Abstract:
A high gain, steerable phased array antenna includes multiple oblong slots. For each of the oblong and preferably rectangular slots, an electrical microstrip feed line is disposed within a parallel plane to the slot, and extends in the short dimension of the slot across the center of its long dimension. The microstrip feed lines and corresponding oblong slots form magnetically coupled LC resonance elements. A main feed line couples with the microstrip feed lines. Delay circuitry is used to electronically steer the antenna by selectively changing signal phases on the microstrip feed lines. One or more processors operating based on program code continuously or periodically determine a preferred signal direction and control the delay circuitry to steer the antenna in the preferred direction. The preferred signal direction is determined based on a directional throughput determination.

Description:
BACKGROUND 
   Conventional phased array antennas incorporate waveguide technology with the antenna elements. A waveguide is a device that controls the propagation of an electromagnetic wave so that the wave is forced to follow a path defined by the physical structure of the guide. Waveguides, which are useful chiefly at microwave frequencies in such applications as connecting the output amplifier of a radar set to its antenna, typically take the form of rectangular hollow metal tubes but have also been built into integrated circuits. A waveguide of a given dimension will not propagate electromagnetic waves lower than a certain frequency (the cutoff frequency). Generally speaking, the electric and magnetic fields of an electromagnetic wave have a number of possible arrangements when the wave is traveling through a waveguide. Each of these arrangements is known as a mode of propagation. It is desired to have a phased array antenna that provides enhanced gain characteristics. It is also desired to have a phased array antenna system with a more efficient means for determining and controlling the antenna to be steered according to a most desired directionality. 
   SUMMARY OF THE INVENTION 
   A high gain, steerable phased array antenna includes a board or conducting sheet having multiple slots. For each of the slots, an electrical microstrip feed line is disposed within a parallel plane to the slot. The microstrip feed lines and corresponding slots form magnetically coupled LC resonance elements. A main feed line couples with the microstrip feed lines. Delay circuitry is used to electronically steer the antenna by selectively changing signal phases on the microstrip feed lines. One or more processors operating based on program code continuously or periodically determine a preferred signal direction and control the delay circuitry to steer the antenna in the preferred direction. Preferably the slots are oblong or rectangular. The microstrip feed lines preferably extend in the short dimensions of the slots. 
   A method of operating a high gain, steerable phased array antenna is also provided. The method includes electronically steering the above-described antenna by controlling the delay circuitry, continuously or periodically determining a preferred signal direction, and controlling the delay circuitry to selectively change signal phases on the microstrip feed lines and thereby steer the antenna in the preferred direction. 
   A further high gain, steerable phased array antenna is also provided, along with a corresponding method of operating it. The antenna includes multiple resonant elements and a main feed coupling with the resonant elements. Electronics are used for steering the antenna by providing different inputs to the resonant elements. One or more processors operating based on program code continuously or periodically determine a preferred signal direction based on a directional throughput determination, and control the electronics to steer the antenna in the preferred direction. The resonant elements are preferably oblong or rectangular slots defined in a board. 
   The antenna signal preferably includes multiple discreet lobes extending in different directions away from the antenna. The lobes are preferably selected by controlling the electronics based on the directional throughput determination. 
   The directional throughput determination may include monitoring the throughput of an initial selected lobe, and when the throughput drops below a threshold value, or drops a predetermined percentage amount, or becomes a predetermined amount above a noise level, or combinations thereof, then changing to an adjacent lobe and similarly monitoring its throughput. When the adjacent lobe is determined to have a throughput that is below a threshold value, or is at least a predetermined percentage amount below a maximum value, or is below a predetermined amount above a noise level, or combinations thereof, then the selected lobe is changed to the other adjacent lobe on the opposite side of the initial selected lobe. The directional throughput determination may also include scanning through and determining the throughputs of all or multiple ones of the lobes, wherein the lobe with the highest throughput is selected. 
   One or more processor readable storage devices are also provided having processor readable code embodied thereon. The processor readable code programs one or more processors to perform any of the methods of operating a high gain steerable phased array antenna described herein. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a front view of a high gain steerable phased array antenna in accordance with a preferred embodiment. 
       FIG. 2  illustrates a back view of a high gain steerable phased array antenna in accordance with a preferred embodiment. 
       FIG. 3  illustrates micro feed line coupling to resonant slots in accordance with a preferred embodiment. 
       FIG. 4  schematically illustrates delay electronics coupled with microstrip feed lines for steering a phased array antenna in accordance with a preferred embodiment. 
       FIGS. 5A–5D  show exemplary signal distribution plots in various directions based on selections of different lobes in accordance with a preferred embodiment. 
       FIG. 6  schematically illustrates an electronic component representations of elements of a phased array antenna in accordance with a preferred embodiment. 
       FIGS. 7–8  are a flow diagram of operations performed for selecting a signal distribution lobe of a phased array antenna in accordance with a preferred embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , a high gain steerable phased array antenna in accordance with a preferred embodiment includes a conducting sheet  102 . The conducting sheet  102  is preferably an area of sheet metal such as copper, and may be composed of one or more of various metals or other conductors. Four slots  104  are cut into the conducting sheet  102 . More or fewer slots  104  of arbitrary number may be used, although preferably the slots  104  are arranged in such a manner that they complement each other in a phased array pattern. Each time the number of slots are doubled, the gain is increased by 3 dBi. 
   The slots  104  are preferably oblong and more preferably rectangular. However, the slots  104  may be square or circular or of an arbitrary shape. The preferred dimension of the sheet is 5⅞″ wide by 5⅛″ tall. The preferred dimensions of the rectangular slots is ⅝″×2⅛″. The dimensions of the slots  104  are generally preferably a half wave (λ/2) wide and a quarter wave (λ/4) wave high. The drive impedances of the slots  104  is preferably (60)sq/73=494 ohms. An advantageous gain characteristic is achieved due to the lack of losses in the transition to free space of 377.564 ohms. 
   A coaxial cable  105  is connected to the sheet  102  preferably by soldering. Although  FIG. 2  will show the electrical arrangement of the antenna in more detail,  FIG. 1  shows four soldered connections  106  at the middles of long edges of the rectangular slots  104 . A signal cable  108  is also shown in  FIG. 1 , along with a few other solder connections  110  to the sheet  102  from the back side. 
     FIG. 2  illustrates a back side view of a high gain steerable phased array antenna in accordance with a preferred embodiment. This side of the antenna includes a circuit board with various electrical connections. The slots  104  that are cut into the conducting sheet at the front side are shown in dotted lines in  FIG. 2  for perspective as to their relative location to the electrical components on the back side. The micro strip feed line connections  206  correspond to the solder connections  106  to the conducting sheet  102  on the front side. These connections  206  are preferably at the centers of the long edges of the oblong and preferably rectangular slots  104 . The connections  206  may be alternatively located at the centers of the short edges, or again the slots  104  may be squares or circles or arbitrary shapes. 
   The slots  104  are resonant by means of a coupling mechanism. The coupling mechanism connects to the resonant slots  104  using microstrip feed lines  212 . The microstrip feed lines are constructed on a separate plane of the antenna. The resonant slots  104  are fed in parallel, preferably with 100 ohm microstrip feed lines  212 . The microstrip feed lines  212  are shown crossing the short dimensions of the rectangular slots  104  at their centers. The microstrip feed lines  212  are each connected to a series of electronic circuitry components  214 . In  FIG. 2 , each microstrip feed line  212  is has four of these components  214  illustrated as squares. These components  214  include electronic delays that permit the antenna to be directionally steerable. Preferably the components  214  include PIN diodes and inductors. The diodes may be of type diode PIN 60V 100 mA S mini-2P by Panasonic SSG (MFG P/N MA2JP0200L; digikey MA2JP0200LTR-ND). The inductors may be of type 1.0 μH +/−5% 1210 by Panasonic (MFG P/N ELJ-FA1R0JF2; digikey PCD1825TR-ND). 
   The antenna is electronically steered by adding the delay circuitry  214  to the microstrip feed lines  212 . The delay changes the phase of the signal on the microstrip feed lines. The delay circuitry includes the PIN diodes and a pad cut into the copper plane of the circuit board. When the PIN diode is turned on, delay is added to the circuit. This means that it can be used to follow the source of the signal. The signal can originate from a wireless access point, a portable computer, or another device. 
   The microstrip feed lines  212  each connect to a main feed line  216 . The two microstrip feed lines  212  in the upper half of the antenna of  FIG. 2  are connected to the upper half of the main feed line  216 , and the two microstrip feed lines  212  in the lower half of the antenna of  FIG. 2  are connected to the lower half of the main feed line  216 . The main feed lines is connected at its center to a coax connection segment  218  that is connected to the coaxial cable  105 . Various traces  220  are shown connecting the delay pads  214  to the signal cable  108 . The signal cable  108  in turn connects to computer operated control equipment. 
   The antenna of  FIGS. 1–2  has four resonant slots  104 . The top and bottom halves of the antenna are mirror images of one another. Two 100 ohm feed lines feed the two resonant slots  104  in the upper half of the antenna shown at  FIG. 1 . The 100 ohm feed lines are in parallel. The resulting resistance is 50 ohms. This matches the resistance of the 50 ohm main feed line  216 . When the lower half of the antenna is taken into account, the center of the antenna is at 25 ohms, i.e., two 50 ohm circuits in parallel. The input impedance of the antenna is selected to be 50 ohms according to the preferred embodiment. An impedance matching pad of 35.35 ohms achieves this. 
   Referring now to  FIG. 3 , micro feed line coupling points  306  are illustrated. These coupling points  306  are at the centers of long edges of the resonant slots  104 . The microstrip feed lines  212  cross the short dimensions of the slots  104 . As  FIG. 3  is only for illustration, only the slots  104 , microstrip feed lines  212  and connections points  306  are shown. The connections  306  of the two slots  104  in the lower half of the antenna of  FIG. 3  are at the lower long edges of the slots  104 . In  FIG. 2 , they were shown connected to the upper long edges of the slots  104 . The microstrip feed line connections to the two slots in the upper half of the antenna could also be to the lower edges of the slots  104 . Moreover, the slots  104  and microstrip feed lines  212  could be rotated ninety degrees, or another arbitrary number of degrees, or only the slots may be rotated, or only the microstrip feed lines  212  may be rotated. 
     FIG. 4  schematically illustrates the delay electronics  214  coupled with the microstrip feed lines  212  for steering the phased array antenna in accordance with a preferred embodiment. Each of the microstrip feed lines  212  is shown in  FIG. 4  coupled with three groups of electronics including a pin diode pad  424  and an inductor  426 . The delay pads  424  are enabled and disabled by a voltage of +5 Volts and −5 Volts respectively on select lines. 
     FIGS. 5A–5D  show exemplary signal distribution plots in various directions based on selections of different lobes in accordance with a preferred embodiment. The pads illustrated in  FIG. 4  are labeled one through six, or pads # 1 , # 2 , # 3 , # 4 , # 5  and # 6 . The signal distribution plots were generated based on selectively turning on certain of pads # 1 –# 6 .  FIG. 5A  illustrates a signal distribution of the antenna when only pad # 1  is selected.  FIG. 5B  illustrates a signal distribution of the antenna when pads # 1 , # 2  and # 3  are each selected.  FIG. 5C  illustrates a signal distribution of the antenna when only pad # 4  is selected.  FIG. 5D  illustrates a signal distribution of the antenna when pads # 4 , # 5  and # 6  are each selected. 
     FIG. 6  schematically illustrates an electronic component representations of elements of a phased array antenna in accordance with a preferred embodiment. The slots  104 , microstrip feed lines  212 , main feed line  216 , coax attachment point  218  and microstrip feed line attachments points  306  are each shown and are preferably as described above. The microstrip feed line attachment points  306  are preferably grounded as illustrated in  FIG. 6 . The pin diode pads  424  and inductors  426  are illustrated with their common electrical representations. 
     FIGS. 7–8  are a flow diagram of operations performed for selecting signal distribution lobes based on monitoring the throughput of lobes of a phased array antenna in accordance with a preferred embodiment. Although two lobes or more than three lobes may be available, the example process of  FIG. 7  assumes three lobes for illustration. At  702 , the IP address of a connected wireless device is obtained. The lobe data is scanned and logged for this connection to the antenna. Of the lobes that may be selected, the lobe with the highest throughput is selected. Throughput is the speed at which a wireless network processes data end to end per unit time. Typically measured in mega bits per second (Mbps). In this example, it will be assumed the middle of three lobes is selected. 
   This lobe is maintained as the selected lobe as long as the throughput remains above a threshold level. The threshold level may be a predetermined throughput level, or a predetermined throughput or percentage of throughput below a maximum, average or pre-set throughput level, or may be based on a comparison with other throughputs. At  FIG. 8 , which will be described in detail further below, if a signal strength falls to a noise level or within a certain amount of percentage of a noise level, then this fallen signal strength is used to determine when to select another lobe. The throughput is monitored according to the process of  FIG. 7  continuously or periodically at  708 . The process remains at  708  performing this monitoring unless it is determined that the throughput has dropped below the threshold level. Then at  710  another is lobe is selected such as the next closest lobe to the right. It is determined at  712  whether the throughput with this lobe is above or below the threshold. If the throughput with this new lobe is above the threshold, then the process moves to  714 . At  714 , the lobe number and signal strength of the new lobe and/or other data are saved. Now, the monitoring at  716  will go on with the new lobe as it did at  708  with the initial lobe. That is, the process will periodically or continuously monitor the throughput of the connection with the new lobe. The process moves to  718  only when the throughput with the new lobe is determined at  716  to be below the threshold level. Referring back to  712 , if the throughput with the new lobe is determined there to be below the threshold, then the process moves directly to  718 . At  718 , yet another lobe, a third lobe, is selected such as the closest lobe to the left of the initial lobe. It is determined at  720  whether the throughput is above or below the threshold. If it is above the threshold, then this lobe will remain the selected lobe unless and until the throughput falls below the threshold. If the throughput does drop below the threshold, then at  724  lobe data is scanned and logged, and the process returns to  706  to select the highest throughput lobe again. 
   The process at  FIG. 8  illustrates monitoring of the signal strengths and other data of all of the lobes according to a further embodiment, e.g., to select the strongest lobe. Referring now to  FIG. 8 , lobe #1, e.g., is selected at  802 . The signal strength of the connection of a wireless device is read at  804 . If the signal strength is determined to be above a noise level, or alternatively if the signal strength is above some predetermined amount or percentage above the noise level, then the throughput is calculated at  808 . The lobe number, signal strength and throughput are logged at  810  and the process moves to  812 . If at  806 , the signal strength is determined to be at a noise level or at or below a predetermined amount or percentage above the noise level, then the lobe number, signal strength and throughput (equal to 0) are logged at  814  and the process moves to  814 . 
   At  812 , it is determined whether the data regarding the last lobe has been processed. If it has not, then the process returns to  804  to perform the monitoring for the next lobe. If the lobe data for all of the lobes has been monitored and determined, then the process returns to caller at  818 . 
   The present invention has been described above with reference to a preferred embodiment. However, those skilled in the art having read this disclosure will recognize that changes and modifications may be made to the preferred embodiment without departing from the scope of the present invention. These and other changes or modifications are intended to be included within the scope of the present invention, as expressed in the following claims. 
   In addition, in methods that may be performed according to preferred embodiments and that may have been described above, and/or as recited in the claims below, the operations have been described above and/or recited below in selected typographical sequences. However, the sequences have been selected and so ordered for typographical convenience and are not intended to imply any particular order for performing the operations.