The effects of antenna shape and magnetic field configuration on thrust performance in a 30W class miniature microwave discharge ion thruster were investigated with the objective of improving its thrust performance. The ion beam currents were measured for three different antenna configurations: disc, star, and cross. The results showed that the optimum antenna shape depends on the desired mass flow level because of the tradeoff between microwave-plasma coupling efficiency and surface area recombination. The ion beam current with various magnitude of magnetic field was measured, since magnetic confinement and microwave-plasma coupling could be affected by the magnetic field configuration. The ion beam current was increased with increasing the number of magnets, though under too much magnitude of magnetic field, the thruster cannot be ignited. So, there is an optimum magnitude of magnetic field. The thrust performance of the miniature microwave discharge ion thruster, i.e., propellant utilization, and ion beam production cost were 0.97 and 600W/A, respectively, at mass flow rate of 0.018mg/s, and incident microwave power of 8W.
