<p>This paper reports on the modeling and simulation of a continuous-time delta-sigma analog to digital converter (ADC) in VHDL AMS. The ADC is intended for use in a microcontroller and is therefore underlying restrictions on power consumption. Continuous-time delta-sigma architectures are well known for their good low-power capabilities compared to discrete-time realizations. This is due to their reduced demands to the gain bandwidth product (GBW) of the internal amplifiers in the ADCs. Continuous-time ADCs often operate with GBWs in the range of the sampling frequency, fs. The ADC presented in this work is also employing a previously reported compensation technique which ideally allows the GBW to be reduced further >20 times of this. Considering that the current drain in the amplifiers usually is proportional with GBW, this could be a promising power saving technique. The work focuses on the development of two similar models of a 2-order continuous-time delta-sigma ADC in VHDL-AMS, where one of the ADCs is using the compensation technique. The main purpose is to see how the compensated ADC is affected by nonidealities such as GBW-variation, finite amplifier gain, RC-product variation, excess loop delay and finite DAC slew rate compared to the performance of the noncompensated ADC. The required accuracy for the modeled ADCs is 62dB Signal to Noise and Distortion Ratio (SNDR), thus an appropriate oversampling ratio (OSR) also must be found. The simulations show that the compensated ADC has similar performance as the noncompensated ADC operating with GBW=10*fs when subject to the different nonidealities. With an OSR=64 it stays within the accuracy specification for GBWs >= 0.05*fs This is however only valid if actual GBW stays within +-40% of the GBW compensated for. For larger deviations, especially lower GBW values, the SNDR drops rapidly. It is also shown that the internal signal swing in the ADC is reduced for low GBW values. This may limit the practical achievable SNDR when subject to circuit noise. If these potential drawbacks are circumvented, the compensation technique could lead to a further decrease of the power consumption in continuous-time delta-sigma ADCs.</p>

<p>The goal of this Master Thesis is to study shared radio resources among users with different services requirements. The analyzed properties of the wireless connection are fairness, throughput and delay for users demanding different services and QoS requirements. Four scheduling algorithms are used for allocating system resources. Two of them, Max Rate and Round Robin, are used as references to analyze throughput and fairness respectively. The other two algorithms, Proportional Fair Scheduling and Rate Craving Greedy, exploit the idea of multiuser diversity improving the throughput without comprising fairness. Different fading radio channel models are investigated, but only urban environments and pedestrian users are simulated in this report. OFDM has been the technique used to transmit signals over the wireless channel. The performance of these algorithms is analyzed and compared through MATLAB computer simulations.</p>

<p>A 64-modulus prescaler operating at 5.8 GHz has been designed in a 0.18 μm CMOS process. The prescaler uses a four-phase high-speed ÷4 circuit at the input, composed of two identical cascaded ÷2 circuits implemented in pseudo-NMOS. The high-speed divider is followed by a two-bits phase switching stage, which together with the input divider forms a ÷4/5/6/7 circuit. The phase switching stage is mostly implemented in complementary CMOS. After this follows four identical ÷2/3 cells with local feedback, also implemented in complementary CMOS. Other architectural approaches are also described and tried out. An architecture based solely the ÷2/3 cells with local feedback is presented. The ÷2/3 cells were implemented and simulated, and worked up to 2.3 GHz. An alternative high-speed divider based on an inverter ring interrupted by transmission gates is also described. Simulations showed that a divider using pseudo-NMOS inverters and CMOS transmission gates operated well and gave out four signals evenly spaced in phase at a input frequency of 4.8 GHz.</p>

<p>Software defined radio (SDR) is an emerging trend of radio technology. The idea is basically to move software as close to the antenna of a radio system as possible, to improve flexibility, adaptability and time-to-market. This thesis covers the description of a DSP architecture especially optimized for modulation / demodulation algorithms of low-complexity, low-power radio standards. The DSP allows software processing of these algorithms, making SDR possible. To make the DSP competitive to traditional ASIC modems, tough constraints are given for area and power consumption. Estimates done to indicate the power consumption, area and computational power of the DSP, shows that a software implementation of the studied physical layer should be possible within the given constraints.</p>

<p>This work investigates whether in vivo magnetic resonance spectroscopy (MRS) and diffusion-weighted magnetic resonance imaging (DW-MRI) can be used for non-invasive monitoring of treatment response in an experimental tumor model. Twenty-nine nude mice with colorectal adenocarcinoma HT29 xenografts on each flank were included into 2 separate experiments. In the first experiment control tumors were compared to tumors irradiated with 15 Gy at Day 2. MR baseline values were established at Day 1 followed by 4 post-treatment MR examinations. Mice were sacrificed for histological response evaluation and high-resolution ex vivo magic angle spinning (HR-MAS) MRS of tumor tissue samples for correlation with in vivo MR data. The second experiment included 3 groups recieving combined chemoradiation therapy; Control group, Capecitabine (359 mg/kg daily Day 1 - Day 5) group and Capecitabine (359 mg/kg daily Day 1 - Day 5) + Oxaliplatin (10 mg/kg at Day 2) group. All left-sided tumors were irradiated with 15 Gy at Day 2. Three repeated MR examinations were compared to the MR baseline values established at Day 1. After MR examinations the mice were sacrificed for histological response evaluation. The choice of chemoterapy was based on a clinical patient study currently running at Rikshospitalet-Radiumhospitalet HF, the LARC-RRP (Locally Advanced Rectal Cancer - Radiation Response Prediction) study. In Experiment 1, localized 1H MR spectra were acquired at short (35 ms) and long (144 ms) echo times (TEs) using a single-voxel technique. The metabolite choline is related to tumor growth. The choline peak area relative to the unsuppressed 35 ms TE water area in the same voxel, i.e. the normalized choline ratio, was assessed in all MRS examinations. For both TEs, the choline ratio increased after irradiation, followed by a decrease and a renewed increase 12 days after irradiation. In Experiment 1, statistically significant differences at the 0.1 level were observed between the choline ratios at Day 5 and Day 12 (p = 0.068) for short TE and between the ratios at Day 3 and Day 8 (p = 0.05) for long TE. The change in choline ratio was in accordance with the tumor necrotic fraction (NF) found in histological analyses. Principal component analysis (PCA) revealed a correlation between the score values of ex vivo HR-MAS MR spectra and necrosis. This suggests a correlation between ex vivo and in vivo MRS. In both experiments, the diffusion in the HT29 xenografts varied during treatment. There was a correlation between the amount of necrosis in tumor and the calculated apparent diffusion coefficient (ADC) obtained from DW-MRI examinations. In Experiment 1, statistically significant differences at the 0.1 level were observed between the ADCs at Day 3 and Day 5 (p = 0.05), between Day 5 and Day 12 (p = 0.068), and between Day 8 and Day 12 (p = 0.068). The HT29 xenografts responded to treatment with an initial increase of necrosis due to the short-term effect of treatment, stimulating development of fibrosis. In accordance to the change in choline and ADC, the level of necrosis increased 8 - 12 days after start of treatment, which might correspond to the long-term effect of treatment. The findings in this work shows that in vivo MRS and DW-MRI can be used for non-invasive monitoring of treatment response in an experimental tumor model. This suggests that in vivo MRS and DW-MRI could yield important information about a tumors response to therapy.</p>

<p>This thesis is divided into two parts, the design of a practical first order open loop sigma-delta modu- lator using discrete components, and simulation of a third order OLSD ADC to investigate the consequences of circuit imperfections - and determining circuit requirements if the ADC should be used in a GSM system. The practical modulator is designed as a first order OLSD ADC, with standard discrete components such as operational amplifiers and switches, and a microcontroller with a built in ADC. The practical circuit uses surface mount capacitors with a tolerance of 20%, resulting in poor matching and inaccurate behavior of the modulo integrator. Despite the poor matching, the OLSD ADC shows a distinct noise shaping, with a slope of about 20dB per decade. The quantization noise is not the dominating noise source in the circuit, and the quantizer resolution must to be set to four bits or less to achieve any improvement in performance over the standard ADC. The third order modulator is modeled and simulated at a behavior level using VHDL-AMS. The ideal circuit confirms the results from the preliminary project [12], where the quantizer resolution had to be equal to or larger than the modulator order to obtain proper noise shaping. The simulations shows that the ideal third order modulator with a four bit quantizer can achieve a SNR of 88:51dB, and an ENOB of 13:78bits within a 200kHz band. The third order modulator is simulated with circuit imperfections to determine the effect of these when there is no feedback present. Introducing finite gain in the integrators results in harmonic distortion at the output. This harmonic distortion is a result of leakage of the internal reset signal in the integrators. By setting the gain in all three integrators to 2OSR = 42dB, the SNR of the third order modulator sinks to 71:74dB. The gain in the ¯rst integrator is increased to 60dB, and the SNR raises to 84:52dB. The first integrator is the most crucial to the performance of the modulator, as is the case for conventional sigma-delta ADCs. The circuit is also simulated with capacitance mismatch and comparator o®set in the modulo integrator. These two imperfections results in the same error - the output voltage from the integrator di®ers from the ideal case. Simulations show that the total voltage error should be significantly less than 0.5VLSB to obtain the noise shaping. If the integrator output error is too large, the noise shaping will totally disappear. In general, it has been proved that the OLSD modulator with modulo integrators works as intended, the quantization noise is shaped like in conventional sigma-delta modulators. The modulator is very sensitive to capacitor mismatch and parasitics. The e®ect of these capacitor imperfections will increase as the quantizer resolution increase, because the error will cover more units of VLSB. It is important to minimize these capacitor effects, as increased quantizer resolution will allow a greater input signal swing.</p>

<p>In the later years the scientist community has bin investigating the possibility of using zoo plankton as a commercial resource. It is therefore of interest to investigate the size distribution and abundance of zoo plankton. NTNU has for this purpose developed an Acoustical plankton recorder or APR, for determination of the size distribution and abundance of plankton. The system utilizes three frequencies namely 200 kHz, 710 kHz and 1 MHz for the task. A specific kind of plankton called Callanus finmarchicus which has primarily a size range from 1-3 mm is considered the most interesting one since it has a large population in the Norwegian Sea. In this report the signal processing from the “raw” measured values with the APR to the calculated distribution of plankton is described. The following steps has bin carried out in the signal processing: • First of the measured values are processed with an exact “Time Varied Gain Function” or TVG. This function will compensate for the range from the APR to the target by information about the absorption, the range, the pulse-length and the band-width of the receiver. The exact TVG function has bin used since the ordinary TVG function will give a positive bias for ranges below 10 meters • After the TVG function the Echo Integrator equation with noise subtraction is used. This will reduce the effect of noise in the measurements and improve the linearity principle. • At the end inversion is carried out. Two different algorithms are used in the purpose of the inversion, namely the “Least Square non Negative” and the GA algorithm. The inversion will try to find the best fit between the measured data and the mathematically modelled plankton distribution and thereby calculating the size distribution and abundance of plankton. The echo integration with noise subtraction works by calculating the energy in the measurement over a series of samples contributing to a distance in the measurement in active mode. The samples contributing to the same distance is then used to calculate the energy in passive mode and this value is then subtracted from the energy in active mode. The accuracy of the method is dependent on the number of samples used giving better results with an increasing number of samples. Therefore the method has to be used with consideration to the resolution needed in the measurements. The “Least Square non Negative” and the GA algorithm are compared by testing them one the same synthetic data. The result is that in some cases the “Least Square non Negative” seems to work better but in other cases the GA algorithm gives the best results. Both methods has got problems in determining the abundance of smaller plankton when large plankton or potentially air bubbles are present.</p>

<p>This study will focus on strain induced by thermal history and thickness on antiferromagnetic epitaxial LaFeO3(110) thin films grown on Nb:SrTiO3(001) substrates. Lattice mismatching between film and substrate induce strain in the film lattice during growth of the film. This strain can be relaxed by thermal treatment after growth and may show tendencies in the domain size, shape and distribution related to strain. Thin films are grown in different thicknesses by rf magnetron sputtering and selected films are relaxed by thermal anneal treatment. The samples are investigated in room temperature and in heating experiments to obtain images of antiferromagnetic domain contrast along the L2 and L3 absorbtion egde of Fe by XMLD spectromicroscopy. Size of domains areas and contrast level are measured and related to the strain in the thin films. Averaged spectra of L2 absorbtion edge antiferromagnetic contrast showed a clearly observable domain contrast with consistently shaped energy spectrums. No difference in antiferromagnetic contrast due to lattice strain caused by lattice mismatching was observed. All as-grown samples showed comparable size, distribution and shape of antiferromagnetic domains on both polished and etched substrates. Relaxation of prepared samples in 1000±C for 12 hours in a 1 atm atmosphere of oxygen gave a distinct increase in size for the domains. Area calculation show a increase from typically 0.2 ¹m2 for as-grown films to 2 ¹m2 for relaxed films. Heating experiments estimate a Néel temperature of 625oK for as-grown films and 740oK for relaxed samples. The thermal anneal thus has a significant effect on LaFeO3 thin films as the domains increase in size and the Néel temperature in which the film is no longer antiferromagnetic increases to the Neel temperature of bulk LaFeO3. This preparation approach may be useful for further investigations of the exchange-bias effect.</p>

<p>Video streamed over packet-switched networks such as the Internet are vulnerable to packet loss, which result in a degradation of quality. This degradation can be measured subjectively or by objective measures. The Internet is a best-effort media-unaware environment where all packets receive equal quality of service (QoS), disregarding the fact that some packets are more essential in streaming multimedia applications. Using the differentiated services (DiffServ) model, unequal degrees of QoS are offered, resulting in essential packets being prioritized through the network. The main objective of this thesis is to conduct an informal subjective evaluation experiment, where the test material used consists of high-definition video distorted by various packet loss rates, using both the best effort Internet and DiffServ as underlying channel models. The results from the subjective evaluation experiment are compared to those of the objective video quality estimation to see how well the objective models perform. The video sequences are encoded by using the H.264/AVC video compression standard, and further transmitted in RTP packets. Packet loss is introduced by using a DiffServ simulator, where decoded distorted sequences are assessed. Results show that the NTIA and SSIM were the video quality models with respectively the highest and the lowest performance regarding PLCC, SRCC and RMSE. The NTIA model had statistically significant higher performance than SSIM using PLCC and SRCC with a 95% confidence interval. When comparing packet loss rate versus objective measures, the performance of best effort degrades more rapidly than the performance of DiffServ. However, the results from the subjective evaluations did not show any statistically significant differences between the two channel models using a 90% confidence interval. The DMOS values were categorized into low, medium and high packet loss rates. Studying the high (5%-10%) packet loss rate category, the DiffServ model achieved a higher mean DMOS value compared to the Best Effort model. For low (0%-2.5%) and medium (2.5%-4%) packet loss rates categories the Best Effort model achieved a higher mean DMOS value compared to the DiffServ model.</p>

<p>This master thesis presents the design of a high IIP2 direct-conversion receiver front-end, consisting of a LNA and I- and Q-channel mixers. The front-end is implemented in a 0.18 μm technology with 1.8V supply voltage. Problems that are especially severe for direct-conversion receivers are presented; 1/f-noise, DC offset, and second-order nonlinearity, with particular attention to the latter. Methods to improve the IIP2 are presented and explored in the design of the front-end. The complete front-end has -19.7 dBm IIP3, 4 dB noise figure, and consume 7.4mA of current from a 1.8V supply. Through mixer load tuning an IIP2 of more than +48 dBm is achieved for the front-end.</p>