Planar transformer

Abstract

An integrated transformer structure is disclosed. In one embodiment, a circuit is disclosed for a transformer circuit including two metallization layers and other layers, a conducting spiral, a gapped spiral, two radial conductors and various short bridging conductors and vias. Superior transformer price/performance is obtained without the use of more than two metallization layers. The invention may be embodied in GaAs and/or other technologies.

1 . A transformer circuit consisting essentially of 
 a first metallization layer;    a second metallization layer;    a plurality of conducting vias connecting the metallization layers and    a plurality of further layers other than metallization layers    wherein:    a first winding is formed substantially consisting of a first conducting spiral formed in the first metallization layer, a first substantially radial conductor formed in the second metallization layer and a first via connecting the first conducting spiral to the first substantially radial conductor;    and further wherein: 
 a second winding is formed in proximity to the first winding, the second winding substantially consisting of a second substantially radial conductor, a gapped spiral formed in the second metallization layer, a plurality of short conductors in the first metallization layer, the short conductors bridging across the substantially radial conductors and a plurality of other vias connecting the gapped spiral to the short conductors.  
   
   
   
       2 . The circuit of  claim 1  wherein: 
 further layers comprises a GaAs substrate.    
   
   
       3 . The circuit of  claim 2  wherein: 
 the spirals have diameters of about 50 to 500 microns.    
   
   
       4 . The circuit of  claim 2  wherein: 
 the transformer circuit has a total thickness of about 0.3 to 10 microns.    
   
   
       5 . The circuit of  claim 1  wherein: 
 the first and second windings have a coupling factor higher than 0.8.    
   
   
       6 . The circuit of  claim 1  wherein: 
 the self inductances of the first and second windings are substantially equal.    
   
   
       7 . The circuit of  claim 2  wherein: 
 the first and second windings have a coupling factor higher than 0.8.    
   
   
       8 . The circuit of  claim 2  wherein: 
 the self inductances of the first and second windings are substantially equal.