Wideband RCS Reduction of Microstrip Array Antenna Based on Absorptive Frequency Selective Surface and Microstrip Resonators

An approach for wideband radar cross section (RCS) reduction of a microstrip array antenna is presented and discussed. The scheme is based on the microstrip resonators and absorptive frequency selective surface (AFSS) with a wideband absorptive property over the low band 1.9–7.5 GHz and a transmission characteristic at high frequency 11.05 GHz. The AFSS is designed to realize the out-of-band RCS reduction and preserve the radiation performance simultaneously, and it is placed above the antenna with the operating frequency of 11.05 GHz. Moreover, the microstrip resonators are loaded to obtain the in-band RCS reduction. As a result, a significant RCS reduction from 1.5 GHz to 13 GHz for both types of polarization has been accomplished. Compared with the reference antenna, the simulated results exhibit that the monostatic RCS of the proposed array antenna in x- and y-polarization can be reduced as much as 17.6 dB and 21.5 dB, respectively. And the measured results agree well with the simulated ones

A hydrogel-based optical fibre fluorescent pH sensor for observing lung tumor tissue acidity

Technologies for measuring physiological parameters in vivo offer the possibility of the detection of disease and its progression due to the resulting changes in tissue pH, or temperature, etc. Here, a compact hydrogel-based optical fibre pH sensor was fabricated, in which polymer microarrays were utilized for the high-throughput discovery of an optimal matrix for pH indicator immobilization. The fabricated hydrogel-based probe responded rapidly to pH changes and demonstrated a good linear correlation within the physiological pH range (from 5.5 to 8.0) with a precision of 0.10 pH units. This miniature probe was validated by measuring pH across a whole ovine lung and allowed discrimination of tumorous and normal tissue, thus offering the potential for the rapid and accurate observation of tissue pH changes.</p