Sub-Band Knowledge Distillation Framework for Speech Enhancement

In single-channel speech enhancement, methods based on full-band spectral features have been widely studied. However, only a few methods pay attention to non-full-band spectral features. In this paper, we explore a knowledge distillation framework based on sub-band spectral mapping for single-channel speech enhancement. Specifically, we divide the full frequency band into multiple sub-bands and pre-train an elite-level sub-band enhancement model (teacher model) for each sub-band. These teacher models are dedicated to processing their own sub-bands. Next, under the teacher models' guidance, we train a general sub-band enhancement model (student model) that works for all sub-bands. Without increasing the number of model parameters and computational complexity, the student model's performance is further improved. To evaluate our proposed method, we conducted a large number of experiments on an open-source data set. The final experimental results show that the guidance from the elite-level teacher models dramatically improves the student model's performance, which exceeds the full-band model by employing fewer parameters.Comment: Published in Interspeech 202

A Compact Monopole Antenna With Filtering Response for WLAN Applications

A novel compact monopole antenna with filtering response for WLAN applications is presented in this paper. The antenna is composed of a capacity-loaded matching patch, two resonators, and two end-coupled monopoles. The resonators consist of wide rectangular patches and narrow shorted lines to form the resonance, and the resonators are printed on the different layers to increase the design flexibility. Two meandering monopoles are located at the edges of the top layer with capacitive coupling at each other's end. The mutual couplings between the meander monopoles are utilized to produce two radiation nulls at the two band-edges. Based on the design method, the prototype of the proposed antenna was designed, fabricated and measured. The measured results show that the antenna has a broad bandwidth of 16% for S 11 <; -10 dB. Also, ideal omnidirectional radiation patterns, and steep band-edge selectivity with two radiation nulls are achieved for the proposed antenna

A Wideband Series-Fed Circularly Polarized Differential Antenna by Using Crossed Open Slot-Pairs

A novel method of designing a wideband series-fed circularly polarized (CP) differential antenna by using crossed open slot-pairs is presented in this paper. The near-field distributions and input impedance analyses show that the closely spaced open slot-pairs can radiate as the crossed dipoles and have stable radiating resistance with a compact radiator size. Besides, a wideband half-power phase shifter by using open slot is proposed and utilized to realize CP radiation. The proposed CP antenna is composed of a wide slot-pair and a narrow slot-pair. In the antenna design, the narrow slot-pair is not only excited as a radiator, but also elaborately loaded to provide wideband half-power output and quadrature phase excitation to the wide slot-pair. Both the proposed half-power phase shifter and CP antenna are illustrated by the corresponding equivalent circuits. Based on these analyses, the proposed antenna is designed, fabricated and measured. Compared to the simulated traditionally designed counterpart, 2.1 times wider axial ratio bandwidth is achieved for the proposed antenna. The measured overlapped bandwidth for axial ratio 10 dB is 1.95-3.45 GHz (55.6%). Also, the antenna gain and radiation patterns are measured, which agree well with the simulated results

A Dual-Polarized Planar Antenna Array Differentially-Fed by Orthomode Transducer

This paper presents a new design of a differentially-fed substrate integrated planar antenna array with dual-polarization. Compared with the traditional dual-polarized antenna arrays, the proposed array antenna has the advantages of simple configuration, high cross-polarization discrimination (XPD) and high gain. 2×2-element subarray design with a vialoaded crossover structure is used, which reduces the complexity of the array antenna. The operation bandwidth is improved by generating three resonances in the subarray. One 8×8 antenna array is designed, prototyped and tested to exemplify its potential applications in large dual-polarized antenna arrays. A planar orthomode transducer is used to achieve differential excitation for the antenna array. The measured results show that the proposed antenna array has an impedance bandwidth of 19.2–20.7 GHz for |S11| < −10 dB and port isolation higher than 20 dB. The array antenna exhibits a high XPD of 43 dB and a flat gain about 22.2 dBi within the bandwidth

A Low Complexity 16 X 16 Butler Matrix Design Using Eight-Port Hybrids

Beamforming networks such as Butler Matrices are important for multibeam array antenna applications. The challenge for Butler Matrix design is that their complexity increases with the number of ports. In this paper, a novel approach of designing a 16 X 16 Butler Matrix with significant structure simplification is presented. The eight-port hybrids with no crossovers are used to simplify the network. To ensure the network has the same magnitude and phase responses as the standard one, the location and phase shifting value of each fixed phase shifter are derived from the $S$ -matrix of each hybrid. A $16\times 16$ Butler Matrix network operating from 9 GHz–11 GHz is designed to validate this concept. The compensated microstrip 3-dB/90° directional coupler, the phase shifter with a shunt open-and-short stub and the crossover with a resonating patch are used to reduce the transmission loss and enable broadband operation

Expanding Transportation Opportunities on Hawai`I Island

Residents of Hawai`i Island pay some of the highest rates for electricity and petroleum products among residents of the United States. Moreover, the islands of the Hawaiian archipelago rely almost entirely on imported petroleum fuels for both transportation and energy generation. Though Hawai`i Island has integrated more renewable energy onto its electrical grid than anywhere else in the U.S., the reliance on fossil fuel remains high because more than half the energy demand of the island can be attributed to transportation. Traditionally mass transit systems can be used to increase energy efficiency, as well as energy sustainability of a transportation system; as a result the University of Michigan team was engaged by The Kohala Center to examine and analyze the public transit system of Hawai`i Island for potential improvements. The primary objective of the project is to develop a set of recommendations for the County of Hawai`i focused on high-­‐impact solutions to reduce fossil fuel use in the island’s ground transportation system, while improving accessibility and lowering travel times for commuters. Our team completed initial research to gain a background on Hawai`i and its energy and transit challenges, completed data collection and analysis through a research trip to Hawai`i, and designed a set of recommendations for optimizing the current system, as well as potential alternatives that include the establishment of carpooling and ride-­‐sharing networks that would employ new business models to help solve some additional transit issues.Master of ScienceNatural Resources and EnvironmentUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/106554/1/Hawaii Transit_Final_for distribution_2014.pd