Tunable dual-mode filter using varactor and variable ring resonator on integrated BST/TiO2/Si substrate

Abstract

A RF tunable dual-mode filter employing a BST (Ba x Sr 12x TiO 3 )-based ring resonator and a capacitor is proposed. BST thin film was deposited on TiO 2 /Si substrate and a TiO 2 buffer layer grown by ALD (atomic layer deposition). The device with a BST varactor capacitance of 0.5 pF and 40% of tunability applied voltage of 40 V, and a tunable ring resonator frequency of 1.53 -2.02 GHz with a bias of up to 40 V, has been realised. The fabricated bandpass filter has a centre frequency of 1.53 GHz and shows a tunability of approximately 20% with an applied voltage of 40 V. It also has a bandwidth of 74 MHz and shows a tunability of approximately 27% with an applied voltage of 40 V.Introduction: Tunable dielectric-based RF device technology is one of the suitable solutions for intelligent RF applications satisfying multiband or multimode standards. Specifically, barium strontium titanate, Ba x Sr 12x TiO 3 (BST), is being investigated with considerable interest as a dielectric material for tunable microwave device applications owing to its large field dependent permittivity, high dielectric constant, and relatively low loss tangent. By using these advantageous properties of BST, a number of advanced tunable capacitors have been successfully demonstrated and integrated into RF components, such as phase shifters and RF filters [1][2][3][4][5][6].In this Letter, we present a tunable dual-mode bandpass filter using ferroelectric varactor and ring resonator perturbation. We obtained high tunability and improved microwave properties of BST films on Si by an atomic layer deposition (ALD)-grown TiO 2 buffer layer [2-4] and compared BST films on MgO single crystal substrate by PLD (pulsed laser deposition). Through the simulation and measurement results, it is shown that RF tunable bandpass filters can be applicable to the dual-mode ring resonator with BST varactor design.

Cognitive Radio RF: Overview and Challenges

“…In this direction, some solutions have been proposed, for example, a tunable integrated duplexer in [20], tunable RF BAW filters in [21], using metamaterials as BST in [22], or RF MEMS [23]. However the performances are not good enough and the tuning range is quite small.…”

Cognitive radio systems: Overview and challenges

“…In this direction, some solutions have been proposed e.g. a tunable integrated duplexer in [16], tunable RF BA W filters in [17], using meta-materials as BST in [18], or RF MEMS [19]. However the performances are not good enough and the tuning range is quite small.…”

Tunable dual‐mode microstrip patch resonators and filters

“…Tunable or reconfigurable microwave devices are in great demand for intelligent RF applications because of their advantages in improving the capability of wireless systems [1][2][3][4][5][6][7][8]. Microwave bandpass filters (BPFs) as essential microwave components are accordingly required to have adjustable frequency response.…”

“…Microwave bandpass filters (BPFs) as essential microwave components are accordingly required to have adjustable frequency response. In the designs of microstrip BPFs, dual-mode resonators with ring, loop and patch structures are more attractive because of their half-reduced number of resonators and compact filter configurations, compared with single-mode resonators [4][5][6][7][8][9][10][11][12][13]. The BPFs designed by using dual-mode patch resonators show higher power-handling capability than those using ring or loop resonators [8][9][10][11][12][13].…”

“…The BPFs designed by using dual-mode patch resonators show higher power-handling capability than those using ring or loop resonators [8][9][10][11][12][13]. Lots of effort has been done for tunable single-mode patch resonators [3] and for dual-mode ring or loop resonators [4][5][6]. In [7], a dual-mode reconfigurable filter using a patch resonator provides two switchable passbands by using a set of p-i-n diodes in series configuration to connect or isolate the loaded stubs to the patch.…”