Low-1/f-Noise Local Oscillator for Non-Overlapping Differential I/Q Signals

摘要

The present invention relates to a circuit arrangement (300) for generating non-overlapping and immune-to-1/f-noise signals as has been described. A break-before-make (BBM) circuit ensures that the differential I/Q signals (LO_—0, LO_—90, LO_—180, LO_—270), driving the transistors (M11, M12, M21, M22) of mixers (16A, 16B) in an RF receiver (200), are non-over-lapping for having at any time only one of these transistors turned on. The duty cycle of each driving signal is measured, and the difference (Δ) in the duty cycle corresponding to two subsequent LO phases is determined through a respective differential amplifier (38A-38D). Each differential amplifier is configured to have a current output (LT_—0, LT_—90, LT_—180, LT_—270), which is then fed back to the input of the input buffer (30A-30D) corresponding to the first LO phase in order to adjust its logic threshold (LT) level and make the difference (Δ) equal to zero. Thereby, the combined action of the BBM circuit and the feedback loops results in four non-overlapping differential I/Q signals (LO_—0, LO_—90, LO_—180, LO_—270) with constant and mutually equal duty cycles, and fixed and well-defined relative positions.