Apparatuses and methods for a compact, low phase noise tunable radio frequency synthesizer

A radio frequency (RF) synthesizer configured to generate a desired frequency of an RF signal with diminished phase noise, the RF synthesizer comprising:

• a processing circuit configured to receive data indicative of the desired frequency of the RF signal, to determine a third carrier wave frequency and a fourth carrier wave frequency which when mixed generate a mixing product at the desired frequency, using the third carrier wave frequency, to generate a first control signal with a parameter value and a third control signal with a parameter value, and using the fourth carrier wave frequency, to generate a second control signal with a parameter value and a fourth control signal with a parameter value, wherein each of the third and the fourth carrier wave frequencies is selected from a set of stimulated Brillouin scattering (SBS) optical frequencies at which an SBS optical resonator is configured to generate an optical signal;
• a first frequency tunable laser configured to emit a first optical signal at a first carrier wave frequency determined by the parameter value of the first control signal;
• a second frequency tunable laser configured to emit a second optical signal, at a second carrier wave frequency determined by the parameter value of the second control signal;
• a first frequency tunable optical filter configured to receive the first optical signal, wherein a first passband spectrum of the first frequency tunable optical filter is configured to be set, by the parameter value of the third control signal, to include the first carrier wave frequency;
• a second frequency tunable optical filter configured to receive the second optical signal, wherein a second passband spectrum of the second frequency tunable optical filter is configured to be set, by the parameter value of the fourth control signal, to include the second carrier wave frequency;
• the SBS optical resonator configured to receive the first optical signal having the first carrier wave frequency and the second optical signal having the second carrier wave frequency and to emit a portion of the first optical signal having the first carrier wave frequency, a portion of the second optical signal having the second carrier wave frequency, a first SBS optical signal having the third carrier wave frequency, and a second SBS optical signal having the fourth carrier wave frequency;
• wherein the first frequency tunable laser is further configured to receive, through the first frequency tunable optical filter, the portion of the first optical signal having the first carrier wave frequency and to be injection locked;
• wherein the second frequency tunable laser is further configured to receive, through the second frequency tunable optical filter, the portion of the second optical signal having the second carrier wave frequency and to be injection locked;
• and
• an optical mixer configured to generate, using the first SBS optical signal and the second SBS optical signal, generating the mixing product at the desired frequency.

A method of calibrating a radio frequency (RF) signal which includes a processing circuit configured to receive data indicative of a desired frequency of the RF signal, to determine a third carrier wave frequency and a fourth carrier wave frequency which when mixed generate a mixing product at the desired frequency, using the third carrier wave frequency, to generate a first control signal with a parameter value and a third control signal with a parameter value, and using the fourth carrier wave frequency, to generate a second control signal with a parameter value and a fourth control signal with a parameter value, wherein each of the third and the fourth carrier wave frequencies is selected from a set of stimulated Brillouin scattering (SBS) optical frequencies at which an SBS optical resonator is configured to generate an optical signal;

• a first frequency tunable laser configured to emit a first optical signal at a first carrier wave frequency determined by the parameter value of the first control signal;
• a second frequency tunable laser configured to emit a second optical signal, at a second carrier wave frequency determined by the parameter value of the second control signal;
• a first frequency tunable optical filter configured to receive the first optical signal, wherein a first passband spectrum of the first frequency tunable optical filter is configured to be set, by the parameter value of the third control signal, to include the first carrier wave frequency;
• a second frequency tunable optical filter configured to receive the second optical signal, wherein a second passband spectrum of the second frequency tunable optical filter is configured to be set, by the parameter value of the fourth control signal, to include the second carrier wave frequency;
• the SBS optical resonator configured to receive the first optical signal having the first carrier wave frequency and the second optical signal having the second carrier wave frequency and to emit a portion of the first optical signal having the first carrier wave frequency, a portion of the second optical signal having the second carrier wave frequency, a first SBS optical signal having the third carrier wave frequency, and a second SBS optical signal having the fourth carrier wave frequency;
• wherein the first frequency tunable laser is further configured to receive, through the first frequency tunable optical filter, the portion of the first optical signal having the first carrier wave frequency and to be injection locked;
• wherein the second frequency tunable laser is further configured to receive, through the second frequency tunable optical filter, the portion of the second optical signal having the second carrier wave frequency and to be injection locked;
• and an optical mixer configured to generate, using the first SBS optical signal and the second SBS optical signal, generating the mixing product at the desired frequency, the method comprising:
• determining a first trio relationship;
• determining a second trio relationship;
• storing the first and the second trio relationships;
• and
• wherein the first trio relationship includes a parameter value of each of the first control signal and the third control signal, and the third carrier wave frequency of the first SBS optical signal configured to be emitted by the SBS optical resonator when such parameter value of the first control signal is conveyed to the first frequency tunable laser and when such parameter value of the third control signal is conveyed to the first frequency tunable optical filter;
• wherein the second trio relationship includes a parameter value of each of the second control signal and the fourth control signal, and the fourth carrier wave frequency of the second SBS optical signal configured to be emitted by the SBS optical resonator when such parameter value of the second control signal is conveyed to the second frequency tunable laser and when such parameter value of the fourth control signal is conveyed to the second frequency tunable optical filter.