Self-calibrating radio frequency calorimeter
Disclosed is a radio frequency (RF) calorimeter having National Metrology Institute (NMI) traceable measurement accuracy with uncertainty of less than about ±0.25%, including the incorporation of a low-frequency reference source integral to the calorimeter for the purpose of self-calibration, a load with very high thermal efficiency, a temperature-controlled load enclosure, a vacuum relay high-power RF switch, an integrated low-frequency reference source, a non-reactive coolant liquid, a liquid-to-liquid heat exchanger, a self-calibration routine that can be performed on demand, and machine learning algorithms to create more accurate data models.
1 . A radio frequency (RF) calorimeter, comprising:
a low-frequency reference source, said low-frequency reference source is integrated into said calorimeter, thereby permitting said calorimeter to self-calibrate using said low-frequency reference source;
a controller configured to self-calibrate said calorimeter on-demand immediately prior to measuring a power value of an RF source having an unknown power;
said calorimeter having a measurement accuracy with an uncertainty of less than about ±0.25%,
wherein said calorimeter uses a silicon oil as a coolant.
2 . The RF calorimeter of claim 1 , wherein said calorimeter is a high-power flow calorimeter capable of maintaining National Metrology Institute (NMI) traceable measurement accuracy at frequencies up to about 3 GHz and power levels up to about 3000 Watts.
3 . The RF calorimeter of claim 1 , further comprising an RF input and a load, said load having a body and an internal resistor located inside of said body, said internal resistor being electrically connected to said RF input, said internal resistor being in thermal contact with a coolant;
said load having a very high thermal efficiency to maximize a transfer of an RF power that is applied to said internal resistor through said RF input into thermal energy in said coolant flowing through said load, wherein said internal resistor converts said RF power to thermal energy and transfers said thermal energy to said coolant in thermal communication with said internal resistor while said coolant is flowing through said load,
thereby minimizing RF power lost by thermal transfer through said body and minimizing RF power lost by thermal transfer through said RF input, said RF power lost through said RF input either lost through a center conductor or an outer conductor of said RF input, thereby no RF power is lost by thermal transfer from the internal resistor through said body of said load to an environment surrounding said body of said load,
wherein said RF calorimeter optionally has a silver plated quartz tube providing mechanical and electrical connection between said RF input and said load,
wherein said RF power lost by thermal transfer through said body and through said RF input contributing to less than about ±0.018% of total system uncertainty.
4 . The RF calorimeter of claim 1 , wherein said controller uses machine learning to generate and update a model of said calorimeter based on continuously acquired sensor data obtained during power measurements, thereby enhancing a predictive accuracy of said calorimeter for power measurements under varying conditions.
5 . The RF calorimeter of claim 1 , wherein said uncertainty of said power measurement of said calorimeter enables a calibration of an RF power measurement device under test to uncertainties of less than about ±0.5%, when said RF power measurement device is calibrated to said calorimeter.
6 . The RF calorimeter of claim 1 , wherein said measurement accuracy of said calorimeter enables an extension of a time between calibrations of an RF power measurement device under test having about ±1% uncertainty or higher when said RF power measurement device under test is calibrated to said calorimeter, since said measurement accuracy of said calorimeter results in an increase in a test accuracy ratio (TAR) between an RF power measurement device under test and said calorimeter.
7 . The calorimeter of claim 1 , wherein said low-frequency reference source being located inside a main enclosure of said calorimeter.
8 . The RF calorimeter of claim 3 , further comprising a temperature-controlled enclosure for the load, said temperature-controlled enclosure isolating said load from changes to an ambient environment of said calorimeter, thereby ensuring that a thermal gradient between a coolant at an inlet of said load and said ambient environment is kept constant to minimize any error associated with said thermal gradient.
9 . The RF calorimeter of claim 3 , wherein said load for converting said RF power to a thermal energy is comprised of one or more individual loads.
10 . The RF calorimeter of claim 3 , further comprising an RF switch, which permits for electrically controlled switching between said low-frequency reference source and said RF source having said unknown power connected to said RF input, said RF switch having an insertion loss between about −0.0025 dB and about −0.0275 dB and return loss between about −40 dB and about −68 db over the frequency of operation, and said RF switch optionally comprises an impedance-matched vacuum relay.
11 . The RF calorimeter of claim 3 , wherein said use of said silicon oil as said coolant permits for an application of DC power to said load without a risk of electro-chemical reactions between said coolant and said load; wherein said coolant is cooled using a liquid-to-liquid heat exchanger which permits for a primary and a secondary cooling circuit, each of said primary and said secondary cooling circuits optionally containing different types of said coolant.
12 . The RF calorimeter of claim 3 ,
wherein said controller self-calibrates said calorimeter using said low-frequency reference source and an RF switch, a position of said RF switch determines whether power from said low-frequency reference source or said RF source is applied to said load,
wherein said controller controls said low-frequency reference source, said RF switch, and said RF source having said unknown power.
13 . A method for making a radio frequency (RF) power measurement using an RF calorimeter, comprising:
providing an RF calorimeter,
said RF calorimeter having a measurement accuracy with an uncertainty of less than about ±0.25%,
said RF calorimeter having a low-frequency reference source integrated into said calorimeter for a purpose of self-calibration;
wherein said RF calorimeter further comprising a controller, said controller self-calibrates said RF calorimeter on-demand immediately prior to measuring a power value of an RF source having an unknown power;
said RF calorimeter having a silicon oil as a coolant;
calibrating said RF calorimeter using said low-frequency reference source; and
measuring said power value of said RF source having said unknown power.
14 . The method of claim 13 , wherein said RF calorimeter is a high-power flow RF calorimeter capable of maintaining National Metrology Institute (NMI) traceable measurement accuracy at frequencies up to about 3 GHz and power levels up to about 3000 Watts.
15 . The method of claim 13 , wherein said RF calorimeter further comprises an RF input and a load, said load having a body and an internal resistor located inside of said body, said internal resistor being electrically connected to said RF input, said internal resistor being in thermal contact with a coolant;
said load having a very high thermal efficiency to maximize a transfer of an RF power that is applied to said internal resistor through said RF input into thermal energy in said coolant flowing through said load, wherein said internal resistor converts said RF power to thermal energy and transfers said thermal energy to said coolant in thermal communication with said internal resistor while said coolant is flowing through said load,
thereby minimizing RF power lost by thermal transfer through said body and minimizing RF power lost by thermal transfer through said RF input, said RF power lost through said RF input either lost through a center conductor or an outer conductor of said RF input, thereby no RF power is lost by thermal transfer from the internal resistor through said body of said load to an environment surrounding said body of said load,
wherein said RF calorimeter optionally has a silver plated quartz tube providing mechanical and electrical connection between said RF input and said load,
wherein said RF power lost by thermal transfer through said body and through said RF input contributing to less than about ±0.018% of total system uncertainty.
16 . The method of claim 15 , wherein said RF calorimeter further comprises a temperature-controlled enclosure for the load, said temperature-controlled enclosure isolating said load from changes to an ambient environment of said calorimeter, thereby ensuring that a thermal gradient between a coolant at an inlet of said load and said ambient environment is kept constant to minimize any error associated with said thermal gradient.
17 . The method of claim 15 , wherein said load for converting said RF power to a thermal energy is comprised of one or more individual loads.
18 . The method of claim 15 , wherein said use of said silicon oil as said coolant permits for an application of DC power to said load without a risk of electro-chemical reactions between said coolant and said load; wherein said coolant is cooled using a liquid-to-liquid heat exchanger which permits for a primary and a secondary cooling circuit, each of said primary and said secondary cooling circuits optionally containing different types of said coolant.
19 . The method of claim 15 ,
wherein said controller self-calibrates said RF calorimeter using said low-frequency reference source and an RF switch, a position of said RF switch determines whether power from said low-frequency reference source or said RF source is applied to said load,
wherein said controller controls said low-frequency reference source, said RF switch, and said RF source having said unknown power.
20 . The method of claim 13 , wherein said RF calorimeter further comprises an RF switch, which permits for electrically controlled switching between said low-frequency reference source and said RF source having said unknown power, said RF switch having an insertion loss between about −0.0025 dB and about −0.0275 dB and return loss between about −40 dB and about −68 dB over the frequency of operation, and said RF switch optionally comprises an impedance-matched vacuum relay.
21 . The method of claim 13 , wherein said controller uses machine learning to generate and update a model of said RF calorimeter based on continuously acquired sensor data obtained during power measurements, wherein said model is used to measure said power value of said RF source, thereby enhancing a predictive accuracy of said RF calorimeter for power measurements under varying conditions.
22 . The method of claim 13 , wherein said uncertainty of said RF power measurement of said RF calorimeter enables a calibration of an RF power measurement device under test to uncertainties of less than about ±0.5%, when said RF power measurement device under test is calibrated to said RF calorimeter.
23 . The method of claim 13 , wherein said measurement accuracy of said RF calorimeter enables an extension of a time between calibrations of an RF power measurement device under test having about ±1% uncertainty or higher when said RF power measurement device under test is calibrated to said RF calorimeter, since said measurement accuracy of said RF calorimeter results in an increase in a test accuracy ratio (TAR) between said RF power measurement device under test and said RF calorimeter.
24 . The method of claim 13 , wherein said low-frequency reference source being located inside a main enclosure of said calorimeter.
25 . A radio frequency (RF) calorimeter comprising:
a low-frequency reference source integral to the RF calorimeter for a purpose of self-calibration, said RF calorimeter having a silicon oil as a coolant;
a controller having a processor and a memory;
said memory storing executable code when executed by the processor performs actions comprising:
calibrating said RF calorimeter using said low-frequency reference source on-demand immediately prior to measuring a power value of an RF source having an unknown power; and
measuring said power value of said RF source having said unknown power;
said RF calorimeter having a measurement accuracy with an uncertainty of less than about ±0.25%.
26 . The RF calorimeter of claim 25 , wherein said calorimeter is a high-power flow calorimeter capable of maintaining National Metrology Institute (NMI) traceable measurement accuracy at frequencies up to about 3 GHz and power levels up to about 3000 Watts.
27 . The RF calorimeter of claim 25 , wherein said calorimeter further comprises an RF input and a load, said load having a body and an internal resistor located inside of said body, said internal resistor being electrically connected to said RF input, said internal resistor being in thermal contact with a coolant;
said load having a very high thermal efficiency to maximize a transfer of an RF power that is applied to said internal resistor through said RF input into thermal energy in said coolant flowing through said load, wherein said internal resistor converts said RF power to thermal energy and transfers said thermal energy to said coolant in thermal communication with said internal resistor while said coolant is flowing through said load,
thereby minimizing RF power lost by thermal transfer through said body and minimizing RF power lost by thermal transfer through said RF input, said RF power lost through said RF input either lost through a center conductor or an outer conductor of said RF input, thereby no RF power is lost by thermal transfer from the internal resistor through said body of said load to an environment surrounding said body of said load,
wherein said RF calorimeter optionally has a silver plated quartz tube providing mechanical and electrical connection between said RF input and said load,
wherein said RF power lost by thermal transfer through said body and through said RF input contributing to less than about ±0.018% of total system uncertainty.
28 . The RF calorimeter of claim 27 , wherein said calorimeter further comprises a temperature-controlled enclosure for the load, said temperature-controlled enclosure isolating said load from changes to an ambient environment of said calorimeter, thereby ensuring that a thermal gradient between said coolant at an inlet of said load and said ambient environment is kept constant to minimize any error associated with said thermal gradient.
29 . The RF calorimeter of claim 27 , wherein said load for converting said RF power to a thermal energy is comprised of one or more individual loads.
30 . The RF calorimeter of claim 27 , wherein said use of said silicon oil as said coolant, which permits for an application of DC power to said load without a risk of electro-chemical reactions between said coolant and said load; wherein said coolant is cooled using a liquid-to-liquid heat exchanger which permits for a primary and a secondary cooling circuit, each of said primary and said secondary cooling circuits optionally containing different types of said coolant.
31 . The RF calorimeter of claim 27 ,
wherein said controller self-calibrates said calorimeter using said low-frequency reference source and an RF switch, a position of said RF switch determines whether power from said low-frequency reference source or said RF source is applied to said load,
wherein said controller controls said low-frequency reference source, said RF switch, and said RF source having said unknown power.
32 . The RF calorimeter of claim 25 , wherein said calorimeter further comprises an RF switch, which permits for electrically controlled switching between said low-frequency reference source and said RF source having said unknown power, said RF switch having an insertion loss between about −0.0025 dB and about −0.0275 dB and return loss between about −40 dB and about −68 dB over the frequency of operation, and said RF switch optionally comprises an impedance-matched vacuum relay.
33 . The RF calorimeter of claim 25 , wherein said controller uses machine learning to generate and update a model of said calorimeter based on continuously acquired sensor data obtained during power measurements, wherein said model is used to measure said power value of said RF source, thereby enhancing a predictive accuracy of said calorimeter for power measurements under varying conditions.
34 . The RF calorimeter of claim 25 , wherein said uncertainty of said power measurement of said calorimeter enables a calibration of an RF power measurement device under test to uncertainties of less than about ±0.5%, when said RF power measurement device is calibrated to said calorimeter.
35 . The RF calorimeter of claim 25 , wherein said measurement accuracy of said calorimeter enables an extension of a time between calibrations of an RF power measurement device under test having about ±1% uncertainty or higher when said RF power measurement device is calibrated to said calorimeter, since said measurement accuracy of said calorimeter results in an increase in a test accuracy ratio (TAR) between said RF power measurement device under test and said calorimeter.
36 . The RF calorimeter of claim 25 , wherein said low-frequency reference source being located inside a main enclosure of said calorimeter.