Impedance transformation circuit and wireless communication apparatus

1. An impedance transformation circuit comprising:

a transformer including a first coil element and a second coil element that are magnetically coupled and disposed in a stacked element including a plurality of base material layers stacked on each other;

a feeder port connected to a first end of the first coil element;

an antenna port connected to a second end of the first coil element and a first end of the second coil element; and

a ground port connected to a second end of the second coil element; wherein

the first coil element includes a first loop-shaped conductor and a second loop-shaped conductor disposed in different layers of the stacked element, respectively;

the second coil element includes a third loop-shaped conductor and a fourth loop-shaped conductor disposed in different layers of the stacked element, respectively;

the first loop-shaped conductor, the second loop-shaped conductor, the third loop-shaped conductor, and the fourth loop-shaped conductor have a same or substantially a same shape in a top view from a stacking direction;

the first loop-shaped conductor and the second loop-shaped conductor are sandwiched in the stacking direction between the third loop-shaped conductor and the fourth loop-shaped conductor; and

at least portions of the first loop-shaped conductor and the second loop-shaped conductor are connected in parallel.

2. A wireless communication apparatus comprising a wireless communication circuit including therein the impedance transformation circuit according to claim 1 .

3. The wireless communication apparatus according to claim 2 , wherein

a parallel circuit includes a portion of the first loop-shaped conductor and a portion or all of the second loop-shaped conductor;

a remaining portion of the first loop-shaped conductor is connected in series with the parallel circuit; and

when the parallel circuit includes the portion of the second loop-shaped conductor, a remaining portion of the second loop-shaped conductor is also connected in series with the parallel circuit.

4. The wireless communication apparatus according to claim 2 , wherein a conductive pattern connected in series with one of the third loop-shaped conductor and the fourth loop-shaped conductor is provided on a formation layer of one of the first loop-shaped conductor and the second loop-shaped conductor.

5. The wireless communication apparatus according to claim 2 , wherein the third loop-shaped conductor and the fourth loop-shaped conductor are connected in series.

6. The wireless communication apparatus according to claim 2 , wherein each of the first loop-shaped conductor, the second loop-shaped conductor, the third loop-shaped conductor, and the fourth loop-shaped conductor is loop-shaped including a single or substantially a single turn per layer.

7. The wireless communication apparatus according to claim 2 , wherein at least any of the first loop-shaped conductor, the second loop-shaped conductor, the third loop-shaped conductor, and the fourth loop-shaped conductor define a loop including a plurality of turns over a plurality of base material layers.

8. The wireless communication apparatus according to claim 2 , wherein at least any of the first loop-shaped conductor, the second loop-shaped conductor, the third loop-shaped conductor, and the fourth loop-shaped conductor are provided in a plurality of base material layers and are connected in parallel.

9. The wireless communication apparatus according to claim 2 , wherein a plurality of sets of the first loop-shaped conductors and the second loop-shaped conductors are stacked.

10. The impedance transformation circuit according to claim 1 , wherein

a parallel circuit includes a portion of the first loop-shaped conductor and a portion or all of the second loop-shaped conductor;

a remaining portion of the first loop-shaped conductor is connected in series with the parallel circuit; and

when the parallel circuit includes the portion of the second loop-shaped conductor, a remaining portion of the second loop-shaped conductor is also connected in series with the parallel circuit.

11. The impedance transformation circuit according to claim 1 , wherein a conductive pattern connected in series with one of the third loop-shaped conductor and the fourth loop-shaped conductor is provided on a formation layer of one of the first loop-shaped conductor and the second loop-shaped conductor.

12. The impedance transformation circuit according to claim 1 , wherein the third loop-shaped conductor and the fourth loop-shaped conductor are connected in series.

13. The impedance transformation circuit according to claim 1 , wherein each of the first loop-shaped conductor, the second loop-shaped conductor, the third loop-shaped conductor, and the fourth loop-shaped conductor is loop-shaped including a single or substantially a single turn per layer.

14. The impedance transformation circuit according to claim 1 , wherein at least any of the first loop-shaped conductor, the second loop-shaped conductor, the third loop-shaped conductor, and the fourth loop-shaped conductor define a loop including a plurality of turns over a plurality of base material layers.

15. The impedance transformation circuit according to claim 1 , wherein at least any of the first loop-shaped conductor, the second loop-shaped conductor, the third loop-shaped conductor, and the fourth loop-shaped conductor are provided in a plurality of base material layers and are connected in parallel.

16. The impedance transformation circuit according to claim 1 , wherein a plurality of sets of the first loop-shaped conductors and the second loop-shaped conductors are stacked.