Element removal design in microwave filters

Abstract

A method of designing a microwave filter using a computerized filter optimizer, comprises generating a filter circuit design in process (DIP) comprising a plurality of circuit elements having a plurality of resonant elements and one or more non-resonant elements, optimizing the DIP by inputting the DIP into the computerized filter optimizer, determining that one of the plurality of circuit elements in the DIP is insignificant, removing the one insignificant circuit element from the DIP, deriving a final filter circuit design from the DIP, and manufacturing the microwave filter based on the final filter circuit design.

What is claimed is: 
     
         1 . A microwave filter constructed using a process comprising the steps:
 (a) generating a filter circuit design in process (DIP) comprising a plurality of circuit elements having a plurality of resonant elements and one or more non-resonant elements;   (b) optimizing the DIP by inputting the DIP into the computerized filter optimizer;   (c) determining that one of the plurality of circuit elements in the DIP is insignificant after the DIP has been optimized;   (d) removing the one insignificant circuit element from the DIP;   (e) deriving a final filter circuit design from the DIP; and   (f) manufacturing the microwave filter based on the final filter circuit design.   
     
     
         2 . The microwave filter of  claim 1 , wherein the one insignificant circuit element is a non-resonant element that initially comprises one of an inductance and a capacitance, the process, prior to removal of the non-resonant element, further comprises:
 generating a transformed filter circuit design by transforming the one insignificant circuit element from the one of the inductance and the capacitance to the other of the inductance and the capacitance;   again optimizing the DIP by inputting the transformed filter circuit design into the computerized filter optimizer; and   confirming that the one insignificant circuit element in the DIP is insignificant.   
     
     
         3 . The microwave filter of  claim 1 , wherein the one insignificant circuit element is initially a resonant element, the process, prior to removal of the one insignificant circuit element, further comprises:
 generating a transformed filter circuit design by transforming the one insignificant circuit element from the resonant element to a static capacitance;   again optimizing the DIP by inputting the transformed filter circuit design into the computerized filter optimizer; and   confirming that the one insignificant circuit element in the DIP is insignificant.   
     
     
         4 . The microwave filter of  claim 1 , wherein the removal of the one significant circuit element from the DIP results in a reduced filter circuit design, the process further comprising:
 (g) again optimizing the DIP by inputting the reduced filter circuit design into the computerized filter optimizer;   (h) determining that another one of the plurality of circuit elements in the DIP is insignificant after the DIP is again optimized; and   (i) removing the other one insignificant circuit element from the DIP.   
     
     
         5 . The microwave filter of  claim 4 , wherein the one insignificant circuit element is a non-resonant element, and the other insignificant circuit element is a resonant element. 
     
     
         6 . The microwave filter of  claim 4 , further comprising generating at least one additional reduced filter circuit design by repeating steps (g)-(i) until none of the circuit elements in the DIP is determined to be insignificant, wherein the final filter circuit design is identical to a last optimized DIP. 
     
     
         7 . The microwave filter of  claim 1 , wherein the one circuit element is a non-resonant element. 
     
     
         8 . The microwave filter of  claim 7 , wherein determining if the non-resonant element is insignificant comprises comparing a value of the non-resonant element to a threshold value. 
     
     
         9 . The microwave filter of  claim 8 , wherein the value of the non-resonant element is an absolute impedance value. 
     
     
         10 . The microwave filter of  claim 9 , wherein the non-resonant element is either a series inductor or a shunt capacitor that is determined to be insignificant if the absolute impedance value is less than the threshold value. 
     
     
         11 . The microwave filter of  claim 9 , wherein non-resonant element is either a shunt inductor or a series capacitor that is determined to be insignificant if the absolute impedance value is greater than the threshold value. 
     
     
         12 . The microwave filter of  claim 7 , wherein the value of the non-resonant element is a relative value. 
     
     
         13 . The microwave filter of  claim 12 , wherein the non-resonant element is a series circuit element, the relative value is a percentage of the absolute value of the series circuit element relative to the absolute value of another series circuit element in the DIP, and the series circuit element is determined to be insignificant if the relative value is less than the threshold value. 
     
     
         14 . The microwave filter of  claim 12 , wherein the non-resonant element is a shunt circuit element, the relative value is a percentage of the absolute value of the shunt circuit element relative to the absolute value of another shunt circuit element in the DIP, and the shunt circuit element is determined to be insignificant if the relative value is less than the threshold value. 
     
     
         15 . The microwave filter of  claim 12 , wherein the non-resonant element is a series circuit element, the relative value is a percentage of the absolute value of the series circuit relative to an impedance seen in either direction from the series circuit element, and the series circuit element is determined to be insignificant if the relative value is less than the threshold value. 
     
     
         16 . The microwave filter of  claim 12 , wherein the non-resonant circuit is a shunt circuit element, the relative value is a percentage of the absolute value of the shunt circuit element relative to a susceptance seen in either direction from the shunt circuit element, and the shunt circuit element is determined to be insignificant if the relative value is less than the threshold value. 
     
     
         17 . The microwave filter of  claim 1 , wherein determining if the non-resonant element is insignificant comprises removing the non-resonant element from the optimized circuit design, and comparing a value of a performance parameter in the optimized circuit design without the non-resonant element to a value of the performance parameter in the optimized circuit design with the non-resonant element. 
     
     
         18 . The microwave filter of  claim 1 , wherein the one circuit element is a resonant element. 
     
     
         19 . The microwave filter of  claim 18 , wherein the DIP has a frequency response with one or both of a passband and a stopband, and wherein determining if the resonant element is insignificant comprises comparing transmission zero associated with the resonant element to an edge frequency of the one or both of the passband and the stop band. 
     
     
         20 . The microwave filter of  claim 19 , wherein the resonant element is determined to be insignificant if a percentage of the transmission zero relative to an edge frequency of the one or both of the passband and the stop band is greater than a threshold value. 
     
     
         21 . The microwave filter of  claim 1 , wherein the microwave filter is an acoustic wave filter. 
     
     
         22 . The microwave filter of  claim 21 , wherein the acoustic wave filter is one of a surface acoustic wave (SAW), a bulk acoustic wave (BAW), and a film bulk acoustic resonator (FBAR). 
     
     
         23 . The microwave filter of  claim 1 , wherein the microwave filter is a ladder filter.