| 摘要 |
PROBLEM TO BE SOLVED: To easily and accurately exert predistortion and to further increase average transmission power. SOLUTION: A signal correction apparatus comprises an absolute-value calculating unit 30 for calculating the magnitude x of a vector (xi, xq) consisting of an in-phase component xi and an orthogonal component xq filtered by a low-pass filter, predistortion units 31, 32 for multiplying both xi and xq by h(x)/x, and a phase pre-rotating unit 22 for rotating output vectors of the predistortion units by an angleϕ(x). When the output amplitude is expressed as a function g(x) of the input amplitude x of a power amplifier, the function h(x)/x is determined so that the function g(h(x)) is proportional to x. Alternatively, the predistortion function h(x) is approximated by a power-series expansion of the amplitude x, initial values are applied to the power-series expansion coefficients c1 to cn; and the coefficients c1 to cn are so determined as to substantially minimize the absolute valueεof the ratio of the secondary Fourier coefficients of the function g(h(x)) to the primary Fourier coefficients, wherein the amplitude x is defined as the amplitude of the intermodulated wave of base-band signals having angular frequenciesω1 andω2. COPYRIGHT: (C)2007,JPO&INPIT
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