Programmable Filter Research Articles

Optical parametric amplification of sub-cycle shortwave infrared pulses

Few–cycle short–wave infrared (SWIR) pulses are useful tools for research on strong–field physics and nonlinear optics. Here we demonstrate the amplification of sub–cycle pulses in the SWIR region by using a cascaded BBO–based optical parametric amplifier (OPA) chain. By virtue of the tailored wavelength of the pump pulse of 708 nm, we successfully obtained a gain bandwidth of more than one octave for a BBO crystal. The division and synthesis of the spectral components of the pulse in a Mach–Zehnder–type interferometer set in front of the final amplifier enabled us to control the dispersion of each spectral component using an acousto–optic programmable dispersive filter inserted in each arm of the interferometer. As a result, we successfully generated 0.73–optical–cycle pulses at 1.8 μm with a pulse energy of 32 μJ.

A Reconfigurable Analog Baseband Circuitry for LFMCW RADAR Receivers in 130-nm SiGe BiCMOS Process

A highly reconfigurable open-loop analog baseband circuitry with programmable gain, bandwidth and filter order are proposed for integrated linear frequency modulated continuous wave (LFMCW) radar receivers in this paper. This analog baseband chain allocates noise, gain and channel selection specifications to different stages, for the sake of noise and linearity tradeoffs, by introducing a multi-stage open-loop cascaded amplifier/filter topology. The topology includes a course gain tuning pre-amplifier, a folded Gilbert variable gain amplifier (VGA) with a symmetrical dB-linear voltage generator and a 10-bit R-2R DAC for fine gain tuning, a level shifter, a programmable Gm-C low pass filter, a DC offset cancellation circuit, two fixed gain amplifiers with bandwidth extension and a novel buffer amplifier with active peaking for testing purposes. The noise figure is reduced with the help of a low noise pre-amplifier stage, while the linearity is enhanced with a power-efficient buffer and a novel high linearity Gm-C filter. Specifically, the Gm-C filter improves its linearity specification with no increase in power consumption, thanks to an alteration of the trans-conductor/capacitor connection style, instead of pursuing high linearity but power-hungry class-AB trans-conductors. In addition, the logarithmic bandwidth tuning technique is adopted for capacitor array size minimization. The linear-in-dB and DAC gain control topology facilitates the analog baseband gain tuning accuracy and stability, which also provides an efficient access to digital baseband automatic gain control. The analog baseband chip is fabricated using 130-nm SiGe BiCMOS technology. With a power consumption of 5.9~8.8 mW, the implemented circuit achieves a tunable gain range of −30~27 dB (DAC linear gain step guaranteed), a programmable −3 dB bandwidth of 18/19/20/21/22/23/24/25 MHz, a filter order of 3/6 and a gain resolution of better than 0.07 dB.

High-speed chemical imaging of dynamic and histological samples with stimulated Raman micro-spectroscopy.

We report a shot noise limited high-speed stimulated Raman microscopy platform allowing to acquire molecular vibrational spectra over 200 cm-1 in 12 µs at a scan rate of 40kHz. Using spectral focusing together with optimized acousto-optics programmable dispersive filters, the designed low noise imaging platform performs chemical imaging of dynamical processes such as Mannitol crystal hydration and reaches a signal to noise ratio sufficient to perform label free histological imaging on frozen human colon tissue slides.

Design and Implementation of Reversible Vedic Multiplier with Trlic

The 'Vedic Mathematics' is the name given to the ancient system of mathematics with a unique technique of calculations based on simple rules and principles with which any mathematical problem can be solved with the help of arithmetic, algebra, geometry or trigonometry. In any of the fastest ALU, multiplier play an inevitable role. There is always a demand on high speed multiplier due to the raising limitation on delay. Increasing the speed of a multiplier there are number of new techniques have been implemented in which multiplier using Vedic mathematics are foremost one. The system performance and delay depend on the performance of multiplier used in it. Multiplier are used in different area such as cryptography, image processing application, embedded system application, programmable filter application etc .One of the major techniques to scale back the power dissipation is Reversible logic. There is no loss of data therefore power dissipation is reduced producing distinctive output for fixed input and vice-versa. The main objective of the project is to scale back the TRLIC of the multiplier factor by exploitation of Vedic arithmetic.The proposed methods are designed using VHDL Programming language, simulation and synthesis are done using Cadence RTL compiler in 180nm technology.

Out-of-band suppression improved tunable microwave photonic Hilbert transformer based on optical spectral shaping

An out-of-band suppression improved microwave photonic Hilbert transformer (MPHT) with adjustable bandwidth and central frequency based on optical spectral shaping is theoretically analyzed and experimentally demonstrated. The MPHT consists of a broadband optical source, a Mach–Zehnder interferometer (MZI), a dispersion compensating fiber and a photodetector. The MZI incorporates an intensity modulator in one arm and a programmable optical filter (POF) and a variable optical delay line in the other. The frequency response of the MPHT is determined by the Fourier transformation of the optical spectral shaping response of the POF. By tailoring the optical phase profile, a π phase shift can be introduced into the center of the MPHT. By shaping the optical amplitude profile, a MPHT with adjustable bandwidth and improved sidelobe suppression can be achieved. In the experiments, MPHTs with bandwidths varying from 100 MHz to 1 GHz and the central frequency varying from 2.5 GHz to 16.5 GHz are demonstrated. The out-of-band suppression is more than 20 dB, which is the best result ever reported for a MPHT. The impulse response of the MPHT is verified and the result proves that the proposed MPHT can be applied to microwave analytic signal processing systems.

A novel programmable attenuator based low Gm-OTA for biomedical applications

In this paper, a novel programmable operational transconductance amplifier (POTA) using a pseudo resistor based programmable attenuator is proposed. A 4th order Butterworth programmable low pass filter (LPF) targeted for biomedical applications is designed using the proposed POTA. The proposed POTA and the LPF are designed and implemented in 0.18 ​μm CMOS technology with a supply voltage of 1 ​V and their performances are evaluated through post-layout simulations. The proposed POTA consumes a power of 27 ​nW, and its transconductance could be varied from 27 ​nA/V to 75 ​nA/V. It has higher linearity, dynamic range (DR) of 85.62 ​dB–79.46 ​dB and lower input-referred noise (IRN) of 33.15 μVrms to 58.65 μVrms than pre-input voltage attenuator based OTAs. The proposed LPF consumes a power of 208 ​nW. Its output dynamic range and IM3 lie in the range of (62.1 ​dB–49.26 ​dB) and (61.87 ​dB–53.14 ​dB) respectively. Its cutoff frequency can be varied from 100 ​Hz to 250 ​Hz.

Memristive and Memory Impedance Behavior in a Photo-Annealed ZnO–rGO Thin-Film Device

An oxygen-rich ZnO-reduced graphene oxide (rGO) thin film was synthesized using a photo-annealing technique from zinc precursor (ZnO)–graphene oxide (GO) sol–gel solution. X-ray diffraction (XRD) results show a clear characteristic peak corresponding to rGO. The scanning electron microscope (SEM) image of the prepared thin film shows an evenly distributed wrinkled surface structure. Transition Metal Oxide (TMO)-based memristive devices are nominees for beyond CMOS Non-Volatile Memory (NVRAM) devices. The two-terminal Metal–TMO (Insulator)–Metal (MIM) memristive device is fabricated using a synthesized ZnO–rGO as an active layer on fluorine-doped tin oxide (FTO)-coated glass substrate. Aluminum (Al) is deposited as a top metal contact on the ZnO–rGO active layer to complete the device. Photo annealing was used to reduce the GO to rGO to make the proposed method suitable for fabricating ZnO–rGO thin-film devices on flexible substrates. The electrical characterization of the Al–ZnO–rGO–FTO device confirms the coexistence of memristive and memimpedance characteristics. The coexistence of memory resistance and memory impedance in the same device could be valuable for developing novel programmable analog filters and self-resonating circuits and systems.

Sculpting the spin-wave response of artificial spin ice via microstate selection

Artificial spin ice (ASI) systems have emerged as promising hosts for magnonic applications due to a correspondence between their magnetic configuration and spin dynamics. Though it has been demonstrated that spin-wave spectra are influenced by the ASI microstate the precise nature of this relationship has remained unclear. Recent advances in controlling the magnetic configuration of ASI make harnessing the interplay between spin dynamics and the microstate achievable. This could allow diverse applications including reconfigurable magnonic crystals and programmable microwave filters. However, extracting any novel functionality requires a full understanding of the underlying spin-wave/microstate interaction. Here, we present a systematic analysis of how the microstate of a honeycomb ASI system affects its spin-wave spectrum through micromagnetic simulations. We find the spectrum to be highly tunable via the magnetic microstate, allowing the (de)activation of spin-wave modes and band-gap tuning via magnetic reversal of individual nanoislands. Symmetries of ASI systems and the chirality of ``monopole'' defects are found to play important roles in determining the high-frequency magnetic response.

Study on millimeter-wave photonic generator scheme with tunable multiplication factors

In this paper, we propose and demonstrate a prototype of millimeter-wave (MMW) generator with tunable multiplication factors. A dual-parallel Mach-Zehnder modulator and a remodulation structure are used to effectively excite higher-order optical sidebands and a programmable filter contributes to changing multiplication factors. In our work, frequency-quadrupling (20GHz), frequency-12-tupling (60GHz) and frequency-20-tupling (60 GHz) MMW signals were generated, transmitted and detected. Benefited from the satisfactory unwanted mode suppression ratio, the generated signals show anti-power fluctuation capability along the fiber length, which helps to reduce the power penalty in signal transmission.

Design of programmable multi-wavelength tunable filter on lithium niobate

Tunable optical filters have a wide range of applications, especially in optical sensing systems and optical communication systems. In this letter, a programmable multi-wavelength tunable filter on Lithium Niobate (LN) is designed. The spectral response of the filter could be tuned by manipulating the voltage applied on the electrode pairs due to the electro-optic effect of LN. Besides, the number of resonant wavelength and the wavelength spacing are both programmable by encoding the electrode pairs. The number of resonant wavelength is reconfigured by changing the number of ‘1’ in the code. The wavelength spacing of the filter is reconfigured by the number of ‘0’ between adjacent ‘1’ in the code.

Spectral Difference Interferometry for the Characterization of Optical Media

AbstractA new form of interferometry combining high phase sensitivity and excellent mechanical isolation is proposed and demonstrated. These features arise from maintaining a probe and reference tone in the same medium under test at all times, their ultimate homodyne detection, as well as a novel method employing an optical programmable filter which is used to extract their relative phase difference. A compilation of studies performed to illustrate the applicability of the scheme to a range of measurements of optical propagation characteristics is presented. Measurements include the chromatic dispersion of SMF‐28 of lengths ranging from 1 m to 1 km, the nonlinear coefficient of highly nonlinear fiber and the phase transfer profile of an integrated optical ring resonator.

Discretely programmable microwave photonic filter based on temporal Talbot effects.

We propose and experimentally demonstrate a reconfigurable microwave photonic filter based on temporal Talbot effects. The microwave signal is first uniformly sampled by a train of optical pulses through electro-optic intensity modulation. The sampled optical pulses are then directed to a Talbot-based optical signal processor, consisting of an electro-optic temporal phase modulator and a chromatic dispersion line. The Talbot-based microwave photonic filter (TMPF) exploits the inherent properties of the Talbot self-imaging effect for mitigating pulse-to-pulse intensity fluctuations of optical pulses to transmit some fluctuation frequencies and mitigate or entirely block other microwave spectral components. The output microwave signal is finally reconstructed from the processed optical pulses and the resultant RF response is measured by a network analyzer. The TMPF exhibits an RF response with periodic, symmetric-profile passbands whose center frequency and free spectral range (FSR) are defined by the sampling rate and the dispersion value. The filter passbands can be reconfigured electrically, in discrete steps, by adjusting the modulation function of the phase modulator, i.e., without the need for manual adjustment of the optical components. This enables the capability of selection of specific passbands among the primary passbands. The phase modulation function is provided using an arbitrary waveform generator, with the potential for fast tuning of the filter's spectral response. The bandwidth of the filter passband can also be easily customized by adjusting the sampling pulse's temporal width using an optical bandpass filter. Examples of filter performance in various passband configurations are also presented in the time domain to further validate the operation of the filter.

A Study of Phase Noise and Frequency Error of a Fractional-N PLL in the Course of FMCW Chirp Generation

This paper presents the theoretical and experimental results on the phase noise spectrum and the rms frequency error of a fractional-N phase-locked loop (PLL) under frequency-modulated continuous-wave (FMCW) chirp generation. The phase noise spectrum under modulation is analytically calculated for a second-order charge pump PLL with a feedback divider ratio linearly changing over time. This is followed by an analysis of the steady-state rms frequency error of the output frequency after PLL settling is achieved during chirp generation. A fractional-N PLL with integrated frequency ramp generator is presented. Phase noise and jitter measurements on the PLL under modulation are performed at the output of the programmable feedback divider. The resulting low-frequency rms jitter is reduced by about 9dB with doubling the charge pump current, and reduced by about 6dB with halving the ramp slope. The rms frequency error under FMCW modulation is measured at the modulated voltage-controlled oscillator output. The dependence of the frequency error on the loop filter capacitance for various ramp slopes is given. A frequency error of 112kHz is achieved with a ramp slope of 1.28GHz/80 μs at a carrier frequency of 62GHz. The noise measurements are in good agreement with the developed phase noise model. A programmable loop filter capacitance is suggested to accommodate the static phase offset and the resulting noise performance to the ramp slope.

Light Attenuation Display: Subtractive See-Through Near-Eye Display via Spatial Color Filtering.

We present a display for optical see-through near-eye displays based on light attenuation, a new paradigm that forms images by spatially subtracting colors of light. Existing optical see-through head-mounted displays (OST-HMDs) form virtual images in an additive manner-they optically combine the light from an embedded light source such as a microdisplay into the users' field of view (FoV). Instead, our light attenuation display filters the color of the real background light pixel-wise in the users' see-through view, resulting in an image as a spatial color filter. Our image formation is complementary to existing light-additive OST-HMDs. The core optical component in our system is a phase-only spatial light modulator (PSLM), a liquid crystal module that can control the phase of the light in each pixel. By combining PSLMs with polarization optics, our system realizes a spatially programmable color filter. In this paper, we introduce our optics design, evaluate the spatial color filter, consider applications including image rendering and FoV color control, and discuss the limitations of the current prototype.

Four-Input One-Output Voltage-Mode Universal Filter Using Simple OTAs

This paper presents a new electronically tunable voltage-mode universal filter with four-input one-output employing six simple operational transconductance amplifiers (OTAs), two grounded capacitors and two MOS resistors. The use of grounded passive components is beneficial for integrated circuit implementation. The proposed filter can realize low-pass, band-pass, high-pass, band-stop and all-pass filtering functions without active and passive component-matching conditions and inverting-type input signals requirements. The natural frequency and quality factor can be tuned independently and electronically by adjusting the bias currents. The voltage-mode filter offers the features of high-input impedance and low active and passive sensitivities. The characteristics of the proposed universal filter are verified using PSPICE simulators through 0.35[Formula: see text][Formula: see text]m CMOS process. Experimental results are used to confirm the workability of proposed circuit through LM13600 commercially available OTAs. Also a digitally programmable filter is shown to confirm the advantage of multiple-input universal filter.

Instantaneous in‐band radio frequency interference suppression using non‐linear folders

A front-end adaptive folder with a filter is presented to instantaneously push jammers to higher frequencies while preserving the integrity of small signals of interest. A programmable filter is utilised to further suppress folded jammers for achieving a widely scalable dynamic range over a large frequency range. To achieve maximum programmability with a minimal increase of power and area, combinatorial intrinsic device characteristics are exploited to tune folding points for rapid adaptation to a changing electromagnetic environment.

Cooperative Operation of Parallel Connected Boost Converters for Low Voltage-High Power Applications: An Experimental Approach

Modern power conversion devices have realized several significant attributes such as high efficiency and reliability for high power (HP) applications. Traditionally, boost converters (BC) are required to operate as an intermediate interface to drive high power loads through available low voltage (LV) sources such as a fuel cell (FC), photovoltaic or battery based energy system. This paper addresses the complementary operation of parallel connected boost converters (PCBC) for high power applications considering wide spectrum of low voltage source conditions. The mutual sharing of load current between parallel connected converters is guaranteed by the appropriate placement of LC based passive equalization filter (LCEF) therefore offloading stress from individual converter and increasing efficiency and reliability drastically. To validate the performance of proposed topology in real-time scenarios, an experimental setup consisting of programmable source, electronic load, boost converters and filter circuit has been synthesized and studied in various operating conditions such as FC energy system based HP and LV application. The experimental results clarifies and validates the necessity of parallel connected converters based power splitting strategy and LC equalization filter topology for high power loads especially with low voltage source conditions.

Upgrading a Low-Cost System for Measuring Lightning Electric Field Waveforms

Recent upgrades of the low-cost lightning detection and waveform storage system (LDWSS) are presented. The system has been developed for research and operational use in the Amazon region of Brazil and it has been in operation in this region since November 1, 2017. The original version of the LDWSS operated for 10 months at the Lightning Observatory in Gainesville, Florida, where it was calibrated and tested. Two main modifications implemented include the improvement of the effective dynamic range and the capability to detect lightning in different frequency bands. The improvements were achieved by using two pre-amplifiers working in parallel, a new processing (smart saving) algorithm, and programmable analog filters. As a result, a single, low-cost lightning electric field measuring system allows one to record both close and far lightning events with good amplitude resolution and without saturation, and study both wideband and narrow-band (for example, very low frequency) field signatures of lightning, without modifying the hardware.

Monolithic lithium niobate photonic circuits for Kerr frequency comb generation and modulation

Microresonator Kerr frequency combs could provide miniaturised solutions for a wide range of applications. Many of these applications however require further manipulation of the generated frequency comb signal using photonic elements with strong second-order nonlinearity (χ(2)). To date these functionalities have largely been implemented as discrete components due to material limitations, which comes at the expense of extra system complexity and increased optical losses. Here we demonstrate the generation, filtering and electro-optic modulation of a frequency comb on a single monolithic integrated chip, using a nanophotonic lithium-niobate platform that simultaneously possesses large electro-optic (χ(2)) and Kerr (χ(3)) nonlinearities, and low optical losses. We generate broadband Kerr frequency combs using a dispersion-engineered high-Q lithium-niobate microresonator, select a single comb line using an electrically programmable add-drop filter, and modulate the intensity of the selected line. Our results pave the way towards monolithic integrated frequency comb solutions for spectroscopy, data communication, ranging and quantum photonics.

A novel dual loop adaptive equalizer based on spectrum balancing technique

Inductorless circuits are gaining advantage in RF and high-speed serial link circuits due to the reduced silicon area. This paper presents an inductor-less adaptive equalizer featuring both data rate adaptation and channel loss adaptation. The conventional adaptive equalizers use spectrum balancing technique. The spectrum balancing technique balances the power in low and high frequency components with cutoff frequency of the filters as 0.28Tb (Tb is the minimum bit period of the incoming data stream). The proposed technique removes the necessity of using high pass filter and uses only a programmable low-pass filter in the adaptive equalization loop. This technique leads to the tunability of the equalizer over a wide range of throughput and channel losses. For the proof of concept, the entire equalizer circuit is designed and fabricated in 180 nm mixed mode CMOS technology. The measurements with lossy channels show that the proposed adaptive equalizer is able to work well for the channel losses up to 6 dB and wide throughput of 1–3.125 Gbps. The design is targeted to operate at a maximum data rate of 3.125 Gbps to meet JESD 204 standards. The proposed adaptive equalizer consumes a power of 9.8 mW/Gbps including IO buffers.