Apparatus and method for determining single sideband noise figure from double sideband measurements

Claim 1

Apparatus for determining the single sideband noise figure for a device under test at a given RF measurement frequency, comprising: a noise source having an output; a mixer having a first input, a second input, and an output; a device under test having an input connected to the output of the noise source and an output connected to the first input of the mixer; a local oscillator for generating a variable frequency local oscillator signal, the local oscillator having an output connected to the second input of the mixer; a tunable intermediate frequency receiver having an input connected to the output of the mixer for measuring the output noise power of the device under test; and a controller connected to the local oscillator and the receiver; the local oscillator being controlled by the controller to separately produce three local oscillator signals comprising a first local oscillator signal having a frequency on the high side of the given RF measurement frequency, a second local oscillator signal having a frequency on the low side of the given RF measurement frequency, and a third local oscillator signal having a frequency at the given RF measurement frequency; the receiver being controlled by the controller to measure a first output noise power of the device under test at a first predetermined intermediate frequency when the local oscillator produces the first local oscillator signal, a second output noise power of the device under test at the first predetermined intermediate frequency when the local oscillator produces the second local oscillator signal, and a third output noise power of the device under test at a second predetermined intermediate frequency equal to twice the first intermediate frequency when the local oscillator produces the third local oscillator signal; and the controller for combining the first, second, and third output noise power measurements for cancelling image noise power to provide a single sideband noise figure measurement for the device under test.

Claim 8

A method for determining the single sideband noise figure for a device under test at a given RF measurement frequency (RF), comprising the steps of: connecting an input of a device under test to an output of a noise source; connecting an output of the device under test to a first input of a mixer; connecting a local oscillator to a second input of the mixer; connecting an output of the mixer to a tunable intermediate frequency receiver; producing a first local oscillator signal having a frequency on the high side of the given RF measurement frequency; selecting a first receiver intermediate frequency (IF 1 ) such that two measured sidebands occur at the given RF measurement frequency and at RF+2IF 1 ; measuring with the receiver a first output noise power of: N.sub.1 =(FGN.sub.i).sub.RF +(FGN.sub.i).sub.RF+2IF.sbsb.1 while the first local oscillator signal is produced and the first receiver intermediate frequency is selected; producing a second local oscillator signal having a frequency on the low side of the given RF measurement frequency; selecting the first receiver intermediate frequency (IF 1 ) such that two measured sidebands occur at the given RF measurement frequency and at RF-2IF 1 ; measuring with the receiver a second output noise power of: N.sub.2 =(FGN.sub.i).sub.RF +(FGN.sub.i).sub.RF-2IF.sbsb.1 while the second local oscillator signal is produced and the first receiver intermediate frequency is selected; producing a third local oscillator signal having a frequency equal to the given RF measurement frequency; selecting a second receiver intermediate frequency (IF 2 ) as twice the first intermediate frequency (IF 2 =2×IF 1 ) such that two measured sidebands occur at RF+2IF 1 and RF-2IF 1 ; measuring with the receiver a third output noise power of: N.sub.3 =(FGN.sub.i).sub.RF+2IF.sbsb.1 +(FGN.sub.i).sub.RF-2IF.sbsb.1 while the third local oscillator signal is produced and the second receiver intermediate frequency is selected; combining the first, second, and third noise power measurements by adding the first and second and subtracting the third: N.sub.1 +N.sub.2 -N.sub.3 =2(FGN.sub.i).sub.RF to eliminate the power from unwanted sidebands and leave only the noise power at the given RF measurement frequency; and determining the single sideband noise figure for the device under test as: ##EQU8## where N i represents noise power input and G represents the gain of the device under test.

Claim 9

A method for determining the single sideband noise figure for a device under test at a given RF measurement frequency (RF), comprising the steps of: connecting an input of a device under test to an output of a noise source; connecting an output of the device under test to a first input of a mixer; connecting a local oscillator to a second input of the mixer; connecting an output of the mixer to a tunable intermediate frequency receiver; producing a first local oscillator signal having a frequency on the high side of the given RF measurement frequency; selecting a first receiver intermediate frequency (IF 1 ) such that two measured sidebands occur at the given RF measurement frequency and at RF+2IF 1 ; measuring with the receiver a first output noise power of: N.sub.1 =(FGN.sub.i).sub.RF +(FGN.sub.i).sub.RF+2IF.sbsb.1 while the first local oscillator signal is produced and the first receiver intermediate frequency is selected; producing a second local oscillator signal having a frequency on the low side of the given RF measurement frequency; selecting the first receiver intermediate frequency (IF 1 ) such that two measured sidebands occur at the given RF measurement frequency and at RF-2IF 1 ; measuring with the receiver a second output noise power of: N.sub.2 =(FGN.sub.i).sub.RF +(FGN.sub.i).sub.RF-2IF.sbsb.1 while the second local oscillator signal is produced and the first receiver intermediate frequency is selected; producing a third local oscillator signal having a frequency equal to the given RF measurement frequency; selecting a second receiver intermediate frequency (IF 2 ) as twice the first intermediate frequency (IF 2 =2×IF 1 ) such that two measured sidebands occur at RF+2IF 1 and RF-2IF 1 ; measuring with the receiver a third output noise power of: N.sub.3 =(FGN.sub.i).sub.RF+2IF.sbsb.1 +(FGN.sub.i).sub.RF-2IF.sbsb.1 while the third local oscillator signal is produced and the second receiver intermediate frequency is selected; combining the first, second, and third noise power measurements by adding the first and second and subtracting the third: N.sub.1 +N.sub.2 -N.sub.3 =2(FGN.sub.i).sub.RF to eliminate the power from unwanted sidebands and leave only the noise power at the given RF measurement frequency; and determining the single sideband noise figure for the device under test as: ##EQU8## where N i represents noise power input and G represents the gain of the device under test.

Claim 13

A method for determining the single sideband noise figure for a device under test at a given RF measurement frequency (RF), comprising the steps of: measuring S-parameters of a device under test with a vector network analyzer; measuring S-parameters of the isolator with the vector network analyzer; measuring an output reflection coefficient of the noise source in hot and cold states with the vector network analyzer; connecting an input of an isolator to an output of a noise source and an output of the isolator to a first input of a mixer; connecting a local oscillator to a second input of the mixer; connecting an output of the mixer to a tunable intermediate frequency receiver; producing a first local oscillator signal having a frequency on the high side of the given RF measurement frequency; selecting a first receiver intermediate frequency (IF 1 ) such that two measured sidebands occur at the given RF measurement frequency and at RF+2IF 1 ; performing with the receiver a first hot calibration measurement (N H1 ): N.sub.H1 =[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF +[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF+2IF.sbsb.1 performing with the receiver a first cold calibration measurement (N C1 ): N.sub.C1 =[(kBT.sub.C +kBT.sub.R)G.sub.R (0)M.sub.C ].sub.RF +[(kBT.sub.C +kBT.sub.R)G.sub.R (0)M.sub.C ].sub.RF+2IF.sbsb.1 connecting an input of the device under test to the output of the noise source and an output of the device under test to the input of the isolator; performing with the receiver a first output noise power measurement (N MEAS1 ): N.sub.MEAS1 =[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF +[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF+2IF.sbsb.1 disconnecting the input of the device under test from the output of the noise source and the output of the device under test from the first input of the mixer; connecting the output of the noise source to the input of the isolator; producing a second local oscillator signal having a frequency on the low side of the given RF measurement frequency; selecting the first receiver intermediate frequency (IF 1 ) such that two measured sidebands occur at the given RF measurement frequency and at RF-2IF 1 ; performing with the receiver a second hot calibration measurement N H2 ): N.sub.H2 =[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF +[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF-2IF.sbsb.1 performing with the receiver a second cold calibration measurement (N C2 ): N.sub.MEAS2 =[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBt.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF +[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF-2IF.sbsb.1 connecting the input of the device under test to the output of the noise source and the output of the device under test to the input of the isolator; performing with the receiver a second output noise power measurement (N MEAS2 ): N.sub.MEAS2 =[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBt.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF +[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF-2IF.sbsb.1 disconnecting the input of the device under test from the output of the noise source and the output of the device under test from the first input of the mixer; connecting the output of the noise source to the input of the isolator; producing a third local oscillator signal having a frequency equal to the given RF measurement frequency; selecting a second receiver intermediate frequency (IF 2 ) chosen as twice the first intermediate frequency (IF 2 =2×IF 1 ) such that two measured sidebands occur at RF+2IF 1 and RF-2IF 1 ; performing with the receiver a third hot calibration measurement (N H3 ): N.sub.H3 =[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF+2IF.sbsb.1 +[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF-2IF.sbsb.1 performing with the receiver a third cold calibration measurement (N C3 ): N.sub.C3 =[(kBT.sub.C +kBT.sub.R)G.sub.R (0)M.sub.C ].sub.RF+2IF.sbsb.1 +[(kBT.sub.C +kBT.sub.R)G.sub.R (0)M.sub.C ].sub.RF-2IF.sbsb.1 connecting the input of the device under test to the output of the noise source and the output of the device under test to the input of the isolator; performing with the receiver a third output noise power measurement (N MEAS3 ): N.sub.MEAS3 =[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF+2IF.sbsb.1 +[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF-2IF.sbsb.1 and determining the single sideband noise figure for the device under test as: ##EQU9## where N MEAS =N MEAS1 +N MEAS2 -N MEAS3 , N H =N H1 +N H2 -N H3 , N C =N C1 +N C2 -N C3 , G R (0) is the available gain of the receiver when a reflection coefficient of zero is connected to the receiver input, T H and T C =T 0 are the temperatures of the noise source in its hot and cold states, T R and T E are the effective input noise temperatures of the receiver and the device under test, respectively, G DUT is the available gain of the device under test at a particular frequency and is calculated from its S-parameters and the noise source output reflection coefficient using the relationship: ##EQU10## B represents the measurement bandwidth, and k is Boltzmann's constant.

Claim 14

A method for determining the single sideband noise figure for a device under test at a given RF measurement frequency (RF), comprising the steps of: measuring S-parameters of a device under test with a vector network analyzer; measuring S-parameters of the isolator with the vector network analyzer; measuring an output reflection coefficient of the noise source in hot and cold states with the vector network analyzer; connecting an input of an isolator to an output of a noise source and an output of the isolator to a first input of a mixer; connecting a local oscillator to a second input of the mixer; connecting an output of the mixer to a tunable intermediate frequency receiver; producing a first local oscillator signal having a frequency on the high side of the given RF measurement frequency; selecting a first receiver intermediate frequency (IF 1 ) such that two measured sidebands occur at the given RF measurement frequency and at RF+2IF 1 ; performing with the receiver a first hot calibration measurement (N H1 ): N.sub.H1 =[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF +[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF+2IF.sbsb.1 performing with the receiver a first cold calibration measurement (N C1 ): N.sub.C1 =[(kBT.sub.C +kBT.sub.R)G.sub.R (0)M.sub.C ].sub.RF +[(kBT.sub.C +kBT.sub.R)G.sub.R (0)M.sub.C ].sub.RF+2IF.sbsb.1 connecting an input of the device under test to the output of the noise source and an output of the device under test to the input of the isolator; performing with the receiver a first output noise power measurement (N MEAS1 ): N.sub.MEAS1 =[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF +[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF+2IF.sbsb.1 disconnecting the input of the device under test from the output of the noise source and the output of the device under test from the first input of the mixer; connecting the output of the noise source to the input of the isolator; producing a second local oscillator signal having a frequency on the low side of the given RF measurement frequency; selecting the first receiver intermediate frequency (IF 1 ) such that two measured sidebands occur at the given RF measurement frequency and at RF-2IF 1 ; performing with the receiver a second hot calibration measurement N H2 ): N.sub.H2 =[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF +[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF-2IF.sbsb.1 performing with the receiver a second cold calibration measurement (N C2 ): N.sub.MEAS2 =[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBt.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF +[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF-2IF.sbsb.1 connecting the input of the device under test to the output of the noise source and the output of the device under test to the input of the isolator; performing with the receiver a second output noise power measurement (N MEAS2 ): N.sub.MEAS2 =[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBt.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF +[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF-2IF.sbsb.1 disconnecting the input of the device under test from the output of the noise source and the output of the device under test from the first input of the mixer; connecting the output of the noise source to the input of the isolator; producing a third local oscillator signal having a frequency equal to the given RF measurement frequency; selecting a second receiver intermediate frequency (IF 2 ) chosen as twice the first intermediate frequency (IF 2 =2×IF 1 ) such that two measured sidebands occur at RF+2IF 1 and RF-2IF 1 ; performing with the receiver a third hot calibration measurement (N H3 ): N.sub.H3 =[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF+2IF.sbsb.1 +[(kBT.sub.H +kBT.sub.R)G.sub.R (0)M.sub.H ].sub.RF-2IF.sbsb.1 performing with the receiver a third cold calibration measurement (N C3 ): N.sub.C3 =[(kBT.sub.C +kBT.sub.R)G.sub.R (0)M.sub.C ].sub.RF+2IF.sbsb.1 +[(kBT.sub.C +kBT.sub.R)G.sub.R (0)M.sub.C ].sub.RF-2IF.sbsb.1 connecting the input of the device under test to the output of the noise source and the output of the device under test to the input of the isolator; performing with the receiver a third output noise power measurement (N MEAS3 ): N.sub.MEAS3 =[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF+2IF.sbsb.1 +[[(kBT.sub.C +kBT.sub.E)G.sub.DUT +kBT.sub.R ]G.sub.R (0)M.sub.DUT ].sub.RF-2IF.sbsb.1 and determining the single sideband noise figure for the device under test as: ##EQU9## where N MEAS =N MEAS1 +N MEAS2 -N MEAS3 , N H =N H1 +N H2 -N H3 , N C =N C1 +N C2 -N C3 , G R (0) is the available gain of the receiver when a reflection coefficient of zero is connected to the receiver input, T H and T C =T 0 are the temperatures of the noise source in its hot and cold states, T R and T E are the effective input noise temperatures of the receiver and the device under test, respectively, G DUT is the available gain of the device under test at a particular frequency and is calculated from its S-parameters and the noise source output reflection coefficient using the relationship: ##EQU10## B represents the measurement bandwidth, and k is Boltzmann's constant.