Acoustic Wave Filter Technology-A Review Ruppel, Clemens C. W.
IEEE transactions on ultrasonics, ferroelectrics, and frequency control,
09/2017, Letnik:
64, Številka:
9
Journal Article
Recenzirano
Today, acoustic filters are the filter technology to meet the requirements with respect to performance dictated by the cellular phone standards and their form factor. Around two billion cellular ...phones are sold every year, and smart phones are of a very high percentage of approximately two-thirds. Smart phones require a very high number of filter functions ranging from the low double-digit range up to almost triple digit numbers in the near future. In the frequency range up to 1 GHz, surface acoustic wave (SAW) filters are almost exclusively employed, while in the higher frequency range, bulk acoustic wave (BAW) and SAW filters are competing for their shares. Prerequisites for the success of acoustic filters were the availability of high-quality substrates, advanced and highly reproducible fabrication technologies, optimum filter techniques, precise simulation software, and advanced design tools that allow the fast and efficient design according to customer specifications. This paper will try to focus on innovations leading to high volume applications of intermediate frequency (IF) and radio frequency (RF) acoustic filters, e.g., TV IF filters, IF filters for cellular phones, and SAW/BAW RF filters for the RF front-end of cellular phones.
A class of multi-resonant RF filtering stage that exhibits a multi-band bandpass filtering transfer function with embedded in-band notches is presented. It is derived from the application of a ...composed lowpass-to-multi-passband/multi-stopband frequency transformation that converts the normalized lowpass prototype into the proposed multi-passband/multi-embedded-notch filtering cell. Thus, when employed in higher-order filtering networks, high-selectivity multi-band bandpass-filter (BPF) counterparts with embedded in-band stopbands are synthesized. Furthermore, two different approaches for out-of-band transmission-zero (TZ) generation in these type of filters to achieve sharp-rejection characteristics into them are detailed. The operational foundations of the engineered multi-passband/multi-embedded-notch filtering stage are described, along with several illustrative first-to-multi-order theoretical design examples with/without stopband TZs. Moreover, for experimental-demonstration purposes, a proof-of-concept microstrip prototype of a third-order dual-band BPF with two and one embedded notches in its lower and upper transmission bands, respectively, is manufactured and characterized.
This work presents a design technique to implement miniaturized cross-coupled bandpass filters in inline physical configurations based on triple-mode resonators. Triple-mode resonances are obtained ...by using integrated coaxial-waveguide cavity resonators. They consist of two coaxial conducting posts placed in the sidewalls of a rectangular waveguide cavity. In the proposed triplet, a transmission zero (TZ) can be positioned at any of the two sides of the passband by simply locating the coaxial posts either on the same wall or on opposite walls of the rectangular waveguide cavity. Coaxial-to-waveguide mode coupling is implemented by means of coupling screws, which adds flexibility in terms of tuning easiness. Three 9.9-GHz proof-of-concept prototypes corresponding to third- and sixth-order integrated coaxial-waveguide bandpass filters are designed at the electromagnetic-simulation level. Furthermore, the triplet with a TZ below the passband is manufactured and characterized to experimentally validate the engineered 3-D RF filter principle and its underlying design theory.
A novel arbitrary-order absorptive balanced filter is presented in this letter. It consists of an <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula>-th order coupled-line ...bandpass filter with absorption networks terminated at its input-output ports. The absorption network is constructed by <inline-formula> <tex-math notation="LaTeX">N </tex-math></inline-formula> sections of coupled-lines and absorption resistors. With the proposed architecture, not only common-mode (CM) noise but also out-of-band differential-mode (DM) signal can be directed into the absorption network and dissipated on the resistors, realizing reflectionless characteristics for both CM and DM signals. Moreover, the proposed absorption network can greatly extend the reflectionless bandwidth compared to previously reported work. For demonstration, first-order, second-order, and third-order microstrip prototypes are fabricated and measured. The measured results show wide-band reflectionless performance for both CM noise and DM signal.
A class of RF multi-functional input-reflectionless dispersive-delay structure (DDS) with linear-type in-band group-delay variation and sharp-rejection bandpass-filtering capability is reported. It ...exploits a two-branch-channelized/balanced-type circuit with similar low-order reflective DDS units inside its channels, which are connected through input/output <inline-formula> <tex-math notation="LaTeX">\boldsymbol {3} </tex-math></inline-formula>-dB quadrature wideband couplers. The adopted DDS unit is based on a coupled-resonator network with a frequency-dependent cross-coupling. It introduces a pair of complex transmission zeros (TZs) to shape the intended in-band group-delay profile. Unequal transmission-line-based phase-shifting sections are also inserted at the outputs of both channels. In this manner, an input-absorptive behavior and selectivity enhancement with TZ generation are attained by means of transversal signal-interference techniques at the overall input and output nodes, respectively. Moreover, as the transfer-function phase term of the interference action in transmission is linear with frequency, the total group-delay pattern is defined by the DDS unit of the channels. As practical validation, a 1.5-GHz proof-of-concept microstrip prototype is constructed and tested.
A class of input reflectionless dual-behavior resonator (DBR)-based bandpass filters (BPFs) with reconfigurable center frequency, bandwidth, out-of-band attenuation, and intrinsic switching-off ...capabilities is reported. They exploit a complementary-duplexer approach, in which the resistively terminated bandstop-filter (BSF) channel dissipates the RF input signal energy that is not transmitted by the main BPF channel in its out-of-band region. Spectral reconfiguration is realized through the synchronous tuning of the counterpart resonators in the DBR-based BPF and BSF channels-i.e., without variable couplings-which results in a dynamic transmission-zero (TZ) reallocation process. The theoretical analysis of the first-order section and design examples for higher order schemes are presented. Furthermore, for experimental-validation purposes, a microstrip prototype that can be tuned within the frequency range 1.3-2 GHz is manufactured and characterized.
A millimeter-wave passive-integrated bandstop filter (BSF) with absorptive/reflectionless behavior is reported. It avoids the creation of RF-power reflections for filtered signals which can ...deteriorate earlier active stages in integrated RF front-end chains. It exploits a two-path transversal configuration in a multi-layer structure. Specifically, it is composed of a direct transmission line for the main path (top layer) and two lossy edge-grounded spiral-shaped resonators for the secondary path (bottom layer) that are coupled between them and to the main path. Thus, a sharp second-order stopband is created through destructive signal-interference effects between the two signal paths with intrinsic RF-power absorption within the volume of the lossy resonators. As practical validation, a 24.5-GHz on-chip millimeter-wave absorptive BSF circuit is built in a 0.13-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> SiGe bipolar complementary metal-oxide-semiconductor (Bi)-CMOS technology and tested. Close agreement between simulated and measured results for this on-chip BSF circuit is achieved.
A class of reflectionless RF bandpass filters (BPFs) with wideband quasi-constant in-band group-delay response in transmission for high-data-rate digital-communication systems is presented. These ...BPFs are developed by exploiting multilayer wideband microstrip-to-microstrip vertical transitions and lossy multi-section microstrip lines in complementary-diplexer-based architectures. A two-port-reflectionless wideband BPF with low-in-band-variation equi-ripple-type group-delay characteristics is firstly realized by using two resistively-terminated one-section microstrip lines. To further flatten its passband group delay, its counterpart based on lossy two-section microstrip lines is then conceived to attain extremely-flat wideband group-delay pattern. Subsequently, by means of a modified wideband microstrip transition with a short-circuit-ended two-section microstrip line and a resistively-terminated two-section microstrip line, an input-reflectionless BPF with two close-to-passband transmission zeros (TZs) and wideband in-band flat group-delay profile is reported. In order to obtain a higher-order flat-group-delay wideband BPF response with more TZs, its structure shaped by two in-series-cascaded units of the previous input-absorptive BPF section with two TZs is engineered, in which different impedance values for their constituent short-circuit-ended microstrip lines are utilized. The operational foundations of all the proposed wideband flat-group-delay RF BPFs are described in detail. Furthermore, for practical-validation purposes, three 2-GHz microstrip prototypes of these reflectionless wideband RF BPFs with quasi-constant group-delay responses beyond their 3-dB absolute bandwidths (BWs) are designed, simulated, manufactured, and characterized.
<inline-formula><tex-math notation="LaTeX">AC</tex-math></inline-formula> power filters play an important role in limiting the high-frequency current harmonics injected by grid-tied voltage source ...converters (VSCs). Amongst the various types of filters, <inline-formula><tex-math notation="LaTeX">LCL</tex-math></inline-formula> filters with integrated <inline-formula><tex-math notation="LaTeX">LC</tex-math></inline-formula> traps have become popular due to their ability to achieve a size reduction of the grid side inductor while demonstrating a similar current harmonic mitigation performance as a traditional <inline-formula><tex-math notation="LaTeX">LCL</tex-math></inline-formula> filter. In this article, a passively damped filter network with a partially rated <inline-formula><tex-math notation="LaTeX">LC</tex-math></inline-formula> trap (also referred to as the <inline-formula><tex-math notation="LaTeX">L\text{-}PT\text{-}L</tex-math></inline-formula> filter) is proposed and delineated. The proposed <inline-formula><tex-math notation="LaTeX">L\text{-}PT\text{-}L</tex-math></inline-formula> filter provides a <inline-formula><tex-math notation="LaTeX">\text{-}60\;dB/dec</tex-math></inline-formula> roll-off characteristics at frequencies greater than switching frequency. Additionally, it is also demonstrated that this proposed <inline-formula><tex-math notation="LaTeX">L\text{-}PT\text{-}L</tex-math></inline-formula> filter has smaller voltage ratings for two of its shunt-connected capacitor components due to the specific placement of the damping resistor. A systematic analysis of the proposed <inline-formula><tex-math notation="LaTeX">L\text{-}PT\text{-}L</tex-math></inline-formula> filter is elucidated to design and select the component parameters. Steady-state and transient experimental results captured from a grid-tied 2-Level, 3 <inline-formula><tex-math notation="LaTeX">\phi</tex-math></inline-formula> VSC prototype are provided to validate the grid current harmonic filtering capability, reduced voltage ratings of the two shunt capacitors and passive damping performance of the proposed <inline-formula><tex-math notation="LaTeX">L\text{-}PT\text{-}L</tex-math></inline-formula> filter. The proposed approach can achieve 19% and 36% filter shunt branch volume reduction for low voltage (208 V, 60 Hz) and medium voltage (4.16 kV, 60 Hz) grid-tied inverter systems, respectively, compared to state-of-the-art <inline-formula><tex-math notation="LaTeX">LCL</tex-math></inline-formula> filters with integrated <inline-formula><tex-math notation="LaTeX">LC</tex-math></inline-formula> traps.
Signal-interference single- and multiband bandpass-type transversal filtering sections (TFSs) with input- and two-port low-reflection (LR) behavior are reported. These LR TFSs consist of the ...following three parts: 1) a reflective-type TFS shaped by two in-parallel unequal length transmission line segments; 2) a lossy open-ended stub shunted at the input or both at the input and output nodes of the building reflective-type TFS for the input- and two-port-LR TFS cases, respectively; and 3) input/output power-matching transmission line sections. In this manner, the stopband RF-signal energy that is not transmitted by the reflective-type TFS is dissipated by the resistor(s) of the lossy open-ended stub(s) instead of being reflected back to the source. This allows LR capabilities to be obtained in the overall modified TFSs. The operational principles of the proposed input- and two-port-LR TFSs, along with theoretical design examples and their comparison, are presented. Moreover, multi-TFS-stage LR bandpass filters (BPFs) are shown. They are based on the in-series cascade of several LR TFSs to enlarge the bandwidth and power rejection levels of the stopbands while keeping their LR nature. For experimental validation purposes, microstrip prototypes of a three-TFS-stage BPF with broadened input-LR stopbands and a quintuple-band input-LR TFS are developed and characterized.
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