Thermoacoustic sound generation in the head from high power pulsed microwaves, the microwave auditory effect or the Frey effect that people often hear as buzzes of clicks, may explain “anomalous” health incidents such as Havana syndrome. Directed energy weapons (DEWs) can exploit the Frey effect. This article explores the history and physical basis for the effect and estimates the magnitudes of peak acoustic pressures generated in the head and likely thresholds for adverse effects. The article concludes with discussion about whether thermoacoustic sound pressures generated in the head from high power pulsed microwaves might reasonably explain Havana Syndrome.

Analog computing with microwave signals can enable exceptionally fast computations, potentially surpassing the limits of conventional digital computing. For example, by letting some input signals propagate through a linear microwave network and reading the corresponding output signals, we can instantly compute a matrix-vector product without any digital operations. In this article, we investigate the computational capabilities of linear microwave networks made exclusively of two low-cost and fundamental components: hybrid couplers and phase shifters, which are both implementable in microstrip. To validate our theoretical results, a hardware prototype was designed and fabricated, integrating hybrid couplers and phase shifters to implement the 4 × 4 DFT. By realizing an analog computer through standard microwave components, this work demonstrates a practical pathway toward low-latency, real-time analog signal processing.

Phase-change material switches (PCMSs) have outstanding performance, while the thermal excitation rate of the switch is a critical issue restricting the performance of the PCMS. In order to improve the heat transfer efficiency of the four-port indirectly heated GeTe thin-film PCMS and, in turn, enhance the switching rate, we propose a four-port indirectly heated phase-change switch with a heater placed on the top. This new structure puts the heater on the topmost layer of the switch and transmits the majority of the heat generated in a unidirectional way downward. In the frequency band of 0.1–40 GHz, the insertion loss of the switch after de-embedding is smaller than 0.38 dB, and the isolation degree of the switch is larger than 18.4 dB.

A compact single-layer microwave microfluidic sensor based on a toroidal dipole resonator is proposed for lossy liquid characterization. Four rotationally symmetric split-ring resonators (SRRs) are excited in phase to generate the toroidal mode. Sector-shaped capacitive loading is introduced to maintain a measurable resonance under lossy liquid loading, while interdigital capacitors (IDCs) enhance field–sample interaction. A prototype fabricated on low-cost FR-4 is experimentally validated using ethanol–water mixtures from 0% to 100%. The sensor achieves an average sensitivity of 1.4% and preserves a clearly distinguishable resonance over the investigated concentration range, demonstrating its suitability for compact lossy liquid characterization.