The disclosure relates generally to semiconductor devices and the corresponding circuits, and more particularly, to a solution for reducing an amount of intermodulation distortions in such devices and circuits.
Modern communication systems seek components having a high linearity in order to reduce intermodulation distortions. Intermodulation distortion can adversely affect the operation of multichannel systems utilizing closely spaced channel frequencies, f1, f2, f3, etc. When the current (I) voltage (V) characteristics of all the circuit components are perfectly linear, e.g., I=α1×V, where α1 is a constant coefficient, no frequency transformation and mixing occurs in the circuit. However, when some of the components have a nonlinear I-V relationship, intermodulation products appear in some or all of the signal channels. One of the most adverse types of intermodulation distortion are the third order distortions, which generate intermodulation products at frequencies corresponding to 2×f1±f2, 2×f2±f1, 2×f2±f3, etc. When the channel frequency separation is small, the third order intermodulation products generate signals within the channel frequencies, f1, f2, f3, etc., thereby creating intermodulation distortions.
The I-V nonlinearity responsible for the third order distortion comes from a term proportional to V3. In particular, when the actual I-V characteristic is approximated by the polynomial expression I=α1×V+α2×V2+α3×V3+ . . . , the α3 coefficient gives rise to the third order intermodulation distortions. Frequently, a level of third order intermodulation distortion can be characterized by calculating the third order intercept point (IP3). IP3 corresponds to a fictitious extrapolated input power level at which the power at a fundamental frequency equals the power at an intermodulation frequency (e.g., 2×f1±f2). For a single element, IP3 in dBm can be calculated by:
IP3=10×log10[4×α13/(3×α3)×103].
A more practical expression for the magnitude of IP3 comes from considering a nonlinear component connected into a circuit.
Aspects of the invention provide a solution for compensating intermodulation distortion of a component. A circuit element includes multiple connected components. At least two of the connected components comprise current-voltage characteristics of opposite signs (e.g., sublinear and superlinear current-voltage characteristics) such that the current-voltage characteristics of the circuit element produces a level of intermodulation distortion for the circuit element lower than a level of intermodulation distortion for each of the connected components.
A first aspect of the invention provides a circuit element comprising: a plurality of connected components, the plurality of connected components including: at least one sublinear connected component, each of the at least one sublinear connected component having sublinear current-voltage characteristics; and at least one superlinear connected component, each of the at least one superlinear connected component having superlinear current-voltage characteristics, wherein the plurality of connected components are connected such that the current-voltage characteristics of the circuit element produces a level of intermodulation distortion for the circuit element lower than a level of intermodulation distortion for each of the plurality of connected components.
A second aspect of the invention provides a circuit comprising: at least one circuit element comprising: a plurality of connected components, the plurality of connected components including: at least one sublinear connected component, each of the at least one sublinear connected component having sublinear current-voltage characteristics; and at least one superlinear connected component, each of the at least one superlinear connected component having superlinear current-voltage characteristics, wherein the plurality of connected components are connected such that the current-voltage characteristics of the circuit element produces a level of intermodulation distortion for the circuit element lower than a level of intermodulation distortion for each of the plurality of connected components; a source electrically connected to an input of the at least one circuit element; and a load electrically connected to an output of the at least one circuit element.
A third aspect of the invention provides a circuit comprising: a first circuit element comprising: an active component; and a controllable circuit component connected to the active component, wherein the controllable circuit component has a variable and controllable nonlinearity; a linearity measurement component connected to an output of the first circuit element, wherein the linearity measurement component is configured to generate data corresponding to a linearity measurement of the first circuit element; and a control component connected to an output of the linearity measurement component and the controllable circuit component, wherein the control component is configured to generate a set of control signals to adjust the nonlinearity of the controllable circuit component based on data received from the linearity measurement component and a target level of linearity for the first circuit element.
The illustrative aspects of the invention are designed to solve one or more of the problems herein described and/or one or more other problems not discussed.
These and other features of the disclosure will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various aspects of the invention.
It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements between the drawings.
As indicated above, aspects of the invention provide a solution for compensating intermodulation distortion of a component. A circuit element includes multiple connected components. At least two of the connected components comprise current-voltage characteristics of opposite signs (e.g., sublinear and superlinear current-voltage characteristics) such that the current-voltage characteristics of the circuit element produces a level of intermodulation distortion for the circuit element lower than a level of intermodulation distortion for each of the connected components. To this extent, the solution can reduce the intermodulation distortions in devices and circuits, such as semiconductor devices and radio frequency devices and circuits, e.g., as part of a communications system. While illustrative aspects are shown and described herein with reference to third order distortions, it is understood that aspects of the invention can be applied to compensate other order distortions, such as second order distortions. As used herein, unless otherwise noted, the term “set” means one or more (i.e., at least one) and the phrase “any solution” means any now known or later developed solution.
Turning to the drawings,
Each of the components of the device 4A, 4B, the contacts 6A, 6B and the device channel 8, can have nonlinear current-voltage (I-V) characteristics, thereby giving rise to inter-modulation distortions.
In an illustrative example, the circuit 2 of
When the values of the α3 coefficients of the components 14, 16 are substantially equal in magnitude with opposite signs, the circuit element 12 comprising the series connection of the two components 14, 16 provides an I-V characteristic substantially equal to the I-V characteristics with a zero α3 coefficient as shown by line (0) in
In an illustrative configuration, the first component 14 can have I-V characteristics given by I=α1×V+α3×V3, where α1=1 and α3=−0.002, and the second component 16 can have I-V characteristics given by I=α1×V+α3×V3, where α1=1 and α3=0.00199. Simulations of these parameters indicate the I-V characteristics of the series connection of the components 14, 16 is given by I=α1×V+α3×V3, where α1=0.5 and α3=7.88E-15. Using the expression (1), the IP3 point can be calculated as IP3=193 dBm. As illustrated, the inclusion of a compensating component provides a substantial increase in the IP3 values, which well exceeds any practical values demonstrated to date.
As discussed herein, a compensating component 22A, 22B can have an opposite sign for the α3 coefficient to that of the active component 24. The I-V characteristics of the diode D1, D2 can be calculated by: ID=IS×exp(V/0.026), where IS is the reverse bias saturation current, while the I-V characteristics of the resistor R1, R2 can be calculated by: IR=G×V, where G is the conductance of the resistor R1, R2. In an embodiment, the active component 24 comprises a channel of the element 20A-20C.
Referring to
It is understood that the α3 coefficient can be further decreased by fine tuning the resistor value, the diode IS parameter, and/or other diode parameters, which will result in a corresponding increase for the IP3. For example, in the example above, changing the conductance of the resistor R1 to G=11E3, results in a compensated α3 coefficient value of α3=1.33E-5. The corresponding IP3=100.8 dBm, which is approximately a 36 dBm improvement compared to the IP3 of an uncompensated device. Similarly, a value of the maximum diode current for the diode D1 can be adjusted to make the absolute value of the α3 coefficient of the compensating component 22A the same or close to the absolute value of the active component 24.
The various elements 20A-20C can be manufactured using any solution. For example, the diode(s) D1, D2 and resistor(s) R1, R2 can comprise external components, which are electrically connected to the active component 24 as illustrated by one or more of
To this extent,
Each contact 32A, 32B comprises a contact area 36 within which are included a set diode cells (pixels) 38. Each diode cell 38 comprises a region within which the contact between the metal electrode 32A, 32B and the semiconductor material of the channel 34 is of a Schottky or p-n junction type. The diode cells 38 can be formed using any solution, e.g., by a metal deposition and selective doping of semiconductor materials solution. The remaining contact area 36 forms an Ohmic or linear resistance contact to the semiconductor material of the channel 34. In an embodiment, a ratio of the total area covered by the set of diode cells 38 to the total area covered by the remaining contact area 36 is selected to obtain a target relation between the diode and resistor I-V characteristics and the I-V characteristics of the channel 34 as described herein. While each contact 32A, 32B is shown including a particular number and configuration of diode cells 38, it is understood that a contact 32A, 32B can have any number and/or configuration of diode cells 38.
Various configurations are possible for the elements described herein. In an embodiment, the active component comprises a transistor, to which at least one compensating component is connected in series with the channel of the transistor (e.g., on the source and/or drain side of the transistor). In this case, the transistor can have a sublinear I-V characteristic and the compensating component(s) can have a superlinear I-V characteristics. Illustrative compensating components with superlinear I-V characteristics include: a Schottky contact; a parallel connection of a Schottky diode and a linear or variable resistor (e.g., as shown in
An embodiment of the element described herein can be implemented as part of various types of devices and/or circuits. Illustrative devices including at least one element according to an embodiment include: a radio frequency (RF switch); a power switch; an attenuator; a power limiter; an amplifier; and/or the like. Such devices can be incorporated in various types of circuits, such as communication systems. Furthermore, an embodiment of the element described herein can be formed from various materials. In an illustrative embodiment, an element is formed of one or more III-V materials, e.g., a heterostructure. In a more particular illustrative embodiment, the element and/or component is a group III nitride based component, in which one or more layers of the element and/or a component thereof is formed of a group III nitride based material. Group III nitride materials comprise one or more group III elements (e.g., boron (B), aluminum (Al), gallium (Ga), and indium (In)) and nitrogen (N), such that BWAlXGaYInZN, where 0≦W, X, Y, Z≦1, and W+X+Y+Z=1. Illustrative group III nitride materials include AlN, GaN, InN, BN, AlGaN, AlInN, AlBN, AlGalnN, AlGaBN, AlInBN, and AlGalnBN with any molar fraction of group III elements.
An embodiment provides a circuit for controlling a level of linearity of a device. To this extent,
Additionally, an output of the element 42 is evaluated by a linearity level measurement unit 44. The linearity level measurement unit 44 can generate data corresponding to the linearity of the output of the element 42 by, for example, performing a standard two-tone measurement technique, extracting linearity coefficients from a measured I-V characteristic, and/or the like. The linearity level measurement unit 44 generates a set of data signals corresponding to a measurement of the linearity (or nonlinearity) of the output of the element 42. The set of data signals is provided for use by a control system 46, which can adjust one or more aspects of the compensating components 22A, 22B affecting the corresponding nonlinearity of the compensating components 22A, 22B in order to achieve a target level of linearity for the element 42 based on the set of data signals. In an embodiment, control system 46 can generate a set of control signals that adjust the resistance values of variable resistors R1 and/or R2 to achieve a target level of linearity for the element 42.
In an embodiment, control system 46 comprises a computer system. In a more particular embodiment, control system 46 comprises a general purpose computer system executing program code, which enables the control system 46 to generate a set of output signals to adjust one or more aspects of the compensating components 22A, 22B based on a set of data signals corresponding to the linearity of the output of the element 42. In an embodiment, the control system 46 can receive a set of data signals from the linearity level measurement unit 44 corresponding to a measured I-V characteristic, and can generate a set of output signals there from. For example, the control system 46 can extract linearity coefficients from the measured I-V characteristic and can generate a set of output signals to implement a set of adjustments as defined by the linearity coefficients, the target level of linearity, and a relationship there between. Furthermore, the control system 46 can enable a user (human or another system) to provide data, such as the target level of linearity, which is used in generating the set of control signals. Similarly, control system 46 can provide data for presentation and/or processing by the user using any solution.
While shown and described herein as a method of designing and/or fabricating a nonlinearity compensated element, it is understood that aspects of the invention further provide various alternative embodiments. For example, in one embodiment, the invention provides a method of designing and/or fabricating a circuit that includes one or more of the nonlinearity compensated elements designed and fabricated as described herein.
To this extent,
In another embodiment, the invention provides a device design system 110 for designing and/or a device fabrication system 114 for fabricating a semiconductor device 116 as described herein. In this case, the system 110, 114 can comprise a general purpose computing device, which is programmed to implement a method of designing and/or fabricating the semiconductor device 116 as described herein. Similarly, an embodiment of the invention provides a circuit design system 120 for designing and/or a circuit fabrication system 124 for fabricating a circuit 126 that includes at least one device 116 designed and/or fabricated as described herein. In this case, the system 120, 124 can comprise a general purpose computing device, which is programmed to implement a method of designing and/or fabricating the circuit 126 including at least one semiconductor device 116 as described herein.
In still another embodiment, the invention provides a computer program fixed in at least one computer-readable medium, which when executed, enables a computer system to implement a method of designing and/or fabricating a semiconductor device as described herein. For example, the computer program can enable the device design system 110 to generate the device design 112 as described herein. To this extent, the computer-readable medium includes program code, which implements some or all of a process described herein when executed by the computer system. It is understood that the term “computer-readable medium” comprises one or more of any type of tangible medium of expression, now known or later developed, from which a copy of the program code can be perceived, reproduced, or otherwise communicated by a computing device. For example, the computer-readable medium can comprise: one or more portable storage articles of manufacture; one or more memory/storage components of a computing device; paper; and/or the like.
In another embodiment, the invention provides a method of providing a copy of program code, which implements some or all of a process described herein when executed by a computer system. In this case, a computer system can process a copy of the program code to generate and transmit, for reception at a second, distinct location, a set of data signals that has one or more of its characteristics set and/or changed in such a manner as to encode a copy of the program code in the set of data signals. Similarly, an embodiment of the invention provides a method of acquiring a copy of program code that implements some or all of a process described herein, which includes a computer system receiving the set of data signals described herein, and translating the set of data signals into a copy of the computer program fixed in at least one computer-readable medium. In either case, the set of data signals can be transmitted/received using any type of communications link.
In still another embodiment, the invention provides a method of generating a device design system 110 for designing and/or a device fabrication system 114 for fabricating a semiconductor device as described herein. In this case, a computer system can be obtained (e.g., created, maintained, made available, etc.) and one or more components for performing a process described herein can be obtained (e.g., created, purchased, used, modified, etc.) and deployed to the computer system. To this extent, the deployment can comprise one or more of: (1) installing program code on a computing device; (2) adding one or more computing and/or I/O devices to the computer system; (3) incorporating and/or modifying the computer system to enable it to perform a process described herein; and/or the like.
The foregoing description of various aspects of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to an individual in the art are included within the scope of the invention as defined by the accompanying claims.
The current application claims the benefit of co-pending U.S. Provisional Application No. 61/419,923, titled “Device and circuit with improved linearity,” which was filed on 6 Dec. 2010, and which is hereby incorporated by reference.
Number | Date | Country | |
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61419923 | Dec 2010 | US |