Nonlinear Effects in Active Phased Array System Performance

Transcription

1 Nonlinear Effects in Active Phased Array System Performance Larry Williams, PhD Director of Product Management ANSYS Inc. 1

2 Advanced Simulation Simulate the Complete Product Real-life behavior in real-world environments Comprehensive multiphysics Complete system modeling Concept & Design Simulation-Driven Product Development Physical Prototype Production Simulation-Driven Product Development Minimizes TOTAL time through the loop Maximizes validated learning 2

3 Simulation Driven Product Development Integrating BFN with Antenna Elements for a Radar System 3D Antenna Array Design 3D Beam Forming Network (BFN) Design Radar System Platform performance Simulation-Driven Product Development BFN Digital Phase Shifter/Attenuators Power Splitter Antenna Array ANSYS, Inc. April 24, 2015 ANSYS, Inc. Proprietary 2009 ANSYS, Inc. All rights reserved. 1-3 Platform Performance February 23, 2009 Inventory #002593

4 HFSS Advanced Simulation Technology Finite Element Method Efficiently handles complex material and geometries FEM Transient Ideal for fields that change versus space and time; scattering locations Local time stepping Circuit Solver Dynamic Link to Field Solvers Integral Equations (IE) Efficient solution technique for open radiating and scattering of metallic objects ACA and MLFMM Physical Optics(PO) Ideal for electrically large, conducting and smooth objects 4

5 Multi-Scale Multi-Domain System MIMIC in HFSS 3D Layout 3D EM Simulation of Circulator Domains: Circuit, Frequency, Time, FEM, IE, PO etc Antenna Element/Array 5 3D EM Simulation of Amp Package Scale: Circuit level, component level, antenna and array level, small component on large aircraft

6 R16 Electronics Desktop HFSS-IE HFSS HFSS Layout Circuit 6

7 Active Phased Array on Aircraft 7

8 Integrated Radar System Northrop Grumman RQ-4 Global Hawk Radar - Operational Modes Side-looking Synthetic Aperture Radar 8

9 Goal Integrated Antenna Performance Understand antenna system performance in actual operational environment Solved! 55 minutes, 32 cores, 75GB RAM UAV solved with HFSS-IE Data-link: antenna array is a near field source in HFSS-IE design 9

10 16 x 64 Element Phased Array in HFSS Solved! 3 hours, 16 cores, 75GB RAM 10

11 Concept: Antenna Requirements Reconfigurable: Electronically Steerable Phased Array Phased Array A group of antenna elements in which the relative amplitudes and phases are varied to construct an effective radiation pattern by constructive and destructive interference Amplitude Phase 11

12 Concept: Shaped Beam Wide Area Cosecant-Squared Beam Spot Area - Taylor Weighting Requires 16 antenna elements 12

13 Concept: Controlling Amplitude and Phase Transmit/Receive (T/R) Module Block Diagram Antenna Element Power Distribution Beam Forming Network (BFN) Transmit Circulator (Amplitude/Phase) Power Amplifier Receive Replicate <n> Times Component Requirements Phase 5-bit Phase Shifter Amplitude 15 db dynamic range 5-bit Digital Attenuator 13

14 Design Approach: Integrated System Antenna + T/R Antenna Element Circulator Amp BFN Power Distribution 14

15 Radar Tx System Beam Forming Network Radar Tx Performance Power Distribution Antenna Array 15

16 HFSS 3D Layout 16

17 Feed Network Design Verification Design Optimization Offset Radius HFSS 3D Components HFSS Circuit Optimization 17

18 Multiscale: 3D With Embedded Circuits 3D Physical Device Model Ideal Electrical Model Digital Phase Shifter/Attenuators 18 Transistor Based or X-Parameter Power Amplifier

19 Quantization Effect on Boresite Pattern Quantized Phase/Atten Ideal Phase/Atten Quantization of the element weights makes little difference in the beamwidth or sidelobe levels 19

20 Quantization Effect on Steered Pattern Quantized Phase/Atten Ideal Phase/Atten The difference is not noticeable near the main lobe Parasitic lobe near 0 degrees is the result of phase rounding quantization, and can be eliminated with a variety of methods [1] 20 [1] M.S. Smith and Y.C. Guo, A Comparison of Methods for Randomizing Phase Quantization Errors in Phased Arrays, IEEE Trans. On Ant. & Prop., v. AP-31, no. 6, Nov 1983

21 Nonlinear Effects on Shaped Beam 21

22 db10normalize(gainl3y) Z X Ansoft Corporation 0.00 XY Plot 4 16x1_o dB -30dB -20dB Theta [deg] 22 R.S. Elliott and George J. Stern, A New Technique for Shaped Beam Synthesis of Equispaced Arrays, IEEE Trans. Antennas Propagat., vol. AP- 32, No. 10, Oct

23 15dB Dynamic Range Amplitude (db) Amplitude / Phase Distribution Element Number (m) Excitation Voltage (V m ) Element Number (m) Excitation Voltage (V m ) Element Number

24 dbm(p(port2)<f1>) db(tg(port2,port1)<f1,f1>) L21 1e-006 L22 1e-006 BJT Power Amplifier is Nonlinear V24 Port1 I23 0 U3 Nexxim4 0 Nexxim2 U1 Port1 Port2 C20 Q17 C19 Port1 Port2 1e-009 Port2 1e-009 bjt33 0 Ansoft Corporation gain, pout, phase Nexxim Pout Gain Curve Info dbm(p(port2)<f1>) HB1Tone db(tg(port2,port1)<f1,f1>) HB1Tone pin [dbm]

25 Y1 Gain Compression Ansoft Corporation 6.00 Gain Compression XY Plot 3 PowerSweep ~15dB P1 [dbm] Linear +10dBm +14dBm 25

26 Y1 Linear (blue) vs. +10dBm Ansoft Corporation XY Plot 2 Blue: 0dBm (linear) Red: +10dBm 16x Theta [deg] 26

27 Y1 Linear (blue) vs. +14dBm Ansoft Corporation 0.00 XY Plot 2 16x Blue: 0dBm (linear) Red: +14dBm Theta [deg] 27

28 Infinite and Finite Planar Array 28

29 Array Description 16 x64 Element Array 1024 Y-Polarized Quasi-Yagi Elements 15mm x 15mm Square Lattice 50 o Conical Scan Volume Frequency Band from 9GHz to 11GHz 29

30 Array Analysis Methods Infinite Array Finite Array Domain Decomposition Unit Cell with Periodic Boundaries Unit Cell Provides Embedded Element Pattern Includes mutual coupling effects Predicts Blind Zones and Surface Waves Assumes an infinite array No edge effects Uniformly Excited Small volume; fast simulation Solver decomposes array into domains of similar element type for more efficient solve times Corner elements Edge elements Center elements Leverages many computers to solve large but finite array Mesh copied from unit cell 30

31 Infinite Array Mirror Quasi-Yagi antenna element Mirror 31 Image courtesy

32 Infinite Array Unit Cell Periodic boundary conditions Slave has same fields as Master but for a phase shift Simulates any scan condition. The radiated fields are terminated through a Floquet Port The scan volume can be evaluated by parametrically sweeping the scan angle (qs,fs) Slave Floquet Port Master ANSYS, Inc.

33 Effects on the Pattern z x y Element Pattern Gain calculated directly from Floquet Transmission Coefficients E-Plane Scan Blindness G 2 TM TE cos( q ) 4 A 2 2 0,0 0,0 s 33

34 Floquet Transmission Coefficients Indicate a Possible Surface Wave Transmisssion Grating Lobe Possible Surface Wave 34

35 Surface Wave Verification The fields at the problem frequency and scan angle indicate a surface wave is the cause. The surface wave was found because Floquet Ports were used More frequencies could be evaluated The interpolation in the interpolating sweep help reveal the surface wave 35

36 Finite Array Domain Decomposition Method (DDM) 16x64 Array Mesh copied from unit cell design to every element in finite array design - Reinforces periodicity of array - Dramatically reduces mesh time associated with finite array analysis Solver decomposes array into domains and solves those domains in parallel Full array solved with composite excitation for significant gains in simulation speed 36 Unit Cell Import mesh Time (16 cores) RAM Unit Cell 15mins 7GB Finite Array 3hrs 75GB

37 Finite Array Domain Decomposition Method (DDM) 37

38 Finite Array vs Infinite Array Factor Blue: Infinite Array Factor Red: Finite Array 38

39 Platform Integration 39

40 Array on UAV UAV solved with HFSS-IE Data-link: antenna array is a near field source in HFSS-IE design Time (32 cores) RAM 40 55mins 75GB

41 Array Performance on Aircraft Blue: Array on Aircraft Red: Finite Array 41

42 Multiphysics 42

43 Physics-Based Simulation Electromagnetics Electronics RF/Antenna and SI/PI/EMI Antenna Array Antenna Placement Large Scale Platform Interaction Co-Site Rotor Blade Modulation Lightening Strike 43

44 Physics-Based Simulation Structural Mechanics Coupled Solution Electro-Mechanical Design Stress/ Explicit Dynamics Rivet Fatigue Vibration 44 Composites Failure

45 Physics-Based Simulation Engine Combustion Fluid Dynamics Engine Cooling Landing Deck Air Flow Rotor Design and Aero acoustics Aerodynamics 45 Landing Gear Turbulent Flow

46 Summary Modern simulation allows real-world system analysis Electromagnetics Mechanical Fluid Dynamics Multi-scale analysis of phased array Quantization effects Nonlinear circuit effects Planar array simulation Infinite array using periodic boundaries used to find blind zones and surface waves Finite array reveals pattern degradation due to array edges Platform Integration Brings all techniques together for full installed performance 46

47 Thank You 47