Cold source based noise figure measurement using S-parameters and a vector signal transceiver/vector signal analyzer/spectrum analyzer
The noise figure for a radio frequency device may be obtained through power measurements. A signal flow graph based upon the S-parameter information of the entire RF system may be constructed. The S-parameter information may be representative of the microwave termination, the device, the measurement instrument and any losses due to additional components such as connecting cables/attenuators/switches, etc. The signal flow graph includes proper placement and values of the source nodes corresponding to each RF sub-system enumerated above. Noise figure measurements may include a calibration step and a measurement step. During the calibration step the noise figure and the noise temperature of the measurement instrument used for the measurement may be obtained. During the measurement step, the noise figure and the noise temperature of the device may be obtained based at least on the noise figure and noise temperature of the measurement instrument obtained during the calibration step.
1. A method for determining a noise figure for a radio frequency (RF) device, using a measurement instrument, the method comprising:
measuring a first noise power when the RF device is not connected to the measurement instrument;
determining a noise figure and noise temperature of the measurement instrument based at least on the measured first noise power and a first signal flow model representation of a signal measurement path exclusive of the RF device;
measuring a second noise power when the RF device is connected to the measurement instrument; and
determining a noise figure of the RF device based at least on the measured second noise power, the noise figure and noise temperature of the measurement instrument and a second signal flow model representative of the signal measurement path inclusive of the RF device.
2. The method of claim 1 , wherein said measuring the first noise power and said measuring the second noise power are performed for a first termination coupled to an input of the measurement instrument and having a specified first impedance.
3. The method of claim 2 , further comprising performing at least one of the following, prior to said measuring the first noise power:
obtaining a reflection coefficient value of the first termination;
obtaining S parameters corresponding to intermediary components comprised in the measurement system between the termination and the measurement instrument; or
obtaining a reflection coefficient value of the measurement instrument.
4. The method of claim 3 , wherein said determining the noise figure and the noise temperature of the measurement instrument comprises determining the noise figure and the noise temperature of the measurement based on at least one of the following:
the obtained reflection coefficient value of the first termination;
the obtained S parameters; or
the obtained reflection coefficient value of the measurement instrument.
5. The method of claim 1 , wherein the first noise power is representative of a superposition of:
available power corresponding to a first termination coupled to an input of the measurement instrument and having a specified first impedance;
available power corresponding to intermediary components comprised in the measurement system between the termination and the measurement instrument; and
noise power associated with the measurement instrument.
6. The method of claim 1 , wherein the second noise power is representative of a superposition of:
available power corresponding to a first termination coupled to an input of the measurement instrument and having a specified first impedance;
available power corresponding to power loss at an input of the RF device;
available power corresponding to power loss at the RF device;
available power corresponding to power loss at an output of the RF device; and
noise power associated with the measurement instrument.
7. The method of claim 6 , wherein said determining the noise figured of the RF device comprises calculating the noise figure of the RF device according to the second signal flow model from:
the measured second noise power;
the available power corresponding to the first termination;
the available power corresponding to the power loss at the input of the RF device;
the available power corresponding to the power loss at the RF device;
the available power corresponding to the power loss at the output of the RF device; and
the noise power associated with the measurement instrument.
8. A measurement system comprising:
a measurement instrument configured to couple to a device under test (DUT); and
a processing unit configured to interoperate with the measurement instrument to:
measure a first noise power when the DUT is not connected to the measurement instrument;
determine a noise figure and noise temperature of the measurement instrument based at least on the measured first noise power and a first signal flow model representative of a signal measurement path exclusive of the DUT;
measure a second noise power when the DUT is connected to the the measurement instrument; and
determine a noise figure of the DUT based at least on the measured second noise power, the noise figure and noise temperature of the measurement instrument and a second signal flow model representative of the signal measurement path inclusive of the DUT.
9. The measurement system of claim 8 , further comprising:
a first power source configured to provide power to the measurement instrument and having a specified first impedance.
10. The measurement system of claim 9 , further comprising:
intermediary components coupling the first power source to the measurement instrument;
wherein the processing unit is configured to interoperate with the measurement instrument to:
obtain a reflection coefficient value of the first power source;
obtain S parameters corresponding to the intermediary components; and
obtain a reflection coefficient value of the measurement instrument.
11. The measurement system of claim 10 , wherein the processing unit is configured to interoperate with the measurement instrument to:
determine the noise figure and the noise temperature of the measurement instrument based in addition on at least one of the following:
the obtained reflection coefficient value of the first power source;
the obtained S parameters; or
the obtained reflection coefficient value of the measurement instrument.
12. The measurement system of claim 8 , wherein first noise power is representative of a superposition of:
available power corresponding to a first power source coupled to an input of the measurement instrument and having a specified first impedance;
available power corresponding to intermediary components coupling the first power source to the measurement instrument; and
noise power associated with the measurement instrument.
13. The measurement system of claim 8 , wherein the second noise power is representative of a superposition of:
available power corresponding to a first power source coupled to an input of the measurement instrument and having a specified first impedance;
available power corresponding to power loss at an input of the DUT coupled to the output of the measurement instrument;
available power corresponding to power loss at the DUT;
available power corresponding to power loss at an output of the DUT; and
noise power associated with the measurement instrument.
14. The measurement system of claim 13 , wherein the processing unit is configured to interoperate with the measurement instrument to calculate the noise figure of the DUT according to the second signal flow model from:
the measure second noise power;
the available power corresponding to the first power source;
the available power corresponding to the power loss at the input of the DUT;
the available power corresponding to the power loss at the DUT;
the available power corresponding to the power loss at the output of the DUT; and
the noise power associated with the measurement instrument.
15. A measurement system for measuring a noise factor of a device under test (DUT), the measurement system comprising:
a non transitory memory element storing data; and
a processing unit configured to use at least a portion of the data to interoperate with a measurement instrument to:
measure a first noise power when the DUT is not connected to the measurement instrument;
determine a noise figure and noise temperature of the measurement instrument based at least on the measured first noise power and a first signal flow model representative of a signal measurement path exclusive of the DUT;
measure a second noise power when the DUT is connected to the measurement instrument; and
determine a noise figure of the DUT based at least on the measured second noise power, the noise figure and noise temperature of the measurement instrument and a second signal flow model representative of the signal measurement path inclusive of the DUT.
16. The measurement system of claim 15 , further comprising:
a termination coupled to an input of the measurement instrument and having a specified impedance.
17. The measurement system of claim 16 , further comprising:
intermediary components coupling the termination to the input of the measurement instrument;
wherein the processing unit is configured to interoperate with the measurement instrument to:
obtain a reflection coefficient value of the termination;
obtain S parameters corresponding to the intermediary components; and
obtain a reflection coefficient value of the measurement instrument.
18. The measurement system of claim 16 , wherein the processing unit is configured to interoperate with the measurement instrument to:
determine the noise figure and the noise temperature of the measurement instrument based in addition on at least one of the following:
the obtained reflection coefficient value of the termination;
the obtained S parameters; or
the obtained reflection coefficient value of the measurement instrument.
19. The measurement system of claim 15 , wherein first noise power is representative of a superposition of:
available power corresponding to a termination coupled to an input of the measurement instrument and having a specified first impedance;
available power corresponding to intermediary components coupling the termination to the input of the measurement instrument; and
noise power associated with the measurement instrument.
20. The measurement system of claim 15 , wherein the second noise power is representative of a superposition of:
available power corresponding to a termination coupled to an input of the measurement instrument and having a specified first impedance;
available power corresponding to power loss at an input of the DUT coupled to the output of the measurement instrument;
available power corresponding to power loss at the DUT;
available power corresponding to power loss at an output of the DUT; and
noise power associated with the measurement instrument.
21. The measurement system of claim 20 , wherein the processing unit is configured to interoperate with the measurement instrument to calculate the noise figure of the DUT according to the second signal flow model from:
the measured second noise power;
the available power corresponding to the termination;
the available power corresponding to the power loss at the input of the DUT;
the available power corresponding to the power loss at the DUT;
the available power corresponding to the power loss at the output of the DUT; and
the noise power associated with the measurement instrument.