E-ISSN: 2349-7610 INTERNATIONAL JOURNAL FOR RESEARCH IN EMERGING SCIENCE AND TECHNOLOGY, VOLUME-1, ISSUE-3, AUGUST-2014 1 Analysis of Microstrip Finger on bandwidth of Interdigital band Pass Filter using Artificial Neural Network 1 Robert Mark, 2 Vandana V. Thakare 1 Dept of Electronics, Madhav Institute of Technology and Science, Gwalior, India 1 markrobert7@gmail.com 2 Dept of Electronics, Madhav Institute of Technology and Science, Gwalior, India 2 vandanavt_19@rediffmail.com ABSTRACT In this paper, a novel method of bandwidth estimation using variation of finger length on interdigital band pass filter has been presented using artificial neural networks for desired frequency range between 1.5--3.5GHz. Interdigital filter is multifinger periodic structure which offers compact filter design space. An ANN model has been developed and tested for estimating the cut off frequency of band pass filter and performance is evaluated in terms of mean square error and concluded that RBF network is more accurate than MLPFFBP. The proposed method of design provides the exact bandwidth for particular finger length of filter without using painstaking calculation. Keyword - Artificial neural networks (ANN), Multi layer Perceptron feed Forward back propagation (MLPFFBP), Interdigital capacitor (IDC), Mean square error (MSE), Radial Basis Function (RBF), Artificial neural network (ANN), Levenberg Marquardt (LM). 1. INTRODUCTION In modern communication systems, high performance and small size band pass filters are essentially required to enhance the system performance and to reduce cost of fabrication. Existing Parallel coupled microstrip filters have been widely used in the RF front end of microwave and wireless communication systems for decades. But their large size was problematic with the RF system where size is important consideration [1-2]. To overcome existing drawback, Interdigital capacitor (IDC) geometry is used in which gaps meanders back and forth in a rectangular area forming two sets of fingers that are interdigital. IDC is a multifinger periodic structure which offer very high Q value in compact design space with microstrip finger coupled between the input and output ports across the gaps, hence increase performance of filter. [3] In present work, an attempt has been made to utilize the potential of neural network to calculate the cut off frequency of filter using data from design parameter. ANN model has been established by learning from microwave data which was acquired by EM simulation of filter design in CST (computer simulation technology) Microwave environment and results are used as standard to train the network through a process called training. An ANN model based on Radial basis function and feed forward back propagation algorithms are used to train the network and determine Fu (upper cut off) and Fl (lower cut off) and hence bandwidth (Fu - Fl) of filter for desired frequency range of 1.5-3.5 GHz. 2. PROPOSED FILTER DESIGN AND DATA GENERATION Interdigital capacitor (IDC) is an element for producing high pass characteristic using microstrip finger lines used for filter design. Number of Fingers (N) provide coupling between the input and output ports across the gaps. Typically, the gaps between finger and end of the fingers are equal to reduce parasitic capacitance. [3] The length (L) and width (W) of the finger determined total capacitance and capacitance per unit length along the width of