A method to decrease the igniting power of microwave microplasma through adding magnetic field is proposed to further miniaturize low-power microwave micro-plasma source.Simulation on a planar microstrip tapered spiral antenna at 2.45GHz is performed to obtain the optimal structure.Values of S parameters are measured through applying the ring magnets of360,990and 2 840 Gs on the spiral antenna.Finally,the excitation effects of low-power microwave micro-plasma are investigated by changing the magnetic field ...