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transmission (WPT). The difference between the WPT and communication systems is only efficiency.
power to receiver. It was proved that the power transmission efficiency can approach close to 100%.
some good optical approaches in Russia.
transmitting antenna is ten times larger than that on the edge of the transmitting antenna.
 Garmash, V.N., Katsenelenbaum B.Z., S.S.Shaposhnikov, S.S., V. N. Tioulpakov, and R. B.
over the globe preferably in small amounts, ranging from a fraction of one to a few horse-power.
power to the Tesla coil resonated at 150 kHz. The RF potential at the top sphere reached 100 MV.
radio waves whose wave length was 21 km.
microwaves, 1-10 GHz radio waves, was achieved by invention of the magnetron and the klystron.
concentrate a power to receiver with microwaves.
He and his team succeeded in the largest MPT demonstration in 1975 at the Venus Site of JPL Goldstone Facility (Fig. Distance between a transmitting parabolic antenna.45 GHz microwave.2. overall DC-DC total efficiency was only 26.2.2.5 % at 39WDC in Marshall Space Flight Center. DC-DC total efficiency was finally 54 % at 495WDC with magnetron in Raytheon Laboratory (Fig. Fig.3).3 First Ground-to-Ground MPT Experiment in 1975 at the Venus Site of JPL Goldstone Facility DC-RF-transmission-RF-DC total efficiency with 2. whose diameter 5 .2).2. Brown  Fig. In parallel. In 1975.2 MPT Laboratory Experiment in 1975 by W. In 1970.
Glaser proposed a Solar Power Satellite (SPS) in 1968.4 MINIX rocket experiment in microwave and ionospheric plasmas. respectively. Japanese scientists progressed the MPT technologies and research.2. Science.4 m x 7.Microwave Energy Transmission in Space) in 1993. and a rectenna array.5 SHARP flight experiment and 1/8 model in 1987  6 . whose size was 3. In 1980s. Hiroshi Matsumoto’s team carried out the first MPT experiment in space.388GHz was 450 kW from klystron and the achieved rectified DC power was 30 kWDC with 82. and Medical) for the MPT system. 2. After 1990s. The rocket experiment were called MINIX (Microwave Ionosphere Nonlinear Interaction eXperiment) in 1983 (Fig. 2. many MPT laboratory and field experiments were carried out in the world.4) and ISY-METS (International Space Year . In 1983 and 1993.8 GHz of the ISM band (ISM=Industry.was 26m. they used cooker-type 800W-2.45 GHz or 5. E. New wave-wave-particle interaction phenomenons were observed in the MINIX.45GHz magnetron for microwave transmitter.2 m. P. Based on the Brown’s work. Canadian group succeeded fuel-free airplane flight experiment with MPT in 1987 which was Fig. The transmitted microwave of 2.5% rectifying efficiency. They focused nonlinear interaction between intense Fig. Plasma theory and computer experiments supported the observations. In the MINIX 1983 experiment. We often uses 2. was 1 mile.
new devices and microwave circuit technologies. retrodirective microwave transmitters.5 MILAX Airplane Experiment and Model Airplane with Phased Array in 1992 Fig. there were many field MPT experiments such as fuel-free airplane flight experiment with MPT phased array with 2. C. rectennas.6).7 SPS Demonstrator “SPRITZ” with 5.2.2. ground-to-ground MPT experiment with power Fig. there are many MPT research and development after W. Brown. In Japan.2.8 GHz experiment in Japan in 1994-95 (Demonstration in IAC2005) 7 .45 GHz (Fig. 2.5).called SHARP (Stationary High Altitude Relay Platform) with 2. In USA.6 Ground-to-Ground MPT Fig. for instance.411 GHz in 1992 (Fig. 2.
1904. Science”.1. H. “The transmission of electric energy without wires”.8 GHz in 2000 (Fig.8 Grand Bassin. 78.104-11  Matsumoto. H.. pp. “Theoretical Analysis of Nonlinear Interaction of Intense Electromagnetic Wave and Plasma Waves in the Ionosphere”.273.2.857-886  Matsumoto.. pp. 1995.company and universities in 1994-95 (Fig. IEEE Microwave Magazine. 1984.. Vol...  Tesla. Figure 2.189- 191. Vol. Omura.. “Power from the Sun.7) with 2. The Radio Science Bulletin. Electronics and Communications in Japan. W. “Experiments with Alternate Current of High Potential and High Frequency”.9). As described before. there is only quiet small difference between the WPT and wireless communications. 1973 G. W. 9. In Europe. No. N. C. “Microwave Power Transmission from Space and Related Nonlinear Plasma Effects”. H. We will show recent WPT technologies based on the wireless communications. pp. Y..MTT International Microwave Symposium Digest of Technical Papers 73. some kinds of retrodirective microwave transmitters. pp..2. H.  Brown. 1973.36-45  Matsumoto. N.2.. They plan ground-to-ground MPT experiment in Re-union Island (Fig. development of SPS demonstrator with 5.11-35  Matsumoto. and many rectennas were also developed in Japan. Some kinds of microwave transmitters. No.162. fuel-free airship light experiment with MPT in 1995 with 2. Hashino. some unique technologies are developed. Shinohara. H. and Y. E. N. N. IEEE Trans. Co. Part3.45 GHz.Y. 32.. pp.  Glaser.45 GHz. “Computer Simulation on 8 .1230-1242  Brown. McGraw Pub. December 2002. pp. Reunion.11. Shinohara. H. 1968. C. 1904. France and Their Prototype Rectenna  References  Tesla. Hashino.. Y. MTT. No. “Research on Solar Power Station and Microwave Power Transmission in Japan : Review and Perspectives”. and N. “The History of Power Transmission by Radio Waves”. March 5.8). No. Yashiro. Hirata. The thirteenth Anniversary Number of the Electrical World and Engineer. P. 1995. “Adapting Microwave Techniques to Help Solve Future Energy Problems”.
vol. pp.89-103  Schlesak.ca/SHARP/sharp. S. No.283-286  http://friendsofcrc. Digest. pp. L.9-17  Kaya..125.. 1998. C.1.11.4. “Space Solar Power Programs and Microwave Wireless Power Transmission Technology”. “Case study in Reunion island. Chabriat. and H. “MILAX Airplane Experiment and Model Airplane. 54. Vol.1. “Dependence of dc Output of a Rectenna Array on the Method of Interconnection of Its Array Element”. and M. 1988. Ohno. IEEE MTT-S Int. “The Grand-Bassin Case Study: Technical Aspects”. Acta Astronautica”. 1997. Tokyo. Luk. and J. pp. Fujita. No. A microwave powered high altitude platform. Symp.255-258  Celeste. and G. Fujino. S. 2004. December 2002. pp.html  McSpadden. Alden and T.237-245  Celeste. Nonlinear Interaction of Intense Microwave with Space Plasmas”. Japan. Part3.” 12th ISAS Space Energy Symposium. pp. Mankins. Proc. O. P. P. pp. et al.46-57  Matsumoto. Jeanty. H. IEEE Microwave Magazine. No.. J. 1995. Matsumoto. pp. of SPS’97. A. J-D. Vol. 253-258 9 . J.. A. Electronics and Communications in Japan. 78. Space Energy and Transportation. Pignolet. March 1993  Shinohara N. J. Ida. Y. A. 1996. “Transmitting antenna system for airship demonstration (ETHER).. Vol. J. Electrical Engineering in Japan. and G Pignolet. N.
It is possible to steer the direction of the microwave beam. phased array antenna or any other type of antenna.1).1 Antennas for Microwave Power Transmission All antennas can be applied for both the MPT system and communication system.3.2. the phased array antenna was adopted to steer a direction of the microwave beam (Fig. All SPS is designed with the phased array antenna.2 and Fig.3. slot antennas. Yagi-Uda antenna. they changed a direction of the parabolic antenna to chase the moving airship. The antenna elements might be dipoles. we have to use a phased array antenna for the MPT from/to moving transmitter/receiver which include the SPS because we have to control a microwave beam direction accurately and speedy. horn antenna. To fixed target of the MPT system. However. for example. Recent Technologies and Researches of Wireless Power Transmission – Antennas and Transmitters – 3. in MPT demonstration in 1975 at the Venus Site of JPL Goldstone Facility and in ground-to-ground MPT experiment in 1994-95 in Japan (See Fig. Right : for SPRITZ in 2000) 3. or any other type of antenna. The phased array is a directive antenna which generate a beam form whose shape and direction by the relative phases and amplitudes of the waves at the individual antenna elements. microstrip antenna. parabolic antenna.1 Phased Array Used in Japanese Field MPT Experiment (Left : for MILAX in 1992. Fig. In some MPT experiments in Japan.6).3. even parabolic antennas. we usually select a large parabolic antenna. In the fuel-free airship light experiment with MPT in 1995 in Japan. We consider the phased array antenna for all following MPT system. for example.2.2 Recent Technologies for Transmitters The technology employed for the generation of microwave radiation is an extremely important 10 .
The magnetron is self-oscillatory device in which the anode contains a resonant RF structure.1 Magnetron r r Magnetron is a crossed field tube in which E × B forces electrons emitted from the cathode to take cyclonical path to the anode.2. we need higher stabilized and accurate phase and amplitude of microwave when we use phased array system for the MPT. the microwave tube has higher efficiency (over 70%) and the semiconductor has lower efficiency (below 50%) in general. Fig. There are two types of microwave generators/amplifiers. Especially. 3. Trew reviewed microwave generators/amplifiers. One is a microwave tube and the other is a semiconductor amplifier. These have electric characteristics contrary to each other. averaged power as shown in Fig. We have to choose tube/semiconductor case by case for the MPT system. Although there are some discussion concerning generation/amplifier efficiency.1 Average RF output power versus frequency for various electronic devices and semiconductors 3. such as a cooker-type magnetron. W. The microwave tube. For highly efficient beam collection on rectenna array. magnetron is very economical. frequency vs.1. The magnetron has long history from invention by A. can generate and amplify high power microwave (over kW) with a high voltage (over kV) imposed. The semiconductor amplifier generate low power microwave (below 100W) with a low voltage (below fifteen volt) imposed. Hull in 1921. It is still expensive currently.3. We need higher efficient generator/amplifier for the MPT system than that for the wireless communication system. The practical and efficient magnetron tube gathered world interest only after K. Okabe 11 .subject for the MPT system.
Magnetron technologies were advanced during the World War II. Therefore. Korean and Chinese more reduce the cost of the microwave oven now. Brown who invented a voltage controlled oscillator with a cooker-type magnetron in a phase locked loop. nearly all of them Japanese. If we do not make a phased array to control beam direction electrically.5GW/year for all magnetrons used in microwave ovens whose production is 50 – 55 millions. Compared that American tube’s cost was $300 and they planned to sell for $500 in 1960’s.45 GHz. S. As a result. Peak levels of higher harmonics are below -60 dBc and other spurious is below -100 dBc.S. A. the magnetron of 500 – 1. There is a net global capacity of 45. the magnetron is suitable device for the MPT because of high efficiency and low cost and unsuitable device because of its unstable frequency and uncontrollable phase. the cooker-type magnetron itself cannot be applied for the phased array-type MPT because it is only a generator and we cannot control/stabilize the phase and the amplitude.000 W is widely used in microwave ovens in 2. The cooker-type magnetron was considered as noisy device.000 ovens at $300 to $400 apiece. C.000. In present. In 1960’s. In 1970. and is a relatively inexpensive oscillator (below $5).2 Phased Array with 2. He could control and stabilize a phase of microwave emitted from cooker-type magnetron.proposed the divided anode-type magnetron in 1928. A history of the magnetron is a history of a microwave oven. Sales increased rapidly over the next 15 years. It was W. the equivalent of about $20. Japan played a important role to reduce the cost of the microwave oven.45GHz Phase Controlled Magnetrons Developed in Kyoto University 12 . the magnetron can be applied for the MPT system. U. Instead of Japanese microwave oven. Japanese tube cost was less than $25. The first microwave oven with a magnetron sold shortly in U. especially in Japanese Army. It is however confirmed that spurious emissions from the cooker-type magnetron with a stable DC power supply is low enough and this can be applied to the MPT system. rising to a million by 1975 and 10 million by 1985. but by 1971 the Japanese had begun exporting low-cost models priced $100 to $200 less. The magnetrons main were advanced and manufactured for the microwave ovens.3.000 today. some research groups try and succeed to develop new magnetron Fig. But history repeats itself. after the World War II ended for more than $2. manufacturers sold 40. However.
Applied frequency of the TWTA is very wide. The TWTA is widely used in television broadcasting satellites and communication satellites. They realized that the frequency stability and an error in phase and amplitude of the PACM are below 10-6. the efficiency of the TWTA is very low. Field in 1945. within 1 degree.4 Estimated TWTA World Market  system design and experiment with 13 .2 Traveling Wave Tube Amplifier (TWTA） Traveling Wave Tube (TWT) was invented by R.3 Trend of DC-RF Conversion Efficiency of TWTA from 1GHz-band to 60 GHz-band. Kompfner in the World War II and was advanced theoretically and improved by J. Pierce and L. respectively. a phase and amplitude controlled magnetron (PACM) has been developed at Kyoto University.system which we can control and stabilize a phase of microwave emitted from cooker-type magnetron-. Before 1980s. and within 1 %.45 GHz and 5. M. the interaction between the RF waves and the electron beam is continuous along the length of the SWS. The technology of the PACM is effective to realize the economical MPT system with light weight and high DC-RF conversion efficiency.3. The TWT is a linear beam tube with helix structure. 3. The helix slow wave structure (SWS) slows the RF waves down to just below the velocity of the electron beam. They have also succeeded to control beam directions with phased arrays with phase controlled magnetrons operated in 2. an injection locking and PLL feedback are adopted as same as that adopted in Brown’s work. The TWTA has a proven track record in space. In their developed magnetrons. The Kyoto University’s system is most stabilized. the higher gain. Japan.3.3. There was no MPT Fig.2).8 GHz (Fig. As an advanced method. around 30%.2. The longer the tube. The TWT can be used for amplifier and we call it TWT amplifier (TWTA). It is not enough to use for the MPT system. R. In the TWT. The difference between the methods proposed in these papers is how to control a phase of the magnetron.  Typical output power of the TWT is a few hundreds watts. Fig.
small size and low weight.3 Klystron The klystron was invented by the Varian brothers in the late 1930s. The paper  describes that main reasons for this price decrease are (1) development time and effort could be reduced due to the standardization of the product.2. the electron beam is modulated and RF is amplified in last. in recent years. 1996=100%)  from 1972 and the price of the TWTA decreases (Fig. Market of the TWTA grows Fig. semiconductor amplifiers.3). 14 . The klystron is also used for uplinks (earth stations beaming to orbital satellites).3. the net conversion rate has risen to around 70 % (Fig. However. The other application of the klystron is fusion. One klystron transmitted microwave of 450 kW and 2. a TWTA uses techniques called velocity tapering energy recovery . 3. we may consider the MPT system with TWTA.5).5 Trend of Price of TWTA (% . (3) manufacturing cost could be reduced by manufacturing larger number of TWTAs in a certain time frame and by more automatization in the manufacturing process.3. This makes MPM into a good candidate for space application because it has high conversion efficiency. and state-of-the-art power supply technology into one package. Electrons are emitted from the cathode and electron beam passes through the cavities.4. there has not been klystron phased array system yet.3. It requires a ponderous power supply and also a heavy magnet. The klystron was used in MPT demonstration in 1975 at the Venus Site of JPL Goldstone Facility. Fig. The klystron is high power amplifier from tens of kilowatts to a few megawatts with high efficiency. In this way. The klystron is suitable for large MPT system such as SPS. and (4) test time and effort has been reduced due to the higher credibility of the product. When RF inputs from input cavity. (2) parts cost could be reduced due to buying higher number of parts and holding them on stock.3.TWTA. over 70%. In near future. The klystron is also a linear beam tube with cavities. Detail general theory of the microwave tubes is described in reference . The SPS designed by NASA/DOE in 1980 was designed with phased array of the klystrons.388 GHz. Trends of development of the TWT are MPM (Microwave Power Module) and phased array TWT. The MPM combines the best aspects of TWT. The klystrons are used for broadcast applications in 400-850 MHz-band. However.
2) high power and high efficient power generation and high efficient detector in a small and light fashion. semiconductor device plays the lead in microwave world instead of the microwave tubes. B. dissolution of tortuous relationship between efficiency and linearity is expected by the MPT. some MPT experiments were carried out in Japan with phased array of semiconductor amplifiers. amplifiers. It does not guarantee the linearity between input and output microwaves and non-linearity causes high spurious which must be suppressed in the MPT. higher harmonics are used effectively to increase efficiency. E. Therefore. To develop the high efficient amplifier. and 3) precise beam control for a large phased array antenna combining with a huge number of sub-arrays. For the microwave amplifiers. Especially F class amplifier is expected as high efficient amplifier for the MPT system.3.2. the large plate model by a layered configuration in a sandwich fashion was proposed.8GHz. It causes that the semiconductor amplifiers keep expensive cost for the MPT system. and so on. The point of this configuration is the 15 . An efficiency of a driver stage is also taken into consideration if the gain of the final stage is not enough. In D. Typical semiconductor device for microwave circuits are FET (Field Effect Transistor). The semiconductor device is expected to expand microwave applications. The maximum efficiency usually is realized at saturated bias voltage. and HEMT (High Electron Mobility Transistor). circuit design theoretically determines efficiency and gain. phase shifters. Some reports noted that it is possible to realize a PAE (power added efficiency = (Pout-Pin)/PDC) of 54%. for example. modulators. These classes are also applied in kHz systems. It causes by advance of mobile phone network. F class amplifiers for microwave frequency. at 5. phased array and Active integrated antenna (AIA).4 Semiconductor Amplifier After 1980s. A. C class amplifiers are classified in bias voltage in device. Present materials for the semiconductor device are Si for lower frequency below a few GHz and GaAs for higher frequency. After 1990s. we need strict adjustment in contrary of mass productivity. It is easy to control a phase and amplitude through the microwave circuits with semiconductor devices. because of its manageability and mass productivity. HBT (Heterojunction Bipolar Transistor). It potentially has low price capability by the mass production. These are champion data in laboratory. for instance. theoretically 100%. We design microwave circuits with these semiconductor devices. These three points may be described as 1) pureness in spectrum. There are unique development items for the SPS from the microwave point of view distinguished from the ordinary use of the microwave technology such as telecommunications. efficiency of about 60%. We always have to consider the efficiency. The other requirement from MPT use to the semiconductor amplifier is linearity of amplifier because power level of the MPT is much higher than that for wireless communication system and we have to suppress unexpected spurious radiation to reduce interference. To cope with the second requirement for the microwave technology.
especially for mobile applications. it is expected that the technical problems will be solved by efforts of many engineers. The AIA is defined as the single entity consisting of an integrated circuit and a planar antenna.3. and their control. Due to the nature of small-size. a power transmission part of the spacetenna (space antenna) can be realized in thin structure.6). They are called wide-bandgap devices such as SiC and GaN.3 Transmitter Issues and Answers for Space Use Largest MPT application is a SPS in which over GW microwave will be transmitted from space to ground at distance of 36.3. In present. Kyoto University’s group have developed a light weight phase controlled magnetron called COMET. poor efficiency. microwave circuit operation and radiation. Prof. thinness. The wide-bandgap devices can make over hundreds watt amplifier with one chip. and low power output. lightness and multi-functions in AIA.6 Compact Microwave Energy Transmitter with the PCM (COMET) 16 . The microwave tube can generate/amplify higher power microwave than that by the semiconductor amplifier. we will use microwave transmitters in space. the “the Active Integrated Antenna (AIA)” technique is considered. For space use. In the SPS. there are some development of microwave amplifiers with SiC MESFET or GaN HEMT. In recent days. The MMIC devices still have heat-release problems. However. 3.000km. A weight of the microwave tube is lighter than that of the semiconductor amplifier when we compare the weight by power-weight ratio (kg/kW). The COMET includes a DC/DC Fig. Lighter transmitters can be realized with the MMIC devices. Kawasaki’s group have developed some AIA system for the MPT application. The other trend is development of MMIC (Microwave Monolithic Integrated Circuit) to reduce space and weight. the microwave transmitter will be required lightness to reduce launch cost and higher efficiency to reduce heat problem. The AIA has many features applicable to the SPS. Compact Microwave Energy Transmitter with a power-weight ratio below 25g/W (fig.effective integration with DC power generation. As one of the promising microwave technologies. new materials are developed fore the semiconductor device to increased output power and efficiency.
6. We should aim for over 80 % efficiency for the microwave transmitter. and C. they can deliver 12g/W and 16. We need special heat reduction system in space.15kg).29-35  Takano. 1999. heat reduction will be a serious problem.15 kg (the TWTA weighs 0. P.8 GHz. pp. therefore. References  Shinohara. pp.xml 17 . the power supply weighs 1. isolators.1 Characteristics of Semiconductor Amplifier for Space Use (most are arranged from a reference ) Satellite ETS-6 TDRSS NSTAR INT-7 JCSAT-3 Efficiency 31% 32% 36% 29% 40% Output 14W 24W 40W 30W 34W 1.8kg. SPS2003-09(SPS2004-02). Rep. Hashimoto. The Radio Science Bulletin. TWTA for satellite use has lighter power weight ratio: 220W at 2.5g/W. H. The power-weight ratio of the COMET is lightest weight in all microwave generators and amplifiers.. V. “Simplification Techniques of the Constitution of Microwave Transmission Antennas of SPS (in Japanese)”. which must include all loss in phase shifters.65 kg (the TWTA weighs 1. Proc. a wave guide. Tech.. If we use high efficient microwave transmitters. A. of IEICE. Although it may seem that semiconductor amplifiers are light in weight. R. Table 3. power circuits. we can reduce weight of heat reduction system. The semiconductor amplifier is not light remarkably. Armstrong. Vol. No. No.inventionandtechnology. antennas. M.5kg 1. and an antenna.2kg 3. Examples of characteristics of various transmitters for space use are shown in Table 3. pp.9kg Weight = 85g/W =121g/W =63g/W =57g/W =56g/W Frequency 2. a wave guide. Especially. respectively. K. They do not include a heat radiation circuit. All lost power converts to heat. “SiC and GaN Transistors—Is There One Winner for Microwave Power Applications?”.45GHz at 2. the SPS is a power station in space.5GHz 4GHz 4GHz Heat reduction is most important problem in space. and an antenna. “Scanning the Technology: Vacuum Electronics at the Dawn of the Twenty-First Century. a control circuit of the phase controlled magnetron with 5. Kamo. IEEE.. 702–716  Trew.com/xml/2005/4/it_2005_4_feat_4. Sugawara. “Phase-Controlled Magnetron Development for SPORTS : Space Power Radio Transmission System”. they have heavy power-weight ratio because output microwave power is very small.5GHz 2GHz 2. IEEE. Hence. Matsumoto. 130W at 5.4kg 2. a heat radiation circuit.. J. Parker. 2004. N.1. 87. and N. the power supply weighs 1. pp. 2002. T.1032-1047  http://www. L.51-58  Granatstein.90.5kg.8 GHz at 2.” Proc.35kg). Vol. and K.7kg 1. 2004.converter.310.
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The retrodirective system is usually used for satellite communication.1 (a) two-sided corner reflector.2)-. The signal received by an antenna is re-radiated by its pair.1(c)).4.4. This array is made up of pairs of antennas spaced equidistant from the center of the array. Therefore. achieving the proper phasing for retrodirectivity. http://hcac. Van Atta array is also a basic technique of the retrodirective system. A signal transmitted from the target is received and re-radiated through the phase conjugate circuit to the direction of the target. A corner reflector is most basic retrodirective system. There are many researches of the retrodirective system for these applications (Fig. Fig. They use the almost same frequency for the pilot signal and returned signal with a local oscillator (LO) signal at a frequency twice as high as the pilot signal frequency in the typical retrodirective systems (Fig.edu/tcwct03/papers/s16p03. wireless LAN. Prof. The signal is called a pilot signal. We do not need any phase shifters for beam forming.1(a)).4. (b) Van Atta Array. thus the order of re-radiating elements are inverted with respect to the center of the array.4.pdf) 20 . Accuracy depends on stability of the frequency of the pilot signal and the LO signal. Retrodirective system is always used for SPS. (Fig. etc. (c) retrodirective array with phase conjugate circuits. Propagation – 4.1(c)) which play a same role as pairs of antennas spaced equidistant from the center of the array in Van Atta array. 4.1(b)).hawaii. Usual retrodirective system have phase conjugate circuits in each receiving/transmitting antenna. Incoming signals are reflected back in the direction of arrival through multiple reflections off the wall of the reflector. Itoh’s group proposed the pilot signal instead of the LO signal.4. Recent Technologies and Researches of Wireless Power Transmission – Beam Control . and connected with equal length transmission lines (Fig. which meet at an apex (Fig.4. Target Detection. military. (Sung et al. ..1 Recent Technologies of Retrodirective Beam Control A microwave power transmission is suitable for a power transmission from/to moving transmitters/targets. The corner reflectors consist of perpendicular metal sheets. accurate target detection and high efficient beam forming are important.
45GHz).4. (f) UCLA in 2000 (6GHz) 21 . (d) Jet Propulsion Laboratory and University of Michigan in 2001 (5. There are other kinds of the phase conjugate circuits for the MPT applications. (b) Kyoto University in 1996 (2. They have also developed the (a) (b) (c) (d) (e) (f) Fig. and the LO signal of 2ωt.2 Various Retrodirective Array with Phase Conjugate Circuits Developed in (a) Kyoto University and Kobe University in 1987 (2.45GHz).9GHz). ωt+∆ω and ωt+2∆ω. ωt indicate a frequency of a transmitter. Kyoto University’s group have developed a retrodirective system with asymmetric two pilot signals. (e) UCLA in 1995 (6GHz). (c) Queen’s University (62-66GHz).
neural network. The “optimum” has multi-meanings. In this method. for example. we cannot form the microwave beam to the desired direction. Computer is usually used for the software rectodirective with the phase data from a pilot signal and for the beam forming with calculation of the optimum phase and amplitude distribution on the array. to increase beam collection efficiency. There are some methods for target detecting with pilot signal which is separated to beam forming. The LO signal is generated from the pilot signals. to suppress sidelobe level. After the target detection. They have used 2. Kyoto University’s group use a pilot signal modulated by spread spectrum in order to use the same frequency band of microwave power beam and the pilot signal and also in order to use two or more pilot signals for multi-target MPT. and to make multiple power beams. Although the best way is to use only one oscillator for the standard of the phase/frequency for one phased array of larger than km in size with more than billion elements. and multi-objective optimization learning. We call the method “software retrodirective”. multi-beams. The retrodirective system unifies target detection with beam forming by the phase conjugate circuits. We can select object of optimum and algorism freely with consideration of time of calculation. Kyoto University in Japan and Texas A&M University in USA have developed the software retrodirective system independently.85 GHz and 5.77 GHz. we need accurate beam forming. The other is self-synchronization with some data sent from the target.45 GHz for ωt. One is wireless synchronization of separated units. The latter system solve a fluctuation problem of the LO and the pilot signal which cause phase errors because the fluctuations of the LO and the pilot signals are synchronous. there are some algorism. we need phase shifters in all antennas. 3. For the optimum beam forming.6 ppm of the frequency and below 3. respectively. genetic algorithm. 22 .5 degree of phase error. The change gives us information on phase corrections. If the standard of the phase/frequency like the LO signal is different on one array. In the software rectodirective. Some trials have been carried out. we can form microwave beam freely. Mitsubishi Electric Corporation in Japan have developed PLL-heterodyne type retrodirective system in which different frequencies for the pilot signal and the microwave power beam. a phase of a part of arrays is changed and a resultant change of the microwave beam intensity is measured in the rectenna site. it is quite difficult. A standard of the phase/frequency is very important to steer microwave power beam to a desired direction Both for beam forming with the software retrodirective and for retrodirective with the phase conjugate circuit. have been used. On contrary. The present accuracy of wireless synchronization is below 0. for instance.other retrodirective system with 1/3 ωt pilot signal and without LO signal. A better way is use of some oscillators on some group of sub-phased array and the oscillators are synchronous with each other.
In recent years there 23 . As the studies for this Question had not been completed by 2002. to extend the Question. 1.5. wireless LAN and DSRC (Dedicated Short Range Communication). Science and Medical) applications. Therefore. Grating lobes and sidelobes of the MPT beam should be low enough in order to make the affected region as small as possible.45 GHz.4. some modulation might be necessary.45 GHz or 5. harmonics. One calculation of the interferences between the MPT of the SPS. 2. If the harmonics of the MPT frequencies are.8 GHz MPT of the SPS was published in Japan. which was incorporated into Document 1A/32-E Annex8) in October 2000 .35 GHz). Power density for the MPT is a few orders higher than that for the wireless communication. 5.1 Interferences to Existent Wireless System Most MPT system adopted 2.45 GHz and 5. Space-to-Earth communications on 11-12 GHz-band. therefore.3-1. no response has been submitted.2. grating lobes should be mitigated because they are a direct loss of transmitter power. ASR (airport surveillance radar. Conversely speaking. the date has been extended by three years. The other interference assessment on 2.9GHz) and MR (meteorological radar.25 . and will submit in 2005. Also. Responses to Question ITU-R 210/1 (1997) had been submitted to the ITU-R WP1A meetings by USA. radars called ARSR (air route surveillance radar. regulated by the ITU (International Telecommunication Union) power flux density (PFD) limits. mainly 2. Carrier noises.7-2.2 Environmental Issues 4. to the wireless communication systems was done in Japan.35GHz).8 GHz band which are allocated in the ITU-R Radio Regulations to a number of radio services and are also designated for ISM (Industry. terrestrial radio relay links on 5GHz (5G-150M) system and 11GHz (11G-50M) system. The bandwidth of the microwave for the MPT do not need wide band and it is enough quite narrow since an essentially monochromatic wave is used without modulation because we use only carrier of the microwave as energy. 4. there is no allowed frequency band for the MPT. JAXA (Japanese Aerospace Exploration Agency) estimated the interference and submitted “Proposal of the extension regarding the termination year of Question ITU-R 210/1 to 2010 from 2005”to ITU in 2004. we used the ISM band. They submit the above document from JAXA in response to Question 210/1 which would otherwise terminate this year. however.2 Safety on Ground One of the characteristics of the MPT is to use more intense microwave than that in wireless communication systems. and applications in the ISM bands. We have to consider and dissolve interferences between the MPT to the wireless communication systems. we have to consider MPT safety for human. Since the response (Document 1A/18-E. They discussed four main existent systems. and spurious emissions of the MPT signal should be quite small to avoid interference to other radio services in operation around the world.2. They discussed mainly Japanese case.
45 GHz and 0.8 GHz.2 dB/km in 5. regardless of the nature of the interaction mechanism. This is different from the EMF research.8 GHz. respectively. and irregularity of air refraction ratio.05 dB.4. Inside the rectenna site.03 dB/km in 2.45 GHz.01 (dB/km) x 5 (km) x sec 47 (degree) = 0.035 dB. The attenuation factor by rain whose intensity is 50 mm/h and 150 mm/h is 0. at either frequency. is used as the basis of the standard.6 or 100 W/m2 as averaged over six min. the general public. Famous guideline. The scientific research results have indicated that the microwave effect to human health is only heating problem.01 dB/km and 0. The SAR (specific absorption rate) threshold for the most sensitive effect considered potentially harmful to humans. it is enough to consider only absorption by the oxygen in the microwave frequency. The SAR is only heating problem. are 81. 4. In the SPS case.3 dB/km and 1. and that the elevation is 47 degree in the Japanese SPS case. respectively.8 GHz. In future MPT system.07 (dB). we calculate the rain attenuation as follows. the ICNIRP (International Commission on Non-Ionizing 2 Radiation Protection) guidelines. It is approximately 0. Scatter by irregularity of air refraction ratio is quite smaller than the absorption and scatter by air and rain. as contrasted with the general public.0013 dB in the 2. the total absorption is approximately 0. Especially. there remains discussion concerning the keep out area.3 Interaction with Atmosphere In general.3. effect of atmosphere to microwave is quite small. There are absorption and scatter by air.8 GHz. at 2. we have to keep the safety guideline outside of a rectenna site. and 1. These two effects are different. It was estimated below 0. Especially. The corresponding limits for IEEE standards for maximum permissible human exposure to microwave radiation. and is normally interpreted to mean individuals who are occupationally exposed to the microwave radiation.45 or 5.45 24 . are 50 or 10 W/m for occupationally exposed vs. Contemporary RF/microwave standards are based on the results of critical evaluations and interpretations of the relevant scientific literature. the absorption by water vapor and oxygen dominate the effect in the air. for controlled and uncontrolled environments. in Japan.45 GHz and 5. respectively.2 (dB) in 5. When elevation is 47 degree in the middle latitude. there have been many research and discussions about effects at 50/60 Hz and over GHz (microwave). for example. 0. The controlled and uncontrolled situations are distinguished by whether the exposure takes place with or without knowledge of the exposed individual.have been considerable discussions and concerns about the possible effect for human health by RF and MW radiation.2.3 or 38. There is long history concerning the safety of the microwave. rain.3 (dB) and 5. In 2. When rain intensity is 50 mm/h and 150 mm/h. the attenuation is 0. In assumption that rain cell size is 5km at 50 mm/h and 3km at 150 mm/h. controlled or uncontrolled area.13 (dB) in 2. respectively. Attenuation factor by rain is shown in Fig.7 W/m2 as averaged over 30 min. the amount of total absorption through the air from space is approximately 0. and 16.007 dB/km.
Although plane of polarization will rotate in approximately 7 degree at 2. The NASA/DOE SPS was designed including the results of the reference  and they decided that maximum microwave power density was 23 mW/ 25 . some interaction between the microwave and the ionospheric plasmas occurs. It is nonlinear interaction between intense microwave and the space plasmas that we have to investigate before the commercial SPS. We theoretically predict that it has possibility to occur Ohmic heating of the plasmas. It is well known that refraction.3 Attenuation factor by rain  plasmas. Total attenuation of the 2.05 + 0. influence to the MPT system is negligible.45 GHz SPS.GHz SPS.4. scintillation.8 GHz is only 0. Faraday rotation. The effect is largest in the lower ionosphere (D and E regions) where the collision frequency is highest. We have to consider a counterplan the attenuation by rain in the 5. respectively.0013 = 0. However.2.45 GHz and 5. there is no inference because diameter of rectenna site will be over km. Total attenuation of the 5. In the 2. and three-wave interactions and excitation of electrostatic waves in MHz bands. we can neglect the attenuation by air and rain. when they calculated theoretically with the Snell's law and total electron contents in the ionosphere.8 GHz SPS is over 5 dB in hard rain circumstance.13 + 0.45 GHz SPS is 0.8 GHz SPS. and absorption occur between weak microwave used for satellite communication and the plasmas. The absorption of the radio waves can be calculated from the electron density and electron-neutral collision frequency profile. there is also no inference because we will use circular polarized microwave for the MPT of the SPS.12 m.45 GHz by Faraday rotation. 4.4 Interaction with Space Plasmas When microwave from the SPS propagates through ionospheric Fig. reflection through the ionosphere at 2. plasma hall effect by Ponderomotive force. These interactions will not occur in existent satellite communication systems because the microwave power is very weak.1813 dB. thermal self-focusing effect of the microwave beam.67 m and 0. However. For example. Perkins and Roble theoretically calculated the Ohmic heating by the microwave beam from the SPS in 1978.
4.4). From these simulation results it was estimated that below 0. They neglected collisions and based the analysis on kinetic equation in collision free plasma. Concerning the three-wave interactions and excitation of electrostatic waves in MHz bands.01 % of the microwave beam energy from the SPS would be converted to electrostatic waves.cm2 at the center of the rectenna site. Shklyar and Shinohara derived a equation of self-focusing effect of the microwave beam caused by the inhomogeneity of the microwave energy density in 1992. Matsumoto predicted in 1982 that the microwaves may decay into forward traveling electron plasma waves (Raman scattering) or ion acoustic waves (Brillouin scattering) and a backward traveling secondary microwave. Both these features could be successfully modeled using a more realistic computer simulation where the nonlinear feedback processes were fully incorporated. These frequencies are typically 2-10 MHz in the local ionospheric plasma. It was found that the excited waves differed from the initial theoretical expectations  in that the line spectrum expected from a simple three-wave coupling theory was in fact a broad spectrum. Matsumoto’s group carried out the first rocket MPT experiment called MINIX (Microwave Ionosphere Nonlinear Interaction eXperiment) in 1983 in order to observe the excitation of the plasma waves (Fig. It occurs without the collisional plasma heating. The electron plasma waves could be Langmuir waves when the excitation is parallel to the geomagnetic field.4 Observed Wave Spectrum Concerning Three-wave Interactions and Excitation of Electrostatic Waves by Microwave in MINIX Rocket Experiment  26 . Though the wave frequency is six orders of magnitude higher than the maximum collision Fig.4. or electron cyclotron waves for excitation perpendicular to the field. and the electron cyclotron harmonics were stronger than the Langmuir waves.
52. Oct. Y.908. Y.465-469  Karode. No. 2003  Van Atta.htm  Gallop..49. there have not been advance of the research yet.16. References  Sung. Itoh. There are only two experimental data concerning the interaction between the intense microwave and the space plasmas. Fusco. pp. pp. Miyamoto.221. and T. D. Sci.9. 220 . K. 2003. No.ac. Y. Murakami. 15-17. and T. A. T. Technol. and T. S. Vol. “Retro-Transceiver Array Using Monopole Antennas”. “Retrodirective Antenna Technology for CubeSat Networks”. IEEE Trans. 2001. Vol.  Miyamoto.49.46. patent No. “Electromagnetic Reflector”. L. IEEE Trans. K. Newberg. J.. since finally they deal with a weak effect of Ponderomotive force. pp. U. vol. B. pp. D. Plasma hall effect is predicted theoretically with Ponderomotive force and it is important to consider the effect from the microwave beam to plasma circumstance. M. No. H.49. Fetterman. Japanese group just start computer simulation with electromagnetic particle code from 2004.. We need advanced space experiment to verify the theoretical studies as soon as possible. Vol. No. “Balanced Subharmonic Mixers for Retrodirective- Array Applications”. V. MTT. the frequency and the intensity of the microwave and its spatial gradient. L. pp. pp. Karode. Vol. L. 1959.. Roque. “Microwave Phase Conjugation Using Antenna Arrays”. Itoh. the density and the temperature of the plasmas. “A Full Duplex Capable Retrodirective Array System for High-Speed Beam Tracking and Pointing Applications”. K. IEEE Trans. Y.11. However. Wang. H. 2001. Fusco.5. 6.ee. pp. Qian. Panaretos. 1998. 2004. Both experiments were carried out in Japan with small rockets. “An active integrated retrodirective transponder for remote information retrieval-on-demand”. “Progress in Active Integrated Antennas and Their Applications”.1658-1662  Leong. R. Vol. MTT. S. R. F.3. MTT. G. Macfarlane. S. and S. Supercond. the assumption of collisionless plasma is not obvious. MTT. 2003..uk/hfe/st173. S. T. 1998.qub. “Mobile Digital Communications Using Phase 27 .11. G. Rebeiz.. IEEE Trans. IEEE Topical Conference on Wireless Communication Technology. and V. L.002. Peden.1891-1990  Brabetz. Hao and J. no. pp. and W. and G. Vol.565-568  http://www. Oct.. 2.. 2001. S.S. IEEE Trans.frequency in the ionosphere. Itoh. Y. Almost all studies are theoretical prediction and computer simulations. They showed this self-focusing effect will not occur with the SPS and ionopheric parameters.3. “A Microwave Phase Conjugating Antenna Using High Temperature Superconductors”. M. Hawaii. Shiroma.1910-1919  DiDomenico. F. R. D. Shiroma. J. MTT. IEEE Trans.46.A.1479-1489  Qian. MTT. U. I.. Y. No.1566–1569  Chang. and S.
M. Sep.5-10  Hatsuda. T. and N. 4. 2002. and P.. N. Hashimoto. Proc. Rodenbeck. 1987  Hashimoto. H. Shinohara. 2003  ICNIRP. K. Y. Shinohara. E. “A Frequency Autonomous Retrodirective Array Transponder”. Petersen. Space Power. of the 4th Int. S. 1998  Leong. “Guidelines for Limiting Exposure to Time-varying Electric. SPS2004-06(2005-01). Arndt. M. of 3rd SPS symposium. No. K. Akiba. “Frequency Problem for Microwave Power Transmission (in Japanese)”.  Osepchuk1. and K. pp. K. M. K. 9. J. on Solar Power from Space . 38-46  Tominaga. 1A/18-E. K. “Historical Review of RF Exposure Standards and the International Committee on Electromagnetic Safety (ICES)”. F.1&2. and USEF SSPS Study Team. and R. “Space Solar Power System Beam Control with Spread Spectrum Pilot Signals”. No. pp. Document No.311. Proc.11.1349-1352  Kaya. and R. pp. and Electromagnetic Fields (Up to 300 GHz). S. D. 2000. Jeon. Reference Question 210/1. G.1A/53-E. 494-522 28 . “Development of Retrodirective Control Transmitter for Wireless Power Transmission”.21-31. 31-37  Little. Shibata.. Magnetic. 1998. pp. Miyamoto. and H. No. “Some Proposals for the SSPS Actualization from Innovative Component Technology Standpoint”. 2004. Itoh. 2000  Present status of wireless power transmission toward space experiments (Question ITU-R 210/1).SPS ’04. C. The Radio Science Bulletin. Document No. Wang. 2002. E. T. Task Group ITU-R WPIA. ITU Radiocommunication Study Group. Mizuno. 2005.267 – 274  Mikami. H. “A Self-Steering Array and Its Applicationto Phase Synchronization of transmitter units and SSPS (in Japanese)”.. H. Satoh. 2004.. J. Bioelectromagnetics Supplement 6:S7-S16. S. The Radio Science Bulletin.. T. pp. T.. of URSI EMTS 2004. H.-S. Task Group ITU-R WPIA. pp. Matsumoto. Dec. of the IEEE Military Communications Conference (MILCOM '98). Proc. H. 2004. 1993.. N. H. Y. H. K.. “Solar power satellite interference assessment”. C. Oct. 2002 IEEE MTT-S Digest..4. M. IEEE Microwave Magazine. 30. Vol. Inoue.65-70  Matsumoto. K. Wiley-Interscience. Matsumoto. H. pp. No.311. paper9. Study Group. Nakada. Matsumoto. No. Proc. R. Tech. “Phase Synchronous System of Separated Units”. “Rocket Experiment METS Microwave Energy Transmission in Space”. Ueno. Report of IEICE. 2004. Ngo. Tsutsumi.. Chang.139-144  Hashimoto. Matsumoto. K.” Health Physics.74.. 3. pp.317-319  Lipsky. Conjugating Arrays”. Morishita. H. Ikematsu. Vol. pp.. pp. 2004  Applications and Characteristics of Wireless Power Transmission. Kokel. I. “Microwave passive direction finding”. Conf. and T.
and H. and H.. H. Shinohara. Vol. Information and Communication Engineers. “Engineering Aspect of the Microwave- Ionosphere Nonlinear Interaction Experiment (MINIX) with a Sounding Rocket”.8..89-103 29 .148. W. 1995. J.104-114  Matsumoto. Vol. “Nonlinear Interaction of strong microwave beam with the ionosphere: MINIX rocket experiment”. pp. Obayashi. Matsumoto. Concept Development and Evaluation Program".723-730  Perkins. Nagatomo and T.28. pp.23 – 29  Matsumoto. 1986. Part3. “Attenuation by Atmopheric Gases”. 1978  CCIR Report 721. Vol.. H. Roble. 1999.148. Vol. Hirata. New York  Bean. 1982. pp. Space Solar Power Review. N. 2004. N. p. Kimura. Itoh. and S. Miyatake.1611-1624  DOE and NASA report .100.78. And Rept. Electronics and Communications in Japan. “Effect of non-ionized air in high power microwave power transmission (in Japanese)”.107  Furuhama. pp.28. IEEE. and E.715-721  Hashimoto.9. Geophys. “Attenuation and Scattering by Precipitation and Other Atmopheric Particles”. G. H. Vol. Acta Astronautica. Electronics and Communications in Japan. pp. “Computer Simulation on Nonlinear interaction of Intense Microwaves with Space plasmas”.271. “Numerical estimation of SPS microwave impact on ionospheric environment”. H. Shinohara. B. 1979)  Matsumoto. Matsumoto.6. predictions for Arecibo and satellite power station". Vol.A4. pp. R. Space Solar Power Review. Hashino. p. Acta Astronautica. H. Vol. Hashino. 1982. Matsumoto. “Microwave Beam Control for Space Solar Power Satellite (in Japanese)”. SBC-1-12. J. No. “Effect of Ionized air in high power microwave power transmission (in Japanese)”. Proc. pp. Oct. Part3..78. 1986. “Theoretical analysis of nonlinear interaction of intense electromagnetic wave and plasma waves in the ionosphere”. H.. Kaya. Of CCIR. pp. of the Institute of Electronics. Kimura.11.. "Ionospheric heating by radio waves. 3 kHz to 300 GHz. and R. “Radio Meteorology”.. M. pp.187 –191  Kaya. Dutton. Y. 1966  CCIR Report 719. K. Yashiro. Reference System Report. 1995. and T.6.11.493-497  Matsumoto. No. N. Vol. Y. 1978 (Published Jan. N. “Nonlinear excitation of electron cyclotron waves by a monochromatic strong microwave: computer simulation analysis of the MINIX results”. No. 1978. Vol. NBS Monograph 92. p. Recomm. 1986. pp. I.181-186  Nagatomo.13. Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields. No. N. 1982. No. Ibid. M..83. Review of the Radio Research Laboratories. IEEE. Review of the Radio Research Laboratories.S23-S24  Matsuura. F. No. Res. Y. "Satellite Power System . H. S.
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The RF-DC conversion efficiency of the rectenna with a diode depends on the microwave power input intensity and the connected load. 31 .8GHz microwave input. or other hybrid rectifiers. coplanar patch. microstrip antenna-. which means the wave form is a full-wave rectified sine form. The world record of the RF-DC conversion efficiency among developed rectennas is approximately 90% at 4W input of 2. loop antenna. It has the optimum microwave power input intensity and the optimum load to achieve maximum efficiency. especially diode. there are some MPT applications with one small rectenna element such as RF-ID. The circuit. As a result.45 GHz microwave. New diode devices like SiC and GaN are expected to increase the efficiency. The rectennas with FET or HEMT appear in recent years. mainly determines the RF-DC conversion efficiency. past CRL) in Japan. Brown in 1960’s. When the power or load is not matched the optimum.45GHz or 5. The rectenna and its word were invented by W. The antenna of rectenna can be any type such as dipole-. Other rectennas in the world have approximately 70 – 90 % at 2. The rectenna can also take any type of rectifying circuit such as single shunt full-wave rectifier. On contrary. monopole. spiral antenna. C. full-wave bridge rectifier. The λ/4 distributed line and the capacitor allow only even harmonics to flow to the load. Especially for the SPS. Its operation can be explained theoretically by the same way of a F-class microwave amplifier. Recent Technologies and Researches of Wireless Power Transmission – Receivers and Rectifiers – Point-to-point MPT system needs a large receiving area with a rectenna array because one rectenna element receives and creates only a few W. operated without any power source. Yagi-Uda antenna. we need a huge rectenna site and a power network connected to the existing power networks on the ground. 100% of the received microwave power should be converted into DC power. and a capacitor inserted in parallel.1 Recent Technologies of Rectenna The word “rectenna” is composed of “rectifying circuit” and “antenna”.5. There are many researches of the rectenna elements (Fig.5.1). and Kyoto University in Japan. NICT(National Institute of Information and Communications Technology. The rectenna can receive and rectify a microwave power to DC. the wave form on the λ/4 distributed line has a π cycle. 5. The rectenna using the active devices is not passive element. Famous research groups of the rectenna are Texas A&M University in USA. The rectenna is passive element with a rectifying diode. It consists of a diode inserted to the circuit in parallel. a λ/4 distributed line. The single shunt full-wave rectifier is always used for the rectenna. Silicon Schottky barrier diodes were usually used for the previous rectennas. or even parabolic antenna. In an ideal situation.
(a) (b) (c) (d) (e) (f) (g) (h) Fig.1 Various Rectennas (a) Brown’s Rectenna (2.5.2GHz) the efficiency becomes quite low (Fig. If the input voltage to the diode is lower than the junction voltage or is higher than the breakdown voltage. The weak microwave will be transmitted from the experimental satellite 32 .5GHz) (h) University of Colorado’s Rectenna (8.5-12.45GHz) (b) Brown’s Thin-Film Rectenna (2.45GHz) (e) Texas A&M University’s Rectenna (35GHz)  (f) CRL’s Rectenna (5. As a result. major research topic in the rectenna is to research and develop new rectennas which are suitable for a weak-wave microwave.5. which can be used in experimental power satellites and RF-ID.45GHz) (c) Hokkaido University’s Rectenna (2. the RF-DC conversion efficiency drops with a lower or higher input than the optimum.8GHz) (g) Denso’s Rectenna for Microrobot (14-14. The weak-wave means in the "micro-watt" range. The RF-ID is the first commercial MPT system in the world. The diode has its own junction voltage and breakdown voltage.45GHz) (d) Kyoto University’s Rectenna (2. the diode does not show a rectifying characteristic. The characteristic is determined by the characteristic of the diode.2). In recent years.
mutual coupling and phase distribution are problems to solve. The other approach is to develop a new rectifying circuit to increase the efficiency at a weak microwave input-. One is to increase an antenna aperture under a weak microwave density. This is theoretical prediction. We have two approaches to increase the efficiency at the weak microwave input. Fig. they will not operate at their optimum power output and their combined power output will be less than that if operated independently. It was experimentally and theoretically reported that the total power decrease with series connection is more than that with parallel connection.1. We can apply this type of the rectenna for the commercial RF-ID. problem is different from that of the array antenna because the rectenna array is connected not in microwave phase but in DC phase. There is the optimum connection of the 33 .2 Typical characteristic of RF-DC conversion efficiency of rectenna  on LEO to the ground because microwave power and size of transmitting antenna on the experimental satellite will be limited by the capacity of the present launch rockets. 5. There are two problems for this approach. 5. For usual phased array antenna.2 Recent Technologies of Rectenna Array The rectenna will be used as an array for high power MPT because one rectenna element rectifies a few W only. It makes sharp directivity and it is only applied for the SPS satellite experiment and not for the RF-ID application.5. It is caused by characteristic of the RF-DC conversion efficiency of the rectenna elements shown in Fig. It was further confirmed with simulation and experiments that current equalization in series connection is worse than voltage equalization in parallel connection. When we connect two rectennas in series or in parallel. For the rectenna array.
Although there are many researches of rectenna elements as shown in references - and more .3).3 Large Rectenna Array Used for (a) G-to-G Experiment in Goldstone in 1975 . (b) G-to-G Experiment in Japan in 1994-95 . The SPS requires a rectenna array whose diameter of over km. 5. only a few rectenna arrays were developed and used for experiments (Fig.5. (c) fuel-free airship experiment in 1995 .rectenna array. (d) Experimental Equipment in Kyoto University  34 . The maximum rectenna array in the world (a) (b) (c) (d) Fig.
a region with symmetrically reversed (or decreasing to zero) static magnetic field and a collector with depressed potential as shown in Fig. The size was 3.7 m x 3. a microwave cavity with uniform transverse electric field in the gap of interaction. 5.is that used for a ground to ground experiment in Goldstone by JPL. The most studied cyclotron wave converter (CWC) comprises an electron gun.5 m2. NICT in present) in Japan and Kobe University in 1995.4 m x 7. The CWC is a microwave tube to rectify high power microwave directly into DC.4. we have to use Cyclotron Wave Converter (CWC) instead of the rectenna. There is a large gap between these arrays of a few meters in size and the SPS array of kilometers in diameter.2 m was developed for a ground to ground experiment conducted by Kyoto University.304 elements and whose size was 3.8 GHz. A rectenna array that had 2. These sizes are approximately 1mφ. Fig. in 1975 as shown in the section of MPT history. Research of larger scale rectenna arrays is required.54 m x 3. USA. the latter is transformed into additional energy of the longitudinal motion of the electron beam by reversed static magnetic field.4 Schematic Picture of Cyclotron Wave Converter 35 .3 Recent Technologies of Cyclotron Wave Converter If we would like to use a parabolic antenna as a MPT receiver. Microwave power of an external source is converted by this coupler into the energy of the electron beam rotation. and Kansai Electric Corporation in 1994. then extracted by decelerating electric field of the collector and appeared at the load-resistance of this collector. Another rectenna array with the size of 2.4 m was developed for MPT to fuel-free airship experiment with conducted by CRL (Communication Research Laboratory.45 GHz and 5.5.5. Kobe University.2 m = 24. Kyoto University has several types of rectenna arrays at 2.
The TORIY Corporation and Moscow State University collaborate to create a several high power CWC with the efficiency of 60-83% at 10-20 kW-. The grid is designed to take up the slack if the SPS dropouts without warning. Japan.5 CWCs Developed in Russia  5. Moreover. there is potential for trouble for the rectenna (power source to the grid).5. Most of the grid connection issues. Vanke’s group continue to improve the CWC in present. Jonson-. then output may cease. a variant of the CWC was tested and its efficiency was 70-74% at 25-25W. The technology for connection to the grid already exists.5 W input with 56% efficiency. If the lapse or power failure is too large.4 Rectenna Site Issue It is widely assumed that a commercially feasible SPS will be on the order of GW. and can contribute to any national power grid. it has possibility that accidents can occur at either the SPS side or the grid side. European group planed to apply the CWC for a ground-to-ground MPT experiment in Re-union Island. At Moscow State University. are the same. although the output of the SPS is a direct current. the DC power converter may be able to handle these lapses in most cases -. C. The first CWC experiment was carried out by D. C. If connected to a large existent grid. However.within a certain specified range of lapses. If an accident occurs on the grid side. They demonstrated the CWC at the WPT’95 conference in Kobe. It delivers significant electric power. In some cases the output of the rectenna may lapse. then the grid should be able to take up the slack. Fig. The grid 36 . some simulations concerning the connection with the rectennas and the existent power grid are carried out. When The SPS connect to existent power grid. The SPS will be steady state base power system without CO2 emission. The first CWC could rectify only 1-1. Its output is predictable. Grow. because they must first drive a kind of turbine-generators. Watson. somehow. a GW class power plant is similar to a nuclear power plant or large hydropower plant. The output of thermal or nuclear power plant is an AC. therefore. In Japan. and C. We have no problems economically and technologically with connecting the SPS to an existent power grid. W. R.
21. Proc.. Fujita. 6. 1979. Vol.14. 1996. T. No.144  Brown. C. Vol. Vol. 1994. Jan.. and K. pp. Idogaki. Electronics Letters.1072-1073  Yoo. Kaya. Vol. Chang. No.1. C. 76. No. N. Fujino. short enough for the SPS to manage with such hits to the grid. However. “Theoretical and Experimental Development of 10 and 35 GHz Rectenna”.. and T. Fujino. M. pp.. and T. 15-18. Vol. T. “Microwave Energy Transmission System for Microrobot”. IEEE Trans. pp. “The History of the Development of the Rectenna”. Y. 6.261-268  Shibata. 46. but the power failure duration should be very short. 1992. “A Dual Polarization Microwave Power Transmission System for Microwave propelled Airship Experiment”. IEICE Trans. Miura.2..313-320  Shinohara. MTT. 1986. pp. Of SPS’97.. J. Fujita. IEEE MTT-S Digest. Commun. W. “Experimental Study of Large Rectenna Array for Microwave Energy Trasnmission”. MTT. 1980. Journal of Microwave Power. pp. pp. and K. IEICE Trans.510  Alden A. “A Microwaver Powered. “Single Foreplane high Power Rectenna”. Vol. pp. Of SPS microwave systems workshop at JSC-NASA.507. pp. and N. 11.1508-1513  McSpadden. and M. W.657-661  Ito. No. No. T. pp.2. Matsumoto. Y. M.. “A Dual Polarized Circular Patch Rectifying Antenna at 2.. S. 1998..142.1749-1752  Fujino. Gworek. N. pp. Y. 1992. Proc. Vol. Kusaka.3. High Altitude Platform”. M. and R. IEEE Trans. 1993.4. R. 80-C. Ogihata. Y. “Yagi-Uda Receiving Elements in Microwave Power Transmission System Rectennas”. More careful studies are needed on this matter. N. Vol. Ishii. T. Proc. Kunimi.251-253  Shinohara. may be difficult for the SPS to cope with. No. and T. and H. pp. Electr. N. 40.393-396  Saka. B-II. Fujita.S International Microwave Symposium Digest. Long Duration. W. References  Brown. An Experiment of a C Band Rectenna”. a major accident at another power source (resulting output failure for hours or days). No. T. Matsumoto.S International Microwave Symposium Digest of Technical Papers. C. B. J. T. Otsuka.. Chang.86.1259-1266  Gutmann. Aoki. Kunimi. 1998. 1997. O. pp. Kaya. “Optimization of the Efficiency and Other Properties of the Rectenna Element”. MTT.271-280  Brown. Fujiwara. M. IEICE-Trans.12. “Open Experiment of Microwave Power Experiment with Automatically Target Chasing System (in Japanese)”.J81-B-II. 1997. No. Ohno. Hattori.. of ISAP’96.may be hit by electrical storms (thunder storms).45 GHz for Microwave Power Conversion and Detection”. No. MTT.303-308 37 . Vol. N. Ida.E-76-B. S. “Fundamental Experiment of a Rectenna Array for Microwave Power Reception”. pp. and S. Vol. H.1 1976.
Mikami. Fujimori. 2005. and H. H. Xue. and K. “A Rectangular Parabola Rectenna with Elliptical Beam for SPS Test Satellite Experiment (in Japanese)”. Electronics and Communications in Japan. “Design of a 5.. 2002.12. “A High Efficiency Rectenna Element using E-pHEMT Technology”. Appl. Okegawa. and S. of 12th GAAS Symposium. Santandrea. MTT. Chang. Rorrego. No.. pp. R. Strassner. and S. and H. IEEE-MTT. pp. Y.. A.. 2004. Popovic. pp. No. Essakhi. Akoun. Eur. J. Popovic and Z. Mediavilla.. and S.. 2004. SPS2004-07(2005-01). of the Institute of Electronics. Proc. “Monolithic and Hybrid Integrated ZB Converter Design”. Matsumoto. SBC-1-10. pp. P. Latrach. “Power Combining in an Array of Microwave Power Rectifiers”. No.261-268  Miura. 2005. Sanagi. J. “A Novel Low-Cost High-Conversion Efficiency Microwave Power Detector Using GaAs FET”. 84. García. pp.2. Tazón.46.11-14. T. .2001. Nogi. 2004. No. H. J. C. and J. pp. “An e. G. Phys. IEEE Trans.27-36 38 . Part 2. Chan. and I. A. Proc. L. Yamamoto. B. B. Matsumoto. M. and A. A. Tech. D. Pichon.958-968  Zibitou. C. Vol. 2000. and K.. Chang. H. 1998. M. N. Ogimura. EuMC_JHnlBP_00. and C. K. Proc.S29-S20  Suh. A. Report of IEICE..1870-1876  Leroy.3. Latrach. Information and Communication Engineers. 2005. MTT. “Development of High Efficiency Rectenna at mW input (in Japanese)”. 2004. Lopez. pp.175-178  Hagerty. of 4th International Conference on Solar Power from Space (SPS’04).315-318  Gutmann.29-31  Gómez. H.8-GHz Circularly Polarized Rectifying Antenna for Wireless Microwave Power Transmission”. “Wide Band Power Rectenna with High Sensitivity Detection”. Y. 50. 2005  Shinohara.8.111-116  Zibitou. Proc. Q. 2005  Tada. pp. pp. Phys. Ikematsu. IEEE Trans. and C. 4. K. pp. B. 44. Vol. Shinohara.15-20.” Experimental Study of Large Rectenna Array for Microwave Energy Transmission”. Toutain. N. of 4th International Conference on Solar Power from Space (SPS’04). pp. “Experimental Study of Rectenna Connection for Microwave Power Transmission”. 1.8-GHz Rectenna Incorporating a New Patch Antenna”. Guyot. Vol. J.MTT-27. “5. No. IEEE Antenna and Wireless Propagation Lett.251-255  Shinohara. J. SPS2004-08(2005-01). Microwave and Optical Tech. Matsumoto. Tech. Toutain. T.cient global analysis of a rectenna using the combination of a full-wave model and a rational approximation”. pp. pp. Vol. of 30th European Microwave Conference. M. H. M. Vol. Mizuno. L. “Characteristics of Microwave Rectification Circuit with Couple Line Structure (in Japanese). Lett. Proc. K.29. N. N. Vol.39-43  Chin.. Report of IEICE. H. 1979. and K.. J. “Broadband Rectenna Arrays for Randomly Polarized Incident Waves”.pdf  Fujino. H. No. Uematsu.
. Lopukhin. Institute of Electric Engineers Japan. C.3-3  Vanke. R. Savvin. E81-C. Savvin. K. p. P. “A Rectifier with Tranverse Interaction”. M.. in Microwave Power Engineering. Proc.1136-1142  Vanke.SPS ’04. Science and Technology Agency.1014  Vanke. 54. Matsumoto. R. and K. “Ground-based Receiving/Convertin System for Space Solar Power Systems”. A. pp. C. 2004. on Solar Power from Space . N. “Case study in Reunion island. C. Vol. p. V. pp. Jonson.131-138  Watson. Matsumoto. pp. A.1965  Watson. Shinohara. Jeanty. no. and A.116-B. pp. Digest.6. Dickinson. C. 1998. and G Pignolet. pp. V. Microwave Power. 1968. Bykovski.. N. 2003.. W. of WPT’95. D.. C. “Cyclotron Wave Converter of Microwave into DC”.7. M. and N. A. Vol. and V.5.. “A Cyclotron Wave Microwave Power Converter”. I. vol. 1995. Electron.. Sigorin. D. Savvin. Matsumoito. H. 1976. J. N. H. R. A. “On a Possibility to Decrease Magnetic Intensity in Microwave/DC Cyclotron Wave Converter”. No. T. Radiotechnique & Electronics. Grow. K. V. 253-258  Research and Study of SSPS (Space Solar Power System) (in Japanese).11. Jonson. No. Tabbot.7.388-GHz Receiving Array in Wireless Power Transmission over 1.515-520  Vanke. Microwave Symp. and C. L. Kita.1390-1392  Celeste. IEICE Trans. D. New York and London. No. A. No. L.. C. 1965. A. ed. “Development of Cyclotron Wave Converter”.72  Vanke. pp. Electron. Academic Press. Okress E. pp. V. 1982. E86-C. Grow. Proc..648-653  Matsumoto. A. IEEE. and C. V. N. C. V. and C. Hashimoto.27. Boudzinski. vol. 1970.54 km”. and T./MRI. H.. Shinohara.5.2. and H. W.139-141  Shimokura. Jonson. 1976 MTT-S Int. 2005 39 . of SPS’91. Vol. of the 4th Int. No. “Performance of a High-Power 2.408-419  Watson. Trans. and S. K. V. Acta Astronautica”. pp.. L. Proc. 1996. “Point-to-point microwave power transmission experiment (in Japanese)”. Vol. JAXA. 1991. “Cyclotron Wave Converter for SPS Ebergy Transmission System”. V.. p. V. Conf. 2004. Mitani. I.1. IEICE Trans. Proc. “A Cyclotron Wave Rectifier for S-band and X-band”. Vol. Shinohara. V. M. Rosnovsky. Kaya. Shinohara. p. “Experimental Equipments for Microwave Power Transmission in Kyoto University”..
and the separation distance between the two antennas as shown in the section 1. and RF-DC conversion efficiency. the rectenna aperture is 10x13 km. If we have enough large number of elements.2. 6.8GHz Rectenna Fig. grating lobes. This problem occurs in module-type phased array.6. The idea of random array has risen in order to suppress the grating 40 . The beam pattern on the ground is shown in Fig.24 cm (2. it is easier to keep high efficiency than that on the other two stages. it was calculated approximately 89% in the SPS reference system with the parameters as follows.1 RF-DC Conversion Efficiency The RF-DC conversion efficiency of the rectenna or the CWC is over 80 % of experimental results as shown in Fig. Decline of the efficiency is caused by phase/frequency/amplitude error on a phased array. and any losses on the systems. For example.000 km. the wavelength. trouble of the rectenna.6. beam collection efficiency which means ratio of all radiated power to collected power on a receiving antenna. the difference of the beam direction is negligible. The rise of the sidelobe decreases antenna gain and beam collection efficiency. whose power level is the same as main beam. Phase/frequency/amplitude error on a phased array causes difference of beam direction and rise of sidelobes.1 Efficiency of Rectenna Element 6. cables. DC/AC conversion. If antenna planes separate each other structurally. However. Efficiency We classify the MPT efficiency roughly into three stages. the transmitter aperture is 1 kmφ. and the distance between the SPS and the rectenna 36. 6. may occur and power can not be concentrated to the rectenna array.45GHz Rectenna (b) Efficiency of 5. They assume 10dB Gaussian power taper on the transmitting antenna. the wavelength is 12.45GHz). (a) Efficiency of 2. Decline of the efficiency is caused by array connection loss. change of optimum operation point of the rectenna array caused by change of connected load.1. DC-RF conversion efficiency which includes losses caused by beam forming. etc.2 Beam Collection Efficiency The beam collection efficiency depends on the transmitter and receiver aperture areas. for example.6.
the optimum and economical size of the transmitting phased array and microwave power are calculated as around a few Fig.3 DC-RF Conversion Efficiency If we do not have to steer a microwave beam electrically in a MPT. if we need to steer a microwave beam electrically without any grating lobes. Therefore.lobes.2 Beam Pattern on the Ground km and over a few GW. development of High Power Oscillator Phase-shifter? (Isolator) Antenna Multiple Power Phase-shifter? (Isolator) Antenna Divider Phase-shifter? (Isolator) Antenna Fig.6. Especially in the SPS system.6. In that case. Power in grating lobes diffuses not to a main lobe but to sidelobes. 6. However.3 Implementation of microwave transmission with a high power microwave oscillator and phase-shifters for high precision control of microwave beam direction to large angles without grating lobes 41 . we have to use phase shifters with high loss. It means that microwave power from one antenna element is much smaller than that from one microwave tube or high power (over a several tens watts) semiconductor amplifier. 6. beam collection efficiency decreases and have to search for special techniques. we have to fundamentally suppress the grating lobes for a MPT system.3) if microwave beam will be steered to directions of larger than 5 degrees without grating lobes. respectively. It also means that phase shifter have to be installed after the microwave generation/amplification (Fig. a sidelobe level increases. we can use a microwave transmitter with high DC-RF conversion efficiency over 70-80 % like microwave tubes. However.
J.low loss phase shifter is very important for construction of a phased array with high efficiency. “A High Conversion Efficiency 5. pp. 2003. 1994.6. Oct. Concept Development and Evaluation Program". 1978 (Published Jan. J. Reference System Report.38-7.393-403  Yamamoto. and H.C-2-105 42 . Chang.547-550  DOE and NASA report . 1979)  Skolnik. Artech House. It means that DC-RF conversion efficiency in the MPT system in Fig. W. 1980. the phase shifter problem will be solved if microwave beam will be steered to directions within 0.4 Implementation of microwave transmission with phase-shifters and low power amplifiers for high precision control of microwave beam direction without grating lobes References  Brown.271-280  McSpadden.. "Satellite Power System . the power loss of the phase shifter is over 4-6 dB. I. R. Proc. 1997. 2nd Ed.. L.8 GHz Rectenna”. Matsumoto. Another way to solve the phase shifter problem is use of low power amplifiers after the high loss phase shifters (Fig. pp. of SPS microwave systems workshop at JSC-NASA. M. Oscillator Low power Phase-shifter amplifier (Isolator) Antenna Multiple Low power Power Phase-shifter (Isolator) Antenna amplifier Divider Low power Phase-shifter amplifier (Isolator) Antenna Fig. However.4). pp. “Study of Phase Array with Phase Controlled Magnetrons (in Japanese)”.. 6.1 degree because the phase shifters do not need to be installed without grating lobes with large sub-array. of IEICE. pp. S. N. “Phased Array Antenna Handbook”. 1990.. “The History of the Development of the Rectenna”. IEEE MTT-S Digest. McGraw-Hill. O.43  Mailloux. Fun.4 is below 20% if we use over 70% efficiency high power oscillator/amplifier. and K. “Radar Handbook. Shinohara. C. In present. p.7.6. Proc..”.
To realize the commercial SPS. The problem in order to realize the SPS is high efficient phased array for the MPT. We have also achieved a phased array technologies with low efficiency. there are some research subjects to solve in order to decrease its cost.1). We have already achieved a point-to-point MPT in 1970’s (Fig. There are some methods to increase the efficiency of the MPT.1 History and Future of the MPT 43 . We can advance energy systems from RF-ID to the SPS. New semi-conductor device is expected for increasing the DC-RF and RF-DC conversion efficiency. One is a superconducting to reduce a loss in resistance. The SPS is the largest and most suitable MPT application. Summary The MPT is very old concept with newest technologies. The higher efficiency can suppress a cost of the SPS. we have to advance the MPT technologies.Advance for SSPS - End of 19th Century –Begining of 20th Century .7. The other is an achievement of higher accurate beam control to reduce a loss in beam focusing.6. End of 20th Century – 21st Century .Theoretical Possibility - Hertz After World War II .Demonstration . The SPS is future system. Highly Efficient Space Use Phased Array Brown Thermal and Structural Maxwell Design Glaser Completion of WPT on ground Tesla Wireless Power Transmission via Microwave Fig. Based on the MPT application on the ground.6.

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