Mobile THz communications using photonic assisted beam steering leaky-wave antennas

Abstract

THz communications is envisaged for wide bandwidth mobile communications eventually reaching data capacities exceeding 100 Gbit/s. The technology enabling compact chip-integrated transceivers with highly directive, steerable antennas is the key challenge at THz frequencies to overcome the very high free-space path losses and to support user mobility. In this article, we report on mobile and multi-user THz communications using a photonic THz transmitter chip featuring 1D beam steering for the first time. In the proposed approach, 1D THz beam steering is achieved by using a photodiode excited leaky-wave antenna (LWA) in the transmitter chip. The on-chip LWA allows to steer the directive THz beam from 6° to 39° within the upper WR3-band (0.28-0.33 THz). The antenna’s directivity is 14 dBi which is further increased to 23 dBi using an additional hemicylindrical Teflon lens. The 3-dB beam width and coherence bandwidth of the fabricated THz transmitter chips with lens are 9° and 12 GHz, respectively. The proposed approach allows steering the THz beam via the beat frequency of an optical heterodyne system at a speed up to 28°/s. Without using a THz amplifier in the transmitter chip, a data rate of 24 Gbit/s is achieved for a single user for all beam directions and at short wireless distances up to 6 cm. The wireless distance is successfully increased to 32 cm for a lower data rate of 4 Gbit/s, still without using a transmitter amplifier. Also, multi-user THz communications and the overall capacity of the developed THz transmitter chip is studied revealing that up to 12 users could be supported together with a total wireless data capacity of 48 Gbit/s. Fully integrated 2D transmitter chips are expected to reach wireless distances of several meters without additional amplifiers.

Review of graphene for the generation, manipulation, and detection of electromagnetic fields from microwave to terahertz

“…LWAs are highly suitable for CMOS integration [171]. Most non-graphene implementations focus on the microwave frequency range [171][172][173][174], with fewer implementations exploring the THz range [171,[174][175][176]. The main focus has been in the development of highly efficient, high directivity, and wide scan angle implementations for communication applications.…”

“…The main focus has been in the development of highly efficient, high directivity, and wide scan angle implementations for communication applications. As such, much interest has been in the reconfiguration of their polarization [173], beam scanning [172], and multiplexing [175,176]. RF switches, such as diodes [171] or MEMS [177], are commonly used to achieve reconfigurability.…”

THz Systems Exploiting Photonics and Communications Technologies

“…In [147], 100 Gbit/s wireless THz transmission is demonstrated at 300 GHz using an analog bandwidth of only 12.5 GHz. By using a photodiode excited planar InP-based on-chip THz LWA, mobile THz communications is demonstrated for the first time in [148]. For single user operation, a minimum data rate of 24 Gbit/s is achieved within the antenna's scanning range of 33°.…”

Initial Access & Beam Alignment for mmWave and Terahertz Communications

“…Another example introduced tilt into the pump beam of a photoconductive antenna to achieve an outgoing phase gradient [123], but this requires a highly advanced physical laser set-up that is not viable for network VOLUME 10, 2022 deployment. Leaky-wave antennas have been deployed for demonstrations of terahertz communications [124], but their frequency-scanning nature imposes stringent restrictions on achievable data rates and achievable beam patterns.…”