Pamir Alpay

LOW VOLTAGE TUNABLE BAND PASS FILTERS USING BARIUM STRONTIUM TITANATE PARALLEL PLATE CAPACITORS

ABSTRACT In this paper, we report the results of third order combline inter-digited band pass filters implemented with parallel plate barium strontium titanate (BST) capacitors on sapphire substrates with platinum electrodes. The frequency characteristics of the filters were simulated using Sonnet software package. The resonators were implemented on FR-4 substrates using a LPKF rapid prototyping machine. The resonators were loaded with BST capacitors prepared on sapphire substrates by metalorganic decomposition (MOD). The measured center frequency of the filters was 1.35 GHz with a 3 db bandwidth of 0.15 GHz for zero bias voltage to the ferroelectric capacitors. The center frequency can be tuned from 1.35 GHz to1.45 GHz for an applied tuning voltage of 3 Volts.

Tunable and switchable bulk acoustic resonator with graded BST composition

ABSTRACT In this paper, we are presenting the results on tunable and switchable graded composition BaxSr1-xTiO3 (x = 0.6 to 0.90) film bulk resonators (FBARs) based on Silicon dioxide/Tantalum oxide Bragg reflectors. The Bragg reflectors can withstand high temperatures of about 800°C during annealing of graded barium Strontium Titanate (BST) film. BST films as well as Bragg reflectors were all deposited by spin on technique. The DC bias-dependent resonance frequency due to electro-restriction of the graded BST film decreases with increasing bias field and the tunability is about 2% for an applied bias voltage of 14 V. The calculated electromechanical coefficient for these resonators increases with applied bias and the maximum value of 12.5% is reached for a bias voltage of 10 V. The maximum quality factor ‘Q’ for these devices was 80 at a bias voltage of 13 V.

Switchable and tunable resonators with barium strontium titanate on GaN/Sapphire substrates

A solidly mounted tunable barium strontium GaN/Sapphire substrate using a metalorganic solution deposition (MOSD) technique. An acoustic Bragg reflector was first formed on the GaN/sapphire substrate consisting of alternating layers of silicon dioxide and tantalum oxide deposited using a-spin on technique. Lower and upper electrodes were fabricated using sputter deposited platinum. The resonant frequency of the resonator could be tuned from 5.17 GHz to 5.20 GHz by applying a voltage of 8 V, resulting in tunability of about 0.6%. The quality factor of the resonator was found to depend on the applied voltage, with a maximum quality factor of 216 observed for an applied bias voltage of 8 V. The effective electromechanical coupling coefficient (kt2) of the resonator was found to be 13.1% at 8 V.

Switchable band pass BAW filter based on Ba 0.7 Sr 0.3 TiO 3 for C band RF applications

This paper presents the design and fabrication of a switchable band pass filter based on barium strontium titanate (Ba0.7Sr0.3TiO3) thin film materials. This filter is designed and fabricated as a solidly mounted resonator (SMR) using spin-on metal organic solution decomposition. It consists of six film bulk acoustic resonators (FBARs), two series and four shunt. Without voltage biasing, there is no frequency switching and the filter has shown capacitive response of return loss S11 at -3 dB and insertion loss of -21 dB. By applying 10.8 dc voltage to the six resonators, the filter has exhibited band pass response at 4.67 GHz with 150 MHz band width and insertion loss of 3.8 dB and shown an agreement between the simulation and measurement results.