Low loss tunable matching network for pattern reconfigurable array antennas

Abstract

An array antenna system having an RF-port with individually controlled radiating elements.

Claims

1. An array antenna system comprising: a reconfigurable matching network connected to a multiport switch by a via; said reconfigurable matching network comprised of a port connected to an initial transmission line, said initial transmission line including a capacitor; an intermediate transmission line connected to said initial transmission line, said intermediate transmission line functions as an inductance transformer; a terminal transmission line connected to said intermediate transmission line on one end and a via on another end; a plurality of stubs, each of said plurality of stubs connected to said terminal transmission line by a diode; said diodes located between said ends of said terminal transmission line; each of said stubs connected to a DC line by an inductor; said multiport switch comprised of a plurality of arms, one end of said arms connected to said via and the other ends connected to a port; an RF choke connected to each of said arms, said RF choke turns power on and off at said port; and a plurality of antenna arrays, each array connected to a port of said arms.

2. The array of claim 1 wherein said stubs are the same.

3. The array of claim 2 wherein said arms are uniform.

4. The array of claim 3 wherein said stubs of said reconfigurable matching network change the impedance at said via.

5. The array of claim 4 wherein said RF chokes are comprised of a stub connected to said arm by a diode, said stubs connected to a DC line by an inductor.

6. The array of claim 5 wherein, when one port is enabled, it receives all the supplied power and, if more than one port is enabled, the supplied power is equally shared among them in the same phase, while maintaining input matching.

7. The array of claim 5 wherein said reconfigurable matching network is configured to tune an RF circuit at different input impedances.

8. The array of claim 4 wherein said RF chokes are comprised of a plurality of stub sets, each set comprised of a plurality stubs connected by diodes and wherein at least one stub of each set is connected to said arm by a diode, said stubs connected to a DC line by an inductor.

9. The array of claim 3 wherein said RF chokes are comprised of an RF switch.

10. The reconfigurable tuning network of claim 1 wherein said ports are configured to activate and deactivate radiating elements.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) In the drawings, which are not necessarily drawn to scale, like numerals may describe substantially similar components throughout the several views. Like numerals having different letter suffixes may represent different instances of substantially similar components. The drawings generally illustrate, by way of example, but not by way of limitation, a detailed description of certain embodiments discussed in the present document.

(2) FIG. 1A is a top view of a reconfigurable tuning switch topology for an embodiment of the present invention.

(3) FIG. 1B is a bottom view of a reconfigurable tuning switch topology for an embodiment of the present invention.

(4) FIG. 1C is a side view of a reconfigurable tuning switch topology for an embodiment of the present invention.

(5) FIG. 2 illustrates a reconfigurable matching network for an embodiment of the present invention.

(6) FIG. 3 illustrates an alternative possible reconfigurable matching network for an embodiment of the present invention.

(7) FIG. 4 illustrates a reconfigurable switching network for an embodiment of the present invention.

(8) FIG. 5 illustrates an alternative possible reconfigurable switching network for an embodiment of the present invention.

(9) FIG. 6A shows S-parameters of the reconfigurable switching network for an embodiment of the present invention with 1 port enabled.

(10) FIG. 6B shows S-parameters of the reconfigurable switching network for an embodiment of the present invention with 2 ports enabled.

(11) FIG. 6C shows S-parameters of the reconfigurable switching network for an embodiment of the present invention with 3 ports enabled.

(12) FIG. 6D shows S-parameters of the reconfigurable switching network for an embodiment of the present invention with 4 ports enabled.

(13) FIG. 7A shows a port's phase of the reconfigurable switching network for an embodiment of the present invention with 1 port enabled.

(14) FIG. 7B shows a port's phase of the reconfigurable switching network for an embodiment of the present invention with 2 ports enabled.

(15) FIG. 7C shows a port's phase of the reconfigurable switching network for an embodiment of the present invention with 3 ports enabled.

(16) FIG. 7D shows a port's phase of the reconfigurable switching network for an embodiment of the present invention with 4 ports enabled.

(17) FIG. 8A is a top view of a cube antenna implementing a reconfigurable tuning switch network for an embodiment of the present invention.

(18) FIG. 8B is a bottom view of a cube antenna implementing a reconfigurable tuning switch network for an embodiment of the present invention.

(19) FIG. 9A is a top view of a planar array antenna for an embodiment of the present invention.

(20) FIG. 9B is a bottom view of a planar array antenna for an embodiment of the present invention.

(21) FIG. 10A illustrates S-parameters response for a sequential power divider for an embodiment of the present invention.

(22) FIG. 10B illustrates consecutive phase difference response for a sequential power divider for an embodiment of the present invention.

(23) FIG. 11A shows a planar array's response and the input reflection coefficient for an embodiment of the present invention.

(24) FIG. 11B shows a planar array's response and the gain at plane Θ=90° degrees for an embodiment of the present invention.

(25) FIG. 12A shows a cube antenna system reflection coefficient for an embodiment of the present invention with 1 port enabled.

(26) FIG. 12B shows a cube antenna system reflection coefficient for an embodiment of the present invention with 2 ports enabled.

(27) FIG. 12C shows a cube antenna system reflection coefficient for an embodiment of the present invention with 3 ports enabled.

(28) FIG. 12D shows a cube antenna system reflection coefficient for an embodiment of the present invention with 4 ports enabled.

(29) FIG. 13A shows a cube antenna system radiation pattern when 1 port enabled for an embodiment of the present invention with port 1 enabled.

(30) FIG. 13B shows a cube antenna system radiation pattern when 1 port enabled for an embodiment of the present invention with port 2 enabled.

(31) FIG. 13C shows a cube antenna system radiation pattern when 1 port enabled for an embodiment of the present invention with port 3 enabled.

(32) FIG. 13D shows a cube antenna system radiation pattern when 1 port enabled for an embodiment of the present invention with port 4 enabled.

(33) FIG. 14A shows a cube antenna system radiation pattern when 2 ports enabled for an embodiment of the present invention with port 1 and port 2 enabled.

(34) FIG. 14B shows a cube antenna system radiation pattern when 2 ports enabled for an embodiment of the present invention with port 2 and port 3 enabled.

(35) FIG. 14C shows a cube antenna system radiation pattern when 2 ports enabled for an embodiment of the present invention with port 3 and port 4 enabled.

(36) FIG. 14D shows a cube antenna system radiation pattern when 2 ports enabled for an embodiment of the present invention with port 4 and port 1 enabled.

(37) FIG. 14E shows a cube antenna system radiation pattern when 2 ports enabled for an embodiment of the present invention with port 1 and port 3 enabled.

(38) FIG. 14F shows a cube antenna system radiation pattern when 2 ports enabled for an embodiment of the present invention with port 2 and port 4 enabled.

(39) FIG. 15A shows a cube antenna system radiation pattern when 3 ports enabled for an embodiment of the present invention with port 1, port 2, and port 3 enabled.

(40) FIG. 15B shows a cube antenna system radiation pattern when 3 ports enabled for an embodiment of the present invention with port 2, port 3, and port 4 enabled.

(41) FIG. 15C shows a cube antenna system radiation pattern when 3 ports enabled for an embodiment of the present invention with port 3, port 4, and port 1 enabled.

(42) FIG. 15D shows a cube antenna system radiation pattern when 3 ports enabled for an embodiment of the present invention with port 4, port 1, and port 2 enabled.

(43) FIG. 15E shows a cube antenna system radiation pattern when 4 ports enabled for an embodiment of the present invention with port 1, port 2, port 3, and port 4 enabled.

DETAILED DESCRIPTION OF THE INVENTION

(44) Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed method, structure, or system. Further, the terms and phrases used herein are not intended to be limiting, but rather to provide an understandable description of the invention.

(45) In a preferred embodiment, the present invention provides a reconfigurable tuning network 100 used to create an independent-port RF switch that maintains input matching during an alternative ports' activation, as seen in FIGS. 1A-1C. The embodiment shown uses as an example four ports 110-113 and consequently, fifteen (2.sup.4−1) matched switching states (excluding the OFF state). Also, the operating center frequency chosen for the example design is 10 GHz; nevertheless, the embodiments of the present invention may apply at any desired frequency.

(46) The tuning network of the present invention has stack topology that allows symmetrical surface currents resulting in balanced matching for all the possible switching combinations. In this case, it consists of two same 0.25 mm thick substrates 120 and 121 (RT6006, ε.sub.r=6.15, tan δ=0.0019) sharing a common ground plane 122. The first substrate 120 accommodates the reconfigurable matching network 130 shown in FIG. 1A, and the second substrate 121 has the switchable ports network 140, as shown in FIG. 1B. An exemplary configuration is illustrated in FIG. 1C, explained from top to bottom as follows.

(47) The reconfigurable matching network 200 located on the top substrate 120 as shown in FIG. 2, is composed of three transmission lines 210-212; components of the shelf at 10 GHz, a capacitor 250, inductors 260-262

(48) Initially, the signal path starts at the P0 port 270 at the 50 Ohm line TL.sub.1 (210). The line extends to a 0.8 pF capacitor 250, serving as DC-block, protecting the RF source. The λ.sub.g/4-line TL2 (211) serves as an inductance transformer, at 35.35 Ohm, matches the 50 Ohm line TL1 (210) to the 25 Ohm line TL3 (212). This line has the two PIN diodes 230, 231 assembled on it, and an inductor 261 of 3.8 nH, as part of the DC-bias network.

(49) The inductors allow the proper DC-circuit formation for the diodes' activation; diodes in turn are responsible for the reconfigurable stub integration in the switching network. The length of line TL3 (212) depends on the diodes integrated position. This position relies on the changeable input impedance at the point of VIA each time a new port is activated in the bottom layer. In other words, the matching happens using stubs, where the approach is the reconfigurable stubs/reactance to match a variety of input impedances. This approach is not limited just to the specific stub shown herein, but each of the stub can be reconfigurable too, by extending themselves using more active elements (320-322) and stubs (301-303) as FIG. 3 shows.

(50) Additionally, the active elements can be any RF switch type (PIN diode, RF MEMS, Varactor, etc. . . . ), preferable the ones introduce the least electromagnetic turbulence during the installation. This is the key for stable tuning performance and the realization of numerous reconfigurable stubs.

(51) Afterwards, the signal is transmitted through via 400 which may be a copper rod of 1.5 mm radius to the bottom uniform switching port system as shown in FIG. 4. This system consists of arms 410-413, which may be uniform in construction. For this particular exemplar, each of them is composed of a 35.35 Ohm transmission line TL4 (430A-430D) connected to a reconfigurable shunt stub stp (420-423) and a 50 Ohm transmission line TL5 (440A-440D), that ends to a 50 Ohm RF port Pn (450A-450D).

(52) The transmission line TL4 (430A-430D) serves to impedance match the previous line TL3 to the next line TL5. At the end section of TL4, the reconfigurable shunt stub is implemented to serve as an enabled RF choke to allow or block the power to be distributed to the RF port. In this case, as shown for arm 410 as the exemplar, each reconfigurable shunt stub 420 is comprised of a dc line 462, an inductor 463, and a diode dpn 464. The other arms of the system are similarly configured.

(53) The state (ON/OFF) of the diode activates or deactivates respectively the RF choke into the arm. When the diode is on, the RF choke function is active and no RF reaches the port. When the diode is off, RF reaches the port.

(54) The RF choke may be also achieved with a series configuration by having an RF switch to connect the two transmission lines TL4 and TL5, implemented at a distance that creates a virtual open load at the OFF state of the switch.

(55) The choice between the two configurations of implementing the RF choke, series or shunt, depends on the active element characteristics, such as insertion loss and isolation at the ON and OFF states respectively. If more ports are requested, these are included maintaining the uniform system pattern 500 as shown in FIG. 5, with the addition of the proper reconfigurable matching stubs at the top network.

(56) The circuitry's reconfigurable condition for proper operation is provided in Table 1, showing the necessary diodes' state, OFF or ON, in respective binary form 0 or 1. As shown, all ports can be enabled alone or in combination with other ports, by activating the associate tuning stub. For instance, if two ports are desired to be enabled, tuning stub St2 is active to set this condition.

(57) In case one port is enabled, then it receives all the supplied power RFin from the P0 port; if more than one port is enabled, the supplied power is equally shared among them in the same phase, while maintaining input matching. The simulated (in HFSS) reflection coefficient and signal phase at each port, are depicted in FIGS. 6 and 7, respectively. The two figures illustrate four cases: plot (a) includes one port enabled; plot (b) has two ports enabled; plot (c) has three ports enabled; plot (d) has four ports enabled. Individual combinations of each port for the above cases are not shown because the electromagnetic response remains the same thanks to the uniform pattern of the network. For instance, in the case of two-port enabled, the individual combination 0011 (P.sub.4P.sub.3P.sub.2P.sub.1) has a similar response (s-parameters—magnitude and phase) with 0110 or 1100 or 1001 or 1010 or 0101. As seen in the S-parameter figure (FIG. 6), the circuitry has an input reflection coefficient always less than −20 dB with isolation towards the disabled ports to exceed 24 dB. The insertion loss is noticed to be almost 1 dB in each case due to non-ideal active elements implemented in the system and the dielectric losses. Specifically, the transmission coefficient (TC) for each case at center frequency Fc=10 GHz is as next: for single port enabled is −1.1 dB (ideal 0 dB); for two ports enabled, TC is −3.9 dB (ideal −3 dB); for three ports enabled, TC is −5.7 dB (ideal −4.7 dB); for four ports enabled, TC is −7 dB (ideal −6 dB).

(58) TABLE-US-00001 TABLE 1 St.sub.2 St.sub.1 P.sub.4 P.sub.3 P.sub.2 P.sub.1 0 0 0 0 0 1 0 0 0 0 1 0 1 0 0 0 1 1 0 0 0 1 0 0 1 0 0 1 0 1 1 0 0 1 1 0 0 1 0 1 1 I 0 0 1 0 0 0 1 0 1 0 0 1 1 0 1 0 1 0 0 1 1 0 1 1 1 0 1 1 0 0 0 I 1 1 0 1 0 1 1 1 1 0 0 1 1 1 1 1

(59) The electromagnetic balanced behavior of the system is seen in FIGS. 6 and 7, where the graphs representing the enabled ports are identical. Similarly, the disabled ports have identical response with each other too. Therefore, the designed reconfigurable independent active-port switch can be used to form single RF-port array antennas, able to activate and deactivate radiating elements. Moreover, active and passive components such as power amplifiers, RF switches, phase shifters, attenuators, couplers, etc., can be implemented at the output ports of the suggested 1 to N RF switch, forming for instance a phased array antenna without the necessary implementation of transceivers to control individually each radiating element.

(60) As shown in FIGS. 8A and 8B, cube antenna array 800 is able to cover four 90° degree sectors 810-813. FIG. 8A shows the arrange of the sectors. Each sector of the antenna consists of four planar arrays 910-913 enclosing the reconfigurable feeding network to compose a concise device, covering an area of 27 mm×27 mm×27 mm.

(61) The switching ports described previously are now extended to the feeding port of the four planar arrays that are aligned orthogonally with each other to form the cube. Each planar array has a stack topology with the radiating elements located at the top layer 900 (a 0.5 mm thick RO3003 substrate, ε.sub.r=3, tan δ=0.0013) and the feeding network 921 located at the bottom layer 920 (a 0.25 mm thick RT6006 substrate), separated by a common ground 930 to improve isolation, as seen in FIG. 9B.

(62) The radiating elements that compose the array are rectangular truncated patches aligned sequentially and fed through VIAs (copper rods) by a sequentially rotated power divider. The divider delivers equal power in a consecutive phase difference (90° degrees at Fc=10 GHz) between the elements, as seen in FIGS. 10A and 10B. The performance of the planar array alone is depicted in FIGS. 11A and 11B, with an input reflection coefficient better than −30 dB and a RHCP realized gain to reach 9 dBic at the Fc; cross-polarization (LHCP) is −30 dB.

(63) The unique performance that the reconfigurable switching system provides to an antenna application is shown in FIGS. 12-15. The reflection coefficient of the cube antenna in FIG. 12, proves the good operating frequency range (9.5-10.5 GHz) for the four enabled port cases. The radiation pattern of the fifteen alternative cases is shown in FIGS. 13-15, demonstrating the beam diversity of the antenna that covers the four 90°-degree sectors. The figures include the co and cross-polarization gain, where the 3 dB beamwidth coverage is 61° degrees (FIG. 13) for one port enabled; 150° (FIG. 14) for two-port enabled; 245.5° degrees for three ports enabled and 360° degrees for four ports enabled (FIG. 15).

(64) Inexpensive and simple antennas like the present invention with independent multiple beam steering are novel designs thanks to the newly introduced mechanism they are driven by. Similarly, the reconfigurable tuning network can be used to approach different reconfigurable antenna models such as polarization diverse, frequency diverse, or a combination of other radiating characteristics.

(65) While the foregoing written description enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The disclosure should therefore not be limited by the above-described embodiments, methods, and examples, but by all embodiments and methods within the scope and spirit of the disclosure. In addition, to the above description, the materials attached hereto form part of the disclosure of this provisional patent application.