M.N. Ericson

A multi-channel ADC for use in the PHENIX detector

A custom CMOS analog to digital converter was designed and a prototype 8-channel ADC ASIC was fabricated in a 1.2 /spl mu/m process. The circuit uses a Wilkinson-type architecture which is suitable for use in multi-channel applications such as the PHENIX detector. The ADC design features include a differential positive-ECL input for the high speed clock and selectable control for 11 or 12-bit conversions making it suitable for use in multiple PHENIX subsystems. Circuit topologies and ASIC layout specifics, including power consumption, maximum clock speed, INL, and DNL are discussed. The ADC performed to 11-bit accuracy.

In vivo application of a minimally invasive oximetry based perfusion sensor

Pulse oximetry is an optical technique based on the differences in absorption of blood oxygenated and deoxygenated hemoglobin, which can be used for sensing blood flow in tissue. The inadequacy of current systemic blood flow measurements to detect changes in the local perfusion of transplanted and/or diseased organs has led us to develop a novel micro-sensor for this purpose. For this paper, we present in vivo results from a preliminary study performed to quantify the effectiveness and SNR of the sensor using a rat model. The results indicate that the sensor is able to detect changes in perfusion to the target organ in correlation to a standard laser-Doppler reference signal.

Monolithic circuits for the WA98 lead class calorimeter

Two monolithic circuits developed for readout of a 10000 element lead glass calorimeter are described. The first contains 8 channels with each channel comprising a charge integrating amplifier, two output amplifiers with gains of one and eight, a timing filter amplifier and a constant fraction discriminator. This IC also contains a maskable, triggerable calibration pulser and circuits needed to form 2 by 2 and 4 by 4 energy sums used to provide trigger signals. The second IC is a companion to the first and contains 16 analog memory channels with 16 cells each, eight time-to-amplitude converters and a 24-channel analog-to-digital converter. The use of the analog memories following the integration function eliminates the need for delay cables preceding it. Characterizations of prototypes are reported, and features included to ease integration of the ICs into a readout system are described.<<ETX>>

Implantable sensor for blood flow monitoring after transplant surgery

A limited number of techniques are employed in clinical medicine for regional tissue perfusion assessment. These methods are marginally effective and are not well suited for implantation due to the inability to miniaturize the associated technologies. Consequently, no standardized techniques exist for real-time, continuous monitoring of organ perfusion following transplantation. In this paper, a brief overview of the relevant clinical techniques employed for regional tissue perfusion assessment is given with particular emphasis on post-surgical monitoring of transplanted organs. The ideal characteristics for a perfusion monitoring system are discussed and the development of a new, completely implanted local tissue monitoring system is summarized. In vivo and in vitro data are presented that establish the efficacy of this new technology, which is a photonics-based sensor system uniquely suited for continuous tissue monitoring and real-time data reporting. The suitablity of this sensor technology for miniaturization, which enables implantation for monitoring localized tissue perfusion, is discussed.

Processing of pulse oximeter data using discrete wavelet analysis

A wavelet-based signal processing technique was employed to improve an implantable blood perfusion monitoring system. Data was acquired from both in vitro and in vivo sources: a perfusion model and the proximal jejunum of an adult pig. Results showed that wavelet analysis could isolate perfusion signals from raw, periodic, in vitro data as well as fast Fourier transform (FFT) methods. However, for the quasi-periodic in vivo data segments, wavelet analysis provided more consistent results than the FFT analysis for data segments of 50, 10, and 5 s in length. Wavelet analysis has thus been shown to require less data points for quasi-periodic data than FFT analysis making it a good choice for an indwelling perfusion monitor where power consumption and reaction time are paramount.

A wide-range logarithmic electrometer with improved accuracy and temperature stability

A seven-decade temperature-compensated logarithmic electrometer is presented. The amplifier is designed to a dynamic range of 1 pA to 10 mu A. Temperature compensation is accurately achieved by using an array of four matched monolithic bipolar transistors and straightforward postprocessing techniques. Use of this method results in >

Development of an implantable oximetry-based organ perfusion sensor

A sensor system enabling real-time monitoring of organ perfusion following transplantation is presented. This system uses a three wavelength oximetry-based approach. The instrument is intended for implantation at the organ site during transplantation to provide real-time reporting of the perfusion status of the tissue for 7-10 days following the procedure. Data is transmitted from the sensor to a localized receiver using direct sequence spread spectrum techniques at 916 MHz. In this paper, the sensing method and associated electronics implementation are presented. The present status of system miniaturization is summarized along with plans for future miniaturization efforts. Preliminary sensor data is presented demonstrating the efficacy of the technique.

A low-power, CMOS peak detect and hold circuit for nuclear pulse spectroscopy

A low-power CMOS peak detecting track and hold circuit optimized for nuclear pulse spectroscopy is presented. The circuit topology eliminates the need for a rectifying diode, reducing the effect of charge injection into the hold capacitor, incorporates a linear gate at the input to prevent pulse pileup, and uses dynamic bias control that minimizes both pedestal and droop. Both positive-going and negative-going pulses are accommodated using a complementary set of track and hold circuits. Full characterization of the design fabricated in 1.2 /spl mu/m CMOS including dynamic range, integral nonlinearity, droop rate, pedestal, and power measurements is presented. The circuit operates with only 250 /spl mu/w for input pulses with 7 /spl mu/s peaking time. Power consumption was increased to 750 /spl mu/w for driving off-chip and test system capacitances. Analysis and design approaches for optimization of operational characteristics are also discussed. >

Charge sensitive preamplifier and pulse shaper using CMOS process for germanium spectroscopy

The authors have developed a low noise, low power charge sensitive amplifier and pulse shaping circuit. The application is for a double-sided germanium strip detector, nominally providing 50 independent spectroscopy channels. An array of these detectors would provide significant improvements in imaging, spectroscopy and sensitivity for space-based gamma-ray astronomy. The key features of these electronics are low noise, very low power, and a small footprint per channel. Performance of the first circuit is in good agreement with simulations, with /spl sim/205e noise rms (0 pF), and 3 mW/channel power consumption. The dynamic range is 0-3.3 MeV (germanium) with a linearity of /spl plusmn/0.6%. Performance of this prototype device is discussed. >

Time-domain noise analysis of linear time-invariant and linear time-variant systems using MATLAB and HSPICE

A custom simulation tool that combines HSPICE and MATLAB to enable time-domain noise analysis is reported. The simulation technique is based on computing the statistics of a random process by ensemble averaging and is applicable to both linear time-invariant (LTI) and linear time-variant (LTV) systems. MATLAB is used to generate a set of representative noise signals, which are imported into HSPICE for simulation. Once the simulations are complete the results are read back into MATLAB and ensemble statistics are calculated. The MATLAB-generated noise signals have a user-defined white-noise floor and flicker-noise corner frequency and thus are suitable for modeling a wide variety of electronic components, including CMOS transistors and resistors. Simulation results of the time-dependent output noise of a gated integrator and the timing resolution of a gated integrator/comparator detector are presented to highlight both the utility and the versatility of the tool.