These sinuous antennas are used in electronic countermeasures, radio astronomy, and remote sensing. Figure 1 shows the discretization pattern of one of these antennas.

Figure 1: Sinous antenna

The design on Figure 1 was analyzed using the method of moments to predict its performance.The SWR of the input impedance is plotted below in Figure 2 referenced to both 50 and 140 Ohms, the mean input impedance of the antenna.

Figure 2: SWR of the input impedance referenced to both 50 and 140 Ohms

Figures 3 and 4 show the half-power beamwidths (HPBW) for the sinuous antenna excited in the left-hand sense. Figure 3 is a cut in the phi = 0deg plane, and Figure 4 is a cut in the phi = 45deg plane.

Figure 3: HPBW in the phi = 0deg plane (left-hand excitation)

Figure 4: HPBW in the phi = 45deg plane (left-hand excitation)

Figures 5 and 6 show the same HPBW data for right-hand excitation.

Figure 5: HPBW in the phi = 0deg plane (right-hand excitation)

Figure 6: HPBW in the phi = 45deg plane (right-hand excitation)

Finally, Figures 7 and 8 show the surface current directed tangentially along an arm centerline at 4 GHz. The magnitude and phase are plotted for left- (Figure 7) and right-hand (Figure 8) excitation. The graph abscissa denotes arc length along the arm.

Figure 7: Tangential surface current magnitude and phase (left-hand excitation)

Figure 8: Tangential surface current magnitude and phase (right-hand excitation)

The above work is a collaboration between Jim Bowen, Prof. Paul Mayes, and Prof. Weng Cho Chew. Please send suggestions, comments, and inquiries to: jbowen@.uiuc.edu.