| 摘要 |
PURPOSE:To make a modulator/demodulator small and to reduce the cost by utilizing digital signal processing of a high efficiency orthogonal arithmetic operation unit so as to compose/decompose low frequency base band signals thereby eliminating a phase difference between subcarriers at modulation/demodulation. CONSTITUTION:A low frequency local generating means 1 generates a function of exp(j(2i-1)#2wst) when number of subcarriers(SC) is an even number and generates a function of exp(2jiomegaSt) when number of subcarriers(SC) is an odd number. A vector inversion means 2 generates a rotation complex vector exp(-j(2i-1)omegast) when number of subcarriers(SC) is an even number and generates a rotation complex vector exp(-2jiomegast) when number of subcarriers(SC) is an odd number to give a low frequency base band signal via multiplier circuits 3, 4 and adder means 5, 8. A high frequency local generating means 6 generates a rotation complex vector exp(jomegast) and a multiplier means 7 multiplies the vector with an output of the means 8, then the relation equivalent to equation I is obtained. Thus, no phase difference between the subcarriers is produced. Angular frequencies omegac, omegack are selected so as to realize equation II by digital signal processing; exp(jomegact)sd(t)... equation I sd(t)=SIGMA(k=1, mk(t)exp(jomegaskt)... equation II. |
