ISM 433-MHz Miniaturized Antenna Using the Shielding Box of Mobile Terminals

A miniaturized monopole antenna for ISM 433-MHz frequency band is designed, fabricated, and measured. The whole structure proposed in this letter consists of a metal shielding box for transceiver circuit, a rectangular ground for battery, and a meander-line monopole. The size of the structure is 51 × 82 mm², and the area left of the antenna itself is just about 49 × 13 mm². To make the antenna work in such a small area, and maintain good performance, the metal shielding box of the transceiver circuit in this work is connected to the meander-line monopole. Actually, the shielding box does not serve as a part of the ground, but a part of the antenna itself, which plays an important role in matching and increasing the antenna´s electrical length. Meanwhile, no additional area is needed compared to the conventional design. The measured - 10-dB bandwidth is 5 MHz. The comparison between the traditional design and the proposed design as well as the critical parameter study is presented in this letter.