TECHNIQUES FOR CONFIGURABLE ADC FRONT-END RC FILTER
1. A front-end circuit for suppressing signal transfer function peaking of a processing circuit, the front-end circuit comprising:
- a resistor-capacitor filter including at least two capacitors, the resistor-capacitor filter configured to couple an input analog signal to the processing circuit; and
a switch circuit coupled to a first capacitor of the at least two capacitors, the switch circuit configured to selectively place a terminal of the first capacitor at a selected one of a plurality of distinct nodes of the resistor-capacitor filter.
Techniques for a configurable analog-to-digital converter filter to ameliorate transfer function peaking or frequency response issues are provided. In an example, a front-end circuit of a processing circuit can include a resistor-capacitor filter including at least two capacitors and a switch circuit. The resistor-capacitor filter can couple an input analog signal to the processing circuit. The switch circuit can couple to a first capacitor of the at least two capacitors, and can selectively place a terminal of the first capacitor at a selected one of a plurality of distinct nodes of the resistor-capacitor filter to configure the circuit to address the peaking or frequency response issue.
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|Switched resistance device with reduced sensitivity to parasitic capacitance|
Patent #US 10,644,675 B2
Current AssigneeRobert Bosch GmbH
Sponsoring EntityRobert Bosch GmbH
|RESONATOR AND OVERSAMPLING A/D CONVERTER|
Patent #US 20110169677A1
Current AssigneePanasonic Intellectual Property Management Co. Ltd.
Sponsoring EntityPanasonic Corporation
|Ramp wave output circuit, analog/digital conversion circuit, and camera|
Patent #US 8,188,903 B2
Current AssigneePanasonic Corporation
Sponsoring EntityPanasonic Corporation
|REFERENCE VOLTAGE GENERATOR|
Patent #US 20150192946A1
Current AssigneeSamsung Electronics Co. Ltd.
Sponsoring EntitySamsung Electronics Co. Ltd.
- 1. A front-end circuit for suppressing signal transfer function peaking of a processing circuit, the front-end circuit comprising:
a resistor-capacitor filter including at least two capacitors, the resistor-capacitor filter configured to couple an input analog signal to the processing circuit; and a switch circuit coupled to a first capacitor of the at least two capacitors, the switch circuit configured to selectively place a terminal of the first capacitor at a selected one of a plurality of distinct nodes of the resistor-capacitor filter.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- 9. A front-end circuit for suppressing signal transfer function peaking of an analog-to-digital converter (ADC), the circuit comprising:
a plurality of resistor-capacitor (RC) filters selectively coupled in parallel with each other, the plurality of RC filters configured to couple an input analog signal with an integrator of the ADC; and wherein each resistor-capacitor filter includes at least two capacitors; and wherein a first capacitor of the at least two capacitors is electrically coupled closer to the integrator than a second capacitor of the at least two capacitors.
- View Dependent Claims (10, 11, 12, 13, 14, 15)
- 16. A system to enhance an analog-to-digital converter (ADC) transfer function by adjusting a front-end filter circuit, the system comprising:
an ADC; and a configurable resistor-capacitor filter having at least two capacitors, the configurable resistor-capacitor filter configured to receive an analog input signal, to pass the analog input signal to a first integrator of the ADC, and to suppress signal transfer function peaking of the ADC.
- View Dependent Claims (17, 18, 19, 20)
This patent application claims the benefit of priority of Gutta, U.S. Provisional Patent Application Ser. No. 62/532,178, entitled “TECHNIQUES FOR CONFIGURABLE ADC FRONT-END RC FILTER,” filed on Jul. 13, 2017 (Attorney Docket No. 3867.444PRV), which is hereby incorporated by reference herein in its entirety.
This document pertains generally, but not by way of limitation, to filters and, more particularly, to configurable filters for analog-to-digital converters (ADC).
An ADC can be defined, at least in part, by the following application requirements: its bandwidth (the range of frequencies of analog signals it can properly convert to a digital signal), its resolution (the number of discrete levels the maximum analog signal can be divided into and represented in the digital signal), and its signal to noise “SNR” ratio (how accurately the ADC can measure signal relative to the noise the ADC introduces). Analog-to-digital converters (ADCs) have many different designs, which can be chosen based on the application requirements. Signal transfer function peaking can be an issue with some designs of ADCs.
In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
Processing circuits such as analog-to-digital converters (ADCs) are electronic devices that can convert a continuous physical quantity carried by an analog input or signal to a digital number or output that represents the quantity'"'"'s amplitude (or to a digital signal carrying that digital number). The conversion involves quantization of the analog input signal, so it would introduce a small amount of error. Typically the quantization occurs through periodic sampling of the analog input signal. The result is a sequence of digital values (i.e., a digital signal) that has convened a continuous-time and continuous-amplitude analog input signal to a discrete-time and discrete-amplitude digital signal.
An ADC is usually defined by the following application requirements: its bandwidth (the range of frequencies of analog signals it can properly convert to a digital signal), its resolution (the number of discrete levels the maximum analog signal can be divided into and represented in the digital signal), and its signal to noise “SNR” ratio (how accurately the ADC can measure signal relative to the noise the ADC introduces). Analog-to-digital converters (ADCs) have many different designs, which can be chosen based on the application requirements.
Analog-to-digital converters (ADCs) based on delta-sigma (DS) modulation have been widely used in digital audio and high precision instrumentation systems. A delta-sigma ADC can include a loop filter, quantizer, and feedback digital-to-analog converter (DAC). A delta-sigma ADC can usually provide an advantage of being able to convert an analog input signal to a digital signal with high resolution at low cost. Typically, a delta-sigma ADC encodes an analog signal using a delta-sigma modulator or the quantizer. In certain examples, the quantizer can employ, for example, a low resolution ADC, such as a 1-bit ADC, Flash ADC, or Flash quantizer, etc. for encoding the analog signal. If applicable, the delta-sigma ADC can apply a digital filter to the output of the quantizer to form a higher-resolution digital output. The loop filter can include one or more integrators and may be included to provide error feedback for the delta-sigma ADC and to help shape the noise from the quantizer out of baseband to higher frequencies. The error is usually generated by taking the difference between the original analog input signal and a reconstructed version of the original analog input signal generated using the feedback DAC (where digitized signal is converted back into an analog signal). One key characteristic of a delta-sigma ADC is its ability to push the quantization noise, such as the noise from the quantizer 104) to higher frequencies. Pushing noise to different frequencies can also be referred to as noise shaping. The amount of noise shaping can depend on the order of the loop filter. delta-sigma ADCs are generally able to achieve high resolution analog-to-digital conversion.
Due to its popularity, many variations on the delta-sigma ADC and structures employing the delta-sigma ADC have been used and proposed. Depending on the application, different orders of the loop filter can be implemented. In some cases, the delta-sigma ADC can be implemented using continuous time circuitry (as opposed to discrete time circuitry). For example, the cascade of integrators can include discrete time integrators. In some cases, delta-sigma ADCs can be implemented with a mix of continuous time circuitry and discrete time circuitry for a hybrid architecture. For instance, some of the integrators (e.g., the first integrator in the cascade of integrators) can be implemented using continuous time circuitry while some other integrators (e.g., later integrator(s) in the cascade of integrators) can be implemented using discrete time circuitry. Generally speaking, a continuous-time, delta-sigma ADC or continuous-time circuitry can operate with lower power and achieve better wideband performance than its discrete time counterpart. Continuous-time, delta-sigma ADCs and discrete-time, delta-sigma ADC can also come in different flavors, e.g., feedback architecture and feedforward architecture. Different designs can affect the resulting signal transfer function and/or the noise transfer function of the delta-sigma ADC.
The ever increasing data rates in communication moves engineers to design analog-to-digital converters (ADCs) with higher Figures of Merit (FOM), e.g., greater requirements for bandwidth and accuracy, while being power efficient for prolonged battery life of the device having such ADCs. During the last couple of decades continuous-time, delta-sigma converters have been extensively used in high speed architectures due to the speed versus power advantages over its discrete-time counterpart (discrete-time, delta-sigma converters, having switch-capacitor circuits), and its inherent anti-aliasing capabilities.
While the above examples are shown as being continuous-time, delta-sigma analog-to-digital converters, discrete-time, delta-sigma ADCs can also have feedback and feedforward architectures. For a feedback discrete-time, delta-sigma ADC, the ADC 102 can have feedback paths from the output of the quantizer to the inputs of the integrators. For a feedforward, discrete-time, delta-sigma ADC, the ADC 102 can have a single main feedback path from the output of the quantizer to the input of the first integrator INT1, and the outputs of the integrators INT1, INT2, and INT3 are fed forward to the input of the quantizer. The feedback and feedforward configurations are applicable to hybrid architectures where both continuous time and discrete time circuits are used for the delta-sigma ADC.
One of the drawbacks of the continuous-time, feedforward, ADCs is that the Signal Transfer function (STF) at higher frequencies can exhibit peaking. In a continuous-time, feedforward, delta-sigma converter, at high frequencies, the first integrator and the associated feedforward path overrules other contributors and ensures stability. Referring to
Due to signal transfer function (STF) peaking, continuous-time, feedforward, delta-sigma ADCs can amplify interferers or out of band blocking signals. In wireless applications where the presence of out of band blocking signals can cause the modulator to overload, STF peaking can be problematic. For this reason, designers working in these applications often revert back to using a less power efficient continuous-time, feedback, delta-sigma ADC instead of using a continuous-time, feedforward, delta-sigma ADC. Some designers use a brute force approach to address the interferers and out of band blocking signals by adding a low pass filter or similar in front of the converter to remove the undesirable signal components, but such brute force approach is not always ideal. Using a low pass filter is not a power efficient solution to deal with the undesirable signal components. These aforementioned issues are applicable to discrete-time, feedforward, delta-sigma ADCs as well, or even hybrid continuous-time, discrete-time, feedforward, delta-sigma ADCS having both continuous time and discrete time circuitry. In addition to the above issues, manufacturing anomalies can also effect the intended 3 db frequency of the ADC which can effect phase match between two ADCs and can lead to modulator instability.
The present inventors have recognized a more effective configurable RC front-end filter 101 that allows configuration to ameliorate STF peaking and allow for adjustment of the desired 3 db frequency. In certain examples, the configurable RC front-end filter 101 can position a pole of the STF such that STF peaking is eliminated or reduced. In addition, the configurable RC front-end filter 101 can prevent the modulator or quantizer of the ADC from overloading.
In certain examples, each node 461, 462 of the capacitor 413 can be selectably coupled to an intermediate node 321, 322, 323, 324 of one of the networks 431, 432 of the series coupled resistances. In certain examples, for certain manufacturing anomalies, or when the ADC is operating a first frequency, the capacitor 413 can be connected, via a first switch 415 and a second switch 455, to a first pair of intermediate nodes 421, 423 to reduce or eliminate SFT peaking associated with the manufacturing anomalies or first frequency. In some examples, the capacitor 413 can be coupled to a second pair of intermediate nodes 422, 424 via a third switch 416 and a fourth switch 456 to ameliorate SFT peaking associated with the manufacturing anomalies, or with the operation of the ADC at a second frequency. In certain examples, the first pair of intermediate nodes 421, 423 can be located closer to the input of the ADC than the second pair of intermediate nodes 422, 424. In certain examples, the capacitor 413 can be spatially located closer to the output of the configurable RC front-end filter 401, or the input of the continuous-time, feedforward, delta-sigma ADC, to combat SFT peaking at lower frequencies and can be spatially located further from the input of the continuous-time, feedforward, delta-sigma ADC to combat SFT peaking at higher frequencies.
In certain examples, the configurable RC front-end filter 401 can optionally include additional resistances 414, 418, 444, 448 and a second capacitor 417. In some examples, the value of each resistance in each of the resistance networks 431, 432 can increase along with the distance the resistance, or resistor, is located from the output (OUT) of the configurable RC front-end filter 401. In some examples, spatial arrangement of the first capacitor 413 and the relative values of the resistances near the output (OUT) of the configurable RC front-end filter 401 can allow for programmability of the 3 db frequency of the configurable RC front-end filter 401.
In certain examples, the plurality of individual RC filters 561 can be arranged into two or more groups of filters 561, 562. In an example, each individual RC filter 560 of the plurality of RC filters of each group 561, 562 can have a filter architecture such as the filter architecture shown in the example of
It is understood that the configurable RC filter 501 can include more than two groups of individual RC filters without departing from the scope of the present subject matter. It is understood that each group of individual RC filters can include any number of individual RC filters without departing from the scope of the present subject matter. In certain examples, a first group of individual RC filters can include, for example, 32 RC filters having the resistances and capacitances design for a first 3 db frequency and a second group of individual RC filters can include, for example, 32 RC filters having the resistances and capacitances design for a second 3 db frequency, such that when a combination of the filters of the first group and filters of the second group are enabled, the filter can have a 3 db frequency that falls between the first 3 db frequency and the second 3 db frequency. In certain examples, a first group of individual RC filters can include a number of RC filters having the resistances and capacitances design for a first operating frequency of the ADC and a second group of individual RC filters can include a number of RC filters having the resistances and capacitances design for a second operating frequency of the ADC, such that when a combination of the filters of the first group and filters of the second group are enabled, the filter can ameliorate STF peaking at an operating frequency of the ADC falling between the first operating frequency and the second operating frequency that falls between the first 3 db frequency and the second 3 db frequency.
Examples, as described herein, may include, or may operate by, logic or a number of components, or mechanisms. Circuit sets are a collection of circuits implemented in tangible entities that include hardware (e.g., simple circuits, gates, logic, etc.). Circuit set membership may be flexible over time and underlying hardware variability. Circuit sets include members that may, alone or in combination, perform specified operations when operating. In an example, hardware of the circuit set may be immutably designed to carry out a specific operation (e.g., hardwired). In an example, the hardware of the circuit set may include variably connected physical components (e.g., execution units, transistors, simple circuits, etc.) including a computer readable medium physically modified (e.g., magnetically, electrically, moveable placement of invariant massed particles, etc.) to encode instructions of the specific operation. In connecting the physical components, the underlying electrical properties of a hardware constituent are changed, for example, from an insulator to a conductor or vice versa. The instructions enable embedded hardware (e.g., the execution units or a loading mechanism) to create members of the circuit set in hardware via the variable connections to carry out portions of the specific operation when in operation.
Accordingly, the computer readable medium is communicatively coupled to the other components of the circuit set member when the device is operating. In an example, any of the physical components may be used in more than one member of more than one circuit set. For example, under operation, execution units may be used in a first circuit of a first circuit set at one point in time and reused by a second circuit in the first circuit set, or by a third circuit in a second circuit set at a different time.
Machine (e.g., computer system) 600 may include a hardware processor 602 (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory 604 and a static memory 606, some or all of which may communicate with each other via an interlink (e.g., bus) 608. The machine 600 may further include a display unit 610, an alphanumeric input device 612 (e.g., a keyboard), and a user interface (UI) navigation device 614 (e.g., a mouse), sensors such as light or infrared sensors, gyroscopes, accelerometers and the associated filters and ADCs, such as those discussed above. In an example, the display unit 610, input device 612 and UI navigation device 614 may be a touch screen display. The machine 600 may additionally include a storage device (e.g., drive unit) 616, a signal generation device 618 (e.g., a speaker), a network interface device 620, and one or more sensors 621, such as a global positioning system (GPS) sensor, compass, position sensor system such as a position sensor system as discussed above, or other sensor. The machine 600 may include an output controller 628, such as a serial (e.g., universal serial bus (USB), parallel, or other wired or wireless (e.g., infrared (IR), near field communication (NFC), etc.) connection to communicate or control one or more peripheral devices a printer, card reader, etc.).
The storage device 616 may include a machine readable medium 622 on which is stored one or more sets of data structures or instructions 624 (e.g., software) embodying or utilized by any one or more of the techniques or functions described herein.
The instructions 624 may also reside, completely or at least partially, within the main memory 604, within static memory 606, or within the hardware processor 602 during execution thereof by the machine 600. In an example, one or any combination of the hardware processor 602, the main memory 604, the static memory 606, or the storage device 616 may constitute machine readable media.
While the machine readable medium 622 is illustrated as a single medium, the term “machine readable medium” may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) configured to store the one or more instructions 624.
The term “machine readable medium” may include any medium that is capable of storing, encoding, or carrying instructions for execution by the machine 600 and that cause the machine 600 to perform any one or more of the techniques of the present disclosure, or that is capable of storing, encoding or carrying data structures used by or associated with such instructions. Non-limiting machine readable medium examples may include solid-state memories, and optical and magnetic media. In an example, a massed machine readable medium comprises a machine readable medium with a plurality of particles having invariant (e.g., rest) mass. Accordingly, massed machine-readable media are not transitory propagating signals. Specific examples of massed machine readable media may include: non-volatile memory, such as semiconductor memory devices (e.g., Electrically Programmable Read-Only Memory (EPROM), Electrically Erasable Programmable Read-Only Memory (EEPROM)) and flash memory devices; magnetic disks, such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks.
The instructions 624 may further be transmitted or received over a communications network 626 using a transmission medium via the network interface device 620 utilizing any one of a number of transfer protocols (e.g., frame relay, internet protocol (IP), transmission control protocol (TCP), user datagram protocol (UDP), hypertext transfer protocol (HTTP), etc.). Example communication networks may include a local area network (LAN), a wide area network (WAN), a packet data network (e.g., the Internet), mobile telephone networks (e.g., cellular networks), Plain Old Telephone (POTS) networks, and wireless data networks (e.g., Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards known as Wi-Fi®, IEEE 802.16 family of standards known as WiMax®), IEEE 802.15.4 family of standards, peer-to-peer networks, among others. In an example, the network interface device 620 may include one or more physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one or more antennas to connect to the communications network 626. In an example, the network interface device 620 may include a plurality of antennas to wirelessly communicate using at least one of single-input multiple-output (SIMO), multiple-input multiple-output (MIMO), or multiple-input single-output (MISO) techniques. The term “transmission medium” shall be taken to include any intangible medium that is capable of storing, encoding or carrying instructions for execution by the machine 600, and includes digital or analog communications signals or other intangible medium to facilitate communication of such software.
The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein. In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls.
In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term are still deemed to fall within the scope of subject matter discussed. Moreover, such as may appear in a claim, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects.
Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like.
The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 CFR. § 1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of a claim. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. The following aspects are hereby incorporated into the Detailed Description as examples or embodiments, with each aspect standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations.