Reconfigurable filter in multiplexer

Abstract

The invention relates to a reconfigurable filter in a multiplexer. A filter apparatus for multi-band wireless communication includes a first circuit characterized by a first passband from a first frequency to a second frequency; a second circuit characterized by a second passband from a frequency not less than the first frequency to a third frequency, the third frequency not higher than the second frequency but higher than the first frequency; a third circuit characterized by a third passband from a fourth frequency to a frequency not greater than the second frequency, the fourth frequency being not less than the first frequency but less than the second frequency; and a switch configured to connect the first circuit to the second circuit to reconfigure a first filter with the second passband or to connect the first circuit to the third circuit to reconfigure a second filter with the third passband.

Description

Technical Field

[0001] The present technology relates to devices in wireless communications. Background Art

[0002] In multi-mode and multi-band wireless communication systems, filters play many roles within the multiplexer structure to ensure that signals across different frequency bands are isolated from each other and are properly directed. These filters help separate, combine or route different frequency bands to appropriate paths, thereby facilitating seamless operation between various communication standards (e.g., LTE, 5G, Wi-Fi, etc.) and across a variety of frequency bands (e.g., 2.4GHz, 5GHz, etc.). Multiplexers can be made to support various frequency bands simultaneously. For example, a smartphone may need to operate across multiple LTE bands, Wi-Fi bands, and possibly other dedicated communication bands. In such cases, the multiplexer contains an array of filters, each of which is tuned to a specific frequency band that the device needs to support. Typically, each filter that transmits or receives a desired signal and blocks an undesired signal is designed to support only one frequency band. Since each frequency band requires its corresponding filter, the number of filters required for the multiplexer is very large and the matching network components required for matching between the filter and the RFIC make the module very complex. Increase the module size to support as many frequency bands as needed. Therefore, there is a need for an improved filter device that can inherently support multiple frequency bands so that the number of filters required in multiplexer modules and associated matching networks can be reduced. Summary of the invention

[0003] In one aspect, the present disclosure relates to a filter device for multi-band wireless communication, comprising: a first circuit, which is characterized by a first passband from a first frequency to a second frequency, the second frequency being greater than the first frequency; a second circuit, which is characterized by a second passband from a frequency not less than the first frequency to a third frequency, the third frequency being not higher than the second frequency but higher than the first frequency; a third circuit, which is characterized by a third passband from a fourth frequency to a frequency not greater than the second frequency, the fourth frequency being not less than the first frequency but less than the second frequency; and a switch, which is configured to connect the first circuit to the second circuit to reconfigure the first filter with the second passband, or to connect the first circuit to the third circuit to reconfigure the second filter with the third passband, wherein at least one of the second passband and the third passband is narrower than the first passband.

[0004] In another aspect, the present disclosure relates to a reconfigurable filter device, comprising: a first circuit characterized by a first passband from a first frequency to a second frequency, the second frequency being higher than the first frequency; a second circuit characterized by a second passband from a frequency not less than the first frequency to a third frequency, the third frequency being not higher than the second frequency but higher than the first frequency; a third circuit characterized by a third passband from a fourth frequency to a frequency not greater than the second frequency, the fourth frequency being not lower than the first frequency but lower than the second frequency; a switch comprising an input port coupled to the first circuit, a first output port coupled to the second circuit, and a first output port coupled to the a second output port of the third circuit, the switch being configured to receive at the input port a first signal filtered by the first circuit with the first passband and deliver the first signal to the first output port for reconfiguring a second signal filtered by the second circuit with the second passband, or to deliver the first signal directly to the second output port for reconfiguring a third signal filtered by the third circuit with the third passband; and a fourth circuit coupled to the switch in parallel between the first circuit and the second circuit or the third circuit and configured to implement a rejection band for the second signal or the third signal.

[0005] In yet another aspect, the present disclosure relates to a reconfigurable filter device comprising: a circuit comprising a first plurality of resonators in a series and shunt circuit system characterized by a first passband from a first frequency to a second frequency, a second plurality of resonators in a series and shunt circuit system characterized by a second passband from a frequency not less than the first frequency to a third frequency, a third plurality of resonators in a series and shunt circuit system characterized by a third passband from a fourth frequency to a frequency not greater than the second frequency, and a capacitor coupled between the first plurality of resonators and the second plurality of resonators, the third frequency being lower than the second frequency but higher than the first frequency, and the fourth frequency being higher than the first frequency but lower than the second frequency; and a switch configured to couple to the circuit to connect the first plurality of resonators to the second plurality of resonators to reconfigure the first filter with the second passband and a deeper rejection band, or to connect the first plurality of resonators to the third plurality of resonators to reconfigure the second filter with the third passband and a deeper rejection band. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] A further understanding of the nature and advantages of particular embodiments may be achieved by reference to the remainder of the specification and drawings, wherein like reference numerals are used to refer to similar components. In some instances, a sub-label is associated with a reference numeral to represent one of multiple similar components. When a reference numeral is cited without elaborating on the existing sub-label, the reference numeral is intended to refer to all such multiple similar components.

[0007] Figure 1 is a simplified block diagram of a conventional multiplexer structure for supporting multi-mode and multi-band wireless communication systems.

[0008] Figure 2 is a simplified circuit diagram of a conventional filter device for a wireless communication system.

[0009] Figure 3 is a simplified circuit diagram of a reconfigurable filter for a wireless communication system in accordance with an embodiment of the present technology.

[0010] Figure 4 is a schematic diagram of the spectral characteristics of a reconfigurable filter according to an embodiment of the present technology.

[0011] Figure 5 is a simplified circuit diagram of a reconfigurable filter for a wireless communication system according to another embodiment of the present technology.

[0012] Figure 6 is a simplified graph showing the anti-resonant frequency tuned by added circuitry according to an embodiment of the present technology.

[0013] Figure 7 is a simplified circuit diagram of a reconfigurable filter for a wireless communication system according to another embodiment of the present technology. DETAILED DESCRIPTION

[0014] The present technology provides a filter device for multi-band wireless communication. In an embodiment, the device includes a first circuit characterized by a first passband from a first frequency to a second frequency. The device also includes a second circuit characterized by a second passband from the first frequency to a third frequency. The device also includes a third circuit characterized by a third passband from a fourth frequency to the second frequency. The device also includes a switch configured to connect the first circuit to the second circuit to reconfigure the filter with the second passband, or to connect the first circuit to the third circuit to reconfigure another filter with the third passband. Other embodiments also exist.

[0015] The following description is presented to enable one skilled in the art to make and use the invention and to incorporate the invention into the context of a particular application. Various modifications and various uses in different applications will be readily apparent to one skilled in the art, and the general principles defined herein may be applied to a wide range of embodiments. Therefore, it is not intended to limit the invention to the embodiments presented, but rather to give the invention the widest scope consistent with the principles and novel features disclosed herein.

[0016] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without being limited to these specific details. In other examples, well-known structures and devices are shown in block diagram form rather than in detail in order to avoid obscuring the present invention.

[0017] The reader is advised to pay attention to all papers and documents which are filed concurrently with this specification and are available for public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. Unless expressly stated otherwise, all features disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose. Therefore, unless expressly stated otherwise, each disclosed feature is only one example of a series of generic equivalent or similar features.

[0018] In addition, any element in the technical solution that does not explicitly state a "means" for performing a specified function or a "step" for performing a specified function should not be interpreted as a "means" or "step" clause as provided in 35 U.S.C. Section 112, paragraph 6. In particular, the use of "step" or "action" in the claims herein is not intended to refer to the provisions of 35 U.S.C. Section 112, paragraph 6.

[0019] When an element is referred to herein as being "connected" or "coupled" to another element, it is understood that the element may be directly connected to the other element, or that there may be intervening elements between the elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, it is understood that there are no intervening elements in the "direct" connection between the elements. However, the presence of a direct connection does not exclude other connections in which there may be intervening elements.

[0020] When an element is referred to herein as being "disposed" in some manner relative to another element (e.g., disposed on, between, below, near, or in some other relative manner), it is understood that the element may be disposed directly relative to the other element (e.g., disposed directly on the other element) or that there may be intervening elements between the elements. In contrast, when an element is referred to as being "directly disposed" relative to another element, it is understood that there are no intervening elements in the "direct" instance. However, the presence of a direct disposition does not exclude other instances in which there may be intervening elements.

[0021] Similarly, when an element is referred to herein as being "joined" to another element, it is understood that the element may be directly joined to the other element (without any intervening elements) or with intervening elements between the joined elements. In contrast, when an element is referred to as being "directly joined" to another element, it is understood that there are no intervening elements in the "direct" joining between the elements. However, the presence of direct joining does not exclude other forms of joining in which there may be intervening elements.

[0022] Likewise, when an element is referred to herein as a "layer," it is understood that the layer may be a single layer or may include multiple layers. For example, a conductive layer may include a plurality of different conductive materials or multiple layers of different conductive materials, and a dielectric layer may include a plurality of dielectric materials or multiple layers of dielectric materials. When a layer is described as being coupled or connected to another layer, it is understood that the coupled or connected layer may include intervening elements present between the coupled or connected layers. In contrast, when a layer is referred to as being "directly" connected or coupled to another layer, it is understood that there are no intervening elements between the layers. However, the presence of directly coupled or connected layers does not exclude other connections in which intervening elements may be present.

[0023] In addition, the terms left, right, front, back, top, bottom, forward, reverse, clockwise and counterclockwise are used for explanation purposes only and are not limited to any fixed direction or orientation. Instead, the terms are only used to indicate the relative position and / or direction between the various parts of an object and / or component.

[0024] In addition, for ease of description, the methods and processes described herein may be described in a specific order. However, it should be understood that unless the context otherwise requires, the intervening process may occur before and / or after any portion of the described process, and other various procedures may be reordered, added, and / or omitted according to various embodiments.

[0025] Unless otherwise indicated, all numbers used herein to express quantities, sizes, etc. should be understood to be modified by the term "about" in all cases. In this application, unless otherwise specifically stated, the use of the singular includes the plural, and unless otherwise indicated, the use of the terms "and" and "or" means "and / or". In addition, the use of the terms "including" and "having" and other forms such as "includes", "included", "has", "have" and "had" should be considered non-exclusive. Moreover, unless otherwise specifically stated, terms such as "element" or "component" include both elements and components including one unit and elements and components including more than one unit.

[0026] As used herein, the phrase "at least one of..." following a series of items, with the terms "and" or "or" separating any of the items, modifies the entire list, rather than each member of the list (i.e., each item). The phrase "at least one of..." does not require selection of at least one of each of the listed items; rather, the phrase allows for a meaning that includes at least one of any of the items and / or at least one of any combination of the items. By way of example, the phrase "at least one of A, B, and C" or "at least one of A, B, or C" each refers to only A, only B, or only C; and / or any combination of A, B, and C. In instances where "at least one of each of A, B, and C" or, alternatively, "at least one of A, at least one of B, and at least one of C" is intended to be selected, it is expressly described as such.

[0027] One general aspect of the present technology includes a filter device for multi-band wireless communication. The filter device also includes a first circuit, the first circuit being characterized by a first passband from a first frequency to a second frequency, the second frequency being greater than the first frequency. The device also includes a second circuit, the second circuit being characterized by a second passband from a frequency not less than the first frequency to a third frequency, the third frequency being not higher than the second frequency but higher than the first frequency. The device also includes a third circuit, the third circuit being characterized by a third passband from a fourth frequency to a frequency not greater than the second frequency, the fourth frequency being not less than the first frequency but less than the second frequency. The device also includes a switch, the switch being configured to connect the first circuit to the second circuit to reconfigure the first filter with the second passband, or to connect the first circuit to the third circuit to reconfigure the second filter with the third passband, wherein at least one of the second passband and the third passband is narrower than the first passband.

[0028] Implementations may include one or more of the following features. The device, wherein the first circuit may include a first rejection band below a fifth frequency and a second rejection band above a sixth frequency, the fifth frequency being less than the first frequency and the sixth frequency being higher than the second frequency. The first filter may include a third rejection band below a seventh frequency and a fourth rejection band above an eighth frequency, the seventh frequency being aligned with the fifth frequency and the eighth frequency being greater than the third frequency but less than the sixth frequency. The first circuit may include a plurality of first resonators coupled in series in a transmission line and a plurality of second resonators coupled in parallel with the transmission line, each first resonator being characterized by a respective anti-resonance frequency associated with the sixth frequency and each second resonator being characterized by a respective resonant frequency associated with the fifth frequency. Each of the first resonator and the second resonator may include a film bulk acoustic resonator (FBAR). The second circuit may include a plurality of third resonators coupled in series in a transmission line and a plurality of fourth resonators coupled in parallel with the transmission line, each third resonator characterized by a respective anti-resonance frequency associated with an eighth frequency, each fourth resonator characterized by a respective resonant frequency associated with a seventh frequency, and each of the third and fourth resonators may include a film bulk acoustic resonator (FBAR). For frequencies less than the seventh frequency, the third rejection band may include at least 40 dB of loss due to the aggregation of each peak impedance contribution from each fourth resonator and the second resonator at a respective resonant frequency in which the seventh frequency is aligned with the fifth frequency. For frequencies greater than the eighth frequency, the fourth rejection band may include at least 40 dB of loss due to the aggregation of each peak impedance contribution from each third resonator and the first resonator at a respective anti-resonance frequency. The first filter may include a fourth passband from an eleventh frequency to a twelfth frequency, a seventh rejection band below a thirteenth frequency, and an eighth rejection band above a fourteenth frequency, the eleventh frequency being higher than the first frequency, the twelfth frequency being lower than the second frequency, the thirteenth frequency being higher than the fifth frequency but the seventh rejection band has a deeper rejection than the first rejection band, and the fourteenth frequency being lower than the sixth frequency but the eighth rejection band has a deeper rejection than the second rejection band. The second filter may include a fifth rejection band below a ninth frequency and a sixth rejection band above a tenth frequency, the ninth frequency being lower than the fourth frequency but higher than the fifth frequency, the tenth frequency being aligned with the sixth frequency. The third circuit may include a plurality of fifth resonators coupled in series in a transmission line and a plurality of sixth resonators coupled in parallel with the transmission line, each fifth resonator being characterized by a respective anti-resonance frequency associated with the tenth frequency, each sixth resonator being characterized by a respective resonant frequency associated with the ninth frequency, and each of the fifth resonator and the sixth resonator may include a film bulk acoustic resonator (FBAR). For frequencies less than the ninth frequency, the fifth rejection band may include a loss of at least 40 dB due to the aggregation of each peak impedance contribution from each sixth resonator and the second resonator at the respective resonant frequency.For frequencies greater than the tenth frequency, the sixth rejection band may include at least 40 dB of loss due to the aggregation of each peak impedance contribution of each fifth resonator and the first resonator at a respective anti-resonant frequency where the tenth frequency is aligned with the sixth frequency.

[0029] Another general aspect of the present technology includes a reconfigurable filter device for a multi-mode and multi-band wireless communication system. The reconfigurable filter device also includes a first circuit, the first circuit being characterized by a first passband from a first frequency to a second frequency, the second frequency being higher than the first frequency. The device also includes a second circuit, the second circuit being characterized by a second passband from a frequency not less than the first frequency to a third frequency, the third frequency being not higher than the second frequency but higher than the first frequency. The device also includes a third circuit, the third circuit being characterized by a third passband from a fourth frequency to a frequency not greater than the second frequency, the fourth frequency being not lower than the first frequency but lower than the second frequency. The device also includes a switch, the switch may include an input port coupled to the first circuit, a first output port coupled to the second circuit, and a second output port coupled to the third circuit, the switch being configured to receive a first signal filtered by the first circuit with the first passband at the input port and deliver the first signal to the first output port for reconfiguring a second signal filtered by the second circuit with the second passband, or to deliver the first signal directly to the second output port for reconfiguring a third signal filtered by the third circuit with the third passband. The device also includes a fourth circuit coupled in parallel to the switch between the first circuit and the second circuit or the third circuit and configured to implement a rejection band for the second signal or the third signal.

[0030] An implementation may include one or more of the following features. The device, wherein the first circuit may include a plurality of first resonators coupled in series in a transmission line and a plurality of second resonators coupled in parallel with the transmission line, the plurality of second resonators generating a first rejection band below a fifth frequency, the plurality of first resonators generating a second rejection band above a sixth frequency, the fifth frequency being lower than the first frequency, and the sixth frequency being higher than the second frequency. The second circuit may include a plurality of third resonators coupled in series in the transmission line and a plurality of fourth resonators coupled in parallel with the transmission line, the second circuit in combination with the first circuit generating a first filter having a second passband, the plurality of fourth resonators and the plurality of second resonators providing a third rejection band to the first filter, the third rejection band having a higher loss than the first rejection band below a seventh frequency, the plurality of third resonators and the plurality of first resonators providing a fourth rejection band to the first filter, the fourth rejection band having a higher loss than the second rejection band above an eighth frequency, the seventh frequency being aligned with the fifth frequency, and the eighth frequency being higher than the third frequency. The third circuit may include a plurality of fifth resonators coupled in series in the transmission line and a plurality of sixth resonators coupled in parallel with the transmission line, the third circuit in combination with the first circuit produces a second filter having a third passband, the plurality of sixth resonators and the plurality of second resonators provide a fifth rejection band to the second filter, the fifth rejection band having a higher loss than the first rejection band below a ninth frequency, the plurality of fifth resonators and the plurality of first resonators provide a sixth rejection band to the second filter, the sixth rejection band having a higher loss than the second rejection band above a tenth frequency, the ninth frequency being lower than the fourth frequency, the tenth frequency being aligned with the sixth frequency. The fourth circuit may include a capacitor or an inductor or a resonator configured to reconfigure the first filter or the second filter to have increased rejection loss by shifting the anti-resonance frequency of one of the first resonators in the first circuit. Alternatively, the first filter is characterized by a fourth passband configured to be narrower than the first passband and within the first passband, a seventh rejection band below an eleventh frequency higher than the fifth frequency, and an eighth rejection band above a twelfth frequency lower than the sixth frequency, the seventh rejection band having deeper rejection than the first rejection band, and the eighth rejection band having deeper rejection than the second rejection band.

[0031] Another general aspect of the present technology includes a reconfigurable filter device. The reconfigurable filter device also includes a circuit that may include a first plurality of resonators in a series and shunt circuit system characterized by a first passband from a first frequency to a second frequency, a second plurality of resonators in a series and shunt circuit system characterized by a second passband from a frequency not less than the first frequency to a third frequency, a third plurality of resonators in a series and shunt circuit system characterized by a third passband from a fourth frequency to a frequency not greater than the second frequency, and a capacitor coupled between the first plurality of resonators and the second plurality of resonators, the third frequency being lower than the second frequency but higher than the first frequency, and the fourth frequency being higher than the first frequency but lower than the second frequency. The device also includes a switch configured to couple to the circuit to connect the first plurality of resonators to the second plurality of resonators to reconfigure the first filter with the second passband and a deeper rejection band, or to connect the first plurality of resonators to the third plurality of resonators to reconfigure the second filter with the third passband and a deeper rejection band.

[0032] Figure 1 It is a simplified block diagram of a conventional multiplexer structure for supporting a multi-mode and multi-band wireless communication system. In a multi-mode and multi-band wireless communication system, the multiplexer structure includes an antenna switching module (ASW) to support a wireless device connected to a multi-band network by combining individual transmission and reception paths of individual bands transmitted by one or more antennas of Long Term Evolution (LTE), Code Division Multiple Access (CDMA), Universal Mobile Telecommunications Service (UMTS), Enhanced Data Rate for GSM Evolution (EDGE) and Global System for Mobile Communications (GSM). In particular, the ASW allows multi-band operations to share one antenna. These modules can be used for both transmission and reception of RF signals. Using the Rx path as an example, a matching network (MN) is first placed, the impedance of which is appropriately matched to the input impedance of the signal associated with a specific communication (e.g., LTE) to maximize power transfer and reduce possible signal power loss. The multiplexer filter F allows multiple bands to be handled simultaneously. The multiplexer filter performs the function of filtering out unwanted frequencies while allowing the desired band to pass. Each of these filters handles a specific operating bandwidth. For example, the filter F 11 It has a passband from 2300MHz to 2400MHz and a rejection band from 2427MHz to 2482MHz. 12There may be another passband from 2300MHz to 2370MHz, and a rejection band from 2402MHz to 2482MHz. After passing through these filters, each signal output from the filter requires another matching network (MN) to ensure that the signal is received with minimal loss. Finally, a low noise amplifier (LNA) may be required to enhance the signal-to-noise ratio for any further downstream signal processing. A similar configuration is implemented for the Tx path of the multiplexer module, where each band may require a power amplifier (PA) to amplify the signal before it is sent to the antenna for transmission.

[0033] Since each frequency band requires its corresponding filter, the number of filters required for the multiplexer can be very large. An equally large number of matching components are required to match the filters to associated RF components such as (LNA or PA) amplifier devices, making the multiplexer module more complex and increasing the module size to support as many frequency bands as needed. A reconfigurable filter that can reconfigure the frequencies of its passband and rejection band can reduce the number of filters required in the multiplexer module. And the number of matching networks (MNs) can also be reduced, so that the multiplexer module can be simplified and minimized. The present disclosure proposes a reconfigurable filter that can reconfigure its passband and rejection band frequencies to function in multiple frequency bands with a single filter.

[0034] Film bulk acoustic resonator (FBAR) technology has been used to make radio frequency (RF) filters for filtering RF signals in various wireless communication applications. FBAR resonators are typically made of a piezoelectric material sandwiched between two electrodes. When an alternating current is applied, the piezoelectric material resonates at a specific frequency, thereby generating acoustic waves. This resonant behavior can be used to pass or block specific frequencies in the RF spectrum. FBAR filters are particularly suitable for high frequency, low loss, and narrow bandwidth filtering requirements. Figure 2An example of a filter device based on FBAR resonators for a wireless communication system is shown. Optionally, the filter 200 is implemented along a transmission line, which typically has multiple resonators located in a microstrip or coplanar waveguide (CPW) that guides RF signals. For example, resonator 201 is one of multiple resonators coupled in series along the transmission line and resonator 202 is one of multiple resonators coupled in a parallel (shunt) configuration relative to the transmission line. Here, the transmission line is typically a dedicated circuit that facilitates efficient transmission of electrical signals, typically in the form of voltage and current, from one point to another while maintaining signal integrity and minimizing losses. The filter 200 under this complex structure provides advantages in terms of steep roll-off characteristics, low insertion loss, and high selectivity. The series resonator 201 is designed to resonate at a corresponding passband frequency. The resonator effectively "passes" frequencies within the bandwidth of interest (passband) while providing high impedance to unwanted frequencies. The shunt resonator 202 creates a low impedance path to ground the undesired frequencies, thereby attenuating the undesired frequencies (rejection band).

[0035] FBAR filters offer a high quality (Q) factor, which means that they provide a steep roll-off and good filter characteristics. This is well suited for applications that require tight channel separation. Due to the nature of acoustic wave propagation in FBARs, the devices can be much smaller than other filtering technologies, making them suitable for compact portable devices. FBAR filters typically offer low insertion loss, which means that very little signal power is lost when the signal passes through the filter. In addition, FBAR technology can be designed to operate at very high frequencies, typically in the GHz range, making it suitable for a variety of modern wireless applications. Optionally, depending on specific requirements such as frequency range, form factor, power handling, and Q factor, RF filters can be made of other components that can replace FBAR (film bulk acoustic wave resonator) resonators. These alternatives may include surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, ceramic resonators, microelectromechanical systems (MEMS) resonators, LC resonators, crystal resonators, dielectric resonators, coaxial resonators, spiral resonators. However, for Figure 2 In the filter shown in , the passband and rejection band of the filter are fixed and do not need to be reconfigured.

[0036] Figure 33 is a simplified circuit diagram of a reconfigurable filter for a wireless communication system according to an embodiment of the present technology. This diagram is only an example and should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, alternatives and modifications. In an embodiment, the filter device 300 is divided into three circuits: a first circuit 310, a second circuit 320 and a third circuit 330. Each circuit is interconnected by a switch 340. The first circuit 310 is constructed by a plurality of first resonators 313s coupled in series in a transmission line and a plurality of second resonators 313p coupled in parallel with the transmission line. The first resonator 313s is a series resonator coupled in series in a transmission line. The second resonator 313p is a shunt resonator coupled in parallel to the transmission line. Based on the transmission spectrum of these series or shunt resonators around their corresponding characteristic resonant frequencies or anti-resonant frequencies that are properly aligned, the first circuit 310 is configured to form a filter with a common passband and a common rejection band for wireless signals within a specific frequency range.

[0037] Similarly, the second circuit 320 is constructed by a plurality of third resonators 321s coupled in series in a transmission line and a plurality of fourth resonators 321p coupled in parallel with the transmission line. The second circuit 320 may be configured to allow appropriate selection of its respective anti-resonance frequency or resonant frequency, so that the second circuit 320 may form a signal path having a corresponding frequency response, i.e., a filter having a desired passband and rejection band. Alternatively, the third circuit 330 is constructed by a plurality of fifth resonators 331s coupled in series in a transmission line and a plurality of sixth resonators 331p coupled in parallel with the transmission line. The third circuit 330 may be configured to allow appropriate selection of its respective anti-resonance frequency or resonant frequency, so that the third circuit 330 may form an alternative signal path having a corresponding frequency response, i.e., another filter having a desired passband and rejection band different from the filter based on the second circuit 320. In the same context of transmission response around the respective resonant frequency or anti-resonant frequency, the second circuit 320 and the third circuit 330 are configured such that the respective filters can be reconfigured with lower and higher frequency bands, respectively.

[0038] The switch 340 is configured as a single-pole double-throw (SPDT) switch, in which a single input port 341 can be switched to two output ports 342 and 343. The input port 341 is coupled to the first circuit 310. The output port 342 is coupled to the second circuit 320 and the output port 343 is coupled to the third circuit 330. This is a switch for directing a high-frequency signal from one port to the other port among two available ports but not to both ports at the same time. The entire filter device 300 including the SPDT switch can be used in the opposite path, that is, in the receiving path or the transmitting path of the multiplexer module. Using the switch 340, the first circuit 310 is combined with the second circuit 320 to form a first filter or combined with the third circuit 330 to form a second filter, wherein the first circuit 310 acts as a common section and the second circuit 320 and the third circuit 330 act as tuning sections. By appropriately selecting or aligning their respective anti-resonance or resonant frequencies, the first filter and the second filter can be configured as two different filters with different spectral responses in different frequency ranges. For example, a first filter may be configured to operate at a lower frequency range and a second filter may be configured to operate at a higher frequency range.

[0039] In an embodiment, the resonator in the circuit is provided as an FBAR resonator. An FBAR resonator is typically made of a piezoelectric material sandwiched between two electrodes. When an alternating current is applied, the piezoelectric material resonates at a specific frequency, thereby generating an acoustic wave that is used to store or transmit a radio frequency signal in a transmission line associated with multiple resonators in a series and shunt configuration. FBAR filters provide a high quality (Q) factor, which means that they provide a steep roll-off and good filter characteristics. This is very suitable for applications that require strict channel separation. Due to the nature of acoustic wave propagation in FBARs, the device can be much smaller than other filtering technologies, making the device suitable for compact portable devices. FBAR filters also provide many advantages, such as low insertion loss, adaptability to high or extremely high frequencies (in the GHz range), and excellent temperature stability.

[0040] A resonator, or in particular a FBAR resonator, is characterized by a resonant frequency at which it naturally oscillates and stores energy. At the resonant frequency, the impedance of the resonator is at a minimum, which allows for maximum energy storage or transfer. Furthermore, a resonator is characterized by an anti-resonant frequency at which the resonator has maximum impedance and minimum energy storage. At the anti-resonant frequency, the resonator does not allow energy to be efficiently transferred or stored. When the resonators are coupled in a series or shunt configuration, each series resonator is characterized by a resonant frequency f rCharacterized by the fact that at the resonant frequency, the impedance of the resonator is minimum, which allows high transmission of signal power through the transmission line. The spectral response exhibits sharp peaks, resulting in the formation of a passband. The resonator is also related to the anti-resonant frequency f a In association, at the anti-resonant frequency, the impedance is maximum, thereby allowing minimum power transfer. The spectral response will show a dip or drop in power, resulting in the formation of a rejection band. On the other hand, each shunt resonator is connected by another resonant frequency f r 'characterizes that at the other resonant frequency, the impedance is maximum, effectively "blocking" the signal from being shunted from the transmission line or maintaining high power transmission along the transmission line. The spectral response exhibits a peak, which helps the passband. The shunt resonator is also characterized by another anti-resonant frequency f a ' Characterizes that at the other anti-resonance frequency, the impedance minimum is close to zero, resulting in maximum power being shunted from the transmission line. The spectral response will give a trough or dip in power, resulting in a rejection band. When multiple series and shunt resonators are coupled (as in the first circuit 310, where the resonant and anti-resonant frequencies of the resonators are properly aligned), the respective spectral responses are aggregated to provide a desired passband with a particular bandwidth, a first rejection band below the first rejection frequency at a relatively lower frequency range below the passband range, and a second rejection band above the second rejection frequency at a relatively higher frequency range above the passband range.

[0041] Figure 4 According to an embodiment of the present technology Figure 3 Schematic diagram of the spectrum characteristics of the reconfigurable filter. This diagram is only an example, which should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, alternatives and modifications. In an embodiment, the first circuit 310 itself is configured to form a filter having a common passband from a first frequency f1 to a second frequency f2 (f2>f1). The second circuit 320 itself is configured to form a filter having a lower passband from a frequency not less than the first frequency f1 to a third frequency f3≤f2. The third circuit 330 itself is configured to form a filter having a higher passband from a fourth frequency f4 (f4≥f1) to a frequency not greater than the second frequency f2. When the switch 340 is controlled to connect the first circuit 310 to the second circuit 320, its corresponding spectrum is combined to form a first effective filter device mainly configured with a lower passband. When the switch 340 is controlled to connect the first circuit 310 to the third circuit 330, its corresponding spectrum is combined to form a second effective filter device mainly reconfigured with a higher passband. The first loop 310 becomes a common section of the first effective filter and the second effective filter.

[0042] From an alternative perspective, the first effective filter and the second effective filter can be distinguished by focusing on their respective rejection bands, which automatically determines their respective passbands and the rejection loss from the passband frequencies to the rejection band frequencies. In an embodiment, the first circuit is configured to have a first rejection band below a fifth frequency f5 and a second rejection band above a sixth frequency f6. The first effective filter (combining the first circuit and the second circuit) has a third rejection band below a seventh frequency f7 and a fourth rejection band above an eighth frequency f8, where the seventh frequency is aligned with the fifth frequency f5. The second effective filter (combining the first circuit and the third circuit) has a fifth rejection band below a ninth frequency f9 and a sixth rejection band above a tenth frequency f 10 10, where the tenth frequency is aligned with the sixth frequency f6. By making appropriate design choices regarding the number of series or shunt resonators and their respective spectral responses around their resonant and anti-resonant frequencies, the fifth frequency can be made less than the first frequency, f5 < f1, and the sixth frequency can be made greater than the second frequency, f6 > f2, thus giving a gap from the first passband to the first and second rejection bands. Specifically, the spectral roll-off characteristics and the steepness of the power drop can be controlled with an enhanced quality factor in a small frequency gap. Similarly, the eighth frequency f8 is greater than the third frequency f3 and the ninth frequency f9 is less than the fourth frequency f4. Additionally, the seventh frequency f7 can be aligned with the fifth frequency f5 and the tenth frequency f 10 10 can be aligned with the sixth frequency f6 to make the corresponding spectral roll-off steeper. In an implementation, the filter 300 can be reconfigured and can be configured as a lower band filter or a higher band filter as needed. Optionally, 5 or more resonators can be selected for the series or shunt resonators to achieve an isolation of > 40 dB between the passband and the rejection band. In other words, the rejection of the third (or fifth) rejection band is deeper than that of the first rejection band, and the rejection of the fourth (or sixth) rejection band is deeper than that of the second rejection band.

[0043] In a particular embodiment, the first effective filter can be configured to have a narrower fourth passband from an eleventh frequency to a twelfth frequency, a seventh rejection band below a thirteenth frequency, and an eighth rejection band above a fourteenth frequency. The eleventh frequency is higher than the first frequency and the twelfth frequency is lower than the second frequency, i.e., the fourth passband is substantially a part within the first passband. The thirteenth frequency of the seventh rejection band is higher than the fifth frequency. However, due to the combined effect of the first filter and the second filter, the rejection of the seventh rejection band is deeper than that of the first rejection band. The fourteenth frequency of the eighth rejection band is lower than the sixth frequency. However, the rejection of the eighth rejection band is deeper than that of the second rejection band.

[0044] Figure 5is a simplified circuit system diagram of a reconfigurable filter for a wireless communication system according to another embodiment of the present technology. This figure is only an example and should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, alternatives and modifications. In another embodiment, the reconfigurable filter device 500 includes a first circuit 510, a second circuit 520 and a third circuit 530, wherein the first circuit, the second circuit and the third circuit are respectively configured as a first filter having a common passband and a common rejection band, a second filter having a lower passband and a third filter having a higher passband. Each of the first circuit, the second circuit and the third circuit can be constructed by a (simulated) transmission line assembled by a plurality of resonators in a series and shunt configuration. Optionally, the resonator is a FBAR resonator characterized by one or more resonant frequencies and anti-resonant frequencies to express a specific spectral response in a peak or trough. The combined effect of a plurality of resonators in a series and shunt configuration results in a specific passband and rejection band under a specific frequency range of interest.

[0045] The reconfigurable filter device 500 further includes a switch 550 configured to connect the first circuit 510 to the second circuit 520 to reconfigure the first filter with a lower passband, or to connect the first circuit 510 to the third circuit 530 to reconfigure the second filter with a higher passband. In addition, the reconfigurable filter device 500 includes a fourth circuit 540 coupled between the first circuit 510 and the second circuit 520 in parallel with the connection between the first circuit 510 and the second circuit 520 established by the switch 550 from the input port to the first output port. For the fourth loop, the first filter now becomes the first effective filter. Optionally, the fourth circuit 540 includes a capacitor 541. Optionally, the fourth circuit 540 includes a resonator 541. Optionally, the capacitor 541 has one terminal coupled to the common terminal of the last series resonator 513s and the last shunt resonator 513p of the first circuit 510. The first terminal of the first series resonator 531s in the third circuit 530 is coupled to the second output port of the switch 550. A second terminal of the first series resonator 531s is coupled to a terminal of the first shunt resonator 531p of the third circuit 530. The capacitor 541 has the other terminal coupled to a first terminal of the first series resonator 521s of the second circuit 520. A first terminal of the first series resonator 521s of the second circuit 520 is coupled to a first output port of the switch 550. A second terminal of the first series resonator 521s of the second circuit 520 is coupled to a first terminal of the first shunt resonator 521p of the second circuit 520.

[0046] The fourth circuit 540 with capacitor 541 is configured to cause a downward shift reduction in the maximum impedance value at the lower anti-resonance frequency of the last series resonator 513s in the first circuit 510. In this case, the first circuit and the second circuit are combined with the fourth circuit to form a new first effective filter with some changes in the fourth rejection band. The second filter remains unchanged (as a second effective filter). Accordingly, the spectrum trough response appears at a slightly different frequency, or the new first effective filter has a deeper rejection band that is enhanced with a steeper rejection loss at a frequency slightly greater than the band edge frequency. Adding the fourth circuit 540 provides an additional reconfigurable scheme for the first effective filter. Figure 6 is a simplified graph showing the anti-resonance frequency tuned by the added circuit according to an embodiment of the present technology. Figure 6 As shown in FIG. 5 , the peak impedance of about 80 dB of the last series resonator 513 s of the first circuit 510 corresponds to the anti-resonance frequency, which is 513s (~2,436GHz) down to f' 513s (~2.419GHz). The downward shift of the peak response in impedance is equivalent to the downward shift of the trough response in power transmission. Due to this change in the spectral response, the fourth rejection band of the new first effective filter can have a steeper rejection loss for frequencies slightly above the rejection band edge f6, thereby enhancing the quality factor of the first effective filter. Optionally, the fourth circuit 540 may include a resonator.

[0047] In an alternative embodiment, a fourth circuit 540 including an inductor or a resonator may be configured to couple between the last series resonator 513s in the first circuit 510 and the first series resonator 531s in the third circuit 530. In essence, the fourth circuit adds an additional signal path for the last series resonator 513s to provide a lower impedance to change the spectral response. As a result, the anti-resonance frequency of the last series resonator 513s in the first circuit 510 is shifted slightly higher. This shift may be slightly higher than the band edge f of the sixth rejection band of the new second effective filter (which is combined with the first circuit 510, the third circuit 530, and the fourth circuit 540). 10 This effectively results in steeper rejection losses at frequencies of , thereby enhancing the performance of the reconfigurable filter.

[0048] In a particular embodiment, the first effective filter is characterized by a fourth passband, which is configured to be narrower than the first passband (or a portion within the first passband). The first effective filter is also characterized by a seventh rejection band that is lower than an eleventh frequency, which is higher than the fifth frequency. However, the combined effect of the first circuit, the second circuit, and the fourth circuit provides a seventh rejection, which is deeper than the first rejection band. In addition, the first effective filter may be characterized by an eighth rejection band that is higher than a twelfth frequency, which is lower than the sixth frequency. However, the eighth rejection band is deeper than the second rejection band.

[0049] Figure 7 7 is a simplified circuit system diagram of a reconfigurable filter for a wireless communication system according to another embodiment of the present technology. This diagram is only an example, which should not unduly limit the scope of the claims. Those skilled in the art will recognize many variations, alternatives and modifications. In an alternative embodiment, the reconfigurable filter device 700 includes a circuit 710, which includes a first plurality of resonators in a series and shunt circuit system from port 701 to port 711 characterized by a first passband from a first frequency to a second frequency. The resonators in the series circuit system are represented by series resonators 713s and the resonators in the shunt circuit system are represented by shunt resonators 713p. Circuit 710 also includes a second plurality of resonators in a series and shunt circuit system from port 712 to port 702 characterized by a second passband from a first frequency to a third frequency, which are represented by series resonators 714s and shunt resonators 714p. Circuit 710 further includes a third plurality of resonators in a series and shunt circuit system from port 713 to port 703 characterized by a third passband from a fourth frequency to the second frequency, represented by a series resonator 715s and a shunt resonator 715p. In addition, circuit 710 includes a capacitor 7112 coupled between the first plurality of resonators and the second plurality of resonators. With appropriate selection of the series resonator and the shunt resonator, the third frequency can be configured to be lower than the second frequency but higher than the first frequency. The fourth frequency can be configured to be higher than the first frequency but lower than the second frequency. By integrating all resonators and capacitors inside a chip and using each of those ports 701, 711, 712, 702, 713 and 703 as surface contacts, circuit 710 can be provided as an individual chip die.

[0050] In addition, the reconfigurable filter device 700 includes a switch 750 having an input port 751 and a first output port 752 and a second output port 753. The switch 750 is controlled to connect the input port 751 to the first output port 752 or the second output port 753. The input port 751 can be coupled to the port 711 to connect with the first plurality of resonators in the series and shunt circuit system. The first output port 752 is coupled to the port 712 to connect with the second plurality of resonators in the series and shunt circuit system. The second output port 753 is coupled to the port 713 to connect with the third plurality of resonators in the series and shunt circuit system. When the switch 750 is controlled to connect the input port 751 to the first output port 752, the reconfigurable filter device 700 is configured as a first filter having a second passband with additional rejection in the corresponding rejection band. When the switch 750 is controlled to connect the input port 751 to the second output port 753, the reconfigurable filter device 700 is reconfigured into a second filter having a third passband with additional rejection in a corresponding rejection band.

[0051] Although specific embodiments have been fully described above, various modifications, alternative constructions and equivalents may be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the present technology, which is defined by the appended claims.

Claims

1. A filter device for multi-band wireless communication, comprising: a first circuit characterized by a first passband from a first frequency to a second frequency, the second frequency being greater than the first frequency; a second circuit characterized by a second passband from a frequency not less than the first frequency to a third frequency, the third frequency not higher than the second frequency but higher than the first frequency; a third circuit characterized by a third passband from a fourth frequency to a frequency no greater than the second frequency, the fourth frequency being no less than the first frequency but less than the second frequency; and A switch configured to connect the first circuit to the second circuit to reconfigure the first filter with the second passband, or to connect the first circuit to the third circuit to reconfigure the second filter with the third passband, wherein at least one of the second passband and the third passband is narrower than the first passband.

2. The device of claim 1, wherein the first circuit comprises a first rejection band below a fifth frequency and a second rejection band above a sixth frequency, the fifth frequency being lower than the first frequency and the sixth frequency being higher than the second frequency.

3. The device of claim 2, wherein the first filter comprises a third rejection band below a seventh frequency and a fourth rejection band above an eighth frequency, the seventh frequency being aligned with the fifth frequency, the eighth frequency being greater than the third frequency but less than the sixth frequency.

4. The device of claim 2, wherein the second filter comprises a fifth rejection band below a ninth frequency and a sixth rejection band above a tenth frequency, the ninth frequency being less than the fourth frequency but greater than the fifth frequency, the tenth frequency being aligned with the sixth frequency.

5. The apparatus of claim 3 , wherein the first circuit comprises a plurality of first resonators coupled in series in a transmission line and a plurality of second resonators coupled in parallel with the transmission line, each first resonator being characterized by a respective anti-resonant frequency associated with the sixth frequency, and each second resonator being characterized by a respective resonant frequency associated with the fifth frequency. 6 . The device of claim 5 , wherein each of the first resonator and the second resonator comprises a film bulk acoustic resonator (FBAR).

7. The device of claim 5 , wherein the second circuit comprises a plurality of third resonators coupled in series in a transmission line and a plurality of fourth resonators coupled in parallel with the transmission line, each third resonator being characterized by a respective anti-resonance frequency associated with the eighth frequency, each fourth resonator being characterized by a respective resonant frequency associated with the seventh frequency, each of the third resonators and the fourth resonators comprising a film bulk acoustic resonator (FBAR).

8. The device of claim 7 , wherein the third rejection band comprises at least 40 dB of loss for frequencies less than the seventh frequency due to an aggregation of each peak impedance contribution from each fourth resonator and the second resonator at the respective resonant frequencies where the seventh frequency is aligned with the fifth frequency.

9. The device of claim 7, wherein the fourth rejection band comprises at least 40 dB of loss for frequencies greater than the eighth frequency due to an aggregation of each peak impedance contribution from each third resonator and the first resonator at the respective anti-resonant frequency.

10. The device of claim 4, wherein the third circuit comprises a plurality of fifth resonators coupled in series in a transmission line and a plurality of sixth resonators coupled in parallel with the transmission line, each fifth resonator being characterized by a respective anti-resonance frequency associated with the tenth frequency, each sixth resonator being characterized by a respective resonant frequency associated with the ninth frequency, each of the fifth resonators and the sixth resonator comprising a film bulk acoustic resonator (FBAR).

11. The device of claim 10, wherein the fifth rejection band comprises at least 40 dB of loss for frequencies less than the ninth frequency due to an aggregation of each peak impedance contribution from each sixth resonator and the second resonator at the respective resonant frequency.

12. The device of claim 11 , wherein the sixth rejection band comprises at least 40 dB of loss for frequencies greater than the tenth frequency due to an aggregation of each peak impedance contribution of each fifth resonator and the first resonator at the respective anti-resonant frequencies where the tenth frequency is aligned with the sixth frequency.

13. The device according to claim 3, wherein the first filter includes a fourth passband from an eleventh frequency to a twelfth frequency, a seventh rejection band lower than a thirteenth frequency, and an eighth rejection band higher than a fourteenth frequency, the eleventh frequency is higher than the first frequency, the twelfth frequency is lower than the second frequency, the thirteenth frequency is higher than the fifth frequency but the rejection of the seventh rejection band is deeper than the first rejection band, the fourteenth frequency is lower than the sixth frequency but the rejection of the eighth rejection band is deeper than the second rejection band.

14. A reconfigurable filter device comprising: a first circuit characterized by a first passband from a first frequency to a second frequency, the second frequency being higher than the first frequency; a second circuit characterized by a second passband from a frequency not less than the first frequency to a third frequency, the third frequency not higher than the second frequency but higher than the first frequency; a third circuit characterized by a third passband from a fourth frequency to a frequency no greater than the second frequency, the fourth frequency being no less than the first frequency but less than the second frequency; a switch including an input port coupled to the first circuit, a first output port coupled to the second circuit, and a second output port coupled to the third circuit, the switch being configured to receive at the input port a first signal filtered by the first circuit with the first passband and deliver the first signal to the first output port for reconfiguring a second signal filtered by the second circuit with the second passband, or to deliver the first signal directly to the second output port for reconfiguring a third signal filtered by the third circuit with the third passband; and A fourth circuit is coupled in parallel to the switch between the first circuit and the second circuit or the third circuit and is configured to implement a rejection band for the second signal or the third signal.

15. The apparatus of claim 14, wherein the first circuit comprises a plurality of first resonators coupled in series in a transmission line and a plurality of second resonators coupled in parallel with the transmission line, the plurality of second resonators generating a first rejection band below a fifth frequency, the plurality of first resonators generating a second rejection band above a sixth frequency, the fifth frequency being lower than the first frequency, and the sixth frequency being higher than the second frequency.

16. The apparatus of claim 15, wherein the second circuit comprises a plurality of third resonators coupled in series in a transmission line and a plurality of fourth resonators coupled in parallel with the transmission line, the second circuit in combination with the first circuit producing a first filter having the second passband, the plurality of fourth resonators and the plurality of second resonators providing a third rejection band to the first filter, the third rejection band having a higher loss than the first rejection band below a seventh frequency, the plurality of third resonators and the plurality of first resonators providing a fourth rejection band to the first filter, the fourth rejection band having a higher loss than the second rejection band above an eighth frequency, the seventh frequency being aligned with the fifth frequency, the eighth frequency being higher than the third frequency.

17. The apparatus of claim 16, wherein the third circuit comprises a plurality of fifth resonators coupled in series in a transmission line and a plurality of sixth resonators coupled in parallel with the transmission line, the third circuit in combination with the first circuit producing a second filter having the third passband, the plurality of sixth resonators and the plurality of second resonators providing a fifth rejection band to the second filter, the fifth rejection band having a higher loss than the first rejection band below a ninth frequency, the plurality of fifth resonators and the plurality of first resonators providing a sixth rejection band to the second filter, the sixth rejection band having a higher loss than the second rejection band above a tenth frequency, the ninth frequency being lower than the fourth frequency, the tenth frequency being aligned with the sixth frequency.

18. The device of claim 17, wherein the fourth circuit comprises a capacitor or an inductor or a resonator configured to reconfigure the first filter or the second filter to have increased rejection loss by shifting an anti-resonance frequency of one of the first resonators in the first circuit.

19. The device of claim 16 , wherein the first filter is alternatively characterized by a fourth passband configured to be narrower than and within the first passband, a seventh rejection band below an eleventh frequency higher than the fifth frequency, and an eighth rejection band above a twelfth frequency lower than the sixth frequency, the seventh rejection band having a deeper rejection than the first rejection band, and the eighth rejection band having a deeper rejection than the second rejection band.

20. A reconfigurable filter device comprising: a circuit comprising a first plurality of resonators in a series and shunt circuit system characterized by a first passband from a first frequency to a second frequency, a second plurality of resonators in the series and shunt circuit system characterized by a second passband from a frequency not less than the first frequency to a third frequency, a third plurality of resonators in the series and shunt circuit system characterized by a third passband from a fourth frequency to a frequency not greater than the second frequency, and a capacitor coupled between the first plurality of resonators and the second plurality of resonators; and A switch is configured to couple to the circuit to connect the first plurality of resonators to the second plurality of resonators to reconfigure the first filter with the second passband and the deeper rejection band, or to connect the first plurality of resonators to the third plurality of resonators to reconfigure the second filter with the third passband and the deeper rejection band.

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