All-pass Filter Configuration Research Articles

Two-CFOA-grounded-capacitor first-order all-pass filter configurations with ideally infinite input impedance

Recently, Yuce, Verma, Pandey and Minaei presented two interesting current feedback operational amplifier (CFOA)-based first-order all pass filter (APF) configurations employing a single grounded capacitor (GC). Their first circuit employs only two CFOAs (along with five resistors) but does not have ideally infinite input impedance; the second circuit although does possess ideally infinite input impedance but requires three CFOAs (along with five resistors). In this paper, we present six new GC-APFs which employ only two CFOAs and yet provide infinite input impedance with a reduced number of only three/four resistors than the quoted earlier circuits. A non-ideal analysis of all the proposed circuits has been carried out and the workability and utility of the proposed circuits has been corroborated by the SPICE simulation and hardware implementation results using AD844-type IC CFOAs. This paper, thus, adds a number of interesting alternatives to the CFOA-based first-order APFs presented in the mentioned earlier work.

Realizations of Current Transfer Functions Using Current Differencing Transconductance Amplifiers

Keskin and Biolek have proposed a current differencing transconductance amplifiers configuration for realizing quadrature oscillator using first-order all-pass filters. This paper exploits their all-pass filter configurations for realizing a wider class of current mode transfer functions. The synthesis procedure is illustrated with examples from first-order and second-order all-pass filters.

Dynamical analysis of double-ring resonator with non-instantaneous Kerr response and effect of loss

We investigate dynamics of Kerr-nonlinear resonant structures consisting of two coupled ring resonators in an all-pass filter configuration. We observe rich dynamical behavior, classify the states, and present a detailed description of transitions from steady state to self-pulsing and chaos. We show that the finite relaxation time and loss may significantly affect the nature and occurrence of self-pulsing states. We also discuss effects of strength of the coupling between the resonators and resonance splitting on the period and onset of self-pulsing operation.

Numerical scheme for simulation of self-pulsing and chaos in coupled microring resonators

Nonlinear coupled equations that describe propagation of optical pulses in waveguide structures under the slowly varying envelope approximation are solved by a simple explicit finite-difference scheme.The technique, which is based on upwind differencing, is used for modeling of Kerr-nonlinear structures with microring resonators in all-pass filter configuration. We show numerical examples that demonstrate existence of self-pulsing and chaotic solutions. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2238–2242, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26242

All-pass filters realised using the current-controlled CCII with intrinsic negative resistance

Novel first-order all-pass filter configurations are introduced in this article for the first time using CCIIs with negative intrinsic resistance. The first one offers the benefit of the high-impedance input with a simultaneous reduction of the number of required passive elements. In addition, one current conveyor and an appropriate adder are required instead of the two current conveyors employed in the corresponding earlier topology. The second proposed all-pass filter has the attractive characteristic, in comparison with those already published in the literature, that only a single current conveyor is required. In both these configurations, a single grounded resistor is required as a passive element. Thus, these configurations can be made resistorless using metal-oxide semiconductor field-effect transistors and, also the condition of realisability can be electronically satisfied.

Vertically integrated As_2S_3 ring resonator on LiNbO_3

Titanium-diffused lithium niobate (Ti:LiNbO3) waveguides are widely used in current fiber optic networks because of their high-speed, electro-optic modulation, and low-loss integration with standard single-mode fibers. However, they cannot achieve small ring resonators owing to their lack of a high core-to-cladding index contrast. To overcome this challenge, we vertically integrate an emerging chalcogenide glass waveguide technology on well-established Ti:LiNbO3 waveguides. We present, to our knowledge, the first arsenic trisulfide (As2S3) race-track ring resonator with a 290.8 μm bend radius in an all-pass filter configuration, integrated on a Ti:LiNbO3 waveguide. Vertical coupling is achieved using a unique taper design. Experimental results are shown for 10.6% coupling, 2.08 dB roundtrip loss, and a 25.4 GHz free-spectral range.

High-rate data buffering in silicon nanophotonic devices

Buffers represent one of the most important components in a communications router. The device must be able to store data packets for a substantial period of time and release the data within an acceptable delay when the switch is clear. Optical buffers—devices that store optically transmitted data—are considered key elements to achieve synchronized and contention-free traffic in the design of all-light-based communication networks. Conventional buffers use optical fiber delay lines, but since the delay is for a fixed amount of time, they are unable to guarantee contention-free connections in the switch or through a network. Hence, research on tunable optical delay lines is generating significant interest, especially with optical communications now gearing up for large-scale integration. Advances in silicon technology are making this material a choice candidate for future integrated photonics. On-chip delay lines based on silicon-on-insulator (SOI) photonic wire waveguides were recently demonstrated, consisting of up to 100 microring resonators cascaded in either coupled-resonator or all-pass filter (APF) configurations with error-free operation up to 5Gbps.1 This demonstration was a major milestone in the development of all-optical buffers for interconnects. Tunable delays in an SOI planar waveguide based on slow light induced by stimulated Raman scattering (SRS) have also been reported,2 as well as intensity-tunable group delays in siliconmicroresonators enhanced by SRS.3 The functional mechanism of a ring resonator-based optical delay line can be described as follows: When a probe beam is injected into a ring with a frequency matching the resonance of the ring, light is forced to circle multiple times, lengthening the delay. If beam frequency deviates from resonance, it will bypass the ring and no delay will occur. When a pump light, whose frequency is of a different resonance, is injected into the microring resonator, the absorbed energy is eventually converted to therFigure 1. (a) Scanning electron microscope image of a microring resonator and (b) its resonance spectrum.

Ultracompact optical buffers on a silicon chip

On-chip optical buffers based on waveguide delay lines might have significant implications for the development of optical interconnects in computer systems. Silicon-on-insulator (SOI) submicrometre photonic wire waveguides are used, because they can provide strong light confinement at the diffraction limit, allowing dramatic scaling of device size. Here we report on-chip optical delay lines based on such waveguides that consist of up to 100 microring resonators cascaded in either coupled-resonator or all-pass filter (APF) configurations. On-chip group delays exceeding 500 ps are demonstrated in a device with a footprint below 0.09 mm2. The trade-offs between resonantly enhanced group delay, device size, insertion loss and operational bandwidth are analysed for various delay-line designs. A large fractional group delay exceeding 10 bits is achieved for bit rates as high as 20 Gbps. Measurements of system-level metrics as bit error rates for different bit rates demonstrate error-free operation up to 5 Gbps.

Noncritical Waveguide Alignment for Vertically Coupled Microring Using a Mode-Expanded Bus Architecture

Vertically coupled microrings in an all-pass filter configuration are fabricated with a range of waveguide misalignments deliberately introduced into the lithography masks to demonstrate noncritical fabrication requirements. The microrings have a mode-expanded bus design which allows a greatly reduced variation in power coupling coefficient-only 6% for fabrication misalignments as high as 1 mum. This represents a five-fold improvement in fabrication tolerance when compared with conventional designs

Realization of log‐domain high‐order transfer functions using first‐order building blocks and complementary operators

AbstractHigh‐order log‐domain filters could be easily designed by using the functional block diagram (FBD) representation of the corresponding linear prototype and a set of complementary operators. For this purpose, lossy and lossless integrator blocks have been already introduced in the literature. Novel first‐order log‐domain highpass and allpass filter configurations, which are fully compatible with the already published integrator blocks, are introduced in this paper. These are realized using integration and subtraction blocks or a novel differentiation configuration. As a result, a complete set of first‐order building blocks would be available for synthesizing any arbitrary high‐order transfer function. In order to verify the correct operation of the proposed structures, the performance of the introduced highpass filters was evaluated through simulation results. In addition, a fifth‐order log‐domain bandpass filter was designed and simulated using one of the introduced first‐order highpass filter configurations. Copyright © 2006 John Wiley & Sons, Ltd.

Mode conversion losses in silicon-on-insulator photonic wire based racetrack resonators

Two complimentary types of SOI photonic wire based devices, the add/drop (A/D) filter using a racetrack resonator and the Mach-Zehnder interferometer with one arm consisting of an identical resonator in all-pass filter (APF) configuration, were fabricated and characterized in order to extract the optical properties of the resonators and predict the performance of the optical delay lines based on such resonators. We found that instead of well-known waveguide bending and propagation losses, mode conversion loss in the coupling region of such resonators dominates when the air gap between the racetrack resonator and access waveguide is smaller than 120nm. We also show that this additional loss significantly degrades the performance of the optical delay line containing cascaded resonators in APF configuration.

A New Transadmittance Type First-Order Allpass Filter Employing Single Third Generation Current Conveyor

A novel transadmittance (TA) mode first-order all-pass filter configuration is proposed. The proposed circuit uses a third generation current conveyor (CCIII), three resistors and a grounded capacitor. The output of the filter exhibits high output impedance so that the synthesized filter can be cascaded without additional buffers. The theoretical results are verified with PSPICE simulations using a CMOS realization of CCIII.

Novel allpass filter configuration employing single OTRA

A new circuit configuration uses a single operational transresistance amplifier (OTRA) and four passive elements to realize both first- and second-order allpass filters. Owing to internal grounding of the OTRA input terminals, effects of input parasitics are significantly reduced. Applications of the circuit include the realization of the phase equalizer, the quadrature oscillator, and the high-Q bandpass filter for analog signal processing. The performance of the allpass filter is illustrated by circuit-level simulation of a quadrature oscillator with CMOS realization of the OTRA.

Current-Mode First-Order Allpass Filter Employing Single Current Operational Amplifier

A current-mode first-order allpass filter configuration is proposed. The presented circuit uses a single current operational amplifier (COA), a resistor and a capacitor, which are of minimum number. High output impedance of the proposed filter enables the circuit to be cascaded without additional buffers. The proposed circuit is insensitive to parasitic input capacitances and input resistances due to internally grounded input terminals of COA. It does not impose any component matching constraint in analog signal processing circuits. Non-ideal effects of COA to the first-order allpass network are also investigated. To demonstrate the performance of the proposed filter a new current-mode quadrature oscillator is given as an application example. The theoretical results are verified with PSPICE simulations using a new realization of fully differential CMOS COA.

Novel Transimpedance Type First-Order All-Pass Filter Using Single Otra

Summary A novel transimpedance-mode first-order all-pass filter configuration is proposed. It uses a single operational transresistance amplifier (OTRA) and few passive components. The proposed circuit is structurally all-pass that does not impose any component matching condition. The proposed circuit is insensitive to parasitic input capacitances and input resistances due to the internally grounded input terminals of the OTRA. It provides an alternative realization of phase equalizers for analog signal processing applications by providing also current-to-voltage conversion. The theoretical results are verified with PSPICE simulations using a CMOS realization of OTRA.

GaAs MESFET distributed baseband amplifier IC with allpass filter network

A distributed baseband amplifier integrated circuit (IC) which uses an allpass-filter configuration and three-dimensional transmission lines is described. An IC fabricated using 0.1 µm gatelength GaAs MESFETS has a 0 to > 62.5 GHz bandwidth with a flat gain of 10 dB. Its group delay variation in the 0-50 GHz band is only 12.4 ps. This is ~17 ps smaller than that of a conventional distributed baseband amplifier IC.