An x-band RFIC active phase shifter

Abstract— An active RFIC X-band phase shifter is implemented using IHP SiGe HBT 0.25 μm SGB25V technology with an improved vector sum method. The chip is formed by a three way Wilkinson power divider, three phase delays for 0-120-240 degrees, three similar RFIC LNAs and a final three way Wilkinson power combiner on the same chip and occupies an area of 4x1.8 mm2. The circuit provides both phase and amplitude control without the need of any additional digital circuitry. Phase shifting is simply based on the weighted vector sum of three vectors which are separated by 120º from each other. All 0-360 degree phase can be scanned simply by this method with the addition of amplitude control. The RFIC LNA circuit is fabricated and measurement results show that LNA has a gain of 10 - 13 dB with in the band of 6-9 GHz and 2-3 dB NF within the same band. The simulation results show that the phase can be scanned from 0-360 degrees with average 7 degree resolution for a 2 dB amplifier gain change. The gain of the overall active phase shifter circuit is 12-13 dB with output gain flatness is 1 dB and the circuit consumes 15.36 mW power. The circuit combines the amplifier with phase shifter and can be used for X-band applications

A telemetry antenna system for unmanned air vehicles

This paper presents a low VSWR high gain telemetry antenna system manufactured for UAVs that provides 360± coverage in the roll plane of the UAV. Proposed telemetry antenna system includes four telemetry antennas, one power divider that has one input and four output terminals which feeds the telemetry antennas with equal magnitude and phase. Proposed high gain telemetry antennas are based on the feeding of the microstrip patch antenna via aperture coupling. Full coverage in the roll plane of the UAV is obtained by using circular array configuration of telemetry antennas. RF power divider is designed by using couple of Wilkinson power dividers with equal line lengths and impedance sections from input terminal to the all four output terminals

Essays On Dynamic Incentive Design

This dissertation consists of three essays that examine incentive problems within various dynamic environments. In Chapter 1, I study the optimal design of a dynamic regulatory system that encourages regulated agents to monitor their activities and voluntarily report their violations. Self-monitoring is a private and costly process, and comprises the core of the incentive problem. There are no monetary transfers. Instead, the regulator (she) uses future regulatory behavior for incentive provision. When the regulator has full commitment power, she can induce costly self-monitoring and revelation of ``bad news\u27\u27 in the initial phase of the optimal policy. During this phase, the agent is promised a higher continuation utility (in the form of future regulatory approval) each time he discloses ``bad news\u27\u27. If the regulator internalizes self-monitoring costs, the agent is either blacklisted or whitelisted in the long run. When she does not internalize these costs, blacklisting is replaced by a temporary probation state, and whitelisting becomes the unique long run outcome. This result suggests that whitelisting, which may appear to be a form of regulatory capture, may instead be a consequence of optimal policy. In Chapter 2, I study the dynamic pricing problem of a durable good monopolist with commitment power, when a new version of the good is expected at some point in the future. The new version of the good is superior to the existing one, bringing a higher flow utility. The buyers are heterogeneous in terms of their valuations and strategically time their purchases. When the arrival is a stationary stochastic process, the corresponding optimal price path is shown to be constant for both versions of the good, hence there is no delay on purchases and time is not used to discriminate over buyers, which is in line with the literature. However, if the arrival of the new version occurs at a commonly known deterministic date, then the price path may decrease over time, resulting in delayed purchases. For both arrival processes, posted prices is a sub-optimal selling mechanism. The optimal one involves bundling of both versions of the good and selling them only together, which can easily be implemented by selling the initial version of the good with a replacement guarantee. Finally, Chapter 3 examines the question under what conditions can automation be less desirable compared to human labor. We study a firm that has to decide between a human-human team and a human-machine team for production. The effort choice of a human employee is not observed by the manager, therefore the incentives need to be properly aligned. We argue that, despite the desirable benefits resulting from the partial substitution of labor with automated machines such as less costly machine input and reduced scope of moral hazard, the teams with only human employees can, under some conditions, be more preferred over the human-machine teams. This stems from the fact that, in all-human teams, the principal, through the selection of incentive scheme, can control the interaction among the agents and get benefit from the mutual monitoring capacity between them. The automation, however, eliminates this interaction and shuts down a channel that can potentially help to mitigate the overall agency problem

Printed dipole array fed with parallel strip line for Ku-band applications

This paper presents the design procedure of a printed dipole antenna and 1D array configurations of the single dipole element in the Ku-Band with its metallic reflector plane parallel to the array plane. The proposed antenna has a natural beam tilt which is useful for some specific applications. Several array configurations in 1D are simulated and tested. The effect of mutual coupling among each array elements is also investigated. Required modifications on the individual array element and the feed structures due to the effect of mutual coupling are examined. The single dipole and array of dipole has measured VSWR values smaller than 2 in the Ku-Band with simulated gains of 5.7 dBi and 12 dBi, respectively. All the simulations are performed with ADS-2006A software and measurements are performed in an anechoic chamber

Optimization of aperture coupled microstrip patch antennas

Aperture coupled microstrip patch antennas (ACMPA) are special class of microstrip antennas with high gain and wide impedance bandwidth. These antennas differ from other microstrip antennas with their feeding structure of the radiating patch element. Input signal couples to the radiating patch through the aperture that exists on the ground plane of the microstrip feedline. These special antennas are multilayer stacked type of antennas with so many design variables that will affect the antenna performance. This paper presents the design and optimization procedure of ACMPA while taking care of all possible design variables and parameters to get the highest possible antenna gain and minimum VSWR

The role of dynamic geometry software in the process of learning: GeoGebra example about triangles

            This paper aims to observe effects of dynamic mathematics software (GeoGebra) on eight grade students’ achievements for the subjects of triangles. Two eighth grade classes from a primary school were selected as experiment and control groups. A two weeks course was planned in accordance with the official course curriculum for the experiment group. The planned and GeoGebra constructed activities which demand effective use of GeoGebra for this grade shared with the students during the learning and teaching process. Simultaneously, the control group continued their formal teaching and learning procedure. A pre test, a post test and a recall test were used to assess the possible effect of the dynamic mathematics software for the groups both before and after the classroom activities. Possible comparisons between the tests and the groups were performed. The results show that dynamic software (GeoGebra) has positive effects on students' learning and achievements. It has also been observed that it improves students’ motivation with positive impact

Efficacy of BNT162b2 and CoronaVac in patients diagnosed with COVID-19

This retrospective observational study is aimed to determine the efficacy of BNT162b2 (Pfizer-BioNTech) and CoronaVac (Sinovac) vaccines against symptomatic or severe disease in COVID-19-diagnosed patients. The secondary aim was to define the differences between vaccinated and un-vaccinated patients in terms of age, comorbidities and course of the disease, and to determine the survival rates. Of the 1463 PCR-positive patients, 55.3 % were vaccinated, and 44.7 % were unvaccinated. While 959 patients had mild-moderate symptoms, 504 patients had severe-critical symptoms and were treated in the intensive care unit. There was a statistically significant difference in the distribution of the type and doses of vaccines between the patient groups (p = 0.021). The rate of receiving 2 doses of Biontech was 18.9 % in the mild-moderate patient group but lower in the severe patient group (12.6 %). The rate of two doses of Sinovac and two doses of Biontech vaccine (four doses of vaccine) was 5 % in the mild-moderate patient group and 1.9 % in the severe patient group. The mortality rates were statistically significantly different (p < 0.001) between the patient groups: 65.3 % in the severe patient group and 1 % in the mild-moderate patient group. The multivariate model showed that the mortality risk of the unvaccinated patients was 1.5 times higher than the vaccinated ones (p = 0.042). In addition to being unvaccinated, advanced age, coronary artery disease (CAD), diabetes mellitus (DM), chronic obstructive pulmonary disease (COPD), chronic kidney disease (CKD), and obesity were found to be associated with higher mortality risk. Besides, the reduction in mortality rate was more evident in individuals vaccinated with at least 2 doses of the BNT162b2 (Pfizer-BioNTech) vaccine than in CoronaVac group

Experimental investigation of time-dependent local scour downstream of a stepped channel

In this study, temporal variation of local scour occurring at the downstream part of the stepped channel were investigated experimentally. The experimental tests were carried out in a stepped flume with a height of 2.4 m. The width of the rectangular flume was 0.10 m and the length of the stilling basin was 2.12 m. Bed material was placed in a sediment box with a height of 24 cm and length of 2.48 m, without any compaction. Experiments were carried out by using bed material of 4 different grain size distributions, 2 different sill heights and 6 different flow rates. Two empirical equations which include Shields parameter (θ) and densimetric Froude particle number (Fd) were proposed by using the experimental findings to predict the temporal variation of the scour depth. The R2 (coefficient of determination) values were computed for both proposed equations as 0.866 and 0.865. The scatter index (SI) values were also determined and computed as 8.73% and 8.25%. The fit of the equations was also determined by means of Fisher’s test.Keywords: stepped channel, local scour, temporal variatio

Effects of Collars on Scour Reduction at Bridge Abutments

Bridge failures are generally resulted from scour of the bed material around bridge piers and abutments during floods. In this study, scour phenomenon around bridge abutments and collars, located at abutments as scour countermeasures, were experimentally investigated. Based on the results of 97 experiments conducted, the effect of various sizes of collars which were located around the abutments at different elevations, on the scour reduction at bridge abutments was determined. The results were compared with previous studies, and the effect of the sediment grain size on the performance of abutment collars was emphasized. It was noticed that when the collar width was increased and it was placed at or below the bed level, the reduction in the maximum local scour depth increases considerably. It was also seen that the change of the sediment size did not affect the optimum location of the collar at the abutment, which yields the maximum scour reduction around the abutment. © 2010 American Society of Civil Engineers