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引言各种含有扩频数据通信线路的军用和商用系统,需要高频谱纯度、低噪声、精确、快速跳频的信号源或综合器。跳频速度小于1μs的不能采用锁相环。直接综合是用开关矩阵来选择连续工作的信源,然后混合产生输出频率,其跳频速度几乎和开关本身的速度一样快。因而,直接综合器可以容易地在零点几微秒范围内改变频率。低成本的、结构紧凑的直接综合器,要求带有相同特性的滤波器组(Banks)。声表面波(SAW)滤波器是一种合乎逻辑的选择。具有表面波滤波器组的直接综合器示于图1。图中说明了
INTRODUCTION Various military and commercial systems that include spread spectrum data communications lines require signal generators or synthesizers with high spectral purity, low noise, accurate and fast frequency hopping. Frequency hopping speed of less than 1μs can not be used phase-locked loop. Direct synthesis is to use the switch matrix to select the source of continuous work, and then mixed to produce the output frequency, the frequency hopping almost as fast as the speed of the switch itself. Thus, the direct synthesizer can easily change the frequency within a few microseconds. Low-cost, compact, direct synthesizers require Banks with the same characteristics. Surface acoustic wave (SAW) filter is a logical choice. A direct synthesizer with a surface acoustic wave filter bank is shown in FIG. The figure shows