| 摘要 |
In order to generate a carrier frequency Fc, a digital modulator must operate (to satisfy the Nyquist criteria) at a system sample rate Rs which is at least twice the carrier frequency Fc. However, digital modulator structures are provided herein that facilitate the use of M quadrature modulators which modulate, at a reduced modulation rate Rs/M, respective ones of M polyphase cosine elements and M polyphase sine elements with respective ones of interpolated I elements and interpolated Q elements to thereby form M polyphase modulated elements. The modulated elements are then sequentially selected in a multiplexer to form a modulated digital signal. The reduced modulation rate simplifies modulator design and lowers fabrication costs.
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