Kuangda Wang

Balanced Substrate Integrated Waveguide Filter

A novel balanced filter realized in the form of substrate integrated waveguide (SIW) is proposed and studied in this paper. Based on the inherently horizontal and vertical symmetry of the SIW, this filter presents inherently high-performance balanced property with advantages of no identical pair requirement, being free from the limitation of symmetrical topology, easy and flexible design, high common-mode (CM) suppression, and robust CM suppression when comparing with conventional counterparts. Several prototypes are designed, fabricated, and measured to verify the expected properties.

Accurate Characterization of Attenuation Constants of Substrate Integrated Waveguide Using Resonator Method

A novel resonator method is presented to extract the attenuation constants of the substrate integrated waveguide (SIW) transmission lines, providing an alternative way to investigate the propagation properties of SIW. The losses of SIW transmission line and cavity resonator have been investigated with theoretical analysis. Then a formula is derived for establishing the relationship between the attenuation constant of the SIW transmission line and the unloaded Q-factor of SIW cavity resonator at its resonant frequency. Thus, the attenuation constant of SIW transmission line can be extracted using SIW cavity resonator. Good agreement between the resonator method and Thru-Line (TL) method has been achieved in both full-wave simulation and experimental results. Besides, good robustness of the resonator method has been demonstrated, suggesting it is a promising technique for investigation of the propagation properties of SIW.

Development of a Large¿Signal¿Network¿Analyzer Round¿Robin Artifact

This article presents the design and measurement results of the contest-winning LSNA round-robin artifact. The proposed two-port device was designed with respect to the objective of complementing an upcoming LSNA international round-robin between measurement facilities. The proposed device consists of three parts, a nonlinear circuit generating the required five harmonics based on a monolithic InGaP HBT MMIC amplifier, an output circuits based on a wideband amplifier and attenuator, which role is to amplify the signal generated by the nonlinear device and isolate the nonlinear device from the output load, and finally, a stabilized dc supply circuit based on voltage regulator chips typically used for instrumentation. To avoid noise interfering with the measurement, EMI considerations were taken into account. The overall device is shielded within a casing composed of three cavities to isolate each circuit. This casing also helps as a heat sink to stabilize the artifact in temperature. The proposed device is validated by measurements. Thanks to a high output signal level at the fundamental and harmonics, a high-value attenuator can be used to efficiently isolate the artifact from the load and still obtain a sufficiently high output signal for accurate measurement with an LSNA.

Slow-Wave Effect of Substrate Integrated Waveguide Patterned With Microstrip Polyline

A class of slow-wave substrate integrated waveguide (SIW) structures patterned with microstrip polyline is presented, theoretically studied, and experimentally validated, which demonstrates some interesting slow-wave propagation effects. The slow-wave SIW (SW-SIW) enables the size reduction of a physically large circuit without sacrificing its performance. A size reduction of 40% of the lateral dimension is achieved with reference to that of the conventional SIW counterpart at the same cutoff frequency. Meanwhile, the phase velocity of the waveguide is also reduced by 40%, resulting in a smaller longitudinal dimension for a given electrical length. Both lateral and longitudinal effects give rise to a total size reduction, largely extending the operation range of SIW structures in the low-frequency region, which has often been restrained by a physical dimension-related cutoff frequency. Also, a transmission line-based two-dimensional (2-D) equivalent-circuit model is proposed and deployed for the modeling and analysis of the slow-wave mechanism. The results from the equivalent-circuit model agrees very well with that from the full-wave simulations. Furthermore, a broadband microstrip to SW-SIW taper with good return loss is designed for measurement verification. Using the proposed SW-SIW structure, the size of conventional SIW-based microwave circuits such as power splitters, couplers, and filters can be further reduced in addition to the existing size-reduction techniques.

Multiharmonic Generator for Large-Signal-Network-Analyzer Verification

Since S-parameters were first used to describe linear microwave circuits in the 1960s, circuit designers, software developers, and instrument manufacturers have gradually come to an agreement on this blackbox representation, resulting in significant advancements in modeling, simulation, and measurement. As a mathematical language of high-frequency signal transmission and scattering, S-parameter stands for a unified form of the linear characteristics of microwave networks in the frequency domain. Subsequently, the vector network analyzer (VNA) was invented as the principal instrument to measure S-parameters and characterize the linear behavior of devices and components, including small-signal active circuits.

A Multitarget Active Backscattering 2-D Positioning System With Superresolution Time Series Post-Processing Technique

An active backscattering 2-D positioning system is studied and demonstrated in this paper. The hardware is based on an investigated principle of switched injection phase locking for wireless ranging. A new post-processing technique and a system modeling for multitarget time-of-arrival (TOA) and direction-of-arrival (DOA) estimations are proposed and studied. The technique features a joint singular value decomposition-based ESPRIT algorithm and a matrix diagonalization technique using Moore–Penrose pseudoinverse for model order estimation as well as the TOA/DOA extraction. They make use of the shift invariant property of a backscattered signal in the time-domain. The accuracy and resolution are studied and are shown to be superior to those of the conventional frequency-domain technique using a fast Fourier transform (FFT). Moreover, the proposed algorithms take full advantage of the chirp bandwidth and allow all the targets to operate at the same modulation frequency and arbitrary carrier frequency. These merits avoid a commonly exercised compromise of the FFT method among the resolution, target quantity, signal-to-noise ratio, and other critical specifications. The system is simulated, and the demonstrator is constructed for experimental verifications in both indoor and outdoor environments, with a bandwidth of 600 MHz centered at 5.6 GHz.

Liquid crystal enabled substrate integrated waveguide variable phase shifter for millimeter-wave application at 60ghz and beyond

A variable phase shifter based on substrate integrated waveguide (SIW) and liquid crystal (LC) is proposed and demonstrated in 57-65GHz. The permittivity of nematic LCs can be made variable by applying various intensities of electric or magnetic fields. By partially replacing the dielectric substrate of SIW with standard LC (E7) and embedding an electric bias structure, an electronically tunable phase shifter is created. The phase shifter can be continuously tuned up to 300 ° with an insertion loss from 4.5dB to 8.5dB. Since alternative LC materials having a much lower loss tangent are already available, the results obtained from this experimental demonstration illuminate an emerging class of high-performance tunable millimeter-wave devices that can be seamlessly integrated in SIW platforms.

Harmonic feedback-loop oscillator for pulling effect reduction and improved phase noise

A diplexer-based harmonic feedback-loop oscillator concept is presented and demonstrated at 5.8GHz. Without additional complexity, the diplexer together with an RF amplifier creates isolation between nonlinear feedback-loop dynamics and second harmonic signal component that is directed to the output. As a result, the load pulling effect is reduced as well as the phase noise performance is improved with reference to its fundamental feedback-loop counterpart. Load-pull measured results (VSWR ≤ 9) are observed follows: 1) load dependent frequency drift is significantly reduced from -19⁰/₀₀~15⁰/₀₀ to -0.75⁰/₀₀~1.06⁰/₀₀; 2) phase noise at 1MHz offset is improved by 15dB; and 3) output power is slightly affected only.