Systems Analysis for Thermal Infrared ‘THz Torch’ Applications

Abstract

The 'THz Torch' concept was recently introduced by the authors for providing secure wireless communications over short distances within the thermal infrared (10-100 THz). Unlike conventional systems, thermal infrared can exploit front-end thermodynamics with engineered blackbody radiation. For the first time, a detailed power link budget analysis is given for this new form of wireless link. The mathematical modeling of a short end-to-end link is provided, which integrates thermodynamics into conventional signal and noise power analysis. As expected from the Friis formula for noise, it is found that the noise contribution from the pyroelectric detector dominates intrinsic noise. From output signal and noise voltage measurements, experimental values for signal-to-noise ratio (SNR) are obtained and compared with calculated predictions. As with conventional communications systems, it is shown for the first time that the measured SNR and measured bit error rate found with this thermodynamics-based system resembles classical empirical models. Our system analysis can serve as an invaluable tool for the development of thermal infrared systems, accurately characterizing each individual channel and, thus, enables the performance of multi-channel 'THz Torch' systems to be optimized.

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

“…Unlike laser sources, which have very narrow beamwidths, radiation from open thermal sources is isotropic. From the Friis equation, in the far field, received power density is inversely proportional to the square of the transmission range [13]. With the previously demonstrated multiplexing systems setup [11], having a range set to 3 cm and bias current of 80 mA (giving a source temperature of 772 K, or total output power of 97.5 mW), the measured bit error rate (BER) was ∼10 −3 .…”

“…Both single-and multi-channel wireless links have been reported; the resilience to interception and jamming with 2.56 kbps frequency division multiplexing (FDM) and 0.64 kbps frequency-hopping spread-spectrum (FHSS) systems has been demonstrated experimentally [11]. Furthermore, the radiation mechanisms for the basic thermal source transducers [12], as well as the power link budget analysis for the system were previously reported [13]. In this paper, we discuss recent advancements in the front-end enabling technologies associated with the THz Torch concept for wireless communications, which go beyond what has already been published.…”

“…This offers opportunities for developing such systems within this largely unregulated part of the electromagnetic spectrum. The 'THz Torch' concept was recently introduced by the authors for providing secure wireless communications over short distances within the thermal infrared [8][9][10][11][12][13]. Both single-and multi-channel wireless links have been reported; the resilience to interception and jamming with 2.56 kbps frequency division multiplexing (FDM) and 0.64 kbps frequency-hopping spread-spectrum (FHSS) systems has been demonstrated experimentally [11].…”

Modelling Miniature Incandescent Light Bulbs for Thermal Infrared ‘THz Torch’ Applications

“…The spectral range for the first proof-ofconcept single-channel 'THz Torch' system was defined over the 25 to 50 THz (12 μm to 6 μm) octave bandwidth [1,3,4], while four non-overlapping spectral ranges for the 4-channel multiplexing systems are: 15 to 34 THz (20 μm to 8.8 μm) for Channel A; 42 to 57 THz (7.1 μm to 5.3 μm) for Channel B; 60 to 72 THz (5 μm to 4.2 μm) for Channel C; and 75 to 89 THz (4 μm to 3.4 μm) for Channel D [2,[4][5][6]. Fig.…”

“…For the simple proof-of-concept demonstrator, the 'THz Torch' transmitter consists of five Eiko 8666-40984 miniature incandescent light bulbs, having a length of 6.3 mm and diameter 2.6 mm [1][2][3][4][5][6]. These bulbs are connected in series and assembled into a compact cylindrical package having an outer diameter of 8.2 mm, as shown in Fig.…”