Transformer based filter for complementary oscillator circuitry

Oscillator circuitry configured to output oscillating signals, comprising:

• a first pair of cross-coupled transistors;
• a second pair of cross-coupled transistors;
• a load inductor coupled to the first and second pairs of cross-coupled transistors;
• a load capacitor coupled to the first and second pairs of cross-coupled transistors;
• and
• a transformer based tail filter coupled between the first and second pairs of cross- coupled transistors and including
• a first tail coil coupled to the first pair of cross-coupled transistors,
• a first filter coil inductively coupled to the first tail coil, and
• a differential tunable capacitor directly coupled to the first filter coil.

Oscillator circuitry comprising:

• a first n-type transistor having a source terminal coupled to a first tail node and having a drain terminal coupled to a first output terminal;
• a second n-type transistor having a source terminal coupled to the first tail node and having a drain terminal coupled to a second output terminal;
• a first p-type transistor having a source terminal coupled to a second tail node and having a drain terminal coupled to the first output terminal;
• a second p-type transistor having a source terminal coupled to the second tail node and having a drain terminal coupled to the second output terminal;
• a first tail coil having a first terminal coupled to the first tail node and having a second terminal coupled to a first power supply line;
• a second tail coil having a first terminal coupled to the second tail node and having a second terminal coupled to a second power supply line different than the first power supply line;
• and
• a first filter coil inductively coupled to the first tail coil.