Advances in Front-end Enabling Technologies for Thermal Infrared ‘THz Torch’ Wireless Communications

Abstract

The thermal (emitted) infrared frequency bands (typically 20-40 and 60-100 THz) are best known for remote sensing applications that include temperature measurement (e.g. non-contacting thermometers and thermography), night vision and surveillance (e.g. ubiquitous motion sensing and target acquisition). This unregulated part of the electromagnetic spectrum also offers commercial opportunities for the development of short-range secure communications. The 'THz Torch' concept, which fundamentally exploits engineered blackbody radiation by partitioning thermally generated spectral radiance into pre-defined frequency channels, was recently demonstrated by the authors. The thermal radiation within each channel can be independently pulse-modulated, transmitted and detected, to create a robust form of short-range secure communications within the thermal infrared. In this paper, recent progress in the front-end enabling technologies associated with the THz Torch concept is reported. Fundamental limitations of this technology are discussed; possible engineering solutions for further improving the performance of such thermal-based wireless links are proposed and verified either experimentally or through numerical simulations. By exploring a raft of enabling technologies, significant enhancements to both data rate and transmission range can be expected. With good engineering solutions, the THz Torch concept can exploit nineteenth century physics with twentieth century multiplexing schemes for low-cost twenty-first century ubiquitous applications in security and defence.

A Comprehensive Survey on Millimeter Wave Communications for Fifth-Generation Wireless Networks: Feasibility and Challenges

“…where d 1 = 20 m and d 2 = 39 m in both (11) and (12), and d 2D denotes the distance between the indoor building surface and the BS, d 2D is the 2D transmit-receiver Euclidean distance, with d 1 and d 2 as curve-fit parameters. While the mmMAGIC LOS probability model in an indoor hotspot environment gives…”

“…The short wavelengths, narrow beamwidth and high interaction with atmospheric constituents such as oxygen (O 2 ) and water vapor (H 2 O) characteristics of mmWave [1], [5], turns into both benefits and drawbacks. Some of the main benefits include: 1) The decrease in wavelength permits packing a large number of antenna elements into small form factors [2]; 2) Wide bandwidths centred around main carrier frequencies (35,94,140 and 220 GHz) [10] provide high data rates (up to 10 Gbps), ultra-low latency of around 1 ms [11], wideband spreadspectrum potential for reduced multipath, clutter, and high resistance to interference and jamming [10]; 3) relatively low atmospheric attenuation in the transmission windows over moderate path lengths, which potentially support the application of optical sources at specific wavelengths (i.e., 800 nm, 1550 nm and 10 µm) [10], [12]. Some of the mmWave drawbacks include: 1) Manufacturing the small mmWave components requires more precision and hence, increased costs [2], [13], [14]; 2) It encounters low sensitivity in the receiving system resulting from the reduced energy managed by the small antenna size [15].…”

Low-Cost Thermal-Infrared ‘THz-Torch’ Spectroscopy

“…Commercial TIR emitters have been used as the thermal source in our THz-T systems, for both wireless communications links [18]- [19] and spectroscopy applications [20]. The TIR emitter INTX 17-0900 has been found to be an efficient replacement for the original incandescent light bulbs [12]- [16]. Planck's law calculates the spectral radiance emitted from an ideal blackbody emitter 𝐼 𝐵𝐵 (𝑇 𝐵𝐵 ), as a function of absolute blackbody temperature 𝑇 𝐵𝐵 , which is assumed here to be the physical temperature T = 𝑇 𝐵𝐵 .…”

Thermodynamics-based Cognitive Demodulation for 'THz Torch' Wireless Communications Links

“…bps. With subsequent prototypes 12,[15][16][17] , the emitters generated a constant level of thermal radiation power (i.e., time-invariant) and employed mechanical optical choppers as an indirect modulation mechanism. This solution mitigates against thermal time constant constraints, offering the advantage of faster data rates.…”