对于超宽带模拟信号,很难用单个模拟数字转换器(ADC)直接进行采样。该文提出了一种新的并行调制混合滤波器组结构用于实现超宽带模拟信号的采样,首先,将每一路宽带模拟输入信号进行余弦调制,并用相同的低通模拟滤波器均匀分割输入信号的带宽;然后,采用相同的ADC将子带信号数字化;各路子带信号通过上采样器后用数字综合滤波器综合得到原宽带模拟输入信号的数字重构。综合滤波器采用总体最小二乘准则下的特征值滤波器设计方法得到。本文所提出的系统结构不需要使用高速的采样保持电路,降低了系统实现的难度,并且设计的系统具有与其他混合滤波器组相近的重构性能。仿真结果表明了本方法的有效性。
It is difficult to use a single analog-to-digital conversion (ADC) to satisfy the requirements for conversion of an ultra-wideband signal. A parallel architecture for wideband ADC, named cosine modulated hybrid filter bank, is presented to address this problem. First, the proposed architecture shifts the input signal spectrum by means of mixers. The mod- ulated signal is channelized into smaller frequency subband signals using identical lowpass analog filters. Then the subband signals are digitized through identical narrowband ADCs, respectively. Finally, the digitized signals are up-sampled, filtered and combined to reconstruct the digital representation of original wide-band input signal. The digital filters are designed to the eigenfilter method based on total least squares error criterion. Since the sample-and-hold circuits needed in this architecture are simple identical narrowband baseband circuits, which makes the design easier and cheaper. Several design examples are presented to illustrate the performance of the proposed system.