Abstract: To address the combined requirements of miniaturization, wide-band performance, and high-power handling in X-band phased array radar systems, a compact microstrip isolator is proposed and implemented. The device is based on a circulator structure constructed with a nested ceramic-ferrite composite substrate, and its impedance bandwidth is enhanced using a dual Y-junction topology, dual-stub matching networks, and a triangular central conductor. To manage power dissipation at port 3, an arched tantalum nitride（TaN） thin-film load is designed, and its thermal distribution and interface efficiency are optimized through coupled electromagnetic-thermal simulations. With an overall size of 5 mm×6 mm×0.4 mm（including the matching load but excluding external magnets）, the isolator operates over 7.7-12.4 GHz, achieving a relative bandwidth of 46.7%, an isolation of ≥16 dB, a voltage standing wave ratio（VSWR） of ≤1.35, and a maximum insertion loss of ≤0.4 dB. Under 35 W average input power with a 25% duty cycle, the peak device temperature remains below 70 ℃, demonstrating excellent thermal stability and power endurance. The device features an ultra-low profile of 0.4 mm, approximately 16% of the thickness reported in comparable designs, while exhibiting significantly improved bandwidth performance. These characteristics make the proposed isolator suitable for integration into radar T/R modules and other compact systems operating in complex electromagnetic environments. In the coal mine wide-band wireless communication system, it can effectively improve the equipment integration and anti-interference ability.