Nanyang Research Programme Presentation EEE19: Beautiful Arrays Kwa - PowerPoint PPT Presentation

Nanyang Research Programme Presentation EEE19: Beautiful Arrays Kwa Shi Min Hwa Chong Institution (College Section)

INTRODUCTION AIMS METHODOLOGY RESULTS AND DISCUSSION CONCLUSION

INTRODUCTION Example: Satellite Communication Satellites using same frequency bands Target satellite Interference with another satellite! Antenna with low directivity Antenna with high directivity

INTRODUCTION Background: Antenna Array Directivity • Major uses in radar, sonar, wireless telecommunication, etc. • Radiate power in a specific direction • Single-element antenna usually limited in directivity • Antenna array synthesis 1. Array weight - costly in implementation 2. Array geometry • Current analytical, numerical and algorithmic approaches have yet to reveal a general theory for non-uniform arrays

INTRODUCTION Approach: Beautiful Antenna Array Geometry • Implement symmetry, golden ratio (GR) and silver ratio (SR) in the determination of inter-element spacings of non-uniform arrays o Led to many new theories when used in other fields o GR used implicitly before in phased arrays research – used solely as a special logarithmic spiral array o Not explicitly studied in the design of arrays in a general sense

AIMS Investigate effect of beautiful antenna array 1 geometry on antenna array directivity Increase antenna array directivity to higher than that 2 of control using beautiful antenna array geometry

METHODOLOGY 1 Geometry Design • Design schemes for testing • Adapt for linear and planar arrays • Design tests to investigate effects

METHODOLOGY Scheme 1: Scheme 2:

METHODOLOGY Scheme 3: Scheme 4:

METHODOLOGY Scheme 0: Linear Control Array

METHODOLOGY 1 Geometry Design • Design schemes for testing • Adapt for linear and planar arrays • Design tests to investigate effects

METHODOLOGY

METHODOLOGY Planar Control Array

METHODOLOGY 1 Geometry Design • Design schemes for testing • Adapt for linear and planar arrays • Design tests to investigate effects

METHODOLOGY 1 Geometry Design • Design schemes for testing • Adapt for linear and planar arrays • Design tests to investigate effects Control parameters 1. Array weights 2. Frequency 3. Wavelength Variable 1. Element position vectors

METHODOLOGY 2 Beampattern Generation • Real world antenna simulated by computer-programmed isotropic elements • Plot of array response to a plane-wave front • with unity amplitude arriving in direction (θ, φ) o A function of elevation angle (θ), azimuth angle (φ) & element position vectors (r) x 1 (t) w 1 Direction of Source z n x 2 (t) w 1 r n (x n , y n , z n ) y(t) Plane-Wave Front w 1 x L (t) θ y n y x(t) sampled signals at outputs of x n φ sensor elements w1 uniform weights x y(t) array output

METHODOLOGY 3 Performance Measurement • Observe and record Main Beamwidth, Mainlobe Gain and Peak Sidelobe Gain • Narrow Main Beamwidth Low Sidelobe Level (SLL) High Directivity 11-Element Symmetric GR Scheme 4 Root Value 0.587 Uniform Linear Array Main Beamwidth Gain (abs) Mainlobe Peak Sidelobe Azimuth Angle (⁰)

RESULTS AND DISCUSSION (LINEAR ARRAY) RESULTS AND DISCUSSION Preliminary Testing • Length increase, main beamwidth decrease o Coincides with general theory of uniformly-spaced linear arrays – for the same number of elements, the larger aperture will have a smaller beamwidth • Presence of undesirable spacings of (<0.5 or >1 wavelength), SLL increase o Dense regions reduce the elements contribution to the directivity since they are too close in terms of wavelength, while empty regions increase the under-sampling

RESULTS AND DISCUSSION (LINEAR ARRAY) Effect of Reflection Symmetry

RESULTS AND DISCUSSION (LINEAR ARRAY) Effect of Reflection Symmetry 0.00 SLL (dB) -10.00 Asymmetric Symmetric * -20.00 Scheme 1 Scheme 2 Scheme 3 Scheme 4 Scheme

RESULTS AND DISCUSSION (LINEAR ARRAY) RESULTS AND DISCUSSION Effect of Symmetry vs GR Schemes

RESULTS AND DISCUSSION (LINEAR ARRAY) RESULTS AND DISCUSSION Effect of Symmetry vs GR Schemes 0.00 Scheme 1 SLL (dB) Scheme 2 -10.00 Scheme 3 Scheme 4 Scheme> -20.00 Symmetry Scheme 3 Scheme 4 Scheme 1 Scheme

RESULTS AND DISCUSSION (LINEAR ARRAY) Effect of GR with Change in Root Value Let the distances between origin and X number of elements in a scheme be s 1 , s 2 , …, s x . E.g. When the scheme is subjected to a root value of 0.1 , s 2 0.1 , …, s x 0.1 . 0.1, the distances will become s 1 • To obtain optimized power and best scheme • Reduce side lobe amplitudes and grating lobes

RESULTS AND DISCUSSION (LINEAR ARRAY) RESULTS AND DISCUSSION Effect of GR with Change in Root Value 0.00 Larger root values forces inter- element spacings to become more similar→oscillation Scheme 0 Consider SLL (dB) Scheme 1 -5.00 main Scheme 2 Further beamwidth test Scheme 3 when SLLs portions are similar Scheme 4 to 3s.f. -10.00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Root Value

RESULTS AND DISCUSSION (LINEAR ARRAY) RESULTS AND DISCUSSION Effect of GR with Change in Root Value 200.00 Main Beamwidth (°) Scheme 0 Scheme 1 100.00 Scheme 2 Scheme 3 Scheme 4 0.00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 .0 Root Value

RESULTS AND DISCUSSION (LINEAR ARRAY) Effect of GR with Change in Number of Elements 9 11

RESULTS AND DISCUSSION (LINEAR ARRAY) RESULTS AND DISCUSSION Effect of GR with Change in Number of Elements -8.00 SLL (dB) -13.00 Scheme 0 gradual Scheme 4 -18.00 3 5 7 9 11 13 15 17 19 +2 Number of Elements

RESULTS AND DISCUSSION (LINEAR ARRAY) RESULTS AND DISCUSSION Beampatterns of Finalised Symmetric GR Scheme vs Control 11-Element Symmetric GR Scheme 4 Root Value 0.587 Uniform Linear Array Main Beamwidth Mainlobe Gain (abs) Peak Sidelobe Main Beamwidth ↓21% SLL ↓28 % Azimuth Angle (⁰)

RESULTS AND DISCUSSION (PLANAR ARRAY) RESULTS AND DISCUSSION Effect of Order of Rotational Symmetry Order 4 Order 8

RESULTS AND DISCUSSION (PLANAR ARRAY) RESULTS AND DISCUSSION Effect of Order of Rotational Symmetry 0.00 * SLL (dB) -15.00 Order 4 Order 8 -30.00 Scheme 0Scheme 2Scheme 3Scheme 4 Scheme

RESULTS AND DISCUSSION (PLANAR ARRAY) RESULTS AND DISCUSSION Effect of SR with Change in Number of Elements 0.00 but stagnates Scheme 0 SLL (dB) -15.00 Scheme 2 Scheme 3 Scheme 4 -30.00 20 30 40 50 60 70 80 90 100 Number of Elements

RESULTS AND DISCUSSION (PLANAR ARRAY) Effect of SR with Change in Scaling Value Let the distances between origin and X number of elements in a scheme be s 1 , s 2 , …, s x . Eg. When the scheme is subjected to a scaling value of 1.1, the distances will become 1.1 * s 1 , 1.1 * s 2 , …, 1.1 * s x . • Optimize SLL and beamwidth

RESULTS AND DISCUSSION (PLANAR ARRAY) RESULTS AND DISCUSSION Effect of SR with Change in Scaling Value 120.00 Main Beamwidth (°) Control array has main beamwidth of 40.00⁰, therefore further tested to 2d.p. →1.25, 38.00⁰ 60.00 Scaling V alue (≥1)↑, 0.00 Main Beamwidth ↓ 1.0 1.1 1.2 1.3 1.4 1.5 Scaling Value

RESULTS AND DISCUSSION (PLANAR ARRAY) Effect of SR with Change in Scaling Value 0.00 SLL (dB) 1.25, -23.41dB -15.00 Scaling V alue (≥1)↑, SLL↓ -30.00 1.0 1.1 1.2 1.3 1.4 1.5 Scaling Value

RESULTS AND DISCUSSION (PLANAR ARRAY) RESULTS AND DISCUSSION Cartesian Beampattern of Finalised Symmetric SR Scheme Gain (dB)

RESULTS AND DISCUSSION (PLANAR ARRAY) Polar Beampattern of Finalised Symmetric SR Scheme Main Beamwidth ↓5.0% SLL ↓18% Gain (dB) Elevation Angle (⁰)

CONCLUSION Novel empirical study on the effects of using symmetry, GR and SR in the design of non-uniform antenna arrays on the directivity of beampatterns Symmetry, GR and SR can be used to increase antenna array directivity 1 Significant increase of antenna array directivity in comparison with control 2 Beautiful Antenna Array Geometry: Potential Way of Increasing Antenna Array Directivity

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