This paper presents a novel broadband rectenna for ambient wireless energy harvesting over the frequency band from 1.8 to 2.5 GHz. First of all, the characteristics of the ambient radio-frequency energy are studied. The results are then used to aid the design of a new rectenna. A novel two-branch impedance matching circuit is introduced to enhance the performance and efficiency of the rectenna at a relatively low ambient input power level. A novel broadband dual-polarized cross-dipole antenna is proposed which has embedded harmonic rejection property and can reject the 2 nd and 3 rd harmonics to further improve the rectenna efficiency. The measured power sensitivity of this design is down to -35 dBm and the conversion efficiency reaches 55% when the input power to the rectifier is -10 dBm. It is demonstrated that the output power from the proposed rectenna is higher than the other published designs with a similar antenna size under the same ambient condition. The proposed broadband rectenna could be used to power many low-power electronic devices and sensors and found a range of potential applications.

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Objective. This study explores how various measures, ranging from assimilation, to human capital, to family capital, and Holland's career-development theories, affect Asian-American students' choice of college majors. To test our hypotheses, we examine choice of college major using a unique measure based on the early earning potential of a large number of specific majors. Methods. Our data come from the National Education Longitudinal Study of 1988 (NELS88). We use the Heckman selection approach to adjust for the nonrandom selection of college attendance and choice of college majors. Results. The findings of the study show little difference between Asian men and white men. On the other hand, there are significant differences among women. Conclusions. Chinese, Filipino, and Southeast Asian women are all more likely to choose more lucrative college majors than white women, controlling for all the other factors. Interestingly, effects of our assimilation, psychological, and some of the family capital measures are quite different for men than for women. n Direct correspondence to Chunyan Song, Department of Sociology, Arizona State University, PO Box 874802, Tempe, AZ 85287-4802 hchunyan.song@asu.edui. The firstnamed author will share all data and coding materials with those wishing to replicate the study.