Abstract
A resonator circuit, a filter with improved tunability, and a duplexer with improved tunability are disclosed. In an embodiment, the resonator circuit includes a resonator, a Z transformer and an impedance circuit, wherein the impedance circuit has an impedance Z and includes an impedance element, wherein the Z transformer is interconnected between the resonator and the impedance circuit, and wherein the Z transformer transforms the impedance Z to a new impedance ZZ and comprises a transformation circuit selected from: a generalized impedance converter (GIC), an negative impedance converter (NIC), a generalized impedance inverter (GII) and an negative impedance inverter (NII).
Claims
1. A resonator circuit comprising: a resonator; an impedance transformer; and an impedance circuit configured to adjust a frequency spacing between a pole and a resonant frequency of the resonator circuit, wherein the impedance circuit has a first impedance and includes an impedance element, wherein the impedance transformer is interconnected between the resonator and the impedance circuit, and wherein the impedance transformer is configured to transform the first impedance to a second impedance different from the first impedance and comprises a transformation circuit selected from: a generalized impedance converter (GIC), an negative impedance converter (NIC), a generalized impedance inverter (GII) and a negative impedance inverter (NII).
2. The resonator circuit according to claim 1, wherein the resonator comprises at least one of a surface acoustic wave (SAW) resonator, a bulk acoustic wave (BAW) resonator, a microelectromechanical system (MEMS) resonator, or an LC resonant circuit.
3. The resonator circuit according to claim 1, wherein the transformation circuit is the NIC and comprises two cross-connected transistors.
4. The resonator circuit according to claim 1, wherein the impedance element is tunable.
5. The resonator circuit according to claim 1, wherein the impedance element is a capacitive element.
6. The resonator circuit according to claim 1, wherein the impedance element comprises a digitally tunable capacitor (DTC), a varactor, or a barium-strontium-titanate (BST)-based element.
7. The resonator circuit according to claim 1, wherein the resonator, the impedance transformer and the impedance circuit are arranged on a common carrier.
8. The resonator circuit according to claim 1, wherein at least one of the impedance transformer or the impedance circuit is manufactured using CMOS technology or using a technology based on GaAs or SiGe.
9. The resonator circuit according to claim 1, wherein: at least one of the impedance transformer or the impedance circuit is formed in a semiconductor substrate, the resonator is formed in or on a resonator substrate, and the resonator substrate and the semiconductor substrate are stacked.
10. A radio frequency (RF) filter comprising: one or more resonator circuits according to claim 1.
11. The RF filter according to claim 10, wherein the one or more resonator circuits are interconnected either exclusively in a signal path or exclusively in one or more shunt paths which interconnect the signal path with ground.
12. A duplexer comprising: the RF filter according to claim 10.
13. The duplexer according to claim 12, wherein the duplexer comprises a tunable impedance element as the impedance element such that the duplexer is tunable in terms of its frequency properties.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Important aspects and principles of the resonator circuit are explained in greater detail below with reference to schematic figures.
(2) In the figures:
(3) FIG. 1 shows a schematic illustration of the resonator circuit RS,
(4) FIG. 2 shows one embodiment of a resonator circuit,
(5) FIG. 3 shows a further embodiment of the resonator circuit,
(6) FIG. 4 shows a further embodiment of the resonator circuit,
(7) FIG. 5 shows a further configurational form of the resonator circuit,
(8) FIG. 6 shows the equivalent circuit diagram of a resonator R operating with acoustic waves,
(9) FIG. 7 shows various possibilities for the impedance element in the impedance circuit,
(10) FIG. 8 shows an extension of the resonator circuit in order to obtain additional degrees of freedom,
(11) FIG. 9 shows one embodiment of an NIC,
(12) FIG. 10 shows one possible arrangement of the circuit components on a carrier substrate TSU,
(13) FIG. 11 shows a further possibility of the arrangement with a higher degree of integration,
(14) FIG. 12 shows a cross section through a component which represents a further possibility for the arrangement with a higher degree of integration,
(15) FIG. 13 shows a perspective view of a component in which circuit component parts are arranged on a carrier substrate TSU and interconnected by means of bonding wire,
(16) FIG. 14 shows a further embodiment with provision of an interconnection by means of bump connection BU,
(17) FIG. 15 shows admittance curves of an exemplary resonator circuit,
(18) FIG. 16 shows admittance curves of an alternative embodiment of a resonator circuit.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
(19) FIG. 1 schematically illustrates the relationship of the individual circuit component parts of the resonator circuit RS. The resonator circuit RS comprises a resonator R, a Z transformer ZT and an impedance circuit IS. The impedance circuit has an impedance Z and comprises an impedance element IE. The impedance element IE can determine the impedance Z of the impedance circuit IS by itself or in interaction with further circuit component parts of the impedance circuit IS. The Z transformer ZT is interconnected between the resonator R and the impedance circuit IS. As a result, it is possible for the Z transformer ZT to mask the impedance Z of the impedance circuit IS and to cause it to appear as an alternative impedance Z toward the outside, i.e., toward the resonator. Depending on the choice of the matrix elements of the chain matrix of the Z transformer, the original impedance Z of the impedance circuit IS can appear as practically any arbitrary impedance Z. In particular capacitances having a negative capacity are possible. The coupling of the resonator R with a fundamentally arbitrarily transformed impedance Z enables degrees of freedom which, by means of conventional impedance circuits IS, do not become accessible at all or become accessible at most with a high outlay on circuitry.
(20) Since the combination of the three circuit component parts of the resonator circuit IS has a multiplicity of electrical terminals, it is possible in a diverse manner to connect precisely this resonator circuit to an external circuit environment, e.g., a bandpass circuit.
(21) FIG. 2 shows an embodiment of the resonator circuit in which the Z transformer ZT is embodied as a two-port network interconnected with the resonator R by one port and with an impedance element IE of the impedance circuit IS by the other port. In this case, the resonator circuit RS has a first terminal A1 and a second terminal A2, via which it can be interconnected with an external circuit environment.
(22) FIG. 2 illustrates here a parallel interconnection of the resonator R with the new impedance Z that results from the use of the Z transformer ZT between the resonator R and the impedance element IE.
(23) FIG. 3 shows an embodiment of the resonator circuit in which the terminals of the resonator circuit are assigned to the port P facing the impedance element IE.
(24) FIG. 4 shows an embodiment of the resonator circuit in which the resonator R and the new impedance Z are connected in series between the terminals for an external circuit environment.
(25) FIG. 5 illustrates a resonator circuit in which the terminals for an external circuit environment are provided directly on the one hand with the impedance element and on the other hand with a terminal of a port of the Z transformer that faces the impedance element.
(26) FIG. 6 illustrates the equivalent circuit diagram of a resonator R operating with acoustic waves. A series interconnection of an inductance L.sub.1 and a first capacitance C.sub.1 is interconnected in parallel with a capacitive element of the capacitance C.sub.0. In this case, the capacitance C.sub.0 influences the position of the pole, but not the position of the resonant frequency of the resonator.
(27) A connection of the resonator R to an impedance element IE via a Z transformer ZT makes it possible, depending on matrix elements of the chain matrix, to have practically any desired influence on the variables L.sub.1, C.sub.1 and C.sub.0.
(28) FIG. 7 shows various embodiments of the impedance element IE in the impedance circuit IS. The impedance element can be a capacitive element KE (shown at top left), a tunable capacitive element AKE (shown at top right), an inductive element INE (shown at bottom left), a tunable inductive element AINE (shown at bottom right), or generally an inductive element IE (middle, left) or a tunable inductive element AIE (middle, right). Interconnections of different tunable or non-tunable impedance elements in the impedance circuit IS are likewise possible.
(29) The impedance element can itself have a circuit composed of elementary circuit units such as active or passive units.
(30) FIG. 8 shows the possibility of further manipulating the resonator circuit RS or the frequency-dependent impedance behavior thereof by an interconnection with further circuit component parts, in order to obtain even more degrees of freedom. In this regard, the resonator circuit RS can be interconnected in series with a third impedance element IE3. A second impedance element IE2 can be coupled to the third impedance element IE3 via a further Z transformer, such that the impedance of the second impedance element is also settable practically arbitrarily toward the outside. The circuit interconnected with the resonator circuit RS thus constitutes a further impedance circuit IS2. A serial interconnection of the further impedance circuit IS2 and the resonator circuit RS is thus made available via the terminals for an external circuit environment.
(31) Generally, each resonator circuit RS in FIG. 1, 2, 3, 4 or 5 can also be interconnected with each resonator circuit RS in FIG. 1, 2, 3, 4 or 5 in this way.
(32) FIG. 9 shows one possible embodiment of a GIC, specifically of an NIC, which embodiment is very simple, however, for the sake of clarity: an impedance element of the impedance Z.sub.L is interconnected with the input port of the NIC via two cross-connected transistors and appears as impedance Z.sub.IN. The emitter of the upper transistor T1 is interconnected with one terminal of the port. The emitter of the lower transistor T2 is interconnected with the second terminal of the port. The base of the first transistor T1 is interconnected with the lower terminal of the impedance element. The base of the second transistor T2 is interconnected with the upper terminal of the impedance element. Since the base of the first transistor T1 is additionally interconnected with the collector of the second transistor and the base of the second transistor is interconnected with the collector of the first transistor, a crosswise interconnection is obtained.
(33) Applying Kirchhoff s lawsconsidered in suitable conductor loops for voltages and at suitable circuit nodes for currentsleads to the result that the voltages present at the impedance element, on the one hand, and at the input port of the NIC, on the other hand, are identical in terms of absolute value, but of different polarities if both transistors are of the same design. If a sinusoidal RF signal is applied to the circuit in FIG. 9, then this results in a phase shift of 180 degrees between the input of the circuit and the load. However, the current flow is identical in this case. Z.sub.IN=Z.sub.L thus ensues from equation 2. Therefore, an NIC having a proportionality factor=1 is actually present, which transforms an arbitrary load impedance Z.sub.L into the negative impedance Z=Z.sub.L.
(34) The behavior of the Z transformer is determined by the matrix entries A, B, C, D. At first glance it appears to be difficult to find a corresponding circuit which realizes the matrix for selected values for A, B, C and D. However, the advantage of matrix notation is manifested here: two series-connected two-port networks are described by a common matrix that results as the product of the two individual matrices of the two individual two-port networks. A technical solution for the chain matrix has therefore already been found if technical solutions are found for a multiplicity of two-port networks whose matrix product yields the desired chain matrix. The problem can thus easily be found by decomposing into partial problems and solving these partial problems independently of one another.
(35) For reasons of stability, it may be advantageous to use a plurality of transistors.
(36) NICs realized with transistors are known, e.g., from the paper Transistor Negative-Impedance Converters by J. G. Linvill; Proceedings I; R; E June 1953, pp. 725-729.
(37) FIG. 10 shows one possible arrangement of the circuit component parts on a carrier substrate TSU. The resonator R, the Z transformer ZT and the impedance element, e.g., a tunable impedance element AIE, can be arranged alongside one another on the carrier substrate TSU. Interconnections are possible via metallization on the surface of the carrier substrate TSU or in interlayers of a carrier substrate embodied in a multilayered fashion.
(38) FIG. 11 shows a further degree of integration in which the tunable impedance element AIE and the circuit elements of the Z transformer ZT are integrated together, e.g., in a semiconductor chip.
(39) FIG. 12 shows a cross section through a component in which a component part comprising the tunable impedance element AIE and the Z transformer is arranged on a carrier substrate. The interconnection therebetween can be produced by means of bumps.
(40) A component part comprising the resonator is arranged on the component part comprising the tunable impedance element and the Z transformer. The interconnection of these component pails can also be effected by means of bumps. An interconnection via TSVs (TSV=Thru-Silicon Via) is likewise possible.
(41) FIG. 13 shows such a possibility in a perspective view, wherein signal lines as structured metallizations are arranged on the surface of the carrier substrate TSU. Terminals of the resonator R are connected to the metallizations of the signal line SL by bond wires BD.
(42) FIG. 14 shows an alternative or additional embodiment, in which the resonator R is interconnected with the metallizations of the signal line by means of bump connections BU.
(43) FIG. 15 shows frequency-dependent admittance curves Y for a resonator circuit in which the impedance element is embodied as a tunable impedance element. In this case, the tunable impedance element is interconnected with a conventional SAW resonator via an NIC (see, e.g., FIG. 2). Tuning the impedance Z of the impedance element, i.e., varying the impedance Z of the impedance element, does not vary the resonant frequency, which is approximately 880 MHz. The two curves shown in FIG. 15 result depending on the value of the impedance of the tunable impedance element. The pole is at approximately 880 MHz in one case, and at approximately 895 MHz in the other case. That corresponds to an increase in the pole-zero spacing from 30 MHz to 45 MHz and enables an increase in the (relative) bandwidth by 50 percent.
(44) FIG. 16 shows frequency-dependent admittance curves of a resonator circuit in which the impedance element in the sense of FIG. 3 is directly connected to the terminals of the resonator circuit and the NIC masks the impedance of the resonator R. Here, too, a readily variable antiresonance is settable. The quality factor of the antiresonance is still relatively good.
(45) By contrast, the quality factor of the resonance is detrimentally affected. However, better quality factors can be improved by correspondingly carefully selected circuit component parts.
(46) Further resonator circuits comprising additional resonators, transformers and impedance elements and corresponding filter circuits and duplexers are possible besides the above-described circuits and exemplary embodiments shown in the figures.
