Incremental method and system for absolute measurement of coherent power at millimeter and submillimeter wavelengths
AssigneeThe United States of America as represented by the Secretary of the Army
InventorsAbraham Singer, Jan M. Minkowski
Life of this patent
Estimating the term…
Abstract
A method and system for making absolute measurements of coherent rf power is described. The method surmounts the primary shortcoming of the other existing methods in that it permits absolute measurement of power at all radio frequencies, whereas the other methods are inherently frequency limited, with the current upper limit being about 75 GHz. This major advantage stems from the fact that this method utilizes a direct comparison of the unknown rf power with a primary standard, whereas all other methods require a conversion of the power to heat before making the comparison.
Claims10
A method for measuring coherent rf power from an rf source having its output connected to a mixer and an i.f. pre-amplifier, the steps comprising:
- measuring the noise factor of a system to which the source is connected;
- measuring the noise factor of the i.f. pre-amplifier;
- measuring the noise temperature ratio of the mixer;
- measuring the i.f. conductance of the output of the mixer;
- measuring the changes in dc current from the mixer as a result of changes in rf power from the source;
- and
- calculating the absolute coherent rf power in accordance with ##EQU6## where P.sub.o is the rf power at the plane of the mixer;
- .DELTA.I is the change in dc current from the mixer;
- F.sub.T is system noise factor;
- F.sub.IF is the i.f. pre-amplifier noise factor;
- g.sub.b is i.f. conductance;
- and
- t is the noise temperature ratio of the mixer.
In a system for performing measurements of quantities of coherent rf power from an rf source, a network for determining system noise factor comprising:
- rf mixing means connected in circuit to the output of the source for generating an output signal from the mixing means;
- i.f. amplifying means for amplifying the i.f. content of the output signal;
- switching means connected to the output of the mixing means for selectively connecting this output to the i.f. amplifying means, in a first switching position;
- means selectively connected to the input of the mixing means for introducing thereto a source of noise;
- and
- means connected in circuit to the output of the amplifying means for determining the system noise factor.
A system for performing measurements of quantities of coherent rf power from an rf source, the system comprising:
- a network for determining a system noise factor, the network including:
- rf mixing means connected in circuit to the output of the source for generating an output signal from the mixing means;
- i.f. amplifying means for amplifying the i.f. content of the output signal;
- switching means connected to the output of the mixing means for selectively connecting this output to the i.f. amplifying means, in a first switching position;
- means selectively connected to the input of the mixing means for introducing thereto a source of noise;
- and
- means connected in circuit to the output of the amplifying means for determining the system noise factor;
- variable impedance means selectively connected with the input of the amplifying means for determining the noise temperature ratio of the mixing means;
- a resistive network selectively connected to the output of the mixing means in a second switching position, for determining the changes in dc current from the mixing means with rf input power being applied from the source.
Dependencies are inferred from the claim text.