Available Technology

Phase Modulation Noise Reducer

The phase modulation (PM) noise reducer is a novel scheme for lowering the PM noise of an oscillator.  Low PM noise, or phase instability, is among the most important metrics for oscillators used in modern civilian and military applications.

One can sense and correct an oscillator’s PM noise by measuring its PM noise in real time.  However, such measurement requires a higher quality reference oscillator or a stable high-quality factor (Q) element to measure against.  The PM noise reducer is new and much simpler.  It requires a measurement of amplitude modulation (AM) noise only.  Such a measurement is easier than a PM noise measurement, requiring only a reference voltage from, for example, a diode and a few capacitors, rather than a reference oscillator.

The PM noise reducer works by requiring a measurement of a subject oscillator’s PM noise, AM noise, and correlation between them.  The AM noise of the oscillator is measured with an AM detector and a control signal of equal magnitude, same frequency response but opposite phase as the PM noise is generated.  This control signal is then utilized to reduce the PM noise of the oscillator via a feed-forward error correction.

This scheme simultaneously reduces PM noise of an oscillator in steady state as well as under vibration (PM noise of an oscillator degrades under vibration).  This reduction cannot be done with any existing techniques.

The figure below illustrates a PM noise reducer. It is configured to reduce PM noise of oscillator (6). PM noise reducer (2) includes AM detector (4) to receive a primary oscillator signal from oscillator (6) and to produce an AM detector signal based on the primary oscillator signal. The primary oscillator signal can include a first PM noise.  PM noise reducer (2) also includes control circuit (12) in electrical communication with AM detector (4) to receive the AM detector signal and to produce a control signal. Phase shifter (14) is in electrical communication with control circuit (12) and is configured to receive the primary oscillator signal from splitter (8) and the control signal (at phase shifter control port (20)) and to produce a secondary oscillator signal based on the primary oscillator signal and the control signal. Here, the secondary oscillator signal includes a second PM noise that is less than the first PM noise.

Abstract: 

A phase modulation (PM) noise reducer to reduce phase modulation noise of an oscillator, the PM noise reducer including: an amplitude modulation (AM) detector to receive a primary oscillator signal and to produce an AM detector signal based on the primary oscillator signal, the primary oscillator signal including a first phase modulation (PM) noise; a control circuit in electrical communication with the AM detector to receive the AM detector signal and to produce a control signal; a phase shifter in electrical communication with the control circuit to receive the primary oscillator signal and the control signal and to produce a secondary oscillator signal based on the primary oscillator signal and the control signal, the secondary oscillator signal comprising a second PM noise, wherein the second PM noise is less than the first PM noise.

Inventors: 
Archita Hati, Craig Nelson, David Howe
Patent Number: 
10050608
Technology Type(s): 
Homeland Security, Digital Information Access, Manufacturing, Electronics, Precision Measurement
Internal Laboratory Ref #: 
14-033
Patent Issue Date: 
August 14, 2018
Lab Representatives
Share to Facebook Share to Twitter Share to Google Plus Share to Linkedin