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.
Validation and application of nonlinear elastic model to design triple-beat-free SAW duplexers
We have proposed the nonlinear elastic model for predicting the nonlinear responses of surface acoustic wave (SAW) duplexers, especially for the in-band 3rd order nonlinear distortion, the so-called `triple beat'. This paper validates the nonlinear elastic model by comparing the simulated triple beat responses to the measurements in several designs of SAW duplexers. The model precisely simulates the every measurement result with an accuracy as high as a few dB. This model is applied to design the highly linear SAW duplexers for 1.9 GHz Personal Communications Service (PCS). The developed SAW duplexer achieves the extremely high linearity of approximately -90 dBc in the triple beat test, which is 20 dB better than the conventional duplexer keeping the equivalent filter characteristics and same packaging size. To the best of our knowledge, this is the first PCS SAW duplexer which satisfies the triple beat specification required in CDMA2000.
Human reproduction: irrational but in most cases morally defensible
While I am inclined to agree that in most cases a choice to become pregnant and bring to birth a child is an irrational choice, unlike Professor Hayry,1 I believe that choosing to do so is far from being necessarily immoral. In fact I will argue that it is often these irrational (but morally defensible) choices which make human life the valuable commodity many of us believe it is.

Hayry argues that not only is the choice to have children always an irrational choice, but also it is necessarily an immoral choice. Thus, for Hayry “human reproduction is fundamentally immoral”.1 He claims it is important to point out to prospective parents that their urge to have children is irrational. From this, he argues, it follows that once this is accepted the use of advance technologies to assist conception should be reassessed, and furthermore, the irrationality and immorality of having children should become a legitimate part of guidance given to those expressing a wish to have children.

According to Hayry the reason it is irrational and immoral to choose to bring to birth a child is that “having a child can always realistically lead to the worse possible outcome, when the alternative is not having a child”.1 He argues that when people consider having children they are faced with the choice between deciding not to have children and thus harming or benefiting no-one (this, it is argued has a value of zero), or having children where this life may be good or bad, and thus the value of this choice can be …