Tapas Chakravarty

A Novel Digital Beamformer with Low Angle Resolution for Vehicle Tracking Radar

In this paper we propose a digital beamformer utilizing the radar integrator method of detection. In the receive mode the digitized radar returns weights are allocate on the such a way that the first pulse reflect a SUM pattern and the subsequent three pulses reflect DIFFERENCE pattern. The pulses on DIFFERENCE pattern are added to each other and the net signal subtracted from signal received in SUM pattern. This results in very narrow beam which shows narrow spatial resolution. The schematic is presented and the results are shown.

Analytical Model for Optimum Signal Integrity in PCB Interconnects Using Ground Tracks

In this paper, we present analytical models for line impedance and the coupling coefficient in the presence of additional ground tracks. We use a variational analysis combined with the transverse transmission-line technique to model interconnect lines guarded by ground tracks. Using the proposed model, it would be possible for designers to reduce crosstalk in coupled lines and obtain desired line impedance, thereby ensuring optimum signal integrity. The results obtained are verified by full-wave simulations and measurements performed on a vector network analyzer. The proposed model may find applications in the design and analysis of high-speed interconnects.

Numerical Computation of Resonant Frequency of Gap Coupled Circular Microstrip Antennas

In this paper the numerical computation of resonant frequency of gap coupled circular microstrip antennas using the concept of cavity model has been presented. The resonant frequency of the gap-coupled circular patches is computed and the mode number is also evaluated. The computed results are compared with published results. The previously published results are based on experimentation and do not present a clear mathematical model for the same structure. An extensive comparison with Method-of-moments based software (IE3D) is also done. The accuracy of prediction is reasonably good.

On the architecture of vehicle tracking system using wireless sensor devices

Integration of different technologies potentially provides support to wide variety of applications and systems with vastly varying requirements and characteristics. Vehicle tracking system is one of such applications possible by embedding wireless sensor devices on the vehicles. The most of the state-of the-art technology uses GPS (Global Positioning System) for tracking vehicles which is very expensive. The focus of the proposed vehicle tracking system is to track the desired vehicle with low-cost, effective implementation as in contrast to the existing high-cost tracking systems. In this paper, we present architecture for vehicle tracking system using wireless sensor technology. We have defined the packet structure for communication between the nodes. Certain issues that arise during implementation are discussed. To investigate our proposed design towards implementation, we have performed simulations for different scenarios under certain realistic conditions using Qualnet network simulator. The results from the analysis and evaluation through simulations provide general design guidelines to implement the proposed solution.

BlueEye: a system for proximity detection using bluetooth on mobile phones

Interesting applications of crowdsensing include measurement of crowdedness at public places and evaluating the extent of social interactions between people, at large gatherings. These require enabling the accurate estimation of proximity between two or more people. Since mobile phones have emerged as the most ubiquitous sensing and computing platform, carried by almost all people close to their body, it is logical to use the same for proximity detection. Further, in order to motivate people to use such application, it is necessary to estimate distances accurately, using only short blocks of sampled signal strengths. In this paper the authors present a mobile based proximity detection system, codenamed BlueEye which is based on Bluetooth. To achieve better distance estimates, BlueEye proposes a new form of path loss model which takes into account the relative orientation of mobile phones. The results show enhanced distance estimates when the separation between devices is less than 8 feet.

Characteristic Impedance of a Microstrip-Like Interconnect Line in Presence of Ground Plane Aperture

We propose new empirical expressions for the characteristic impedance of a microstrip-like interconnect line in presence of ground plane aperture. The existing characteristic impedance expressions are modified so as to include the effect of the ground plane aperture. The variation in the characteristic impedance vis-a-vis the aperture size is established. The proposed expressions are general and valid for a range of dielectric materials concerning MICs, RFICs, and PCBs. The results are validated by measurements performed on a vector network analyzer.

Gap - Coupled Microstrip Antennas

In this paper a survey of the gap-coupled microstrip antennas is presented. The need and types of gap-coupled microstrip antennas with recent research overview is discussed. By using the concept of gap-coupling the bandwidth of microstrip antenna can be increased. In this one patch is fed and the parasitic patch is excited by the gap-coupling. The concept of increasing the bandwidth by gap-coupling is also discussed.

Estimating true speed of moving vehicle using smartphone-based GPS measurement

The Global Positioning System (GPS) receivers are now an integral part of smartphones. However, phone based GPS measurements display much less accuracy as compared to professional grade receivers. On the other hand, the deep penetration of smartphones in consumer market offers opportunity for customizing new solutions. One such possible application is targeted towards identifying risky driving profile for the purpose of customizing auto-insurance premium. For this to be successful, one needs to estimate the true vehicle speed. In this paper, we have presented a method to estimate the true speed of a moving vehicle derived solely from GPS measurements. In this case the accelerometer sensors are not used in conjunction with GPS measurement. The results are compared with OBD2 speed measurement. The proposed method computes a better estimate of vehicle speed, where correctness is measured relative to OBD2 measurement.

EXTENDED CAVITY MODEL ANALYSIS OF STACKED CIRCULAR DISC

Stacked microstrip antennas deserve special attention due to their advantageous properties like dual frequency operation and wide bandwidth. In the present communication a theoretical model for single stacked microstrip disc antenna is proposed using extended cavity model. The method of analysis by this model is easier and intuitive than the full wave analysis. Single stacked microstrip disc antenna with co-axial feed locations at different radial positions is analyzed with this model taking different ratios of patch sizes. Antenna properties like return loss, input impedance, gain and radiation efficiency are calculated with the proposed model different cases and compared with the simulated and experimental results. The results are in fairly good agreement.

Reduction of Signal Overshoots in High-Speed Interconnects Using Adjacent Ground Tracks

In this paper, we present a novel computational model that uses ground tracks adjacent to the interconnect line for alleviation of signal overshoots. It is found that the adjacent ground tracks increase the capacitance of the interconnect line and therefore the damping factor, which reduces the signal overshoots and undershoots to acceptable levels. The proposed model is based on the unified approach (variational analysis combined with transverse transmission line technique) and uses existing ground tracks that are commonly used for crosstalk mitigation between coupled interconnects, thus avoiding any physical changes in the interconnect geometry. Results are verified using finite-difference time-domain simulations and measurements performed on a vector network analyzer. The novelty of our model lies in the easy and efficient computation of line parameters and damping factor. The proposed model can be used for mitigation of signal overshoots in high-speed interconnects, whether on-chip, or at packaging, board, or system levels, where overshoots are a common design headache.