Printed Single-Strip Monopole Using a Chip Inductor for Penta-Band WWAN Operation in the Mobile Phone

A single-strip monopole capable of generating two wide operating bands at about 900 and 1900 MHz covering GSM850/900/1800/1900/UMTS penta-band WWAN operation in the mobile phone is presented. The monopole has a simple structure of an inverted-L shape to be printed on the no-ground region of the system circuit board of the mobile phone. By simply embedding a chip inductor at the proper position in the strip monopole, the first two resonant modes of the monopole can have a frequency ratio of about 1 to 2 (instead of 1 to 3 for the traditional monopole) to respectively cover the desired wide 900 and 1900 MHz bands. In addition, the total strip length can be less than the required 0.25 wavelength (about 0.17 wavelength in this design) for the fundamental resonant mode excitation of the proposed monopole; this behavior is owing to the embedded chip inductor compensating for the increased capacitance seen at the feeding point with the decreasing strip's resonant length. The SAR of the proposed monopole placed at the bottom position of the mobile phone is found to meet the SAR limit for practical applications.