Browsing by Subject "filter"
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Item Automatic tuning of continuous-time filters(Texas A&M University, 2004-11-15) Sumesaglam, TanerIntegrated high-Q continuous-time filters require adaptive tuning circuits that will correct the filter parameters such as center frequency and quality factor (Q). Three different automatic tuning techniques are introduced. In all of the proposed methods, frequencyand quality factor tuning loops are controlled digitally, providing stable tuning by activating only one loop at a given time. In addition, a direct relationship between passband gain and quality factor is not required, so the techniques can be applied to active LC filters as well as Gm-C filters. The digital-tuning method based on phase comparison was veri?ed with 1% tuning accuracy at 5.5 MHz for Q of 20. It uses phase information for both Q and center-frequency tuning. The ?lter output phase is tuned to the known references, which are generated by a frequency synthesizer. The core tuning circuit consists of D ?ip-?ops (DFF) and simple logic gates. DFFs are utilized to perform binary phase comparisons. The second method, high-order digital tuning based on phase comparison, is an extension of the previous technique to high-order analog filters without depending on the master-slave approach. Direct tuning of the overall filter response is achieved without separating individual biquad sections, eliminating switches and their parasitics. The tuning system was veri?ed with a prototype 6th order bandpass ?lter at 19 MHz with 0.6 MHz bandwidth, which was fabricated in a conventional 0.5 [mu]m CMOS technology. Analysis of different practical limitations is also provided. Finally, the digital-tuning method based on magnitude comparison is proposed for second-order filters for higher frequency operations. It incorporates a frequency synthesizer to generate reference signals, an envelope detector and a switched comparator to compare output magnitudes at three reference frequencies. The theoretical analysis of the technique and the simulation results are provided.Item Digitally Assisted Multi-Channel Receivers(2011-10-21) Pentakota, Krishna Anand Santosh SpikanthThis work presents a data estimation scheme for wide band multi-channel charge sampling receivers with sinc filter banks together with a complete system calibration and synchronization algorithm for the receiver. A unified model has been defined for the receiver containing all first order mismatches, offsets and imperfections and a technique based on least mean squares algorithm is employed to track these errors. The performance of this technique under noisy channel conditions has been verified. The sinc filter bank is compared with the conventional analog filter banks and it is shown that the sinc filter banks have very low computational complexity in data estimation Nextly, analytical tools for the design of clock-jitter tolerant multi-channel filterbank receivers have been developed. Clock-jitter is one of the most fundamental obstacles for the future generation of wideband receivers. Additionally all the trade-offs and specifications of a design example for a multi-channel receiver that can process a 5 GHz baseband signal with 40 dB of signal-to-noise-ratio (SNR) using sampling clocks that can tolerate up to 5 ps of clock-jitter standard deviation are presented. A novel bandwidth optimization technique has been presented. As a part of it the bandwidth of the filters present in each path is optimized thereby improving the performance of the receiver further in the presence of sampling clock jitter. The amount of bandwidth reduction possible depends on the order of the filter and the noise amplification provided by the reconstruction matrix. It has been shown that 3rd order filters of bandwidth 1 GHz can be replaced with 1st order filters of bandwidth 100 MHz without any depreciation in the output resolution, implying huge power savings.Item The effect of nutrient limitations on the production of extracellular polymeric substances by drinking-water bacteria(2013-05) Evans, Ashley Nichole; Kirisits, Mary JoBiological filtration (biofiltration) of drinking-water is gaining popularity due the potential for biodegradation of an array of contaminants not removed by traditional drinking-water processes. However, previous research has suggested that biomass growth on biofilter media may lead to increased headloss, and thus, greater energy and water requirements for backwashing. Research has suggested that the main cause of headloss might be due to extracellular polymeric substances (EPS) rather than the bacterial cells themselves. As EPS production has been shown to increase under nitrogen- and phosphorus-limited or -depleted conditions, the goal of this research was to add to the body of knowledge regarding biofiltration by studying the relationship between EPS production and nutrient limitations in drinking-water. Batch experiments with a synthetic groundwater were run with a mixed community of drinking-water bacteria under nutrient-balanced (a molar carbon to nitrogen to phosphorus ratio [C:N:P] of 100:10:1), nutrient-limited (e.g., C:N:P of 100:10:0.1), and nutrient-depleted conditions (C:N:P of 100:0:1 or 100:10:0). After 5 days, growth was measured as the optical density at 600 nanometers (OD600), and the concentrations of free and bound carbohydrates and proteins, the main components of EPS, were measured. In batch experiments with 2.0 and 0.2 g/L as carbon (mixture of acetic acid, mannitol and sucrose) increases in EPS production per OD600 and decreases in growth were noted under nutrient-depleted conditions. When the same experiments were conducted with a pure culture of Bacillus cereus, bound polysaccharides normalized to OD600 increased under nitrogen- and phosphorus-depleted conditions. Since previous research suggested that Bradyrhizobium would be an important player in EPS production in drinking-water biofilters, similar batch experiments were conducted with Bradyrhizobium. However, due to experimental challenges with Bradyrhizobium japonicum USDA 110, differences in EPS production under nutrient limitations could not be reliably assessed. Additional work is required with Bradyrhizobium. Recommendations for future work include the replication of these batch conditions in steady-state chemostats containing biofilm attachment media and in bench-scale columns. Additionally, future work should include experiments at carbon concentrations as low as 2 mg/L to match typical carbon concentrations in drinking-water biofilters.Item High frequency continuous-time circuits and built-in-self-test using CMOS RMS detector(Texas A&M University, 2007-04-25) Venkatasubramanian, RadhikaThe expanding wireless market has resulted in complex integrated transceivers that involve RF, analog and mixed-signal circuits, resulting in expensive and complicated testing. The most important challenges that test engineering faces today are (1) providing a fast and accurate fault-diagnosis and performance characterization so as to accelerate the time-to-market and (2) providing an inexpensive test strategy that can be integrated with the design so as to aid the high-volume manufacturing process. The first part of the research focuses on the design of an RMS detector for built-in-self-test (BIST) of an RF integrated transceiver that can directly provide information at various test points in the design. A cascode low noise amplifier (LNA) has been chosen as the device under test (DUT). A compact (< 0.031 mm2) RF RMS detector with negligible input capacitance (< 13 fF) has been implemented in 0.35 ????m CMOS technology along with the DUT. Experimental results are currently being assimilated and compared with the simulation results. Frequency limitations were encountered during the testing process due to unexpected increase in the value of the N-well resistors. All other problems faced during the testing, as well as the results obtained so far, are presented in this thesis. In the second part of the research, the use of the RMS detector for BIST has been extended to a continuous-time high-frequency boost-filter. The proposed HF RMS detector has been implemented along with a 24 dB 350 MHz boost filter as the DUT on 0.35 ????m CMOS technology. The HF RMS detector occupies 0.07 mm2 and has an input capacitance of 7 fF. The HF RMS detector has a dynamic range greater than 24 dB starting from -38 dBm of input power. The bandwidth and boost of the filter have been accurately estimated in simulation using the HF RMS detector. The sensitivity of an intermediate band pass node of the filter has also been monitored to predict the filter's sensitivity to Q errors. The final part of the research describes the design of a single-ended to differential converter for use in a broadband transceiver operating from 50-850 MHz. This circuit is used as the second stage in the transceiver after the LNA. The design has been simulated on a 0.35 um CMOS process and has a power consumption of 13.5 mW and less than 8 dB of noise figure over the entire band. It is capable of driving a 500fF load with less than 1dB of gain ripple over the entire band (50-850 MHz).Item Low Power Filtering Techniques for Wideband and Wireless Applications(2010-10-12) Gambhir, ManishaThis dissertation presents design and implementation of continuous time analog filters for two specific applications: wideband analog systems such as disk drive channel and low-power wireless applications. Specific focus has been techniques that reduce the power requirements of the overall system either through improvement in architecture or efficiency of the analog building blocks. The first problem that this dissertation addresses is the implementation of wideband filters with high equalization gain. An efficient architecture that realizes equalization zeros by combining available transfer functions associated with a biquadratic cell is proposed. A 330MHz, 5th order Gm-C lowpass Butterworth filter with 24dB boost is designed using the proposed architecture. The prototype fabricated in standard 0.35um CMOS process shows -41dB of IM3 for 250mV peak to peak swing with 8.6mW/pole of power dissipation. Also, an LC prototype implemented using similar architecture is discussed in brief. It is shown that, for practical range of frequency and SNR, LC based design is more power efficient than a Gm-C one, though at the cost of much larger area. Secondly, a complementary current mirror based building block is proposed, which pushes the limits imposed by conventional transconductors on the powerefficiency of Gm-C filters. Signal processing through complementary devices provides good linearity and Gm/Id efficiency and is shown to improve power efficiency by nearly 7 times. A current-mode 4th order Butterworth filter is designed, in 0.13um UMC technology, using the proposed building. It provides 54.2dB IM3 and 55dB SNR in 1.3GHz bandwidth while consuming as low as 24mW of power. All CMOS filter realization occupies a relatively small area and is well suited for integration in deep submicron technologies. Thirdly, a 20MHz, 68dB dynamic range active RC filter is presented. This filter is designed for a ten bit continuous time sigma delta ADC architecture developed specifically for fine-line CMOS technologies. Inverter based amplification and a common mode feedback for such amplifiers are discussed. The filter consumes 5mW of power and occupies an area of 0.07 mm2.Item Microwave Metamaterial Applications using Complementary Split Ring Resonators and High Gain Rectifying Reflectarray for Wireless Power Transmission(2011-10-21) Ahn, Chi HyungIn the past decade, artificial materials have attracted considerable attention as potential solutions to meet the demands of modern microwave technology for simultaneously achieving component minimization and higher performance in mobile communications, medical, and optoelectronics applications. To realize this potential, more research on metamaterials is needed. In this dissertation, new bandpass filter and diplexer as microwave metamaterial applications have been developed. Unlike the conventional complementary split ring (CSRR) filters, coupled lines are used to provide larger coupling capacitance, resulting in better bandpass characteristics with two CSRRs only. The modified bandpass filters are used to deisgn a compact diplexer. A new CSRR antenna fed by coplanar waveguide has also been developed as another metamaterial application. The rectangular shape CSRRs antenna achieves dual band frequency properties without any special matching network. The higher resonant frequency is dominantly determined by the outer slot ring, while the lower resonant frequency is generated by the coupling between two CSRRs. The proposed antenna achieves about 35 percent size reduction, compared with the conventional slot antennas at the low resonant frequencies. As a future alternative energy solution, space solar power transmission and wireless power transmission have received much attention. The design of efficient rectifying antennas called rectennas is very critical in the wireless power transmission system. The conventional method to obtain long distance range and high output power is to use a large antenna array in rectenna design. However, the use of array antennas has several problems: the relatively high loss of the array feed networks, difficultiy in feeding network design, and antenna radiator coupling that degrades rectenna array performance. In this dissertation, to overcome the above problems, a reflectarray is used to build a rectenna system. The spatial feeding method of the reflectarray eliminates the energy loss and design complexity of a feeding network. A high gain rectifying antenna has been developed and located at the focal point of the reflectarray to receive the reflected RF singals and genterate DC power. The technologies are very useful for high power wireless power transmission applications.Item Programmable two-port polarization independent electro-optically tunable wavelength filter in lithium niobate(2009-05-15) Ping, YangProgrammable two-port polarization independent electro-optically wavelength tunable filters based on asymmetric Mach-Zehnder structure in LiNbO3 substrate have been developed for 1.55 ?m application. The operation principle is based on Mach-Zehnder interference and TE?TM polarization conversion. Fabrication parameters for channel waveguides, polarization converters and bandpass filters have been optimized. Straight channel waveguides 7 ?m in width were produced by diffusing 1116 ? thick Ti into LiNbO3 substrate at 1035?C for 10 hours. Single mode guiding has been realized for both TE and TM polarization. Insertion loss of 2.9 dB for TE polarization input and 3.3 dB for TM polarization input were achieved on a 46 mm long sample. Single sideband programmable polarization mode converters were produced with 16 electrode sets, each containing 64 grating periods. Programmability was achieved by applying spatially periodic weighted independent voltages to interdigital electrode sets, and controlled electronically via a personal computer through a digital-to-analog converter array chip. Maximum conversion efficiency of more than 99% was realized for both TM?TE and TE?TM, and was observed at 1530.48 nm. Two-port polarization independent electro-optically tunable wavelength filters were produced based on the results obtained above. The 3 dB bandwidth is 1.1 nm and the nearest side lobes to the main transmission are down by about 9 dB for uniform coupling. Side lobes are reduced to about 20 dB below peak transmission after apodization, and the 3 dB bandwidths increased to ~ 1.3 nm as a result. Seven channels (channel -4, -2, -1, 0, +1, +2 and +4) were selectable by programming the voltages on each electrode set. Channel spacing is 1.1~1.2 nm. The tuning ranges from 1524.04 to 1533.56 nm. Fiber-to-fiber insertion loss of the filter at center frequency is 4.3 dB for TE input and 4.2 dB for TM input. The polarization dependent loss is < 0.5 dB for all selectable channels. The temporal response to a 21 V step change in applied voltages was measured to be 586 ns for the 10%-90% rise time and 2.308 ?s for the 90%-10% fall time. This research work provides a convenient scheme for making programmable two-port tunable bandpass filters and ROADMs.Item Two-port polarization independent electro-optically tunable wavelength filter in lithium niobate(Texas A&M University, 2004-09-30) Ping, YangTwo-port polarization independent electro-optically wavelength tunable filters based on asymmetric Mach-Zehnder structure in LiNbO3 substrate have been developed for 1.55?m application. The operation principle is based on Mach-Zehnder interference and TE?TM mode conversion. Fabrication parameters for channel waveguides, interferometers and mode converters have been optimized. 7?m wide single mode straight channel waveguides were produced by diffusing 1050-1100A thick Ti into LiNbO3 substrate. Insertion loss of 3.6dB was achieved for both TE and TM polarization. Mach-Zehnder interferometer performance was optimized by testing the Y-branch on samples cut in half length compared to complete device. Best results were obtained from samples that were produced by diffusion at 1025 degC for 11 hours of 1050A thick Ti film, and by diffusion at 1025 degC for 12 hours of 1090A thick Ti film. Metal electrodes were added to one arm of asymmetric Mach-Zehnder interferometers to evaluate electro-optic modulation. Modulation depth as high as 99.6% for TE mode and 98.9% for TM mode were obtained. TE?TM mode conversion was demonstrated on straight channel waveguides with conversion efficiency greater than 96% utilizing 500 strain inducing SiO2 grating pads with 21?m spatial period. Two-port polarization independent electro-optically tunable wavelength filters were produced based on the optimized parameters described above. The -3dB bandwidth of the filter is 2.4nm. The nearest side lobe to the main peak is more than 13dB below the central lobe for both TE polarization and TM polarization. A thermal tuning rate of -0.765nm/degC is obtained. An electrical tuning range of 12.8nm and a tuning rate of 0.08nm/V were achieved.Item Wideband phased array antennas and compact, harmonic-suppressed microstrip filters(2009-05-15) Tu, Wen-HuaModern satellite, wireless communications, and radar systems often demand wideband performance for multi-channel and multi-function operations. Among these applications, phased array antennas play an important role. This dissertation covers two wideband phased array antennas, one produces linear polarization and one produces circular polarization. The main difference between these two phased array antennas is the antenna array. For the linearly polarized array, a wideband microstrip line to slotline transition is used to feed a Vivaldi antenna. For the circularly polarized array, a wideband microstrip line to parallel stripline transition is used to feed a spiral antenna. From 3 to 12 GHz, the linearly polarized beam is steered over ? 15?. Since the electromagnetic spectrum is limited and has to be shared, interference is getting serious as more and more wireless applications emerge. Filters are key components to prevent harmonic interference. The harmonic signals can be suppressed by cascading additional lowpass filters or bandstop filters. A bandstop filter combining shunt open stubs and a spurline is proposed for a compact size and a deeper rejection. Two lowpass filters with interdigital capacitors and slotted ground structures are also studied. Harmonic suppression can also be achieved with the modification of bandpass filters. Three conventional bandpass filters with spurious passbands are investigated. The first one is a dual-mode patch bandpass filter. The second passband of the proposed filter is at 2.88fo, where fo is the fundametal frequency. The second filter is an open-loop bandpass filter. Two open stubs are added to achieve high suppression in the second harmonic signal. The suppression of 35 dB at the second harmonic is obtained. For the third filter using half-wavelength open stubs, a T-shaped line is used to replace the quarter-wavelength connecting line. The T-shaped line has the same response with the connecting line in the passband. Furthermore, the T-shaped line works as a bandstop filter at the second harmonic. Finally, a new compact slow-wave resonator and bandpass filters are presented. A simple transmission-line model is used to predict the resonant frequency. Compared with the conventional uniform half-wavelength resonator, the slow-wave resonator shows a 25% size reduction.