Transformer-based wideband filter with ripple reduction

Abstract

The present disclosure relates to transformer-based wideband filters with reduced ripple. A radio frequency filter circuit includes a first inductor, a second inductor, and a conductive loop. The first inductor receives a first current, the first current inducing a second current in the second inductor when the first current is received. The first inductor and / or the second inductor induces a third current in the conductive loop. The conductive loop adjusts the third current to reduce a first gain peak of an output signal relative to a second gain peak of the output signal.

Description

BACKGROUND

[0001] The present disclosure relates generally to electronic devices, and more particularly to electronic devices that transmit and receive radio frequency signals for wireless communication.

[0002] This section is intended to introduce the reader to various aspects of art that can be related to various aspects of the present disclosure and is not intended to limit the scope of the present disclosure. The following discussion is believed to be helpful in providing the reader with a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0003] Electronic communication devices can include radio frequency filter circuits that allow certain frequencies in an output signal to pass or block, such that the signal can be transmitted on desired frequencies. By way of example, many electronic devices utilize radio frequency filter circuits that include wideband filters to allow signals within a wide bandwidth (e.g., a large range of frequencies) to pass. The radio frequency filter circuits can include one or more coupled resonators to form one or more filters. A resonator can refer to a device, system, or circuit that exhibits oscillations with relatively large amplitudes at some frequencies (e.g., resonant frequencies). Resonant circuits include discrete components that act as resonators when both inductors and capacitors are included. In such circuits, oscillations can be limited by including resistance through a particular resistor component or due to resistance of the inductor windings (e.g., resistor-inductor-capacitor (RLC) circuits). SUMMARY

[0004] A summary of certain implementations disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain implementations and that neither this summary nor the following detailed description are

[0005] A radio frequency filter circuit includes a transformer-based resonator that allows or blocks certain frequencies in an output signal (e.g., an outgoing signal) such that the signal can be transmitted on desired frequencies. Additionally or alternatively, the transformer-based resonator can provide a wideband impedance match within an amplifier (e.g., over a range of available impedances and over a wide range of frequencies). By way of example, the transformer-based resonator can be used for input matching, output matching, and / or inter-stage matching within an amplifier. The resonator includes a first inductor (e.g., one or more coils), a second inductor (e.g., one or more coils), and a conductive loop. The conductive loop includes a resistor, which can be a programmable variable resistor or a static resistor.

[0006] When the power supply supplies current to the first inductor, the first inductor induces current in the second inductor via the "transformer effect." Specifically, the current in the first inductor can include two parts: a first even mode current and a first odd mode current. The first even mode current causes a second even mode current in the second inductor, and the first odd mode current causes a second odd mode current in the second inductor. The first even mode current and the second even mode current travel in the same direction through the first inductor and the second inductor. On the other hand, the first odd mode current and the second odd mode current travel in opposite directions through the first inductor and the second inductor.

[0007] Because the first odd mode current flowing through the first inductor and the second odd mode current flowing through the second inductor have equal magnitudes and flow in opposite directions, the currents can cancel each other out with respect to the conductive loop, such that there is no transfer of current in the conductive loop. As a result, current cannot travel through the resistor coupled to the conductive loop. In this way, and as described below, the conductive loop with the resistor can affect the frequency response associated with the even mode currents (e.g., a gain peak at a low frequency) to reduce the in-band ripple, but cannot affect the frequency response associated with the odd mode currents (e.g., a gain peak at a high frequency).

[0008] The first even mode current and the second even mode current flowing through the first inductor and the second inductor generate an induced current in the conductive loop that at least partially reduces a first gain peak (e.g., at a low frequency pole in the frequency response) of the output signal to correlate with (e.g., approximately match) a second gain peak of the output signal due at least in part to the resistor. In this way, the in-band ripple between the gain peaks can be reduced. As described above, the in-band ripple can refer to the frequency response of the operating region of the resonator, which includes the first pole, the second pole, and between the two poles. Otherwise, the resonator of the radio frequency filter circuit can produce a frequency response with in-band ripple, which can result in poor error vector magnitude (EVM) and / or signal-to-noise ratio (SNR) values when the electronic device including the radio frequency filter circuit is transmitting the output signal. In some embodiments, the resonator can also include one or more shunt resistors and / or one or more series resistors. These resistors can improve the performance of the resonator at least in part by reducing the difference in the peaks across the frequency response including the first peak gain and the second peak gain, thereby further smoothing the in-band ripple.

[0009] One aspect of the disclosure provides a radio frequency filter circuit. The radio frequency filter circuit includes a first inductor, a second inductor, and a conductive loop. The first inductor receives a first current, and the second inductor is inductively coupled to the first inductor based on the first current. The first current induces a second current in the second inductor. The conductive loop is inductively coupled to at least one of the first inductor and the second inductor, thereby inducing a third current in the conductive loop. The conductive loop adjusts the third current to reduce a first gain peak of an output signal to correlate to a second gain peak of the output signal.

[0010] Another aspect of the disclosure provides an electronic device having a radio frequency filter circuit. The electronic device has a current source, a first coil coupled to the current source, a second coil, a conductive loop, and a resistor. The first coil generates a first even mode current and a first odd mode current in the first coil based on a current received from the current source. The second coil conducts a second even mode current induced by the first even mode current, where the first even mode current flows through the first coil and the second even mode current flows through the second coil in the same direction. The second coil conducts a second odd mode current induced by the first odd mode current, where the odd mode current flows through the first coil and the second odd mode current flows through the second coil in the opposite direction. The conductive loop conducts an induced current, where the induced current is induced by the first even mode current traveling through the first coil and the second even mode current traveling through the second coil. The resistor is coupled to the conductive loop and adjusts the induced current to reduce a first gain peak of a frequency response of the radio frequency filter circuit to a second gain peak of the frequency response for an output signal.

[0011] Still another aspect of the disclosure provides a transformer-based resonator. The transformer-based resonator includes a first inductor, a second inductor, a third inductor, and a variable resistor. Upon supplying a current to the first inductor, the first inductor transmits a first even mode current and a first odd mode current. The second inductor transmits a second even mode current induced by the first even mode current that travels in the same direction as the first even mode current, and transmits a second odd mode current induced by the first odd mode current that travels in the opposite direction as the first odd mode current. The third inductor transmits an induced current that is induced by the first even mode current traveling through the first inductor and the second even mode current traveling through the second inductor. The variable resistor adjusts a coupling factor between the first inductor and the second inductor to reduce an in-band ripple between a first gain peak of a frequency response of the transformer-based resonator and a second gain peak of the frequency response of the transformer-based resonator.

[0012] Various modifications can be made to the above described features to various aspects of the present application. Other features can also be added to these various aspects. These modifications and additional features can exist alone or in any combination. For example, various features discussed below in relation to one or more illustrated embodiments can be incorporated into any of the above described aspects of the present application, alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of implementations of the disclosure, and does not limit the claimed subject matter. BRIEF DESCRIPTION OF DRAWINGS

[0013] Various aspects of the disclosure can be better understood when read in conjunction with the following detailed description and reference to the drawings, in which:

[0014] FIG. 1 is a block diagram of an electronic device according to an embodiment of the disclosure;

[0015] FIG. 2 is a perspective view of a notebook computer representing an embodiment of the electronic device of FIG. 1

[0016] FIG. 3 is a front view of a handheld device representing another embodiment of the electronic device of FIG. 1

[0017] FIG. 4 is a front view of another handheld device representing another embodiment of the electronic device of FIG. 1

[0018] FIG. 5 is a front view of a desktop computer representing another embodiment of the electronic device of FIG. 1

[0019] FIG. 6 is a front view and a side view of a wearable electronic device representing another embodiment of the electronic device of FIG. 1

[0020] FIG. 7 is a circuit diagram of a transformer-based coupled resonator of a radio frequency filter circuit;

[0021] FIG. 8 is a schematic diagram of a resonator implemented on a silicon chip of FIG. 7

[0022] FIG. 9A is a circuit diagram of a resonator of FIG. 7 having a series resistor and a shunt resistor;

[0023] FIG. 9B is a circuit diagram of a resonator of FIG. 9A showing even mode current flowing through the resonator;​​​​​​

[0024] FIG. 9C is a circuit diagram of a resonator of FIG. 9A showing odd mode current flow through the resonator;

[0025] FIG. 10 is a plot of frequency poles of a frequency response of a resonator of FIG. 9A ;

[0026] FIG. 11A is a circuit diagram of a resonator of a conductive loop showing in-band ripple of a frequency response of the resonator having reduced FIG. 7 according to embodiments of the present disclosure;

[0027] FIG. 11B is a circuit diagram of a resonator of FIG. 11A showing even mode current flow according to embodiments of the present disclosure;

[0028] FIG. 11C is a circuit diagram of a resonator of FIG. 11A showing odd mode current flow according to embodiments of the present disclosure;

[0029] FIG. 12 is a schematic diagram of a resonator of FIG. 11A according to embodiments of the present disclosure;

[0030] FIG. 13A is a schematic diagram of a cross-sectional view of a resonator of FIG. 11A according to embodiments of the present disclosure;

[0031] FIG. 13B is a schematic diagram of a perspective view of a resonator of FIG. 11A according to embodiments of the present disclosure; and

[0032] FIG. 14 is a plot of frequency poles of a frequency response of an output signal of an operating region of a resonator of FIG. 11B according to embodiments of the present disclosure. DETAILED DESCRIPTION

[0033] One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which can vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0034] When introducing elements of various embodiments of the present disclosure, the articles "a," "an," and "the" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there can be additional elements other than the listed elements. Additionally, it should be understood that references to "one embodiment" or "an embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate those features. Use of the term "about" or "approximately" in connection with a quantity is meant to include not only the amount exact to the indicated value, but also amounts that are close to the indicated value.

[0035] As used herein, the term "frequency response" refers to a gain of an output signal as a function of frequency within a range of frequencies (e.g., an operating region of a resonator filter). Additionally, as used herein, the term "frequency pole" refers to a frequency at which a transfer function of a system approaches a high gain or amplitude (e.g., infinity). By way of example, a frequency pole can include a particular frequency having a highest gain or amplitude, or a relatively high gain or amplitude, of a frequency response of a resonator filter (e.g., a high frequency pole and a low frequency pole). As used herein, the terms "peak," "peak gain," or "gain peak" refer to a highest gain or amplitude, or a relatively high gain or amplitude, at a frequency pole (e.g., a gain peak at a high frequency pole). The relatively high gain at the particular frequency produces a peak relative to a relatively low gain at other frequencies of the frequency response. Further, as used herein, the term "uneven gain" refers to a difference between two or more gain peaks (e.g., a gain difference between a gain peak at a low frequency pole and a gain peak at a high frequency pole). As used herein, the term "in-band ripple" refers to a ripple or variation in a frequency response of a resonator filter including a first pole, a second pole, and an operating region between the two poles. The ripple includes a difference or variation in gain peaks between the two gain peaks at the frequency poles, with a gain dip between the two gain peaks.

[0036] Radio frequency (RF) filter circuits may include transformer-based resonators, which may include multiple inductors, such as a primary inductor (e.g., a first inductor) and a secondary inductor (e.g., a second inductor). If the primary inductor receives current, such as from a current source, it can transfer the current to the second inductor, thus inducing a current in the secondary inductor. Specifically, the current in the primary inductor can change as it flows through the inductor's coil, generating a changing magnetic field (e.g., magnetic flux) that induces the current in the secondary inductor. This transfer of current or electrical energy from one inductor to another due to the changing magnetic field is known as the "transformer effect."

[0037] In some cases, some current from the primary inductor may not be transferred to the secondary inductor. Instead, this current may not follow the expected path through the coil of the primary inductor. This portion of the current can be referred to as leakage flux. The extent of the transfer can be measured by various parameters, including the coupling coefficient k. The coupling coefficient can be adjusted or tuned, for example, by circuit elements (e.g., resistors or capacitors coupled to the first and / or second inductors), to change filter parameters and bandwidth. However, adjusting the coupling coefficient alone may not provide a tuning effect that reduces the non-uniform gain of the output signal (e.g., the in-band signal) at different frequency poles (e.g., low-frequency poles and high-frequency poles), resulting in persistently unintended and / or undesirable filter performance. Therefore, electronic devices with RF filtering circuitry can benefit from circuitry that provides the same or substantially the same gain (e.g., similar and within the gain threshold) of the output signal at different frequency poles.

[0038] The embodiments disclosed herein can be applied to a variety of electronic devices with radio frequency (RF) filtering circuitry. Specifically, any electronic device transmitting signals over a communication network can incorporate the RF filtering circuitry disclosed herein to ensure signal transmission with similar gain over a target frequency range, excluding the expected gain applied to the signal at a specific frequency. In light of the foregoing, a general description of suitable electronic devices that may include the disclosed RF filtering circuitry is provided below.

[0039] Considering the foregoing, there are various suitable communication devices that may include the radio frequency filtering circuit disclosed herein. First, let's turn to... FIG. 1 The electronic device 10 according to the embodiments of the present disclosure may, among other things, include one or more processors 12, memory 14, non-volatile storage device 16, display 18, input structure 22, input / output (I / O) interface 24, network interface 26, power supply 28, and transceiver 30. FIG. 1 The various functional blocks shown may include hardware elements (including circuits), software elements (including computer code stored on a computer-readable medium), or a combination of both hardware and software elements. It should be noted that...FIG. 1 is merely one example of a particular implementation and is intended to illustrate the types of components that can be present in electronic device 10.

[0040] By way of example, electronic device 10 can represent a block diagram of a notebook computer as shown in FIG. 1, FIG. 2 a handheld device as shown in FIG. 2, FIG. 3 a handheld device as shown in FIG. 2, FIG. 4 a handheld device as shown in FIG. 2, FIG. 5 a desktop computer as shown in FIG. 3, FIG. 6 a wearable electronic device as shown in FIG. 4, or similar devices. It should be noted that FIG. 1 Processor 12 and other related items in FIG. 1 can be generally referred to herein as "data processing circuitry." Such data processing circuitry can be implemented in whole or in part as software, hardware, or any combination thereof. Moreover, processor 12 and other related items in FIG. 1 can be a single, stand-alone processing module or can be incorporated in whole or in part within any of the other elements within electronic device 10. FIG. 1

[0041] In electronic device 10 of FIG. 1, processor 12 can be operatively coupled with memory 14 and non-volatile storage 16 to execute various algorithms. Such programs or instructions for execution by processor 12 can be stored in any suitable article of manufacture including one or more tangible computer readable media. Tangible computer readable media can include memory 14 and / or non-volatile storage 16, individually or collectively, to store instructions or routines. Memory 14 and non-volatile storage 16 can include any suitable article of manufacture for storing data and executable instructions, such as random access memory, read only memory, re-writable flash memory, hard drives, and optical discs. Moreover, programs (e.g., operating systems) encoded on such computer program products can also include instructions executable by processor 12 to enable electronic device 10 to provide various functionality. FIG. 1 In certain embodiments, display 18 can be a liquid crystal display (LCD) that can facilitate a user viewing images generated on electronic device 10. In some embodiments, display 18 can include a touch screen that can facilitate a user interacting with a user interface of electronic device 10. Moreover, it should be appreciated that in some embodiments, display 18 can include one or more light emitting diode (LED) displays, organic light emitting diode (OLED) displays, active matrix organic light emitting diode (AMOLED) displays, or some combination of these and / or other display technologies.

[0042]

[0043] ​​The input structure 22 of the electronic device 10 can enable a user to interact with the electronic device 10 (e.g., to press a button to increase or decrease a volume level). As with the network interface 26, the I / O interface 24 can enable the electronic device 10 to interact with various other electronic devices. The network interface 26 may, for example, include one or more interfaces for a personal area network (PAN) such as a Bluetooth® network, a local area network (LAN) or wireless local area network (WLAN) such as an 802.11x network, and / or a wide area network (WAN) such as a 3rd Generation (3G) cellular network, a Universal Mobile Telecommunications System (UMTS), a 4th Generation (4G) cellular network, a Long Term Evolution cellular network, a Long Term Evolution Licensed Assisted Access (LTE-LAA) cellular network, a 5th Generation (5G) cellular network, and / or a New Radio (NR) cellular network. In particular, the network interface 26 may, for example, include one or more interfaces for Release-15 cellular communication standards using the 5G specification including millimeter wave (mmWave) frequency ranges (e.g., 24.25-300 gigahertz (GHz)). The transceiver 30 of the electronic device 10, including a transmitter and a receiver, can allow for communication over the aforementioned networks (e.g., 5G, Wi-Fi, LTE-LAA, etc.).

[0044] The network interface 26 may, for example, also include one or more interfaces for a broadband fixed wireless access network (e.g., ), a mobile broadband wireless network (mobile ), an Asynchronous Digital Subscriber Line (e.g., ADSL, VDSL), a Digital Video Broadcast network, and its extension DVB-Handheld network, an Ultra Wide Band (UWB) network, an alternating current (AC) power line, etc.

[0045] In some embodiments, the electronic device 10 uses the transceiver 30 to communicate over the aforementioned wireless networks (e.g., mobile 4G, 5G, etc.). The transceiver 30 can include circuitry available both in wireless reception and wireless transmission signals (e.g., data signals, wireless data signals, wireless carrier signals, RF signals), such as a transmitter and / or a receiver. In fact, in some embodiments, the transceiver 30 can include a transmitter and a receiver combined into a single unit, or in other embodiments, the transceiver 30 can include a transmitter separate from a receiver. The transceiver 30 can transmit and receive RF signals to support wireless applications such as, for example, a PAN network (e.g., ), a WLAN network (e.g., 802.11x ), WAN networks (e.g., 3G, 4G, 5G, NR and (and LTE-LAA cellular network) Network, Mobile Network, ADSL and VDSL networks, and Voice and / or data communication in networks, UWB networks, etc. As further shown, electronic device 10 may include power supply 28. Power supply 28 may include any suitable power source, such as a rechargeable lithium polymer (Li-poly) battery and / or an alternating current (AC) power converter.

[0046] In some embodiments, electronic device 10 may take the form of a computer, portable electronic device, wearable electronic device, or other type of electronic device. Such a computer may be a typically portable computer (such as a laptop, notebook computer, and tablet computer) or a computer typically used in one location (such as a conventional desktop computer, workstation, and / or server). In some embodiments, electronic device 10 in the form of a computer may be a product purchased from Apple Inc., Cupertino, California. Pro, MacBook mini or Mac Model. By way of example, according to one embodiment of this disclosure, in... FIG. 2 An electronic device 10 in the form of a laptop computer 10A is shown. The laptop computer 10A shown may include a casing or housing 36, a display 18, input structures 22, and ports for I / O interfaces 24. In one embodiment, the input structures 22 (such as a keyboard and / or touchpad) can be used to interact with the computer 10A, such as to launch, control, or operate a graphical user interface (GUI) or applications running on the computer 10A. For example, the keyboard and / or touchpad can allow a user to navigate on the user interface and / or application interface displayed on the display 18.

[0047] FIG. 3 A front view of a handheld device 10B is depicted, representing one embodiment of an electronic device 10. The handheld device 10B can represent, for example, a portable telephone, media player, personal data manager, handheld gaming platform, or any combination of such devices. For instance, the handheld device 10B could be purchased from Apple Inc. (Cupertino, California). or Handheld device 10B may include a housing 36 to protect internal components from physical damage and / or shield them from electromagnetic interference. The housing 36 may enclose the display 18. I / O interface 24 can be opened through the housing 36 and may include, for example, I / O ports for hardwired connections to allow charging and / or content manipulation using standard connectors and protocols such as the Lightning connector supplied by Apple Inc. of Cupertino, California, Universal Serial Bus (USB), or other similar connectors and protocols.

[0048] Input structure 22, in conjunction with display 18, allows the user to control handheld device 10B. For example, input structure 22 can activate or deactivate handheld device 10B, navigate the user interface to a home screen, a user-configurable application screen, and / or activate voice recognition features of handheld device 10B. Other input structures 22 may provide volume control or switch between vibration and ringtone modes. Input structure 22 may also include a microphone for acquiring user voice for various voice-related features, and a speaker for enabling audio playback and / or certain telephone functions. Input structure 22 may also include a headphone input for connecting to external speakers and / or headphones.

[0049] FIG. 4 A front view of another handheld device 10C is depicted, representing another embodiment of electronic device 10. The handheld device 10C can represent, for example, a tablet computer, or one of various portable computing devices. For instance, the handheld device 10C can be a tablet-sized embodiment of electronic device 10, specifically, for example, a device purchased from Apple Inc. (Cupertino, California). Handheld device.

[0050] See FIG. 5 Computer 10D can represent FIG. 1 Another embodiment of the electronic device 10. The computer 10D can be any computer, such as a desktop computer, server, or laptop, but can also be a standalone media player or video game console. For example, the computer 10D could be a device from Apple Inc. in Cupertino, California. Or another similar device. It should be noted that computer 10D may also refer to a personal computer (PC) from another manufacturer. A similar housing 36 may be provided to protect and enclose the internal components of computer 10D, such as monitor 18. In some embodiments, the user of computer 10D may interact with computer 10D using various peripheral input structures 22 that can be connected to computer 10D, such as keyboard 22A or mouse 22B (e.g., input structure 22).

[0051] Similarly, FIG. 6 Depicting the representation FIG. 1 Another embodiment of the electronic device 10 is a wearable electronic device 10E, which can be configured to operate using the techniques described herein. By way of example, the wearable electronic device 10E, which may include a wristband 43, could be an Apple product of Apple, Inc., Cupertino, California. However, in other embodiments, the wearable electronic device 10E may include any wearable electronic device, such as, for example, a wearable motion monitoring device (e.g., a pedometer, accelerometer, heart rate monitor), or other devices from another manufacturer. The display 18 of the wearable electronic device 10E may include a touchscreen display 18 (e.g., an LCD, LED display, OLED display, active-matrix organic light-emitting diode (AMOLED) display, etc.) and an output structure 22 that allows the user to interact with the user interface of the wearable electronic device 10E.

[0052] Considering the above, FIG. 7 This is a schematic diagram of a transformer-based coupled resonator 50 for an RF filter circuit. Generally, a resonant circuit may include a first inductor and a second inductor. These inductors can form a transformer when placed too close together and current flows between them. That is, when current is received through the first inductor, the current in the first inductor can induce or transfer electrical energy (e.g., magnetic flux) from the first inductor to the second inductor. Each inductor in the resonant circuit coupled with a capacitor can be referred to as a magnetically coupled resonator, where energy oscillates between the coil of the inductor (e.g., the transformer) and a capacitor that stores energy at a specific resonant frequency in an electric field. The offset between the first and second inductors is often used to tune parameters of the transformer, such as the coupling coefficient k. In some cases, capacitors and / or resistors in the resonant circuit can be used to tune the coupling coefficient. Tuning allows for changes in the filter's bandwidth (e.g., a wider or narrower frequency range) and / or in-band ripple caused by non-uniform peak gain at multiple frequency poles. However, adjusting the coupling coefficient can lead to non-uniform gain of the output signal at multiple frequency poles, which can result in undesirable filter performance.

[0053] As shown in the depicted embodiment, transformer-based coupled resonator 50 has a first inductor 52 (LI), a second inductor 54 (L2), a first capacitor 56 (CI), and a second capacitor 58 (C2). The first inductor 52 can be coupled to the first capacitor 56, and the second inductor 54 can be coupled to the second capacitor 58. Each of these inductor-capacitor (LC) arrangements can function as an LC resonant circuit that stores energy oscillating at the resonant frequency of the circuit. LC circuits can generate signals at or pass signals through at a particular frequency (e.g., bandpass filters).

[0054] In general, resonator 50 can include coupling elements that facilitate wideband filtering. Coupling elements can include components that allow energy to be coupled or transferred from one inductive circuit segment (e.g., one or more coils of first inductor 52) to another inductive circuit segment (e.g., another one or more coils of second inductor 54). Coupling elements can be capacitive and / or magnetic. Capacitive coupling elements can provide transfer of energy between circuit segments due to changes in electric field caused by voltage. Magnetic coupling elements can provide transfer of energy due to changes in magnetic field caused by current.

[0055] As shown, resonator 50 includes capacitors on each inductor side, such as first capacitor 56 coupled to first inductor 52 and second capacitor 58 coupled to second inductor 54. These coupling elements can form a magnetically coupled resonator when current is applied to resonator 50. As will be discussed with respect to FIG. 3, the coupling between the inductors can be adjusted by adjusting the capacitance of the capacitors. FIG. 9A to FIG. 9C As discussed in detail, adjusting the coupling coefficient of resonator 50 can allow for adjustment of the bandwidth of the filter and / or the in-band ripple of the frequency response of the output signal through resonator 50.

[0056] FIG. 8A resonator 50 implemented on a silicon chip is shown. As illustrated, the resonator 50 can be formed with a first inductor 52 (indicated by the light dot pattern) and a second inductor 54 (indicated by the dark dot pattern) arranged in a multi-layer stack architecture on a printed circuit board 55 (PCB). While the following discussion describes a resonator 50 implemented on a PCB representative of a particular implementation, the resonator 50 can instead be implemented on a silicon chip or integrated circuit. The first inductor 52 and / or the second inductor 54 can be provided, such as by being mounted on the PCB 55 and / or etched onto a first (e.g., lower) layer of the PCB 55. Here, the first inductor 52 is provided (e.g., positioned) on the first layer of the PCB 55, while the second inductor 54 is provided on a second (e.g., higher or lower) layer of the PCB 55. In some implementations, a portion of the coil of the first inductor 52 can be provided on the first layer, while another portion of the coil of the first inductor 52 is provided on the second layer. In such implementations, the portions can be coupled with a via 53, such that current flowing (e.g., traveling) through the first inductor 52 can flow between the two layers without interruption. Similarly, the second inductor 54 can also include a portion of its coil provided on the second layer, while another portion of its coil is provided on another layer (e.g., a third layer higher than the second layer). The second inductor can also include a via 53 to couple the portions together. In some implementations, the circuit segments or components of the resonator 50 can be segregated on separate PCBs. That is, the first inductor 52 can be positioned on a first PCB, while the second inductor 54 is positioned on a second PCB coupled to the first PCB.

[0057] In implementations with even mode current, and as referenced with respect to FIG. 9B As discussed in detail, when current 70 (I) is applied to the first inductor 52 in the depicted stack architecture of the resonator 50, the current can flow through the first inductor 52 in the direction indicated by the solid arrow. In particular, the direction shown by the arrow illustrates the current 70 flowing through the coil of the first inductor 52 in a first direction. Upon receiving the current 70, the first inductor 52 can induce (e.g., generate, conduct, or transmit) a current 71 in the second inductor 54 that flows through the second inductor 54 in the same direction. In implementations with odd mode current, and as referenced with respect to FIG. 9CAs discussed in detail, when current 70 is applied to first inductor 52, current 70 can flow in a first direction through first inductor 52 and induce current 71 in second inductor 54. In particular, the direction indicated by the dashed arrow illustrates that, upon receiving current 70, first inductor 52 can induce current 71 in second inductor 54, which flows in a second direction opposite the first direction through second inductor 54. Although the following description describes current 70 flowing in the first direction through first inductor 52 (which represents a particular implementation), current 70 can flow in a different or opposite direction (e.g., the second direction) instead.

[0058] As a result of the transformer effect, first inductor 52 can induce a current in second inductor 54. Although not shown, the induced current through second inductor 54 can flow similarly to the flow in first inductor 52. In particular, and as will be described with reference to FIGS. 3-5, the induced current can flow in the same direction through second inductor 54 when current 70 is an even mode current, or in the opposite direction through second inductor 54 when current 70 is an odd mode current. FIG. 9B and FIG. 9C As discussed in detail, when current 70 is applied to first inductor 52, current 70 can flow in a first direction through first inductor 52 and induce current 71 in second inductor 54. In particular, the direction indicated by the dashed arrow illustrates that, upon receiving current 70, first inductor 52 can induce current 71 in second inductor 54, which flows in a second direction opposite the first direction through second inductor 54. Although the following description describes current 70 flowing in the first direction through first inductor 52 (which represents a particular implementation), current 70 can flow in a different or opposite direction (e.g., the second direction) instead.

[0059] Further, and as previously mentioned, the amplification or gain of the output signal (e.g., the transmission signal) at various frequencies and / or frequency poles can vary. In particular, the frequency response of the output signal through resonator 50 can indicate that the gain of the output signal at these various frequencies and / or frequency poles can be different (e.g., a relatively high gain at a low frequency pole and a relatively low gain at a high frequency pole), such that the gain peaks at the respective frequency poles are uneven, resulting in an "in-band ripple effect." The resonator 50 of the radio frequency filter circuit can cause the frequency response to have in-band ripples, which can result in poor EVM and SNR values when electronic device 10 transmits the output signal.

[0060] To improve the filtering performance, adjusting various filter parameters can enable adjusting the gain (e.g., increasing or decreasing the gain) of the output signal at particular frequencies and / or frequency poles. By adjusting the gain, the overall frequency response can become even and smooth, thereby removing the in-band ripples. To illustrate the components of the tunable filter parameters, FIG. 9A A resonator 50 is depicted having a capacitor, a resistor, a series resistor, and a shunt resistor.

[0061] As FIG. 9AAs shown, the resonator 50 may include a first inductor 52 (L1), a second inductor 54 (L2), a first capacitor 56 (C1), and a second capacitor 58 (C2). Here, the first capacitor 58 (C1) may be connected in parallel with the first resistor 57 (R1) and the first shunt resistor 60 (R3), while the second capacitor 58 may be connected in parallel with the second resistor 59 (R2) and the second shunt resistor 62 (R4). Furthermore, a first series resistor 64 (R5) may be connected in series with the first inductor 52 and the first capacitor 56. Similarly, a second series resistor 66 (R6) may be connected in series with the second inductor 54 and the second capacitor 58. While the depicted embodiments exemplify and describe a resonator 50 having both shunt resistors 60, 62 and series resistors 64, 66 for tuning radio frequency filter circuitry, the resonator 50 can be implemented without at least some of these resistors, such as without shunt resistors 60, 62 and / or without series resistors 64, 66. In some embodiments, each RLC circuit of the resonator 50, such as a first RLC circuit 73A including a first inductor 52, a first capacitor 56 and a first resistor 57, and a second RLC circuit 73B including a second inductor 54, a second capacitor 58 and a second resistor 59, can be implemented independently without shunt resistors 60, 62 and / or without series resistors 64, 66.

[0062] For reference FIG. 10 The operation of the resonator 50 in the RF filter circuit is discussed in detail via shunt resistors 60, 62 and / or series resistors 64, 66. In addition to adjusting the operation of the resonator 50 via shunt resistors 60, 62 and / or series resistors 64, 66, or as an alternative, the operation of the resonator 50 is adjusted via first resistor 57, second resistor 59 and / or capacitors 56, 58. Specifically, and as will be described herein, the network quality factor (Q factor) and / or coupling coefficient can be adjusted by tuning filter parameters via first resistor 57, second resistor 59, shunt resistors 60, 62, series resistors 64, 66 and / or capacitors 56, 58. The Q factor includes the source / load impedance (R1). As will be relative to... FIG. 11A to FIG. 11C As discussed in detail, the Q factor can be finite and is associated with the coupling coefficient. Adjusting the coupling coefficient using only the first resistor 57 and the second resistor 59, shunt resistors 60, 62, series resistors 64, 66 and / or capacitors 56, 58 may not effectively reduce or remove in-band ripple in the frequency response of the output signal through the resonator 50.

[0063] As shown, a power source can supply current 70 or voltage (e.g., an input signal) to resonator 50. In the depicted embodiment, the power source provides current 70 to first inductor 52. A portion of current 70 can be transferred to second inductor 54 through a transformer effect, thereby inducing current into second inductor 54, as previously described. When current 70 is transferred from first inductor 52 to second inductor 54, current 70 can flow through the coil of second inductor 54 in the same direction or in the opposite direction relative to current 70 flowing through the coil of first inductor 52.

[0064] To illustrate, FIG. 9B Resonator 50 is shown with even mode current. Total current 70 supplied to resonator 50 can flow through first inductor 52 and can include two portions, namely even mode current and odd mode current. As shown, total current 70 through first inductor 52 splits into first even mode current 72A (i / 2) and first odd mode current 74A (i / 2), each having half the magnitude of total current 70. First even mode current 72A results in second even mode current 72B in second inductor 54, which has half the magnitude and flows in the same direction as first even mode current 72A through first inductor 52 (e.g., as shown by current arrows pointing in the same direction). That is, current can flow through the coil of first inductor 52 in a particular direction, and when the current is transferred to second inductor 54, the current can also flow through the coil of second inductor 54 in the same direction.

[0065] Polarity points 75 placed adjacent to the coils can indicate the polarity associated with the respective inductors 52, 54. The direction of current 70 can be determined or referenced relative to polarity points 75. First even mode current 72A can flow into polarity point 75 for first inductor 52 (e.g., primary current through the primary side of a transformer), and second even mode current 72B can also flow into polarity point 75 for second inductor 54 (e.g., secondary current through the secondary side of a transformer). On the other hand, first even mode current 72A can flow through first inductor 52 and out of polarity point 75, and second even mode current 72B can flow through second inductor 54 and out of polarity point 75. In both cases, first even mode current 72A and second even mode current 72B flow through their respective inductors 52, 54 in the same direction.

[0066] In the depicted embodiment, the even-mode current 72A through the first inductor 52 causes an even-mode current 72B to flow through the second inductor 54. As previously described, the even-mode currents 72A, 72B flow in the same direction (both toward the polarity point 75 or both away from the polarity point 75). Because both the first even-mode current 72A and the second even-mode current 72B flow in the same direction, the second even-mode current 72B can provide positive feedback to the first even-mode current 72A (e.g., add an equal and proportional signal in the same direction), resulting in a high gain of the output signal. This amplification can result in greater oscillation between the gain peak associated with the even-mode current and the gain peak associated with the odd-mode current, resulting in greater in-band ripple effects.

[0067] When the current is transferred from the first inductor 52 to the second inductor 54 through the transformer effect, the odd-mode current can flow in opposite directions (based at least in part on the polarity of the inductors 52, 54). Specifically, the first odd-mode current 74A can flow into the polarity point 75 for the first inductor 52, and the second odd-mode current 74B can flow through the second inductor 52 and out of the polarity point 75, or vice versa. That is, the first odd-mode current 74A and the second odd-mode current 74B flow through the first inductor 52 and the second inductor 54 in opposite or different directions relative to the polarity point 75. To illustrate, FIG. 9C The resonator 50 is depicted with odd-mode currents. As shown, a first odd-mode current 74A (i / 2) of the total current 70 supplied to the resonator 50 can flow through the first inductor 52 in a particular direction, and a second odd-mode current 74B (i / 2) can flow through the second inductor 54 in the same direction (e.g., as shown by the current arrows pointing in opposite directions). Specifically, the first odd-mode current 74A causes a second odd-mode current 74B in the second inductor 54 that has half the magnitude and flows in the opposite direction of the first odd-mode current 74A. By way of example, the current can flow through the coil of the first inductor 52 in a particular direction, and when the current is transferred to the second inductor 54, the current can be induced to flow in the opposite direction.

[0068] The even-mode and odd-mode analysis can be performed on the resonator 50 to determine tuning parameters. Although the following discussion and equations describe a symmetric transformer-based resonator such that the capacitor, inductor, and / or resistor of the first RLC circuit 73A is related to the characteristics of the capacitor, inductor, and / or resistor of the second RLC circuit 73B (e.g., C1 = C2, L1 = L2, R1 = R2), which represents a particular embodiment, the capacitor, inductor, and / or resistor on either side can have different or varying characteristics between the first RLC circuit 73A and the second RLC circuit 73B (e.g., C1 ≠ C2, L1 ≠ L2, R1 ≠ R2). That is,FIG. 9A to FIG. 9C and FIG. 11A to FIG. 11C The formulas and circuit descriptions do not necessarily have to correspond to those representing a specific implementation. FIG. 9A to FIG. 9C and FIG. 11A to FIG. 11C The circuit depicted is consistent. Here, the even-mode and odd-mode voltages of the first RLC circuit 73A of the resonator 50, including the first inductor 52, the first capacitor 56, and the first resistor 57, can be described using the following equations:

[0069]

[0070]

[0071] In these equations, V1 corresponds to the input voltage (e.g., the input signal) and V2 corresponds to the output voltage (e.g., the output signal). By way of example, V1, even corresponds to the even-mode input voltage of the first segment, and V2, even corresponds to the even-mode output voltage of the second RLC circuit 73B of the resonator 50, which includes the second inductor 54, the second capacitor 58, and the second resistor 59. As previously described, i / 2 corresponds to the first even-mode current 72A, R1 corresponds to the first resistor 57 (e.g., a real resistor), and C1 corresponds to the first capacitor 56. w corresponds to the frequency, j corresponds to the imaginary unit (e.g., an imaginary resistor, such as the reactance of an inductor or capacitor), and k corresponds to the coupling factor or coefficient. Although the equations described herein are relative to the first RLC circuit 73A of the resonator 50, these equations may also be applied to the corresponding parameters of the second RLC circuit 73B of the resonator 50 circuit.

[0072] By adding even-mode and odd-mode voltages, the input and output voltages can be expressed as:

[0073]

[0074]

[0075] Equations 3 and 4 can be used to determine one or more frequency poles, or one or more gain peaks of the output signal at one or more specific frequencies. Although the following description refers to two frequency poles of the frequency response, such as low-frequency poles and high-frequency poles, the systems, methods, and equations described herein can be used to determine any suitable number of frequency poles (e.g., one, two, four, seven, etc.). As previously stated, a “pole” can refer to a “gain peak,” such as the highest relative gain of the output signal at other frequencies (e.g., the frequency response). These two poles correspond to a first frequency w1 and a second frequency w2, which can be defined as follows:

[0076]

[0077]

[0078] Furthermore, a network quality factor Q can be defined as:

[0079] Q = R1*C1*w0 (Equation 7)

[0080] where w0corresponds to a geometric mean frequency, which is defined as:

[0081]

[0082] As previously mentioned, the coupling coefficient k can indicate a ratio or measure of inductive coupling between the coils of the two inductors. The coupling coefficient is represented as a value between 0 and 1, where 0 indicates no inductive coupling and 1 indicates ideal inductive coupling (e.g., no flux leakage). By way of example, when the coupling coefficient is 0.5 or greater, the two coils can be well coupled. When the coupling coefficient is less than 0.5, then the two coils can be poorly coupled (e.g., more flux or current leakage than expected).

[0083] The gain peaks of the output signal at a particular frequency (e.g., the first frequency pole) and another particular frequency (e.g., the second frequency pole) can vary such that the frequency response of the resonator 50 can exhibit in-band ripple between the gain peaks. The following equation can describe an ideal filter standard to flatten or smooth the ripple to a maximum flat response:

[0084] kQ = 1 (Equation 9)

[0085] That is, to reduce or minimize the in-band ripple effect, the product of the Q factor and the coupling coefficient should be 1 or approximately 1. Changing the value of the resistor (e.g., the first resistor 57) and / or the capacitor (e.g., the first capacitor 56) can adjust the product of the Q factor and / or the coupling coefficient. In some cases, adjusting the Q factor can be performed primarily by adjusting the resistor, as the resonant frequency of the resonator 50 can change with adjustments to the capacitor. By way of example, if the coupling coefficient is 0.5, such that the coils of the first inductor 52 and the second inductor 54 are well coupled, the Q factor can be adjusted to 2 to generate a maximum flat response (e.g., effectively reducing or minimizing in-band ripple). As another example, when the coupling coefficient is 0.5 and the Q factor is greater than 2, the difference between the gain peaks of the in-band ripple can increase. On the other hand, when the Q factor is less than 2, the dual-pole frequency response can degenerate to a single-pole frequency response and thus lose its bandwidth extension (e.g., wideband filter) benefits.

[0086] As previously mentioned, FIG. 9A to FIG. 9CThe shunt resistors 60, 62 and / or series resistors 64, 66 can also adjust filter parameters (e.g., network Q-factor (Q) and / or coupling coefficient (k)) of the resonator 50. Specifically, the resonator 50 implemented with the shunt resistors 60, 62 and / or series resistors 64, 66 can reduce the gain peaking (e.g., decrease the gain) of the output signal at both frequency poles, thereby uniformizing the in-band ripple.

[0087] By way of example, the first frequency pole at a relatively low frequency can correspond to the even-mode current, and the second frequency pole at a relatively high frequency can correspond to the odd-mode current. The frequency pole at the low frequency corresponds to the even-mode current. Specifically, the gain peaking at the low frequency pole can be relatively higher than the gain peaking at the high frequency pole. As previously described, since both the first even-mode current 72A and the second even-mode current 72B flow in the same direction, the second even-mode current 72B can provide positive feedback to the first even-mode current 72A, which results in a high gain of the output signal, and a relatively higher gain peaking corresponds to the frequency pole at the lower frequency. On the other hand, since the first odd-mode current 74A and the second odd-mode current 74B flow in opposite directions, resulting in a relatively lower gain of the output signal, a relatively lower gain peaking corresponds to the frequency pole at the higher frequency.

[0088] To illustrate, FIG. 10 A plot 100 depicting the gain peaking of the output signal at the first frequency pole 110 and the second frequency pole 112 (e.g., a double-pole frequency response) is illustrated. The first curve 102 illustrates the gain peaking of the output signal at the first frequency pole 110 and the second frequency pole 112 without the shunt resistors or series resistors (e.g., the resonator 50 without the shunt resistors 60, 62 and / or series resistors 64, 66). The second curve 104 illustrates the gain peaking of the output signal at the first frequency pole 110 and the second frequency pole 112 with the shunt resistors 60, 62 and / or series resistors 64, 66. FIG. 9A to FIG. 9Cfrequency response of the output signal of the resonator 50 implemented with one or more shunt resistors, such as the first shunt resistor 60 and the second shunt resistor 62. The plot 100 can illustrate the output signal over a frequency range 108 in units of Hertz (Hz) (x-axis) and a corresponding gain 109 in units of decibels (dB) (y-axis) to indicate the frequency response of the output signal of the resonator 50 through the radio frequency filter circuit. The gain 109 indicates the reflection and / or transmission characteristics of the output signal in the frequency domain. The gain 109 can be proportional to the gain of the output signal at a particular frequency, such that the gain value increases as the gain of the output signal increases (e.g., from -8 dB to 2 dB). That is, a high gain peak can be associated with a high gain value (e.g., approximately -2 dB). A low gain value (e.g., approximately -8 dB) can correspond to more reflection or loss of the output signal. Thus, maintaining a high gain at various frequencies and / or frequency poles can be beneficial to transmit the output signal at a desired power level.

[0089] As shown by the first curve 102, the gain peaks at the first frequency pole 110 and the second frequency pole 112 have different gain values, creating in-band ripple between the gain peaks at the respective frequency poles 110, 112. To smooth the ripple, the resonator 50 can be implemented with the series resistors 64, 66. As shown by the second curve 104, adding the series resistors 64, 66 can smooth some of the in-band ripple, such that there is a smaller difference between the respective gain peaks at the first frequency pole 110 and the second frequency pole 112. However, the gain of the overall frequency response is also reduced. That is, by reducing the gain difference between the peaks, the peaks can become relatively more uniform (e.g., as compared to without the series resistors 64, 66), but there is a lower overall gain at each of the peaks at the respective frequency poles 110, 112 and between the peaks. The lower gain peaks correspond to higher reflection of the output signal, such that there is relatively greater loss of the output signal.

[0090] In addition to or alternatively to adding series resistors 64, 66, resonator 50 can be implemented with shunt resistors 60, 62. As shown by third curve 106, shunt resistors 60, 62 can further smooth some of the in-band ripple, such that there is a smaller difference between the respective peak gains at first frequency pole 110 and second frequency pole 112. However, the gain of the overall frequency response (including the frequency poles) is also reduced. That is, by reducing the gain difference between the peaks, the peaks can become relatively more uniform (e.g., as compared to without shunt resistors 60, 62), but with a lower overall gain at each of the respective frequency poles 110, 112. As previously described, the lower gain peaks can indicate a higher reflection of the output signal at the respective frequency poles 110, 112, such that there is a relatively greater output signal loss. Accordingly, shunt resistors 60, 62 and / or series resistors 64, 66 can reduce the in-band ripple effects of the output signal, but can compromise the gain at each of the frequencies, including first frequency pole 110 and second frequency pole 112.

[0091] In some cases, simply adjusting the coupling coefficient can not provide the tuning effect of reducing the uneven gain of the output signal. As such, as previously described, the uneven gain peaks caused by the even mode current and the odd mode current through transformer-based resonator 50 can be difficult to reduce.

[0092] The gain peak at first frequency pole 110 (e.g., the low frequency pole) is associated with the Q factor of the sum of the inductance and the coupled inductance (e.g., the coupled gain peak). On the other hand, the gain peak at second frequency pole 112 (e.g., the high frequency pole) is associated with the leakage inductance Q factor. At higher frequencies, the leakage inductance can have a lower Q factor due to a lower efficiency flux loop. Resonator 50 of the radio frequency filter circuit that causes the frequency response to have uneven gain peaks that create spikes and in-band ripple when electronic device 10 transmits the output signal can result in poor EVM and SNR values. Tuning resonator 50 to address the in-band ripple by tuning capacitors 56, 68 and / or resistors 60, 62 (e.g.,“de-Q” the output signal) and / or adding shunt resistors 60, 62 and / or series resistors 64, 66 to resonator 50 can result in an output signal that has a compromised transmission gain (e.g., is excessively and / or undesirably reduced).

[0093] Transmitting output signals with lower gain can result in the electronic device 10 transmitting a degraded signal due to an increase in reflection loss, which in turn results in a degraded form of wireless communication. In some cases, the gain peak can fall below a predefined threshold for transmitting output signals from the transceiver 30. By way of example, the threshold gain peak can include a gain value or range of values that allows the antenna of the transceiver 30 to transmit the output signal at a predefined power (e.g., low reflection), thereby indicating a reliable or expected quality of wireless communication. That is, if the gain of the output signal at a particular frequency is below this threshold, the electronic device 10 with the radio frequency filter circuit with resonator can not be able to transmit the output signal in an expected manner.

[0094] In addition to or alternatively to adjusting resonator 50 parameters (e.g., by adjusting the Q-factor and / or the coupling coefficient) with capacitors (e.g., first capacitor 56 and second capacitor 58), resistors (e.g., first resistor 57 and / or second resistor 59), and / or shunt and series resistors (e.g., shunt resistors 60, 62 and series resistors 64, 66), resonator 50 can be implemented with a ripple reduction loop that includes a third inductor with an additional resistor. In particular, the ripple reduction loop can be used to adjust the coupling coefficient, rather than the Q-factor, which can be limited.

[0095] To illustrate, FIG. 11A A resonator 51 is depicted in accordance with embodiments of the disclosure that can include the same components as resonator 50 of FIG. 9A and a ripple reduction loop 130 (e.g., a de-Q loop). The ripple reduction loop 130 includes a third inductor 120 (L3) and an additional resistor 122 (R7). The resonator 51 can also include the first inductor 52, the second inductor 54, the first capacitor 56, the second capacitor 58, the first resistor 57, and the second resistor 59. In some embodiments, the resonator 51 can include the first shunt resistor 60, the second shunt resistor 62, the first series resistor 64, and / or the second series resistor 66. In general, the resonator 51 can implement a ripple reduction technique for a wideband filter for a frequency range of 24-48 GHz.

[0096] These components can provide the same or similar respective functions as with respect to FIG. 9A to FIG. 9C the same or similar respective functions as with respect to FIG. 11B and FIG. 11C A resonator 51 is depicted in accordance with embodiments of the disclosure that includes the same respective components as resonator 50 of FIG. 9B and FIG. 9C but with a ripple reduction loop 130 having a third inductor 120 and an additional resistor 122. As FIG. 11BAs shown, the third even-mode current 72C flowing through the third inductor 120 can follow the same direction as the windings in the first inductor 52 and the second inductor 54. Specifically, the first even-mode current 72A through the first inductor 52 can induce the second even-mode current 72B in the second inductor 54 and the third even-mode current 72C in the third inductor 120. The second inductor 54 can also induce the third even-mode current 72C in the third inductor 120. Although not shown, in some embodiments, a portion (e.g., one-third or approximately one-third) of the total current 70 through the first inductor 52 can be diverted into each of the second inductor 54 and the third inductor 120.

[0097] On the other hand, in FIG. 11C As a result, the first odd-mode current 74A and the second odd-mode current 74B do not flow through the additional resistor 122.

[0098] The ripple reduction loop 130 can facilitate matching of the gain peaks of the two frequency poles 110, 112. Specifically, the ripple reduction loop 130 reduces the gain of the first frequency pole 110 (e.g., the low frequency pole) without affecting or minimally affecting the gain of the second frequency pole 112 (e.g., the high frequency pole), which is associated with the leakage inductance Q factor. The ripple reduction loop 130 can also not affect or minimally affect the gain of the output signal at frequencies between the frequency poles 110, 112. That is, the ripple reduction loop 130 can substantially maintain the gain of the output signal (e.g., maintain the gain of the output signal at approximately every frequency except the low frequency pole) while reducing the in-band ripple caused by the frequency poles 110, 112. In some embodiments, the ripple reduction loop 130 can minimally reduce the gain between the first frequency pole 110 and the second frequency pole 112. However, the gain between the first frequency pole 110 and the second frequency pole 112 can already be significantly lower than the poles 110, 112, and thus the ripple reduction loop 130 can not reduce the gain as much as for the gain peaks of the poles 110, 112. Accordingly, the ripple reduction loop 130 can control and facilitate matching (e.g., correlation) of the gain peak of the first frequency pole 110 with the gain peak of the second frequency pole 112, as compared to other filter parameter adjustment methods that can compromise the gain at the peaks of the two frequency poles 110, 112.

[0099] In some implementations, the additional resistor 122 can be a fixed resistor (e.g., providing a single fixed resistance). In other implementations, the additional resistor 122 can be a programmable variable resistor that can provide a variable resistance. In such implementations, the additional resistor 122 can include components (e.g., a controller with a processor, such as the processor 12) to vary the amount of current flowing through the resonator 51. Thus, the ripple reduction loop 130 including the additional resistor 122 can dynamically adjust the gain to provide dynamic ripple reduction. The gain at the second frequency pole 112 can vary, for example, based on factors external to the resonator 50 (e.g., input signals and / or environmental factors). In such cases, the ripple reduction loop 130 can adjust the additional resistor 122 to reduce the gain at the first frequency pole 110 and according to (e.g., related to or approximately matching) the second frequency pole 112. Further, the additional resistor 122 can be programmed to a particular resistance to vary the gain and smooth the frequency response when there are multiple poles (e.g., three or more cascaded poles) that result in in-band ripple. In such cases, the additional resistor 122 can be programmed to have different resistance values based on each of the poles and the difference in gain between the poles.

[0100] FIG. 12 A resonator 51 on a silicon chip is shown. While the following discussion describes a resonator 51 implemented on a PCB representative of a particular implementation, the resonator 51 can instead be implemented on a silicon chip or integrated circuit. As shown, in accordance with implementations of the present disclosure, a first inductor 52 (indicated by the light dot pattern), a second inductor 54 (indicated by the dark dot pattern), and a ripple reduction loop 130 (indicated by no pattern) can be arranged in a stacked architecture on a PCB 55. The first inductor 52, the second inductor 54, and / or the ripple reduction loop 130 can be mounted on the PCB 55 and / or etched (e.g., positioned) onto one or more layers of the PCB 55. Here, the ripple reduction loop 130 is positioned on a first (e.g., lower) layer of the PCB 55. The first inductor 52 is positioned on a second (e.g., higher) layer of the PCB 55, and the second inductor 54 is positioned on a third (e.g., higher than the second) layer of the PCB 55.

[0101] In some implementations, the inductors 52, 54, 120 and / or portions of the inductors 52, 52, 120 can be disposed on separate layers of the PCB 55. For example, a portion of the coil of the third inductor 120 can be positioned on a first layer, while another portion of the coil of the third inductor 120 is positioned on a second or another layer. Further, a portion of the coil of the first inductor 52 can be positioned on a second layer, while another portion of the coil of the first inductor 52 is positioned on a third or another layer. In such implementations, the portions can be coupled with vias 53 such that current flowing through the first inductor 52 can flow between the two layers without interruption. Similarly, the second inductor 54 can also include a portion of its coil on the third layer, while another portion of its coil is positioned on a fourth (e.g., higher than the third) layer or another layer. The second inductor 54 can also include vias 53 to couple the portions together.

[0102] As shown, the ripple reduction loop 130 is a conductive loop (e.g., a metal loop) that includes the third inductor 120 and the additional resistor 122 in series. While describing the ripple reduction loop 130 as a conductive loop is representative of a particular implementation, the ripple reduction loop 130 can additionally or alternatively include one or more metal coils, where portions of its coil are positioned on different layers in the stacked architecture of the resonator 51 as previously described. The first inductor 52 and the second inductor 54 can be symmetrical such that they are made of the same material, have the same thickness, have the same length, have the same size, and / or have the same number of coils. In some implementations, the ripple reduction loop 130 can be relatively thinner than the first inductor 52 and the second inductor 54. In particular, the first inductor 52 can have a first thickness (e.g., a first cross-sectional width or diameter), the second inductor 54 can have a second thickness (e.g., a second cross-sectional width or diameter), and the reduction loop 130 can have a third thickness (e.g., a third cross-sectional width or diameter). The third thickness can be less than the first thickness and less than the second thickness. By way of example, the first inductor 52 and the second inductor 54 can be 2-3 micrometers (pm), and the reduction loop can be 0.1 pm.

[0103] As previously described, the first even mode current 72A flowing through the first inductor 52 can induce the second even mode current 72B to flow through the second inductor 52 in the same direction (e.g., both in the clockwise direction or both in the counterclockwise direction). This positive feedback of the even mode currents 72A, 72B in the same direction can induce the third even mode current 72C in the third inductor 120. Specifically, the first inductor 52 can induce at least a portion of the third even mode current 72C in the third inductor 120, and the second inductor 54 can induce at least a portion of the third even mode current 72C in the third inductor 120. As will be discussed herein, the additional resistor 122 can adjust the parameters of the resonator 51 to change the frequency response of the input signal through the resonator 51. For example, the additional resistor 122 can lower the gain peak of the first frequency pole 110 to correlate to or approximately correlate to the gain peak of the second frequency pole. As previously described, the even mode current through the resonator 50 and / or the resonator 51 can correspond to a low frequency pole, while the odd mode current can correspond to a relatively high frequency pole.

[0104] When the first inductor 52 receives the first odd mode current 74A, the first odd mode current 74A can transfer current, such as the second odd mode current 74B, to the second inductor 54. The second odd mode current 74B is induced in equal magnitude and opposite direction (e.g., clockwise in the first inductor 52 and counterclockwise in the second inductor 54) relative to the first odd mode current 74A. As previously described, the opposite currents can prevent current from being transferred to the third inductor 120 due to canceling each other out. Thus, current can not flow through the additional resistor 122. As such, adjusting the filter parameters (e.g., coupling coefficient) of the resonator 51 via the additional resistor 122 to reduce in-band ripple can affect the even mode current corresponding to the low frequency peak. As previously described, the additional resistor 122 can be a variable resistor or a fixed resistor. As a variable resistor, the additional resistor 122 can be programmed based on a desired ripple reduction effect. The additional resistor 122 can also be programmed to vary during operation, and thus can be dynamically programmed based on operating conditions. Alternatively or additionally, the additional resistor 122 can be set as a fixed resistor based on test simulations during device manufacturing. Specifically, the additional resistor 122 can be fixed to a set resistance for a type and / or model of device that can typically operate in a similar manner during operation.

[0105] For the sake of clarity, FIG. 13A is a schematic diagram showing a cross-sectional view of the resonator 51, and FIG. 13Bis a schematic diagram showing a perspective view of the resonator 51. As shown, the first inductor 52 (indicated by the light dot pattern), the second inductor 54 (indicated by the dark dot pattern), and the ripple reduction loop 130 (indicated by no pattern) including the third inductor 120 with the additional resistor 122 can be arranged in a stacked architecture on the PCB 55 (not shown). The first inductor 52, the second inductor 54, and / or the ripple reduction loop 130 can be mounted on the PCB 55 and / or etched (e.g., positioned) onto one or more layers of the PCB 55. The ripple reduction loop 130 is positioned on a first layer 132A (e.g., a lower layer) of the PCB 55. The first inductor 52 is positioned on a second layer 132B (e.g., higher than the first layer) of the PCB 55, and the second inductor 54 is positioned on a third layer 132C (e.g., higher than the second layer) of the PCB 55. In some cases, and as previously discussed, a portion of the first inductor 52, the second inductor 54, and / or the third inductor 120 of the ripple reduction loop 130 can be on one or more layers. By way of example, a portion of the second inductor 54 can be disposed on the third layer 132C, while another portion of the second inductor 54 is disposed on a fourth layer 132D (e.g., higher than the third layer 132C), with the portions connected by a via 53. The architecture and functionality of the resonator 51 can be implemented as previously discussed.

[0106] FIG. 14 According to embodiments of the present disclosure, a plot 200 is depicted that illustrates a frequency response of an output signal through an operating region of the resonator 51. A first plot 102 illustrates a frequency response of an output signal of the resonator 50 without the ripple reduction loop 130. A second plot 202 illustrates a frequency response of an output signal of the resonator 51 with the ripple reduction loop 130 implemented. As discussed with respect to FIG. 12 the ripple reduction loop 130 can smooth the gain of the frequency response over the operating region, including the gain peaks at the first frequency pole 110 (e.g., a low frequency pole) and the second frequency pole 112 (e.g., a high frequency pole), and the gain of the output signal at frequencies between the low frequency pole and the high frequency pole. The ripple reduction loop 130 can smooth the gain of the frequency response over the operating region, for example, by relating the gain peak at the low frequency pole to the high frequency pole with the additional resistor 122.

[0107] As shown, the first curve 102 illustrates a stark difference between the gain peaks of the first frequency pole 110 and the second frequency pole 112. The difference between the peaks results in a 2 dB in-band ripple (e.g., drop between the peaks). However, due to the ripple reduction loop 130 of the resonator 51, the difference between the peaks is reduced in the second curve 202. Specifically, the ripple reduction loop smooths the frequency response over the operating region of the resonator 51 by matching the gain peak of the first frequency pole 110 to the gain peak of the second frequency pole 112, such that the difference results in a 0.8 dB in-band ripple. As such, the systems and methods described herein of the resonator 51 having the ripple reduction loop 130 can facilitate smoothing the frequency response of the output signal through the resonator 51 while minimizing gain loss.

[0108] The technology described and claimed herein is to be understood fully as being directed to the specific examples set forth herein, which examples represent the fullness of the state of the art to the best of our knowledge. The technology described and claimed herein also is to be understood fully as being directed to the abstractly stated concept of the technology, which concept represents the fullness of the state of the art to the best of our knowledge. The technology described and claimed herein is to be understood fully as being directed to the specific examples set forth herein, which examples represent the fullness of the state of the art to the best of our knowledge, and which are not abstract, intangible or purely theoretical. Furthermore, if any of the claims appended to this specification contain one or more dependent claims followed by a comma and the words "means for" or "steps for", then it is the intent of the claimant(s) that those dependent claims be interpreted under 35 U.S.C. 112(f) rather than 112 (6). To the extent that interpretation of any one of the claims appended to this specification differs from the interpretation of the same claim by the US Patent and Trademark Office, then the claimant(s) will insist on the interpretation of the claim as set forth above.

Claims

1. A radio frequency filter circuit, comprising: a first inductor configured to receive a first current; a second inductor configured to be inductively coupled to the first inductor based on the first current, the first current inducing a second current in the second inductor; a conductive loop configured to be inductively coupled to at least one of the first inductor or the second inductor, the at least one of the first inductor or the second inductor inducing a third current in the conductive loop, the conductive loop further configured to adjust the third current to reduce a first gain peak of an output signal such that the first gain peak of the output signal is related to a second gain peak of the output signal.

2. The radio frequency filter circuit of claim 1, wherein the conductive loop comprises a third inductor and a resistor.

3. The radio frequency filter circuit of claim 2, wherein the resistor comprises a programmable resistor or a fixed resistor.

4. The radio frequency filter circuit of claim 1, wherein the first current comprises an even mode current.

5. The radio frequency filter circuit of claim 4, wherein the first current, the second current, and the third current travel in a same direction in response to the even mode current.

6. The radio frequency filter circuit of claim 1, wherein the first gain peak corresponds to a first frequency pole associated with an even mode current, and wherein the second gain peak corresponds to a second frequency pole associated with an odd mode current.

7. The radio frequency filter circuit of claim 1, wherein the radio frequency filter circuit is configured to pass frequencies within a wideband range of 24 gigahertz (GHz) to 48 GHz.

8. The radio frequency filter circuit of claim 1, wherein adjusting the third current comprises adjusting a coupling factor between the first inductor and the second inductor.

9. The radio frequency filter circuit of claim 1, comprising at least one of one or more capacitors, one or more shunt resistors, or one or more series resistors.

10. The radio frequency filter circuit of claim 9, wherein the at least one of the one or more capacitors, the one or more shunt resistors, or the one or more series resistors is configured to adjust a network quality factor associated with the radio frequency filter circuit.

11. The radio frequency filter circuit of claim 1, wherein the first current comprises a first even mode current and a first odd mode current through the first inductor, wherein the second current comprises a second even mode current and a second odd mode current through the second inductor, wherein the first even mode current through the first inductor and the second even mode current through the second inductor travel in a same direction, wherein the first odd mode current through the first inductor and the second odd mode current through the second inductor travel in opposite directions, wherein the first even mode current traveling through the first inductor, the second even mode current traveling through the second inductor, or both induce the third current in the conductive loop.

12. An electronic device having a radio frequency filter circuit, comprising: a current source configured to provide a current; a first coil coupled to the current source and configured to generate a first even mode current and a first odd mode current in the first coil based on the current received from the current source; a second coil configured to: conduct a second even mode current induced by the first even mode current flowing through the first coil, and the second even mode current flowing through the second coil in a same direction, and conduct a second odd mode current induced by the first odd mode current flowing through the first coil, and the second odd mode current flowing through the second coil in an opposite direction; a conductive loop configured to conduct an induced current induced by the first even mode current traveling through the first coil and the second even mode current traveling through the second coil; and a resistor coupled to the conductive loop and configured to adjust the induced current to reduce a first gain peak of a frequency response of the radio frequency filter circuit for an output signal such that the first gain peak of the frequency response is related to a second gain peak of the frequency response.

13. The electronic device of claim 12, wherein: the first coil is disposed on a first layer of a printed circuit board of the electronic device; the second coil is disposed on a second layer of the printed circuit board; and the conductive loop is disposed on at least one of the first layer, the second layer, or a third layer of the printed circuit board.

14. The electronic device of claim 12, wherein the first odd mode current traveling through the first coil and the second odd mode current traveling through the second coil do not generate the induced current in the conductive loop.

15. The electronic device of claim 12, wherein the first gain peak is associated with the first even mode current and the second even mode current, and wherein the second gain peak is associated with the first odd mode current and the second odd mode current.

16. The electronic device of claim 12, wherein the radio frequency filter circuit comprises a second resistor, a third resistor, or both, wherein the second resistor comprises a shunt resistor coupled to the current source of the electronic device, and wherein the third resistor comprises a series resistor coupled to a capacitor of the radio frequency filter circuit.

17. The electronic device of claim 12, wherein the radio frequency filter circuit comprises a first capacitor coupled to the first coil and a second capacitor coupled to the second coil, wherein the radio frequency filter circuit is configured to pass frequencies within a wideband range of 24 to 48 gigahertz (GHz).

18. The electronic device of claim 12, wherein the resistor comprises a programmable resistor or a fixed resistor.

19. A transformer-based resonator, comprising: a first inductor configured to transmit a first even mode current and a first odd mode current when a current is supplied to the first inductor; a second inductor configured to transmit a second even mode current induced by the first even mode current and to conduct a second odd mode current induced by the first odd mode current, the second even mode current traveling in a same direction as the first even mode current, the second odd mode current traveling in an opposite direction as the first odd mode current; a third inductor configured to transmit an induced current induced by the first even mode current traveling through the first inductor and the second even mode current traveling through the second inductor; and a variable resistor configured to adjust a coupling factor between the first inductor and the second inductor to reduce an in-band ripple between a first gain peak of a frequency response of the transformer-based resonator and a second gain peak of the frequency response of the transformer-based resonator.

20. The transformer-based resonator of claim 19, wherein the first gain peak is associated with a coupling inductance, and wherein the second gain peak is associated with a leakage inductance. ​

Images