Abstract:
The present invention generally relates to an electromagnetic field vector sensing receive antenna array system for installation and deployment on a structure. A multipolarized array of collocated antenna elements is used to provide calibrated amplitude and phase radiation patterns with monopole, dipole, and loop modes generated from crossed loops connected to a be informer. The invention has applications for installation and deployment on a tower, balloon, or satellite for radio frequency sensing and location of low-frequency galactic emissions. The novel receive antenna array system comprises a multipolarized vector sensor antenna array. The disclosed direction-finding vector sensor can be installed and deployed on a structure and can detect and locate radio frequency emissions from galactic sources. The key system components of the receive antenna array system consist of deployable antennas, receivers, signal processing computer, and communications link.

Description:
[0001]    This application claims priority of U.S. Provisional Patent Application Ser. No. 62/243,343, filed Oct. 19, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
     
    
       [0002]    This invention was made with government support under Grant No. FA8721-05-C-0002 awarded by the U.S. Air. Force. The government has certain rights in the invention. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    It is well known that mapping of radio frequency galactic noise-like sources can be determined by ground based large diameter antenna array measurements for frequencies above about 25 MHz. Due to the total electron content of the ionosphere, radio frequency sources radiating below about 25 MHz are partially or almost completely reflected by the ionosphere. Therefore, the electromagnetic waves from galactic radio frequency sources are partially or almost completely blocked by the earth&#39;s ionosphere up to an altitude of about 300 km. Terrestrial radio frequency emissions are a significant source of interference for ground-based low-frequency mapping sensors. The natural radio frequency shielding provided by the ionosphere reduces terrestrial interference that would be received by a low-frequency satellite sensor orbiting above the ionosphere. Thus, mapping of galactic RF sources below 25 MHz can best be accomplished from a spacecraft above 300 km altitude. Multipolarized vector sensor antenna systems are being explored for a variety of direction finding applications and these sensors, when deployed in orbit above the ionosphere, are an alternate approach to mapping galactic sources. 
         [0004]    Curved thin shells, often called tapes, have been used to deploy structures and antenna in space for some time. They are used in many antenna concepts because they roll up or fold very compactly and after they deploy, they provide structural stiffness. In particular, metal tapes are often used as monopole antennas on cubesats. Common metal carpenters tapes are well suited for cubesat antennas because they are conductive metal and are very inexpensive. 
         [0005]    It would be beneficial if there were a system which can be deployed in a tower, balloon, or satellite for radio frequency sensing and location of low frequency galactic emissions. Further, it would be advantageous if this system could be stowed during launch and deploy while in orbit. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention generally relates to an electromagnetic field vector sensing receive antenna array system for installation and deployment on a structure. A multipolarized array of collocated antenna elements is used to provide calibrated amplitude and phase radiation patterns with monopole, dipole, and loop modes generated from crossed loops connected to a beamformer. The invention has applications for installation and deployment on a tower, balloon, or satellite for radio frequency sensing and location of low-frequency galactic emissions. 
         [0007]    More specifically, the novel receive antenna array system comprises a multipolarized vector sensor antenna array. The disclosed direction-finding vector sensor can be installed and deployed on a structure and can detect and locate radio frequency emissions from galactic sources. The key system components of the receive antenna array system consist of deployable antennas, receivers, signal processing computer, and communications link. 
         [0008]    There are multiple unique aspects of the invention. One is the approach to generating the loop and dipole modes from a mix of dual mode elements and a multiple feedpoint air loop. A second unique aspect is that the antenna is stowed during launch and then deployed once in orbit. The vector sensor antenna system disclosed here can also be installed on a tower or balloon and used to map radio sources at frequencies above about 25 MHz where the ionospheric shielding is reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    For a better understanding of the present disclosure, reference is made to the accompanying drawings, in which like elements are referenced with like numerals, and in which: 
           [0010]      FIG. 1  is a schematic diagram showing the key components of the direction finding RF vector sensor system including deployable antennas, receivers, signal processing and a communications link. 
           [0011]      FIG. 2  is a pictorial view of a generally polarized electromagnetic wave from a galactic radio frequency source incident on three orthogonal loop antennas and three orthogonal dipole antennas. 
           [0012]      FIG. 3  is a pictorial view of a vector sensor half-loop antenna deployed on the side of an electrically conducting housing. 
           [0013]      FIG. 4A-4B  are pictorial views of vector sensor antennas operating with monopole mode ( FIG. 4A ) and loop mode ( FIG. 4B ) deployed on the side of an electrically conducting housing. The arrows represent current flow. 
           [0014]      FIG. 5  is a pictorial view of a vector sensor full-loop antenna deployed on opposite sides of an electrically conducting housing. 
           [0015]      FIG. 6  is a pictorial view of a vector sensor full-loop antenna operating in a dipole mode. The arrows represent current flow. 
           [0016]      FIG. 7  is a pictorial view of a vector sensor full-loop antenna operating in a loop mode. The arrows represent current flow. 
           [0017]      FIG. 8  is a pictorial view of a monopole vector sensor antenna deployed on the end of an electrically conducting housing. 
           [0018]      FIG. 9  is a pictorial view of a vector sensing horizontal antenna surrounding an electrically conducting housing. 
           [0019]      FIG. 10  is a schematic diagram of a full six-mode vector sensor antenna system with feedlines for a horizontal loop mode. 
           [0020]      FIG. 11  is an enlarged view of the housing showing the connection ports for one of the full loop antennas. 
           [0021]      FIG. 12  shows electromagnetic simulations of the electric and magnetic field radiation patterns for the six vector sensor modes which include two crossed dipoles, two crossed loops, a vertical monopole, and a horizontal loop. 
           [0022]      FIG. 13  is the simulated input impedance for the vector sensor dipole mode. 
           [0023]      FIG. 14  is the simulated input impedance for the vector sensor vertical loop mode. 
           [0024]      FIG. 15  is the simulated input impedance for the vector sensor vertical monopole mode. 
           [0025]      FIG. 16  is the simulated input impedance for the vector sensor horizontal loop mode. 
           [0026]      FIG. 17  shows the simulated mismatch loss relative to a 50-ohm system for the vector sensor modes. The upper left graph shows x and y dipole modes. The upper right graph shows x and y loop modes. The lower left graph shows monopole mode. The lower right graph shows horizontal loop mode. 
           [0027]      FIG. 18  shows simulated current distributions for the dipole and loop modes. 
           [0028]      FIG. 19  shows simulated current distributions for the monopole and horizontal loop modes. 
           [0029]      FIG. 20  is a schematic diagram of a vector sensor antenna beamformer in which sum and difference hybrid magic tee components are used to generate dipole and loop modes, and a four-way combiner is used to generate the horizontal loop mode. 
           [0030]      FIG. 21  is a schematic diagram of a vector sensor antenna beamformer in which sum and difference hybrid magic tee components are used to generate dipole and loop modes, and a four-way combiner is used to generate the horizontal loop mode. Compared to  FIG. 20 , baluns are used to provide a balanced input from the four loop ports. 
           [0031]      FIG. 22  is a schematic diagram of a vector sensor antenna beamformer in which the sum port of a hybrid magic tee component generates dipole mode current flow. 
           [0032]      FIG. 23  is a schematic diagram of a vector sensor antenna beamformer in which the difference port of a hybrid magic tee component generates loop mode current flow. 
           [0033]      FIG. 24  is a schematic diagram of a hybrid magic tee device showing the electrical phasing of the RF ports. 
           [0034]      FIG. 25  shows a prototype vector sensor antenna and the measured reflection coefficients for loop, dipole and monopole modes. 
           [0035]      FIGS. 26A-B  shows a conceptual deployment mechanism for the vector sensor antennas on a cubesat body.  FIG. 26A  shows the stowed position and  FIG. 26B  shows the deployed position. 
           [0036]      FIG. 27  shows a prototype vector sensor array with the crossed loop arms stowed. 
           [0037]      FIG. 28  shows the prototype vector sensor array with the crossed loop arms deployed. 
           [0038]      FIGS. 29A-29C  show the telescoping hub mechanism and vector sensor array according to one embodiment. 
           [0039]      FIGS. 30A-30C  show the telescoping hub mechanism and vector sensor array according to a second embodiment. 
           [0040]      FIG. 31  shows the connections between the beamformer and the receiver. 
       
    
    
     LIST OF TABLES 
       [0000]    
       
         TABLE 1 lists the input impedance versus frequency for the vector sensor dipole mode. 
         TABLE 2 lists the input impedance versus frequency for the vector sensor vertical loop mode. 
         TABLE 3 lists the input impedance versus frequency for the vector sensor monopole mode. 
         TABLE 4 lists the input impedance versus frequency for the vector sensor horizontal loop mode. 
       
     
       DETAILED DESCRIPTION 
       [0045]      FIG. 1  illustrates a novel receive array antenna system designed for mapping of galactic radio frequency electromagnetic fields  50 . The electrical system includes deployable antennas  60 , receivers  70 , an onboard signal processing unit  80 , and a downlink system  90  to communicate the received data to a ground station (not shown). The system comprises a multipolarized antenna array with up to six co-located antenna elements, multichannel digital receiver, and a signal processing unit. The signal processing unit  80  may comprise a computer or other controller having a processing unit and an associated memory device. The memory device, which may be volatile or non-volatile, may contain the instructions which, when executed by the processing unit, enable the signal processing unit to perform the functions described herein. As described in more detail below, the antenna array can be installed and deployed on a tower, a balloon or from a satellite such as a cubesat. 
         [0046]    In the case of a galactic source, an electromagnetic wave is received by the vector sensing antennas  60 , each having calibrated amplitude and phase receive radiation patterns. The antennas  60  are connected by means or radiofrequency coaxial cables, twin lead, or microstrip lines to channels of the digital receiver  70  that filter, down convert, and digitize the received radio frequency wave. A signal processing unit  80  processes the digitized data, and then on-board global positioning system (GPS) and inertial navigation system (INS) data are used as reference position and orientation information in mapping location of the galactic radio frequency source. 
         [0047]    The general case of an electromagnetic wavefront attributed to a galactic radio frequency electromagnetic field  50  incident on a set of antennas including three orthogonal loop modes  200  and three orthogonal dipole modes  100  is shown conceptually in  FIG. 2 . A dipole consists of two monopole segments, and a monopole over an electrically conducting ground plane has radiation pattern characteristics similar to a dipole. In the system disclosed, the antenna system includes co-located crossed wire, tubular, or metal tape antennas with up to six simultaneous operating modes including two orthogonal directional dipole modes, two orthogonal directional loop modes, an omnidirectional monopole mode, and an omnidirectional loop mode. When a galactic radio frequency electromagnetic field is received, the unique antenna pattern amplitude and phase distributions are effective in forming a signal correlation matrix that contains the galactic wave&#39;s direction of arrival information. 
         [0048]      FIG. 3  shows a pictorial view of a vector sensor half-loop antenna  150  deployed on the side of an electrically conducting housing  790 , which can represent a small satellite, sometimes referred to in the literature as a cubesat. A typical cubesat has dimensions 10 cm×10 cm×30 cm (also referred to as a 3U cubesat). This half-loop antenna  150  may be used in monopole and loop modes. 
         [0049]      FIGS. 4A-4B  show the concepts of monopole modes  110  and loop modes  210  deployed from the side of a cubesat metallic housing  790 , respectively. In monopole mode  110 , the currents are flowing from the housing  790  in the same direction (i.e. either currents both flow toward housing  790  or away from housing  790 ). In loop mode  210 , the current flows out from one terminal on the housing  790  and returns at the second terminal. These half loops  150  may be combined to form full loops. 
         [0050]      FIG. 5  depicts a full-loop  151  composed of two half-loops  150   1  and  150   2 , with four ports  941   1 ,  941   2 ,  941   3 ,  941   4 . By adjusting the amplitude and phase relation of the four ports, either a dipole or loop mode can be generated.  FIG. 6  is a pictorial view of a vector sensor full-loop  151  operating in the dipole mode  130 .  FIG. 7  is a pictorial view of a vector sensor full-loop  151  operating in the loop mode  230 . 
         [0051]    While  FIGS. 5-7  show a full loop  151  configured on opposite sides of the housing  790 , it is understood that a second full loop may be configured on the remaining opposite sides of the housing  790 . This creates a second full loop that is orthogonal to the full loop  151 . 
         [0052]    Importantly, the full loop antenna  151  is created by two half loops  150   1  and  150   2 , with the metallic housing  790  disposed between these two half loops. The electrical connections used to create this full loop are shown in  FIGS. 20 and 21  and will be described in detail below. 
         [0053]    In addition to the loop antennas, monopole and loop antennas may also be deployed on the housing  790 .  FIG. 8  depicts a monopole antenna  132  deployed from the end of a cubesat housing  790 .  FIG. 9  shows the concept of a horizontal loop antenna  240  deployed around the perimeter of a cubesat housing  790 . 
         [0054]    Thus, it is possible to create six modes through the use of crossed loop antennas, a horizontal loop antenna and a monopole antenna. In the preferred embodiment, a full set of vector sensor antenna modes are deployed from a cubesat housing  790 , as shown in  FIG. 10 . In this full vector sensor, there are two crossed loop antennas (loop  259   1  oriented with the plane of the loop perpendicular to the y axis, and loop  259   2  oriented with the plane of the loop perpendicular to the x axis) operating with dipole and loop modes. Monopole antenna  132  is deployed from the end of the cubesat housing  790  in the z direction. Omnidirectional horizontal loop  240  fed with equal amplitude and equal phase at four points  401   1 ,  401   2 ,  401   3 ,  401   4  via four feedlines  411   1 ,  411   2 ,  411   3 ,  411   4 . The polarity ± of the connections to the horizontal loop antenna  240  is indicated. Omnidirectional horizontal loop  240  is electrically isolated from the crossed loop antennas  259   1  and  259   2 , but it may be mechanically connected to the crossed loop antennas  259   1  and  259   2  to provide mechanical stability. Omnidirectional horizontal loop antenna  240  may be oriented to lie in the x-y plane. 
         [0055]    In the preferred embodiment, the full vector sensor antenna has a diameter between 1 meter and 5 meters. The antennas have ultrawideband radiation pattern characteristics, such that the radiation pattern shape remains essentially constant until the operating frequency approaches resonance of the antennas. 
         [0056]    In certain embodiments, the receiving antenna elements form a collocated array of antenna elements with common phase centers. In some embodiments, the receive antenna elements operate over the frequency band 0.1 MHz to up to 70 MHz. 
         [0057]      FIG. 11  shows an enlarged view of the housing  790  showing the connection ports  941   1 ,  941   2 ,  941   3 ,  941   4  for one of the full loop antennas  259   1  and  259   2 . As also shown in  FIG. 5 , the full loop antenna is created even though the housing  790  is disposed in the middle or the loop. This configuration is advantageous, in that it allows access to more points along the loop. 
         [0058]    An electromagnetic simulation model was developed for a full vector sensor array shown in  FIG. 10  with six modes and analyzed using the commercial FEKO software with a method of moments solver. In the electromagnetic simulations, the diameter of the vector sensor array was assumed to be approximately 3 meters, and the array was housed on a 3U cubesat body. The monopole antenna  132  was assumed to be 1.5 meters long. The antennas were modeled as thin wires. Each vector sensor antenna was driven with the desired amplitude and phase while the surrounding antennas were terminated in 50-ohm loads. 
         [0059]      FIG. 12  summarizes the polarized (E θ , E φ , H θ , H φ ) radiation patterns of the six vector sensor modes. In  FIG. 12 , standard spherical coordinates are used and the radiation patterns shown are at 10 MHz. Dipole  1  is oriented along the x axis and responds to the E φ  field with a peak along the y axis. Dipole  2  is oriented along the y axis and responds to the E φ  field with a peak along the x axis. Loop  1  is in the xz plane and has peak radiation along the x axis. Loop  2  is in the yz plane and has peak radiation along the y axis. The monopole mode responds to the E θ  component and is omnidirectional with respect to the z axis. The horizontal loop mode responds to the H θ  component and is omnidirectional with respect to the z axis. The radiation pattern shapes are frequency independent up to the range of approximately 40 to 70 MHz where the antennas approach resonance. 
         [0060]    The input impedance of each of the vector sensor modes was simulated. The simulated input impedance for the vector sensor dipole mode is shown in  FIG. 13  and resonance occurs near 70 MHz.  FIG. 14  shows the simulated input impedance for the vector sensor vertical loop mode and resonance occurs near 42 MHz.  FIG. 15  shows the simulated input impedance for the vector sensor vertical monopole mode and resonance occurs near 50 MHz.  FIG. 16  shows the simulated input impedance for the vector sensor horizontal loop mode and resonance occurs near 63 MHz. The input impedances for these modes are summarized in Tables 1 to 4.  FIG. 17  shows the simulated mismatch loss relative to a 50-ohm system for the vector sensor modes.  FIG. 18  shows simulated current amplitude distributions for the dipole and loop modes, and  FIG. 19  shows simulated current distributions for the monopole and horizontal loop modes. 
         [0061]    Referring back to  FIG. 10 , the feedlines  411   1 ,  411   2 ,  411   3 ,  411   4  for the horizontal loop  240  can be twin lead, twisted pair, or coaxial cable depending on the beamformer design. The cubesat housing  790  contains the beamforming circuit that provides the necessary amplitude and phasing to form the desired vector sensor modes. Two types of vector sensor beamforming circuits are shown in  FIG. 20  and  FIG. 21 . 
         [0062]      FIG. 20  shows a PC board  904  according to one embodiment. The inputs and outputs to the PC board  904  are shown along the outer edge. Ports  941   1 - 941   8  represent the eight connection points for the loop antennas  259   1 ,  259   2  (see  FIGS. 10 and 11 ). Each pair of ports, such as ports  941   1  and  941   2  attach to legs of different half loops in a loop antenna (see  FIG. 11 ). Each pair of ports is in communication with a respective balun  92   1 - 92   4 , which converts the unbalanced signals from the antenna to balanced signal. Since each loop antenna has four ports, there are a total of eight ports and four baluns  92   3 - 92   4 . The signals from the two baluns associated with each loop antenna are fed to a hybrid magic tee device  501   1 ,  501   2 . Thus, the ports  941   1 - 941   4  utilize hybrid magic tee device  501   1  and the ports  941   5 - 941   8  utilize hybrid magic tee device  501   2 . 
         [0063]    Each hybrid magic tee device  501   1 ,  501   2  has two outputs, a sum and a difference. A schematic diagram of a hybrid magic tee device  501  is shown in  FIG. 24 . The hybrid magic tee ports are designated A, B, C, and D and the phasing between the ports is indicated. The C port provides the sum of the received signals at ports A and B, that is, C=A+B. The D port provides the difference between the received signals at ports A and B, that is, D=B−A. Importantly, the sum port is used for the loop mode and the difference port is used for the dipole mode, as explained in more detail below. The 4-way divider  184  is used for the horizontal loop antenna  240  (see  FIG. 10 ). The four signals from the 4-way divider  184  attach to ports C 1 -C 4 . 
         [0064]    In  FIG. 20 , the ports labeled C 1 , C 2 , C 3 , C 4  are connected to micros trip lines which are suitable for connecting coaxial cables that are routed to the loop feed points  401   1 ,  401   2 ,  401   3 ,  401   4 . In this case with coaxial feedlines, transformer baluns with the required polarity would be located at each feed point  401   1 ,  401   2 ,  401   3 ,  401   4  (see  FIG. 10 ). 
         [0065]      FIG. 21  is similar to  FIG. 20  in many ways. For example, the circuitry associated with the loop antennas  259   1 ,  259   2  is identical. Differences exist in the control of the horizontal loop antenna  240 . In  FIG. 21 , there are four baluns  92   5 ,  92   6 ,  92   7 ,  92   8 , that are used to feed the horizontal loop antenna  240 , and the polarity ± of the connections W 1 , W 2 , W 3 , W 4 , W 5 , W 6 , W 7 , W 8  to the antennas are indicated corresponding to the desired polarities shown in  FIG. 10 . With the four baluns  92   5 ,  92   6 ,  92   7 ,  92   8 , twisted pair or twin lead wires can connect to the four feed points  401   1 ,  401   2 ,  401   3 ,  401   4 . (see  FIG. 10 ) 
         [0066]    The outputs from the beamformer disposed on PC board  904  are connected to the receiver  70 , as shown in  FIG. 31 . Specifically, the five outputs from the beamformer (Dipole x, Loop x, Dipole y, Loop y and horizontal loop z) are each in communication with a respective channel on the receiver  70 . Additionally, the monopole antenna  132  is also in communication with a channel of the receiver  70 . Thus, the receiver  70  receives six different modes. The terms “mode” and “channel” are used interchangeably in this disclosure. The receiver  70  can filter, down convert, and digitize the received radio frequency waves. A signal processing unit  80  processes the digitized data, and then on-board global positioning system (GPS) and inertial navigation system (INS) data are used as reference position and orientation information in mapping the location of the galactic radio frequency source. 
         [0067]      FIG. 22  shows a simplified schematic diagram of the vector sensor antenna beamformer in which the difference port of a hybrid magic tee device  501   1  generates dipole mode current flow.  FIG. 23  shows a schematic diagram of a vector sensor antenna beamformer in which the sum port of a hybrid magic tee device  501   1  generates loop mode current flow. 
         [0068]    A prototype vector sensor antenna with 1.5 meter arms with dipole, loop, and monopole modes was fabricated, and the measured reflection coefficients for these three modes is shown in  FIG. 25 . 
         [0069]    Signal processing for direction finding can be performed as follows. Each of the signals received by the vector sensor modes a e connected to a channel of the microwave receiver  70  (see  FIG. 31 ). The receiver channels amplify, filter, downconvert, and digitize the received RF signals from a galactic source. The receiver can form single or multiple channels by means of switching and filtering. A radiofrequency signal covariance matrix R is computed by taking the frequency average or time average of the digitized received voltages correlated between all pairs of vector sensor antenna modes. For the disclosed multi polarized vector sensor array antenna system, the matrix R is a six row by six column matrix. Mathematically, in computing the correlation R on  between the mth and nth vector sensor antenna channel voltages V m  and V n  respectively, the frequency average is expressed as the integral over the receive bandwidth of the product of V m  and V n * where * means complex conjugate. Well known direction finding algorithms can then be used in the signal processing computer to generate the coordinates of galactic RF source. 
         [0070]    Mechanical deployment of the vector sensor antennas may be performed in a variety of ways.  FIGS. 26A-2   6 B show one possible embodiment.  FIGS. 26A-B  show a conceptual diagram for the deployment of the vector sensor antennas on a cubesat housing  790 , where  FIG. 26A  shows the stowed position and  FIG. 26B  shows the deployed position. As shown in  FIG. 26A , the loop arms  259  and horizontal loop wires are initially coiled on a telescopic hub mechanism  900  stowed within the cubesat housing  790 . The monopole antenna  132  is rolled up and/or folded up and stowed in a cylindrical volume at the end of the cubesat housing  790 . For example, the monopole antenna  152  may be folded back on itself a plurality of times to minimize its height. Alternatively, it may be rolled on a vertically oriented spooler. 
         [0071]    During deployment, first, the telescopic hub mechanism  900  is extended. Then the monopole antenna  132  is extended from the external cylindrical volume. Finally, the loop arms  259  and horizontal loop are uncoiled from the telescopic hub mechanism  900 , forming, monopole and loop shapes as depicted during deployment in  FIG. 26B . 
         [0072]    Another view of this embodiment is shown in  FIGS. 29A-29D . In  FIG. 29A , a perspective view of the telescopic hub mechanism  900  in the stowed position is shown. The telescopic hub mechanism  900  includes an upper spooler  910   a , and a lower spooler  910   b  mounted on a central rod  914 . These upper and lower spoolers  910   a ,  910   b  are each wound with four electrically conducting tapes  913 , each tape  913  offset from the adjacent tapes by 90°. The ends of each of the four tapes  913  on upper spooler  910   a  is connected to the end of a respective tape  913  on lower spooler  910   b  by a conductive member  911 . These conductive members  911  form the vertical connections for each half loop (see  FIG. 10 ). These conductive members  911  may be electrically conductive wires, or electrically conductive rods. A feed spooler  912  is disposed between the upper and lower spoolers  910   a ,  910   b . The feed spooler  912  holds the feed wire  411  used to connect to the horizontal loop antenna  240  at points  401  (see  FIG. 10 ). 
         [0073]    During deployment, the telescopic hub mechanism  900  first extends vertically, as shown in  FIG. 29B . Springs  915  or other biasing members may be used to push the upper and lower spoolers  910   a ,  910   b  away from one another.  FIG. 29B  also shows a teed spooler  912 . Although not shown, the horizontal loop antenna  240  may be physically connected to the conductive members  911 . While the horizontal loop antenna  240  is physically attached to these conductive members  911 , they are electrically isolated from one another. 
         [0074]    After the telescopic hub mechanism  900  has extended vertically, the upper and lower spoolers  910   a ,  910   b  start rotating to release the tapes  913  which form the loop antennas  259 , as shown in  FIG. 29C . The electrically conducting tapes  913  spiral outward. In certain embodiments, the upper and lower spoolers  910   a ,  910   b  and the feed spooler  912  are locked together rotationally such that all unwind at the same rate. 
         [0075]    When the tapes  913  are fully unwound, the tapes  913  are each directed at a different perpendicular direction. 
         [0076]    Thus, each of the four tapes  913  on upper spooler  910   a  forms part of a half loop. The corresponding tape  913  on lower spooler  910   b  shows another part of the half loop. Finally, the conductive member  911 , which connects the upper tape to the lower tape, forms the final part of the half loop. Thus, when the tapes  913  are extended, four half loops, which form two crossed loop antennas  259  are formed. 
         [0077]    Additionally, the horizontal loop antenna  240  is physically attached to the conductive members  911 , and is formed when the half loops are extended outward. Specifically, the horizontal loop antenna  240  is in the shape of a square, where each corner of the horizontal loop antenna  240  is formed by one of the four conductive members  911 . As noted above, feed wires  411  (see  FIG. 10 ) are supplied to the horizontal loop antenna  240  by feed spooler  912 . 
         [0078]    As described above, the tapes  913  form the crossed loop antennas. Physical connections are made between the horizontal loop antenna  240  and the conductive member  911  at the end of each half loop. Additionally, physical connections are made at the midpoint of each side of the horizontal loop antenna  240 , as the horizontal loop antenna is actually four segments, each segment in communication with feed wires  411  at each end. 
         [0079]    Electrically conducting tape can be used as the loop antenna  259  and also as the monopole antenna  132 , and electrically conducting wire can be used to form the horizontal loop antenna  240 . Alternatively, non-conductive materials can be used for the structures making up the loop and monopole arms with conductive material running parallel to the nonconductive structural member. Uncoiling of the vector sensor arms can be accomplished by releasing stored strain in the coiled tapes, motors, centripetal forces, shape memory strain recovery or other actuation method. 
         [0080]    A mechanically deployed prototype vector sensor antenna was fabricated using metal measuring tapes mounted on a hub width crossed loops supported by strings on an aluminum frame to counter gravity effects. The stowed crossed loop tapes  913  and horizontal feed wires  411  are shown in  FIG. 27 , and the deployed vector sensor array of crossed loops is shown in  FIG. 28 . 
         [0081]    The electrical connections between the PC board  904  and the antenna segments may all be made via the central rod  914 . The central rod  914  may include one or more slip rings to allow the wires that are disposed on the spoolers to pass inside the central rod  914  and connect to the PC board  904 . 
         [0082]    While  FIGS. 26-29  show a plurality of spoolers  910   a ,  910   b  and  912  mounted on a central rod  914 , other embodiments are also possible. 
         [0083]    For example,  FIGS. 30A-30C  show a second embodiment, where the tapes  913  are affixed to the central member  924 , and the spoolers are disposed around the central member  924 . The central member  924  may be a cylinder, a rectangular prism or another shape. In certain embodiments, the central member  924  may include an internal cavity to route the electrical connections from the antennas to the beamformer. 
         [0084]    Similar elements have been given identical reference designators.  FIG. 30A  shows a stowed position, where upper spoolers  950   a - d  and lower spoolers  951   a - d  are disposed proximate the central rod  914 . Feed spoolers  952   a - d  are disposed between the upper and lower spoolers. While four upper spoolers, three lower spoolers and two feed spoolers are visible, it is understood that there are four of each type. 
         [0085]    As the telescopic hub mechanism  900  is deployed, the upper spoolers  950  and the lower spoolers  951  moved away from each other, as shown in  FIG. 30B . Feed spoolers  952   a - d  may be connected to the upper spoolers in some embodiments. Unlike the embodiment of  FIGS. 29A-29C , the spoolers are not attached to the central member  924 . Rather, the tapes  913  and feed wires  411  may be directly attached to the central member  924  without the need for slip rings. 
         [0086]      FIG. 30C  shows the vector sensor array in the deployed position, where the spoolers are all located at the far extremity of the half loops. In certain embodiments, rods (not shown) may be used to connect each of the four sets of the upper spooler, feed spooler and lower spooler. In another embodiment, the conductive members  911  serve this function. This may help maintain the desired spatial relationship and insure that each spooler unwinds at the same rate. The upper spoolers  950   a - d  and lower spoolers  951   a - d  are disposed at the distal ends of the loop antennas, while the feed spoolers  952   a - d  are disposed along the horizontal loop antenna  240  between the upper and lower spoolers. 
         [0087]    In certain embodiments, the multipolarized vector sensor array antenna system can be mounted on structures including ships, towers, ground vehicles, or satellites. In certain embodiments, to take account of electromagnetic field scattering effects the multipolarized vector sensor array antenna system is calibrated on a structure by using a known radiofrequency transmitting source and measuring the signal of the known source at multiple angles prior to geolocating the unknown location of an RF signal source. The array antenna calibration can be accomplished by electromagnetic simulations and by measurements. 
         [0088]    While the invention has been particularly shown and described with references to illustrated embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For instance, the apparatus described herein is applicable from low RF frequencies to high microwave frequencies. Further, the invention is applicable to installation on towers, in buildings, and on vehicles such as ground moving vehicles, airborne vehicles, and satellites. In addition to galactic RF source mapping, with appropriate scaling of the size of the antenna array, invention can be applied to geolocation in search and rescue in which the RF source an emergency beacon.