Executive Summary : | One of the emerging radio architectures for wireless 5G tele-communication applications is frequency reconfigurable radio architecture, which is not only spectrum efficient but also cost effective [1]. Frequency reconfigurable radios have the capacity to dynamically tune their operating frequency band, thus effectively utilizing the white spaces in the frequency spectrum. Such a radio architecture incorporates wideband RF components like power amplifiers, low noise amplifier, mixer and antenna in the transceiver path [2]. The two key narrowband components are local oscillator and band pass filter (BPF). Today, tunable local oscillator technology is well established, thanks to PLL (Phase Locked Loop) architecture [3]. Hence, the bottleneck for successful realization of tunable radios is tunable band pass filters. It is a matter of great concern that at present there is no Indian design and manufacturing entity, who can develop this vital communication component not only for commercial tele-communication application but also for aero-space and strategic applications. Hence, in this proposal, the author proposes to indigenously develop digitally tunable microstrip filter. The author in the recent past has successfully developed tunable coaxial and waveguide filters for satellite applications [4]-[7]. The outcomes from the project (i.e. design methodology, prototypes, potential patents and trained manpower) will be transferred to Indian industry for commercialization towards Atmanirbhar Bharat. A preliminary feasibility study has been carried out, where second order and third order tunable band pass filters are analyzed. Technical document depicts the second order tunable microstrip band pass filter along with simulation response. Technical document depicts the third order tunable microstrip band pass filter. Commercially available ADS simulation tool is used for the preliminary study. The idea comes from the fact that a quarter-wavelength resonator has a short-circuited terminal and an open-ended terminal [8]. By placing a digitally tunable capacitor at the open-ended terminal, one can tune the resonant frequency of the resonator. Hence, by suitably coupling such resonators together and by suitably tapping the input and output, one can realize tunable microstrip band pass filter. The major challenge is that, both, the absolute bandwidth and return loss performance has to be consistent while tuning the frequency response of the filter. The project aims to address this challenge. |