This paper presents a compact pentagon shaped monopole microstrip patch antenna, which has been modified to improve its performance. All sides of pentagon patch are truncated and offset feeding is provided to enhance the bandwidth. Defected Ground Structure (DGS) is used which has two rectangular slots of quarter wavelength opposite to each other, and a notch beneath the feedline on the partial ground plane. These slots on the ground plane improves the gain and return loss of the design. The analysis is performed and results are obtained using Ansoft High Frequency Structure Simulator (HFSS). Various parameters which include impedance bandwidth, gain, efficiency, radiation pattern and current distribution of the antenna are studied. The performance of proposed antenna is compared with classical antenna design, both having same operating frequency of 7.4 GHz. Results obtained from the simulation shows impedance bandwidth of 16.65 (3.85-20.5 GHz) GHz, which is 60% enhanced bandwidth as compared to classical antenna, maximum gain of 6.85 dB at 14.35 GHz, peak return loss of -41.6 dB at 7.2 Ghz and good radiation pattern is observed at frequencies of 7.34, 10.4, and 19 GHz. Application of this antenna covers Ultrawide Band (UWB), X Band and Ku Band, and it can be used efficiently for mobile or satellite communication.