Transmitarrays, reflectarrays and phase shifters for wireless communication systems Pablo Padilla de la Torre Universidad de Granada
Outline 1. Introduction to Transmitarray and Reflectarray structures 2. Passive Transmitarrays 3. Passive Reflectarrays 4. Reconfigurability: Phase shifters 5. Reconfigurable devices: Example 2
1. Introduction to Transmitarray and Reflectarray structures 3
Txarray and Rxarray structures Transmitarrays Equivalent to artificial lenses Reflectarrays Equivalent to reflector-based antennas Reception and pattern rearrangement. Planar Architecture. Fundamental Aim: Configure a new radiation pattern (passive devices). Reconfigure the radiation pattern (active devices). Different receivers for different signals, depending on DoA Directions of arrival Lens Receiver 1 Receiver k 4
Transmitarray structures Transmitarray concept: 1. Phase error correction 2. Radiation pattern modification 5
Reflectarray structures Reflectarray concept: 1. Phase error correction 2. Radiation pattern modification 6
Reflectarray structures Reflectarray Configuration: Without phase correction: Array distribution: With phase correction: 7
2. Passive Transmitarrays 8
Passive Transmitarrays Transmitarray configuration: Particular Specifications: Working frequency: 12 GHz. Band width: >0.7 GHz Linear polarization. Geometry Applied: Design 1: Multilayer Planar Geometry Two different geometries analyzed and applied: Design 2: Planar Geometry with plane change 9
Passive Transmitarray: Design 1 Transmitarray design: Particular Specifications: 5x5 element array. Array separation between elements: 0.8λ 0. Radiation pattern reconfiguration: 10º tilt in one of the main axes. Transmitarray Cell Design: Transmitarray configuration: Design of one half of Transmitarray cell: Radiating element. Stripline. Coaxial to stripline transmission line. 10
db db Passive Transmitarray: Design 1 Design and Prototypes for Subsystems: Half transmitarray cell prototype: Phase delay line: Coaxial to stripline transmission. Stripline. For measurements in the center of cell TRL calibration Kit Prototype: Measurement results: 0-10 -20-30 0-10 -20-30 -40 9 10 11 12 13 Frequency (GHz) -40 9 10 11 12 13 Frequency (GHz) 11
Passive Transmitarray: Design 1 Design and Prototypes for Subsystems: Delay line integration Patch array integration Transmission lines Vias Coaxial to stripline transmission. Stripline. Line detail Complete soldered structure Patch array Feeding Horn and hanging elements Complete Prototype 12
Passive Transmitarray: Design 1 Prototype Measurement Phase error correction and 10º tilt in one axis. Theoretical and measured radiation pattern Measuring scheme Copolar Measured Gain: 15.4 dbi. Spherical acquisition chamber Near field to far field conversion Reduction due to spillover (accepted horn power 42%=-3.7 db) and circuit losses (1.9dB). 13
Passive Transmitarray: Design 2 Transmitarray design: Particular Specifications: 10x10 element array. Stacked patches. Array separation between elements: 0.6λ 0. Radiation pattern reconfiguration: 10º tilt in one of the main axes. Transmitarray cell design: Upper Patch ε r =2.17, h=1.575 mm ε r =1.07, h=2 mm Lower Patch ε r =2.17, h=1.575 mm Ground Plane Design of one half of Transmitarray cell: Stacked patch Radiating element. Coaxial to microstrip transmission line. 90º change in reference plane. Microstrip lines 14
Passive Transmitarray: Design 2 Prototypes of Subsystems : Patch prototypes: Single patch measurement results: 0 90º Transition: 0-10 -20-30 8 10 12 14 16-10 -20-30 Half transmitarray cell measurement: Patch + 90º transition+ transmission line: -40 Patch embedded in array: -50 10 11 12 13 14-10 -20 S 11, db -30 S 11, db -40-50 8 10 12 14 16 Frequency (GHz) Frequency (GHz) 15
Upper Lower Layer Passive Transmitarray: Design 2 Transmitarray assembly: Patch layers Delay line layers Complete passive transmitarray for the second design Complete Prototype Lines soldering detail Two radiating interfaces. 10x10 array. 100 soldered transmission lines 200 metallic vias. 50x50cm ground plane. 800 soldering points. 16
Passive Transmitarray: Design 2 Prototype Measurement: For Design 2: Phase error correction and 10º tilt in one main axis 0 Theoretical radiation pattern Measured Radiation pattern -5-10 -15 db -20-25 -30-35 -40-90 -80-70 -60-50 -40-30 -20-10 0 10 20 30 40 50 60 70 80 90 Theta (deg) 3D measured radiation pattern 2D measured radiation pattern Spherical acquisition chamber Near field to far field conversion Measured Gain: 22.5 dbi. Reduction due to spillover (accepted horn power 75%=-1.25 db) and transmission line losses (1.05 db) 17
3. Passive Reflectarrays 18
Array distribution: Passive Reflectarray Circularly polarized Reflectarray: geometry: Rx LHCP/RHCP Tx LHCP/RHCP Shifting circuit layer Ground plane Lower patch layer Upper patch layer x y Reflectarray specifications: Parameter Value Units Frequency bands 11.5-12.5 GHz Polarization LHCP/RHCP - Axial ratio < 2.5 db 3dB beamwidth 7 º Side lobe level < -16 db Cross polarization < -25 db Gain > 25.5 dbi Directivity 27 dbi Radiation efficiency > 65 % VSWR 1.4:1 (-15.6dB) - Size (planar structure) 240x240x3.524 mm Array separation 0.55λ mm Focal distance 210 mm Reflectarray Configuration: z 13x13 cell array. Multilayered square patches. Cell separation: 0.55λ 0. Re-alignement of the radiation pattern towards the broadside direction. ~70% of available power coming from the feeder (spillover efficiency). 19
Passive Reflectarray Subsystem prototypes: multilayered patches and phase shifters Isolated cell: Embedded patch in array: Phase shifters: 20
Upper layer lower layer Passive Reflectarray Prototyping: Reflectarray assembly Phase shifting layer: Patch layers: Complete assembled prototype: 21
Prototype Measurements: Radiation Patterns (at 12GHz): φ=90º (y axis) φ=0º (x axis) Passive Reflectarray [db] 0-10 -20 measured CP simulated CP measured XP -30 [db] -40 0-10 -20-80 -60-40 -20 0 20 40 60 80 phase [º] measured CP simulated CP measured XP -30-40 -80-60 -40-20 0 20 40 60 80 phase [º] 3D Pattern: 2D Pattern: Gain: 26.5 dbi directivity: 28.1 dbi Efficiency: ~68% 22
Passive Reflectarray Prototype Measurements: Radiation Patterns (11.5-12-12.5 GHz): φ=0º (x axis) 0-10 12GHz 11.5GHz 12.5GHz [db] -20-30 -40-80 -60-40 -20 0 20 40 60 80 phase [º] Axial Ratio (steering direction): 2 [db] 1 Gain: 26.5 dbi directivity: 28.1 dbi Efficiency: ~68% 0 11,5 11,75 12 12,25 12,5 freq. [GHz] 23
4. Reconfigurability: Phase shifters 24
Towards reconfigurability For reconfigurability: 1- Mechanical variation: feeder movement Some disadvantages: Reduced steering variation. Mechanical controlling 2- Electronic variation: phase variation at the Txarray or Rxarray A- Electronically reconfigurable radiating elements: Advantages: Costs. Tinny space necessary. Withdraws: Control circuit. Crosspolar levels. B- Electronically reconfigurable phase shifters: Advantages: Technologically feasible. Discrete (bits) control. Withdraws: Costs. Number of elements. Control circuit. 25
A. Active radiating elements Active Patch Scheme: Expected Behavior: Variation in patch equivalent impedance changes in working frequency changes in the phase behaviour of S parameters. Patch with surface Varactor: Basic equivalent Circuit. 26
A. Active radiating elements Simulation Model: Two ways of defining simulations: 1- Complete Simulation with general purpose simulation SW: CST, HFSS, SEMCAD, etc. 2- Simulation with connection of a variety of S parameter boxes, for the different active patch elements. 27
A. Active radiating elements 1 st Model (Complete model) With Cmin (0.13 pf) Simulation results with CST: With Cmax (2.0 pf) 2 nd Model (Boxes model) With Cmin (0.13 pf) With Cmax (2.0 pf) 28
A. Active radiating elements Circuit layout Patch Prototype: Some active patch details: Choke Inductance Varactor Decoupling capacitor Patch over substrate with ε r = 2.17. Unions with conductive epoxy. Varactors for microwave purpose. x6 x10 Reflection scheme: S 11 The phase behaviour is assumed to be twice the phase behaviour considered in a transmission scheme. Measurement Schemes: Transmission scheme: S 12 The phase behaviour of the patch is directly the measured one. 29
A. Active radiating elements Reflection model: Transmission model: With Cmin With Cmin With Cmax With Cmax Laboratory Measurements 30
A. Active radiating elements Phase Range: Crosspolar Level: To avoid polarization rotation or parasitic polarization (high crosspolar), the connection of the active circuitry is performed in the symmetry axes of the patch. Active Circuitry With the reflection model up to 200º could be achieved in a go and return scheme (100º for each way). Patch Feeding Symmetry line Radiation pattern for 4.5v polarization voltage: With the transmission model, the phase variation decreases (up to 80º, for one way). 31
B. Active phase shifters Phase Shifter Scheme: Subsystem 1: Directional coupler: Input For Txarray: Output Directional Coupler 3dB - 90º Subsystem 2: Reflective circuit: For Rxarray: Directional Coupler 3dB - 90º Input/Output jx ( V ) Z Z 0 / jx ( V ) 0 32
B. Active phase shifters Phase Shifter Design: initial element design 4 port 3dB/90º coupler: Reflective LC circuits: 33
For Linearly Polarized Rxarrays: working scheme B. Active phase shifters P (in/out) Hybrid coupler P1 (in) P2 (out 90º) Reflective circuit L C way 1 way 2 way 3 way 4 L C P4 (isolated) Reflective circuit P3 (out 180º) L C Reflective circuit 34
B. Active phase shifters For Linearly Polarized Rxarrays: reflective circuit varactor printed L printed L varactor Phase Shifter Design: LP integrated design substrate reflective circuits S11 [db] 0-1 -2-3 Amplitude: via transition coaxial feeding port (input/output) 0.13pF 0.23pF 0.39pF 0.65pF 0.82pF -4 1.16pF 1.51pF 2.2pF -5 11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13 Freq [GHz] S11 [deg] 200 0-200 -400-600 hybrid coupler printed L Phase: varactor ground plane 0.13pF 0.23pF 0.39pF 0.65pF 0.82pF 1.16pF 1.51pF 2.2pF 11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13 Freq [GHz] 35
For Linearly Polarized Rxarrays: LP prototype manufacturing details B. Active phase shifters 36
For Linearly Polarized Rxarrays: B. Active phase shifters Phase Shifter: LP integrated prototype S11 [db] 0-1 Amplitude: -2 0v 2v 4v -3 6v 8v 10v -4 12v 14v 16v -5 11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13 Freq [GHz] S11 [deg] 0-100 -200-300 -400-500 Phase: -600 11 11.2 11.4 11.6 11.8 12 12.2 12.4 12.6 12.8 13 Freq [GHz] 0v 2v 4v 6v 8v 10v 12v 14v 16v 37
For Circularly Polarized Rxarrays: B. Active phase shifters working scheme Reflective circuit C L Hybrid coupler 2A P4 P3 (180º) Reflective circuits L C P A(in/out) P1 P2 (90º) P1 P2 (90º) L C P B(in/out) P4 P3 (180º) Hybrid coupler 1 P1 P2 (90º) L C P A P B : way 1 way 2 way 3 way 4 C L Reflective circuit P4 P3 (180º) Hybrid coupler 2B L C Reflective circuits 38
For Circularly Polarized Rxarrays: Phase Shifter Design: CP integrated design B. Active phase shifters Amplitude: Phase: S12 [deg] S12 [db] 0-1 -2 0.13pF 0.23pF 0.39pF -3 0.65pF 0.82pF -4 1.16pF 1.51pF -5 11.5 12 2.2pF 12.5 Freq [GHz] 13 13.5-200 -400-600 -800 460º 0.13pF 0.23pF 0.39pF 0.65pF 0.82pF 1.16pF 1.51pF 2.2pF -1000 11.5 12 12.5 13 13.5 Freq [GHz] 39
For Circularly Polarized Rxarrays: CP prototype manufacturing details B. Active phase shifters 40
For Circularly Polarized Rxarrays: B. Active phase shifters Phase Shifter: CP integrated prototype Amplitude: Phase: S12 [db] 0-1 -2-3 -4 0v 2v 4v 6v 8v 10v 12v 14v 16v -5 11.5 12 12.5 13 13.5 Freq [GHz] S12 [deg] -200-400 -600-800 S12 [deg] -350-500 -650 12.5 GHz -800 0 4 8 12 16 Volts 0v 2v 4v 6v 8v 10v 12v 14v 16v 370º -1000 11.5 12 12.5 13 13.5 Freq [GHz] 41
For Linearly Polarized Txarrays: working scheme B. Active phase shifters 42
B. Active phase shifters For Linearly Polarized Txarrays: Phase Shifter integrated design: Amplitude: S X1 behaviour versus polarization voltage: Phase response for edge values (mask) Structure replication up to 3 times 43
For Linearly Polarized Txarrays: Prototype manufacturing details B. Active phase shifters 44
B. Active phase shifters For Linearly Polarized Txarrays: Output Port Phase Shifter measuring results: Varactor Inductive Line Control circuit connection Input Port Coax. to microstrip transition Amplitude: S X1 behaviour versus polarization voltage: GND Connection Hybrid Circuit Z 0 Ω Transmission Line Holes to Ground Plane S 21 Phase: 45
5. Example of reconfigurable device: Electronically Reconfigurable Transmitarray 46
Electronically Reconfigurable Txarray Transmitarray Scheme: Geometry Applied: Patch grouping by means of bidirectional distribution networks. Constituting elements: Stacked patches: Phase shifters: 12 GHz, BW >0.7 GHz, LP Feeding corrugated horn 6x6 element array. 0,7λ 0 grid. 360º range phase shifters. 2x2 patch groups. Distribution networks: 90º transitions: 47
Electronically Reconfigurable Txarray Towards the complete assembly Phase Shifters Verification and Calibration: Average insertion losses: 3.7 db Average Phase Shift: 379º Control voltage range: 0V to16v Pattern modifications in one of the main axes: Plane φ=0º, θ=0º Plane φ=0º, θ=-10º 48
Electronically Reconfigurable Txarray Transmitarray assembly: Patch layers Radiating interface Complete electronically reconfigurable Txarray assembled Integration in ground plane Complete Prototype: Two radiating interfaces. 72 radiating elements. 18 distribution networks. 9 complete phase shifters. Detail of inner zone Distribution networks Transmitarray core Shifters integration 49
Electronically Reconfigurable Txarray Prototype Measurement: Pattern 1: only phase error correction (all shifters with 0V control voltage). Theoretical radiation pattern Measured Radiation pattern 3D measured radiation pattern 2D measured radiation pattern For prototype validation, two configurations: Pattern 1: only phase error correction (all with 0V control voltage). Pattern 2: phase error correction and reconfiguration of radiation pattern in one of the main axes, applying a 9 degrees tilt. Measured Gain: 16.05 dbi. Reduction due to spillover (accepted horn power 60%=-2.2 db) and shifter insertion losses (3dB mean value in this configuration. 50
Electronically Reconfigurable Txarray Prototype Measurement: Pattern 2: Phase error correction and 9º tilt in one main axis Theoretical radiation pattern Measured Radiation pattern 3D measured radiation pattern 2D measured radiation pattern For prototype validation, two configurations : Pattern 1: only phase error correction Pattern 2: phase error correction and reconfiguration of radiation pattern in one of the main axes, 9 degrees tilt. Measured Gain: 15.1 dbi. Reduction due to spillover (accepted horn power 60%=-2.2 db) and shifter insertion losses (4dB mean value in this configuration). 51
Thanks for your attention! 52
I. MIMO antenna performance parameters Transmitarrays, reflectarrays and phase shifters for wireless communication systems Pablo Padilla de la Torre Universidad de Granada EI3204 Antenna Theory Course 8-10 May 2017