US 6,983,028 B2 | ||
Carrier restoration apparatus and method | ||
Keun Hee Ahn, Inchon-shi (Korea, Republic of) | ||
Assigned to LG Electronics Inc., Seoul (Korea, Republic of) | ||
Filed on Aug. 23, 2001, as Appl. No. 9/934,693. | ||
Claims priority of application No. 2000-48926 (KR), filed on Aug. 23, 2000. | ||
Prior Publication US 2002/0067778 A1, Jun. 06, 2002 | ||
Int. Cl. H04L 27/38 (2006.01); H04B 1/10 (2006.01) |
U.S. Cl. 375—326 | 16 Claims |
1. A carrier restoration apparatus for converting a pass-band digital signal of a specified channel into a base-band digital
signal where a frequency offset and a phase jitter are compensated by demodulating the pass-band digital signal by a sine/cosine
wave, the apparatus comprising:
a phase/frequency detection section for obtaining a phase error between constellations of a demodulated signal and constellations
of a blind decision signal or a decision-directed decision signal, and extracting a polarity of the phase error;
a loop section for frequency acquisition for extracting the corresponding frequency offset by accumulating pre-calculated
bandwidth values according to the polarity of the phase error, generating the digital type sine and cosine waves according
to the extracted frequency offset, and then generating the base-band digital signal where the frequency offset of a carrier
is acquired by demodulating the pass-band digital signal by the sine and cosine waves;
a loop section for phase tracking for extracting the corresponding phase jitter by accumulating the pre-calculated bandwidth
values according to the polarity of the phase error, generating the digital type sine and cosine waves according to the extracted
phase jitter, and then generating demodulated signal constellations where the phase jitter is tracked by demodulating the
base-band digital signal by the sine and cosine waves;
a blind decision section for extracting the polarity of the demodulated signal constellations generated from the loop section
for phase tracking, and generating blind decision signal constellations by slicing the demodulated signal constellations according
to the extracted polarity; and
a decision-directed decision section for generating a decision-directed decision signal constellations matching respective
signal levels of the demodulated signal constellations generated from the loop section for phase tracking,
wherein the loop section for frequency acquisition comprises:
a frequency acquisition loon filter for detecting the corresponding frequency offset Δω by accumulating values of predetermined
positive or negative bandwidths for frequency acquisition according to the polarity of the phase error extracted by the phase/frequency
detection section;
a controlled oscillator for generating the digital type sine wave sin(ωc+Δω) and cosine wave cos(ωc+Δω) according to the corresponding frequency offset detected by the frequency acquisition loop filter; and
a frequency acquisition element for generating the base-band digital signal where the frequency offset is acquired by demodulating
the pass-band digital signal PB Data by the cosine wave cos(ωc+Δω) and the sine wave sin(ωc+Δω) generated from the controlled oscillator.
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