Quadrature alignment in communications receivers

Abstract

The present invention, generally speaking, takes advantage of the properties of quadrature signals to achieve precise quadrature alignment in a simple fashion. In particular, the expectation of the product of quadrature signals is zero. In accordance with the teachings of the invention, a phase error detection network therefore operates by multiplying the received quadrature signals and low-pass filtering the product to produce an error signal. When the signals are in precise quadrature relationship, the error signal will be zero. Real-time feedback control may be used to drive the error to zero. In accordance with another aspect of the invention, a variable phase shift network is achieved using a dual delay line. The difference in delay between the two delay lines is adjusted in response to the error signal to obtain precise quadrature alignment. The principles of the invention may be applied in connection with traditional mixer architectures or with switch-mode (e.g., “aliased undersampling”) architectures.

1 - 14 . (canceled)  
     
     
         15 . A method of driving a power switching transistor having a threshold voltage, comprising: coupling a driver transistor to the switching transistor and to two different rail voltages, one greater than the threshold voltage and one less than the threshold voltage; and using a sinusoidal signal, causing the driver transistor to alternate between two states including one state in which the driver transistor causes one rail voltage to be applied to the switching transistor to turn the switching transistor on, and another state in which the driver transistor causes another rail voltage to be applied to the switching transistor to turn the switching transistor off.