Linga Reddy Cenkeramaddi

Jitter analysis of general charge sampling amplifiers

In this paper we present a simple analytical model for the estimation of signal-to-noise ratio (SNR) due to clock jitter for a general charge sampling amplifier. The proposed analytical model is compared with a previously published more complex model. Finally, we compare charge sampling and voltage sampling in terms of SNR due to clock jitter

Analysis and Design of a 1V Charge Sampling Readout Amplifier in 90nm CMOS for Medical Imaging

In this paper, we present the analysis and design of a charge sampling amplifier (CSA) in 90 nm CMOS for medical imaging applications. The CSA is designed based on a 1 V CMOS folded cascode operational transconductance amplifier (OTA) with lead compensation. The OTA achieves a DC gain of 45-dB and a unity gain frequency of 1.3 GHz at a power consumption of 200 muW. Performance of the charge sampling amplifier is investigated when it is connected to a single capacitive micro machined ultrasound transducer (CMUT). The proposed CSA front end architecture for ultrasound imaging achieves a transfer gain of 19 dB from CMUT signal source to the output of the CSA (across feedback capacitor) with sampling simultaneously.

Self-biased charge sampling amplifier in 90nm CMOS for medical ultrasound imaging

In this paper, we present the analysis and design of a self-biased single-ended charge sampling amplifier (CSA) in 90nm CMOS for catheter based intravenous ultrasound imaging applications. The proposed CSA is based on a 1V single-ended CMOS inverter-based cascode amplifier. The amplifier achieves a DC gain of 43.7 dB and a unity gain frequency of 1.37 GHz at a power consumption of 385 μW at 37°C - nominal temperature of human body with typical-typical (TT) models defined in the 90nm CMOS technology used for this design. Performance of the self-biased CSA is studied by connecting a single Capacitive Micro machined Ultrasound Transducer (CMUT) to it.

P4M-6 A Low Noise Capacitive Feedback Analog Front-End for CMUTs in Intra Vascular Ultrasound Imaging

In this paper, we present the capacitive feedback analog front-end for intra vascular ultrasound (IVUS) imaging as opposed to the conventional resistive feedback analog front-ends. In our proposed capacitive feedback architecture, floating input node of the amplifier is dynamically biased during the transmit mode of the CMUTs (capacitive micromachined ultrasound transducers). During the reception mode, the biased voltage at the floating input node of the amplifier is stored on the gate of input transistor of the amplifier. A high voltage pulser circuit with small output capacitance is integrated on-chip with the proposed low-noise capacitive feedback receiver. The proposed capacitive feedback analog front-end circuit is designed using the 0.35 mum high-voltage CMOS technology library of Austria Microsystems Corporation. Based on post- layout simulation results, we were able to achieve an overall noise figure of less than 2 dB with the proposed capacitive feedback analog front end for the amplification of signals generated by a 100times200 mum2 CMUT array element.

1V transimpedance amplifier in 90nm CMOS for medical ultrasound imaging

In this paper we present the measurement results of a 1V transimpedance amplifier designed in a 90nm CMOS technology as an analog front-end for Capacitive Micro machined Ultrasound Transducers (CMUTs) for medical ultrasound imaging. The proposed amplifier is designed to amplify the signals from 15MHz to 45MHz with a center frequency of 30MHz. The measurements show that the proposed amplifier achieves a voltage gain of 15.5 dB, an output noise power spectral density of 0.0497 (µV)/SQRT(Hz) at a center-frequency of 30 MHz, and a total harmonic distortion of −28.8 dB, at 400mV p-p output voltage at 30 MHz input signal frequency. It draws only 450 µA current from a 1-V power supply. The proposed transimpedance amplifier was fabricated in a 90-nm CMOS technology as it is intended for intravenous medical ultrasound imaging, which demands smaller area for the front-end amplifiers. Area measured to be about 26 µm × 26 µm only per amplifier.

Front-end IC design for intravascular ultrasound imaging

Capacitive micromachined ultrasonic transducers (cMUT) technology is a new trend for intravascular ultrasound (IVUS) imaging. Large bandwidth, high sensitivity and compatibility to CMOS processes makes the cMUT a better choice compared to the conventional piezoelectric transducer. To exploit the merits of cMUT technology, an accurately designed front end circuit is required. The circuit functions as an output pulse driver for the generation of the acoustic signal and buffers the return echo. For an accurate evaluation before tape-out, the circuit has to be simulated using the post-layout extracted netlist of the IC with the electrical equivalent circuit that models the transducer pulse-echo behavior. In this paper, we present two different designs of front-end IC for 2D cMUT arrays that can be used for intravascular ultrasound imaging system. To simulate the response of the front-end circuit, we first developed a pulse-echo model for an array element using Mason Equivalent Circuit. The model is then combined with the front-end circuit using Cadence Spectre. The simulation results are verified by comparing them to experimental data obtained from the manufactured front-end IC. The results show that the front-end circuit tested with the equivalent circuit model of the cMUT elements is promising for the optimization of the overall system performance before manufacturing.

Spectrum cartography using adaptive radial basis functions: Experimental validation

In this paper, we experimentally validate the functionality of a developed algorithm for spectrum cartography using adaptive Gaussian radial basis functions (RBF). The RBF are strategically centered around representative centroid locations in a machine learning context. We assume no prior knowledge about neither the power spectral densities (PSD) of the transmitters nor their locations. Instead, the received signal power at each location is estimated as a linear combination of different RBFs. The weights of the RBFs, their Gaussian decaying parameters and locations are jointly optimized using expectation maximization with a least squares loss function and a quadratic regularizer. The performance of adaptive RBFs based spectrum cartography is shown through measurements using a universal software radio peripheral, a customized node and LabView framework. The obtained results verify the ability of adaptive RBF to construct spectrum maps with an acceptable performance measured by normalized mean square error (NMSE).

Radio measurements on a customized software defined radio module: A case study of energy detection spectrum sensing

In this paper, we developed a software defined radio (SDR) system for implementing energy detection spectrum sensing. The SDR module can be used for a wide range of applications. The use of the SDR module is motivated by its high interoperability, availability for relatively cheaper prices and being software independent. Energy detection for cognitive radios is chosen for its simplicity and popularity. However, it is chosen as a representative for a very wide range of measurements and algorithms that can be implemented in the SDR. We have used probabilities of detection and false alarm with the receiver operating characteristics (ROC) curves as performance metrics for the implemented energy detector. We have benchmarked our findings with an energy detector implemented on a Universal Software Radio Peripheral from National Instruments (NI-USRP). Measurements results for the SDR module are in close agreement with the results from NI-USRP using the same setup and also with the theoretical results.

Mixed signal system design (A project based course)

This paper describes an undergraduate 10 ECTS course in the design of analog and digital microelectronic circuits based on a project. This is offered for the students of Electronics engineering in their 3rd semester of the 6-semester bachelor-programme. The emphasis is given on the mixed signal aspects of the system design. From the project, students get practical experience in the mixed signal system design.

BGO front-end electronics and signal processing in the MXGS instrument for the ASIM mission

This paper presents the Bismuth Germanate Oxide (BGO) front-end electronics design and signal processing in Modular X- and Gamma ray sensor (MXGS) instrument onboard the Atmosphere Space Interaction Monitor (ASIM) mission, funded by the European Space Agency. University of Bergen is responsible for the design and development of the detector layers and readout electronics for the MXGS instrument. The principal objective of the instrument is to detect Terrestrial Gamma ray Flashes (TGFs), which are related to thunderstorm activity. The digital pulse processing scheme used in the MXGS BGO detector gives it a significantly higher rate capability than what has been achieved in other instruments used in the study of terrestrial gamma flashes. The front-end electronics for the BGO detector layer in MXGS system also uses fewer components compared to conventional analog front-ends for BGO detectors, thereby increasing its reliability and projected lifetime in the harsh space environment. The MXGS instrument is expected to see about 1000 TGFs in a time period of one year.