C.P. Wen

Bio: C.P. Wen is an academic researcher from Princeton University. The author has contributed to research in topics: Microstrip & Coplanar waveguide. The author has an hindex of 2, co-authored 2 publications receiving 990 citations.

Coplanar Waveguide, a Surface Strip Transmission Line Suitable for Nonreciprocal Gyromagnetic Device Applications

Abstract: A coplanar waveguide consists of a strip of thin metallic film on the surface of a dielectric slab with two ground electrodes running adjacent and parallel to the strip. This novel transmission line readily lends itself to nonreciprocal magnetic device applications because of the built-in circularly polarized magnetic vector at the air-dielectric boundary between the conductors. Practical applications of the coplanar waveguide have been experimentally demonstrated by measurements on resonant isolators and differential phase shifters fabricated on low-loss dielectric substrates with high dielectric constants. Calculations have been made for the characteristic impedance, phase velocity, and ripper bound of attenuation of a transmission line whose electrodes are all on one side of a dielectric substrate. These calculations are in good agreement with preliminary experimental results. The coplanar configuration of the transmission system not only permits easy shunt connection of external elements in hybrid integrated circuits, but also adapts well to the fabrication of monolithic integrated systems. Low-loss dielectric substrates with high dielectric constants may be employed to reduce the longitudinal dimension of the integrated circuits because the characteristic impedance of the coplanar waveguide is relatively independent of the substrate thickness; this may be of vital importance for Iow-frequency integrated microwave systems.

Coplanar-Waveguide Directional Couplers

Abstract: Design information for coplanar-waveguide directional couplers has been calculated using quasi-static zeroth-order approximations. Experimental results on a 10-dB directional coupler designed from these calculations have shown reasonably good agreement with predictions. The smaller difference in even- and odd-mode velocity in a coplanar-waveguide directional coupler leads to better directivity and better performance than a microstrip directional coupler.

Correlation Between Reverse Leakage Current and Electric Field Spreading in GaN Vertical SBD With High-Energy Ion Implanted Guard Rings

Abstract: This work focuses on the bias-dependent reverse leakage current and carrier depletion process of vertical gallium nitride (GaN)-on-GaN Schottky barrier diodes (SBDs) with fluorine ion-implanted guard rings (GRs). The reverse leakage characteristics in the vertical GaN SBD with GRs sequentially go through ohmic conduction, thermionic field emission (TFE), and space charge limited conduction (SCLC) model as the reverse bias increases gradually. Once the traps in the implanted termination region are fully ionized, the device will undergo large leakage current at high biases. Compared with infinite area ion implanted edge termination (ET), ion-implanted GR can effectively reduce the leakage current at low biases. In addition, there are kinks in the reverse current–voltage curves, which proved to be related to the electric field spreading effect of individual GR. Based on the analysis of reverse leakage current, the electric field modulation mechanism of ion-implanted GRs is reviewed.

GaN-on-Si Quasi-Vertical p-n Diode With Junction Termination Extension Based on Hydrogen Plasma Treatment and Diffusion

Abstract: Utilizing hydrogen plasma treatment and controlled diffusion, a junction termination extension (JTE) structure for vertical gallium nitride (GaN) p-n diode with gradient hole density (GHD) is spontaneously formed based on the selective area partial passivation of Mg acceptors with hydrogen. The reverse bias for the quasi-vertical GaN-on-Si p-n diodes to reach a leakage current of 1 A/cm2 was boosted from 631 to 1100 V. In addition, the fabricated diode possessed a superior rectifying behavior with an ON/OFF-current ratio of $10^{{12}}$ , a specific differential ON-resistance of 0.75 $\text{m}\sf \Omega \cdot $ cm2.

Coplanar waveguide circuits, components, and systems

Abstract: Preface Introduction Conventional Coplanar Waveguide Conductor-Backed Coplanar Waveguide Coplanar Waveguide with Finite-Width Ground Planes Coplanar Waveguide Suspended Inside A Conducting Enclosure Coplanar Striplines Microshield Lines and Coupled Coplanar Waveguide Attenuation Characteristics of Conventional, Micromachined, and Superconducting Coplanar Waveguides Coplanar Waveguide Discontinuities and Circuit Elements Coplanar Waveguide Transitions Directional Couplers, Hybrids, and Magic-Ts Coplanar Waveguide Applications References Index

A uniplanar compact photonic-bandgap (UC-PBG) structure and its applications for microwave circuit

Abstract: This paper presents a novel photonic bandgap (PBG) structure for microwave integrated circuits. This new PBG structure is a two-dimensional square lattice with each element consisting of a metal pad and four connecting branches. Experimental results of a microstrip on a substrate with the PEG ground plane displays a broad stopband, as predicted by finite-difference time-domain simulations. Due to the slow-wave effect generated by this unique structure, the period of the PBG lattice is only 0.1/spl lambda//sub 0/ at the cutoff frequency, resulting in the most compact PEG lattice ever achieved. In the passband, the measured slow-wave factor (/spl beta//k/sub 0/) is 1.2-2.4 times higher and insertion loss is at the same level compared to a conventional 50-/spl Omega/ line. This uniplanar compact PBG (UC-PBG) structure can be built using standard planar fabrication techniques without any modification. Several application examples have also been demonstrated, including a nonleaky conductor-backed coplanar waveguide and a compact spurious-free bandpass filter. This UC-PBG structure should find wide applications for high-performance and compact circuit components in microwave and millimeter-wave integrated circuits.

Circuit quantum electrodynamics

Abstract: Quantum-mechanical effects at the macroscopic level were first explored in Josephson-junction-based superconducting circuits in the 1980s. In recent decades, the emergence of quantum information science has intensified research toward using these circuits as qubits in quantum information processors. The realization that superconducting qubits can be made to strongly and controllably interact with microwave photons, the quantized electromagnetic fields stored in superconducting circuits, led to the creation of the field of circuit quantum electrodynamics (QED), the topic of this review. While atomic cavity QED inspired many of the early developments of circuit QED, the latter has now become an independent and thriving field of research in its own right. Circuit QED allows the study and control of light-matter interaction at the quantum level in unprecedented detail. It also plays an essential role in all current approaches to gate-based digital quantum information processing with superconducting circuits. In addition, circuit QED provides a framework for the study of hybrid quantum systems, such as quantum dots, magnons, Rydberg atoms, surface acoustic waves, and mechanical systems interacting with microwave photons. Here the coherent coupling of superconducting qubits to microwave photons in high-quality oscillators focusing on the physics of the Jaynes-Cummings model, its dispersive limit, and the different regimes of light-matter interaction in this system are reviewed. Also discussed is coupling of superconducting circuits to their environment, which is necessary for coherent control and measurements in circuit QED, but which also invariably leads to decoherence. Dispersive qubit readout, a central ingredient in almost all circuit QED experiments, is also described. Following an introduction to these fundamental concepts that are at the heart of circuit QED, important use cases of these ideas in quantum information processing and in quantum optics are discussed. Circuit QED realizes a broad set of concepts that open up new possibilities for the study of quantum physics at the macro scale with superconducting circuits and applications to quantum information science in the widest sense.

Quasi-TEM description of MMIC coplanar lines including conductor-loss effects

Abstract: A quasi-TEM model of MMIC coplanar structures is presented. The elements of the distributed equivalent circuit are calculated by closed-form approximations and hence can easily be implemented into CAD packages. The effects of nonideal conductors are included as well as substrate loss and finite metallization thickness. The description holds for the entire quasi-TEM range, i.e. for typical MMIC geometries from DC to millimeter-wave frequencies. The validity of the model was checked by comparison to full-wave results. The errors for the effective dielectric constant and the characteristic impedance range below 5% for the attenuation typical values of 5-10% are found (maximum: 20%). >

Measurement of mortar permittivity during setting using a coplanar waveguide

Abstract: A sensor based on a coplanar waveguide structure was designed to perform non-destructive tests for material characterization in which the measurement can be done only on one side of the sample. The measurements were compared with the impedance of a capacitor filled with the same material. The permittivity and insertion loss of the sensor showed valuable information about the setting process of a mortar slab during the first 28 days of the hardening process, and a good correlation between both measurements was obtained, so the proposed setup can be useful for structural surveillance and moisture detection in civil structures.