Digital communications transmitter with synthesizer-controlled modulation and method therefor
First Claim
1. A digital communications transmitter comprising:
- a digital-processing circuit configured to generate a digitally-modulated symbol for each unit interval;
a frequency-profiling circuit configured to generate a plurality of digitally-specified frequencies per unit interval in response to each digitally-modulated symbol, said digitally-specified frequencies being configured to confine radio-frequency (RF) emissions within a predetermined spectral mask;
a digital synthesizer having a frequency input coupled to said frequency-profiling circuit and having a periodic output; and
a digital-to-analog converter having an input responsive to said periodic output of said digital synthesizer.
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Accused Products
Abstract
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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Citations
27 Claims
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1. A digital communications transmitter comprising:
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a digital-processing circuit configured to generate a digitally-modulated symbol for each unit interval;
a frequency-profiling circuit configured to generate a plurality of digitally-specified frequencies per unit interval in response to each digitally-modulated symbol, said digitally-specified frequencies being configured to confine radio-frequency (RF) emissions within a predetermined spectral mask;
a digital synthesizer having a frequency input coupled to said frequency-profiling circuit and having a periodic output; and
a digital-to-analog converter having an input responsive to said periodic output of said digital synthesizer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method of operating a digital communications transmitter comprising:
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encoding input data so as to produce in-phase and quadrature baseband samples for a unit interval;
mapping said in-phase and quadrature baseband samples into a frequency-profile index;
selecting a frequency profile in response to said frequency-profile index, wherein said frequency profile specifies a plurality of frequencies in a predetermined sequence;
synthesizing a digital representation of a periodic signal throughout said unit interval in response to said frequency profile; and
converting said digital representation of said periodic signal into an analog signal. - View Dependent Claims (19, 20, 21, 22, 23, 24)
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25. A digital communications transmitter comprising:
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a digital signal processor configured to encode input data so as to produce in-phase and quadrature baseband samples for each unit interval, to map said in-phase and quadrature baseband samples into a frequency-profile index for each unit interval, and to output said frequency-profile index for each unit interval;
a frequency-profiling circuit configured to generate a plurality of digitally-specified frequencies per unit interval in response to each frequency-profile index, said digitally-specified frequencies being configured to confine radio-frequency (RF) emissions within a predetermined spectral mask;
a digital synthesizer having a frequency input coupled to said frequency-profiling circuit and having a periodic output; and
a digital-to-analog converter having an input responsive to said periodic output of said digital synthesizer. - View Dependent Claims (26, 27)
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Specification