Research On High-order Integrated Filter Circuit Design Methods Based On Component-level SFG Simulations

The active filter design technique for fully integrated circuit realization is generalized and a canonical signal flow graph(SFG) design method is proposed based on component-level simulations of general LC ladder networks, in which a one-to-one correspondence between reactive elements and integrators is maintained. With this new design method, signal flow graphs of elliptical bandpass filter,all pole highpass filter,elliptical highpass filter,all pole bandstop filter and elliptical bandstop filter are derived from the resistive doubly terminated passive filters, and the corresponding full-differential active RC filter are also implemented. By means of circuit simulation program SPICE and sensitivity analysis, some research results have been acquired.The innovative points of this thesis include:1. A canonical component-level SFG design method based on simulations of general LC ladder networks is proposed, which contains three kinds of simulation modes for choosing crunode of SFGs: node voltage SFG simulation mode, mesh current SFG simulation mode and hybrid SFG simulation mode. For a LCR ladder filter, each kind of simulation modes could lead to different SFG topology.2. Rules of choosing simulation modes are proposed when the component-level SFG design method is used. Canonical structures of filters could be obtained by using proper simulation modes for given LCR ladder networks, in which problems due to tie-sets of capacitors or cut-sets of inductors could be solved. Complying with these rules, a new design method for fully integrated bandpass filter is presented, which could also be used on complicated high order integrated bandpass filters with transmission zeros.3. Three dominant factors affecting amplitude-frequency characteristics of active realizations are presented by the results of sensitivity analysis: the canonicity of the SFGs, the leap frog symmetry of circuit topology and the tolerance of RC elements. To weaken the influence of the tolerance of RC elements, Norton transformation is used to obtain a new LCR ladder networks together with its active realization. Spice simulator verified the improvements of the magnitude response.4. The uppermost shortcoming of this method from other methods is also proposed: amplitude-frequency response of the filter designed by this method is sensitive to nonideal characteristics of fully-differential operational amplifier. It brings A technique is proposed to weaken the influence of parasitical poles and zeros on amplitude frequency characteristic: using SFG operation rules, the frequency of parasitical poles and zeros could be changed slightly by the fine adjustment of SFGs.5. New design methods for fully integrated highpass filter,bandpass filter and bandstop filter with transmission zeros is presented, which provide new design means to filters in system on chip.