Modified parallel coupled line filter for WiFi application

Abstract

Wireless Local Area Network (WLAN) is a network that allows different devices to communicate and connect without wire. The common application for WLAN in daily life is Wireless Fidelity (WiFi). Most devices, such as mobile phones, laptops, smartwatches, and some Internet of Things (IoT) devices support a WiFi connection. Recently, the technology WiFi 6 has been introduced which has a standard of 802.11ax. The operating frequency of WiFi 6 is 5 GHz with a bandwidth of 160 MHz. In the RF front end, a filter is very important in to filter out the unwanted signal and influence the performance of applications. A parallel coupled line (PCL) bandpass filter is one of the filters that can be used in WiFi transceiver, which has low cost and flexible layout and easy fabrication. Conventional PCL bandpass filter has large size at a higher order and slow attenuation level in stop band at a lower order. Hence, the main objective of this project is to design a PCL bandpass filter with a small size and have good attenuation performance at the stop band. This can be achieved by adding extra stub of coupled line and a quarter wavelength line for low order PCL filter to form transmission zero at upper and lower stopband. The proposed PCL bandpass filter support for WiFi 6 at 5GHz. The conventional PCL and proposed PCL bandpass filter are designed by manual calculation. Simulation and optimization are done by using CST and ADS softwares. The proposed filter is fabricated and comparison of conventional and proposed PCL bandpass filter based on size and performance are discussed. The proposed PCL bandpass filter has better performance in stopband rejection level and the area taken in planar is smaller.