Multi-phase oscillators

An oscillator circuit, comprising:

• a first oscillator having first oscillator terminals and including a first bulk acoustic wave (BAW) resonator;
• a second oscillator having second oscillator terminals and including a second BAW resonator;
• a third oscillator having third oscillator terminals and including a third BAW resonator;
• a first circuit having first inputs and first outputs, the first inputs coupled to the first oscillator terminals, the first outputs coupled to the second oscillator terminals, the first circuit including a first transformer coupled between the first inputs and the first outputs;
• a second circuit having second inputs and second outputs, the second inputs coupled to the second oscillator terminals, the second outputs coupled to the third oscillator terminals, the second circuit including a second transformer coupled between the second inputs and the second outputs;
• and
• a third circuit having third inputs and third outputs, the third inputs coupled to the third oscillator terminals, the third outputs coupled to the first oscillator terminals, and the third circuit including a third transformer coupled between the third inputs and the third outputs.

An oscillator circuit, comprising:

• a first oscillator having first oscillator terminals, the first oscillator including a first bulk acoustic wave (BAW) resonator;
• a second oscillator having second oscillator terminals, the second oscillator including a second BAW resonator, the second oscillator terminals coupled to the first oscillator terminals;
• and
• a frequency multiplier circuitry coupled to the first and second oscillators, the frequency multiplier circuitry including a harmonic extraction circuit.

An oscillator circuit, comprising:

• a first bulk acoustic wave (BAW) oscillator circuit having first oscillator terminals;
• a second BAW oscillator circuit having second oscillator terminals;
• a first circuit having first inputs and first outputs;
• a second circuit having second inputs and second outputs, in which:
• a first one of the first oscillator terminals is coupled to a first one of the first inputs and to a second one of the second outputs;
• a second one of the first oscillator terminals is coupled to a second one of the first inputs and to a first one of the second outputs;
• a first one of the first outputs is coupled to a first one of the second oscillator terminals and to a second one of the second inputs;
• and
• a second one of the first outputs is coupled to a second one of the second oscillator terminals and to a first one of the second inputs,
• wherein:
• the first one of the first oscillator terminals is a positive one of the first oscillator terminals;
• the second one of the first oscillator terminals is a negative one of the first oscillator terminals;
• the first one of the second oscillator terminals is a positive one of the second oscillator terminals;
• the second one of the second oscillator terminals is a negative one of the second oscillator terminals;
• the first one of the first inputs is a positive one of the first inputs;
• the second one of the first inputs is a negative one of the first inputs;
• the first one of the first outputs is a positive one of the first outputs;
• the second one of the first outputs is a negative one of the first outputs;
• the first one of the second inputs is a positive one of the second inputs;
• the second one of the second inputs is a negative one of the second inputs;
• the first one of the second outputs is a positive one of the second outputs;
• and
• the second one of the second outputs is a negative one of the second outputs.

A system comprising:

• an oscillator circuit, comprising:
• multiple bulk acoustic wave (BAW) oscillator circuits each having respective oscillator terminals and a respective center tap terminal, each of the multiple BAW oscillator circuits configured to provide respective signals having a first frequency at the respective oscillator terminals;
• and
• a first circuit having an input and an output, the input coupled to the center tap terminals of the BAW oscillator circuits, and the first circuit configured to provide a clock signal at the output, the clock signal having a second frequency higher than the first frequency;
• a second circuit having a clock input coupled to the output of the first circuit.