Ultra-wideband antennas. S. Sczyslo, G. Armbrecht, H. Thye, S. Dortmund and T. Kaiser

Transcription

1 On the determination of the impulse response of Ultra-wideband antennas S. Sczyslo, G. Armbrecht, H. Thye, S. Dortmund and T. Kaiser

2 Motivation Each path of the impulse response between two antennas can be separated: Knowledge of the directional antenna impulse response (IR) allows for: Derivation of different antenna parameters, e.g. gain, goup delay more realistic simulations e.g. in a raytracing environment design of more efficient receivers CST User Group Meeting 2010 S.Sczyslo 2

3 Motivation Antenna receive IR relates the incident E-field with the signal at the antenna feeding port by: Antenna transmt IR relates the signal at the feeding port with the transmitted E- field by: Antenna transmit and receive IR relation given by Lorentz reciprocity: => Transmit Simulation in CST Microwave Studio can be used to characterize a passive antenna CST User Group Meeting 2010 S.Sczyslo 3

4 Motivation A new method, the GTEM method, is presented using an easy setup to determine the receive IR: Its final equation is very close to the definition equation of the receive IR: CST User Group Meeting 2010 S.Sczyslo 4

5 Outline Introduction of the cone antenna Simulation of the antenna IR using CST MWS Simulation Setup Deconvolution Presentation of the CST / MATLAB framework Results and Comparison Measurement of the antenna IR using the GTEM Method Pulse propagation in GTEM Cells Method description Results and Comparison Conclusion CST User Group Meeting 2010 S.Sczyslo 5

6 Outline Introduction of the cone antenna Simulation of the antenna IR using CST MWS Simulation Setup Presentation of the CST / MATLAB framework Results Measurement of the antenna IR using the GTEM Method Pulse propagation in GTEM Cells Method description Results and Comparison Conclusion CST User Group Meeting 2010 S.Sczyslo 6

7 Introduction of the cone antenna UWB cone antenna mechanically simple to guarantee identical antennas nearly omnidirectional pattern => single impulse response to characterize azimuth plane low cross polarization compact size (20 mm x 20 mm x 20 mm) CST User Group Meeting 2010 S.Sczyslo 7

8 Outline Introduction of the cone antenna Simulation of the antenna IR using CST MWS Simulation Setup Presentation of the CST / MATLAB framework Results and Comparison Measurement of the antenna IR using the GTEM Method Pulse propagation in GTEM Cells Method description Results and Comparison Conclusion CST User Group Meeting 2010 S.Sczyslo 8

9 Simulation Setup Determine antenna transmit IR: Extract E-field component in farfield condition Extract excitation signal Deconvolve both signals E-field probes (farfield) Broadband Farfield Monitor Time consuming to define all probes Check Farfield/RCS Check Transient farfields CST User Group Meeting 2010 S.Sczyslo 9

10 Deconvolution Applying a Wiener filter in the FD leads to the following deconvolution (see also [1]) : λ aims to bound in case of low SNR. Identify signal+noise and noise parts of the energy spectral density λ can be calculated with the noise part which is limited by ω s : [1] S. Sczyslo, H. Thye, G. Armbrecht, S. Dortmund, and T. Kaiser, Determination of the impulse response of uwb antennas using gtem cells, in Ultra-Wideband, ICUWB IEEE International Conference on, Sept. 2009, pp CST User Group Meeting 2010 S.Sczyslo 10

11 CST -> MATLAB Framework Export Farfield Framework allows for conversion of Antenna Farfield to MATLAB (time & freq dependent) Extraction of different parameters in MATLAB e.g. antenna impulse response, Gain Macro in CST includes GUI MATLAB script is guided in command line (GUI in next version) Downloadable soon (May 2010 after evaluation) at: CST User Group Meeting 2010 S.Sczyslo 11

12 Results Plane wave to indicate to Lorentz reciprocity Perfect matching between all three extraction methods CST User Group Meeting 2010 S.Sczyslo 12

13 Outline Introduction of the cone antenna Simulation of the antenna IR using CST MWS Simulation Setup Presentation of the CST / MATLAB framework Results and Comparison Measurement of the antenna IR using the GTEM Method Pulse propagation in GTEM Cells Method description Results and Comparison Conclusion CST User Group Meeting 2010 S.Sczyslo 13

14 Pulse propagation in GTEM cell absorber septum resistor network input port CST User Group Meeting 2010 S.Sczyslo 14

15 Simulation of pulse propagation in GTEM cell Excitation pulse Simulated E y in CS1 CS1 CS2 tude 0.8 P1 P2 norma alized amplit time [ns] TEM waveguide developed d 20 years ago frequently used measurement device in EMC for immunity and emission measurements CST User Group Meeting 2010 S.Sczyslo 15

16 Measurement of pulse propagation in GTEM cell downtime t D defines the time intervall until reflections occur at the measurement position reflections are related to the rear end of the cell IR of GTEM cell can be modelled by a weighted dirac impulse response (see also [2]) [2] H. Thye, G. Armbrecht, and M. Koch, Pulse propagation in gigahertz transverse electromagnetic cells, in IEEE Transactions on Electromagnetic Compatibility, vol. 51, no. 3, Aug CST User Group Meeting 2010 S.Sczyslo 16

17 GTEM method: System Theory Model of the Setup As has been shown the impulse response of the GTEM cell can be modeled by a weigthed Dirac impulse within downtime t D => applying time gating techniques, the IR can be modeled by: => CST User Group Meeting 2010 S.Sczyslo 17

18 GTEM method: Tradeoff in antenna placement CST User Group Meeting 2010 S.Sczyslo 18

19 GTEM method: Measurement Setup Pulse Generator PicoSecond 4015D GTEM 5305 Cone antenna inside the GTEM cell Sampling Oscillocope Agilent Infinium 86100B Pulse Generator: A = -1.9 V t FWHM = 22ps Oscilloscope: av_cycle = 1024 t_scale = 500 ps/div N points = 405 pts/div (interpolation) CST User Group Meeting 2010 S.Sczyslo 19

20 Results using a cutoff frequency f c = 15GHz nearly perfect match between CST simulation and measurement with GTEM method slight oscillations for t > 0.3 ns CST User Group Meeting 2010 S.Sczyslo 20

21 Outline Introduction of the cone antenna Simulation of the antenna IR using CST MWS Simulation Setup Presentation of the CST / MATLAB framework Results and Comparison Measurement of the antenna IR using the GTEM Method Pulse propagation in GTEM Cells Method description Results and Comparison Conclusion CST User Group Meeting 2010 S.Sczyslo 21

22 Conclusion It was shown how to determine the impulse response of an antenna by simulation and measurement A new framework taking advantage of CST MWS s farfield monitor and MATLAB was presented GTEM method was presented as an efficient method to measure the antenna impulse response a nearly perfect match between both methods could have been achieved CST User Group Meeting 2010 S.Sczyslo 22

23 Thank you for your attention CST User Group Meeting 2010 S.Sczyslo 23