and the 3-D full-wave simulator HFSS, respectively. Compared to the conventional design of the weakly coupled DSDMLs, the proposed solutions yield a reduction of about 54% of the peak-to-peak amplitude of the common-mode noise, while the differential impedance remains matched along the complete length of the DSDML. Moreover, the range of frequencies, over which the magnitude of the differential-to-common mode conversion is now significantly reduced, is very wide, i.e. about 0.3-10 GHz. Furthermore, the differential insertion and reflection loss introduced by the newly proposed designs are almost the same as the ones achieved by using the conventional design. Finally, a favorable comparison between simulated and measured results confirms the excellent common-mode noise reduction performance of the proposed schemes

Non Contact Test Points - A high frequency measurement technique for printed circuit boards

A rising problem within electronics today is that, since the frequencies have increased dramatically, it is now very difficult to measure signals. If a traditional probe is used, then the direct contact will destroy the signal. The general idea behind this master thesis project is to make use of the crosstalk between transmission lines to create non contact test points. This thesis aims to evaluate different designs, in order to optimize the crosstalk, and also make use of signal processing to recover the original signal. Firstly, the problem was tackled with simulations and the results were analyzed in an attempt to optimize the design. Secondly, an actual circuit board was produced and the process was tested in reality. It turned out that the idea of non contact test points was solid, and it is shown in the report that good measurements can be acquired with little effect upon the original signal

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

Adaptive transient solution of nonuniform multiconductor transmission lines using wavelets

Abstract—This paper presents a highly adaptive algorithm for the transient simulation of nonuniform interconnects loaded with arbitrary nonlinear and dynamic terminations. The discretization of the governing equations is obtained through a weak formula-tion using biorthogonal wavelet bases as trial and test functions. It is shown how the multiresolution properties of wavelets lead to very sparse approximations of the voltages and currents in typical transient analyzes. A simple yet effective time–space adaptive al-gorithm capable of selecting the minimal number of unknowns at each time iteration is described. Numerical results show the high degree of adaptivity of the proposed scheme. Index Terms—Electromagnetic (EM) transient analysis, multi-conductor transmission lines (TLs), wavelet transforms. I

Scattering parameters characterization of periodically nonuniform transmission lines with a perturbative technique

In this article, a novel procedure for the frequency-domain solution of nonuniform transmission lines (NUTLs) is presented. The procedure is based on a recently proposed perturbative technique, which is proven to be computationally more efficient than standard solution approaches, which are based on line subdivision into uniform cascaded sections. With respect to the original perturbation technique, the procedure proposed here offers more flexibility, as it provides a representation of the NUTL under analysis in terms of S and/or T parameters at its ports. Moreover, it retains the same prediction accuracy at the price of a slight increase in computational burden, which can be mitigated anyway through parallel computing. Furthermore, even without ad hoc (parallel) implementations, the proposed procedure outperforms other approaches to solve differential lines with partially or fully repetitive geometries. Namely, it assures accurate prediction of output quantities with reduced simulation time. This is proven by three application examples, namely, two differential trapezoidal tabbed lines (one with interdigital tabs and one with facing tabs), and a differential microstrip line with a varying common-mode (CM) impedance (as such reducing CM noise). Comparison with full-wave simulations allows assessing the prediction accuracy of the proposed procedure. Comparison with the aforementioned transmission-line-based solutions allows appreciating the enhanced computational efficiency

On-detector electronics for high speed data transport, control and power distribution for the LHCb VELO and ATLAS Pixel Upgrades

The Large Hadron Collider (LHC) will see an upgrade to higher luminosity to widen the scope of study of particle physics and this will be a major upgrade of the LHC. The LHC collides protons at an energy of 13 TeV in order to study the fundamental components of matter and the forces that bind them together. The High-Luminosity Large Hadron Collider (HL-LHC) will enter service after 2025, increasing the volume of the data for analysis by a factor of 10. The phenomena that physicists are looking for have a very low probability of occurring and this is why a very large amount of data is needed to detect them. Vertexing and tracking sub-detectors for these High Energy Physics (HEP) experiments deliver very high data rates that require multi-gigabit transmission links. Commercial solutions such as optical transmission or wire cabling are investigated, however, due to high radiation environments and low radiation length requirements, electrical transmission with low mass custom designs have to be considered. Designing transmission lines with this requirement does pose a challenge and optical data transmission is used when space and radiation limits allow. The increase in luminosity will produce more data making it possible to study the phenomena in more detail by increasing the number of collisions by a factor of between five and seven. The increase in data will require an enhanced readout system and related electronics to be able to transmit and read out the data for further processing. At the same time powering systems need to be looked at to understand cost effcient and reliable techniques to be able to power such electronics. The thesis focuses on the readout electronics of the LHCb Vertex Locator (known as the 'VELO') Upgrade and the ATLAS Inner Tracker (known as the 'ITk') Upgrade including design of some components of the sub-systems, testing for high-speed data signaling, powering schemes and analysis of PCB designs and scope for improvements. An introduction to the LHC and the four experiments that use its beam - ATLAS, CMS, ALICE and LHCb is outlined. The thesis work is focused on two of these detectors namely ATLAS (A Toroidal LHC ApparatuS) and LHCb (Large Hadron Collider beauty) and these are further explained and details of the sub-systems that make up these detectors are elaborated. Major differences to the upgrade of the experiments is explained highlighting the changes and the main challenges that would need to be addressed. The work on the On-detector electronics of the LHCb VELO Upgrade with details of the design requirements and implementations for the different components is described and test results are presented. Data tapes for carrying high speed data signals and control signals from the front-end chip to the Vacuum Feedthoough (VF) were designed and successfully tested to have a loss of < 10 dB at the Nyquist frequency of 2.5 GHz and a characteristic impedance of approximately 94 Ω which is within the 10% tolerance of 100 Ω for differential signals. Sensitivity to radiation damage as well as additional mass in the detector acceptance were some factors that motivated the design of the Opto Power board (OPB). In addition, there was a need to power the front-end ASICs but from outside the vacuum tank. The OPB was designed to meet these requirements in addition to be more easily accessible for repair and maintenance. The OPB is realised in an 8-layer stackup, with custom designed radiation hard ICs, and was designed for optical to electrical conversion of 20 high-speed data links at 5.12 Gb/s per link to be read by the Off-detector electronics. The board comprises 13 DC-DC converters for powering 12 ASICs, two front-end hybrids and the OPB itself with a total current supply of 26 A. The ATLAS experiment will implement the Inner Tracker (ITk) which is a new tracker to be installed during the major ATLAS Upgrade during Long Shutdown 3. The work on the ATLAS ITK addresses two topics; a novel pixel powering scheme adopting layout techniques for high-speed design. A serial powering scheme was evaluated to be an optimal option and this scheme was tested to understand its scope and implementation in the pixel endcap design and results are presented. A study to understand the existing Crescent Tape PCB layout and techniques to improve the design for high-speed data transmission was evaluated. Methods for analysing high-speed data using S-parameters and eye diagrams, sources of signal degradation and mitigation techniques, are detailed. The laboratory test setup for high-speed measurements with the equipments used is also explained