To further improve LTE B3 diplexer interband isolation, a high-isolation SAW duplexer module is designed using SIP technology in this study. The module is composed of two SAW duplexers and three couplers. It applies the phase cancellation of the TX-RX path and the isolation of the couplers to improve the isolation between the uplink and downlink of a single SAW duplexer. An impedance-element filter architecture is used to achieve an isolation degree of 51 dB for the proposed module. A broadside stripline multilayer helical coupler-line architecture is adopted to achieve miniaturized integrated 3 dB couplers with a wide operating bandwidth. The results of the developed module show that in the B3 band, for a SAW duplexer measuring 8.0 mm×8.0 mm×2.0 mm, the insertion loss is less than 3.2 dB, the return loss exceeds 13 dB, and the isolation degree exceeds 65 dB; furthermore, it can withstand instantaneous power levels up to 34 dBm.