Microstrip Traces Research Articles

Microwave Atom Chip Design

We present a toolbox of microstrip building blocks for microwave atom chips geared towards trapped atom interferometry. Transverse trapping potentials based on the AC Zeeman (ACZ) effect can be formed from the combined microwave magnetic near fields of a pair or a triplet of parallel microstrip transmission lines. Axial confinement can be provided by a microwave lattice (standing wave) along the microstrip traces. Microwave fields provide additional parameters for dynamically adjusting ACZ potentials: detuning of the applied frequency to select atomic transitions and local polarization controlled by the relative phase in multiple microwave currents. Multiple ACZ traps and potentials, operating at different frequencies, can be targeted to different spin states simultaneously, thus enabling spin-specific manipulation of atoms and spin-dependent trapped atom interferometry.

Inclusive Modeling and Digital Compensation for Coupling Impairments of High-Speed Coupled Electrical Microstrip Traces in 100G OOK and PAM4 Data Center Connections

Pluggable transceiver modules become the preferable form factor in data centers connectivity due to the lower power consumption and smaller size, which allows high port density. In such small form factors, the optical components may be packaged separately from the electronic blocks. This introduces a new challenge for transmission of ultra-broadband signal over high-speed coupled printed analog traces, as the coupling impairments are enhanced dramatically. Here, an extended model of coupling impairments of coupled microstrip traces in optical fiber communication systems is proposed. This model consists of an accurate formulation of the frequency dependency, which is shown to be critical in the transmission of ultra-broadband signals. In addition, a comparison is presented to standard practice coupling models that are currently being used for crosstalk cancellation techniques in sub-10G systems or very short traces. Based on the inclusive coupling model, novel coupling compensation techniques are proposed and are compared with the classical ones. Comprehensive analysis, which is verified by Monte-Carlo simulation, reveals that the newly introduces coupling compensation technique significantly outperforms the existing crosstalk compensation solutions, for 25G transmission and beyond, thus, longer coupled traces are supported. The new approach is based on symbol-spaced sampling and reduced-complexity digital signal processing. It is shown in the case of 100G PAM4 transmission, based on commercially available 25G components, the newly proposed compensation technique supports long microstrip traces of more than 15 cm, while maintaining 10 -3 pre-forward error correction (pre-FEC) bit error rate (BER).

Analytical Solution for Maximum Differential-Mode Radiated Emissions of Microstrip Trace

In this paper, a novel analytical solution was presented for estimating the maximum differential-mode (DM) radiated emission from electrically long PCB traces using transmission-line theory, travelling wave antenna, and far-field magnetic vector potential. The analytical solution was simplified for matched load in which only forward travelling wave was considered. Additionally, a simple expression for predicting maximum DM-RE from electrically short traces was obtained using proper simplifications. The results from the proposed analytical model were then compared to the results obtained from 3-D HFSS full-wave simulation and the measurement performed in a semianechoic chamber. Good agreements within ±3 dB were obtained over a wide range of frequency.

Sensitive and Efficient RF Harvesting Supply for Batteryless Backscatter Sensor Networks

This work presents an efficient and high-sensitivity radio frequency (RF) energy harvesting supply. The harvester consists of a single-series circuit with one double diode on a low-cost, lossy FR-4 substrate, despite the fact that losses decrease RF harvesting efficiency. The design targeted minimum reflection coefficient and maximum rectification efficiency, taking into account not only the impedance matching network, but also the rectifier microstrip trace dimensions and the load. The simulated and measured rectenna efficiency was 28.4% for $-\hbox{20-dBm}$ power input. In order to increase sensitivity, i.e., ability to harvest energy and operate at low power density, rectennas were connected in series configuration (voltage summing), forming rectenna arrays. The proposed RF harvesting system ability was tested at various input power levels, various sizes of rectenna arrays, with or without a commercial boost converter, allowing operation at RF power density as low as 0.0139 $\mu \hbox{W/cm}^{2}$ . It is emphasized that the boost converter, whenever used, was self-started, without any additional external energy. The system was tested in supplying a scatter radio sensor, showing experimentally the effect of input power density on the operational cold start duration and duty cycle of the sensor.

Spectrally Fragmented Electrical Dispersion Compensation for High-Speed Microstrip Traces in Data Centers Connections

The frequency-dependent dispersion impairment of high-speed printed analog traces in next-generation pluggable modules is studied. This frequency dependence is considered for the first time in optical fiber communication systems. Transmission of ultra-broadband electrical signals over such traces dramatically enhances the frequency-dependent dispersion effect. Here, for the first time, an extended model of the ultrabroadband signal transmission that includes this frequency-dependent dispersion effect of the printed analog traces is proposed. Additionally, a novel approach to compensate for this frequency-dependent dispersion impairment is introduced. Inclusive analysis reveals that a significant performance improvement of up to 4 dB is achieved by using the proposed symbol-spaced sampling and reduced-complexity digital signal processing technique.

A Frequency Tunable High Sensitivity H-Field Probe Using Varactor Diodes and Parasitic Inductance

A frequency-tunable resonant magnetic field probe is designed for near-field scanning applications for the radio frequency interference studies. Tunable resonance is achieved by using a varactor diode providing the required capacitance and the parasitic inductance of a magnetic loop (i.e., a parallel LC circuit). An equivalent circuit model for the probe is described, analyzed, and used for designing the probe for achieving maximum sensitivity. The resonance frequency of the designed probe is tunable in the frequency range of 900–2260 MHz that covers multiple radio bands, such as the GSM900, UMTS, and GPS bands. The sensitivity of the probe at the resonance frequency is about 7–9 dB higher than that of an equivalently sized broadband magnetic field probe throughout the tunable frequency range. The measured frequency response and sensitivity over a microstrip trace using the fabricated probe shows good agreement with the simulated results of the equivalent circuit model and the full-wave simulation model.

Determination of the complex permittivity of microfluids in a microstrip geometry

ABSTRACTA novel configuration for estimating the broadband permittivity of small fluid volumes is presented using 2‐port S‐parameters. Unlike previous demonstrations in coplanar technology, our proposal places the analyte under a microstrip trace where better field overlap with the fluid improves device sensitivity. Fluid parameter estimates based on simulation are presented. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2604–2608, 2014

A FLEXIBLE BROADBAND ANTENNA AND TRANSMISSION LINE NETWORK FOR A WEARABLE MICROWAVE BREAST CANCER DETECTION SYSTEM

First, we report on the design, simulation and measurement of a 2-4 GHz conformable antenna optimized for skin contact and implemented on a flexible printed circuit for integration into a wearable device. Second, we experimentally verify the suitability of appropriately long (∼ 10 cm) microstrip traces for the wearable system signal distribution network, which features varying radii of curvature. Consequently, the contribution of the here reported work is two-fold. First, the experimental results obtained both with breast phantoms and on-body measurements, demonstrate a return loss below −10 dB in the desired frequency band. Phantom results also show a through-breast transmission coefficient of above −40 dB at the centre frequency of 3 GHz. Second, and essential for signal integrity in our target application, the results show that the longitudinal curvature of such a microstrip does not increase transmission line losses.

A Magnetic-Field Resonant Probe With Enhanced Sensitivity for RF Interference Applications

High-sensitive field probes are highly desirable for radio-frequency (RF) interference studies, where ultralow noise levels are of interest. By incorporating an LC resonant circuit in a differential-loop probe, together with a Marchand balun, a magnetic-field probe with enhanced sensitivity is developed. Its equivalent circuit model and design methodology are established. The design is validated by measurements. The measured relative sensitivity in terms of |S21| of the proposed probe increases by approximately 8.63 dB at the resonant frequency of 1.575 GHz compared to that of a conventional design. The advantage of the proposed probe is validated through its application in the measurement of a microstrip trace and a real-world cell phone design.

An Effective Method of Probe Calibration in Phase-Resolved Near-Field Scanning for EMI Application

Near-field scanning can be used to determine the far-field emissions of electronic devices. In general, this requires phase-resolved electric and magnetic near-field data. To capture a broad frequency range relatively quickly, a multichannel oscilloscope can be used for data capture. The phase relationship of the fields between different space points and between the electric and the magnetic field needs to be known. Consequently, it is required to determine the complex-valued probe factor (PF) of the probe, cable, and amplifier chain. This paper presents a fast and efficient calibration method which uses the same setup and instruments during calibration and measurement, and it allows for easy and economical integration of the calibration hardware and software into the scanning system. Known fields are created by a microstrip trace driven with a comb generator. By referencing measured data to this known field, the PF is obtained over a broad frequency range by capturing one time-domain waveform.

BROADBAND ASYMMETRICAL MULTI-SECTION COUPLED LINE WILKINSON POWER DIVIDER WITH UNEQUAL POWER DIVIDING RATIO

The uniform asymmetrical microstrip parallel coupled line is used to design the multi-section unequal Wilkinson power divider with high dividing ratio. The main objective of the paper is to increase the trace widths in order to facilitate the construction of the power divider with the conventional photolithography method. The separated microstrip lines in the conventional Wilkinson power divider are replaced with the uniform asymmetrical parallel coupled lines. An even-odd mode analysis is used to calculate characteristic impedances and then the per-unit-length capacitance and inductance parameter matrix are used to calculate the physical dimension of the power divider. To clarify the advantages of this method, two three-section Wilkinson power divider with an unequal power-division ratio of 1 : 2:5 are designed and fabricated and measured, one in the proposed conflguration and the other in the conventional conflguration. The simulation and the measurement results show that not only the specifled design goals are achieved, but also all the microstrip traces can be easily implemented in the proposed power divider.

Prediction of Radiated Emissions Using Near-Field Measurements

A procedure is developed to predict electromagnetic interference from electronic products using near-field scan data. Measured near-field data are used to define equivalent electric and magnetic current sources characterizing the electromagnetic emissions from an electronic circuit. Reconciliation of the equivalent sources is performed to allow the sources to be accurately applied within full-wave numerical modeling tools like finite-difference time domain (FDTD). Results show that the radiated fields must typically be represented by both electric and magnetic current sources if scattering and multiple-reflections from nearby objects are to be taken into account. The accuracy of the approach is demonstrated by predicting the fields generated by a microstrip trace within and outside of a slotted enclosure, and by predicting the fields generated by the microstrip trace close to a long wire. Values predicted from near-field scan data match those from full-wave simulations or measurements within 6 dB.

Analytical Solutions for the Radiated Emission of Parallel Microstrip Traces

A closed-form expression of the unintentional electromagnetic radiation of parallel microstrip traces is proposed. Based on transmission line theory, far-field Green's function, and concept of array factor in antenna theory, analytical solutions for the electric field radiated from a pair of parallel microstrip lines are developed. Depending on the printed circuit board material, dimension parameters, and termination impedances, the frequency and angular responses of far-field radiated emission on the upper half-plane can be analyzed by the presented method. The differential- and common-mode radiated emission solutions are validated by a full-wave simulator and test board measurements in a full-anechoic chamber.

Using Radiating Near Field Region to Sample Radiation of Microstrip Traces for Far Field Prediction by Genetic Algorithms

Regarding a microstrip trace above an infinite ground plane, near field and far field regions are clearly defined for near field-far field conversion. Near field radiation data sampled in radiating near field and reactive near field regions are compared for far field prediction. An equivalent set of dipoles are searched by genetic algorithms to approximate the near field data, and then predict the far field. Magnetic near field peak magnitudes are obtained by a method-of-moments simulation, and far field prediction is compared with simulated data.

Full-Wave Solver for Microstrip Trace and Through-Hole Via in Layered Media

This paper reports major improvements to a 3-D full wave solver for a microstrip line and through-hole via in layered media. The interior layer problem, consisting of vias between two reference planes, is solved using the Foldy-Lax multiple scattering equations. The exterior layer problem is solved using the method of moments (MoM) with the layered media Green's functions. The exterior layer and interior layer problems are combined to obtain the S-parameters of the trace and through-hole via. A fast approach for calculating the layered-medium Green's functions using the numerical modified steepest descent path method is utilized. The Green's functions require milliseconds to compute per point. Schemes for efficiently computing image contributions for the static portion of the mixed potential Green's function are also implemented to solve the neighboring or self-RWG (basis function) interaction in the MoM problem. To validate the accuracy of the solution, extensive comparison with Ansoft's HFSS versions 9 and 11 for different pad sizes and antipad sizes are presented. The CPU per frequency is also tabulated to demonstrate the speed of the approach in this paper.

Derivation of a Closed-Form Approximate Expression for the Self-Capacitance of a Printed Circuit Board Trace

The electric fields that couple traces on printed circuit boards to attached cables can generate common-mode currents that result in significant radiated emissions. Previous work has shown that these radiated emissions can be estimated based on the self-capacitances of the microstrip structures on a board . In general, the determination of these self-capacitances must be done numerically using three-dimensional static modeling software. In this paper, an approximate closed-form expression for the self-capacitance of microstrip traces is derived. This expression can be used to estimate the voltage-driven common-mode emissions from boards with various microstrip trace geometries. The expression also provides insight relative to the microstrip parameters that have the greatest effect on radiated emissions.

Model for Estimating Radiated Emissions From a Printed Circuit Board With Attached Cables Due to Voltage-Driven Sources

Common-mode currents induced on cables attached to printed circuit boards (PCBs) can be a significant source of unintentional radiated emissions. This paper develops a model for estimating the amount of common-mode cable current that can be induced by the signal voltage on microstrip trace structures or heatsinks on a PCB. The model employs static electric field solvers or closed-form expressions to estimate the effective self-capacitances of the board, trace, and/or heatsink. These capacitances are then used to determine the amplitude of an equivalent common-mode voltage source that drives the attached cables. The model shows that these voltage-driven common-mode cable currents are relatively independent of the cable parameters and the trace or heatsink location when the PCB is small relative to the cable length and to a wavelength.

Traces in Proximity to Gaps in Return Planes

Coupling between circuitry on printed circuit boards can be mitigated by a variety of well-known techniques. One such technique is to isolate circuitry in different areas of the printed circuit board by strategically placing a gap in the signal return plane. However, this technique is only effective at reducing common-impedance coupling, which is generally not a significant coupling mechanism at frequencies above 1 MHz. This paper investigates the effect of a gap located between and parallel to adjacent microstrip traces. The effect of the gap on the mutual inductance and mutual capacitance is evaluated. Laboratory measurements and numerical simulations show that gaps in the return plane are ineffective at reducing inductive and capacitive crosstalk in most configurations, and in some cases they increase the mutual coupling between printed circuit board traces.

The impact of a nonideal return path on differential signal integrity

Printed circuit board transmission lines propagating high-speed digital signals are susceptible to nonideal return paths which may affect signal integrity. In an attempt to clarify this complex issue, this paper presents a study of differential signal integrity issues for the familiar situation in which two coupled microstrip traces are in close proximity to a common reference plane. Differential signaling on coupled microstrip lines and stripline configurations are investigated. Finite-difference time domain simulations are used to demonstrate the impact a nonideal return path can have on differential signal integrity.