Application of CSDG Mosfet based active high pass filter in communication systems.

Abstract

This research work looks at the design of three active high pass filters. These filters have been designed for (i) robotic system, (ii) sensing device and (iii) satellite communication system. In this research work a high pass filter has been designed with a Cylindrical Surrounding Double Gate (CSDG) MOSFET. A CSDG MOSFET is a continuation of DG MOSFET technology. It is formed by rotation of a DG MOSFET with respect to its reference point to form a hollow cylinder. It consists of 2 gates, a drain and a source. Electronic robotic systems have a section of transmitter and receiver. For the receiver, to provide the required selectivity of frequencies, a filter is used. There is a wide variety of these filters that can be used within the Radio Frequency (RF) range. Radio frequencies range from 3 kHz to 300 GHz. This particular filter is designed and simulated at a cutoff frequency of 100 GHz (0.1 THz). It makes use both an operational amplifier and a transistor. This circuit was compared to a circuit that made use of 2 operational amplifiers and the results are discussed. In addition a CSDG MOSFET which makes use of a Silicon Dioxide dielectric is connected to the output of the transistor circuit to see what effect it has on the circuit. Using this model of filter a fine signal (command) can be given to robotic system. The second filter is designed for remote sensing devices. These devices continuously send/receive signals and these signals or radio waves are transmitted/received via a transmission line to/from a receiver/transmitter which has a filter that selectively sorts out the signals and only passes a desired range of signals. The CSDG MOSFET being a capacitive model allows for better filtering of low frequencies and passes through a frequency range of 200 GHz (0.2 THz) efficiently. By placing the capacitors in parallel, the design requires smaller capacitance values to be used. In addition the desired range of frequencies can be achieved from the inversely proportional relationship between frequency and capacitance. Finally a filter has been designed to use in satellite communication systems. These systems consist of various subsystems to allow it to function efficiently. These subsystems require a number of electronic devices. In this research work, a CSDG MOSFET is added to the output of the transistor circuit and operates within the EHF band (0.3 THz). The CSDG MOSFET makes use of Hafnium Silicate (HfSiO4) as a dielectric material due to its wide band-gap and lower dielectric constant makes it ideal for this design. The gain and other parameters of the three designed filters are analyzed. In conclusion, it has been demonstrated that the third order active high pass filters performs better with the CSDG MOSFET.