US 9,225,507 B1 · System and method for synchronizing local oscillators

Abstract

Provided is a method and apparatus for aligning a first local oscillator (LO) clock generated by a controllable LO clock generator in a first radio frequency (RF) path with a second LO clock in a second RF path. The apparatus includes a synchronization channel configured to exchange a synchronization clock between the first and second RF paths, a phase detector configured to measure a phase alignment between the first and second LO clocks, and a loop filter configured to drive the controllable LO clock generators using the phase alignment. Also provided is a time to digital converter. The time to digital converter includes a D flip-flop for sampling first and second input clocks with a third clock, and a counter configured to synchronously increment the resulting samples and create a digital proportional value representing the delay between the first and second clocks.

Claims28

Dependent claims

An apparatus for aligning a first local oscillator (LO) clock generated by a controllable LO clock generator in a first radio frequency (RF) path with a second LO clock in a second RF path, the apparatus comprising:

a synchronization channel utilizing at least one of transmit buffers and receive buffers, the synchronization channel configured to exchange a synchronization clock between the first and second RF paths;
a first phase detector configured to measure a phase alignment between the first and second LO clocks and to generate an output;
a second phase detector configured to measure the phase alignment between the second and first LO clocks and to generate an output;
and
a loop filter configured to drive the controllable LO clock generator using the phase alignments,
wherein:
the first RF path includes the first phase detector,
the second RF path includes the second phase detector,
the outputs from the first and second phase detectors are subtracted at the input of the loop filter,
a true phase relationship between the first and second LO clocks is determined, and
systematic and environmental variability due to the at least one of transmit buffers and receive buffers is cancelled.

8 more elements

A method for aligning a first local oscillator (LO) clock generated by a controllable LO clock generator in a first radio frequency (RF) path with a second LO clock in a second RF path, the method comprising:

exchanging synchronization clocks between the first and second RF paths over a synchronization channel, the synchronization channel utilizing at least one of transmit buffers and receive buffers;
measuring a phase alignment between the first and second LO clocks with a first phase detector and a second phase detector, the first phase detector being included in the first RF path, the second phase detector being included in the second RF path, the measuring of the phase alignment comprising:
subtracting an output from each of the first phase detector and the second phase detector at the input of a loop filter;
determining a true phase relationship between the LO clocks;
and
cancelling systematic and environmental variability due to the at least one of transmit buffers and receive buffers;
and
driving, with the loop filter, the controllable LO clock generator using the phase alignment.

5 more elements

Dependencies are inferred from the claim text.

System and method for synchronizing local oscillators

Life of this patent

System and method for synchronizing local oscillators

Life of this patent

Abstract

Claims28