The Design of Elliptic Low-Pass Filter in Wide Band Chirp Source Based on DDS
Xiaomei Zhang · Journal of Qingdao University · 2006
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.