In this paper, a compact microstrip planar monopole antenna with a wide tunable frequency band is proposed and developed for interweave cognitive radio (CR) communication applications. Tunability is achieved by integrating a tunable folded arms open loop resonator bandpass filter with an ultra-widband (UWB) microstrip monopole antenna. The technique depends on centrally loading the folded arms open loop resonator with a single lumped varactor diode, decreasing the varactor capacitance results in increasing the miniaturized even resonant mode of the folded arms open loop resonator while keeping the odd-mode fixed. The filter-antenna is adaptable and compact in terms of the availability of several tunable bands. Moreover, the simple biasing of the varactor diode does not have a significant effect on the filtenna performance. Simulation results show that the proposed design is capable of tuning over a continuous wide operating band of 3.18 GHz covering a large band for interweave CR communication with a 52 % frequency tuning range from 4.6 to 7.8 GHz. Furthermore, the normalized radiation patterns are steady over the operating frequency bands. The frequency parameters and radiation patterns of the proposed filter-antenna are successfully optimized with numerical experimentation approaches using 3D full-wave electromagnetic simulator.