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在研究数字脉冲调制时,对调制方式的功率谱分析十分必要。详细推导了随机双幅度脉冲位置调制(DAPPM)序列的功率谱密度,并分别对连续谱和离散谱进行了分析。数值结果表明,DAPPM的功率谱形状类似于一般的抽样函数,并且包含直流分量,幅度因子α只影响功率谱的幅度,不影响功率谱的形状;时隙基频分量存在与否与脉冲占空比有关;时隙基频幅度强弱依赖于调制阶数和脉冲占空比。当占空比为0.5时,时隙基频分量最大,调制阶数每增大1,幅度衰减约5 dB。同时指出,当调制阶数较大时,随机DAPPM序列难以直接提取时隙基频分量。
In the study of digital pulse modulation, the modulation of the power spectrum analysis is necessary. The power spectral density of random double amplitude pulse position modulation (DAPPM) sequence is deduced in detail, and the continuous spectrum and discrete spectrum are respectively analyzed. The numerical results show that the shape of power spectrum of DAPPM is similar to the general sampling function and contains the direct current component. The amplitude factor α only affects the amplitude of the power spectrum and does not affect the shape of the power spectrum. The presence or absence of the fundamental frequency component of the slot and the pulse duty Than the relevant; slot base frequency amplitude depends on the modulation order and pulse duty cycle. When the duty cycle is 0.5, the fundamental frequency component of the time slot is the largest. When the modulation order is increased by 1, the amplitude attenuation is about 5 dB. At the same time, it is pointed out that when the modulation order is large, it is difficult to extract the fundamental frequency component of the slot directly by the random DAPPM sequence.