All-dielectric photoconductive metasurfaces for terahertz applications

We review applications of all-dielectric metasurfaces for one of the cornerstone technologies in THz research – ultrafast photoconductive (PC) switches – which are widely used as sources and detectors of broadband THz pulses. Nanostructuring the PC switch channel as a perfectly-absorbing and optically thin PC metasurface allows us to engineer the optical as well as the electronic properties of the channel and improve the efficiency of THz detectors. This approach also opens new routes for employing novel PC materials and enabling new device architectures including THz detector arrays.

24 GHz low-power switch-channel CMOS transceiver for wireless localization

A 24 GHz low-power transceiver is designed, fabricated, and characterized using 130 nm complementary metal-oxide semiconductor (CMOS) process. The designed transceiver is targeted for frequency-modulated-continuous-wave (FMCW) wireless local positioning. The transceiver includes four switchable receiving channels, one transmitting channel and local-oscillator generation circuitries. Several power-saving techniques are implemented, such as switch channel and adaptive mixer biasing. The design aspects of the low-power circuit blocks and integration considerations are presented in details. The integrated transceiver has a chip area of only 2.2 mm × 1.7 mm. In transmitting mode the transceiver achieves an output power of 4 dBm and phase noise of −90 dBc/Hz at 1 MHz, while consuming 75 mW power consumption under 1.5 V power supply. In switch-channel receiving mode the transceiver demonstrates 31 dB gain and 6 dB noise figure with 65 mW power consumption. The transceiver measurements compare well with the simulated results and achieve state-of-the-art performance with very low-power consumption.

Improvement on a Multi-Channel Broadcast Encryption Scheme

Broadcast encryption provides a convenient method to distribute digital content to subscribers over an insecure broadcast channel so that only the qualified users can recover the data. In some broadcast encryption based systems such as pay-TV, multiple ciphertext headers (via multiple channels) are needed since the sender needs to send various contents to different groups of subscribers. Each receiver needs to store all headers in order to switch channel fluently. Recently, Phan et al. described a multi-channel broadcast encryption scheme, in which the sender encapsulates multiple ephemeral keys into one ciphertext header so that each receiver only stores one ciphertext header and still can recover various ephemeral keys for different contents. We present an improvement on their scheme, which will reduce the size of public key and the computation cost for decryption. The improved scheme can be used to construct efficient dynamically privileged broadcast encryption system.