Local oscillator synchronization for coherent phased-array system

A method, comprising:

• generating a plurality of digital reference pulses synchronously according to an RF reference of a master oscillator, wherein a pulse repetition rate of a digital reference pulse of the plurality of digital reference pulses is substantially less than a frequency of the RF reference;
• selectively switching the plurality of digital reference pulses to obtain a plurality of switched digital reference pulses;
• providing the plurality of switched digital reference pulses to a plurality of radio modules operating within a millimeter wave spectrum, each radio module comprising an adjustable LO;
• counting cycles of an LO output signal of the adjustable LO occurring between consecutive pulses of the switched digital reference pulses to obtain a count value;
• determining a difference between the count value and a reference value;
• and
• adjusting the adjustable LO according to the difference to obtain a corrected LO signal, wherein the corrected LO signal is synchronized to the master oscillator.

A multiple input multiple output (MIMO) radio, comprising:

• a plurality of radio modules adapted to operate in a millimeter wave spectrum;
• a master oscillator adapted to provide a radio frequency (RF) reference;
• a digital pulse generator in communication with the master oscillator and adapted to provide a plurality of digital reference pulses based on the RF reference;
• and
• a switch in communication with the digital pulse generator and adapted to provide respective digital reference pulses of the plurality of digital reference pulses to each radio module of the plurality of radio modules, wherein each radio module of the plurality of radio modules comprises:
• a controllable local oscillator (LO) adapted to provide an LO output signal;
• a counter in communication with the switch and the controllable LO, wherein the counter is adapted to count according to the LO output signal and the respective digital reference pulses to obtain a count value;
• and
• a difference detector in communication with the counter and the controllable LO, wherein the difference detector is adapted to determine a difference between the count value and a reference value, wherein the controllable LO is adapted to provide a corrected LO signal responsive to the difference, and wherein the corrected LO signal is coherent with other radio modules of the plurality of radio modules.