inductor the inductive stub is very small, the measured matching of the inductive stub is much better than that of the shunt lump inductor. This is probably attributed to fact that it is not easy to simulate a lump component very accurately whereas an inductive stub can be simulated very accurately. The measured insertion loss of the inductive stub is À0.9 dB across all the operating bands, which is much better than the measured insertion loss of the other two cases. Furthermore, it is obvious that the feeding structure with the inductive stub has better ESD protection than that with the lump inductor. Apart from the electrical properties discussed above, the replacement of the lump inductor by the inductive stub is also cost effective, because a lump inductor with a high-quality factor is generally not cheap.
CONCLUSIONSAn inductive stub of matching the feeding line and feeding pad of a penta-band monopole antenna is proposed to replace a lump inductor which has been traditionally used in monopole .pb6 design of mobile devices. In comparison with a lump inductor, the main advantage of the proposed inductive stub can be classified as:• Much improved return loss and insertion loss.• Perfect ESD protection.• Cost effective, especially for large-scale productions.ABSTRACT: A low-cost, low side-lobe Ku-band array of microstrip antennas, which is fed by waveguide, is presented in this article. The 72 corner-fed square patches of the array are arranged in a 6-by-12 configuration. A novel waveguide to microstrip line transition with power divider is employed as a center fed for the array to reduce the loss of the microstrip feed line. The measured gain is 24.1 dB. The side-lobe is below À20 dB, and the return loss at resonant frequency 12.5 GHz is less than À25 dB.