【摘要】 对宽带线性调频源中基带信号产生时所用的低通滤波器进行了设计。在设计过程中,考虑DDS的结构特点及其杂散信号的分布,采用了截止特性陡峭的9阶椭圆函数低通滤波器。该滤波器的3dB截止频率为125MHz,在146MHz处的衰减为70dB,并且通带内纹波小于0.2dB。通过Pspice仿真研究表明在采用了幅度均衡技术后,滤波器的幅频特性良好;实际制作电路时,应按照“选定电感,微调电容”的原则,适当调整元件值。更多还原

【Abstract】 This article has designed an elliptic low pass filter for the generation of base band signals in a wideband chirp source. In the process of design, the structure feature of DDS and the distribution of spurious signal are considered. A 9th-order elliptic low-pass filter with cliffy cut-off character is adopted. Its 3 dB cut-off frequency is 125 MHz; Its attenuation is 70 dB in 146 MHz; and its pass band ripple is less than 0.2 dB. The study of Pspice simulation shows that amplitude-frequency characteristic of the filter is good when amplitude equalizer is used. It also can be concluded that according to the principle of “fixed inductance and changed capacitance”, the component values are adjusted appropriately.更多还原