Apparatus for providing a carrier signal with two digital data streams I-Q modulated thereon
First Claim
1. A digital I-Q modulator for providing an analog signal at a desired carrier signal frequency ω
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1 and having in-phase I and quadrature-phase Q modulation sidebands thereof respectively provided responsive to respective different ones of in-phase I and quadrature-phase Q baseband digital data stream signals, comprising;
means for alternatingly selecting a different one of the pair of data stream signals to provide a first data signal during each of a successive multiplicity of time intervals of duration T essentially equal to the reciprocal of the carrier signal frequency ω
1 ;
means for inverting each bit of the first data signal during every other one of a multiplicity of successive inversion time intervals of duration T/2, each commencing at successive ones of the beginning and midpoint of each time interval T, to provide a second data signal;
a single digital-to-analog converter (DAC) means for converting said second data signal to an analog signal portion having an amplitude substantially established by the digital value of the second data signal during each of another multiplicity of successive conversion time intervals of duration T/4, each commencing at successive ones of the beginning and midpoint of each inversion time interval T/2; and
a bandpass filter having a center frequency substantially equal to the carrier signal frequency ω
1 and a passband of at least twice the bandwidth of the baseband digital data stream signals.
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Accused Products
Abstract
A digital I-Q modulator provides an analog signal at a desired frequency ω1 with in-phase I and quadrature-phase Q modulation sidebands provided responsive to different associated ones of in-phase I and quadrature-phase Q digital data streams, each having the same number N of data bits. A multiplexer alternatingly selects a different one of the data streams to provide a first N-bit-wide data signal during each of a successive multiplicity of time intervals of duration T essentially equal to the reciprocal of the carrier signal frequency ω1. The bits of the data signal are inverted to provide another data signal during every other one of a multiplicity of inversion time intervals of duration T/2, with each commencing at one of the beginning and midpoint of each time interval T. A single digital-to-analog converter (DAC) uses the sequentially inverted data stream to provide an analog signal having an amplitude substantially established by the digital value of the second data signal during each of another multiplicity of conversion time intervals of duration T/4, each commencing at one of the beginning and midpoint of each inversion time interval T/2. A bandpass filter, having a center frequency substantially equal to the carrier signal frequency F and a bandpass of at least twice the baseband signal bandwidth of the digital data streams effectively removes all frequency components except those of the desired modulation envelopes at the desired carrier frequency.
69 Citations
16 Claims
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1. A digital I-Q modulator for providing an analog signal at a desired carrier signal frequency ω
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1 and having in-phase I and quadrature-phase Q modulation sidebands thereof respectively provided responsive to respective different ones of in-phase I and quadrature-phase Q baseband digital data stream signals, comprising;
means for alternatingly selecting a different one of the pair of data stream signals to provide a first data signal during each of a successive multiplicity of time intervals of duration T essentially equal to the reciprocal of the carrier signal frequency ω
1 ;means for inverting each bit of the first data signal during every other one of a multiplicity of successive inversion time intervals of duration T/2, each commencing at successive ones of the beginning and midpoint of each time interval T, to provide a second data signal; a single digital-to-analog converter (DAC) means for converting said second data signal to an analog signal portion having an amplitude substantially established by the digital value of the second data signal during each of another multiplicity of successive conversion time intervals of duration T/4, each commencing at successive ones of the beginning and midpoint of each inversion time interval T/2; and a bandpass filter having a center frequency substantially equal to the carrier signal frequency ω
1 and a passband of at least twice the bandwidth of the baseband digital data stream signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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1 and having in-phase I and quadrature-phase Q modulation sidebands thereof respectively provided responsive to respective different ones of in-phase I and quadrature-phase Q baseband digital data stream signals, comprising;
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15. A method for providing an analog signal at a desired carrier signal frequency ω
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1, having in-phase I and quadrature-phase Q modulation sidebands thereof respectively provided responsive to respective different ones of in-phase I and quadrature-phase Q baseband digital data stream signals, comprising the steps of;
sampling the I data stream signal at the beginning of each of a multiplicity of successive sampling time intervals of duration T, essentially equal to the reciprocal of the carrier signal frequency ω
1, to provide a first sample signal;sampling the Q data stream signal at a time delayed by one-quarter of the time interval T after the beginning of each of the multiplicity of successive time intervals at which the I data stream signal is sampled, to provide a second sample signal; combining the first and second sample signals, in the time domain, to provide a combined signal; and filtering the combined signal to include spectral energy substantially limited to a frequency band having a center frequency substantially equal to the carrier signal frequency ω
1 and a passband of at least twice the bandwidth of the baseband digital data stream signals. - View Dependent Claims (16)
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1, having in-phase I and quadrature-phase Q modulation sidebands thereof respectively provided responsive to respective different ones of in-phase I and quadrature-phase Q baseband digital data stream signals, comprising the steps of;
Specification