33 GHz Overmoded Bulk Acoustic Resonator

This paper reviews the latest developments in microwave acoustic wave devices. After an introduction and brief history of bulk acoustic wave (BAW) and surface acoustic wave (SAW) devices, a review is given for guided SAWs and XBARs -two new technologies, which are promising for future 5G applications. Following this, we discuss recent simulation techniques, such as 3D finite element method (3D FEM) and simulation of nonlinearities, as well as filter synthesis. Next, a review on tunable and reconfigurable acoustics is given. Finally, we present the latest developments in microwave acoustics for millimeter-wave (mm-wave) operation as well as BAW oscillators.INDEX TERMS Bulk acoustic wave (BAW) devices, filter, filter-synthesis, front-end, high power, MTT 70th Anniversary Special Issue, multiplexer, nonlinearity, resonator, surface acoustic wave (SAW) devices.

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“…In [126] for the first time, an Overmoded Bulk Acoustic Resonator (OBAR) (Fig. 28) for mm-wave acoustic filtering was presented.…”

Section: B the Overmoded Bulk Acoustic Resonatormentioning

confidence: 99%

From Microwave Acoustic Filters to Millimeter-Wave Operation and New Applications

et al. 2023

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“…In other words, it is optimal to have the ratio between piezoelectric stress coefficient and permittivity spatially correlated to the strain profile of the desired mode, as is discussed in existing designs [1], [2], [4], [5]. Therefore, when designing multilayer structures, it is preferable to have the material interfaces placed at the zero strain locations, resulting in half wavelength per layer at the eigenfrequency ω i (the parallel resonance frequency).…”

Section: A Electrical Excitation Of Vibrations In An Fbarmentioning

confidence: 99%

“…Recent efforts in pushing the maximum operating frequencies of FBARs demonstrate that another approach is to use a higher order mode in an FBAR where a boost in electromechanical coupling coefficient is achieved with forward and reverse axis piezoelectric layers [2]- [4]. A previous work observed through simulations that for these resonators with thick electrodes, low characteristic acoustic impedance are preferred in electrodes in an overmoded structure [1]. Other works discussed mode selection in a multilayer structure with alternating polarities of identical piezoelectric layers but simplified the contribution of electrodes in their discussions [5].…”

Section: Introductionmentioning

confidence: 99%

Electrode Effects in mmWave Frequency Multilayer Bulk Acoustic Wave Resonators

Peng¹

2023

Preprint

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<p>Electrodes are present in acoustic resonators to set electrical boundary conditions. Electrodes are acoustically part of a bulk acoustic wave (BAW) resonator that affect both its electromechanical coupling coefficient and its quality factor. Calculation of electromechanical coupling coefficient in multilayer structures requires the analysis of a system of equations relating the waves inside each layer to those in its adjacent layers. In this work, layer thicknesses and material constants in each layer are used to calculate the series and parallel resonance frequencies. Due to the proximity in frequency of series and parallel resonance, a series expansion of the series resonance frequency equation is performed around the parallel resonance frequency, and a closed form expression for electromechanical coupling coefficient from material constants and layer thicknesses is obtained to facilitate the observation of the electromechanical coupling coefficient effects of electrodes. Thermoelastic damping (TED) has been identified as the dominant acoustic loss mechanism in conductors. In this work, the complex wavenumber is calculated based on the unified theory of thermoelasticity to incorporate acoustic loss due to the interaction between elastic deformation and heat flow. Acoustic quality factors due to TED for common metals in microelectromechanical systems (MEMS) processing are calculated to facilitate the observation of the quality factor effects of electrodes. It is observed that there exists tradeoff among electromechanical coupling coefficient, acoustic quality factor, and electrical conductivity in the selection of electrode metals.</p>

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“…FBARs combine high Q and k 2 t , allowing for the synthesis of highly selective and low Insertion Loss (IL) band-pass filters [20]. FBAR overtones have been shown to reach 33 GHz [21] and microacoustic filters have been demonstrated above 20 GHz [22]. Moreover, they can count on a standardized large-scale fabrication process [23].…”

Section: Introductionmentioning

confidence: 99%

Compact and wideband nanoacoustic pass-band filters for future 5G and 6G cellular radios

Giribaldi

Colombo

Simeoni

et al. 2023

Preprint

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The last half a century has seen an enormous growth in mobile communication, reflecting into an increasingly interconnected world. Nevertheless, the incessant demand for faster data-rates requires a shift to higher carrier frequencies, which translates to the need for more ubiquitous hardware due to the increased wave propagation losses. The 7-20 GHz range, located between the sub-6 GHz (5G FR-1) and the mm-wave (5G FR-2) spectrum, provides an excellent trade-off between network capacity and coverage. Such spectrum portion constitutes a yet-to-explore third frequency range (FR-3) for future 5G applications, and is foreseen to become the 6G mid-band, devoted to crowded urban area coverage. This work proposes a technological platform able to deliver CMOS-compatible, on-chip multi-frequency low-loss, wideband, and compact passband filters for cellular radios operating at mid-band frequencies, exploiting the micro-to-nano scaling of acoustic electromechanical resonators and filters. The presented results showcase the first-ever demonstrated low insertion loss bank of 7 nanoacoustic passive passband filters in the X-band, spanning more than 3 GHz of operation, all fabricated on the same substrate with state-of-the-art and low-complexity micro-machining process. Most of the filters showcase fractional bandwidths above 3% and sub-dB loss per stage, all in an extremely compact form factor, enabling the manufacturing of X-band filters and duplexers that can be integrated in mobile handsets at each antenna element. The novelty of the current results stems from the adoption of a high-crystallinity piezoelectric Sc-doped AlN thin film, together with an optimized resonator topology in terms of design and fabrication.

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33 GHz Overmoded Bulk Acoustic Resonator

Cited by 54 publications

References 17 publications

From Microwave Acoustic Filters to Millimeter-Wave Operation and New Applications

From Microwave Acoustic Filters to Millimeter-Wave Operation and New Applications

Electrode Effects in mmWave Frequency Multilayer Bulk Acoustic Wave Resonators

Compact and wideband nanoacoustic pass-band filters for future 5G and 6G cellular radios

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