Dual-band UWB filter using multilayer liquid crystal polymer technology

Abstract

A novel dual-band ultra-wideband (UWB) bandpass filter with compact size is reported. A multilayer structure is adopted to implement the proposed filter. Broadside-coupled patches are designed on the top and second layers to realise an ultra-wide passband character, and quarter-wavelength resonators are integrated underneath broadside-coupled patches to realise the desired stopband. The proposed filter is fabricated using multilayer liquid crystal polymer lamination technology. Experiment results are presented to verify predicted results, which show the proposed filter has good performance including compact size, sharp stopband rejection and good passband performance.Introduction: Following the exploring of ultra-wideband (UWB) technology in high data-rate wireless communication systems, the UWB bandpass filter (BPF) has attracted much research interest in recent years. However, since the FCC-defined Indoor Limit from 3.1 to 10.6 GHz covers some existing wireless communication systems such as 5.0-6.0 GHz wireless local access network, it is necessary to introduce high rejection in these frequency bands to avoid interference from existing wireless communication systems in the UWB BPF design. To this end, two techniques have been reported recently: the integrated notch-band technique and dual-band technique. In [1,2], open circuited stubs are integrated with the UWB BPF to generate desired notching bands; in [3,4], UWB BPFs with notching bands are designed using asymmetric coupled lines with the multiple-mode resonator technique; compact notched-band UWB BPFs are reported in [5, 6] by integrating notching resonators on a multilayer structure, and a dual-band UWB BPF is investigated in [7] by using multiple-mode stepped impedance resonators.This Letter presents a novel dual-band UWB BPF with compact size using multilayer liquid crystal polymer (LCP) technology. The LCP technology is a promising technology that has much lower fabrication cost than that of low temperature cofire ceramic technology and provides multilayer integration capability to implement compact multilayer threedimensional microwave circuits [2,6]. Moreover, LCP films have excellent electrical and mechanical performance, including small thermal expansion coefficient, low dielectric constant and low dielectric loss in a wide frequency range up to millimetre-wave. In this design, by taking advantage of multilayer LCP technology, broadside-coupled patches are adopted to design the ultra-wideband bandpass filter and quarter-wavelength resonators are integrated underneath broadsidecoupled patches to design the desired stopband. As a demonstration, a dual-band UWB BPF is designed, fabricated and measured. Presented predicted and measured results show the proposed filter has good performance, including compact size and good filter characteristic.

Compact dual‐wideband bandpass filter using asymmetrical resonator

“…A novel dual‐wideband bandpass filter designed to control centre frequencies and bandwidths by using short‐circuited SIRs has been presented [3]. In [4], a multilayer structure of LCP was used to integrate the broadside‐coupled patches and quarter‐wavelength resonators. Then, the UWB and stopband performance were introduced to the dual‐wideband response.…”

“…Introduction: Much research into dual-wideband bandpass filters with compact size, good passband selectivity, and sharp rejection is needed for UWB (ultra-wideband) applications. Recently, many methods have been employed to develop dual-wideband bandpass filters, including printed circuit board (PCB) technology [1][2][3], liquid crystal polymer (LCP) lamination technology [4], and low-temperature co-fired ceramic (LTCC) [5,6]. In [1], a stub embedded into the broadsidecoupled microstrip conductors was realised to introduce the dual-band performance.…”

Design of a dual‐band bandpass filter with a wide stopband

“…Zhang and Xue [2] further propose the single-ring resonator, a simpler structure than the stacked dual-mode resonator, to design the dual-mode dual-band bandpass filter. Moreover, stepped-impedance resonators (SIRs) [3,4] are widely utilised for dual-band filters because the SIR resonance at selected harmonics results in dual passbands along a single path. In terms of circuit size, the dual-band filters can be miniaturised with the open/short quarter-wavelength SIRs [5,6].…”

Dual-band UWB filter with LTCC technology

“…However, the notched UWB filter can make a very narrow stopband. In [7], a dual-band UWB filter was presented using broadsidecoupled patches and integrated quarter-wavelength resonators. In [8], a dual-band UWB filter was realised through a combination of one low-frequency and one high-frequency bandpass filter.…”