In this paper theoretical studies have been performed on a multijunction GaInP/GaAs based tandem solar cell. The top GaInP cell and the bottom GaAs cell were investigated separately. At an operating temperature of 300K, the current matching condition is fulfilled when the top cell and bottom cell base doping concentration and thickness are set to 5x1015/cm3, 1µm, and 2x1017/cm3, 0.127µm respectively. For the purpose of the investigation, a wide operating temperature range was chosen from 25ºC to 100ºC. The optimized tandem solar cell structure having a thickness of 1.847 microns is found to have VOC=2.2996V, ISC=0.0136Amp/cm2, FF=87.61% and ɳ=27.4% under AM1.5G one sun illumination. Studies have also revealed that when the cells are analyzed separately the current mismatch is less significant at low temperatures with the difference becoming notable at higher temperatures. Simulations of the solar cell were performed using PC1D.

In this paper, we discuss a Spread Spectrum based radar system for car detection in the road and autonomous guidance of vehicles. An autonomous intelligent vehicle has to perform a number of functionalities. Segmentation of the road, determining the boundaries to drive in and recognizing the vehicles and obstacles around are the main tasks for vision guided vehicle navigation. In this article we propose a set of algorithms which lead to the solution of road and vehicle collision using carrier recovery method from car velocity using DSSS RADAR. In such a spread spectrum system, the transmitted signal is spread over a larger bandwidth, which is much wider than the minimum bandwidth required to transmit the information. Automotive radar systems can take advantage of spread spectrum techniques because of their interference rejection, immunity from noise and multipath distortion, and high resolution ranging properties. In addition, there is no need for high-speed, fast-settling frequency synthesizers. Moreover, spread spectrum techniques can improve the reliability of automotive radars. The data from different sensors on different cars can be combined in order to observe the complete car environment. Thus a spread spectrum radar system will allow sharing the same bandwidth also for data link needed by car-to-car communication systems. The algorithm described here is to recover Doppler frequency using 2P power method from which we are able to detect the vehicle condition in road.