International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 05 Issue: 05 | May-2018 www.irjet.net p-ISSN: 2395-0072 © 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 2640 Design of Switched Filter Bank using Chebyshev Low pass Filter Response for Harmonic Rejection Filter Design Ann Alex 1 , Sanju Sebastian 2 , Niju Abraham 3 1 M.Tech Student, Department of Electronics and Communication Engineering, St. Joseph’s College of Engineering and Technology, Kerala, India, 2 Assistant Professor, Department of Electronics and Communication Engineering, St. Joseph’s College of Engineering and Technology, Kerala, India, 3 Assistant General Manager, Department of Aerospace and Defense, Cyient Limited, Karnataka, India. ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - Harmonic is a serious problem faced by the power amplifier in its working. These are introduced into the power amplifier due to the nonlinearities of the active element such as the transistor in the power amplifier. As a result, the power quality and safe operation become inferior. Therefore the mitigation of harmonics and improvement in the power quality are essential under these circumstances. This paper presents the design of a switched filter bank for using Chebyshev low pass filter response for the design of Harmonic Rejection Filter. Advanced Design System is used for simulation purpose. The obtained results show that each filter bank rejects its harmonic frequencies successfully with a return loss >16 dB. Key Words: Harmonics, Switched Filter Bank, Chebyshev Low pass Filter, Harmonic Rejection Filter, Advanced Design System, Return Loss. 1. INTRODUCTION During 20 th century, evolutions in radios, communications and radars increased the demand for electromagnetic spectrum. Since the demand for Radio Frequency Spectrum has increased and become commercialized for different applications like mobile communications, television and radio communications, a clean radiation spectrum is a must for each radio transmissions. This has to be ensured by the RF front end of each radio transmitters. The RF front end section includes power amplifiers and they introduce harmonics to the signal and these harmonics are a multiple of operating frequencies and causes serious impurities in the spectrum. A demand for higher data rate implies a demand for higher bandwidth for the radio spectrum. This makes the elimination of the harmonics tougher for the RF front-end modules. This motivates the need for an in-house Harmonic Rejection Filter technology in India. The Harmonic Rejection Filter is basically a low pass filter which passes the fundamental frequency and attenuates the higher harmonic frequencies. Passive filters have low cost, simple design and high reliability than active filters. Chebyshev filters have better rate of attenuation beyond passband than Butterworth filters. This paper presents the design of a switched filter bank using Chebyshev low pass filter for the design of Harmonic Rejection Filter. 2. METHODOLOGY Chebyshev filters or equiripple filters have a steeper roll-off and more passband ripple than Butterworth filters. The analytic form of the squared magnitude function is defined by where ε is the ripple factor, Tn(x) is the Chebyshev polynomial of degree n and ωp is the passband edge frequency. Closed form expressions for the Chebyshev polynomial are given by be defined by a recursion formula: where T0(x)=1 and T1(x)=x. The order of the Chebyshev filter is given by the equation: where As is the minimum stopband attenuation in dB, Ap in the maximum passband ripple in dB, ε =(10 0.1Ap −1) 1/2 is the ripple factor, A = (10 0.05As ) 1/2 is the user-defined stopband attenuation parameter, ωs is the stopband edge frequency in rad/sec and ωp is the passband edge frequency in rad/sec. There are two types of LC Ladder networks for Low pass filters as Pi and Tee Section. Pi section prototype starts with a shunt element, whereas Tee section starts with a series element. At the beginning of the circuit g0 = 1 is defined as generator resistance or capacitance. The last element at the end is defined as gN+1 which is the load resistance if gN is a shunt capacitor and load conductance if gN is a series inductor. The type of the prototype used in the design of the filter is Pi section as in Figure 2.1