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A method to excite dual band for a microstrip antenna on a two-layer substrate by combining the proximity feed and the inset feed in a simple way is presented. Both linearly polarised and circularly polarised (CP) dual-band waves can be excited. The CP antenna consists of two stacked perturbed patches. If the lower patch were directly connected to the feed line, it is hard to form two bands. A single resonant frequency is found dependent on the size of the lower patch and is insensitive to the loading effect of the upper patch. The lower patch is inset coupled to the feed line. The authors found that two bands can easily be excited. To demonstrate the idea, a dual-band global positioning system antenna is designed and tested. The achieved impedance bandwidths are 60 MHz centred at 1215 and 65 MHz centred at 1563 MHz. The 3 dB axial-ratio bandwidths are 15 MHz centred at 1228 and 20 MHz centred at 1575 MHz.