Patent ID: 8428183

Claim:
A method for monitoring and aligning in-phase (I) and quadrature (Q) data in a quadrature phase shift keying (QPSK) modulator comprising: sending a series of data bits to an I data channel of the QPSK modulator and a copy of the series of data bits to a Q data channel of the QPSK modulator, the series of data bits and the copy of the series of data bits having a relative skew; and measuring average modulator output power as a function of the relative skew and carrier phase Φ between I and Q data channels at least in part by adjusting, with a phase control, the relative carrier phase Φ, adjusting, with at least one adjustable data delay, the relative skew by integer numbers of unit-intervals for the adjusted relative carrier phase Φ, and detecting, with a detector, the average modulator output power for combinations of the adjusted relative phase Φ and of the adjusted relative skew.