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KAPTEOS CHARACTERIZATION OF COMPACT ANTENNAS

VECTORIAL E-FIELD MEASUREMENT & CHARACTERIZATION OF ULTRA COMPACT ANTENNAS

Typical experimental setup

 

Kapteos eoProbe as RX antenna on Cartesian robot

 

Kapteos Calibration in the right Reference Planes

Kapteos Calibration Process

 DIFFERENCE BETWEEN OPTICAL & RF RX LINK
– NO SIMPLIFICATION FOR RF RX LINK
– FOR OPTICAL RF LINK:

Perfect isolation S12 =
Output RL (Return Loss) given only by eoSense R
Input RL linked at 1st order only to horn R
Chain IL simply equal at 1st order to ILhorn x ILeoSystem

THE ADVANTAGES OF THE KAPTEOS OPTICAL RX LINKS ARE: 
– Rigorously perfect isolation K12 = 0
– Almost infinite input Return Loss K11 ≃ 0
– Whatever DUT upstream Kapteos system rigorously perfect decoupling of output Return Loss S22 = K22
– Straightforward de-embedding of Kapteos system
Insertion Loss ← H21 ≃ 0 S21 / K21
For magnitude → Scalar Kapteos system calibration Scalar Kapteos system calibration
For phase → Scalar Kapteos system calibration Straightforward post-treatment

Kapteos Centered probe

  • K21 SUBSTRACTION

      – Minimum on σ on φS21 for βL/f = 12.89 °.μs

       

      Kapteos Centered probe z=0

    • – Phase accuracy → 1.7°

      USE OF MEASUREMENTS

    • Evolution of corrected phase with z

     

    Kapteos Evolution of corrected phase with z

    Evolution of S21 corrected phase with z

    Kapteos Centered probe at 19 -

     EVOLUTION OF S21 CORRECTED PHASE WITH Z

    – Perfect agreement with theory

    • In far-field region
    • In transition zone

     – Lower phase slope in near field region

    • Due to effective permittivity ≠ 1 in presence of optical probe
    • Phase velocity can be deduced

     – Effective optical probe permittivity

    • 3.6 @ 20 GHz

     

    PROBE INTERFERENCE ON HORN ANTENNA

    Evaluation from S11

     

    Kapteos Centered probe at 140

    No measurable interference down to 2λ

     

    HYPOTHESES

    Kapteos Hypotheses

    Kapteos Hypotheses Graph -

    AT BOUNDARY OF NEAR-FIELD REGION

    Negligible effect of probe from ~19 →21 GHz

    Kapteos Centered probe at z=14mm

     CALCULATION OF BEAM DIVERGENCE

    eoProbe sensitivity axix

    Kapteos Calculation of beam divergence

    Kapteos Centered Probe at 19GHz

     UNCERTAINTY ON S21 VERSUS S21

    Kapteos Centered Probe at 19GHz PS21

    Fit 2 → Scalar Kapteos system calibration noise contributions
    ● Noise floor
    ● Asymptotic measurement accuracy (~ 0,2 dB)

    RÉSUMÉ OF OBTAINED RESULTS

    VNA measurements parameters
    – Injected power 0 dBm, → Scalar Kapteos system calibration RBW = 10 Hz, no AVG
    ● Obtained results (@ 20 GHz & z = 0 mm otherwise written)
    – Equiv. optical fibre length → Scalar Kapteos system calibration 7417 ± 35 mm
    – Absolute eoSystem dephasing → Scalar Kapteos system calibration 4499 ± 21 rad
    – Negligible probe interference for z ≥ λ
    – Acceptable probe interference down to z = 0 mm
    – Probe effective permittivity ~ 3.6
    – RF beam Rayleigh distance → Scalar Kapteos system calibration 7.55 ± 0.45 mm
    – Magnitude accuracy on S21: ± 0.23 dB
    – Relative phase accuracy on S21: ± 1.7 °
    – No de-embedding required
    – No incessant calibration required

    Kapteos Résumé of obtained results image with eoProbe and TX antenna

    2D E-FIELD MAPPING

    Co-polar 2D mapping (120 points / mapping)
    – Spatial step in x direction → Scalar Kapteos system calibration 2 mm
    ● -11mm ↔ 11 mm (12 values) 11 mm (12 values)
    – Spatial step in y direction → Scalar Kapteos system calibration 2 mm
    ● -9 mm ↔ 11 mm (12 values) 9 mm (10 values)
    – Frequential step: 1 GHz
    ● 19 GHz ↔ 11 mm (12 values) 22 GHz (4 values)
    ● Graphs
    – Modulus – contour lines every 1 dB
    ● Max in red
    – Phase – contour line every 10°

    Kapteos 2D E-field mapping

    MAIN POLARISATION

    S21 magnitude @ 19 GHz

    Kapteos Main Polarization at 19GHz z=5mm -

     

    ● S21 phase @ 19 GHz

    Kapteos S21 phase 19 GHz Main Polarization at 19GHz z=5mm

     

    ● S21 magnitude @ 20 GHz

    Kapteos Main Polarization at 20GHz z=5mm

     

    ● S21 phase @ 20 GHz

    Kapteos Main Polarization S21 phase at 20GHz z=5mm

    ● S21 magnitude @ 21 GHz

    Kapteos Main Polarization S21 magnitude at 21 GHz z=5mm

    ● S21 phase @ 22 GHz

    Kapteos Main Polarization S21 phase at 22GHz z=5mm

    CAUSSIAN BEAM FIT OF MAIN POLARISATION

    f = 20 GHz
    – Measurement in orange
    – Fit in blue

    Kapteos Gaussian beam fit of main polarisation

    f = 20 GHz
    Residue → RF beam close to a gaussian beam even in the near-field region!

    Kapteos Gaussian beam fit of main polarisation f = 20 GHz

    RF BEAM PARAMETERS

    Extracted from gaussian fit of 2D field mapping

     

    = 19 GHz

    = 20 GHz

    = 21 GHz

    = 22 GHz

    Beam
    center
    (x0,y0)
    in mm

    (0.6 ; -0.1)

    (0.4 ; 0.5)

    (0.8 ; -0.2)

    (0.7 ; 0.0)

    Beam waist
    (ωx,ωy)
    in mm

    (10.6 ; 10.1)

    (11.7 ; 10.5)

    (10.8 ; 10.9)

    (11.8 ; 11.7)

    Max(ρS21)

    -49.1 dB

    -49.9 dB

    -47.9 dB

    -53.4 dB

    ● Beam center
    – x0 = 0.6 ± 0.2 mm & y0 = 0.1 ± 0.3 mm
    ● Beam waist @ 1/e² of max power
    – ωx = 11.2 ± 0.6 mm & ωy = 10.8 ± 0.7 mm

    NEAR TO FAR FIELD TRANSFORMATION

    ● Measurement of magnitude at = 5 mm

    Kapteos Near to Far field transformation Measurement of magnitude at z = 5 mm

    NEAR TO FAR FIELD TRANSFORMATION

    ● Forward propagation at = 15

    Kapteos Near to Far field transformation Forward propagation at z = 15 mm

    NEAR TO FAR FIELD TRANSFORMATION

    ● Forward propagation at = 105 mm

    Kapteos Near to Far field transformation Forward propagation at z = 105 mm

    NEAR TO FAR FIELD TRANSFORMATION

    ● RF power propagation

    Kapteos Near to Far field transformation RF power propagation at 19GHz -

    NEAR TO FAR FIELD TRANSFORMATION

    ● RF phase propagation

    Kapteos Near to Far field transformation RF phase propagation at 19GHz

    BREACKTHROUGH IN ANTENNA CHARACTERIZATION

    ● Kapteos technology leads to a comprehensive vectorial near-field characterization of antennas and arrays without any compromise on performances!

    Kapteos Breakthrough in antenna characterization

     Application Note: Vectorial E-field measurement & characterization of Ultra Compact Antennas