A new simulation model for nonlinearity of SAW resonator filters
In the design stage of SAW duplexers for 3G handsets, a new simulation method which is predictable for the frequency characteristics of the nonlinearity has been desired in order to improve the intermodulation distortion and/or the triple beet. Recent SAW duplexers consist of not only ladder type filters but also DMS filters. In this paper, a novel simulation method of nonlinear signals, which is applicable for not only one-port SAW resonators but also DMS filters, has been proposed. Basic calculation model of the nonlinear current is derived by introducing nonlinear terms to the piezoelectric fundamental equation. In order to apply this model to IDT structure, we extend the equation to summation model of multi point electrodes. Good agreement between calculated results and measured values has been obtained.
Saw duplexer design for WCDMA system
Some relations between sensitivity performances and duplexer performances (losses, isolations between Tx and Rx terminals) are obtained. We simulate system noise figure levels from duplexer performances and low noise amplifier parameters by using a nonlinear NF model at the viewpoint of a system design.
IP2 and IP3 Nonlinearity Specifications for 3G/WCDMA Receivers
In 3G/WCDMA mobile handsets, the direct conversion receiver (DCR) architecture is commonly used due to its simplicity and low cost, where interstage filters are completely eliminated. However, with less filtering, the linearity requirement for a direct conversion receiver is very critical. It is essential to define system linearity requirements properly for the receiver to meet the performance requirements. In FDD mode, the transmitter and receiver are continuously working at the same time, and the transmitted signal leaks into the receiver due to the limited TX-to-RX isolation of the duplexer. The transmitter is possibly the strongest interferer for the companion receiver in the handset, and poses the most stringent linearity requirement for the receiver.