Coupled Resonator On-Die Filters for WiFi Applications

Abstract

A radio frequency (RF) filter circuit for rejecting one or more spurious components of an input signal has a first resonator circuit including a first capacitor and a first coupled inductor pair of a first inductor and a second inductor, and a second resonator circuit with a second capacitor and a second coupled inductor pair of a third inductor and a fourth inductor. First and second resonator coupling capacitors are connected to the first resonator circuit and the second resonator circuit. A first port and a second port are connected to the first resonator circuit and the second resonator, with the filtered signal of the input signal passed through both the first resonator circuit and the second resonator circuit being output.

What is claimed is: 
     
         1 . A radio frequency (RF) filter circuit for rejecting one or more spurious components of an input signal, the filter circuit comprising:
 a first resonator circuit including a first capacitor and a first coupled inductor pair of a first inductor and a second inductor;   a second resonator circuit including a second capacitor and a second coupled inductor pair of a third inductor and a fourth inductor;   first and second resonator coupling capacitors each connected to the first resonator circuit and the second resonator circuit;   a first port connected to at least one of the first resonator circuit and the second resonator circuit; and   a second port connected to at least one of the first resonator circuit and the second resonator circuit;   wherein the input signal is connected to one of the first port and the second port, and a filtered signal of the input signal passed through both the first resonator circuit and the second resonator circuit being output from a other one of the first port and the second port.   
     
     
         2 . The RF filter circuit of  claim 1 , wherein the first port is connected to the first resonator circuit and the second port is connected to the second resonator circuit. 
     
     
         3 . The RF filter circuit of  claim 2 , wherein:
 the first port is connected to the first inductor, the first capacitor, and the first resonator coupling capacitor; and   the second port is connected to the second resonator coupling capacitor, the third inductor, and the second capacitor.   
     
     
         4 . The RF filter circuit of  claim 1 , wherein the first port is connected to the first resonator circuit and the second port is connected to the first resonator circuit. 
     
     
         5 . The RF filter circuit of  claim 4 , wherein:
 the first port is connected to the first inductor and the first resonator coupling capacitor; and   the second port is connected to the first inductor, the second resonator coupling capacitor, and the first capacitor.   
     
     
         6 . The RF filter circuit of  claim 1 , wherein inductive coupling between the first coupled inductor pair and the second coupled inductor pair is near zero. 
     
     
         7 . The RF filter circuit of  claim 1 , wherein impedance of the second port is 50 Ohms. 
     
     
         8 . The RF filter circuit of  claim 1 , wherein the first resonator circuit, the second resonator circuit, and the first and second resonant coupling capacitors are integrally fabricated on a semiconductor die. 
     
     
         9 . The RF filter circuit of  claim 8 , wherein the first inductor, the second inductor, the third inductor, and the fourth inductor are fabricated as conductive traces etched on to the semiconductor die. 
     
     
         10 . The RF filter circuit of  claim 1 , wherein the first inductor, the second inductor, the third inductor, and the fourth inductor are fabricated with bond wire. 
     
     
         11 . The RF filter circuit of  claim 1 , wherein the first capacitor, the second capacitor, the first resonator coupling capacitor and the second resonator coupling capacitor are metal-insulator-metal (MIM) capacitors. 
     
     
         12 . An RF filter circuit for rejecting one or more spurious components of an input signal, the filter circuit comprising:
 a first filter stage cascaded to a second filter stage, each of the filter stages including:
 a first resonator circuit including a first capacitor and a first coupled inductor pair of a first inductor and a second inductor; 
 a second resonator circuit including a second capacitor and a second coupled inductor pair of a third inductor and a fourth inductor; 
 first and second resonator coupling capacitors each connected to the first resonator circuit and the second resonator circuit; 
   a first port connected to the first filter stage; and   a second port connected to the second filter stage;   wherein the input signal is connected to one of the first port and the second port, and a filtered signal of the input signal passed through the first resonator circuits and the second resonator circuits of both the first filter stage and the second filter stage being output from a other one of the first port and the second port.   
     
     
         13 . The RF filter circuit of  claim 12 , wherein the second resonator circuit of the first filter stage is connected to the first resonator circuit of the second filter stage. 
     
     
         14 . The RF filter circuit of  claim 13 , wherein:
 the first port is connected to the second inductor, the first capacitor, and the first resonator coupling capacitor of the first filter stage;   the second port is connected to the second resonator coupling capacitor, the third inductor, and the second capacitor of the second filter stage;   the third inductor, the second resonator coupling capacitor, and the second capacitor of the first filter stage is connected to the second inductor, the first capacitor, and the first resonator coupling capacitor of the second filter stage.   
     
     
         15 . The RF filter circuit of  claim 13 , wherein:
 the first port is connected to the second inductor, the first capacitor, and the first resonator coupling capacitor of the first filter stage;   the second port is connected to the second resonator coupling capacitor, the first inductor, and the first capacitor of the second filter stage; and   the third inductor, the second resonator coupling capacitor, and the second capacitor of the first filter stage is connected to the second inductor, the first capacitor, and the first resonator coupling capacitor of the second filter stage.   
     
     
         16 . The RF filter circuit of  claim 12 , wherein the first resonator circuit of the first filter stage is connected to the first resonator circuit of the second filter stage. 
     
     
         17 . The RF filter circuit of  claim 16 , wherein:
 the first port is connected to the first inductor, the first capacitor, and the first resonator coupling capacitor of the first filter stage;   the second port is connected to the second resonator coupling capacitor, the first inductor, and the first capacitor of the second filter stage;   wherein the first inductor, the first capacitor, and the second resonator coupling capacitor of the first filter stage is connected to the second inductor, the first capacitor, and the first resonator coupling capacitor of the second filter stage.   
     
     
         18 . An RF filter circuit for rejecting one or more spurious components of an input signal, the filter circuit comprising:
 a first resonator circuit including a first capacitor and a first coupled inductor pair of a first inductor and a second inductor;   a second resonator circuit including a second capacitor and a second coupled inductor pair of a third inductor and a fourth inductor;   a resonator coupling capacitor connected to the first resonator circuit and the second resonator circuit;   a first port connected to at least one of the first resonator circuit and the second resonator circuit; and   a second port connected to at least one of the first resonator circuit and the second resonator circuit;   wherein the input signal is transmitted to one of the first port and the second port, and a filtered signal of the input signal passed through both the first resonator circuit and the second resonator circuit being output from a other one of the first port and the second port.   
     
     
         19 . The RF filter circuit of  claim 18 , wherein the first port is connected to the first resonator circuit and the second port is connected to the second resonator circuit. 
     
     
         20 . The RF filter circuit of  claim 19 , wherein:
 the first port is connected to the first inductor, the first capacitor, and the resonator coupling capacitor; and   the second port is connected to the fourth inductor, the second capacitor, and the resonator coupling capacitor.   
     
     
         21 . The RF filter circuit of  claim 18 , wherein inductive coupling between the first coupled inductor pair and the second coupled inductor pair is near zero. 
     
     
         22 . The RF filter circuit of  claim 17 , further comprising:
 a common inductor connected to the first inductor and the second inductor of the first coupled inductor pair, and to the third inductor and the fourth inductor of the second coupled inductor pair.   
     
     
         23 . The RF filter circuit of  claim 22 , wherein impedance of the second port is 30 Ohms. 
     
     
         24 . The RF filter circuit of  claim 22 , wherein impedance of the second port is 50 Ohms. 
     
     
         25 . The RF filter circuit of  claim 18 , further comprising:
 a second resonator coupling capacitor connected to the first resonator circuit and the second resonator circuit.   
     
     
         26 . The RF filter circuit of  claim 25 , wherein the first coupled inductor pair is further inductively coupled to the second coupled inductor pair. 
     
     
         27 . The RF filter circuit of  claim 26 , wherein the second resonator coupling capacitor is connected to the first capacitor and the second inductor, and to the second capacitor and the third inductor. 
     
     
         28 . The RF filter circuit of  claim 25 , wherein:
 the third inductor, the second capacitor, and the first resonator coupling capacitor is connected to the second port; and   the second resonator coupling capacitor and the second capacitor are connected to the fourth inductor.   
     
     
         29 . The RF filter circuit of  claim 28 , further comprising:
 a common inductor connected to the first inductor and the second inductor of the first coupled inductor pair, and to the third inductor and the fourth inductor of the second coupled inductor pair.   
     
     
         30 . The RF filter circuit of  claim 29 , wherein impedance of the second port is 30 Ohms. 
     
     
         31 . The RF filter circuit of  claim 29 , wherein impedance of the second port is 50 Ohms. 
     
     
         32 . The RF filter circuit of  claim 25 , wherein the first inductor, the second inductor, the third inductor, and the fourth inductor are fabricated as a series of adjacently positioned conductive traces etched on to the semiconductor die as one or more coils, a predefined length of any one of the inductors corresponding to an inductance thereof, and a predefined distance to another conductive trace corresponding to a coupling thereto. 
     
     
         33 . The RF filter circuit of  claim 32 , further comprising an exposed conductive pad connectible to ground, the conductive traces of the first inductor, the second inductor, the third inductor, and the fourth inductor being connected to the exposed conductive pad. 
     
     
         34 . The RF filter circuit of  claim 33 , wherein the exposed conductive pad is spaced from the one or more coils of the conductive traces, an under-path conductive trace connecting the exposed conductive pad to the conductive traces. 
     
     
         35 . The RF filter circuit of  claim 34 , further comprising a solder ball attached to a substrate and electrically connected to one or more of the conductive traces. 
     
     
         36 . The RF filter circuit of  claim 34 , further comprising a copper pillar attached to a substrate and electrically connected to one or more of the conductive traces. 
     
     
         37 . The RF filter circuit of  claim 33 , wherein the exposed conductive pad is positioned within a center region of the coil of the conductive traces. 
     
     
         38 . The RF filter circuit of  claim 37  further comprising a solder ball attached to the exposed conductive pad and electrically connected to one or more of the conductive traces. 
     
     
         39 . The RF filter circuit of  claim 37 , further comprising a copper pillar attached to the exposed conductive pad and electrically connected to one or more of the conductive traces. 
     
     
         40 . The RF filter circuit of  claim 37 , wherein the exposed conductive pad is connected to a ground plane with a via. 
     
     
         41 . The RF filter circuit of  claim 32 , wherein the first capacitor, the second capacitor, and the resonator coupling capacitor are metal-insulator-metal (MIM) capacitors. 
     
     
         42 . The RF filter circuit of  claim 18 , wherein the first coupled inductor pair is further inductively coupled to the second coupled inductor pair. 
     
     
         43 . The RF filter circuit of  claim 42 , wherein the first inductor, the second inductor, the third inductor, and the fourth inductor are fabricated as a series of adjacently positioned conductive traces etched on to the semiconductor die as one or more coils, a predefined length of any one of the inductors corresponding to an inductance thereof, and a predefined distance to another conductive trace corresponding to a coupling thereto. 
     
     
         44 . The RF filter circuit of  claim 43 , further comprising an exposed conductive pad connectible to ground, the conductive traces of the first inductor, the second inductor, the third inductor, and the fourth inductor being connected to the exposed conductive pad. 
     
     
         45 . The RF filter circuit of  claim 44 , wherein the exposed conductive pad is spaced from the one or more coils of the conductive traces, an under-path conductive trace connecting the exposed conductive pad to the conductive traces. 
     
     
         46 . The RF filter circuit of  claim 45 , further comprising a solder ball attached to a substrate and electrically connected to one or more of the conductive traces. 
     
     
         47 . The RF filter circuit of  claim 45 , further comprising a copper pillar attached to a substrate and electrically connected to one or more of the conductive traces. 
     
     
         48 . The RF filter circuit of  claim 44 , wherein the exposed conductive pad is positioned within a center region of the coil of the conductive traces. 
     
     
         49 . The RF filter circuit of  claim 48  further comprising a solder ball attached to the exposed conductive pad and electrically connected to one or more of the conductive traces. 
     
     
         50 . The RF filter circuit of  claim 48 , further comprising a copper pillar attached to the exposed conductive pad and electrically connected to one or more of the conductive traces. 
     
     
         51 . The RF filter circuit of  claim 48 , wherein the exposed conductive pad is connected to a ground plane with a via. 
     
     
         52 . The RF filter circuit of  claim 43 , wherein the first capacitor, the second capacitor, and the resonator coupling capacitor are metal-insulator-metal (MIM) capacitors.