The development a fully-balanced current-tunable first-order low-pass filter with Caprio technique

This paper presents the development and design of a fully-balanced current-tunable first-order low-pass filter with Caprio technique, which could include the design and implementation of a first-order low-pass filter circuits. The filter consists of six bipolar junction transistor (BJT) and a single capacitor. The filter construction uses a bipolar junction transistor (BJT) as the main device and a single capacitor. A fully-balanced current-tunable first-order low-pass filter with Caprio technique developed. The architecture of the circuit is quite simple and proportional, symmetrical with signs of difference. Circuits developed into integrated circuits act like basic circuits for frequency filter circuits, current modes with Caprio techniques, obtained by improving the first-order low-pass filter for signal differences with incoming impedances. Adjusting the parameters of the circuit with the caprio technique achieves the optimal parameter value for correcting the total harmonic distortion value. The results of testing the operation of the circuit, a fully-balanced current-tunable first-order low-pass filter with Caprio technique developed and designed using the PSpice program. The simulation results showed good results in line with predicted theoretical analysis. The sensitivity of the device to the center frequency (ω0) response is low and independent of variables, the angular frequency is linear with wide current adjustment throughout the sweeping range of a wide frequency range, with a wide range of over tree orders of magnitude. Therefore, fully-balanced current-tunable first-order low-pass filter developed is very suitable to apply various applications regarding low frequency signal filtration, for example in biomedical systems, for example

RF Measurement Techniques

For the characterization of components, systems and signals in the range of microwave and radio-frequencies (RF) specific equipment and dedicated measurement instruments are used. In this article the fundamentals of RF signal processing and measurement techniques are discussed. It gives complementary background information for the introduction to RF Measurement Techniques and the Practical RF Course, which are part of the Advanced Accelerator Physics training program of the CERN Accelerator School (CAS) and have also been presented at the CAS 2018 Special Topic Course in Beam Instrumentation.Comment: 54 pages, contribution to the CAS - CERN Accelerator School: Beam Instrumentation, 2-15 June 2018, Tuusula, Finlan

A LINEARIZATION METHOD FOR A UWB VCO-BASED CHIRP GENERATOR USING DUAL COMPENSATION

Ultra-Wideband (UWB) chirp generators are used on Frequency Modulated Continuous Wave (FMCW) radar systems for high-resolution and high-accuracy range measurements. At the Center for Remote Sensing of Ice Sheets (CReSIS), we have developed two UWB radar sensors for high resolution measurements of surface elevation and snow cover over Greenland and Antarctica. These radar systems are routinely operated from both surface and airborne platforms. Low cost implementations of UWB chirp generators are possible using an UWB Voltage Controlled Oscillator (VCO). VCOs possess several advantages over other competing technologies, but their frequency-voltage tuning characteristics are inherently non-linear. This nonlinear relationship between the tuning voltage and the output frequency should be corrected with a linearization system to implement a linear frequency modulated (LFM) waveform, also known as a chirp. If the waveform is not properly linearized, undesired additional frequency modulation is found in the waveform. This additional frequency modulation results in undesired sidebands at the frequency spectrum of the Intermediate Frequency (IF) stage of the FMCW radar. Since the spectrum of the filtered IF stage represents the measured range, the uncorrected nonlinear behavior of the VCO will cause a degradation of the range sensing performance of a FMCW radar. This issue is intensified as the chirp rate and nominal range of the target increase. A linearization method has been developed to linearize the output of a VCO-based chirp generator with 6 GHz of bandwidth. The linearization system is composed of a Phase Lock Loop (PLL) and an external compensation added to the loop. The nonlinear behavior of the VCO was treated as added disturbances to the loop, and a wide loop bandwidth PLL was designed for wideband compensation of these disturbances. Moreover, the PLL requires a loop filter able to attenuate the reference spurs. The PLL has been designed with a loop bandwidth as wide as possible while maintaining the reference spur level below 35 dBc. Several design considerations were made for the large loop bandwidth design. Furthermore, the large variations in the tuning sensitivity of the oscillator forced a design with a large phase margin at the average tuning sensitivity. This design constraint degraded the tracking performance of the PLL. A second compensation signal, externally generated, was added to the compensation signal of the PLL. By adding a compensation signal, which was not affected by the frequency response effects of the loop compensation, the loop tracking error is reduced. This technique enabled us to produce an output chirp signal that is a much closer replica of the scaled version of the reference signal. Furthermore, a type 1 PLL was chosen for improved transient response, compared to that of the type 2 PLL. This type of PLL requires an external compensation to obtain a finite steady state error when applying a frequency ramp to the input. The external compensation signal required to solve this issue was included in the second compensation signal mentioned above. Measurements for the PLL performance and the chirp generator performance were performed in the laboratory using a radar demonstrator. The experimental results show that the designed loop bandwidth was successfully achieved without significantly increasing the spurious signal level. The chirp generator measurements show a direct relationship between the bandwidth of the external compensation and the range resolution performance

Planet Formation at High Resolution: From Ground-Based Ex-AO to JWST

The field of exoplanets has grown rapidly over the last 10 years, especially with technological advances in radial velocity and transit photometry methods of discovery. While direct imaging is behind in discovery tallies it is still competitive in characterization of discovered exoplanets. Direct imaging from the ground is sensitive to a younger population of planets that are still glowing from the heat of formation. Probing planet formation with high angular resolution methods complements coronagraphic surveys from both the ground and space. Combining direct imaging designs with state of the art wavefront control and downstream instrumentation for, e.g., spectroscopy and polarimetry is essential for understanding planet formation and evolution processes. Ground-based instrumentation sets the stage for flying mature high contrast technologies on future space telescopes to obtain the most scientific yield. I present my contributions to the current direct imaging revolution, both for ground based instrumentation as well as preparing for the upcoming JWST mission. I will begin by describing an image-based algorithm for reducing interferometric data, and outline the factors that limit contrast for binary detection. I will present the results from commissioning and characterizing the Gemini Planet Imager's non-redundant mask, outlining the search space for high resolution observations with GPI. I will also discuss how new post-processing methods can remove biases from planet signals close-in that are buried under speckle noise. Lastly, I will show how interferometric methods contribute to wavefront sensing, which can serve as a backup mirror phasing method for JWST and which will be an essential component of future large space telescopes aimed at imaging exo-earths

Femtosecond optical parametric oscillator frequency combs for coherent pulse synthesis

Coherent pulse synthesis takes as its objective the piecewise assembly of a sequence of identical broadband pulses from two or more mutually-coherent sequences of narrowband pulses. The requirements for pulse synthesis are that the parent pulses share the same repetition frequency, are phase coherent and have low mutual timing jitter over the required observation time. The work carried out in this thesis explored the requirements for broadband coherent pulse synthesis between the multiple visible outputs of a synchronously pumped femtosecond optical parametric oscillator. A femtosecond Ti:sapphire laser was characterised and used to pump a PPKTP-based OPO that produced a number of second-harmonic and sum-frequency mixing outputs across the visible region. Using a novel lock-to-zero CEO stabilisation technique, broadband phase coherence was established between all the pulses on the optical bench, producing the broadest zero-offset frequency comb to date. Employing a common optical path for all the pulses provided common-mode rejection of noise, ensuring less than 150 attoseconds of timing jitter between the pulses over a 1 second observation window. The parent pulses were compressed and their relative delays altered in a quasi-common path prism delay line, allowing pulse synthesis at a desired reference plane

Radar systems for the water resources mission. Volume 4: Appendices E-I

The use of a scanning antenna beam for a synthetic aperture system was examined. When the resolution required was modest, the radar did not use all the time the beam was passing a given point on the ground to build a synthetic aperture, so time was available to scan the beam to other positions and build several images at different ranges. The scanning synthetic-aperture radar (SCANSAR) could achieve swathwidths of well over 100 km with modest antenna size. Design considerations for a SCANSAR for hydrologic parameter observation are presented. Because of the high sensitivity to soil moisture at angles of incidence near vertical, a 7 to 22 deg swath was considered for that application. For snow and ice monitoring, a 22 to 37 deg scan was used. Frequencies from X-band to L-band were used in the design studies, but the proposed system operated in C-band at 4.75 GHz. It achieved an azimuth resolution of about 50 meters at all angles, with a range resolution varying from 150 meters at 7 deg to 31 meters at 37 deg. The antenna required an aperture of 3 x 4.16 meters, and the average transmitter power was under 2 watts

Advances in Swept-Wavelength Interferometry for Precision Measurements

Originally developed for radar applications in the 1950s, swept-wavelength interferometry (SWI) at optical wavelengths has been an active area of research for the past thirty years, with applications in fields ranging from fiber optic telecommunications to biomedical imaging. It now forms the basis of several measurement techniques, including optical frequency domain reflectometry (OFDR), swept-source optical coherence tomography (SS-OCT), and frequency-modulated continuous-wave (FMCW) lidar. In this thesis, I present several novel contributions to the field of SWI that include improvements and extensions to the state of the art in SWI for performing precision measurements. The first is a method for accurately monitoring the instantaneous frequency of the tunable source to accommodate nonlinearities in the source tuning characteristics. This work extends the commonly used method incorporating an auxiliary interferometer to the increasingly relevant cases of long interferometer path mismatches and high-speed wavelength tuning. The second contribution enables precision absolute range measurements to within a small fraction of the transform-limited range resolution of the SWI system. This is accomplished through the use of digital filtering in the time domain and phase slope estimation in the frequency domain. Measurements of optical group delay with attosecond-level precision are experimentally demonstrated and applied to measurements of group refractive index and physical thickness. The accuracy of the group refractive index measurement is shown to be on the order of 10-6, while measurements of absolute thicknesses of macroscopic samples are accomplished with accuracy on the order of 10 nm. Furthermore, subnanometer uncertainty for relative thickness measurements can be achieved. For the case of crystalline silicon wafers, the achievable uncertainty is on the same order as the Si-Si bond length, opening the door to potential thickness profiling with single atomic monolayer precision. Thirdly, I demonstrate a novel implementation of SWI in the form of an SS-OCT system for performing quantitative measurements of spatially resolved refractive index contrast. This system relies on the depth-sectioning capability of SWI to isolate Fresnel reflectivity variations at an interface of interest within an optical sample. A motivating application for this quantitative index contrast measurement, volume lithography of photosensitive polymers, is also discussed in detail. This discussion includes the first demonstration of two-dimensional optical waveguide arrays fabricated in photosensitive polymers by means of holographic lithography

Development of an integrated microfluidic platform for oxygen sensing and delivery

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (p. 115-120).Treatment for end stage lung disease has failed to benefit from advances in medical technology that have produced new treatments for cardiovascular disease, certain cancers, and other major illnesses in recent years. As a result, end stage lung disease remains a devastating condition with few therapeutic options. To address the need for improved methods of respiratory life support, a novel technology was developed capable of generating oxygen directly from water present in blood plasma. This technology is intended to provide a self-contained, mobile oxygen supply suitable for implantation or extracorporeal oxygenation in support of an acute or chronically disabled lung. The core technology couples an optoelectronic metal oxide film with a microfluidic capillary network to facilitate oxygen exchange with flowing blood and replicate pulmonary capillary respiration. This thesis focuses on the optimization of this microfluidic capillary network with respect to hemocompatibility, mass transfer, and dissolved oxygen detection. Microfluidic capillary devices were fabricated from silicone rubber using multilayer soft lithography to create dense 2D networks of bifurcating channels. To quantify the effectiveness of mass transfer in various channel geometries under differing experimental conditions, a mathematical model of oxygen convection and diffusion was generated. A novel integrated optical oxygen sensor based on an oxygen-quenched luminescent dye was developed to detect oxygen concentrations within the microfluidic device. Mass transfer within the microfluidic oxygenator was characterized experimentally, employing the integrated optical sensor, and analytically, using the convective model.(cont.) Excellent agreement was found between experimental and analytical results. We conclude that the microfluidic platform achieves rapid and efficient diffusion of oxygen into a liquid medium, effectively mimicking the function of the pulmonary system. The combination of precise oxygen delivery and detection, integrated into a miniature device, is widely applicable both to the photolytic artificial lung and to a broader class of applications related to detection of chemical species in biological microdevices.by Adam P. Vollmer.S.M