Quadrature oscillator circuitry and circuitry comprising the same

Quadrature oscillator circuitry, comprising:

• first and second differential oscillator circuits, each differential oscillator circuit comprising first and second tail nodes, a pair of output nodes, and a pair of parallel current paths which extend in parallel between its first and second tail nodes via its output nodes, respectively, and each differential oscillator circuit configured to generate a pair of differential oscillator signals at its respective output nodes;
• and
• a cross-coupling circuit comprising first and second transistors connected to cross-couple the differential oscillator circuits,
• wherein:
• for each of the differential oscillator circuits, a first tail current path connects the first tail node to a first voltage-source node and a second tail current path connects the second tail node to a second voltage-source node, one of the first and second voltage-source nodes for connection to a high-voltage source and the other of the first and second voltage-source nodes for connection to a low-voltage source;
• the first and second transistors are connected to form respective parts of the first tail current paths of the differential oscillator circuits, respectively, so that current flowing along the respective first tail current paths flows through the respective transistors;
• the gate or base terminals of the first and second transistors are connected to the first tail nodes of the second and first differential oscillator circuits, respectively, so that they are controlled by voltage signals produced at the first tail nodes of the second and first differential oscillator circuits, respectively;
• the first tail current paths extend from the first tail nodes via the first and second transistors, respectively, to a shared tail node;
• a shared tail current path connects the shared tail node to a shared voltage-source node, being the first voltage-source node of both of the differential oscillator circuits;
• each of said differential oscillator circuits comprises an LC tank circuit configured to have a target resonant frequency;
• and
• the quadrature oscillator circuitry comprises an auxiliary LC tank circuit shared by the differential oscillator circuits and configured to have a resonant frequency which is substantially twice the target resonant frequency.