Study on High-Isolation SAW Duplexer with On-Chip SAW Compensation Circuit Optimized for Isolated Multiple Frequency Bands

High isolation surface acoustic wave (SAW)duplexer and bulk acoustic wave (BAW)duplexers are in high demand. To satisfy the requirements, we have developed a method of isolation improvement at multiple isolated frequency bands in an RF SAW duplexer. These duplexers have leakage signal paths between terminals due to stray elements. By fixing the leakage using an on-chip compensation path with proper phase and amplitude, high isolation can be achieved at an arbitrary frequency. We analyzed this concept in detail for a long-term-evolution (LTE)Band-I SAW duplexer for transmitter (Tx)and receiver (Rx)band isolation. Results showed that an around 10-dB improvement of isolation in both of Tx and Rx bands were obtained without sacrificing other properties.