In this letter, a compact single-layer, single-feed, dual-frequency microstrip antenna with a high frequency ratio is proposed. This antenna has a broadside and symmetrical radiation patterns suitable for space-borne applications. The prototype was fabricated on a Rogers RT/duroid 5880 substrate with a relative permittivity of 2.2 and thickness of 1.58 mm. The dual-band behavior is achieved by a shorting pin at 1.7-1.706 and 8.011-8.277 GHz with the frequency ratio of 4.75. In addition, the antenna is miniaturized by 46% compared to the conventional rectangular patch.