Yoshiyuki FUJINO National Institute of Information and Communications Technology, Japan Wireless Power Transmission Activity in NICT

1 RRL Technical Report ( ) Stratosphere Radio Relay System ( ) Rectennas for small airplane experiment Rectennas for Airship experiment Random Rectenna Array (2006) R&D of ETS-8 ( ) S-band Active Phased Array Beam direction changes of large-scale antenna on ETS-8 at the satellite orbit

2 RRL Technical Report ( ) Based on NASA/DoE Project SSPS Study in RRL (now NICT) Mainly electromagnetic environmental point of view. Upper atmosphere effect for high RF power Ground EMC assessment by SSPS, etc

3 Wireless Power Transmission Activity in NICT RRL Technical Report ( ) Stratosphere Radio Relay System ( ) Rectennas for small airplane experiment Rectennas for Airship experiment Random Rectenna Array (2006) R&D of ETS-8 ( ) S-band Active Phased Array Beam direction changes of large-scale antenna on ETS-8 at the satellite orbit

4 Stratosphere Radio Relay System ( ) Rectenna for small airplane experiment (MILAX, 1992) Rectenna for Airship experiment (ETHER, 1995)

5 MILAX demonstration (1992.8) MIcrowave Lifted Airplane eXperiment. 350m, 40 sec flight is succeeded 29 th, Aug.,1992. Tx power Rx power Height Rectenna efficiency 52%

6 A Rectenna Array for ETHER (1995) For Energy Transmission toward High altitude airship ExpeRiment Antenna : Circular Microstrip Antenna Polarization : Dual polarization Frequency : 2.45GHz Subarray Panel Size : 34.1cm×42.7cm Number of elements : 20 Nominal input power flux density : 850 W/m 2 Efficiency : 81% Rectenna array for ETHER Size : 2.7m×3.4m Confirmed maximum power 2.8kW

7 Wireless Power Transmission Activity in NICT RRL Technical Report ( ) Stratosphere Radio Relay System ( ) Rectennas for small airplane experiment Rectennas for Airship experiment Random Rectenna Array (2006) R&D of ETS-8 ( ) S-band Active Phased Array Beam direction changes of large-scale antenna on ETS-8 at the satellite orbit

8 Random Rectenna Array - Harmonics re-radation from a rectenna - Harmonics are generated by the diode which is a nonlinear device included in the rectenna. Normally, such harmonics are removed by the filter, but rest of the components are re- radiated to the space. EMC Problems for existing communication system Rectenna and re-radiation of harmonics

9 Concept of a Random Rectenna Rrray (RRA) In-Phase rectenna array φφφφ Averaged Directivity Normally, in the rectenna array, due to the phase of the re-radiated harmonics, strong directivity is observed in specific direction. So, re-radiated phase can be controlled randomly. Random Rectenna Array φ1φ1 φ2φ2 φ3φ3 φnφn

10 Outer view of 25-elements 2-D Random rectenna array AntennaRectifying circuit

11 Measurement result (1) 5 elements linear RRA Sidelobes at ±45°Averaged beam pattern Theory 2.2dB suppression Experiment 2.4dB suppression In-PhaseRRA Exp.Theory

12 Measurement result (2) 25 elements 2-D RRA Sidelobes at ±45°Averaged beam Error with measurement value Valiations of amplitude and phase error of rectenna array Validity of random rectenna array is confirmed Theory 10.0dB suppression Experiment 6.0dB suppression Exp. Theory

13 Summary To suppress re-radiated harmonics in a rectenna array, theoretical consideration of a random phase rectenna array (RRA) was investigated. Suppression of 5 dB and 17 dB was respectively shown in the 5- and 100-element linear rectenna arrays. For the simultaneous suppression of 2 nd and 3 rd harmonics, we propose three phase (0,, and 2/3 ) RRA. A linear and 2-D random rectenna array were fabricated in order to compare the directivity with the reference uniform phase rectenna array. In the experiment, 6.0-dB harmonic suppression was confirmed in the 25-element 2-D random rectenna array. The validity concerning harmonic suppression in the random rectenna array (RRA) was confirmed.

14 Wireless Power Transmission Activity in NICT RRL Technical Report ( ) Stratosphere Radio Relay System ( ) Rectennas for small airplane experiment Rectennas for Airship experiment Random Rectenna Array (2006) R&D of ETS-8 ( ) S-band Active Phased Array large-scale reflector antenna pattern measurement of ETS-8

15 Reflector (Transmitting) Reflector 18 m Transmitting array feed S band antenna used for receiving antenna

16 S band Active Phased Array Use self diplexing antenna Thin (less than12cm),Light weight (less than 17kg) Analog voltage control phase shifter (No bit error) Use antenna module Sum and Diff. pattern tracking is available

17 Outer view of ETS-8 Large Deployable Reflector 37 Feed Tx Unit Feed Rx Unit Two Tennis courts 24m×11m

18 Beam is moved to left hand side (west side) Received level variation Akashiincrease Kita-kyusyudecrease Yamagawa decrease - y East West Kyusyu beam and earth station

19 Daily variation of receiving level of kyusyu beam

20 LDR antenna pattern measurement (1)Verification of daily variation of receiving level (2)Experiment of correcting beam position error Beam shift cased by thermal distortion of reflector Receiving level is changed by beam shift.

21 Eclipse Example of level variation around eclipse in spring

22 Temp sensor data

23 Beam shift at the Eclipse Before ecripse22 20 After ecripse After ecripse After ecripse Variation of Beam direction

24 LDRA pattern measurement Conclusion (1)Pattern measurement results of LDRA was shown. (2)Daily variation of receiving level at earth station cased by beam shift. (3)Thermal distortion of reflector causes the beam shift. Space base large scale antenna is also important in SSPS technology, so this will be variable data for such system.

25 Summary We Introduced Wireless Power Transmission Activity in NICT. It has two lineup. One is for Rectenna array development for Microwave Power Transmission. The other is Space Communication technology that can be applicable to WPT. Both lineup is introduced.

26 12 (Local Time) sun TX ETS- 146°