The latest advances in several emerging technologies such as AI, blockchain, privacy-preserving algorithms used in localization and positioning systems, cloud computing and computer vision all have great potential in facilitating social distancing. Benefits range from supporting people to work from home to monitoring micro- and macro- movements such as contact tracing apps using Bluetooth, tracking the movement and transportation level of a city and wireless positioning systems to help people keep a safe distance by alerting them when they are too close to each other or to avoid congestion. However, implementing such technologies in practical scenarios still faces various challenges.

Negative Group Delay Devices: From concepts to applications introduces the theoretical concept, analysis, design methodology and implementation of negative group delay (NGD). The NGD concept is a recent topic in electrical and electronic engineering research based on an unconventional function; the generation of an output signal seemingly in time-advance of the input signal. The NGD function has been exploited to develop experimental high-performance electronic devices, and novel design features of radio frequency (RF) and microwave electronic devices, such as filters, power dividers and amplifiers. Examples include the realization of non-Foster reactive elements, shortening or reducing delay lines, enhancing the efficiency of feedforward linear amplifiers, improvement of phase shifters accuracy and bandwidth, equalization of electrical interconnect effects for the microwave, digital and mixed signal integrity improvement, and minimizing beam-squint in series-fed antenna arrays.