Thermoelectric power meter

An apparatus and a system measure electrical power with improved accuracy as a result of compensating for sources of thermal energy that are not caused by the electrical power of the electrical circuit under test. The apparatuses and systems provide a separate electrical signal source (e.g. RF electrical circuits under test) and DC sides. The apparatuses and systems include devices adapted to convert thermal energy into voltages having reversed polarities. The apparatuses and systems are adapted to compensate for temperature changes not caused by the electrical power of the electrical circuit under test (e.g., ambient temperature change and thermal energy transmitted through the signal transmission lines from sources in the electrical circuit).

BACKGROUND

Power meters are used in many applications, such as in radio frequency (RF) or other frequency band applications. Many of the known power meters used in RF power measurements are adversely impacted by thermal changes, which in turn adversely impact the measurement accuracy from the power meters.

Sources of heat that can adversely impact the accuracy of power measurements include ambient temperature changes where the power meter is disposed, and thermal energy generated by the electrical circuit under test. The ambient temperature change results in a change in the output voltage of the RF power meter that is unrelated, of course, to the output power of the electrical circuit under test. The electrical circuit under test includes signal transmission lines (e.g., coaxial cables and planar transmission lines) that conduct heat from the electrical circuit, such as an power source, which heats up during operation. The temperature changes caused by the heat conducted by the signal transmission lines also results in a change in the output voltage of the power meter that is unrelated, of course, to the output power of the electrical circuit under test.

As will be appreciated, the noted and other sources of heat adversely impact the performance of known RF power meters. What is needed, therefore, is an optical wavemeter that overcomes at least the shortcomings of known optical wavemeters discussed above.

DETAILED DESCRIPTION

Unless otherwise noted, when a first element is said to be connected to a second element this encompasses cases where one or more intermediate elements or intervening devices may be employed to connect the two elements to each other. However, when a first element is said to be directly connected to a second element, this encompasses only cases where the two elements are connected to each other without any intermediate or intervening devices. Similarly, when a signal is said to be coupled to an element, this encompasses cases where one or more intermediate elements may be employed to couple the signal to the element. However, when a signal is said to be directly coupled to an element, this encompasses only cases where the signal is directly coupled to the element without any intermediate or intervening devices.

As used in the specification and appended claims, the terms “a”, “an” and “the” include both singular and plural referents, unless the context clearly dictates otherwise. Thus, for example, “a device” includes one device and plural devices. As used in the specification and appended claims, and in addition to their ordinary meanings, the terms “substantial” or “substantially” mean to within acceptable limits or degree. For example, “substantially identical” means that one of ordinary skill in the art would consider the items being compared to be the identical.

As used in the specification and the appended claims and in addition to its ordinary meaning, the term “approximately” means to within an acceptable limit or amount to one having ordinary skill in the art. For example, “approximately the same” means that one of ordinary skill in the art would consider the items being compared to be the same.

Various representative embodiments relate to an apparatus and a system for measuring electrical power with improved accuracy as a result of compensating for sources of thermal energy that are not caused by the electrical power of the electrical circuit under test. As described more fully below in accordance with various representative embodiments, the apparatuses and systems of the present teachings provide separate comparatively high frequency band electrical signal source and DC sides. The apparatuses and systems include devices adapted to convert thermal energy into voltages having reversed polarities. The apparatuses and systems of the present teachings are adapted to compensate for temperature changes not caused by the electrical power of the electrical circuit under test (e.g., ambient temperature change and thermal energy transmitted through the signal transmission lines from sources in the electrical circuit). The resultant apparatuses and systems provide improved accuracy in measurements of power of an electrical circuit under test.

In accordance with a representative embodiment, apparatus for measuring electrical power is described. The apparatus comprises: a substrate; a first device adapted to convert thermal energy into a first voltage. The first device comprises a first thermopile or a first thermocouple, and has a first input and a first output. The first device is disposed over the substrate adjacent to a first resistor. The apparatus also comprises a second device adapted to convert thermal energy into a second voltage. The second device comprises a second thermopile or a second thermocouple, and the second device has a second input and a second output. The second device is disposed over the substrate adjacent to a second resistor. Due to the reversed polarities of the first and second devices, the first output and the second output have opposite polarities. The apparatus may also comprise a source measurement unit (SMU) comprising a direct current (DC) voltage source and a DC voltmeter connected to the second resistor. The SMU provides a third voltage to the second resistor to maintain a voltage between the first and second outputs at a balanced level.

In accordance with another representative embodiment, a system for measuring electrical power is described. The system comprises: a controller comprising a processor; a tangible, non-transitory computer-readable medium that stores instructions; a substrate; a first device adapted to convert thermal energy into a first voltage, the first device comprising a first thermopile or a first thermocouple. The first device has a first input and a first output, and the first device is disposed over the substrate adjacent to a first resistor. The system also comprises a second device adapted to convert thermal energy into a second voltage. The second device comprises a second thermopile or a second thermocouple, and has a second input and a second output. The second device is disposed over the substrate adjacent to a second resistor. Due to the reversed polarities of the first and second devices, the first output and the second output have opposite polarities. The system may also comprise a source measurement unit comprising a direct current (DC) voltage source and a DC voltmeter connected to the second resistor. When executed by the processor, the processor causes the source measurement unit to provide a third voltage to the second resistor to maintain a voltage between the first and second outputs at a balanced level.

FIG.1is a simplified schematic diagram of an apparatus100in accordance with a representative embodiment. As will become clearer as the present teachings continue, the apparatus100may be used as a power meter or power measurement device.

The apparatus100is disposed over a substrate102, and comprises a first device104adapted to convert thermal energy into a first voltage, and a second device106adapted to convert thermal energy into a second voltage. The substrate102is unitary, and is selected to have a substantially uniform coefficient of thermal conductivity, and thus heats and cools substantially equally when the ambient temperature changes. In accordance with a representative embodiment, the substrate102is selected from a material having the desired uniform heating/cooling, and may comprise silicon (Si), gallium arsenide (GaAs), and or gallium nitride (GaN). It is emphasized that the noted materials are merely illustrative, and other materials that provide the desired substantially uniform coefficient of thermal conductivity within the purview of one of ordinary skill in the art having the benefit of the present teachings are also contemplated. Notably, and as described more fully below, the various components depicted inFIG.1are disposed over the substrate102.

The first device104and the second device106are substantially identical but have opposing polarities as described more fully below. In accordance with a representative embodiment, the first device104and the second device106are either thermopiles or thermocouples. Illustratively, the first and second devices104,106comprise substantially identical thermocouples or thermopiles. Such substantially identical first and second devices are realized by fabricating the structures of the first and second devices104,106to be symmetrical or mirror images to each other on a unity substrate (e.g., substrate102). By fabricating the structures of the first and second devices104,106this way results in the devices' having similar sensitivity to the thermal change, which is detected at the output voltage of the respective first and second devices104,106. Finally, it is noted that it is beneficial for the first and second resistors108,110to have same magnitudes and similar temperature coefficients.

Notably, and as shown inFIG.1, the first device104and the second device106have opposite polarities, so their voltage outputs having opposing signs. As described more fully below, this aspect of the first and second device104,106is used to adjust for thermal changes caused by the ambient, heat from electrical circuitry under test, and to provide a measurement of the power from the electrical circuitry under test.

The first device104is disposed adjacent to a first resistor108, and the second device106is disposed adjacent to a second resistor110. Notably, the first device104is electrically isolated from the first resistor108, and the second device106is electrically isolated from the second resistor110. The first device104is disposed between a first input112and a first output114. The second device106is connected between a second input116and a second output118. A common input120is disposed between the first and second device104,106, and its function will become clearer as the present description continues.

As alluded to above, the apparatus is adapted to perform electrical measurements of an electrical circuit (not shown inFIG.1) connected to the first device104, and may be a circuit that operates at comparatively high frequency electrical signal frequencies. The present teachings contemplate the apparatus100is adapted to perform power measurements on electrical circuits in the RF, Microwave, Millimeter Wave and sub terahertz frequency ranges. For ease of description, however, the various representative embodiments are described in connection with electrical circuits that operate in the RF band. As such, the first input112, the first device104, the first output114, and the first resistor108disposed over the substrate102may be referred to as the ‘RF side’ of the apparatus100. By contrast, and as described more fully below, the second input116is connected to a direct current (DC) source that supplies power to the second input116that is used to adjust the operation of the apparatus to account for ambient temperature changes, temperature changes from the electrical circuit, and to provide a measure of the power dissipated from the electrical circuit connected to the first input112. As such, the second input116, the second device106, the second output118, and the second resistor disposed over the substrate102may be referred to as the ‘DC side’ of the apparatus.

As described more fully below, maintaining the voltage between the first output114and the second output118at a balanced level results in the adjustment to account for ambient temperature changes, temperature changes to the RF side caused by the electrical circuit to which it is attached, and the measure of the power dissipated from the electrical circuit connected to the first input112. As such, when thermal energy is transferred to the first device104, due to the function of the first device104, a voltage VTH1is established. This will alter the balanced state between the first output114and the second output118. Application of a voltage VTH2between the second input116and the second output118having the same magnitude returns the first output114and the second output118to a balanced state.

As noted above, the first device104and the second device106are selected to be substantially identical but have opposite polarities. An initial balanced state is determined by a measure of VTH1and VTH2with no power applied from the electrical circuit connected to the first input. This is effected by constructing/disposing the substantially identical first and second devices104,106over substrate102to have similar thermal properties, and constructing the first and second device104,106to be symmetrical so both devices have a similar sensitivity to a change in temperature. However, and as described more fully below, the first and second devices104,106are substantially thermally isolated from one another. Just by way of illustration, during measurements of power from the electrical circuitry up to a power level across the first resistor of approximately 20 dBm, no substantial transfer of heat from the RF side to the DC side occurs. This approach allows the detector to be used in wide range ambient temperature with very low or negligible thermal drift in the output voltages of the first and second device104,106. Residual thermal drift is almost constant or can be corrected with linear variation to the ambient temperature. This approach can be referred to as a built-in thermal drift correction which eliminate the need of complex test setup and time-consuming temperature calibration and correction.

After establishing the balanced state, changes in the ambient temperature of the apparatus100result in substantially uniform heating of the first and second devices104,106. This increase in temperature across the first and second device104,106will cause both VTH1, VTH2to increase. This increase in temperature is substantially identical by selection of the substrate102. Moreover, because the first and second devices104,106are substantially identical, but of opposite polarities, the VTH1. VTH2increase substantially. Accordingly, voltages at the first and second outputs114,118have substantially the same magnitude, but opposite side. Thus, the balanced state realized upon initialization of the apparatus is maintained.

Among other benefits, the apparatus100is adapted to be used in a comparatively wide range of ambient temperatures with no appreciable thermal drift in the output voltages of the first and second device104,106. As such, the apparatus100provides passive thermal drift correction and significantly reduces, if not completely eliminates the need of a comparatively complex test setup and time-consuming calibration and correction to account for ambient temperature shifts that plague known devices.

FIG.2is a simplified circuit diagram of an apparatus200for measuring electrical power in accordance with a representative embodiment. More particularly, the description ofFIG.2is directed to adjusting for heat transferred from an electrical circuit230in accordance with a representative embodiment. Various aspects and details of apparatus100described in connection withFIG.1above may be common to those of apparatus200. These common aspects and details may not be repeated to avoid obscuring the presently described representative embodiments.

The apparatus200is disposed over a substrate202, and comprises a first device204adapted to convert thermal energy into a first voltage, and a second device206adapted to convert thermal energy into a second voltage. The substrate202is unitary, and is selected to have a substantially uniform coefficient of thermal conductivity, and thus heats and cools substantially equally when the ambient temperature changes. In accordance with a representative embodiment, the substrate202is selected from a material having the desired uniform heating/cooling, and may comprise silicon (Si), gallium arsenide (GaAs), and or gallium nitride (GaN). It is emphasized that the noted materials are merely illustrative, and other materials that provide the desired substantially uniform coefficient of thermal conductivity within the purview of one of ordinary skill in the art having the benefit of the present teachings are also contemplated. Notably, and as described more fully below, the various components depicted inFIG.2are disposed over the substrate202.

The first device204and the second device206are substantially identical but have opposing polarities as described more fully below. In accordance with a representative embodiment, the first device204and the second device206are either thermopiles or thermocouples. Again, as noted above, the first and second devices104,106comprise substantially identical thermocouples or thermopiles. Such substantially identical first and second devices are realized by fabricating the structures of the first and second devices104,106to be symmetrical or mirror images to each other on a unity substrate (e.g., substrate102). By fabricating the structures of the first and second devices104,106this way results in the devices' having similar sensitivity to the thermal change, which is detected at the output voltage of the respective first and second devices104,106. Finally, it is noted that it is beneficial for the first and second resistors108,110to have same magnitudes and similar temperature coefficients.

Notably, and as shown inFIG.1, the first device204and the second device206have opposite polarities, so their voltage outputs having opposing signs. As described more fully below, this aspect of the first and second device204,206is used to adjust for thermal changes caused by the ambient, heat from electrical circuitry under test, and to provide a measurement of the power from the electrical circuitry under test.

The first device204is disposed adjacent to a first resistor208, and the second device206is disposed adjacent to a second resistor210. Notably, the first device204is electrically isolated from the first resistor208, and the second device206is electrically isolated from the second resistor210. The first device204is disposed between a first input212and a first output214. The second device206is connected between a second input216and a second output218. A common input120is disposed between the first and second device204,206, and its function will become clearer as the present description continues.

As alluded to above, the apparatus is adapted to perform electrical measurements of an electrical circuit230connected to the first device204. The electrical circuit230operates at comparatively high frequency electrical signal frequencies. The present teachings contemplate the apparatus100is adapted to perform power measurements on electrical circuits in the RF, Microwave, Millimeter Wave and sub terahertz frequency ranges. For ease of description, however, the various representative embodiments are described in connection with electrical circuits that operate in the RF band. As such, the first input212, the first device204, the first output214, and the first resistor208disposed over the substrate202may be referred to as the ‘RF side’ of the apparatus200. By contrast, and as described more fully below, the second input216is connected to a direct current (DC) source that supplies power to the second input216that is used to adjust the operation of the apparatus to account for ambient temperature changes, temperature changes from the electrical circuit, and to provide a measure of the power dissipated from the electrical circuit connected to the first input212. As such, the second input216, the second device206, the second output218, and the second resistor disposed over the substrate202may be referred to as the ‘DC side’ of the apparatus.

As described more fully below, maintaining the voltage between the first output214and the second output218at a balanced level results in the adjustment to account for ambient temperature changes, temperature changes to the RF side caused by the electrical circuit to which it is attached, and the measure of the power dissipated from the electrical circuit connected to the first input212. As such, when thermal energy is transferred to the first device204, due to the function of the first device204, a voltage VTH1is established. This will alter the balanced state between the first output214and the second output218. Application of a voltage VTH2between the first input212and the second output218having the same magnitude returns the first output214and the second output218to a balanced state.

As noted above, the first device204and the second device206are selected to be substantially identical but have opposite polarities. An initial balanced state is determined by a measure of VTH1and VTH2with no power applied from the electrical circuit connected to the first input. This is effected by constructing/disposing the substantially identical first and second devices204,206over substrate202to have similar thermal properties, and constructing the first and second device204,206to be symmetrical so both devices have a similar sensitivity to a change in temperature. However, and as described more fully below, the first and second devices104,106are substantially thermally isolated from one another. Just by way of illustration, again, during measurements of power from the electrical circuit230up to a power level across the first resistor208of approximately 20 dBm, no substantial transfer of heat from the RF side to the DC side occurs. As described more fully below, this thermal isolation aids accurately adjusting for a change in thermal energy caused by the electrical circuit230.

The electrical circuit230illustratively comprises a source232of thermal energy. Just by way of illustration, the electrical circuit230may comprises an RF source including an RF amplifier, or some other device under test (DUT). The source232is electrically connected by a connection to the apparatus200. The electrical connection234generally comprises typical electrical circuitry, such as a coaxial cable signal transmission line or planar waveguide. The electrical connection234necessarily comprises electrically conductive materials (e.g., metals/metal alloys), which conduct not only electricity, but also thermal energy. Moreover, the components of the electrical connection when conducting electricity also generate thermal energy. This thermal energy transmitted through and generated by electrical conduction in the components of the electrical connection234to the first input212on the RF side of the apparatus200.

The increase in thermal energy is transmitted through and generated by electrical conduction in the components of the electrical connection234to the first input212, and causes an increase in temperature of the first device204. When the temperature at the first device204increases, an increase in the voltage VTH1occurs, and is measured by the digital multimeter (DMM)236. Notably, and as described more fully below, the DMM is comparatively accurate, and illustratively is an 8 digit device so accurate changes in VTH1can be measured. Because of the change in VTH1results in a voltage differential between first output214and second output218, which when substantial enough, disturbs the balance between first output214and second output218. Specifically, and as noted above the RF side and the DC side are substantially thermally isolated, and as a result, the change in temperature caused and transmitted by the electrical circuit230only alters the temperature of the first device204, and not the second device206. As such, initial balanced state that is determined by a measure of VTH1and VTH2with no power applied from the electrical circuit230connected to the first input212, is disturbed. As described more fully below, this net change in voltage between the first output214and the second output218, is returned to a balanced state by adjusting the voltage at the second input216by application of a DC voltage at the second input216having a magnitude equal to that measured by the DMM236.

FIG.3is a simplified circuit diagram of an system300for measuring electrical power in accordance with a representative embodiment. More particularly, the description ofFIG.2is directed to adjusting for heat transferred from an electrical circuit330(e.g., an RF source) in accordance with a representative embodiment. Various aspects and details of apparatuses100,200described in connection withFIGS.1and2above may be common to those of system300. These common aspects and details may not be repeated to avoid obscuring the presently described representative embodiments.

The system300is disposed over a substrate302, and comprises a first device304adapted to convert thermal energy into a first voltage, and a second device306adapted to convert thermal energy into a second voltage. The substrate302is unitary, and is selected to have a substantially uniform coefficient of thermal conductivity, and thus heats and cools substantially equally when the ambient temperature changes. In accordance with a representative embodiment, the substrate302is selected from a material having the desired uniform heating/cooling, and may comprise silicon (Si), gallium arsenide (GaAs), and or gallium nitride (GaN). It is emphasized that the noted materials are merely illustrative, and other materials that provide the desired substantially uniform coefficient of thermal conductivity within the purview of one of ordinary skill in the art having the benefit of the present teachings are also contemplated. Notably, and as described more fully below, the various components depicted inFIG.2are disposed over the substrate302.

The first device304and the second device306are substantially identical but have opposing polarities as described more fully below. In accordance with a representative embodiment, the first device304and the second device306are either thermopiles or thermocouples. Notably, and as shown inFIG.1, the first device304and the second device306have opposite polarities, so their voltage outputs having opposing signs. As described more fully below, this aspect of the first and second device304,306is used to adjust for thermal changes caused by the ambient, heat from electrical circuitry under test, and to provide a measurement of the power from the electrical circuitry under test.

The first device304is disposed adjacent to a first resistor308, and the second device306is disposed adjacent to a second resistor320. Notably, the first device304is electrically isolated from the first resistor308, and the second device306is electrically isolated from the second resistor310. The first device304is disposed between a first input312and a first output314. The second device306is connected between a second input316and a second output318. A common input120is disposed between the first and second device304,306, and its function will become clearer as the present description continues.

As alluded to above, the apparatus is adapted to perform electrical measurements of an electrical circuit330connected to the first device304, and may be a circuit that operates at RF frequencies. As such, the first input312, the first device304, the first output314, and the first resistor308disposed over the substrate302may be referred to as the ‘RF side’ of the system300. By contrast, and as described more fully below, the second input316is connected to a direct current (DC) source that supplies power to the second input316that is used to adjust the operation of the apparatus to account for ambient temperature changes, temperature changes from the electrical circuit, and to provide a measure of the power dissipated from the electrical circuit connected to the first input312. As such, the second input316, the second device306, the second output318, and the second resistor disposed over the substrate302may be referred to as the ‘DC side’ of the apparatus.

As described more fully below, maintaining the voltage between the first output314and the second output318at a balanced level results in the adjustment to account for ambient temperature changes, temperature changes to the RF side caused by the electrical circuit to which it is attached, and the measure of the power dissipated from the electrical circuit connected to the first input312. As such, when thermal energy is transferred to the first device304, due to the function of the first device304, a voltage VTH1is established. This will alter the balanced state between the first output314and the second output318. Application of a voltage VTH2between the second input316and the second output318having the same magnitude returns the first output314and the second output318to a balanced state.

As noted above, the first device304and the second device306are selected to be substantially identical but have opposite polarities. An initial balanced state is determined by a measure of VTH1and VTH2with no power applied from the electrical circuit connected to the first input. This is effected by constructing/disposing the substantially identical first and second devices304,306over substrate302to have similar thermal properties, and constructing the first and second device304,306to be symmetrical so both devices have a similar sensitivity to a change in temperature. However, and as described more fully below, the first and second devices304,306are substantially thermally isolated from one another. Just by way of illustration, again, during measurements of power from the electrical circuit330up to a power level across the first resistor308of approximately 20 dBm, no substantial transfer of heat from the RF side to the DC side occurs. As described more fully below, this thermal isolation aids accurately adjusting for a change in thermal energy caused by the electrical circuit330.

The system300is adapted to measure the power from the electrical circuit330as described more fully below. Just by way of illustration, the source may comprises an RF source including an RF amplifier, or some other device under test (DUT). The electrical circuit330is electrically connected by a connection to the system300. Again, the electrical connection generally comprises typical electrical circuitry, such as a coaxial cable signal transmission line or planar waveguide. The electrical connection necessarily comprises electrically conductive materials (e.g., metals/metal alloys), which conduct not only electricity, but also thermal energy. Moreover, the components of the electrical connection when conducting electricity also generate thermal energy. This thermal energy transmitted through and generated by electrical conduction in the components of the electrical connection to the first input312on the RF side of the system300.

The system also comprises a source measurement unit (SMU)342comprising a direct current (DC) voltage source343and a DC voltmeter345. As described more fully below, the SMU342measures current through the second resistor310, and the voltage applied to maintain balance between the first output314and second output318by providing a third voltage to the second input316. As will be appreciated, by having a measure of both the current through and voltage across the second resistor310, a measure of the power needed to maintain the balanced state between the first output314and second output318. As described more fully below, the power required to maintain the balanced state is substantially equal to the output power of the source. This balanced state and the power measurements are effected by a computer system350. The computer system350is adapted to receive measurements from the first DMM340, and thus from the first and second outputs314,318, and stores and processes the measurements data according to representative embodiments described herein. The computer system350comprises a controller352, a processor354, a memory356, and a display358which may in turn comprise a graphical user interface (GUI) (not shown), and a user interface359.

The memory356stores instructions executable by the processor354of the controller352. When executed, and as described more fully below, the instructions cause the processor to adjust the power on the DC side to return the balanced state between the first output314and the second output318. Moreover, and again as discussed more fully below, the processor354is adapted to receive voltage and current data from the SMU342to determine the power output from the electrical circuit330.

The memory356may include a main memory and/or a static memory, where such memories may communicate with each other and the controller352via one or more buses. The memory356stores instructions used to implement some or all aspects of methods and processes described herein.

The memory356may be implemented by any number, type and combination of random access memory (RAM) and read-only memory (ROM), for example, and may store various types of information, such as software algorithms, which serves as instructions, which when executed by a processor cause the processor to perform various steps and methods according to the present teachings. Furthermore, updates to the methods and processes described herein may also be provided to the computer system350and stored in memory356.

The various types of ROM and RAM may include any number, type and combination of computer readable storage media, such as a disk drive, flash memory, an electrically programmable read-only memory (EPROM), an electrically erasable and programmable read only memory (EEPROM), registers, a hard disk, a removable disk, tape, compact disk read only memory (CD-ROM), digital versatile disk (DVD), floppy disk, Blu-ray disk, a universal serial bus (USB) drive, or any other form of storage medium known in the art. The memory130is a tangible storage medium for storing data and executable software instructions, and is non-transitory during the time software instructions are stored therein. As used herein, the term “non-transitory” is to be interpreted not as an eternal characteristic of a state, but as a characteristic of a state that will last for a period. The term “non-transitory” specifically disavows fleeting characteristics such as characteristics of a carrier wave or signal or other forms that exist only transitorily in any place at any time. The memory356may store software instructions and/or computer readable code (collectively referred to as ‘instructions’) that enable performance of various functions of the system300. The memory356may be secure and/or encrypted, or unsecure and/or unencrypted.

“Memory” is an example of computer-readable storage media, and should be interpreted as possibly being multiple memories or databases. The memory or database for instance may be multiple memories or databases local to the computer, and/or distributed amongst multiple computer systems or computing devices, or disposed in the ‘cloud’ according to known components and methods. A computer readable storage medium is defined to be any medium that constitutes patentable subject matter under 35 U.S.C. § 101 and excludes any medium that does not constitute patentable subject matter under 35 U.S.C. § 101. Examples of such media include non-transitory media such as computer memory devices that store information in a format that is readable by a computer or data processing system. More specific examples of non-transitory media include computer disks and non-volatile memories.

The controller352is representative of one or more processing devices, and is configured to execute software instructions stored in memory356to perform functions as described in the various embodiments herein. The processor354may be implemented by field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), systems on a chip (SOC), a general purpose computer, a central processing unit, a computer processor, a microprocessor, a graphics processing unit (GPU), a microcontroller, a state machine, programmable logic device, or combinations thereof, using any combination of hardware, software, firmware, hard-wired logic circuits, or combinations thereof. Additionally, any processing unit or processor herein may include multiple processors, parallel processors, or both. Multiple processors may be included in, or coupled to, a single device or multiple devices.

The term “processor” as used herein encompasses an electronic component able to execute a program or machine executable instruction. References to a computing device comprising “a processor” should be interpreted to include more than one processor or processing core, as in a multi-core processor. A processor may also refer to a collection of processors within a single computer system or distributed among multiple computer systems, such as in a cloud-based or other multi-site application. The term computing device should also be interpreted to include a collection or network of computing devices each including a processor or processors. Modules have software instructions to carry out the various functions using one or multiple processors that may be within the same computing device or which may be distributed across multiple computing devices.

Referring again to the computer system350and the SMU342, the adjustment of the voltage on the DC side of the system300caused by changes in thermal energy to return the first and second outputs to a balanced state, and to determine the power from the electrical circuit330are described.

As noted above, a change in the ambient temperature will result in a substantially identical change of VTH1and VTH2, and the voltage across the first and second outputs314,318is returned to the balanced state.

By contrast, and as described above, a change in temperature on the RF side of the system300causes a change in the voltage drop VTH1, and a commensurate change in the balance state of the first and second outputs314,318. This is measured by the first DMM340. By applying a voltage to the DC side, the voltage differential between the first and second outputs314,318can be restored to the balanced state. This voltage is applied by the DC voltage source343through connections6and5, which are connected to contacts347and349. Notably, instructions stored in memory356are executed by the processor354to determine the required voltage to return the apparatus to the balanced state, and to change the voltage applied to the second input by this required voltage amount. In this way, changes in the voltage across the first and second outputs314,318caused by changes in thermal energy from the electrical circuit330, can be accounted for, and return the system300to the balanced state. Stated somewhat differently, a change in the voltage across the first and second outputs314,318to an unbalanced state is returned to a balanced state after calculations by the processor354executing instructions stored in memory356, and application of a new voltage from the DC voltage source343of the SMU342through the connection between the computer system350and the SMU342. Notably, however, the change in voltage caused by an increase in temperature on the RF side caused by operation of electrical circuit330is also measured by the second DMM340connected through connections2,3to the first and second outputs314,318. Notably, it is also possible to use data from the second DMM344to established the balanced state between first and second contacts314,318in a DC substitution measurement method. As such, the reading from the second DMM344can also be used to measure the RF power from the electrical circuit330based on a lookup table or conversion table stored in memory356. The processor354can thus determine the RF power from the electrical circuit330by accessing this lookup table or conversion chart. Changes in the thermal energy caused by changes in electrical power from the electrical circuit330are measured as follows. As noted above, a change in the output power from the electrical circuit330will result in a change in the thermal energy from the first resistor308, and the voltage VTH1across the first device correspondingly changes. This results in a change in the voltage across the first and second outputs314,318, which is measured by the first DMM340. Again, instructions stored in memory356are executed by the processor354to determine the required voltage to return the apparatus to the balanced state, and to change the voltage applied to the second input by this required voltage amount. In this way, changes in the voltage across the first and second outputs314,318caused by changes in the power output from the electrical circuit330(and the commensurate change in the voltage VTH1caused by the change in thermal energy from the electrical circuit330) can be accounted for, and return the system300to the balanced state. Notably, the SMU further comprises ammeter341and DC voltmeter345. The ammeter341and the DC voltmeter345are connected at contacts346,348, and as shown from the connections5and6respectively, measure the voltage and current through the second resistor310. Based on these readings a change in the power on the DC side required to return the system to the balanced state between the first and second outputs is determined. Because the first and second devices304,306, the first and second resistors308,310are substantially identical, the change in the power across the DC side is substantially the same as the power across the RF side. So, by determining the power across the DC side, the power across the RF side is readily determined. Again, these determinations may be made by the processor354executing instructions stored in memory356.

While representative embodiments are disclosed herein, one of ordinary skill in the art appreciates that many variations that are in accordance with the present teachings are possible and remain within the scope of the appended claim set. The invention therefore is not to be restricted except within the scope of the appended claims.