In this paper we introduce a compact integrated antenna that has two feed ports with more than 20 dB isolation between them. The significance of the design is that it can be utilized in compact wireless communication handsets to provide diversity signals or act as a duplexer allowing the receive and transmit signals to be well isolated. The antenna design is based on merging two patch antennas together in combination with capacitive loading so that a compact design can be obtained. Justification for the design is provided by considering the mutual coupling using the reaction principle and finite-dimensional time-domain (FDTD) simulations. Experimental results are also presented for a design that operates in the 2100-2200 MHz band for possible application in forthcoming third-generation wireless systems. Results include radiation patterns, -parameters, and signal correlations between ports so that the diversity performance and isolation characteristics of the antenna can be demonstrated. These show that in typical wireless environments envelope cross correlations of less than 0.1 between the ports are obtained.