1,706 research outputs found
Digital Filters
The new technology advances provide that a great number of system signals can be easily measured with a low cost. The main problem is that usually only a fraction of the signal is useful for different purposes, for example maintenance, DVD-recorders, computers, electric/electronic circuits, econometric, optimization, etc. Digital filters are the most versatile, practical and effective methods for extracting the information necessary from the signal. They can be dynamic, so they can be automatically or manually adjusted to the external and internal conditions. Presented in this book are the most advanced digital filters including different case studies and the most relevant literature
Design and implementation of DA FIR filter for bio-inspired computing architecture
This paper elucidates the system construct of DA-FIR filter optimized for design of distributed arithmetic (DA) finite impulse response (FIR) filter and is based on architecture with tightly coupled co-processor based data processing units. With a series of look-up-table (LUT) accesses in order to emulate multiply and accumulate operations the constructed DA based FIR filter is implemented on FPGA. The very high speed integrated circuit hardware description language (VHDL) is used implement the proposed filter and the design is verified using simulation. This paper discusses two optimization algorithms and resulting optimizations are incorporated into LUT layer and architecture extractions. The proposed method offers an optimized design in the form of offers average miminimizations of the number of LUT, reduction in populated slices and gate minimization for DA-finite impulse response filter. This research paves a direction towards development of bio inspired computing architectures developed without logically intensive operations, obtaining the desired specifications with respect to performance, timing, and reliability
Frequency-Agile Microwave Filters For Radars With Simultaneous Transmission and Reception
Multi-band/multi-mode wireless communication systems have been receiving increased attention recently due to their potential for spectrum management in a dynamic spectral environment. Similarly radar systems, which can operate in a variety of frequency bands, could provide significant flexibility in the operation for the future applications. However, multi-band/multi-mode operation adds to the complexity of the microwave systems. Reconfigurable RF/microwave components in general, and tunable filters in particular, have been shown to be promising in significantly reducing the system complexity.
On the other hand, current trend of development in wireless communication and radar systems, forces more stringent requirements for electromagnetic spectrum sharing. Therefore, in many microwave applications a very high level
of isolation between the channels are required. This is including simultaneous transmit-receive systems or co-site interference scenarios where the leakage from high power transmitter into receiver degrades the system performance. In these applications, conventional tunable bandpass/bandstop filters cannot provide enough isolation between transmitter and receiver. A promising solution which provides a tunable null, independent of the tunable transmission passband, is a dynamic-tunable bandpass-bandstop filter cascade. In this research, a frequency-agile bandpass-bandstop filter cascade for radar systems with simultaneous transmission and reception is designed to create advanced filtering functionality to isolate the desired signals from interfering signals in a spectrally-crowded environment. For a radar with simultaneous transmit and receive, two filter cascade will be required. Each filter will be used on a separate frequency agile transceiver but they will be synchronized
to provide simultaneously a deep isolation region at one frequency for receive and a high power tolerant passband at an adjacent frequency for transmit
Planar microwave filters with electronically tunability and other novel configurations
In order to meet the increasing demands of advance wireless communications and
radar systems, several novel types of bandpass filters and bandstop filters have been
developed in this thesis.
A new type of varactor-tuned dual-mode bandpass filters have been presented to
achieve a nearly constant absolute bandwidth over a wide tuning range by using a single
DC bias circuit. Since the two operating modes (i.e., the odd and even modes) in a dualmode
microstrip open-loop resonator do not couple to each other, tuning the passband
frequency is accomplished by merely changing the two modal frequencies
proportionally. Design equations and procedures are derived, and two two-pole tunable
bandpass filters and a four-pole tunable bandpass filter of this type are demonstrated
experimentally.
Miniature microstrip doublet dual-mode filters that exhibit quasi-elliptic function
response without using any cross coupling have been developed. It shows that a single
two-pole filter or the doublet can produce two transmission zeros resulting from a
double behaviour of the dual-mode resonator of this type. Electromagnetic (EM)
simulation and experiment results of the proposed filters are described.
Parallel feed configuration of a microstrip quasi-elliptic function bandpass filter
has been built with a pair of open-loop dual-mode resonators. By employing this new
coupling scheme, a novel filter topology with three-pole quasi-elliptic function
frequency response can be obtained, leading to good passband performance, such as low
insertion loss and good matching at the mid-band of passband. A designed three-pole
bandpass filter of this type is demonstrated experimentally.
A new class of dual-band filters based on non-degenerate dual-mode microstrip
slow-wave open-loop resonators, which support two non-degenerate modes that do not
couple, have been introduced. Different feed schemes that affect the filtering
characteristics are investigated. Examples of dual-band filters of this type are described
with simulation and experiment results.
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In order to achieve a wide spurious-free upper passband, a novel design of
bandstop filter with cancellation of first spurious mode by using coupled three-section
step impedance resonators (SIRs) has been developed. This cancellation occurs when
two transmission poles coincide with the first spurious mode (transmission zero) by
properly choosing the step impedance ratio and the gap between the SIR and the main
transmission line. A stripline bandstop filter and a microstrip bandstop filter of this type
are designed, fabricated and tested. As a preliminary investigation, the microstrip filter
is tuned electronically using ferroelectric thin film varactors
Multirate digital filters, filter banks, polyphase networks, and applications: a tutorial
Multirate digital filters and filter banks find application in communications, speech processing, image compression, antenna systems, analog voice privacy systems, and in the digital audio industry. During the last several years there has been substantial progress in multirate system research. This includes design of decimation and interpolation filters, analysis/synthesis filter banks (also called quadrature mirror filters, or QMFJ, and the development of new sampling theorems. First, the basic concepts and building blocks in multirate digital signal processing (DSPJ, including the digital polyphase representation, are reviewed. Next, recent progress as reported by several authors in this area is discussed. Several applications are described, including the following: subband coding of waveforms, voice privacy systems, integral and fractional sampling rate conversion (such as in digital audio), digital crossover networks, and multirate coding of narrow-band filter coefficients. The M-band QMF bank is discussed in considerable detail, including an analysis of various errors and imperfections. Recent techniques for perfect signal reconstruction in such systems are reviewed. The connection between QMF banks and other related topics, such as block digital filtering and periodically time-varying systems, based on a pseudo-circulant matrix framework, is covered. Unconventional applications of the polyphase concept are discussed
Channelization for Multi-Standard Software-Defined Radio Base Stations
As the number of radio standards increase and spectrum resources come under more pressure, it becomes ever less efficient to reserve bands of spectrum for exclusive use by a single radio standard. Therefore, this work focuses on channelization structures compatible with spectrum sharing among multiple wireless standards and dynamic spectrum allocation in particular. A channelizer extracts independent communication channels from a wideband signal, and is one of the most computationally expensive components in a communications receiver. This work specifically focuses on non-uniform channelizers suitable for multi-standard Software-Defined Radio (SDR) base stations in general and public mobile radio base stations in particular.
A comprehensive evaluation of non-uniform channelizers (existing and developed during the course of this work) shows that parallel and recombined variants of the Generalised Discrete Fourier Transform Modulated Filter Bank (GDFT-FB) represent the best trade-off between computational load and flexibility for dynamic spectrum allocation. Nevertheless, for base station applications (with many channels) very high filter orders may be required, making the channelizers difficult to physically implement.
To mitigate this problem, multi-stage filtering techniques are applied to the GDFT-FB. It is shown that these multi-stage designs can significantly reduce the filter orders and number of operations required by the GDFT-FB. An alternative approach, applying frequency response masking techniques to the GDFT-FB prototype filter design, leads to even bigger reductions in the number of coefficients, but computational load is only reduced for oversampled configurations and then not as much as for the multi-stage designs. Both techniques render the implementation of GDFT-FB based non-uniform channelizers more practical.
Finally, channelization solutions for some real-world spectrum sharing use cases are developed before some final physical implementation issues are considered
Digit-slicing architectures for real-time digital filters
One of the many important algorithmic techniques in digital
signal processing is real-time digital filtering. Modular sliced
structures for digital filters have been proposed before, but the
nature of implementation has been mainly constrained to non-recursive
second order digital filters with positive values of coefficients.
The aim of this research project is to extend this modular
digit slicing concept to more practical higher order digital
filters which are recursive and are of many forms (direct, nondirect,
canonic, non-canonic). [Continues.
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