41 |
Network Electrophysiology Sensor-On-A- ChipChen, Tsai Yuan 29 September 2011 (has links)
"
Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) bio-potential signals are commonly recorded in clinical practice. Typically, patients are connected to a bulky and mains-powered instrument, which reduces their mobility and creates discomfort. This limits the acquisition time, prevents the continuous monitoring of patients, and can affect the diagnosis of illness. Therefore, there is a great demand for low-power, small-size, and ambulatory bio-potential signal acquisition systems.
Recent work on instrumentation amplifier design for bio-potential signals can be broadly classified as using one or both of two popular techniques: In the first, an AC-coupled signal path with a MOS-Bipolar pseudo resistor is used to obtain a low-frequency cutoff that passes the signal of interest while rejecting large dc offsets. In the second, a chopper stabilization technique is designed to reduce 1/f noise at low frequencies. However, both of these existing techniques lack control of low-frequency cutoff.
This thesis presents the design of a mixed- signal integrated circuit (IC) prototype to provide complete, programmable analog signal conditioning and analog-to-digital conversion of an electrophysiologic signal. A front-end amplifier is designed with low input referred noise of 1 uVrms, and common mode rejection ratio 102 dB. A novel second order sigma-delta analog- to-digital converter (ADC) with a feedback integrator from the sigma-delta output is presented to program the low-frequency cutoff, and to enable wide input common mode range of ¡Ãƒâ€œ0.3 V. The overall system is implemented in Jazz Semiconductor 0.18 um CMOS technology with power consumption 5.8 mW from ¡Ãƒâ€œ0.9V power supplies. "
|
42 |
ADC and T2 response to radiotherapy in a human tumour xenograft modelLarocque, Matthew 11 1900 (has links)
A 9.4 T magnetic resonance imaging (MRI) system was used to evaluate the response of a human tumour xenograft model to radiation therapy. The apparent diffusion coefficient (ADC) and the transverse relaxation time (T2) of human glioblastoma multiforme (GBM) tumour xenografts in NIH-iii nude mice were measured before, and at multiple points after, treatment of the tumours with 200 kVp x-rays. The response was characterized as a function of a number of variables of interest in the clinical treatment of cancer with external beam radiation therapy.
Mean tumour ADC and T2 responses after single fractions of radiation were investigated, with measurements being made until 14 days after treatment. Single fraction doses ranged from 50 cGy to 800 cGy. Fractionated treatments were used to deliver 800 cGy in two or three fractions with fraction spacings of 24 or 72 hours. The role of hypoxia on ADC and T2 response was investigated by using an externally-applied, suture-based ligature to induce a state of reduced oxygenation in tumours during treatment, after which ADC and T2 were measured using serial MRI. Finally, tumours were dissected in order to provide insight into possible pathophysiological mechanisms explaining the observed responses. Tissue sections were prepared and reviewed by a pathologist.
This work adds to the body of literature describing tumour ADC and T2 response to anticancer therapy, and adds to the understanding of ADC and T2 response to radiation therapy in particular. This works supports that of others suggesting the use of ADC and T2 as potential biomarkers for tumour response to treatment. / Medical Physics
|
43 |
A Frequency-scalable 14-bit ADC for Low Power Sensor ApplicationsLiang, Joshua 15 February 2010 (has links)
In this thesis, a 14-bit low-power Analog-to-Digital Converter (ADC) is designed for sensor applications. Following on previous work, the ADC is designed to be frequency scalable by 1000 times from 1.67S/s to 1.67kS/s. To reduce power, class AB opamps are used. The design was fabricated in 0.18um CMOS and occupies an area of 0.35mm2. Operating at full-rate as a Delta-Sigma modulator, the ADC achieves 91.8dB peak SNDR while consuming 83uW. In incremental mode, the ADC powers off periodically to achieve frequency scalability, maintaining 84.7dB to 89dB peak SNDR while operating from 1.67S/s to 1.67kS/s.
|
44 |
A Frequency-scalable 14-bit ADC for Low Power Sensor ApplicationsLiang, Joshua 15 February 2010 (has links)
In this thesis, a 14-bit low-power Analog-to-Digital Converter (ADC) is designed for sensor applications. Following on previous work, the ADC is designed to be frequency scalable by 1000 times from 1.67S/s to 1.67kS/s. To reduce power, class AB opamps are used. The design was fabricated in 0.18um CMOS and occupies an area of 0.35mm2. Operating at full-rate as a Delta-Sigma modulator, the ADC achieves 91.8dB peak SNDR while consuming 83uW. In incremental mode, the ADC powers off periodically to achieve frequency scalability, maintaining 84.7dB to 89dB peak SNDR while operating from 1.67S/s to 1.67kS/s.
|
45 |
A frequency-translating hybrid architecture for wideband analog-to-digital convertersJalali Mazlouman, Shahrzad 05 1900 (has links)
Many emerging applications call for wideband analog-to-digital converters and some require medium-to-high resolution. Incorporating such ADCs allows for shifting as much of the signal processing tasks as possible to the digital domain, where more flexible and programmable circuits are available. However, realizing such ADCs with the existing single stage architectures is very challenging. Therefore, parallel ADC architectures such as time-interleaved structures are used. Unfortunately, such architectures require high-speed high-precision sample-and-hold (S/H) stages that are challenging to implement.
In this thesis, a parallel ADC architecture, namely, the frequency-translating hybrid ADC (FTH-ADC) is proposed to increase the conversion speed of the ADCs, which is also suitable for applications requiring medium-to-high resolution ADCs. This architecture addresses the sampling problem by sampling on narrowband baseband subchannels, i.e., sampling is accomplished after splitting the wideband input signals into narrower subbands and frequency-translating them into baseband where identical narrowband baseband S/Hs can be used. Therefore, lower-speed, lower-precision S/Hs are required and single-chip CMOS implementation of the entire ADC is possible.
A proof of concept board-level implementation of the FTH-ADC is used to analyze the effects of major analog non-idealities and errors. Error measurement and compensation methods are presented. Using four 8-bit, 100 MHz subband ADCs, four 25 MHz Butterworth filters, two 64-tap FIR reconstruction filters, and four 10-tap FIR compensation filters, a total system with an effective sample rate of 200 MHz is implemented with an effective number of bits of at least 7 bits over the entire 100 MHz input bandwidth.
In addition, one path of an 8-GHz, 4-bit, FTH-ADC system, including a highly-linear mixer and a 5th-order, 1 GHz, Butterworth Gm-C filter, is implemented in a 90 nm CMOS technology. Followed by a 4-bit, 4-GHz subband ADC, the blocks consume a total power of 52 mW from a 1.2 V supply, and occupy an area of 0.05 mm2. The mixer-filter has a THD ≤ 5% (26 dB) over its full 1 GHz bandwidth and provides a signal with a voltage swing of 350 mVpp for the subsequent ADC stage.
|
46 |
A 43mW single-channel 4GS/s 4-bit flash ADC IN 0.18um CMOSSheikhaei, Samad 05 1900 (has links)
The continued speed improvement of serial links and appearance of new communication technologies, such as ultra wideband (UWB), have introduced increasing demands on the speed and power specifications of high speed low to medium resolution analog to digital converters (ADCs). While multi channel ADCs can achieve high speeds, they often require extensive and costly post fabrication calibration.
A single channel 4 bit flash ADC, suitable for abovementioned or similar applications, implemented entirely using current mode logic (CML) blocks, is presented. CML implementation allows for high sampling rates, while typically providing low power consumption at high speeds. To improve the conversion rate, both the analog (comparator array) and the digital (encoder) parts of the ADC are fully pipelined. Furthermore, the logic functions in the encoder are reformulated to reduce wire crossings and delay and to equalize the wires lengths in the layout. To keep the design simple, inductors are avoided. As a result, a compact design with small wire parasitics is achieved. Moreover, some geometric layout techniques, including a common centroid layout for the resistor ladder, are introduced to reduce the effect of mismatches to eliminate the use of digital calibration.
The ADC is designed and fabricated in 0.18um CMOS and operates at 4GS/s. It achieves an effective number of bits (ENOB) of 3.71 (3.14, 2.75) for a 10MHz (0.501GHz, 1.491GHz) signal sampled at 4GS/s (3GS/s, 3GS/s). Differential/integral nonlinearity (DNL/INL) errors are between +/-0.35LSB and +/-0.26LSB, respectively. The ADC consumes 43mW from a 1.8V supply and occupies 0.06mm2 active area.
Due to the use of CML circuits, the ADC achieves the highest speed reported for a single channel 4 bit ADC in a 0.18um CMOS technology. It also reports the best power performance among the 4-bit ADCs with similar or higher speeds. The active area is also among the smallest reported.
In addition, in this thesis, the signal to noise ratio (SNR) of an ADC is formulated in terms of its INL performance. The related formulas in the literature are not accurate for low resolution ADCs, and yet they do not take the input waveform into account. Two standard waveforms, ramp and sinusoid, are considered here. The SNR formulas are derived and confirmed by simulation results.
|
47 |
A 10-bit 30-MS/s Pipeline ADC for DVB-H Receiver Systems and Mixed-Voltage Tolerant I/O Cell DesignChang, Tie-Yan 11 July 2007 (has links)
The first topic of this thesis proposes a 10-bit, 30 Msample/s pipeline analog-to-digital converter (ADC) suitable for digital video broadcasting over handheld (DVB-H) systems. The ADC is based on the 1.5-bit-per-stage pipeline architecture. The proposed design is implement- ed by 0.18 um CMOS technology. The input range is 2 V peak-to-peak differential signals, and the post-layout simulation result shows that the spurious-free dynamic range (SFDR) is 57.85 dBc with a full-scale sinusoidal input at 700 KHz. The maximum power consumption is 37 mW given a 3.3 V power supply. The core area is 0.27 mm2.
The second topic is to propose a fully mixed-voltage-tolerant I/O cell implemented using typical CMOS 2P4M 0.35 um process. Unlike traditional mixed-voltage-tolerant I/O cell, the proposed design can transmit and receive the digital signals with voltage levels of 5/3.3/1.8 V. By using stacked PMOS and stacked NMOS at the output stage and a voltage level converter providing appropriate control voltages for the gates of the stacked PMOS, the gate-oxide overstress and hot-carrier degradation are avoided. Moreover, gate-tracking and floating N-well circuits are used to remove the undesirable leakage current paths. The maximum transmitting speed of the proposed I/O cell is 103/120/84 Mbps for the supply voltage of I/O cell at 5/3.3/1.8 V, respectively, given the load of 20 pF.
|
48 |
Influence of ADC Nonlinearity on the Performance of an OFDM ReceiverSAWADA, Manabu, OKADA, Hiraku, YAMAZATO, Takaya, KATAYAMA, Masaaki 12 1900 (has links)
No description available.
|
49 |
Design of RF/IF analog to digital converters for software radio communication receiversThandri, Bharath Kumar 17 September 2007 (has links)
Software radio architecture can support multiple standards by performing analogto-
digital (A/D) conversion of the radio frequency (RF) signals and running
reconfigurable software programs on the backend digital signal processor (DSP). A
slight variation of this architecture is the software defined radio architecture in which the
A/D conversion is performed on intermediate frequency (IF) signals after a single down
conversion.
The first part of this research deals with the design and implementation of a
fourth order continuous time bandpass sigma-delta (CT BP) C based on LC filters
for direct RF digitization at 950 MHz with a clock frequency of 3.8 GHz. A new ADC
architecture is proposed which uses only non-return to zero feedback digital to analog
converter pulses to mitigate problems associated with clock jitter. The architecture also has full control over tuning of the coefficients of the noise transfer function for obtaining the best signal to noise ratio (SNR) performance. The operation of the architecture is examined in detail and extra design parameters are introduced to ensure robust operation of the ADC. Measurement results of the ADC, implemented in IBM 0.25 µm SiGe BiCMOS technology, show SNR of 63 dB and 59 dB in signal bandwidths of 200 kHz
and 1 MHz, respectively, around 950 MHz while consuming 75 mW of power from ±
1.25 V supply.
The second part of this research deals with the design of a fourth order CT BP ADC based on gm-C integrators with an automatic digital tuning scheme for IF
digitization at 125 MHz and a clock frequency of 500 MHz. A linearized CMOS OTA
architecture combines both cross coupling and source degeneration in order to obtain
good IM3 performance. A system level digital tuning scheme is proposed to tune the
ADC performance over process, voltage and temperature variations. The output bit
stream of the ADC is captured using an external DSP, where a software tuning algorithm
tunes the ADC parameters for best SNR performance. The IF ADC was designed in
TSMC 0.35 µm CMOS technology and it consumes 152 mW of power from ± 1.65 V
supply.
|
50 |
Low power VCO-based analog-to-digital conversionGupta, Amit Kumar 08 September 2015 (has links)
This dissertation presents novel two stage ADC architecture with a VCO based second stage. With the scaling of the supply voltages in modern CMOS process it is difficult to design high gain operational amplifiers needed for traditional voltage domain two-stage analog to digital converters. However time resolution continues to improve with the advancement in CMOS technology making VCO-based ADC more attractive. The nonlinearity in voltage-to-frequency transfer function is the biggest challenge in design of VCO based ADC. The hybrid approach used in this work uses a voltage domain first stage to determine the most significant bits and uses a VCO based second stage to quantize the small residue obtained from first stage. The architecture relaxes the gain requirement on the the first stage opamp and also relaxes the linearity requirements on the second stage VCO. The prototype ADC built in 65nm CMOS process achieves 63.7dB SNDR in 10MHz bandwidth while only consuming 1.1mW of power. The performance of the prototype chip is comparable to the state-of-art in terms of figure-of-merit but this new architecture uses significantly less circuit area. / text
|
Page generated in 0.028 seconds