N-path baseband down-conversion with bias current steering and sinusoidal voltage drivers for transistor commutation

A receiver circuit for baseband down-conversion of a radio frequency (RF) input signal from an antenna, the input signal having a center frequency, the receiver circuit comprising:

• an RF input terminal configured to receive the RF input signal;
• a direct current (DC) voltage supply rail configured to provide a DC voltage supply;
• a shared current source configured to draw a shared bias current from the DC voltage supply;
• a ground terminal coupled to one end of the shared current source;
• N baseband down-conversion paths, wherein an nth baseband down-conversion path comprises an nth transistor, an nth load impedance, and an nth filter capacitor to generate an nth baseband down-conversion signal, where the subscript n is an integer 1 to N and N is an integer of 2 or more and corresponds to a number of baseband down-conversion paths in N baseband down-conversion paths;
• and
• a sinusoidal local oscillator configured to generate an nth sinusoidal voltage signal having a signal frequency that is substantially the same as the center frequency, the nth sinusoidal voltage signal having an nth phase angle and a time varying amplitude;
• wherein:
• the nth load impedance has one end coupled to the DC voltage supply rail;
• the nth transistor has a source coupled to the RF input terminal and to another end of the shared current source, a drain coupled to another end of the nth impendence load and to one end of the nth filter capacitor, and a gate coupled to the sinusoidal local oscillator to receive the nth sinusoidal voltage signal;
• the drain of the nth transistor is configured to provide an nth mixed signal associated with the nth phase angle in response to the time-varying amplitude of the nth sinusoidal voltage signal, the shared bias current, and the RF input signal;
• and
• the nth filter capacitor is configured to provide the nth baseband down-conversion signal in response to the nth mixed signal.

A method of converting a radio frequency (RF) input signal having a center frequency to a baseband signal, the method comprising:

• receiving the RF input signal;
• generating a plurality of sinusoidal voltage signals having a signal frequency that is substantially the same as the center frequency;
• provide a shared bias current;
• associating a plurality of transistors with the plurality of sinusoidal voltage signals, the RF input signal, and the shared bias current;
• cyclically steering the shared bias current to configure one of the plurality of transistors to operate in a saturation mode in response to a time varying amplitude of one of the plurality of sinusoidal voltage signals that drives a gate of the one of the plurality of transistors;
• mixing the RF input signal and the one of the plurality of sinusoidal voltage signals associated with the one of the plurality of transistors configured in the saturation mode to generate a mixed signal, wherein the mixed signal has a phase angle that is at least partially determined by the one of the plurality of sinusoidal voltage signals that drives the gate of the one of the plurality of transistors;
• and
• filtering the mixed signal to provide the baseband signal having the phase angle of the mixed signal.