Multiplexed Millimeter Wave Communication with Dual Orbital Angular Momentum (OAM) Mode Antennas

Abstract

Communications using the orbital angular momentum (OAM) of radio waves have attracted much attention in recent years. In this paper, a novel millimeter-wave dual OAM mode antenna is cleverly designed, using which a 60 GHz wireless communication link with two separate OAM channels is experimentally demonstrated. The main body of the dual OAM antenna is a traveling-wave ring resonator using two feeding ports fed by a 90° hybrid coupler. A parabolic reflector is used to focus the beams. All the antenna components are fabricated by 3D printing technique and the electro-less copper plating surface treatment process. The performances of the antenna, such as S-parameters, near-fields, directivity, and isolation between the two OAM modes are measured. Experimental results show that this antenna can radiate two coaxially propagating OAM modes beams simultaneously. The multiplexing and de-multiplexing are easily realized in the antennas themselves. The two OAM mode channels have good isolation of more than 20 dB, thus ensuring the reliable transmission links at the same time.

Figure 1

The ring resonator. (a) The waveguide ring resonator with two feeding ports (EPA and EPB). The angle between two feeding ports is γ. The circular slot is in the narrow wall of the resonator. (b) The traveling-wave electric field distribution in the resonator and the radiation field from the slot.

Figure 2

The 90° hybrid coupler is designed as the feeding network. (a) The schematic of the 90° hybrid coupler with two input ports and two output ports. (b) The waveguide 90° hybrid coupler model to match the structure of the ring resonator shown in the Fig. 1a.

Figure 3

(a) The section view of the slot-loaded resonator and its radiation field. (b) The explosion view of the antenna. It is composed of four parts, including the ring resonator and metal plate, the phase-shift network (90° hybrid coupler), the ring focus parabolic reflector, and the flange connectors.

Figure 4

The fabricated dual OAM states antenna (l = ±3). (a) 3D printed (photosensitive polymer) antenna blank without metallization. (b) after the electro-less copper plating surface treatment process. The diameter of the ring focus parabolic reflector is ~50 mm.

Figure 5

The S-parameters of the antenna, S11 is the return loss and S21 represents the crosstalk between two ports of the dual OAM antenna. (a) The simulation results. (b) The measurement results.

Figure 6

The near-field radiation for OAM states of l = ±3. (a)~(d) are the measured results; (e)~(h) are the simulation results. (a), (c), (e) and (g) are the amplitudes of the radial component of the electric field, and (b), (d), (f) and (h) are the phase of the radial component of the electric field.

Figure 7

(a) The measurement result (blue dash line) and the simulation result (red solid line) for the far-field directivity diagram of the dual OAM antennas with the parabolic reflector diameter of 100 mm. The measured direction angle, gain and 3 dB angular width of the main lobe are ~6°, 20 dB, and ~4.5°, respectively. (b) The simulated 3D pattern for the antenna with reflector diameter of 200 mm.

Figure 8

The output signals from the l = +3 port of the receiving antenna measured by a spectrum analyzer. The blue solid line is the receiving signal intensity when the signal is launched into the l = +3 port of the transmitting antenna, and the red dash line is that when the signal launched into the l = –3 port. fc = 60 GHz, fs = 20 kHz.

Figure 9

The signals are monitored by a digital communication analyzer. The data A (blue solid line) are the signals when the modulated signal is launched into to the l = +3 port of the transmitting antenna, the data B (red dash line) are the signals A when the modulated signal is launched into the l = –3 port of the transmitting antenna.

Figure 10

(a) The experiment setup of the dual OAM communication link. The l = +3 channel carries the square wave modulated millimeter-wave signal, and the l = −3 channel carries the HD video signal. (b) The experimental photo to demonstrate the successful transmission of two independent channels. The picture on the screen is extracted from the video, Copyright The Admission Office of Zhejiang University.