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US 7,924,946 B2Granted
Method for recovering a baseband signal from an RF signal
AssigneeFitipower Integrated Technology, Inc.
InventorYum-Cheng Chang
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Abstract
By shifting an RF signal to IQ components of a modulated baseband signal directly, the zero-IF technology and IQ interface are applied in ATSC, NTSC, and PAL systems, and VSB and SSB modulations. The mathematic calculations are based on Fourier transform for shifting the RF signal and for recovering a baseband signal from the modulated baseband signal.
Claims10
A method for recovering a baseband signal from an RF signal comprising:
- receiving the RF signal comprising a modulated baseband signal, a carrier frequency, an adjacent channel signal, and noise;
- amplifying the RF signal;
- mixing the RF signal with a first sinusoidal wave with the carrier frequency to generate a first low frequency component;
- mixing the RF signal with a second sinusoidal wave orthogonal to the first sinusoidal wave to generate a second low frequency component;
- filtering the first low frequency component to filter out Adjacent Channel Signal and noise outside a bandwidth so as to generate a first modulated baseband component of the modulated baseband signal;
- filtering the second low frequency component to filter out Adjacent Channel Signal and noise outside the bandwidth so as to generate a second modulated baseband component of the modulated baseband signal;
- forming a Complex Number signal comprising applying the first modulated baseband component as a Real Part signal and the second modulated baseband component as an Imaginary Part signal;
- and
- generating a Real Number signal of a Shifted Complex Number signal from the Complex Number signal, the Shifted Complex Number signal derived from multiplying the sum of the Real Part signal and the Imaginary Part signal of the Complex Number signal with (ejωht), wherein ωh is half the bandwidth of the modulated baseband signal, and t is time.
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Dependencies are inferred from the claim text.