1. FractalComs Exploring the limits of Fractal Electrodynamics for the future telecommunication technologies INFORMATION SOCIETY TECHNOLOGIES (IST) PROGRAMME Quality Factor and Radiation Efficiency Measurement of Genetically Designed Planar Monopoles WP4 Fractal devices development Task 4.3: Prototype construction and measurement J.M. González and J. Romeu May 2003

2. FRACTALCOMS T0+18 22-23 / 05 / 2003 2  University of Granada applied GA for the design of Koch-like small antennas, developing a Pareto tool to optimize several characteristics of pre-fractal wire antennas simultaneously.  The code was also used to generate Euclidean structures to investigate wether fractal shapes might be the best alternative for the design of efficient antennas with minimum resonant frequency.  NEC was used to carry out the simulations.  The space to be filled by the antennas was a rectangle of dimensions h x w. University of Granada Request (1)

3. FRACTALCOMS T0+18 22-23 / 05 / 2003 3 Pre-fractal Meander Line Zigzag Resonant Freq. Matching Freq. Matching Quality Factor Efficiency University of Granada Request (2) 868 MHz 878 MHz -7.6 dB 13.6 96.7 % 827 MHz 836 MHz -8.3 dB 12.8 97.1 % 825 MHz 836 MHz -7.3 dB 14.1 96.7 % h=6.22 cm w=1.73 cm a=6.45 cm a=6.24 cm Copper wire  = 0.2 mm

4. FRACTALCOMS T0+18 22-23 / 05 / 2003 4  Standard electronics printed circuits board photo-etching technology was used to manufacture the monopoles.  FR4 fiberglass substrate: thickness 0.25 mm. Copper strips: 0.29 mm width and 0.25  m thick to have the same electrical section than the wire models.  Monopoles were mounted on a 80 x 80 cm ground plane.  Connection to the RF source through an SMA connector. Fabricated Monopoles (1)

5. FRACTALCOMS T0+18 22-23 / 05 / 2003 5 Meander LineZigzag /4 Pre-fractal Fabricated Monopoles (2)

6. FRACTALCOMS T0+18 22-23 / 05 / 2003 6   and Q measured using the Wheeler cap method.  The input impedance of the AUT is measured at the resonant frequency of the antenna with and without a cap. The cap is a metallic surface that completely encloses the AUT. Measurement Procedure (1) /2  Z in =R r +R  +jX in Z cap =R  +jX cap @ at resonance f 0 : @ RLC model:

7. FRACTALCOMS T0+18 22-23 / 05 / 2003 7  To accurately model the input impedance of the antenna as an RLC circuit (series or parallel) a rotation on the measured data is applied to the Smith chart plot. Measurement Procedure (2) Matching Freq.= Resonant Freq. Matching Freq. Free-space input impedance Resonant Freq. Rotation Angle Wheeler cap input impedance Rotated free-space input impedance Rotated Wheeler cap input impedance

8. FRACTALCOMS T0+18 22-23 / 05 / 2003 8  The cap used to carry out the measurements was an aluminium cylinder (height: 12.5 cm; diameter: 6 cm). Measurement Procedure (3) -12 -10 -8 -6 -4 -2 0 2 123456 0.1 Return Losses (dB) f (GHz) TM 01,1TM 01,5TM 01,9 TE 11,i TE 21,i radianlength limit Modes inside a cylindrical cap excited by a /4 monopole resonant at 694 MHz and skewed 10º.

9. FRACTALCOMS T0+18 22-23 / 05 / 2003 9  Radiation Efficiency Measurement Results (1) t: strip thickness; w: measured strip wideness; w': desired strip wideness;  : measured radiation efficiency;  ':  corrected radiation efficiency;  simulated : computed radiation efficiency;

10. FRACTALCOMS T0+18 22-23 / 05 / 2003 10 Measurement Results (2)  Quality Factor Q: measured quality factor; Q simulated : computed quality factor;

11. FRACTALCOMS T0+18 22-23 / 05 / 2003 11 Conclusions  The expected behavior of GA designs was assessed by comparison with a /4 monopole.  Differences between simulated and measured designs:  wires / strips (  same electrical section)  no connector / SMA connectorsoldering losses  conductivity of copperadditional losses  Not corrected effects:  contact between cap and ground plane  sistematical errors: do not influence measured  but Q