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A single-pot atom-transfer radical polymerization under microwave irradiation was first used to successfully synthesize polyacrylonitrile. This was achieved with FeBr 2 /isophthalic acid as the catalyst and 2-bromopropionitrile as the initiator. With the same experimental conditions, the apparent rate constant under microwave irradiation was higher than that under conventional heating. An FeBr 2 /isophthalic acid ratio of 1:2 not only gave the best control of molecular weight and its distribution but also provided a rather rapid reaction rate. The polymers obtained were end-functionalized by bromine atoms, and they were used as macroinitiators to proceed the chain extension polymerization.

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A compact planar quasi‐Yagi antenna with a wideband microstrip‐to‐slotline transition and a modified bow‐tie driver is designed with an enhanced bandwidth for precise indoor positioning applications. A compact interdigital capacitor loaded loop resonator with a high quality factor is placed inside the ring resonator at the end of the antenna's slot to realise band‐notched characteristics over a frequency range of 5.1–6.3 GHz, thus avoiding interference from wireless local area networks (WLANs) and dedicated short‐range communications (DSRCs). Measured results show that the proposed antenna obtains a relative impedance bandwidth, determined by the voltage standing wave ratio <2, higher than 122.6% (3.0–12.5 GHz) and a gain of 4.9–7.8 dBi outside of the stop band.

Abstract-A novel Vivaldi antenna utilizing a tapered slot edge with a stepped structure (TSESS) to achieve miniaturization is presented in this paper. Compared with a conventional Vivaldi antenna of the same size, the proposed TSESS significantly extends the low-end bandwidth limitation and also improves the low-end antenna gain and radiation characteristics. The proposed antenna is fabricated and tested for validating the reliability of the design. The measured results show reasonable agreement with simulated ones. Moreover, a good time-domain response is indicated from the measured group delay, showing that the antenna meets the requirements of a UWB system.