US 4,048,568 AGranted

Wide operating frequency range superheterodyne FM noise analyzer

AssigneeThe United States of America as represented by the Secretary of the Army

InventorsGustaf J. Rast, Jr., Thomas A. Barley, Raiford L. Hammond, James R. Ashley

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Abstract

It is desirable to be able to measure the FM noise spectra of signals whose arrier power is less than the minimum power level at which a direct non-amplified analyzer can operate satisfactorily. Generally a carrier less than approximately + 2 dbm would require analysis by a very low power measuring system. In the superheterodyne analyzer the discrimination process for a high frequency input signal is accomplished at a suitable intermediate frequency. A single set of discrimination equipment is utilized in the measurement of a wide carrier frequency range of input signals using relatively narrow band intermediate frequency hardware to optimize the analysis function. This provides a means for measuring frequencies from 4 GHz to 8 GHz or from 2 MHz to 2 GHz for example, with high accuracy and sensitivity, while using the same intermediate frequency hardware limited to operational bandwidths of a few MHz. A balanced phase detector, power dividers, attenuators coupled with an optimum length transmission line and balanced mixing of signal and reference signals at an IF level coupled with frequency translation provide frequency discrimination over a wide carrier frequency range.

Claims8

Dependent claims

A wide operating frequency range analyzer for measuring input carrier frequency signals of very low signal level comprising:

first and second power dividers each having an input and first and second outputs, the input of said first divider being coupled to receive said input carrier signals;
first and second balanced mixers each having first and second inputs and an output, the first input of said first mixer being coupled to the first output of said first divider, the second input of said first mixer being connected to the first output of said second divider, the first input of said second mixer being coupled to the second output of said second power divider and the second input of said second mixer being coupled to the second output of said first power divider for providing superheterodyne mixing of signals coupled thereto;
oscillator means coupled to said second power divider input for providing a local oscillation signal thereto;
quadrature detection means having first and second inputs and an output, said second input being coupled to the output of said second mixer, the output of said detection means being disposed to couple output signals therefrom;
discriminator means coupled between the output of said first mixer and the first input of said detection means;
and wave analyzer means coupled to receive said detection means output signals.

3 more elements

Dependencies are inferred from the claim text.