Multi-band monopole antenna with improved HAC performance
A multi-band monopole antenna includes a first metal radiator and a second metal radiator extending in a same direction and arranged in parallel for exciting a high frequency band, and a detoured wire pattern connected between the feed end of the first metal radiator and the connection end of the second metal radiator for exciting a low frequency band. The detoured wire pattern has a, circuit path length longer than one half of the high frequency band λ/2 so that the phase difference on current between the feed end of the first metal radiator and the connection end of the second metal radiator is about π(180-degrees); the electric fields generated at the lower sides of the first metal radiator and the second metal radiator have approximately the same size but reversed phases and the magnetic fields have the same characteristics; when the reversed phases of electromagnetic waves excited by the first and second metal radiators reach the HAC test surface, they cause a destructive interference, thereby improving hearing aid compatibility performance of the multi-band monopole antenna.
1. A multi-band monopole antenna comprising:
a first metal radiator and a second metal radiator arranged in a pair and adapted to excite a high frequency band, said first metal radiator and said second metal radiator being kept apart at a distance and extending in one same direction, said first metal radiator comprising a feed end, said second metal radiator comprising a connection end, said feed end and said connection end being disposed at a same side relative to said first metal radiator and said second metal radiator; and
a detoured wire pattern disposed at one side relative to said first metal radiator and said second metal radiator and adapted to excite a low frequency band, said detoured wire pattern comprising a first end connected with said feed end of said first metal radiator and a second end connected with said connection end of said second metal radiator;
wherein said detoured wire pattern has a circuit path length longer than one half of said high frequency band λ/2 so that the phase difference on current between the feed end of said first metal radiator and the connection end of said second metal radiator is about π; when the reversed phases of electromagnetic waves excited by said first metal radiator and said second metal radiator reach the HAC test surface, they cause a destructive interference, thereby improving hearing aid compatibility performance of the multi-band monopole antenna.
2. The multi-band monopole antenna as claimed in claim 1 , wherein said first metal radiator and said second metal radiator are arranged in parallel.
3. The multi-band monopole antenna as claimed in claim 1 , wherein the gap between said first metal radiator and said second metal radiator is within 0.2 λ of said high frequency band.
4. The multi-band monopole antenna as claimed in claim 1 , wherein the size of the multi-band monopole antenna is 35 mm×18 mm×8 mm; the length of said first metal radiator is 30 mm; the length of said second metal radiator is 32 mm; the length of said detoured wire pattern is 71 mm; the gap between said first metal radiator and said second metal radiator is 11 mm.
5. The multi-band monopole antenna as claimed in claim 1 , which is installed in a clearance zone on a printed circuit board, said printed circuit board having the size of 2 mm height, 110 mm length and 50 mm width, said clearance zone having the size of 21 mm×50 mm.
6. The multi-band monopole antenna as claimed in claim 1 , wherein said detoured wire pattern extends in horizontal.
7. The multi-band monopole antenna as claimed in claim 1 , wherein said detoured wire pattern extends in vertical.