| 摘要 |
A low-power digital communications transmitter ( 20 ) includes a programmable digital-processing circuit ( 22 ), which may be provided by a digital signal processor (DSP), a programmable direct digital synthesizer (DDS), and a constant-envelope, high power amplifier ( 32 ). The DDS ( 24 ) is programmed to provide pulse-shaping and IF/RF signal modulation functions. The digital-processing circuit ( 22 ) produces only one sample per unit interval ( 134 ) and is programmed so that the one sample per unit interval ( 134 ) is a frequency-profile index symbol ( 52 '') produced from a I,Q baseband symbol ( 52 '). The DDS ( 24 ) converts each frequency-profile index symbol ( 52 '') into a frequency profile ( 130 ) that controls the frequency of a synthesizer ( 56 ) to induce modulation into a periodic output ( 68 ) of the synthesizer. Moreover, the frequency profile ( 130 ) is configured to confine spectral emissions within a spectral mask ( 140 ).
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