Digital clipping method for a transmitter of an orthogonal frequency division multiple access system
View Patent ↗The present invention relates to a digital clipping method for reducing a high peak-to-average power ratio (PAPR) of a transmission signal in a transmitter of an orthogonal frequency division multiplexing access (OFDMA) system. In the method, a) the transmission signal to be digitally clipped is divided into real and imaginary parts, b) magnitudes of the real and imaginary part signals are divided into a plurality clipping levels, and c) the transmission signal is respectively clipped by comparing the real and imaginary part signals with the plurality of clipping levels while allowing phase errors. In c), a plurality of comparators is used to respectively compare the real and imaginary parts of the complex number transmission signal with the plurality of clipping levels.
1. A digital clipping method for clipping an Orthogonal Frequency Division Multiplexing (OFDM) transmission signal, the method comprising:
a) dividing the transmission signal into real and imaginary parts;
b) dividing magnitudes of the real and imaginary part signals into a plurality of clipping sections that have different clipping levels; and
c) clipping the real and imaginary parts of the transmission signal by comparing each of the real and imaginary parts with each of the plurality of clipping levels of the clipping sections while allowing a phase error,
wherein two comparators are used to compare the real and imaginary parts with three clipping levels A, L1, and L2 when the three clipping levels are provided as the plurality of clipping levels, and
wherein the clipped real part y i (n) of the signal y(n) in c) is given as
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wherein the transmission signal x(n) is expressed by a real part x i (n) and an imaginary part jx q (n), as x(n)=x i (n)+jx q (n).
2. The digital clipping method of claim 1 , wherein, in c), a plurality of comparators are used to compare the real and imaginary parts of the complex number transmission signal with the plurality of clipping levels.
3. The digital clipping method of claim 2 , wherein the clipping sections in b) are divided by the first, second, and third clipping levels A, L1, and L2, respectively, wherein L1 is given as L1=Ax(1/√2) and L2 is given as L2=Ax(√2−1).
4. The digital clipping method of claim 3 , wherein the clipped real part of the transmission signal in c) has at least one of 6 values according to the respective clipping sections defined by the first, second, and third clipping levels A, L1, and L2, respectively, wherein the clipped signal y(n) is expressed by a real part y i (n) and an imaginary part jy q (n), as y(n)=y i (n)+jy q (n).
5. The digital clipping method of claim 1 , wherein the clipping sections have a respective clipping level,
wherein the step (c) compares the real and imaginary parts with each clipping level of the clipping sections.