| 摘要 |
A balancing/unbalancing (balun) structure for operating at frequency f<SUB>1 </SUB>includes a microstrip printed circuit board (PCB). A balun on the PCB includes two input ports are coupled to a differential signal. An isolated port is connected to ground through a matched resistance. An output port is coupled to a single-ended signal corresponding to the differential signal. A plurality of traces on the PCB connect the two input ports, the load connection port and a tap point to the output port. A f<SUB>2 </SUB>rejection filter on the PCB is wrapped around the balun and includes a first folded element with a transmission length of lambda<SUB>2</SUB>/4 and connected to the output port. A second folded element has a transmission length of lambda<SUB>2</SUB>/4 and connected to the tap point. A third folded element connects the tap point to the output port and has a transmission length of lambda<SUB>2</SUB>/4.
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