Abstract: An improved single sideband modulator is introduced in this paper. Conventional single sideband modulator can achieve 25 dB or so undesired image sideband rejection. the improved single sideband modulator uses the principle of the I/Q quadrature network, combines two conventional single sideband modulators, and obtains a single sideband modulator achieving 35 dB or so undesired image sideband rejection.