This article reports on the design and practical development of RF co-designed MMIC components that exhibit the function of a bandpass filter and an RF isolator. They are based on cascaded non-reciprocal frequency-selective stages (NFSs), one-pole/two-transmission zero (TZ) multi-resonant stages, and impedance inverters. The combination of these components results in a two-port network that exhibits a nonreciprocal quasi-elliptic bandpass filter (NBPF) response in the forward direction and full RF signal cancellation in the reverse one. The operating principles of the NBPF are presented through various circuit-based design examples of low- and high-order configurations. For proof-of-concept demonstration purposes, NBPF prototypes were designed on an MMIC GaAs process and were experimentally validated at $X$ -band. They include a two-pole/two-TZ NBPF and a three-pole/four-TZ NBPF.

X -Band Quasi-Elliptic Non-Reciprocal Bandpass Filters (NBPFs)

In this article, we demonstrate a method for codesign of filtering matching networks for power amplifiers (PAs) with the desired frequency response, improved efficiency, and reduced footprint. The microwave transistor operates with high efficiency with a specific complex-impedance load, and this requires the development of a theory for filter matching network design with arbitrary complex-impedance ports. The formulation is first developed and then applied to a simple second-order filter and a fourth-order filter with cross couplings and transmission zeros and verified in the experiment. A single-stage high-efficiency 4.7-GHz, 4-W hybrid GaN filter-PA (FPA) within a sub-6-GHz 5G band is designed, built, and characterized. The port impedances are determined by load– and source–pull for an efficiency–power tradeoff. The measured performance shows a gain of 15 dB, PAE = 55% with 9% fractional bandwidth, and 10-dB rejection at 4.5 and 5 GHz. Comparison with a cascaded PA-filter circuit shows a 25% lower loss with the same rejection and a reduced footprint with the same rejection. A GaAs monolithic microwave integrated circuit (MMIC) FPA at 28 GHz (millimeter-wave 5G FR2 band) is also designed and measured with a second-order output matching filter, demonstrating 8-dB gain, 200 mW of output power, and PAE = 30% with a rejection of 8 dB at 26.5 and 29.6 GHz.

Power Amplifiers With Frequency-Selective Matching Networks

Natural gas pipeline leakage can cause serious financial losses to natural gas transportation and pose accidents to the environmental safety. Currently-used supervised learning methods heavily rely on sufficient pipeline failure historical data for their training. Therefore, we propose a novel detection approach based on unsupervised learning and stress perception for determining the leakage situation in pipelines. In this study, pipeline stress signals are first acquired based on residual magnetic effect. The relationship between residual magnetic and stress is built using improved sparrow search algorithm (ISSA) and extreme learning machine (ELM). Then, the Wasserstein generative adversarial network with gradient penalty (WGAN-GP) is deployed to learn suitable features from the stress signals under the pipeline normal condition, generating high-quality stress data features. Finally, the generated stress features are supplied to the Bayesian Gaussian mixture model (BGMM). And the weighted logarithm probability (WLP) is used as the health indicator for examining pipeline status. The results demonstrate that the relative error of residual magnetic stress model is controlled within 3 %, and the WLP value of fault samples is smaller than − 100, so that the proposed method can discriminate the normal and leak conditions as well as the risk and severity of leakage. This study provides a theoretical basis and new perspective for pipeline leakage detection. 

Leakage detection in natural gas pipeline based on unsupervised learning and stress perception

To obtain the direction of arrival (DOA) of the moving sound source from the sequential measurements collected by the microphone array is the main task in acoustic tracking and detection. Thanks to the development of compressive sensing and sparse Bayesian learning (SBL), treating time-varying DOA estimation as time-varying sparse signal recovery is considered to be a promising idea. However, most methods have assumed that the source is narrowband and the DOA is on the predefined sparse grid at each estimation step. In fact, most sound sources in the air are wideband and the DOA varies continuously. Therefore, the multi-frequency sequential SBL is proposed for the DOA estimation of the moving wideband sound source in this paper. In this method, gamma hyperprior is used as sparsity-promoting prior for multi-frequency bins so that the multi-frequency measurements can be utilized simultaneously, and with an inexact dynamic model, the sparsity-dependent information from the multi-frequency sequential measurements can be propagated to the next estimation step to improve the performance. Besides, the off-grid refinement is incorporated into the framework to adapt to the continuously varying DOA. Simulation results demonstrate that the proposed method has better performances under low signal-to-noise conditions with higher estimation accuracy and less computation time compared to other state-of-the-art methods. The field experiments show that our proposed method can has a stronger ability to suppress grating lobes and spatial aliasing than conventional methods in the estimation for wideband DOA and adapt to the scenarios where the number of sources also changes.

Multi-frequency sequential sparse Bayesian learning for DOA estimation of the moving wideband sound source

An integrated optical waveguide-type laser velocimeter has been proposed and demonstrated at the central wavelength of 1550 nm. The micro-fabricated and photo-lithographically defined the integrated sensor head has dimensions in the range of 0.25 mm <inline-formula> <tex-math notation="LaTeX">$\times3.50$ </tex-math></inline-formula> mm. The velocities in the range of <inline-formula> <tex-math notation="LaTeX">$5.0\times 10 ^{-2} \mu \text{m}\cdot \text{s}$ </tex-math></inline-formula>−1 to <inline-formula> <tex-math notation="LaTeX">$2.2\times 10\,\,^{6} \mu \text{m}\cdot \text{s}$ </tex-math></inline-formula>−1, and a resolution of <inline-formula> <tex-math notation="LaTeX">$5.0\times 10\,\,^{-2} \mu \text{m}\cdot \text{s}$ </tex-math></inline-formula>−1 have been achieved in the experiment. Through three experimental measurements and data calculation in the measured velocity range, the average relative error is less than 0.52%. This small size semiconductor sensor velocimeter uses semiconductor materials (silicon dioxide, SiO2) to make key sensor elements. The refractive indexes of waveguide core, upper cladding and lower cladding material are 1.448, 1.442 and 1.444. The optical interference fringes were used for velocity measurement, and the collected scattered light signal was used for velocity analysis. The apparent advantages of small size, high precision with large dynamic range, low cost, and high batch-fabrication uniformity make the velocimeter suitable for non-invasive measurement of ultra-low speeds of gases, liquids or solids at the near-surface.

Optical Waveguide-Type Laser Interference Velocimeter for Measurement of Ultra-Low Speeds

This article presents a comprehensive active ${N}\,\,+ 4$ coupling matrix approach for the design of integrated filter–amplifier. The feedback between gate and drain, which is neglected in a previous work, is considered, which improves the accuracy of the coupling matrix model for transistors. More importantly, the relationship between the coupling matrix and the noise figure is also established, which extends the coupling matrix method to tackle noise-related circuit functions. Substrate integrated waveguide (SIW) filters are used to implement an integrated $X$ -band filter–amplifier design and to validate the design approach in terms of return loss, gain, and noise. Compared with rectangular waveguide, SIW is utilized for its appealing advantages, such as lower production cost, easier fabrication, and most importantly easier integration with active components. A second-order filtering circuit is applied to simultaneously match the input and output of the transistor. The integration reduces the losses from the intermediate networks in conventional designs, which is particularly important when the frequencies go higher. The measurements agree very well with the simulations in terms of S-parameters, gains, and noise figures.

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Substrate Integrated Waveguide Filter–Amplifier Design Using Active Coupling Matrix Technique

The flow field is one of the key factors that affect the measuring accuracy of ultrasonic gas flowmeters. The present work demonstrates that the designed novel flow conditioner can enhance the measurement accuracy by homogenizing the velocity profile in the acoustic transmission area. The main objective of this study is to reduce the non-uniformity of flow on velocity distribution. To accomplish this objective, a combination of theoretical analysis and numerical simulations is implemented, and the results indicate that the 10:1 aspect ratio rectangular fluid channel is better applied in ultrasonic gas flowmeters. Thus, a Computational Fluid Dynamics (CFD) model of novel flow conditioner based on the 10:1 fluid channel is simulated and validated by an experimental study. The results verify that the ultrasonic gas flowmeter composed of designed flow conditioner can reduce indication errors by up to 6%; moreover, the repeatability of all the tested standard flow rates can meet the national standard and even be enhanced by 0.15%.

Experimental and Numerical Analysis of a Novel Flow Conditioner for Accuracy Improvement of Ultrasonic Gas Flowmeters

https://doi.org/10.1016/j.pacs.2022.100334

Lei Li

Papers

Substrate Integrated Waveguide Filter–Amplifier Design Using Active Coupling Matrix Technique

Experimental and Numerical Analysis of a Novel Flow Conditioner for Accuracy Improvement of Ultrasonic Gas Flowmeters

Sensitivity enhanced NIR photoacoustic CO detection with SF6 promoting vibrational to translational relaxation process

SuperSoundcompass: a high-accuracy acoustic localization sensor using a small-aperture microphone array

Three-dimensional localization of gas leakage using acoustic holography