Generation of High-Purity Millimeter-Wave Orbital Angular Momentum Modes Using Horn Antenna: Theory and Implementation

Twisted electromagnetic waves, of which the helical phase front is called orbital angular momentum (OAM), have been recently explored for quantum information, high speed communication and radar detections. In this context, generation of high purity waves carrying OAM is of great significance and challenge from low frequency band to optical area. Here, a novel strategy of mode combination method is proposed to generate twisted waves with arbitrary order of OAM index. The higher order mode of a circular horn antenna is used to generate the twisted waves with quite high purity. The proposed strategy is verified with theoretical analysis, numerical simulation and experiments. A circular horn antenna operating at millimeter wave band is designed, fabricated, and measured. Two twisted waves with OAM index of l=+1 and l=-1 with a mode purity as high as 87% are obtained. Compared with the other OAM antennas, the antenna proposed here owns a high antenna gain (over 12 dBi) and wide operating bandwidth (over 15%). The high mode purity, high antenna gain and wide operating band make the antenna suitable for the twisted-wave applications, not only in the microwave and millimeter wave band, but also in the terahertz band.Comment: 18 pages, 9 figure

Angle_data

Angle of Joints (ankle, knee and hip) dat

Breath_data

Breath (the distance between the abdominal markers) dat

Mean values and standard errors of COP measurements in the quiet standing (QSt) and standing with mental arithmetic (MASt) conditions.

<p>Mean values and standard errors of COP measurements in the quiet standing (QSt) and standing with mental arithmetic (MASt) conditions.</p

Mean values and standard errors of breathing measurements in the quiet standing (QSt) and standing with mental arithmetic (MASt) conditions.

<p>Mean values and standard errors of breathing measurements in the quiet standing (QSt) and standing with mental arithmetic (MASt) conditions.</p

Experimental setup.

<p>(A) Marker placement: Eight reflective markers were placed over surface landmarks. The markers, except for L4 and the navel, were used to calculate the ankle, knee, and hip joint angles in the sagittal plane. The markers of L4 and the navel were used to calculate the abdominal breathing movement. (B) Definitions of joint angles: Joint angles were expressed as positive in the clockwise direction.</p

Exp2_Angle_Torque_EMG_Data

Footplate angle, footplate torque and EMG dat

Exp1_Angle_Torque_EMG_Data

Footplate angle, foolplate torque and EMG dat

Exp1_Kinematics_Data

Joint angles of lower limb for 7 subjects in Experiment

A typical example of the stretch reflex responses divided into the early and late responses.

<p>(A) In the TA responses to toes-down rotations. (B) In the SOL responses to toes-up rotations. The dashed horizontal line shows the threshold (BGA + 3SD) of each SR response. The black bar indicates the calculated period for BGA. The arrow indicates the onset of perturbation.</p