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ln-phase/quadrature-phase (l/Q) errors in the implementation of a digital predistortion (DPD) system based on a direct-conversion structure have proven to be a limiting performance factor in modern communication systems. This work presents a method o f time domain compensation fTDQ for frequency-dependent channel imbalances in wideband DPD systems. Compared with the widely used frequency domain compensation method, this method has lower computational complexity. Experimental results show that this method improves transceiver loop normalized mean squared error (NMSE) for 20 and 60 MHz Long Term Evolution (LTE) signals by 10.9and 11.3 dB, respectively. Adjacent channel power ratio (ACPR) is improved by more than 6 and 8 dB, respectively. [ABSTRACT FROM AUTHOR]

The article shows that the complexity of the calculations for determining the total composite phase noise can be reduced while maintaining a reasonable accuracy. Determining the total composite phase noise is a complex calculation requiring knowledge of the phase noise of the reference and microwave oscillators, the reference multiplication efficiency factor and the phase-locked loop frequency response as a function of the noise injected at the reference and the noise injected by the microwave oscillator. Following two parameters may help reduce the complexity: one, the frequency and phase noise of the reference oscillator, and two, the frequency and phase noise of the microwave oscillator.