Microwave-Induced Thermo-Acoustic Tomography (MI-TAT) is a promising technique in biologic tissue imaging. It has predominant advantages in both contrast and resolution compared with conventional microwave or ultrasound imaging system for malignant tumors. In this paper, an integrated prototype MITAT system is briefly introduced. And Time Reversal Mirror (TRM) imaging technique based on Pseudo-Spectrum Time Domain (PSTD) is also first time applied to MITAT system. Two tissue strips of porcine muscle are used as targets in the MITAT experiment to demonstrate the imaging potential of the system. TRM and Filtered Back-Projection (FBP) imaging results are both presented to compare the performance of the TRM and other imaging techniques in contrast and resolution for MITAT.

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The design of compact unbalanced-/balanced-to-unbalanced diplexer (U2U/B2U) based on full dual-mode dielectric resonator (DR) is investigated for the first time. The relationships of the external quality factors (Q e ) under the two modes are analyzed. It is found that the Q e of two modes can be controlled independently, which makes the design procedure simple and efficient. Based on the analysis, both of the proposed U2U and B2U diplexer can be easily built by properly adding feeding probes for the DR without increasing the circuit size by altering the location of the feeding probes according to the distribution of the electromagnetic fields. To verify the proposed design concept, the diplexers mentioned above are simulated, implemented and measured. The isolation is achieved by the orthogonality between modes while the low insertion loss is obtained due to the high unloaded quality factor (Q u ) of the dual-mode DR. The measurements are in accordance with the simulated results, showing low loss and good selectivity.INDEX TERMS Miniaturization, dual-mode dielectric resonator (DR), diplexer, design approach, unbalanced-to-unbalanced (U2U), balanced-to-unbalanced (B2U).

Robustness of stability with respect to small delays, e.g., motivated by feedback systems in control theory, is of great theoretical and practical important, but this property does not hold for many systems. In this paper, we introduce the conception of robustness with respect to small time-varying delays for exponential stability of the non-autonomous linear systems. Sufficient conditions are given for the non-autonomous systems to be robust, and examples are provided to illustrate that the conditions are satisfied for a large class of the non-autonomous parabolic systems.

In this article, a balanced filtering power divider (FPD) that allows for operational agility of the bandwidth (BW) is presented. The differential-mode power dividing and high common-mode (CM) suppression can be realized by microstrip-to-slotline transition. Two slotline open stubs with different lengths are added in shunt to the main slotline for the transition, which can not only introduce transmission poles for extending and controlling transition BW, but also generate two extra transmission zeros (TZs) near to the passband edges, featuring good filtering response. The two transmission poles can be independently tunable by loading varactors to the open ends of slotline stubs and two TZs will be changed accordingly so that the filtering passband BW is electrically tunable. To verify the theoretical prediction, a prototype of tunable balanced FPD is fabricated and measured. The measured results show that the 3-dB fractional bandwidth (FBW) of the passband varies from 5.6% to 12.6%, meaning more than a double tuning range for the FBW, and the CM suppression is better than 40 dB across the frequency band of interest. K E Y W O R D Sbalanced filtering power divider, bandwidth agility, common mode suppression, differential mode