Aliasing-Free Digital Pulse-Width Modulation for Burst-Mode RF Transmitters

作者：Hausmair Katharina^*; Chi Shuli; Singerl Peter; Vogel Christian

来源：IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS, 2013, 60(2): 415-427.

DOI：10.1109/TCSI.2012.2215776

• Aliasing distortion
• burst-mode operation
• Fourier series expansion
• pulse-width modulation (PWM)
• radio frequency (RF) transmitters

Burst-mode operation of power amplifiers (PAs) is a promising concept towards higher power efficiency in radio frequency (RF) transmitters. Such transmitters use pulse-width modulation (PWM) to create the driving signal for the PA, and a reconstruction filter after amplification to obtain the transmission signal. However, conventional digital pulse-width modulated signals contain a large amount of distortion that cannot be removed by the reconstruction filter in a satisfactory manner. %26lt;br%26gt;This paper introduces a method for digital PWM that is free of destructive aliasing distortion. First, a set of mathematical closed-form equations fully describing all baseband processing steps required in conventional PWM-based RF transmitters is developed. Analysis of the equations leads to the conclusion that destructive distortion in digital PWM systems originates from aliasing induced by the infinite bandwidth of pulsed signals that is entailed by the nonlinear operation of the pulse-width modulator. Based on this knowledge, a PWM method is developed that ensures that the generated signals are bandlimited and hence completely avoids destructive aliasing distortion. Simulations as well as measurements demonstrate the improvement that can be achieved with the proposed method compared to conventional methods. The results indicate that by using the proposed method it becomes feasible to implement filters that allow for obtaining satisfying transmission signal quality.

• 出版日期2013-2