Self-adjusting filter

Abstract

Filter circuit comprising a main filter section (210) with at least one passive element (212, 214) configured to receive an input signal and provide a filtered output signal, a tuning feedback section (250) configured to receive the filtered output signal and provide a feedback signal to the main filter section (210), and an adjustable section (230) with at least one controllable part (232A, 232B) coupled in parallel with the at least one passive element (212, 214) of the main filter section (210), wherein the controllable part (232A, 232B) is adjustable based on the feedback signal from the tuning feedback section (250) such that the filter circuit (200) provides a tuned filtered output signal output by the main filter section (210).wherein the tuning feedback section (250) comprises at least one amplifier element (252) configured to receive the filtered output signal, a resistive element (254) coupled in series with the at least one amplifier element (252), a capacitive element (256) wherein a node of the capacitive element (256) is coupled to a node of the resistive element (254), and a second adjustable section (230) coupled in parallel with the capacitive element (256).

Description

The invention relates to a self-tuning filter, an electronic device with a filter circuit and a method in which at least one section of a filter is adjusted. Numerous types of electronic circuits and devices employ filters. For example, circuits for sending and receiving communication signals typically incorporate various types of filters, such as low-pass, high-pass, and band-pass filters. Such communication circuits can be used in a wide variety of devices and applications, including telephones, televisions, wireless computing devices, audio equipment, personal digital assistants (PDAs), and other systems that transmit or receive signals. Besides communication circuits, numerous other types of electrical circuits also incorporate filters. The performance characteristics of a filter during operation can vary depending on several factors. For a conventional low-pass filter, which consists of a combination of several elements, such as operational amplifiers, capacitors, resistors, and the like, the filter's cutoff frequency can fluctuate considerably during operation, for example, depending on the signal processing load and variations in environmental parameters, such as temperature fluctuations, in the filter's environment. A conventional approach to dealing with such operational variations is to design the other components of the electrical circuit to tolerate a shift in the filter's performance characteristic. Another approach is to use a separate reference circuit to measure the filter's performance characteristic and then selectively switch resistive or capacitive elements on or off to adjust the filter's performance characteristic as needed. Such conventional approaches are not ideal. In particular, they may ignore certain side effects that can lead to other inaccuracies in operation. US Patent 2006 / 0267698A1 discloses devices and methods for filter calibration. A filter circuit comprises several capacitors with adjustable capacitances. An output of the filter circuit is coupled to an input of the filter circuit via a switch. A filter component acts as an oscillator and is adjusted to achieve a desired filter characteristic. DE 692 23 218 T2 discloses a calibration circuit for a continuous-time analog filter. The filter comprises resistors, an operational amplifier, and calibration capacitor sections, each containing capacitors and switches. US 4 516 312 A discloses delay circuits that include several inverters and an RC network. US 2006 / 0132212A1 discloses an adjustable delay circuit comprising capacitors and switches connected in series with the capacitors. There is a need for new devices and methods that mitigate the effects of filter operating fluctuations. In particular, there is a need for such devices and methods that offer improvements with regard to the undesirable effects of conventional approaches. A filter circuit, an electronic device, and a method are disclosed as defined in the independent claims. The dependent claims define advantageous or preferred embodiments. A filter circuit is specified according to one aspect. The filter circuit comprises a main filter section, or primary filter section, with at least one passive element, a tuning feedback section, and an adjustable section with at least one controllable part. The main filter section is configured to receive an input signal and provide a filtered output signal. The tuning feedback section is connected to receive the filtered output signal and provide a feedback signal to the main filter section. The adjustable section is coupled in parallel with the at least one passive element, the controllable part being adjustable based on the feedback signal from the tuning feedback section, so that the filter circuit provides a set filtered output signal from the main filter section.The tuning feedback section comprises at least one amplifier element configured to receive the filtered output signal, a resistive element coupled in series with the at least one amplifier element, a capacitive element wherein a node of the capacitive element is coupled to a node of the resistive element, and a second adjustable section coupled in parallel with the capacitive element. Following a further aspect, a procedure is described. This procedure comprises the steps of receiving a signal at a main filter section of a filter circuit, filtering the signal with the main filter section, receiving a filtered output signal from the main filter section at a second filter section, and determining whether the filtered output signal meets an acceptance criterion. The acceptance criterion is a suitably chosen criterion that must be met for the signal to be considered acceptable.If the filtered output signal does not meet the acceptance criterion, the filtered output signal is analyzed to determine an appropriate setting. A feedback signal indicating the determined setting is provided to the main filter section, and at least one section of the main filter section is adjusted based on the feedback signal to at least partially improve the acceptability of the filtered output signal. The second filter section comprises at least one amplifier element configured to receive the filtered output signal, a resistive element coupled in series with the at least one amplifier element, a capacitive element with one node of the capacitive element coupled to a node of the resistive element, and a second adjustable section coupled in parallel with the capacitive element. The devices and methods are generally applicable to systems that include a filter, for example in communication devices for sending and / or receiving signals, and are not limited to this application. Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying drawing. Fig. 1 shows an exemplary environment in which devices and methods according to one embodiment can be used. Fig. 2 is a circuit diagram of a self-tuning filter circuit according to one embodiment. Figs. 3 and 4 show controllable elements of adjustable sections of the self-tuning filter circuit of Fig. 2. Figs. 5 and 6 show exemplary correlation data tables that were determined using a conventional simulation tool. Fig. 7 is a flowchart representation of a self-tuning filter method according to one embodiment. In the figures, similar reference symbols denote similar elements and arrangements. The first digit in each of the three-digit reference symbols refers to the figure in which the referenced element or arrangement first appears. The following describes measures for self-tuning filters that correct or account for fluctuations in performance characteristics due to operating conditions. Generally, the filter itself can be used as a reference for tuning. This allows for the appropriate consideration of side effects. Such measures can mitigate fluctuations in the filter's performance characteristics during operation, while also offering improvements with regard to undesirable effects of conventional approaches. A self-tuning filter and a filtering method can include an additional circuit or circuit section that is tuned to or adapted to the passive elements of the filter. During operation, the filter's natural frequencies are measured, and these measured frequencies provide information about the filter's performance characteristics, such as its cutoff frequency. In one embodiment, the filter's natural frequency or oscillation can be measured digitally. During a tuning process, the filter is exposed to parasitic effects that include a target oscillation frequency. This target oscillation frequency represents the filter's cutoff frequency during operation.By using the filter itself as a reference for tuning, fluctuations in the filter's performance characteristics during operation can be mitigated, and appropriate adjustments can be made for undesirable side effects. In one embodiment, a self-tuning filter circuit comprises a main filter section, or primary filter section, and a tuning feedback section. The main filter section has at least one passive element and is configured to receive an input signal and output a filtered signal. The tuning feedback section receives the filtered output signal and provides feedback to the main filter section. An adjustable section has a controllable part, i.e., a controllable circuit segment, which is coupled in parallel with the at least one passive element of the main filter section. During operation, the controllable part of the adjustable section is adjusted based on the feedback signal from the tuning feedback section.Thus, the filtered output signal is adjusted to provide the desired filtered output signal, using the feedback signal from the tuning feedback section of the circuit. According to a further embodiment, a method comprises receiving a signal at a main filter section of a filter circuit and filtering the signal using the main filter section. A filtered output signal from the main filter section is received at a second filter section, and it is determined whether the filtered output signal meets an acceptance criterion. If the filtered output signal does not meet the acceptance criterion, the method comprises analyzing the filtered output signal to determine a corresponding, correlating setting, providing a feedback signal to the main filter section that is characteristic of the corresponding setting, and adjusting at least one section of the main filter section based on the feedback signal to at least partially improve the fulfillment of the acceptance criterion by the filtered output signal. The measures described here can be implemented in various ways. An exemplary environment is described below with reference to the figures. Fig. 1 shows an exemplary environment 100 in which devices and methods according to the invention can be used. The exemplary environment 100 comprises a communication device 110 with one or more filters 150, configured according to an embodiment of the present invention. The communication device 110 is in communication connection with a plurality of other communication devices 142 via one or more networks 140. In the exemplary environment 100, the communication device 110 is a handheld device, for example a mobile phone, a personal digital assistant (PDA), a global positioning system (GPS) unit, or another similar handheld device.The other communication devices 142 can, for example, include a computer 142A, another handheld device 142B, a ground-mounted communication station 142C, a communication device 142D installed in a vehicle (e.g., a radio, a navigation unit, television, or the like), and a satellite 142E. The communication devices 110, 142 can, of course, also include other suitable devices. Furthermore, each device of the plurality of communication devices 142 can be equipped with a filter 150 or filters 150 configured according to an embodiment of the invention. The communication device 110 of Fig. 1 comprises one or more processors 112 and one or more input / output components (I / O components) 114, for example, a keyboard, a mouse, a transmitter, a receiver, and the like, which are coupled to a system memory 120 via a bus 116. In the embodiment shown in Fig. 1, the I / O component 114 of the communication device 110 comprises the filter 150. Alternatively or additionally, the filter 150 can be integrated into another suitable section of the device 110, or the filter 150 can be a separate, individual component of the device 110. The system bus 116 of the communication device 110 represents any bus structure from several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor bus or local bus, which can use any bus architecture from a variety of bus architectures. The EA component 114 can be configured for communication with one or more external networks 140, such as a mobile phone network, a satellite network, an information network (for example, the Internet, an intranet, a cellular network, a cable network, a fiber optic network, a local area network (LAN), a wide area network (WAN), or the like), or any other suitable network. The system memory 120 can comprise computer-readable media configured to store data and / or program modules for implementing the methods and actions described herein, which the processor 112 can directly access and / or on which the processor 112 is currently operating. For example, the system memory 120 can store a BIOS (Basic Input / Output System) 122, an operating system 124, an application program or several application programs 126, and program data 128, which the processor 112 can access to perform various tasks requested by a user of the communication device 110. The computer-readable media included in the system memory 120 can be any media accessible to the device 110, including computer storage media and communication media. Computer storage media can be volatile or non-volatile, and removable or non-removable. They can be implemented using any method or technology for storing information, such as computer-readable instructions, data structures, program modules, or other data.Computer storage media include, but are not limited to, random access memory (RAM), read only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other storage technology, CD-ROM, DVD or other optical storage disc, magnetic cartridges, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium, including paper, punched cards and the like, that can be used to store the desired information and that the communication device 110 can access. Communication media typically comprise computer-readable instructions, data structures, program modules, or other data contained within a modulated data signal, such as a carrier wave or other transport mechanism, and include any information transmission medium. The term "modulated data signal" refers to a signal in which one or more signal properties are fixed or modified in such a way as to encode information within the signal. For example, communication media include wired media, such as a wired network or a direct-wired connection, and wireless media, such as acoustic, radio frequency, infrared, and other wireless media. Computer-readable media also include any combination of the aforementioned media. In general, program modules executed on the device 110 of Fig. 1 can comprise routines, programs, objects, components, data structures, and the like for performing specific tasks or realizing certain abstract data types. These program modules and the like can be executed as machine code or can be downloaded and executed, for example, in a virtual machine or in other execution environments using just-in-time (JIT) compilation. Typically, the functionality of the program modules can be combined or distributed as desired in the various implementations. Although the exemplary environment 100 in Fig. 1 is depicted as a communication network, this is only a non-limiting example of a suitable environment in which the filter 150 can be used according to one embodiment. Similarly, the communication device 110 is only a non-limiting example of a suitable device that can use one or more filters 150 according to one embodiment. Next, the structure and function of a self-tuning filter circuit will be described in more detail. Fig. 2 shows a self-tuning filter circuit 200, which can be used in the exemplary environment 100 as the filter 150 of Fig. 1. The circuit 200 comprises a main filter section 210, a tuning feedback section 250, and a plurality of adjustable sections 230 coupled to the main filter section 210 and the tuning feedback section 250. The main filter section 210 is a primary section for filtering signals. The main filter section 210 of Fig. 2 comprises a plurality of passive elements, which in Fig. 2 include a pair of resistive elements 212 and a pair of capacitive elements 214 coupled to an operational amplifier 216. In the illustrated filter circuit 200, the configuration of the main filter section 210 is of the type generally known as a second-order Butterworth filter. In other embodiments, however, the main filter section 210 can be configured as another suitable type of filter, for example, as a first- or nth-order Butterworth filter, a Chebyshev filter, a Bessel filter, a Gaussian filter, or any other suitable type of filter. As shown in Fig. 2, an adjustable section 230 is coupled in parallel to each of the capacitive elements 214 of the main filter section 210. Each adjustable section 230 comprises a plurality of controllable parts 232. Here, a "controllable part" generally refers to a controllable section or segment of a circuit. Although in Fig. 2 the adjustable sections 230 are shown to have three controllable parts 232, in alternative embodiments the adjustable sections 230 can have any suitable number of controllable parts 232, for example, one controllable part or a plurality of controllable parts. Furthermore, the adjustable sections 230 need not have the same number of controllable parts 232. Rather, one adjustable section 230 can have a greater number of controllable parts 232 than another adjustable section.In further embodiments, the adjustable sections 230 can be coupled in a parallel circuit with other elements of the main filter section 210, such as the resistor elements 212. Figures 3 and 4 show enlarged views of realizations of the controllable parts 232 of the adjustable sections 230 of Figure 2. In particular, the controllable part 232A of Figure 3 has a pair of switches 234 coupled in series with a capacitor 236, while the controllable part 232B of Figure 4 has a switch 234 coupled in series with a capacitor 236. In some embodiments, the controllable parts 232 can exhibit strictly monotonic behavior. The controllable parts 232 can also be configured differently. For example, the controllable parts 232 can be configured using resistive elements, inductive elements, or other suitable controllable elements. In further embodiments, the controllable parts 232 can comprise one or more binary-weighted elements, such as resistors, capacitors, current sources, thermometer-coded elements, and the like, wherein the value of the one or more binary-weighted elements can be controlled via an input value. The input value for such binary-weighted elements can be variably controlled based on the operating conditions of the self-tuning filter circuit, for example, based on temperature conditions, signal processing loads, or other suitable conditions. As can be seen in Fig. 2, the adjustable sections 230 are coupled in parallel with the capacitors 214 or other passive elements of the main filter section 210. By actuating the switches 234, the controllable parts 232 are adjusted in a controlled or controllable manner to accommodate fluctuations in the performance characteristics of the main filter section 210. In some embodiments, the adjustable sections 230 can affect only the capacitive elements 214, while the resistive elements 212 are essentially bypassed to reduce or minimize possible parasitic effects due to the switches 234. In one embodiment, a nominal capacitance, or more generally a nominal state, can exist when only a portion of the switches 234, in particular approximately half of the switches 234, of the controllable parts 232 are closed.Thus, settings of the adjustable sections 230 can be achieved starting from the nominal capacity by closing or opening switches 234 of the controllable parts 232. The tuning feedback section 250 comprises a plurality of inverters 252 and a resistive element 254, which are coupled in series with an output of the main filter section 210. A capacitive element 256 is coupled in parallel with the other elements 252 and 254 of the tuning feedback section 250. Another adjustable section 230 is coupled in parallel with the capacitive element 256. The tuning feedback section 250 forms a second or secondary filter that receives output signals from the main filter section 210, which serves as the primary filter section. A feedback line 258 feeds the output signal of the tuning feedback section 250 back to the main filter section 210. The feedback need not be direct but can be provided via one or more elements between the output of the tuning feedback section 250 and the main filter section. In one embodiment, the cutoff frequency of the tuning feedback section 250 can be approximately equal to the cutoff frequency of the main filter section 210, so that the tuning feedback section 250 is approximately matched to, or tuned to, the main filter section 210.In alternative embodiments, however, the tuning feedback section 250 can have a cutoff frequency that is slightly higher than the cutoff frequency of the main filter section 210. In some embodiments, “static” capacitive elements that are not intended to be switched on and off can advantageously be equipped with a dummy switch to improve the matching of the main filter section 210 and the tuning feedback section 250. In an untuned state, the self-tuning filter circuit 200 may have an inherent natural frequency of, for example, 1 MHz. If parameters of the circuit 200 are changed by a technical process, the frequency response of the circuit 200 may change. For example, it may drop to a lower frequency of, for example, 900 kHz. During operation, the adjustable sections 230 can be controlled by actuating the controllable parts 232 to achieve the desired performance characteristic, for example, a frequency response of 1 MHz. If the desired performance characteristic of the main filter section 210 is achieved or is regained, then the tuning feedback section 250 can be decoupled, or it can otherwise be prevented from further influencing the main filter section 210. Relationships or correlations between the observed performance characteristics of the main filter section 210 and the configuration of the circuit 200, which are suitable for adjusting the performance characteristics to a desired or target level, can be determined in advance, for example, using computer simulations. Alternatively, the relationships can be determined experimentally, analytically, empirically, or using another suitable method. Figures 5 and 6 show exemplary tables of correlation data 300 and 350, which were determined using a conventional simulation tool to model the self-tuning filter circuit 200 of Figure 2. The correlation data 300 in Figure 5 were generated assuming that the resistive elements have a relative value of 1.3, while the correlation data 350 in Figure 6 were generated assuming that the resistive elements have a relative value of 0.7. The cutoff frequencies are given in the middle columns 302 and 352 of Figures 5 and 6, and the oscillation frequencies of the tuning feedback section 250 in closed-loop operation and in the "tuning" operating mode, respectively, are shown in the right-hand columns 304 and 354. For the exemplary correlation data 300, 350 shown in Figs. 5 and 6, it was assumed that the target operating frequency of the self-tuning filter circuit was 200–700 kHz, and the resistance values ​​of the resistor elements were changed by +30% and -30%, respectively. Furthermore, for the simulations shown in Figs. 5 and 6, it was assumed that the capacitive elements of the adjustable sections 230 are adjustable in four linear steps in the positive and negative directions. This can be achieved by appropriately changing the number of open or closed switches (“s”). During operation, the correlation data 300 and 350 can be used to adjust the adjustable sections 230 based on the actual operating performance characteristics of the circuit 200, in order to achieve the desired operating performance characteristics. By adjusting the right-hand columns 304 and 354 via the adjustable sections using the capacitive elements, achieved by appropriately controlling the controllable parts, a setting is obtained that ensures the actual operating performance characteristics of the circuit 200 are adapted to the desired operating performance characteristics. The following describes methods for self-tuning filter circuits according to various embodiments. While specific embodiments are described by way of example, depending on the circumstances, certain steps may be performed in a different order than described, may be modified, and / or certain steps may be omitted entirely. The various steps can be executed by a computer, a processor, or other computing device based on instructions stored on one or more computer-readable media. The computer-readable media can be any available media that a computing device can access to execute the instructions stored therein. Fig. 7 is a flowchart representation of a self-tuning filter method 400 according to an exemplary embodiment. The method 400 is represented as a plurality of blocks in a logical flowchart, which represent a sequence of operations or workflows that can be implemented by hardware, software, or a combination thereof. In the context of software, the blocks represent computer instructions which, when executed by one or more processors, perform the respective operations. For illustrative purposes only, the method will be described in more detail with reference to the components of the environment 100 and the circuit 200, which were described above with reference to Figs. 1-4. Method 400 comprises filtering an input signal using a main filter section of a filter circuit at 402. At 404, an output signal of the main filter section is sampled with a tuning feedback section, and at 406, it is determined whether the output signal is acceptable. For example, the output signal can be analyzed to determine whether it is at a desired operating value or within a desired operating range. This check represents an example of an acceptance criterion check. If step 406 determines that the output signal is acceptable, then step 400 determines at step 408 whether the tuning feedback section can be decoupled from the main filter section. If so, the tuning feedback section is decoupled at step 410. Step 400 then returns to step 404 to perform sampling and repeats the other steps from 404 to 408 mentioned above. However, if at 406 it is determined that the output signal is unacceptable, then at 412 the sampled output signal is fed back to determine the settings necessary to correct the output signal to the desired value. At 414, the method 400 analyzes the sampled output signal and determines a configuration of the circuit required to adjust the output signal to an acceptable level. For example, the method 400 can use a signal processing component, such as the processor 112 of Fig. 1, to determine how many and which switches of the adjustable sections should be opened or closed to adjust the output signal as desired to achieve the acceptable output signal.Alternatively, the filter in which the self-tuning filter circuit is arranged may include signal processing components or programmable logic components that perform the analysis and determination at step 414. In further embodiments, the method 400 described in 414 can determine other types of settings required in the configuration of the self-tuning circuit to provide the acceptable output signal. The analysis and determination described in 414 may, for example, involve performing a table search, accessing simulation results, accessing information derived analytically, experimentally, or empirically, or using other suitable methods to determine the necessary circuit settings required to provide an acceptable output signal. At 416, the circuit settings required to provide the acceptable output signal are made. For example, the settings may involve actuating one or more switches in the adjustable sections of the circuit. In other embodiments, the circuit may be configured in a different way. After the desired settings have been configured, procedure 400 at 418 determines whether the filtering is complete. If not, procedure 400 returns to sampling at 404, and the steps described above are repeated until the filtering is complete. When the filtering is complete, procedure 400 terminates at 420 or continues with other steps. The devices and methods according to exemplary embodiments of the invention offer advantages over the prior art. For example, tuning is possible without time-consuming external measurements, and no independent external reference elements are required. Instead, the main filter section becomes part of the measurement and tuning loop. Parasitic effects, such as the capacitance of resistive elements, which can vary depending on the composition of the resistive element, for example, the substrate material, as well as delays and cutoff frequencies of operational amplifiers, are also adequately taken into account. While specific embodiments and specific areas of application have been described here, the present invention is not limited to these. For example, the features of different embodiments can be combined with one another.

Claims

Filter circuit comprising a main filter section (210) with at least one passive element (212, 214) configured to receive an input signal and provide a filtered output signal, a tuning feedback section (250) configured to receive the filtered output signal and provide a feedback signal to the main filter section (210), and an adjustable section (230) with at least one controllable part (232A, 232B) coupled in parallel with the at least one passive element (212, 214) of the main filter section (210), wherein the controllable part (232A, 232B) is adjustable based on the feedback signal from the tuning feedback section (250) such that the filter circuit (200) provides a set filtered output signal output by the main filter section (210).wherein the tuning feedback section (250) comprises at least one amplifier element (252) configured to receive the filtered output signal, a resistive element (254) coupled in series with the at least one amplifier element (252), a capacitive element (256) wherein a node of the capacitive element (256) is coupled to a node of the resistive element (254), and a second adjustable section (230) coupled in parallel with the capacitive element (256). Filter circuit according to claim 1, wherein the at least one passive element comprises a capacitive element (214), wherein the main filter section (210) comprises at least one resistive element (212) and at least one operational amplifier (216) coupled to the capacitive element (214). Filter circuit according to claim 2, wherein the at least one resistive element (212) and the at least one operational amplifier (216) are configured with the capacitive element (214) as a Butterworth filter. Filter circuit according to one of the preceding claims, wherein the adjustable section (230) comprises a plurality of controllable parts (232A, 232B) which are coupled in a parallel circuit with the passive element (212, 214). Filter circuit according to claim 4, wherein each part of the plurality of controllable parts (232A, 232B) comprises a capacitor (236) and a controllable switch (234). Filter circuit according to one of the preceding claims, wherein the second adjustable section (230) comprises a plurality of controllable parts (232B) coupled in a parallel circuit with the capacitive element (256) of the tuning feedback section (250), wherein each part of the plurality of controllable parts (232B) comprises a capacitor (234) and a controllable switch (236). Electronic device comprising a processor (112), a communication assembly coupled to the processor (112) and configured to receive input signals and send output signals, and a filter circuit (150) coupled to the communication assembly and configured to perform desired filtering of at least one of the input signals and the output signals, wherein the filter circuit (150) comprises: a main filter section (210) with at least one passive element (212, 214) configured to receive an input signal and provide a filtered output signal, a tuning feedback section (250) configured to receive the filtered output signal and provide a feedback signal to the main filter section (210), and an adjustable section (230) with at least one controllable part (232A, 232B).which is coupled in a parallel circuit with the at least one passive element (212, 214) of the main filter section (210), wherein the controllable part (232A, 232B) can be controlled based on the feedback signal from the tuning feedback section (250), wherein the tuning feedback section (250) comprises at least one amplifier element (252) configured to receive the filtered output signal, a resistive element (254) coupled in a series circuit with the at least one amplifier element (252), a capacitive element (256) wherein a node of the capacitive element (256) is coupled to a node of the resistive element (254), and a second adjustable section (230) coupled in a parallel circuit with the capacitive element (256). Electronic device according to claim 7, wherein the at least one passive element comprises a capacitive element (214), wherein the main filter section (210) comprises at least one resistive element (212) and at least one operational amplifier (216) coupled to the capacitive element (214). Electronic device according to claim 7, wherein the adjustable section (230) comprises a plurality of controllable parts (232A, 232B) coupled in a parallel circuit with the passive element (212, 214). Electronic device according to one of claims 7-9, wherein the filter circuit (150) is configured such that during operation the controllable part (232A, 232B) of the adjustable section (230) is controlled by the processor (112) based on the feedback signal. Electronic device according to one of claims 7-10, wherein the second controllable part (232B) of the tuning feedback section (250) is controllably adjusted by the processor (112) such that the tuning feedback section (250) has a cutoff frequency that is equal to or greater than the cutoff frequency of the main filter section (210). Electronic device according to one of claims 7-11, wherein the filter circuit is configured as a filter circuit (200) according to one of claims 1-6. A method comprising: receiving a signal at a main filter section (210) of a filter circuit (200), filtering the signal with the main filter section (200), receiving a filtered output signal from the main filter section (210) at a second filter section (250), the second filter section (250) comprising at least one amplifier element (252) configured to receive the filtered output signal, a resistive element (254) coupled in series with the at least one amplifier element (252), a capacitive element (256) wherein a node of the capacitive element (256) is coupled to a node of the resistive element (254), and an adjustable section (230) coupled in parallel with the capacitive element (256), determining whether the filtered output signal satisfies an acceptance criterion, and, if the filtered output signal does not, Acceptance criterion not met,Perform the following steps: Analyze the filtered output signal to determine an appropriate setting, provide a feedback signal to the main filter section (210) that is characteristic of the appropriate setting, and adjust at least one section (230) of the main filter section (210) based on the feedback signal so that the filtered output signal at least partially better meets the acceptance criterion. Method according to claim 13, wherein adjusting at least one section of the main filter section (210) comprises adjusting an adjustable section (230) which is coupled in a parallel circuit with a passive element (212, 214) of the main filter section (210), wherein the passive element (212, 214) comprises at least one of a capacitive element (214) and a resistive element (212). Method according to claim 14, wherein adjusting an adjustable section (230) comprises adjusting at least one of a plurality of controllable parts (232A, 232B) coupled in a parallel circuit with the passive element (212, 214), wherein each part of the plurality of controllable parts (232A, 232B) comprises a capacitor (236) and a controllable switch (234). Method according to one of claims 13-15, comprising amplifying the filtered output signal output by the main filter section (210). Method according to one of claims 13-16, comprising adjusting at least the adjustable section (230) of the tuning feedback section (250) such that the second filter section (250) has a cutoff frequency which is equal to or greater than the cutoff frequency of the main filter section (210). Method according to one of claims 13-17, wherein analyzing the filtered output signal to determine a corresponding setting comprises a table search in a correlation data table (300, 350) to determine the corresponding setting. Method according to one of claims 13-18, wherein receiving a signal at a main filter section comprises receiving the signal at a main filter section (210) designed as a Butterworth filter. Method according to one of claims 13-19, wherein the method is carried out with the filter circuit according to one of claims 1-6.

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