Bandwidth Improvement Methods In Acoustically-Coupled Thin Film BAW Devices

Kulkarni, Vinay; Prasad, Kanti; Barber, Bradley P.

doi:10.1109/freq.2006.275371

Cited by 3 publications

(3 citation statements)

References 6 publications

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“…They can be further simplified by means of some common rules used in the BAW filter design. One is setting the acoustical length of electrodes

θ_{e}

small enough than that of the piezoelectric layers

θ_{p}

, which is beneficial to ensure high

k_{e f f}^{2}

for the BAW resonators 23 . Another point is that electrodes material with high acoustic impedance

Z_{e}

should be adopted, while the acoustic impedance of coupling layer

Z_{l}

should be low enough compared with

Z_{e}

to form a large acoustic impedance mismatch and reduce energy leakage from the surfaces of BAW resonators.…”

Section: Crf Configuration and The Modified Crf‐bvd Modelmentioning

confidence: 99%

“…One is setting the acoustical length of electrodes θ e small enough than that of the piezoelectric layers θ p , which is beneficial to ensure high k 2 ef f for the BAW resonators. 23 Another point is that electrodes material with high acoustic impedance Z e should be adopted, while the acoustic impedance of coupling layer Z l should be low enough compared with Z e to form a large acoustic impedance mismatch and reduce energy leakage from the surfaces of BAW resonators. The Z l is also smaller than the acoustic impedance of piezoelectric layer Z p for good filter selection performance.…”

Section: Modification Of the Crf-bvd Model By Taking Electrodes Into ...mentioning

confidence: 99%

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Synthesis of wideband bulk acoustic wave coupled resonator filter combined with lumped components

Xie

et al. 2022

Circuit Theory & Apps

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A novel wideband bulk acoustic wave (BAW) coupled resonator filter (CRF) combined with external lumped inductors and capacitors is proposed. The filter synthesis method based on the Butterworth-van Dyke (BVD) model of CRF (CRF-BVD) is also presented. To improve the synthesis accuracy, the CRF-BVD model is modified and the CRF configuration with a single rather than the traditional multiple coupling layer is adopted in this paper. By establishing equivalence relationships between the modified CRF-BVD model and the filter prototype synthesis network, exact CRF dimensions are solved through a set of equations without any further parameters tuning. The proposed method exhibits a maximum 37.4% (FBW) for a Chebyshev filter with 9.4-dB return loss, which overcomes the narrowband limitation of regular BAW filters with FBW below 5%. To demonstrate the synthesis procedure, an n77 band filter with 3.723-GHz center frequency and 24.2% FBW is designed and simulated. Good agreements are obtained among the simulation results of the prototype synthesis network, the modified CRF-BVD model, and the cosimulations of physical model based on the finite element method (FEM) and the CMOS 130-nm technology.bulk acoustic wave, coupled resonator filter, filter synthesis, wideband filter | INTRODUCTIONBulk acoustic wave (BAW) filters have been identified as one of the best filter options for front-end circuits in wireless mobile communication systems owing to their ultrasmall size, low insertion loss (IL), steep skirt selectivity, and high power handling capability. 1,2 However, the bandwidth of BAW filters is limited by the effective electromechanical coupling coefficient k 2 ef f of BAW resonators. 3,4 The k 2 ef f must be at least double the fractional bandwidth (FBW) of a radio band. Therefore, the commercialized aluminum nitride (AlN) based BAW filter with k 2 ef f less than 7% can only reach a fractional bandwidth (FBW) below 3.5%. 5 With mobile communication evolving into the 5G era, some new bands with large FBW such as n79 (12.8% FBW), n78 (14.8% FBW), and n77 (24.2% FBW) have been proposed. Such wide bandwidths are hard to achieve with regular BAW filters. 6,7 To improve the bandwidth of BAW filters, some approaches have been developed. One is adding auxiliary inductors in series/parallel with the shunt/series resonators. 8,9 However, the bandwidth cannot be extended too much due to the limited distance between the transmission zeros at the lower and upper sides of the passband. Unexpected passbands also appear in the stopband range and affect the broadband rejection performance. 10 One method is employing

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“…They can be further simplified by means of some common rules used in the BAW filter design. One is setting the acoustical length of electrodes

θ_{e}

small enough than that of the piezoelectric layers

θ_{p}

, which is beneficial to ensure high

k_{e f f}^{2}

for the BAW resonators 23 . Another point is that electrodes material with high acoustic impedance

Z_{e}

should be adopted, while the acoustic impedance of coupling layer

Z_{l}

should be low enough compared with

Z_{e}

to form a large acoustic impedance mismatch and reduce energy leakage from the surfaces of BAW resonators.…”

Section: Crf Configuration and The Modified Crf‐bvd Modelmentioning

confidence: 99%

Section: Modification Of the Crf-bvd Model By Taking Electrodes Into ...mentioning

confidence: 99%

Synthesis of wideband bulk acoustic wave coupled resonator filter combined with lumped components

Xie

et al. 2022

Circuit Theory & Apps

View full text Add to dashboard Cite

show abstract

“…One is choosing electrodes with high acoustic impedance Z e and small acoustical length θ e , which is beneficial to ensure high k 2 eff for the BAW resonators. 27 Another point is that the Z l should be low enough compared with Z e to form a large acoustic impedance mismatch and reduce energy leakage from the surfaces of BAW resonators.…”

Section: The Simplified Mason Modelmentioning

confidence: 99%

A novel wideband multi‐mode coupled resonator filter based on bulk acoustic wave technology

Xie

et al. 2021

Int J RF Mic Comp-Aid Eng

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This paper proposes a novel multi-mode bulk acoustic wave (BAW) coupled resonator filter (CRF) for wideband applications. Three stepped-impedance coupling layers of CRF are used to generate multi-mode properties, and external inductors are added for port match. To facilitate the calculation of resonance frequencies, a simplified Mason model is derived and applied in the even-and odd-mode analysis of CRF. Based on different acoustical length of CRF coupling layers, four cases that are applicable for different filter bandwidth are proposed. From these cases, fractional bandwidth (FBW) of the multi-mode CRF can be realized in a wide range from 12.8% to 33% when the coupling layers adopt the commonly used SiO 2 /Mo/SiO 2 materials. Moreover, the tuning range of FBW can be further enlarged by changing the materials of coupling layers. To verify the proposed multi-mode CRF, a triple-mode n77 band filter with center frequency of 3.723 GHz and FBW of 24.2%, and a penta-mode filter with a larger FBW up to 33% are designed and simulated.Simulation results of the original Mason model, the simplified Mason model, and the three-dimensional (3D) model based on the finite element method are consistent well with each other.

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Inductive coupling for increased bandwidth of aluminum nitride contour-mode microresonator filters

Nordquist¹,

Henry²,

Nguyen³

et al. 2016

2016 IEEE MTT-S International Microwave Symposium (IMS)

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Bandwidth Improvement Methods In Acoustically-Coupled Thin Film BAW Devices

Cited by 3 publications

References 6 publications

Synthesis of wideband bulk acoustic wave coupled resonator filter combined with lumped components

Synthesis of wideband bulk acoustic wave coupled resonator filter combined with lumped components

A novel wideband multi‐mode coupled resonator filter based on bulk acoustic wave technology

Inductive coupling for increased bandwidth of aluminum nitride contour-mode microresonator filters

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