Patent ID: 7505141

Claim:
An interferometric apparatus for producing an output signal characteristic of phase and/or amplitude noise of a device under test, an input signal being provided to the interferometric apparatus, comprising: a. signal generation means arranged to produce a third signal having a carrier frequency offset from that of the input signal; b. a first bridge having first and second arms, the first and second arms having input thereto first and second signals, respectively, produced from one of the input signal or the third signal; c. the device under test being provided in one of the first or second arms of the first bridge; d. carrier suppression means connected to the first and second arms of the first bridge to produce a carrier suppressed signal; e. a first amplifier arranged to amplify the carrier suppressed signal; f. first mixing means responsive to the third signal and to the carrier suppressed signal to produce a signal characteristic of phase and/or amplitude noise of the device under test at an offset frequency.