640 research outputs found
Microwave and RF Applications for Micro-resonator based Frequency Combs
Photonic integrated circuits that exploit nonlinear optics in order to
generate and process signals all-optically have achieved performance far
superior to that possible electronically - particularly with respect to speed.
We review the recent achievements based in new CMOS-compatible platforms that
are better suited than SOI for nonlinear optics, focusing on radio frequency
(RF) and microwave based applications that exploit micro-resonator based
frequency combs. We highlight their potential as well as the challenges to
achieving practical solutions for many key applications. These material systems
have opened up many new capabilities such as on-chip optical frequency comb
generation and ultrafast optical pulse generation and measurement. We review
recent work on a photonic RF Hilbert transformer for broadband microwave
in-phase and quadrature-phase generation based on an integrated frequency
optical comb. The comb is generated using a nonlinear microring resonator based
on a CMOS compatible, high-index contrast, doped-silica glass platform. The
high quality and large frequency spacing of the comb enables filters with up to
20 taps, allowing us to demonstrate a quadrature filter with more than a
5-octave (3 dB) bandwidth and an almost uniform phase response.Comment: 10 pages, 6 figures, 68 references. arXiv admin note: substantial
text overlap with arXiv:1512.0174
Reconfigurable fractional microwave signal processor based on a microcomb
We propose and demonstrate reconfigurable fractional microwave signal
processing based on an integrated Kerr optical microcomb. We achieve two forms
of microwave signal processing functions, a fractional Hilbert transform as
well as a fractional differentiator. For the Hilbert transform we demonstrate a
phase shift of 45 degrees, half that of a full Hilbert transform, while for the
differentiator we achieve square-root differentiation. For both, we achieve
high resolution over a broad bandwidth of 17 GHz with a phase deviation of less
than 5 per degree within the achieved passband. This performance in both the
frequency and time domains demonstrates the versatility and power of
micro-combs as a basis for high performance microwave signal processing.Comment: 4 pages 5 figures, 32 references. arXiv admin note: text overlap with
arXiv:1903.08541, arXiv:1904.0099
Digital Filter Design Using Improved Teaching-Learning-Based Optimization
Digital filters are an important part of digital signal processing systems. Digital filters are divided into finite impulse response (FIR) digital filters and infinite impulse response (IIR) digital filters according to the length of their impulse responses. An FIR digital filter is easier to implement than an IIR digital filter because of its linear phase and stability properties. In terms of the stability of an IIR digital filter, the poles generated in the denominator are subject to stability constraints. In addition, a digital filter can be categorized as one-dimensional or multi-dimensional digital filters according to the dimensions of the signal to be processed. However, for the design of IIR digital filters, traditional design methods have the disadvantages of easy to fall into a local optimum and slow convergence. The Teaching-Learning-Based optimization (TLBO) algorithm has been proven beneficial in a wide range of engineering applications. To this end, this dissertation focusses on using TLBO and its improved algorithms to design five types of digital filters, which include linear phase FIR digital filters, multiobjective general FIR digital filters, multiobjective IIR digital filters, two-dimensional (2-D) linear phase FIR digital filters, and 2-D nonlinear phase FIR digital filters. Among them, linear phase FIR digital filters, 2-D linear phase FIR digital filters, and 2-D nonlinear phase FIR digital filters use single-objective type of TLBO algorithms to optimize; multiobjective general FIR digital filters use multiobjective non-dominated TLBO (MOTLBO) algorithm to optimize; and multiobjective IIR digital filters use MOTLBO with Euclidean distance to optimize. The design results of the five types of filter designs are compared to those obtained by other state-of-the-art design methods. In this dissertation, two major improvements are proposed to enhance the performance of the standard TLBO algorithm. The first improvement is to apply a gradient-based learning to replace the TLBO learner phase to reduce approximation error(s) and CPU time without sacrificing design accuracy for linear phase FIR digital filter design. The second improvement is to incorporate Manhattan distance to simplify the procedure of the multiobjective non-dominated TLBO (MOTLBO) algorithm for general FIR digital filter design. The design results obtained by the two improvements have demonstrated their efficiency and effectiveness
Time-domain response of nabla discrete fractional order systems
This paper investigates the time--domain response of nabla discrete
fractional order systems by exploring several useful properties of the nabla
discrete Laplace transform and the discrete Mittag--Leffler function. In
particular, we establish two fundamental properties of a nabla discrete
fractional order system with nonzero initial instant: i) the existence and
uniqueness of the system time--domain response; and ii) the dynamic behavior of
the zero input response. Finally, one numerical example is provided to show the
validity of the theoretical results.Comment: 13 pages, 6 figure
An Electrically Programmable Split-Electrode Charge-Coupled Transversal Filter (EPSEF)
A CCD split-electrode transversal filter (EPSEF) with analog controlled tap weights is described. The programmable tap weighting utilizes a novel analog multiplier for sampled data, based on charge profiling underneath a resistive gate structure. The EPSEF device concept and the performance data of a prototype filter with eight programmable taps are presented. Applications of the EPSEF in several programmed filter functions and in an adaptive filter system are demonstrated
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