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WO2004066494A1 - Structure de filtre de resonateur a equilibrage ameliore - Google Patents

Structure de filtre de resonateur a equilibrage ameliore Download PDF

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Publication number
WO2004066494A1
WO2004066494A1 PCT/IB2003/006226 IB0306226W WO2004066494A1 WO 2004066494 A1 WO2004066494 A1 WO 2004066494A1 IB 0306226 W IB0306226 W IB 0306226W WO 2004066494 A1 WO2004066494 A1 WO 2004066494A1
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Prior art keywords
resonator
elements
filter structure
lattice
resonator filter
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English (en)
Inventor
Hendrik K. J. Ten Dolle
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Koninklijke Philips NV
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Koninklijke Philips Electronics NV
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Priority to AU2003285700A priority Critical patent/AU2003285700A1/en
Publication of WO2004066494A1 publication Critical patent/WO2004066494A1/fr
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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/0023—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output
    • H03H9/0095—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output using bulk acoustic wave devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/0023—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output
    • H03H9/0028—Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns, or networks having balanced input and output using surface acoustic wave devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6423—Means for obtaining a particular transfer characteristic
    • H03H9/6433—Coupled resonator filters
    • H03H9/6483—Ladder SAW filters

Definitions

  • the present invention relates to a resonator filter structure according to the preamble of claim 1.
  • the invention relates to a resonator filter structure arranged for providing a passband which can be defined by frequencies as a center frequency fc, a lower cut off frequency f_, a upper cut off frequency fu comprising between an input port and an output port at least one resonator filter section with first resonator elements having a resonance frequency fi R and an anti-resonance frequency fi A and with second resonator elements having a resonance frequency f R and an anti-resonance frequency f 2A -
  • RF filter structures which despite the increasing miniaturization should be able to withstand considerable power levels, have steep passband edges, and low losses. Due to use of high frequencies in the range of GHz special circuit elements for building RF filter structures are required and high frequency related concerns have to be dealt with.
  • receive band filters for modern telecommunication standards need steep transition from stopband to passband since Tx and Rx are closely separated.
  • extended GSM EGSM
  • the Rx and Tx bands are centered at 942.5 and 897.5 MHz, respectively. Both of these have a bandwidth of 35 MHz, resulting in fractional bandwidth of 3.71% and 3.9% for the Rx and Tx, respectively.
  • GPS or TV up conversion filter require even smaller bandwidths. Accordingly, it is known to use mechanical resonator characteristics in filter circuits for electrical signals. These resonators can be divided into two classes that are derived from the utilized kind of mechanical vibration.
  • SAW Surface Acoustic Wave
  • a SAW resonator typically comprises a piezoelectric solid and two interdigitated structures as electrodes.
  • Various circuits as filters or oscillators containing resonator elements are produced with SAW resonators, which have the advantage of very small size, but unfortunately a weakness in withstanding high power levels.
  • a mechanical vibration of a bulk material is used which is sandwiched between at least two electrodes for electrical connection.
  • the bulk material is a single piezoelectric layer (piezo) disposed between the two electrodes.
  • piezo piezoelectric layer
  • the entire bulk material expands and contracts, creating the mechanical vibration.
  • This vibration is in the bulk of the material, as opposed to being confined to the surface, as is the case for SAWs. Therefore, such elements are called Bulk Acoustic Wave (BAW) resonators.
  • BAW resonators are often employed in bandpass filters having various topologies.
  • BAW resonator elements are thin film bulk acoustic resonators, so called FBARs, which are created using a thin film semiconductor process to build the metal-piezo-metal sandwich in air in contrast to the afore-mentioned BAWs, which are usually solidly mounted to a substrate.
  • FBARs thin film bulk acoustic resonators
  • the electrical behavior of a SAW or BAW resonator is quite accurately characterized by the equivalent circuit, which is shown in the accompanying Fig. 5.
  • Fig. 5 there is a branch comprising a series combination of an equivalent inductance Ls, an equivalent capacitance Cs, and an equivalent resistance Rs.
  • Ls and Cs are the motional inductance and capacitance respectively and Rs represents the acoustic losses of the resonator.
  • each SAW or BAW resonator comprises two characteristic resonance frequencies, which is a series resonance frequency and a parallel resonance frequency. The first is mostly called resonance frequency f R and the second is also known as anti-resonance frequency f A .
  • Circuits comprising BAW or SAW elements in general are better understood in view of above-introduced element equivalent circuit.
  • the series resonance of the individual resonator element is caused by the equivalent inductance Ls and the equivalent capacitance Cs. At frequencies that are lower than the series resonance frequency, the impedance of the resonator element is capacitive.
  • the impedance of the resonator element is inductive. Also, at higher frequencies than the parallel resonance frequency impedance of the resonator element is again capacitive.
  • the impedance characteristic of the resonator element with respect to signal frequency at the (series) resonance frequency f R of the resonator element, the impedance of the resonator element is low, i.e. in an ideal case, where there are no losses in the element, the resonator element functions like a short circuit.
  • the impedance of the resonator element is high, i.e. in an ideal case without losses the impedance is infinite and the device resembles an open circuit at the anti-resonance frequency. Therefore, the resonance- and anti-resonance frequencies (f R and f A ) are important design parameters in filter design.
  • the resonance and anti-resonance frequencies are determined by process parameters like the thickness of the piezoelectric layer of each resonator element and/or the amount of massloading.
  • a first known filter type with BAW resonator elements is constructed in a topology known as ladder type topology.
  • BAW ladder filters For the purposes of this description, ladder type filters that are built primarily of BAW resonator elements are referred to as "BAW ladder filters”.
  • BAW ladder filters are typically made so that one or more BAW resonators are series-connected within the filter and one or more BAW resonators are shunt-connected within the filter.
  • a BAW ladder filter is typically designed so that series-connected resonators also called “series resonators”, yield series resonance at a frequency that is approximately equal to, or near, the desired, i.e. design or center, frequency of the respective filter.
  • shunt-connected resonators also referred to as “shunt resonators” or “parallel resonators” yield parallel resonance at a frequency that is approximately equal to, or near, the desired center frequency of the respective filter.
  • a second known circuit topology for filters is the BAW lattice circuit, which circuit topology is also called balanced bridge design.
  • BAW lattice circuit has a stopband when all branches have approximately equal impedance and a passband when one branch type, i.e. the series arm or the lattice arm, respectively, behaves inductive and the other capacitive.
  • Fig. 6 shows the impedance characteristics of two different BAW resonator elements, BAW-1 and BAW-2, usually used in filter design.
  • BAW-1 and BAW-2 are made such, as anti-resonance frequency f ⁇ of BAW-1 is substantially equal to resonance frequency f R of BAW-2.
  • BAW resonator filters can be constructed, which have a passband approximately corresponding to the difference ⁇ f between the lowest resonance frequency, here f * R i, and the highest anti-resonance frequency, here BAW series and lattice resonator elements may be exchanged provided series or horizontal resonators are of one type and lattice or diagonal resonators are of the other type.
  • the bandwidth, i.e. the passband, of the thus created filter corresponds approximately to the difference between the highest anti-resonance frequency and the lowest resonance frequency of the used resonator elements.
  • BAW lattice circuits have the advantage that there is a deep stopband rejection far away from the passband.
  • impedance matching between circuits within the signal path is crucial.
  • impedance matching can be achieved by scaling BAW resonator areas.
  • LNA low noise amplifier
  • impedance matching requires also impedance transformation, e.g. from 50 ⁇ in to a 150 to 200 ⁇ differential-out.
  • balanced output is preferred as well; because usually low noise amplifiers (LNA) incorporated after receive filters often require a balanced input signal.
  • LNA low noise amplifier
  • a resonator filter structure which provides improved phase and amplitude balance. It is a further objective to have a resonator filter circuit, which has a steep transition from stopband to passband. Another objective is to provide impedance transformation between the impedance levels at input and output port of the resonator filter structure. Moreover, it is a further objective to have the input and output impedances of the resonator filter structure substantially matched with the respective loads.
  • a resonator filter structure of the present invention is characterized by means for balance improvement connected in cascade to a resonator filter section.
  • resonator elements can be used any circuit element which provides an impedance characteristic over signal frequency as is illustrated as an example in Fig. 6, where for two resonator elements BAW-1 and BAW-2 the impedance characteristic is shown, or as is expected from a circuit as shown in Fig. 5.
  • acoustic wave resonator elements more preferably are used bulk acoustic wave (BAW) resonator elements; surface acoustic wave (SAW) resonator elements may also be used.
  • BAW bulk acoustic wave
  • SAW surface acoustic wave
  • such a BAW resonator comprises a stack on a substrate with at least one or more acoustic reflective layer, a bottom electrode, a bulk, a top electrode, and an optional massload on top of the top electrode.
  • the bulk of the BAW resonator elements comprise a piezoelectric layer having a predetermined thickness and being made of an piezoelectric material such as aluminum nitride (A1N) or zinc oxide (ZnO) and having an optional additional dielectric layer, for instance, silicon oxide (SiO2).
  • the combination of silicon oxide (SiO2) and aluminum nitride (A1N) in the BAW resonators reduces the coupling coefficient of the BAW resonator elements, as required in some applications with respect, for instance, to bandwidth or temperature stability.
  • the thickness of the component layers of the bulk, and/or the massload, and/or the electrode layers for each BAW resonator element can be used to arrange the BAW resonator elements to have a predetermined resonance frequency and a predetermined anti-resonance frequency.
  • the frequency of acoustic vibration is approximately inversely proportional to the thickness of the piezoelectric layer.
  • the piezoelectric thickness is therefore of the order of 1 micron, so typically a thin-film semiconductor process is used.
  • the solidly-mounted bulk acoustic wave resonator (sometimes called SB AR) one or more acoustic layers are employed between the piezoelectric layer and the substrate.
  • An alternative embodiment of thin-film BAW resonator elements (sometimes called FBAR) employs a membrane approach with the metal-piezo- metal sandwich suspended in air. BAW resonators are often employed in bandpass filters having various topologies.
  • BAW resonators One advantage of BAW resonators is the intrinsically better power handling compared to the interdigitated structures used in surface acoustic wave (SAW) resonators, especially at frequencies of modern wireless systems where the pitch of the interdigital structures must be sub-micron.
  • SAW surface acoustic wave
  • the resonator filter structure is arranged for providing a passband which can be defined by frequencies as a center frequency fc, a lower cut off frequency fi-, a upper cut off frequency fu comprising between an input port and an output port at least one resonator filter section with first resonator elements having a resonance frequency fi R and an anti- resonance frequency fi A and with second resonator elements having a resonance frequency f 2R and an anti-resonance frequency f 2A -
  • the means for balance improvement comprise a LC-lattice section wherein inductive elements Lx and capacitive elements Cx, are arranged in lattice circuit configuration.
  • the inductive elements Lx are arranged as series elements of the LC-lattice section and the capacitive elements Cx are arranged as lattice elements of the LC- lattice section, or vice versa.
  • the resonator filter structure provides balanced signal guidance. It should be noted that the LC-lattice section can be included in the resonator filters structure at any position.
  • fc is the center frequency of the resonator filter structure
  • R ⁇ N is a input impedance level of the LC-lattice section
  • RO UT is a output impedance level of the LC-lattice section.
  • the LC-lattice section may comprise discrete circuit elements; preferably the LC-lattice section is made with passive integration technologies.
  • a resonator filter section is a resonator ladder filter section having one or more of the first resonator elements arranged as series arms alternating with at least one of the second resonator elements arranged as shunt arms.
  • a resonator ladder type filter section is connected to a balanced side of the means for balance improvement it is symmetrical constructed for providing balanced signal guidance, too.
  • a resonator filter section is a resonator lattice type filter section having the first resonator elements arranged as series arms and having the second resonator elements arranged as lattice arms.
  • series resonator elements and lattice resonator elements of a resonator lattice filter section may be exchanged, provided that series resonator elements are of one type and lattice resonator elements are of the other type.
  • a combination of a resonator ladder filter section and/or a resonator lattice filter section with a specific LC-lattice section according the invention which is designed for optimum balance at the filter center frequency fc, significantly improves the amplitude balance and phase balance in a frequency band which is large enough for communication standards like PCS.
  • the resonator filter structure there is a resonator lattice filter section having resonance frequencies and anti-resonance frequencies of the first and second resonator elements substantially equal. Further, there are capacitances connected in parallel across the lattice arm resonator elements or the series arm resonator elements. This way, very narrow filter bandwidth is realized by using only one type of resonator in the circuit having one resonance frequency and one anti-resonance frequency.
  • the processing is simplified by eliminating the step of creating an offset in resonance frequencies. For instance, all resonators can be made with same thickness of the piezoelectric layer and no massloading is required.
  • the series resonators of different filter sections may differ in area.
  • the capacitances C which are connected in parallel to one type of the resonator elements, advantageously move the anti-resonance frequencies of those resonators.
  • the capacitance value C is used to tune the bandwidth, wherein the smaller the capacitance, the smaller the bandwidth. It has further found by the inventors that to create a good stopband rejection, the total capacitance of all branches needs to be equal in the stopband.
  • the resonator filter structure comprises a resonator lattice filter section and at least one additional resonator ladder filter section.
  • Such combination of these two resonator filter sections adds the best of both topologies.
  • the transition from stopband to passband is much steeper than for a sole lattice design.
  • stopband rejection is much deeper than with a sole ladder design.
  • common mode rejection in stopband is equal to stopband rejection of the applied ladder sections.
  • the combination provides unbalanced-in to balanced-out, which is preferred for receive filters and fits to the LC-lattice section for balance improvement of the present invention.
  • unbalanced ladder section(s) are connected to the unbalanced port of the resonator filter structure and the lattice section(s) are connected to the balanced port of the resonator filter structure.
  • an unrestricted amount of balanced ladder sections can be connected between any two lattice sections or between the lattice sections and the balanced port of the resonator filter structure. It should be noted that the amount of ladder and lattice sections is in general unrestricted.
  • typically series resonators have the same resonance and anti-resonance frequencies, but may have different areas on the substrate of the respective device. Also all lattice or shunt resonator elements have the same resonance and anti-resonance frequencies, but may have different areas.
  • the resonance and anti-resonance frequencies (f R and f A ) of the resonator elements are related to the center frequency fc of the filter circuit. In other words: series resonator elements have a resonance frequency substantially equal to the center frequency and lattice or shunt resonator elements have a anti-resonance frequency substantially equal to the center frequency of the filter circuit.
  • impedance matching at the ports of the resonator filter structure there are arranged at the input port and/or the output port inductive elements and/or capacitive elements which are connected in series to and/or parallel across one of the or both of the input port and output port. It goes without saying that when input and output impedance levels are equal, impedance matching can be achieved by scaling the resonator areas. However, when input and output impedance levels are different, impedance matching requires impedance transforming by the resonator filter structure. The inventors have found that some impedance transformation can be achieved by the LC-lattice section as shown by the above-introduced equations for deriving applicable values for L and O ⁇ .
  • the output port is used as a balanced signal port while at the input port an unbalanced signal as well as a balanced signal can be applied, as it is needed in a specific application.
  • Balanced output is most preferred, because as already mentioned the filter often is connected to the balanced input of a low noise amplifier (LNA).
  • LNA low noise amplifier
  • the input port with the unbalanced signal guidance can be connected to a fixed reference potential, if needed, e.g. a ground potential of the circuit.
  • Fig. 1 shows a circuit diagram of a resonator filter structure wherein a BAW lattice filter section combined with a balanced BAW ladder filter section is connected in cascade to a LC-lattice section and inductances for matching purposes;
  • Fig. 2 depicts a second example for the resonator filter structure of Fig. 1 which is construction optimized;
  • Fig. 3 is a third example for a resonator filter structure wherein an unbalanced
  • BAW ladder filter section is connected to the unbalanced-in side of the LC-lattice section and a balanced BAW ladder filter section is connected to the balanced-out side of the LC-lattice section and inductances are used for matching purposes;
  • Fig. 4 illustrates a further optimization of a BAW lattice filter section providing very narrow filter bandwidth
  • Fig. 5 is an equivalent element circuit of an resonator element; and Fig. 6 shows the impedance characteristics of two BAW resonator elements drawn over signal frequency, wherein resonance frequencies, anti-resonance frequencies and filter center frequency are marked.
  • Fig. 1 shows a resonator filter structure 10 according to the present invention, which comprises a first port 1, which has a connection to a fixed reference potential being ground 5 of the circuit, and a second port 2. There is connected a first load 3 to the first port 1 and a second load 4 towards the second port 2.
  • the first load may represent an internal resistance of a generator that is driving a radio frequency (RF) signal as input for the resonator filter structure 10; in an application the generator, for instance, may be a receiving antenna of a communication unit.
  • the second load 4 represents the input resistance of a following stage like, for instance, a low noise amplifier (LNA).
  • LNA low noise amplifier
  • the first load is a 50 ⁇ resistance and the second load stands for a 200 ⁇ differential resistance.
  • the input impedances of the resonator filter structure have to be matched according to the respective loads 3 and 4, at least within the frequency band that corresponds to the resonator filter structure passband.
  • the passband is defined by a lower cut-off frequency, a center frequency, and an upper cut-off frequency, wherein a cut-off frequency could be derived by a certain signal power level to which the signal has decreased from passband towards the stopband.
  • the basic section of the resonator filter structure is a BAW lattice filter section 20, which comprises four BAW resonator elements 22a, 22b, 24a, 24b.
  • the structure of this BAW lattice filter circuit is constructed with the four BAW elements 22a, 22b, 24a, 24b in the known principle of bridge circuits.
  • respective two of the four resonator elements, i.e. 22a and 24a are connected in series building a first series path
  • 24b and 22b are connected in series building a second series path.
  • the connection nodes between two resonator elements of the first and second series path represent respective one output node of the resonator lattice circuit.
  • first and second series path of the bridge are connected in parallel to the input nodes of the resonator lattice circuit.
  • resonator elements 22a, 22b are also called horizontal elements or series elements of the lattice circuit
  • resonator elements 24a, 24b are also called diagonal elements or lattice elements of the lattice circuit.
  • each branch of the lattice circuit is called an arm of the lattice circuit, wherein horizontal element builds an horizontal or series arm, respectively, and diagonal element builds a diagonal or lattice arm, respectively.
  • both series arm BAW resonators 22a and 22b which are of a first resonator element according the invention, are equal, which means they have same resonance frequency i and same anti-resonance frequency f ⁇ i, and both BAWs 22a and 22b have an equal area on the substrate of the device.
  • both lattice arm BAW resonators 24a and 24b which are of a second resonator element according the invention, are equal, which means they have same resonance frequency f 2 and same anti-resonance frequency ⁇ /_> and both BAWs 24a and 24b have also an equal area size on the substrate.
  • the BAW lattice filter section has a desired center or design frequency fc in accordance to which the respective resonance and anti-resonance frequencies of the BAW elements 22a, 22b, 24a, and 24b are adapted.
  • resonance frequencies f * R i of the series arm BAW elements 22a and 22b are substantially equal to the center frequency fc of the resonator filter structure
  • anti-resonance frequencies f A2 of the lattice arm BAW elements 22a and 22b are substantially equal to the center frequency fc of the resonator filter structure.
  • BAW ladder filter section 30 comprising three BAW ladder elements 32a, 32b, 33. Due to the fact, that the output port 2 of the resonator filter structure is connected to a balanced input port of, for instance, a LNA, the BAW ladder filter section 30 provides balanced signal guidance. Therefore, the BAW ladder filter section 30 is symmetrically constructed with respect to the signal which is travelling in balanced condition and thus, both series BAW elements 32a and 32b have identically design parameters as equal area on the substrate of the device and the same resonant frequency fiu which is substantially equal to the center frequency fc of the RF filter structure 10.
  • the vertical or shunt BAW element of the BAW ladder filter section 30 has its anti-resonance frequency f ⁇ _ substantially equal to the center frequency fc of the resonator filter structure 10.
  • impedance matching section 50a On the left hand side of the BAW lattice filter section 20 is connected an impedance matching section 50a with two equal inductances 54a and 54b which are for impedance matching and therefore, will be described further below.
  • impedance matching section 50a there is a LC-lattice section 40, wherein the same naming convention as for a BAW lattice filter section applies.
  • the LC-lattice section 40 comprises two capacitances 42a and 42b as series arm elements and two inductances 44a and 44b as lattice arm elements.
  • the LC-lattice filter section 40 is according to its balanced bridge design in a balanced condition at the desired center frequency fc of the resonator filter structure 10.
  • the impedances of the inductances 44a and 44b and capacitances 42a and 42b are equal at the center frequency of the resonator filter structure 10.
  • the value C of the used capacitances 42a and 42b is derived from the formula:
  • the value Lx of the used inductances 44a and 44b is derived from the formula: , ⁇ — ⁇ f c wherein R I and R O U T are the impedance levels on the respective input and output side of the LC-lattice section.
  • the LC-lattice section 40 besides the BAW lattice filter section provides for impedance transformation between the input port 1 and the output port 2.
  • impedance matching at the input port 1 of the RF filter structure 10, there are impedance matching sections 50a and 50b, which are arranged for providing impedance matching simultaneously at the input port 1 and the output port 2 of the resonator filter structure.
  • the parallel inductance 56 is connected to the port with the high impedance level being the output port 2 of the resonator filter structure and the symmetrical constructed series inductances 54a and 54b are connected in series to the right side of the LC-lattice section 40 which transforms these series inductances 54a and 54b to the port with the low impedance level being the input port 1 of the RF filter device 10 where it has a effect as a parallel capacitance (as it will be shown in Fig. 2).
  • Fig. 2 shows basically the same resonator filter structure as in Fig. 1, therefore, only the differences will be described.
  • the resonator filter structure in Fig. 2 is a variation that has been found to be more optimal for process of manufacture.
  • the two equal inductances 54a and 54b of impedance matching section 50a on the right side of the LC- lattice section 40 in Fig. 1 have been transformed to a capacitance 54c being a matching section 50c on the left side of the LC-lattice section 40 in Fig. 2.
  • the capacitance 54c at the impedance matching section 50c and the capacitances 42a and 42b of the LC-lattice section 40 maybe combined on a single passive integration chip.
  • Fig. 3 shows another embodiment of a resonator filter with improved phase and amplitude balance within the passband according to the present invention.
  • Fig. 1 and also Fig. 2 there is as a main difference no BAW lattice filter section 20.
  • the central part of the resonator filter structure 10 is again formed by the LC-lattice section 40 which provides for change-over from unbalanced signal guidance on the left side to balanced signal guidance on the right side of the LC-lattice section 40 of the resonator filter structure 10.
  • the LC-lattice section 40 comprises the same construction as described with respect to Fig. 1 and Fig. 2.
  • BAW ladder filter section 30 On the right hand side of the LC-lattice section there is also a symmetrically arranged BAW ladder filter section 30 as known from Fig. 1 and Fig. 2. LC- lattice section 40 and BAW ladder filter section 30 will not be described again in greater detail. On the left hand side of the LC-lattice section 40 there is a further BAW ladder filter section 30a, which is constructed in t-topology. Since signal guidance on this side of the LC- lattice section 40 is unbalanced there is no need to have this BAW ladder filter section symmetrical.
  • a BAW ladder filter section in ⁇ -topology which comprises two shunt BAW elements and between the two shunt BAW elements one series BAW element, or D -topology, which comprises one series BAW element and one shunt BAW element, may be used.
  • a impedance matching section 50d at the input port 1 comprises in this case a series inductance 54d.
  • Fig. 4 highlights another possible improvement of the resonator filter structure, especially when a very narrow passband is needed.
  • a BAW lattice filter section 20a is shown which is used as resonator filter section of the resonator filter structure 10 of the present invention. It goes without saying that it is clear for the man skilled in the art how the BAW lattice filter structure 20a of Fig. 4 can be incorporated in the resonator filter structure according to the present invention as illustrated by example of Fig. 1 and 2.
  • Fig. 4 shows a BAW lattice filter section 20a which is used as resonator filter section of the resonator filter structure 10 of the present invention.
  • all BAW lattice elements 26a, 26b, 26c, 26d have equal resonance frequency and anti-resonance frequency, which also simplifies the fabrication process by eliminating the step of creating an offset in resonance frequencies between first and second resonator elements. That results all resonators can be made with the same piezo thickness and no massloading is required. Further, the BAW resonator elements 26a, 26b and the BAW resonator elements 26c, 26d differ in area.
  • the parallel capacitances 28a, 28b which are connected in parallel towards the BAW elements 26a, 26b are essential to move the anti- resonance frequencies of those resonators, hi other words, providing the tuning capacitances 28a and 28b for adjusting the filter passband can ease the manufacture of the BAW lattice filter section. It has found by the inventors that for good stopband rejection capacitances of each lattice arm need to be equal.
  • horizontal, i.e. series, arms and diagonal, i.e. lattice, arms maybe exchanged.
  • a resonator filter structure applicable for communication devices, for instance, handheld GPS or personal communication units.
  • a resonator filter structure comprising at least one filter circuit with resonator elements that are preferably BAW resonator elements.
  • This at least one resonator filter circuit is combined with at least one LC-lattice section in which inductance and capacitance elements are arranged for balance improvement of the resonator filter structure.
  • the complete resonator filter according to a preferred embodiment of the invention provides improved output amplitude and phase balance in a frequency band which is large enough for communication standards like PCS.
  • implementation in unbalanced-in to balanced-out applications is possible.
  • the present invention is not restricted to the embodiments of the present invention, in particular the invention is not restricted to receive filters which have been used in this specification for reason of example.
  • the principle of the present invention can be applied to any application that needs in a high frequency environment a filter that provides narrow bandwidth and high stopband rejection together with good phase and amplitude balance within the passband.

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  • Acoustics & Sound (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

La présente invention concerne une structure de filtre de résonateur (10) applicable pour des dispositifs de communication, par exemple un GPS portable ou des unités de communication personnelles. Cette structure de filtre de résonateur (10) est fondée sur au moins un circuit de filtre de résonateur (20, 30) comprenant des éléments résonateur qui sont de préférence des éléments résonateur BAW. Ce ou ces circuits de filtre de résonateur (20, 30) sont combinés avec au moins une partie réseau LC (40) dans lequel des éléments d'inductance (44a, 44b) et des éléments de capacitance (42a, 42b) sont agencés de façon à améliorer l'équilibrage de la structure de filtre de résonateur (10). La structure de filtre de résonateur (10) complète d'un mode préféré de réalisation de l'invention fournit une amplitude de sortie et un équilibrage de phase dans une bande de fréquence qui est assez large pour des normes de communication de type PCS. De plus, en fonction du guidage de signal, il est possible de réaliser des applications à entrée dissymétrique et à sortie symétrique.
PCT/IB2003/006226 2003-01-20 2003-12-22 Structure de filtre de resonateur a equilibrage ameliore Ceased WO2004066494A1 (fr)

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AU2003285700A AU2003285700A1 (en) 2003-01-20 2003-12-22 Resonator filter structure with improved balance

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EP03100102.7 2003-01-20
EP03100102 2003-01-20

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WO2004066494A1 true WO2004066494A1 (fr) 2004-08-05

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US20120013419A1 (en) * 2010-07-19 2012-01-19 Jea Shik Shin Radio frequency filter and radio frequency duplexer including bulk acoustic wave resonators
US8963654B2 (en) 2009-08-04 2015-02-24 Samsung Electronics Co., Ltd. Dual input, dual output BAWR filtering apparatus including a ladder-bridge-ladder configuration
KR20150102709A (ko) * 2014-02-28 2015-09-07 아날로그 디바이시즈 글로벌 고속 adc 어플리케이션을 위한 lc 격자 지연 라인
US9294070B2 (en) 2010-08-20 2016-03-22 Epcos Ag Duplexer with balun
US9432045B2 (en) 2013-03-15 2016-08-30 Analog Devices Global Continuous-time oversampling pipeline analog-to-digital converter
US9762221B2 (en) 2015-06-16 2017-09-12 Analog Devices Global RC lattice delay
US10171102B1 (en) 2018-01-09 2019-01-01 Analog Devices Global Unlimited Company Oversampled continuous-time pipeline ADC with voltage-mode summation
CN110165343A (zh) * 2018-02-12 2019-08-23 诺思（天津）微系统有限公司 一种射频滤波器
US11133814B1 (en) 2020-12-03 2021-09-28 Analog Devices International Unlimited Company Continuous-time residue generation analog-to-digital converter arrangements with programmable analog delay
CN118174674A (zh) * 2024-05-13 2024-06-11 之江实验室 滤波器芯片及电子设备

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8963654B2 (en) 2009-08-04 2015-02-24 Samsung Electronics Co., Ltd. Dual input, dual output BAWR filtering apparatus including a ladder-bridge-ladder configuration
US8902021B2 (en) * 2010-07-19 2014-12-02 Samsung Electronics Co., Ltd. Radio frequency filter and radio frequency duplexer including bulk acoustic wave resonators in a ladder and a bridge
US20120013419A1 (en) * 2010-07-19 2012-01-19 Jea Shik Shin Radio frequency filter and radio frequency duplexer including bulk acoustic wave resonators
US9294070B2 (en) 2010-08-20 2016-03-22 Epcos Ag Duplexer with balun
US9432045B2 (en) 2013-03-15 2016-08-30 Analog Devices Global Continuous-time oversampling pipeline analog-to-digital converter
US9774344B2 (en) 2013-03-15 2017-09-26 Analog Devices Global Continuous-time analog-to-digital converter
KR20150102709A (ko) * 2014-02-28 2015-09-07 아날로그 디바이시즈 글로벌 고속 adc 어플리케이션을 위한 lc 격자 지연 라인
KR101647252B1 (ko) * 2014-02-28 2016-08-09 아날로그 디바이시즈 글로벌 고속 adc 어플리케이션을 위한 lc 격자 지연 라인
US9312840B2 (en) 2014-02-28 2016-04-12 Analog Devices Global LC lattice delay line for high-speed ADC applications
US9762221B2 (en) 2015-06-16 2017-09-12 Analog Devices Global RC lattice delay
US10171102B1 (en) 2018-01-09 2019-01-01 Analog Devices Global Unlimited Company Oversampled continuous-time pipeline ADC with voltage-mode summation
CN110165343A (zh) * 2018-02-12 2019-08-23 诺思（天津）微系统有限公司 一种射频滤波器
US11133814B1 (en) 2020-12-03 2021-09-28 Analog Devices International Unlimited Company Continuous-time residue generation analog-to-digital converter arrangements with programmable analog delay
CN118174674A (zh) * 2024-05-13 2024-06-11 之江实验室 滤波器芯片及电子设备

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