Plasma Antennas in Mobile Antenna Systems Haleakala Research and Development, Inc.

Transcription

1 Plasma Antennas in Mobile Antenna Systems Haleakala Research and Development, Inc. Dr. Ted Anderson, CEO Mobile Antenna Systems

2 Haleakala R&D, Inc News Scientific American February 2008 issue on our plasma antenna technology. Page 22. Popular Mechanics article in July 2010 by David Hambling. Page

3 Plasma Antenna book by Dr. Ted Anderson Antennas/b/2130.aspx Theodore- Anderson/dp/ X/ref=sr_1_1?s=books &ie=utf8&qid= &sr=1-1 m=2&usri=plasma%2bantennas#customerrevi ews 3

4 Plasma Antenna book by Dr. Ted Anderson Plasma Antennas Theodore Anderson, Haleakala Research and Development, Inc. ISBN Copyright 2011 ISBN Copyright

5 Haleakala R&D, Inc. Peer Reviewed Journal Articles Published Alexeff, I, Anderson, T., Experimental and Theoretical Results with Plasma Antennas, IEEE Transactions on Plasma Science, Vol. 34, No.2, April 2006 and Anderson, T., Alexeff, I., Anderson, T., Alexeff, I, Plasma Frequency Selective Surfaces, IEEE Transactions on Plasma Science, Vol. 35, no. 2, p. 407, April 2007 Alexeff, I, Anderson, T., Recent Results of Plasma Antennas, Physics of Plasmas, 15, (2008) We have two more journal articles being processed for publication on our smart plasma antenna windowing and another on the lower thermal noise in plasma antennas 5

6 Summary of Key Points Core technical competencies & expertise of your organization. Applications for military and civilian antennas. Reconfigurable plasma antennas Reconfigurable plasma frequency selective surfaces Reconfigurable waveguides. Manufacturing & facility capabilities Facilities to build plasma antenna, plasma FSS, and plasma waveguides. Facilities to perform supporting experiments and computer modeling. 6

7 The Haleakala R&D, Inc. Commercial Smart Plasma Antenna Prototype 7

8 Tactical Capabilities Plasma Windowing Concept External Plasma Blanket Internal Omnidirectional metal or Plasma Antenna HF band for example A wideband internal antenna and multiple windows tuned to different frequencies would produce a multi-beam, multifreq device UHF band for example Low Density Plasma Windows Opened for Transmit or Receive 8

9 Our Commercial Prototype with Our Prototype Engineer Jeff Peck 9

10 Features of our Commercial Prototype It currently weights about 10 pounds. Some weight (but not much) will be added when we make the base rugged and surround the tubes with SynFoam to protect the tubes. Future iterations of the prototype can be made smaller. But nevertheless it is much smaller and lighter than large phased array antennas, and the performance is in many ways better. Even in the prototype stage, our prototype is relatively inexpensive for a steerable smart antenna. Manufacturing would significantly reduce the price. It can steer the antenna beam 360 degrees in milliseconds. Our future prototypes will steer in microseconds using Fabry-Perot-Etalon Effects. 10

11 Features of our Commercial Prototype It is intelligent and smart. It can find and lock on to a transmitter. In addition, one plasma window can lock on to a transmitter and a second plasma window can find a second transmitter. It can reconfigure from single lobe, to multilobe, to no lobe configurations. It can run on a 12 volt car battery. It can be mounted on a tank, a humvee, a surface ship, a sub, etc. conveniently. Other applications: last mile, Wi-Fi, base stations, etc. This commercial prototype will be packaged and made rugged by encasing it in SynFoam. SynFoam is a lightweight, heat resistant, and very strong material. SynFoam has an index of refraction of nearly one, making it invisible to RF waves. 11

12 Our Commercial Prototype 12

13 Our Commercial Prototype 13

14 Our Commercial Prototype Open plasma window indicator. Orange color represents magnitude of power transmitted or received through an open plasma window. 14

15 Our Commercial Prototype Open plasma window indicator. Orange color represents magnitude of power transmitted or received through an open plasma window. 15

16 Ruggedized Smart Plasma Antenna 16

17 A Meshed High-Speed Wireless Distribution Network Using our Smart Plasma Antennas 17

18 Multi-hop meshed wireless distribution network architecture. Refer to slide 17. Smart antennas typically use a multi-element-array antenna, and place the intelligent processing ( smarts ) in the signal processing aspects. The antenna hardware itself is a fairly simple structure consisting of omni-directional or directional elements arranged in a particular geometrical configuration. Smart plasma antennas may increase the degrees of freedom offered by the antenna hardware itself, so that the signal processing software can leverage it to achieve even more sophisticated capabilities (rejection or leverage of multi-path effects) while lowering overall system cost. In particular, consider the multi-hop meshed wireless distribution network architecture in the figure on the previous slide that connects a final-hop smart antenna to a base-station. For simplicity a fixed wireless network is depicted in the figure. Lampposts (or equivalent structures) could host a last-hop smart plasma antenna and also participate in a relaying function. The mobile or home user would reach the base-station after traversing several hops in this network. 18

19 Multi-hop meshed wireless distribution network architecture. Refer to slide 17. High-speed communication in this model becomes feasible when the home or mobile has a directional antenna and the last-hop has smart antennas with the associated signal processing capabilities. This is because of the spectrum reuse, focusing of energy, and multi-path fading rejection that leads to dramatically higher signal-tonoise ratios. The additional key is to design such smart antennas at low cost and small form factors. Moreover, if the front-end antenna hardware also allows sophisticated and tunable beam-forming capabilities, then it provides new degrees of freedom that can be leveraged by signalprocessing systems which control and interface to it. In fact, even with current simple multi-element-array antennas at both ends, the Lucent BLAST (Bell Labs Layered Space-Time) system has demonstrated tremendous spectral efficiency of 20 bits/hz! 19

20 Multi-hop meshed wireless distribution network architecture. Refer to slide 17. In wireless communications which employ smart antennas, the bases use signal processing techniques to virtually direct the antenna array gain lobes towards the direction of the desired signals, as well as directing the gain nulls towards the direction of interfering signals. Since wireless signals experience multipath scattering, the most prominent multipath signals can be used by a RAKE receiver to enhance the signal to interference and noise ratio (SINR) and thus improve the quality of the link. In such a setting, the base would use a training sequence to determine the direction of the desired multipath signals and direct the lobes of the antenna array towards them. The number of lobes which can be directed and the number of nulls depends on the number of antenna elements in the array. The beamwidth of each lobe depends on the distance between the elements. A higher number of antenna elements provide a higher number of lobes to capture several multipath, and thus improve the SINR (signal to interference and noise ratio). However, the increase in antenna elements also implies a higher computational cost, since the dimension of the problem increases with the number of antennas. 20

21 Figure on left: Smart Plasma Antenna lobes for peak hour service with many interfering signals or many reflecting surfaces. Figure on right: Smart Plasma Antenna lobes for low demand period or few reflecting surfaces. 21

22 Reconfigurable Beamwidth and Lobe Number. Refer to slide 21. The beamwidth of the antenna array lobes is chosen so as to minimize the gain towards interfering signals. The narrower the beamwidth, the more isolation is provided for the desired signal. However, we have another trade-off, since a narrow beamwidth requires longer training signals to secure the direction of the desired signal. An unreliable estimate of the desired signal direction with a narrow beam may result in severe attenuation of the desired signal, which defeats the purpose of the antenna array. 22

23 Reconfigurable Beamwidth and Lobe Number. Refer to slide 21 A smart plasma antenna can be developed that allows new degrees of freedom, and simulate the gains (distance, bandwidth, efficiency etc) achievable using outdoor fading and propagation models and advanced signal processing capabilities (e.g.: MIMO processing (Multiple-Input-Multiple-Output)). The challenge is to choose an array configuration, which provides adequate SINR, levels, while requiring a low computational cost. The utility of this arrangement can be seen in the on slide

24 Smart Plasma Antenna as a Base Station Antenna 24

25 Adaptive Directionality of Smart Plasma Antennas. Refer to slide 24 The adaptive directionality of the smart plasma antennas provides a plethora of advantages. The directivity of each smart plasma antenna beam minimizes the power levels broadcast which might interfere with adjacent users. In this sense, it provides a form of SDMA. The directivity of the smart plasma antenna also reduces the power levels that could be detected by unfriendly agents. The adaptive nature of the smart plasma antenna allows the beam to follow the user with a minimum of computation required, as well as to alter the beamwidth depending if the user is in an area of high user density or requiring greater stealth, where the beam can be made very narrow, or if the user is relatively isolated moving at a great speed, where the beam can be made wider. 25

26 Adaptive Directionality of Smart Plasma Antennas. Refer to slide 24 In order to further reduce the transmission power levels, thus conserving battery power and concealing the position of the users and nodes, a low spreading gain code can be applied to each user s signal. The low gain permits us to maintain a high data rate. The highly directional property of our smart antenna does not require a high gain for multiple access. A low tap Walsh code would be enough to permit very low transmission levels, and good protection for each user. In addition, automatic power control can be implemented to decrease the collective power transmission of the entire network. 26

27 Adaptive Directionality of Smart Plasma Antennas. Refer to slide 24 In a civilian setting, where goals are to provide low cost and flexibility, we can use the directivity of a smart antenna as a form of implementing SDMA. The figure on slide 24 shows an example of this. In this case, consider the angle of service for each user can be estimated by a pair of omni-directional antennas placed on the same tower. This setup allows the array of smart antennas to provide uninterrupted service to users without having to estimate the direction of service. The adaptive beamwidth can be adjusted to accommodate users who are in close proximity, providing protection from interference for each user. The variable number of beams from our smart antenna allows the base to service a variable number of users at diverse locations. This eliminates the need for a technician to install additional antennas or make changes when new users initiate service or when other users terminate service. 27

28 Our Smart Plasma Antennas on Humvees 28

29 Adaptive Directionality of Smart Plasma Antennas. Refer to slide 28. In a mobile setting, as in where our goals are to provide as much flexibility, mobility, stealth, and protection from jamming as possible, we tailor our design to meet these needs. We consider a wireless ad hoc network, where there are several nodes deployed which provide as a network backbone. An example are the humvees in slide 28. Each humvee is equipped with an array of plasma antennas, where each of our smart antennas can create a variable number of antenna gain lobes of adaptive beamwidth and direction. Each soldier has a low power omni-directional antenna which is served by the humvee which can offer the best signal to noise ratio and has the capacity to serve that user. 29

30 Adaptive Directionality of Smart Plasma Antennas. Refer to slide 28. The signal to noise ratio levels and directions of service can be determined by performing a 360 sweep by each of our smart antennas. In order to distinguish between users of a given sector, as well as lower power usage, a user spreading code can be applied to users of each sector. This setup provides mobility, since the periodic scanning performed by smart antennas allows all users as well as all ad hoc nodes to move about without loosing the network contact. Each user may be served by any node, which allows for additional flexibility. 30

31 GPS aided and GPS free positioning using plasma antennas. Routing methods rely on the position information of nodes of the network. In this section we explain how using smart plasma antennas can enhance the GPS aided positioning. A method that exploits pattern programmability of smart plasma antennas for GPS free positioning is given. 31

32 GPS aided and GPS free positioning using plasma antennas. GPS is a widely used positioning technology that allows few meters accuracy when it is used in the stand alone mode or even millimeter accuracy when it is used in the differential mode. To reach such accuracy many sources of position error should be estimated and/or eliminated. These sources of error are differential, receiver clock bias, satellite clock bias, ephemeris error, ionospheric delay, tropospheric delay, integer ambiguity (cycles), and multipath error. Among all these sources of error multipath is the only source that cannot be estimated and eliminated. 32

33 GPS aided and GPS free positioning using plasma antennas. The positioning technique in GPS algorithm is based on triangulation. It means that a receiver measures its distance from the four or more satellites and based on these measurement finds its location. Any path that is not line of sight does not reflect the true distance between the satellite and GPS receiver. To reduce the effect of multipath error, the GPS antennas are designed so that the multipath caused by the sea or ground are attenuated, but these antennas cannot eliminated the multipath caused by other objects such as buildings or hills. 33

34 GPS aided and GPS free positioning using plasma antennas. Smart plasma antennas may for the first time provide a practical programmable antenna pattern that can effectively eliminate all unwanted path and therefore, reduce multipath induced error significantly. The possibility exists that smart plasma antenna radiation patterns can be programmed so that each satellite in view is assigned a lobe in the pattern. To account for mobile receivers and satellite movement, a beam steering algorithm could adaptively point these beams towards the associated satellite. 34

35 The figure below shows how smart plasma antennas may be used to eliminate multipath in GPS aided positioning. GPS receiver with omnidirectional antenna GPS receiver with plasma antenna 35

36 GPS-free positioning using plasma antennas. Although the GPS provides acceptable accuracy when four or more satellites are in view, natural or man-made obstacles can block the satellite signals easily. Also the GPS signal is not available for positioning inside buildings. Even when a GPS signal is available it is not always possible to use this technology, because the communication unit may not have enough battery life to power up a GPS receiver or simply because it is not economically feasible to have a GPS receiver in the unit. For all these reasons GPS-free positioning is an important part of academic research, and an industrial challenge. A GPS-free positioning technique that uses a smart plasma antenna to estimate the Angle of Arrival AoA of the received signal and use that for position estimation. 36

37 GPS-free positioning using plasma antennas. Since the plasma tube can be activated and deactivated very quickly, the plasma antenna can be considered as a fast steerable directional antenna. The access point or a mobile node can obtain information about the location of another node by using the following method: It first sends a message starting from the first beam. Then it waits for the node in this direction to respond. Upon receiving the message, a node responds by sending back an acknowledgement. The first node then stores the beam direction of that node. After that or a timeout indicating there is no node residing in this direction, the antenna steers to the next beam, and likewise to cover the whole 360 degree. This steering/response method is used to acquire the spatial signature of each user. 37

38 GPS-free positioning using plasma antennas. The access point or mobile node sequentially steers the beam towards different directions, so that the entire space is covered. The objective of the localization protocol is to locate all users as fast as possible. So far we suppose acknowledgement in each directional beam is contention free. We need to consider the situation that there are more than one node in some directions. In this case, some back-off mechanism can be used. The same directional beam of first node may have to send the message multiple times to locate all the neighbors. The space is successively scanned by a beam until all the direction of neighbors are found and the procedure is repeated for all users equipped with plasma antennas. Once the network nodes have the AoA information, they can use it in position estimation. It is assumed that some nodes in the network have their position information before hand. These nodes are called anchor nodes. Now using the anchor nodes we explain how the other nodes in the network can locate themselves in the same coordinate system. 38

39 GPS-free positioning using plasma antennas. In the next figure we assume that node 1 and 2 are the anchor nodes. Using a smart plasma antenna, each node can estimate the angel of arrival alpha for i,j =1,,6. It is obvious that node 3 can find its position by just measuring the angle of arrival and knowing the position of nodes 1 and 2. Node 4 can use the position of node 3 and 1 and the angle of arrival to estimate its position. This process can be repeated for node 5 and 6 and other nodes if applicable. If nodes are capable of measuring their distance from one another we can use a mean square estimator to incorporate all information with the objective of minimizing the mean square of the error of the position. 39

40 GPS-free positioning using plasma antennas. 2 1 α 1,2 α 1,3 α 2,3 α α 2,1 3,1 α 3,

41 GPS-free positioning using plasma antennas. One important aspect of the smart plasma antennas is that the antenna pattern is programmable. Because we use plasma and not metal the side lobes may be reduced (however more research on sidelobe reduction using plasma antennas is needed), and by turning on and off the plasma tubes we can virtually make any complicated pattern on demand. This capability in directional antennas is unprecedented. In addition to this we can use signal processing algorithms to adaptively change the pattern so that the intended transmitter and the intended receiver can point their corresponding beams at each other to use the highest gain for data transmission. 41

42 GPS-free positioning using plasma antennas. This adaptive algorithm is specially important when the receiver and the transmitter are mobile. We call this the Beam/Pattern Tracking Algorithm. In the beam/pattern tracking algorithm the signal strength at each active beam is compared with its adjacent (inactive) beams. Once the signal strength in the adjacent beam is higher the driver changes the pattern so that the beam with higher signal strength is active. Using this algorithm the receiver and the transmitter can point their the antenna beam to multiple receiver/transmitters while tracking their movements. This algorithm is specially useful when line-of-sight between the transmitter and the receiver is available and is strong. This is the case for GPS receivers. In the GPS receivers we can use smart plasma antennas and the driver for our beam tracking algorithm to remove or significantly attenuate the multipath. 42

43 Conclusions on the Commercial Smart Plasma Antenna Prototype This is an intelligent, high performance steerable antenna with: Compact size Light weight Stealth and jam resistant Rugged packaging has been done We have potential manufacturing capability on our commercial prototype with: Impeccable Instruments, Inc. (CEO, Jeff Peck) in the Knoxville, TN area. Industrial Instruments, Inc. (CEO, Fred Dyer) in the Knoxville, TN area. Complete manufacturing can be done in USA. 43

44 Our SynFoam Housing for the Plasma Tubes. House the plasma tubes in strong and lightweight synthetic foam called Synfoam which can be molded into any shape we want. UDC SynFoam is a high performance syntactic foam combining high strength and low density with very low moisture absorption. SynFoam's syntactic foam products feature a density of less than 20 pcf and a compressive strength greater than 2000 psi. The index of diffraction of the Synfoam is nearly one so it is invisible to rf signals. See website: Synfoam Housing for our Plasma Tubes. We have cushioning foam to put around the tubes in this encapsulation. PLASMA CAN BE HOUSED IN SYNFOAM WITHOUT TUBES. We can mold Synfoam into any shape we want. We will make custom made rugged tubes as well. 44

45 Transmission and Reflection Properties The Concept of Cut-off and Filtering using Plasma Antennas The plasma frequency is proportional to the density of unbound electrons in the plasma or the amount of ionization in the plasma. The plasma frequency sometimes referred to a cutoff frequency is defined as: n where is the density of unbound electrons, e is the charge on the e ω = p 4πn e e me electron, and me is the mass of an electron If the incident EM frequency on the plasma is greater than the plasma frequency ω >ω p the EM radiation passes through the plasma and the plasma is transparent. 2 45

46 Transmission and Reflection Properties The Concept of Cut-off and Filtering using Plasma Antennas When ω < ω p the plasma acts as a metal, and transmits and receives microwave radiation. Note, the incident frequency in the next slide is given as: ν = ω 2π 46

47 Transmission and Reflection Properties We can surround our plasma antenna by a ring of plasma tubes that act as a reflector. If the plasma frequency in this ring is lower than that of the received signal, the signal passes on to the plasma antenna. However, only those frequencies that are lower than the plasma frequency in the plasma antenna will be received. All higher frequencies pass through both the ring of plasma tubes and the plasma antenna without interacting. Mathematically, we can state that υ ring p υ signal p p υ p antenna where the received signal is between the plasma frequency of the ring and the plasma frequency of the enclosed antenna. Since both the plasma frequency of the ring and the plasma frequency of the antenna can be reconfigured in milliseconds, the receiving notch can be moved about as desired 47

48 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity 48

49 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity A cluster of plasma antennas such that the diameter of the cluster is much less than a wave length can fit in a cell phone. The steerablity comes from being able to extinguish the plasma in any given number of plasma antennas in any time sequence in the cluster of plasma antennas. Once computerized this system becomes a smart plasma antenna which fits in a cell phone. 49

50 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity Ring of plasma antennas ( now all off) of diameter L with a plasma antenna in the center: L 50

51 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity All plasma antennas placed in cylindrical mold of synfoam. L 51

52 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity Two plasma antennas turned on at opposite sides out of phase + 52

53 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity θ θ L L E = E0 cos k( x cos θ ) E0 cos k( x + cos θ )

54 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity Assume that kl 2 < 1 The wavelength is large compared to the plasma antenna system of diameter L. The result is: E = E0(sin kx) klcosθ This is a two lobe radiation pattern, but directional. The two lobes of the plasma antenna are oscillating out of phase. 54

55 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity Three plasma antennas in a straight line Two outside antennas radiating in phase The center antenna radiating out of phase but with double the signal strength 55

56 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity The far field E field with the two plasma antennas radiating in phase and a plasma antenna with double the signal strength and oscillating out of phase is: L L E = E0[cosk ( x cosθ ) 2coskx+ cosk( x+ cosθ )]

57 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity Assume that The wavelength is large compared to the antenna diameter L. The result is: kl 2 < 1 E = E kl [ cos kx[( 2 cos 2 0 θ ) ] This is a two lobe plasma antenna with both lobes in phase 57

58 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity Three plasma antennas in a straight line. The two outside plasma antennas are radiating out of phase ( a dipole). + + The center antenna is oscillating in phase with one of the antennas in this case the one on the right ( a monopole). 58

59 Future Smart Cell Phone Antenna Application. Directional and Electronically Steerable Plasma Antenna System using a Cluster of Plasma Antennas in Close Vicinity The resulting radiation E field from the plasma dipole and monopole plasma antennas is: E = E [ 1 cos ] sinkx + θ 0 This is a one lobe directional radiation pattern which is un-attenuated in wavelength. 59

60 Lower Thermal Noise and Higher Data Rate Plasma Antennas than Corresponding Metal Antennas Higher Signal to Noise Ratio and Higher Data Rate Plasma Antennas over Corresponding Metal Antennas. 60

61 Thermal Noise in A Plasma Antenna Compared To a Metal Antenna The Nyquest Theorem [see reference below] states that the thermal noise generated in a resistor is: Equation [1] F ( T, R) = 2 π ktr K is Boltzmann s constant, T is the absolute temperature in degrees K The misconception is: Since T is higher in a plasma antenna obviously the noise in the plasma antenna is higher. This expression for the Nyquest Theorem is an approximation [ see reference below]. Reference: * Fundamentals of Statistical and Thermal Physics, F. Reif, McGraw-Hill, 1965, Section , pp

62 Thermal Noise in A Plasma Antenna Compared To a Metal Antenna Rigorous derivation of thermal noise shows that the approximate expression of the Nyquest Theorem becomes: Equation [2] H ( T, R, ω, ν ) = 2kTR 1 2 π ω 1+ 2 ν Where ν is the electron-atom collision frequency and f = ω 2π is the operating antenna frequency 62

63 Thermal Noise in A Plasma Antenna Compared To a Metal Antenna In the limit of very large collision frequency compared to the antenna operating frequency characteristic of a metal antenna:, equation [2] reduces to equation [1] characteristic of thermal noise in a metal: ν ν >> ω ν >> ω H ( T, R, ω, ν ) = 2kTR 1 π ω 1+ 2 ν 2 2kTR π 63

64 Thermal Noise in A Plasma Antenna Compared To a Metal Antenna The thermal noise of a plasma antenna decreases compared to a metal antenna as the frequency increases because: The thermal noise in a metal antenna is higher at higher operating frequencies because of the thin skin depth and corresponding higher electrical resistance. The thermal noise of the plasma antenna decreases as the operating frequency increases as seen in the power spectral density of thermal noise for the plasma antenna: H( T, R, ων, ) = 2kTR 1 2 π ω 1+ 2 ν 64

65 Thermal Noise in A Plasma Antenna Compared To a Metal Antenna Other factors which further lower thermal noise in a plasma antenna: Ramsauer -Townsend Effect is an effect in which the cross section of electron atom scattering is minimal. This effect is energy dependent and our plasma antennas operate in the energy region of the Ramsauer- Townsend Effect. The Ramsauer Townsend Effect means that the collision frequency ν is small and is minimal This means even less noise thermal noise in the plasma antenna as equation [2] becomes smaller. Operating the plasma antenna in the afterglow state may further reduce thermal noise 65

66 Thermal Noise in A Plasma Antenna Compared To a Metal Antenna With the Ramsauer- Townsend Effect and operation in the afterglow state will broaden the frequency range in which plasma antennas have less thermal noise than metal antennas. Thermal noise in a plasma antenna can further be reduced by reducing plasma pressure, plasma temperature, and plasma resistance. 66

67 Higher Gain with Plasma Antennas? Lower side lobes in a plasma antenna Soft surface effects of plasma Lower thermal noise Higher data rates for plasma antenna system pointed in space. Plasma lens effects Beam focusing with plasma lens 67

68 Physics of Reflection and Transmission of Electromagnetic Waves through Plasma 68

69 Physics of Reflection and Transmission of Electromagnetic Waves through Plasma An electromagnetic wave from an antenna of frequency ω is incident on a plasma with a plasma frequency ω p The plasma frequency is proportional to the square root of the density of unbound electrons in the plasma or the amount of ionization in the plasma. 69

70 Physics of Reflection and Transmission of Electromagnetic Waves through Plasma The plasma frequency is defined as ω = p 4π n e me e 2 ne is the density of unbound electrons, e is the charge on the electron me is the mass of an electron 70

71 Physics of Reflection and Transmission of Electromagnetic Waves through Plasma If the incident antenna frequency on the plasma is much greater than the plasma frequency ω p Such that ω >ω p the antenna radiation passes through the plasma un-attenuated 71

72 Stacked Plasma Antenna Arrays 72

73 Stacked Plasma Antenna Arrays Metal antenna arrays cannot be stacked Metal from one layer blocks radiation of another layer Plasma density from higher frequency antenna arrays is higher than the plasma density from the lower frequency arrays Higher frequency plasma antenna arrays emit high enough frequencies to propagate through the lower frequency plasma antenna arrays 73

74 Stacked Plasma Antenna Arrays When antenna frequency from the ith plasma antenna layer exceeds the plasma frequency from the ith +1 layer the antenna radiation from the ith layer passes through the ith+1 layer Antenna radiation from ith+1 plasma antenna array layer through ith+2 plasma antenna array layer Antenna radiation from ith+n-1 plasma antenna array layer passes through ith+n plasma antenna array layer This goes on until all the plasma antenna array layers are transmitting independently in free space 74

75 Stacked Plasma Antenna Arrays Higher frequency antenna radiation from higher frequency arrays propagate through lower frequency arrays Bandwidths add Power adds Compactness Stacked arrays occupy less space than metal arrays Stacked arrays have smaller RCS Less EMI 75

76 Impedance matching of stacked plasma antenna arrays Each plasma antenna array is tuned to have a narrow band frequency Reduces problem of impedance mismatching that broad band antennas have The bandwidths of each layer of a plasma antenna array adds flexible bandwidth reduced impedance mismatching 76

77 Stacked Plasma Antenna Arrays 77

78 Advantages of Stacking Plasma Antenna Arrays Plasma antenna arrays stacked produces greater Bandwidths Multiband widths Turn any number of plasma arrays on or off power But less physical space helps reduce antenna farm on surface ships RCS 78

79 Nested Plasma Antennas 79

80 Nested Plasma Antennas Higher frequency nested plasma antennas emit higher frequencies which propagate through lower frequency nested plasma antennas Bandwidths add Large bandwidths Multiband widths Turn any number or sequence of nested plasma antennas off or on. Power adds Nesting antennas means compactness Maintains impedance matching Each nested plasma antenna is narrow band but adds up to wide band 80

81 Nested Plasma Antennas Results Antenna that is Compact Wideband Multiband High power Impedance matched Reconfigurable Various radiation patterns including isotopic Low RCS 81

82 Nested Plasma Antennas Example of Concept: Higher Frequency Dipole Plasma Antenna Nested inside Lower Frequency Plasma Helical Antenna and Transmission is Simultaneous with Radiation Patterns, Bandwidths, and Power Adding. 82

83 Nested Plasma Antenna: Concept of High Frequency Plasma Antennas Transmitting And Receiving Through Low Frequency Plasma Antennas Top View Low frequency plasma antenna Side View Medium frequency plasma antenna High frequency Plasma antenna 83

84 Nested Plasma Antennas Higher frequency plasma antennas are nested inside lower frequency plasma antennas Geometric compatibility Higher frequency plasma antennas are smaller Lower frequency plasma antennas are larger Higher frequency plasma antennas fit inside lower frequency plasma antennas 84

85 Nested Plasma Antennas with Plasma Windowing Inner antenna is omnidirectional Omnidirectional in azimuth direction when mounted on the aircraft Use existing broadband COTS antenna such as a COTS biconical Higher iterations would use nested plasma antennas Surround inner omnidirectional antenna with plasma windows 85

86 Tactical Capabilities Plasma Windowing Concept with Plasma Antenna Nesting External Plasma Blanket HF band for example Internal Omnidirectional Nested Plasma Antenna A wideband internal antenna and multiple windows tuned to different frequencies would produce a multi-beam, multifreq device Low Density Plasma Windows Opened for Transmit or Receive UHF band For example 86

87 Satellite Plasma Antennas 87

88 Plasma Antenna Advantages over Metal Antennas as Satellite Antennas Plasma antennas have much less thermal noise than metal antennas at satellite frequencies. Plasma antennas have higher data rates than corresponding metal antennas at satellite frequencies Plasma antennas are reconfigurable and metal antennas are not. An arrangement of plasma antennas can be flat and effectively parabolic. Better for antenna aesthetics. An arrangement of plasma antennas can electronically focus and steer RF signals without phased arrays. Applications for both static (e.g. Direct TV) and dish antennas attached to vehicles, ships, or aircraft. 88

89 Non-Steerable but Reconfigurable Plasma Reflector Antenna 89

90 Plasma Reflector Antenna: Right plasma reflector antenna installed in an electrical anechoic chamber Left - metal reflector antenna designed to be an identical twin to the plasma antenna The microwaves are generated by a line antenna, focused in one dimension by the metal pillbox, and focused in the second dimension by either the plasma antenna or a metal twin 90

91 Non-Steerable but Reconfigurable Plasma Reflector Antenna Radiation Pattern Previous Slide 91

92 Non-Steerable but Reconfigurable Plasma Reflector Antenna. Reduced sidelobes Azimuthal Radiation Pattern Relative Power (db) Reduced sidelobe levels for plasma antenna 92

93 Conclusions on Non-Steerable but Reconfigurable Plasma Reflector Antenna The main lobe plasma reflector antenna is identical to the main lobe of the corresponding metal reflector antenna. When the plasma antenna is turned off it is invisible to all RF frequencies. The plasma reflector antenna can operate at lower frequencies and be stealth at high frequencies. higher frequency RF waves will pass through a lower density plasma. The side lobes of the plasma reflector antenna are less than theside lobes of the corresponding metal reflector antenna. Soft surface effects of plasma 93

94 An Electronically Steerable and Focusing Plasma Reflector Antenna New Work on Plasma Reflector Antennas. 94

95 Some Physics of Plasma Transparency and Reflection The plasma frequency is proportional to the density of unbound electrons in the plasma or the amount of ionization in the plasma. The plasma frequency sometimes referred to a cutoff frequency is defined as: ω = p 4πn e e me 2 where n e is the density of unbound electrons, e is the charge on the electron, and me is the mass of an electron If the incident RF frequency on the plasma is greater than the plasma frequency the EM radiation passes through the plasma and the plasma is transparent. ω > ω p When the opposite is true, plasma acts as a metal, and transmits and receives microwave radiation. 95

96 An Electronically Steerable and Focusing Plasma Reflector Antenna A plasma layer can reflect microwaves. A plane surface of plasma can steer and focus a microwave beam on a time scale of milliseconds. Definition of cutoff: the displacement current and the electron current cancel when electromagnetic waves impinge on a plasma surface. The electromagnetic waves are cutoff from penetrating the plasma The basic observation is that a layer of plasma beyond microwave cutoff reflects: microwaves with a phase shift that depends on plasma density. 96

97 An Electronically Steerable and Focusing Plasma Reflector Antenna Exactly at cutoff, the displacement current and the electron current cancel Therefore there is a antinode at the plasma surface, and the electric field reflects in phase. As the plasma density increases from cutoff the reflected field increasingly reflects out of phase. Hence the reflected electromagnetic wave is phase shifted depending on the plasma density. This is similar to the effects of phased array antennas with electronic steering except that the phase shifting and hence steering and focusing comes from varying the density of the plasma from one tube to the next and phase shifters used in phased array technology is not involved. 97

98 An Electronically Steerable and Focusing Plasma Reflector Antenna This allows us to use a layer of plasma tubes to reflect microwaves. By varying the plasma density in each tube, the phase of the reflected signal from each tube can be altered. so the reflected signal can be steered and focused in analogy to what occurs in a phased array antenna. The steering and focusing of the mirror can occur on a time scale of milliseconds. 98

99 Schematic for an Electronically Steerable and Focusing Plasma Reflector Antenna Input Microwaves Plasma Tubes Reflected and Focused Microwaves 99

100 Basic Plasma Satellite( other frequencies apply) Reflector Antenna Design with Two Banks of Perpendicular Plasma Tubes for Steering and/or focusing in Two Dimensions. This system can apply to both a moving or static surface and steer and/or focus satellite signals by varying the plasma density among the plasma tubes with computer control in space and/or time. Plasma satellite (other frequencies apply) antenna can be flush with a wall, roof, or any static or moving surface which can be flat or curved. Receiving or transmitting Plasma or Metal Horn Antenna Carrying Signal to TV, etc. This system eliminates the parabolic dish Tubes can be within a wavelength apart. Such a wavelength corresponds to the transmitted or received frequency. This system can be completely encapsulated in Synfoam of an aesthetical shape. Plasma in tubes into the page steer and/or focus satellite signals in the z direction. Plasma in tubes parallel to the page steer and/or focus satellite signals azimuthally. One dimensional ( with one bank of tubes) steering and/or focusing may be enough for the static satellite plasma antenna. 100

101 Banks of tubes containing plasma displaced and perpendicular to each other Plasma satellite (other frequencies apply) antenna can be flush with a wall, roof, or any static or moving surface which can be flat or curved. They can also be mounted in other ways On the left a band of tubes containing plasma reflects EM waves and steers and focuses the beam in one direction. On the right a perpendicular bank of tubes containing plasma reflects and steers and focuses the EM waves in the perpendicular direction. A horn antenna in the lower right transmits or receives the EM waves. The banks of tubes containing plasma can be flush with a surface or supported in other ways 101

102 Steering and Focusing when the Plasma Density is Below Cutoff. Steering and focusing can also be achieved when the Plasma Density is below cutoff. An effective Snells Law causes refraction of electromagnetic waves passing through a plasma of variable density ( plasma density varying from container to container containing plasma ) The speed of electromagnetic waves in a plasma is a function of plasma density. 102

103 Steering and Focusing when the Plasma Density is Below Cutoff. Incident RF waves on the left impinge on plasma tubes with different densities but with the plasma densities below cutoff. Focusing or steeringcan be achieved depending on how the plasma densities are varied from tube to tube. Focused and/or steered Microwaves 103

104 Basic Plasma Satellite (works at other frequencies) Antenna Design with Two Banks of Perpendicular Plasma Tubes for Steering and/or focusing in Two Dimensions. This system can apply to both a moving or static surface and steer and/or focus satellite signals by varying the plasma density among the plasma tubes with computer control in space and/or time. Plasma satellite ( works at other frequencies) antenna is mounted between the received or transmitted antenna signals in which the two banks of tubes with plasma with variable density from one tube to the next to steer and focus the antenna beam. Receiving or Transmitting Plasma or Metal Horn Antenna Carrying Signal to TV, etc. This system eliminates the parabolic dish. Tubes can be within a wavelength apart. Such a wavelength corresponds to the transmitted or received frequency. This system can be completely encapsulated in Synfoam of an aesthetical shape. Plasma in tubes into the page steer and/or focus satellite signals in the z direction. Plasma in tubes parallel to the page steer and/or focus satellite signals azimuthally. One dimensional ( with one bank of tubes) steering and/or focusing may be enough for the static satellite plasma antenna. 104

105 Conclusions An electronically steerable and focusing plasma reflector antenna can be made by having plasma densities in the tubes above cutoff but with the plasma densities varying from tube to tube. An electronically steerable and focusing bank of plasma tubes can be made by having plasma densities in the tubes below cutoff but with the plasma densities varying from tube to tube. Electronic steering and focusing in either of the above cases can be made in two dimensions by having two perpendicular banks of tubes. This can also steer and focus horizontal, vertical, circular, and elliptically polarized signals. 105

106 Conclusions (continued) With plasma electronic steering and focusing: parabolic reflector antennas are not needed. is in many ways a superior alternative to electronic steering with phased arrays. At satellite frequencies the plasma antenna has much less thermal noise than metal antennas The plasma antenna can provide better performance satellite communications antennas than metal antennas. 106

107 Some Recent Basic Research Findings 107

108 We have demonstrated that plasma windows can open in microseconds. 1. If a closed ring of plasma tubes is excited by a signal with a wavelength comparable to the ring size, remarkable resonance effects can be observed. 2. At high plasma density, the radiation is transmitted through plasma tubes with a plasma density above CUT-OFF. 3. At intermediate density the radiation is CUT-OFF. 4. As the plasma density decays, the transmission rises to normal. 5. Such effects are only observed with a closed plasma ring. 6. These effects may be of great value in future applications. 108

109 We have demonstrated that plasma tubes intercept microwaves regardless of polarization. We have been designing a plasma shield intended to protect sensitive microwave equipment from intense electronic warfare signals. A layer of plasma tubes is used as a microwave reflector. The plasma tubes work extremely well in intercepting microwave radiation when the incident wave electric field is parallel to the tubes. However, if the electric field is perpendicular to the tubes, the normally induced plasma current cannot flow, and the plasma effects are not expected to appear. To our surprise, when the plasma tubes were experimentally tested with the electric field perpendicular to the tubes, the plasma tubes not only intercepted the microwave signal, but the observed cut-off with a pulsed plasma lasted about twice as long. 109

110 Summary on Recent Basic Research We have demonstrated that plasma windows can open in microseconds. We have demonstrated that plasma tubes intercept microwaves regardless of polarization. 110

111 Target Markets Smart TV plasma antennas to meet the change over into digital airwaves. Dave Wilson, senior director of Consumer Electronics Association, saw our smart plasma antenna prototype work at the Austin antenna conference in September and believes we should have a market in the smart TV antenna market. We have looked at other smart antennas that address this area and we are convinced that ours is superior. GE and RCA have put commercial civilian smart antennas on the market recently to address the 2009 changeover to digital airwaves. Our smart plasma antenna capabilities are superior in many was to the other smart TV antennas. Our smart plasma antenna can steer the antenna beam 360 degrees and the competition cannot. Our smart plasma antenna has a reconfigurable beamwidth. The competition does not. Our smart plasma antenna has higher bandwidth than the bandwidths of the competition. We give some information on the smart TV antennas from GE and Audiovox taken from their websites in the competition section below. 111

112 Target Markets GE and Audiovox Smart TV Antennas See: Digital_Antenna.html and AEC/release_AEC_ html 112

113 Target Markets Smart plasma antennas as RFID readers We have determined advantages that the smart plasma antenna can have over other RFID antennas based on smart phased array technology. These advantages that our smart plasma antenna can have over smart phased array antennas for RFID applications are:. Our smart plasma antenna has the ability to steer (scan) antenna beams 360 degrees in milliseconds. We are aware of how to do it in microseconds. Competition cannot steer 360 degrees. Our smart plasma antenna beam can change direction without scanning in milliseconds. For example: from 0 to 180 degrees in milliseconds Reconfigurable beamwidth.. Broader bandwidth than phased arrays by using broadband omnidirectional antenna in the center such as a biconical antenna. In addition, bandwidth can be reconfigured for use in US, Europe, etc. Competition cannot do this. 113

114 Target Markets Smart plasma antennas as RFID readers Possible Less costs than phased array RFID antennas. We only need one antenna and we do not need phase shifters. Competition uses phased array RFID readers. Our smart plasma antenna is more compact and less cumbersome than phased array RFID antennas. Our smart plasma antenna is light weight: weighs about 10 pounds. Competition uses phased array RFID readers which are much heavier and larger. Our smart plasma antenna can read vertical horizontal, and circular polarizations by reconfiguration of plasma antennas. Competition cannot do this. 114

115 Target Markets Superior fixed satellite plasma antenna Satellite plasma antennas for RVs and yachts. The current markets for smart antennas for WIMAX, 4G, Wi-Fi, Blue Tooth. West, Kirsten; Principal Analyst, West Technology Research, Smart Antenna Technology Review, Antenna Systems & Technology, 2008 Resource Guide, pages 4 and

116 Target Markets Smart plasma antennas to replace omni directional wireless access point antennas in big box stores such as Walmart, CVS, Home Depot, Lowes, Best Buy, etc. These stores utilized sometime 6-30 Omni directional wireless access point also known as AP s. The AP s are extremely inefficient and have a high total cost of ownership with data security standard such as PCI compliance mandating encryption key rotation every 6 months. Major tier one retails utilize wireless infrastructure to drive business initiatives such as markdown, inventory, and price lookup. The big box stores such as Walmart, CVS, Home Depot, Lowes, Best Buy etc. utilized sometime 6-30 Omni directional wireless access point also known as AP s. The AP s are extremely inefficient and have a high total cost of ownership with data security standard such as PCI compliance mandating encryption key rotation every 6 months. 116