A mobile phone data card for reducing a specific absorption rate,SAR, comprising: an antenna configured to transmit and receive signals; a radio frequency,RF, substrate having a rectangular shape with two short sides and two long sides, the RF substrate further comprising a metallization layer that constitutes a ground-plane of the antenna; and a feed source configured to excite the antenna and connected between the RF substrate and the antenna, the feed source being arranged at a first corner on a first short side of the RF substrate; wherein a first hollow portion is arranged at a second corner on the first short side of the RF substrate, the first hollow portion having a rectangular shape comprising two rectangular outer sides, the first hollow portion being provided with a first metal strip having a bent shape substantially fitting with the two rectangular outer sides of the first hollow portion, the first metal strip having an end connected with the first short side of the RF substrate, and another end as a free end; wherein a first electrical length formed from the feed source to the free end of the first metal strip is equal to a second electrical length formed from the feed source to a second short side along a long side on which the first corner is located; and wherein a second hollow portion is arranged on the second short side at a third corner in a diagonal line to the first corner, the second hollow portion having a rectangular shape comprising two rectangular outer sides, the second hollow portion being provided with a second metal strip having a bent shape substantially fitting with the two rectangular outer sides of the second hollow portion, the second metal strip having an end connected with the second short side of the RF substrate, and another end as a free end; wherein a third electrical length is formed from the feed source to a point of the second hollow portion which is in the shortest distance to the feed source, the third electrical length being equal to the second electrical length; an antenna configured to transmit and receive signals; a radio frequency,RF, substrate having a rectangular shape with two short sides and two long sides, the RF substrate further comprising a metallization layer that constitutes a ground-plane of the antenna; and a feed source configured to excite the antenna and connected between the RF substrate and the antenna, the feed source being arranged at a first corner on a first short side of the RF substrate; wherein a first hollow portion is arranged at a second corner on the first short side of the RF substrate, the first hollow portion having a rectangular shape comprising two rectangular outer sides, the first hollow portion being provided with a first metal strip having a bent shape substantially fitting with the two rectangular outer sides of the first hollow portion, the first metal strip having an end connected with the first short side of the RF substrate, and another end as a free end; wherein a first electrical length formed from the feed source to the free end of the first metal strip is equal to a second electrical length formed from the feed source to a second short side along a long side on which the first corner is located; and wherein a second hollow portion is arranged on the second short side at a third corner in a diagonal line to the first corner, the second hollow portion having a rectangular shape comprising two rectangular outer sides, the second hollow portion being provided with a second metal strip having a bent shape substantially fitting with the two rectangular outer sides of the second hollow portion, the second metal strip having an end connected with the second short side of the RF substrate, and another end as a free end; wherein a third electrical length is formed from the feed source to a point of the second hollow portion which is in the shortest distance to the feed source, the third electrical length being equal to the second electrical length;