Compact Integrated Full-Duplex Gap Waveguide-Based Radio Front End For Multi-Gbit/s Point-to-Point Backhaul Links at E-Band

Abstract

This paper presents the design and realization of a high data rate radio front-end module for point-to-point backhaul links at E-band. The design module consists of four vertically stacked unconnected metal layers without any galvanic and electrical contact requirements among the building blocks, by using gap waveguide technology. The module components are a high gain array antenna, diplexer, and circuitry consisting of a transmitter (Tx) and a receiver (Rx) monolithic microwave integrated circuits (MMICs) on a carrier board, which are successfully integrated in one package with a novel architecture and a compact form. The diplexer consists of two direct-coupled cavity bandpass filters with channels at 71-76 GHz and 81-86 GHz with a measured return loss of 15 dB and an isolation greater than 50 dB. A wideband 16×16 slot array antenna with a measured gain of more than 31 dBi is used to provide high directivity. The measured results show that the packaged transmitter provides a conversion gain of 22 dB and 20 dB at 76 GHz and 86 GHz, respectively, with an output power of 14 dBm and 16 dBm at 1-dB gain compression point, at the same frequencies. The packaged receiver shows an average conversion gain of 20 dB at 71-76 GHz and 24 dB at 81-86 GHz bands. A real-time wireless data transmission is successfully demonstrated with a data rate of 8 Gbit/s using 32 quadrature amplitude modulated signal over 1.8 GHz channel bandwidth with spectral efficiency of 4.44 bit/s/Hz. The proposed radio front-end provides the advantages of low loss, high efficiency, compact integration, and a simple mechanical assembly, which makes it a suitable solution for small cell backhaul links.

Adaptive Digital Self-Interference Cancellation for Millimeter-Wave Full-Duplex Backhaul Systems

“…where G q Ant is the antenna gain, A q FS is the free space transmission loss as given by ( 5) (where d q in meter is the distance between the transceiver and obstacle, and f c in GHz is the carrier frequency) [36], A q Rain is the rain attenuation, A q Atm is the atmospheric attenuation (4.0 × 10 −4 dB/m [37]), and A Refl is the reflection loss, which depends on the refractive index of the obstacle and is set to 20 dB typically [38]. Note that the FEXT path length is twice of the distance between the transceiver and obstacle, which should be considered in calculating For the rain attenuation, we typically consider rain zone K with availability of 99.99%, and the corresponding maximum attenuation is 1.65 × 10 −2 dB/m [39], [40].…”

Dual-Band Single-Layer Slot Array Antenna Fed by K/Ka-Band Dual-Mode Resonators in Gap Waveguide Technology

“…There exist few examples of diplexers hosted in single-layer full-metal antennas in the millimeter-wave band. For example, diplexers using gap waveguide technology are presented in [12] and [13]. There, the working bands are much closer together and the diplexers are integrated in dedicated layers in multilevel antennas.…”

Dry Film Photoresist-Based Microfabrication: A New Method to Fabricate Millimeter-Wave Waveguide Components

“…A simple ridge gap waveguide structure is shown in Figure 1 . Recently, many gap waveguide passive components have been demonstrated and realized using the conventional manufacturing method [ 32 , 33 , 34 ] as well as by using micromachining techniques [ 19 , 35 , 36 ].…”