Follow the links to read the full papers in the IET Digital Library.
A planar balun with record bandwidth ratio based on a single-layer printed circuit board has been presented by researchers in the US. The proposed balun could be implemented in many systems, including differential-fed antennas, balanced mixers, and push-pull amplifier circuits with broadband applications.
By inserting a polypropylene membrane between contact surfaces, wear in piezoelectric transformers has been reduced by researchers in China. As well as becoming much more durable, the transformers will have a higher power density, so using a dissipater with a piezoelectric transformer will be more practical.
Researchers from Korea and the US present a miniaturised fibre optic imaging probe that can extend its working distance without the need to insert a physical spacer between the cleaved fibre and the microlens to allow space for the light ray to expand. The structure allows for a smaller, less complex device package for endoscopic imaging applications, such as optical coherence tomography.
Tunnelling again and again
By considering an asymmetric space layer tunnel diode, researchers in the UK have achieved the required control over reproducibility for the first time - for any tunnel device – in the 50 years since the basic tunnel heterojunction structure was first investigated. This will impact on whole classes of electronic and optoelectronic devices.
Collaborating researchers in the US and Singapore have reported the first hybrid Si/III-V semiconductor laser operating at 1.9 µm. At this wavelength, due to their compactness, robustness, efficiency and low cost, such lasers find applications in molecular spectroscopy, gas sensing, laser surgery and fibre/free-space communication.