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Abstract Microstrip line based two switchable power dividers are presented in this paper and these models are capable of power division control at four output ports. Here, power switching is implemented with terminating some open-ended stub-lines using varactor diodes and corresponding mathematical equations are derived. Proper DC voltages are applied for biasing the activator diodes and consequently to have appropriate stub-line terminations. For designing these power dividers, CST Microwave Studio is used here as the EM tool. The characteristics such as return loss, insertion loss and isolation have been explored from the simulation results followed by it's fabrication and measurement. Quite good agreement is achieved between the simulation and the experimental results. Much better performance characteristics make this proposed power divider a good candidate for various microwave systems where switchable power dividers are required. [ABSTRACT FROM AUTHOR]

Aircraft/traffic alert and collision avoidance system (ACAS/TCAS) is an airborne system which is designed to provide the service as a last defense equipment for avoiding mid-air collisions between the aircraft. In the existing system, four monopole stub-elements are used as ACAS directional antenna and one blade type element is used as ACAS omnidirectional antenna. The existing ACAS antenna has some drawbacks such as low gain, large beamwidth, frequency and beam tuning/scanning issues etc. Antenna issues like unwanted signals reception may create difficulties to identify the possible threats. In this paper, the focus is on the design and development of a unit element microstrip antenna which can be used for ACAS application and to overcome the possible limitations associated with the existing techniques. Two proposed antenna models are presented here, which are single feed and dual feed microstrip dual patch slotted antenna. These are designed and simulated in CST Microwave Studio tool. The performance and other antenna characteristics have been explored from the simulation results followed by the antenna fabrication and measurement. A good reflection coefficient, Voltage Standing Wave Ratio (VSWR), narrow beamwidth, perfect directional radiation pattern, high gain and directivity make this proposed antenna a good candidate for this application. [ABSTRACT FROM AUTHOR]