No abstract

This work presents an easy way to improve the low-frequency properties in a small-size LTE/WWAN smartphone antenna by just loading a soft magnetic ferrite film on the strong radiation area. The base non-magnetic antenna, which only takes up an 11 mm × 30 mm no-ground space, can achieve hexa-band operation covering 822–914/1710–3244 MHz bands by co-designing a meandering strip and a T-shaped feeding strip. With loading a small-size ferrite film (2 mm × 15 mm) at the strong radiation strip, the frequencies can be shifted to cover the range of 692–1191/1698–3020 MHz, which shows a fully covering of octa-band operation, especially including the best long-term-evolution band, LTE700, without enlarging the size of base antenna. In addition, the radiation characteristics of the magnetic antenna with ferrite film loading show a limited change at upper bands (1710–2690 MHz) but an acceptable level at lower bands (698–960 MHz). Both experimental and simulated results have been taken out and shown the consistent tendency. This optimization method of low-frequency properties by introducing a commercial ferrite film on the antenna has provided a simple and convenient way to solve the frequency deviation in the practical smartphone applications.

A nona‐band narrow‐frame antenna with a defected ground structure for mobile phone applications is presented in this article. From the analysis of the structure, the coupled‐fed antenna mainly consists of four parts: bending feeding strip, coupling shorted strip, copper plate and defected ground structure. It can effectively cover LTE700/GSM850/GSM900/DCS1800/PCS1900/UMTS2100/LTE2300/LTE2500 and the ninth band on 3300‐4200 MHz (including LTE3500), which may be applied to the future 5G. The size of the nona‐band antenna is 80 × 7.5 × 5 mm3, and the defected ground structure is only 55 × 0.5 mm2. This structure effectively widens the bandwidth of the low‐frequency band and realizes 2G/3G/4G and possible coverage of the 5G operating band without loading the lumped elements. Thus, it is suitable for smartphone application. A prototype of the proposed antenna is manufactured and measured. The measured −6 dB impedance band‐widths in the low, mid and high bands are 340 MHz (630‐970 MHz), 1410 MHz (1510‐2920 MHz) and 1060 MHz (3160‐4220 MHz), respectively. In addition, the efficiency of the antenna is greater than 60% in most of the working frequency bands, and the antenna has good radiation performances.

The solar trough concentrator is used to increase the solar radiation intensity on absorbers for water heating, desalination, or power generation purposes. In this study, optical performances of four solar trough concentrators, viz. the parabolic trough concentrator (PTC), the compound parabolic concentrator (CPC), the surface uniform concentrator (SUC), and the trapezoid trough concentrator (TTC), are simulated using the Monte Carlo Ray Tracing method. Mathematical models for the solar trough concentrators are first established. The solar radiation distributions on their receivers are then simulated. The solar water heating performances using the solar trough concentrators are finally compared. The results show that, as a high-concentration ratio concentrator, the PTC can achieve the highest heat flux, but suffers from the worst uniformity on the absorber, which is only 0.32%. The CPC can generate the highest heat flux among the rest three low-concentration ratio solar trough concentrators. Compared with the PTC and the CPC, the TTC has better uniformity, but its light-receiving ratio is only 70%. The SUC is beneficial for its highest uniformity of 87.38%. Thermal analysis results show that the water temperatures inside the solar trough concentrators are directly proportional to their wall temperature, with the highest temperature rise in the PTC and the smallest temperature rise in the TTC. The solar trough concentrators’ thermal deformations are positively correlated to their wall temperatures. The radial deformation of the SUC is much larger than those of other solar trough concentrators. The smallest equivalent stress is found in the SUC, which is beneficial to the long-term operation of the solar water heating system.