Highly selective bandpass filter using substrate integrated waveguide technology for FMCW radar application

Abstract

A bandpass filter using substrate integrated waveguide technology is proposed in this paper for ISM band frequency (5.7–5.9 GHz) application. Metallic inductive posts are used for the realization of the filter. The proposed structure provides pass band from the frequency range of 5.72 GHz to 5.84 GHz with the insertion loss of 0.7 dB and return loss more than 25 dB. Frequency tuning is carried out from the frequency range of 5.65 GHz to 6.06 GHz with the variation of pass band bandwidth from 88 MHz to 222 MHz. All the simulations are carried out by high frequency structure simulator based on FEM method software. Proposed bandpass filter is fabricated and measured result indicates better performance. It will be utilized in the system developed at CSRTC for the suppression of higher order harmonics in frequency modulated continuous wave radar at the frequency from 5.725 GHz to 5.875 GHz.

Half‐mode substrate‐integrated waveguide based band‐pass filter for C band application

“…A basic structure of SIW is as shown in Figure . It is formed by inserting metallic vias in a dielectric substrate which connects the top and bottom metallic plane . It acts as a high‐pass filter, and cut off frequency of the structure is decided by the width of the waveguide according to Equations …”

“… where a equ is the lateral center to center distance between two metallic rows, d is the diameter of metallic post, p is the spacing between two metallic posts, h is the height of the substrate. Cut‐off frequency of SIW can be calculated from Equation where c is the velocity of electromagnetic wave in free space (3 × 108 m s −1 ), ε r is the relative permittivity of substrate material.…”

“…Microwave and millimeter wave system development requires number of components like oscillator, amplifier, filters, power divider, antenna, and so on. It is pre‐requisites that these components are superior in performance, compact in size with lower development cost . For the development of passive components, conventional waveguide technology or Microstrip line technology are used.…”

“…Conventional waveguide provides better performance with high‐power handling capacity; however, size of the structure, manufacture cost, and integration of it with planar structure are the major limitations . On the other side, development of components based on Microstrip line are small in size, low manufacturing cost, and easy integration but with low power handling capacity and higher losses …”

“…Nowadays planar metallic waveguide structure called as a substrate‐integrated waveguide (SIW) is vastly used in replacement of conventional waveguide technology and Microstrip line. It takes the advantage of both Microstrip line and CWT like better power handling capacity, lower losses, lower weight, high quality factor, low manufacturing cost, and compact in size . Number of components has been reported in different literature based on SIW technology like filters, antennas, and power divider …”