Apparatus with rectangular waveguide to radial mode transition

An apparatus with a rectangular waveguide to radial mode transition and method for using the same are described. In one embodiment, the apparatus comprises a radial waveguide having at least one plate; a radio-frequency (RF) launch coupled to the radial waveguide comprising a rectangular waveguide, a rectangular waveguide to coaxial transition coupled to the rectangular waveguide, and a coaxial to radial transition coupled to the rectangular waveguide to coaxial transition.

FIELD OF THE INVENTION

Embodiments of the present invention relate to the field of wireless communication; more particularly, embodiments of the present invention relate to antennas having a radio-frequency (RF) launch with a transition between two modes of RF transmission.

BACKGROUND OF THE INVENTION

High gain antennas, used in applications such as satellite communications (SATCOM), or line-of-sight (LOS) communications links, require large aperture areas to achieve sufficiently high gains. The gains for the antennas are often achieved by directing RF energy to an antenna feed.

One problem with a conventional antenna feed is that each of the components, e.g., input section, polarizer, is generally constructed as a separate component. For example, in some antennas, the antenna input is a commercial SMA connector and the interface to the diplexer is via a waveguide, which necessitates a commercial waveguide to SMA adapter. Thus, an extra piece of hardware is needed to transition between coax and a waveguide.

The assembly, testing and fine tuning of such separately manufactured antenna feeds results in significant labor and manufacturing cost, long fabrication and test times, and potential for high variability of antenna performance between units.

SUMMARY OF THE INVENTION

An apparatus with a rectangular waveguide to radial mode transition and method for using the same are described. In one embodiment, the apparatus comprises a radial waveguide having at least one plate; a radio-frequency (RF) launch coupled to the radial waveguide comprising a rectangular waveguide, a rectangular waveguide to coaxial transition coupled to the rectangular waveguide, and a coaxial to radial transition coupled to the rectangular waveguide to coaxial transition.

DETAILED DESCRIPTION

An antenna having a radio-frequency (RF) launch with a transition between two modes of RF energy propagation and a method of using the same are disclosed. The transition provides a transformation between two modes of RF energy propagation. In one embodiment, the mode transformation is between a rectangular waveguide mode and radial propagating mode for the antenna. In one embodiment, the rectangular waveguide mode is a waveguide TE10 mode.

In one embodiment, the antenna comprises a metamaterial surface antenna having a cylindrical feed, such as described, for example, in more detail below. In one embodiment, the antenna elements of such an antenna is fed with RF energy from the RF launch with a radial propagating mode, and the RF energy is fed into the RF launch via a rectangular waveguide which is driven by commercial diplexers and RF amplification circuits.

Embodiments of the RF launch described herein have one or more advantages. One or more advantages include that the transition allows a more integrated waveguide structure with fewer discrete parts, a more compact assembly and a repeatable assembly process. That is, the RF launch disclosed herein eliminates the waveguide to SMA adapter of the prior art and changes the antenna input to the waveguide to interface directly to a diplexer. Embodiments of the RF launch also lower the loss of using more discrete components, e.g. waveguide to SMA transition, then SMA to radial transition.

Transition from TE10 Rectangular Waveguide (Mode) to Radial Propagating Mode

FIG. 1illustrates one embodiment of an antenna RF launch with a two-mode transition between two modes of RF energy propagation, namely a rectangular waveguide (mode) to a radial propagating mode. In one embodiment, the antenna includes a radial waveguide having at least one plate. In one embodiment, the radial waveguide is a parallel plate waveguide such as shown inFIGS. 2A and 2BorFIG. 10.

Referring toFIG. 1, the RF launch101is coupled to the radial waveguide (not shown) and comprises a coaxial to radial transition103, a rectangular waveguide to coaxial stepped transition102coupled to coaxial to radial transition103, and a rectangular waveguide coupled to rectangular waveguide to coaxial stepped transition102via rectangular waveguide interface105. In one embodiment, the coaxial to radial transition103comprises an interface shaped into concentric tiers. In one embodiment, the parts of RF launch101operate together to improve, or even maximize, the transfer of energy, while reducing, or even minimizing, RF energy reflection.

In one embodiment, the rectangular waveguide has a radial non-symmetric mode and coaxial to radial transition103has a radial symmetric mode. The radial and coaxial modes of RF propagation are shown inFIGS. 3A and 3B, respectively. In both modes, the direction of propagation is traverse to the polarization of the electric field.FIG. 3Cillustrates the direction of propagation in a rectangular (e.g., TE10) waveguide. Referring toFIG. 3C, the electric field from one broad wall to the other is vertically polarized, with the direction of propagation being transverse to that.

As shown in greater detail below, in one embodiment, the rectangular waveguide to coaxial stepped transition102is coupled to the rectangular waveguide at a 90° angle. This is advantageous as the transition is low profile and the match is in a direction normal to the launch interface. However, in alternative embodiments, the coupling can be at an angle other than a 90° angle.

In one embodiment, the coaxial to radial transition103has a coaxial waveguide dielectric104that surrounds the coupling between coaxial to radial transition103and rectangular waveguide to coaxial stepped transition102. In one embodiment, coaxial waveguide dielectric104has a dielectric constant that is higher than air.

In one embodiment, the rectangular waveguide to coaxial stepped transition102is coupled to the coaxial to radial transition103via a pin (e.g., a press fit pin). In one embodiment, the coaxial to radial transition103has the pin and the pin is fit in a pin receptacle of rectangular waveguide to coaxial stepped transition102. In one embodiment, the coaxial waveguide dielectric104is configured to maintain the pin of the coaxial to radial transition103in a centered (perpendicular) position with respect to the coaxial to radial transition103.

FIGS. 2A and 2Billustrate a side view of one embodiment of an antenna containing an RF launch, such as described, for example, inFIG. 1. Referring toFIGS. 2A and 2B, antenna200includes a radial waveguide201, an aperture consisting of a substrate or glass layers (panels)202with antenna elements (not shown), a ground plane203, a dielectric (or other layer) transition204, an RF launch (feed)205and a termination206. Note that while in one embodiment glass layers202comprises two glass layers, in other embodiments, the radiating aperture comprises only one glass layer or a substrate with only one layer. Alternatively, the radiating aperture comprises more than two layers that operate together to radiate RF energy (e.g., a beam).

In one embodiment, the aperture consisting of glass layers (substrate)202with antenna elements is operable to radiate radio frequency (RF) signals in response to an RF feed wave fed from RF launch205that travels from the central location of RF launch205along radial waveguide201around ground plane203(that acts as a guide plate) and 180° layer transition210to glass layers202to radiating aperture at the top portion of antenna200. Using the RF energy, the antenna elements of glass layers202radiate RF energy. In one embodiment, the RF energy radiated by glass layers in response to the RF energy from the feed wave is in the form of a beam.

In one embodiment, glass layers (or other substrate)202is manufactured using commercial television manufacturing techniques and does not have electrically conductive metal at the most external layer. This lack of conductive media on the external layer of the radiating aperture prevents a physical electrical connection between the subassemblies without further invasive processing of the subassemblies. To provide a connection between glass layers202that form the radiating aperture and waveguide201that feeds the feed wave to glass layers202, an equivalent RF connection is made to prevent radiation from the connection seam. That is, RF choke assembly RF choke220is operable to block RF energy from exiting through a gap between outer portions of waveguide201and glass layers202that form the radiating aperture. In addition, the difference in the coefficient of thermal expansion of glass layers202and feed structure material of waveguide201necessitates the need for an intermediate low-friction surface to ensure free planar expansion of the antenna media.

Because the glass layers202forming the radiating aperture and waveguide housing are made of different materials with different coefficients of thermal expansion, there is some accommodation made at the extents of the housing of waveguide201to allow for physical movement as temperatures vary. To allow for free movement of glass layers202and waveguide201housing without physically damaging either structure, the glass layers202are not permanently bonded to waveguide201. In one embodiment, glass layers202are held mechanically in close intimate contact with waveguide201by clamping type features. That is, to hold glass layers202generally in position with respect to waveguide201in view of their differences in the coefficient of thermal expansion, a clamping mechanism is included.

In one embodiment, beneath the clamp features are materials to isolate the clamp from glass layers202(i.e., foam, additional thin film or both). An intermediate material with lower friction resistance is added between the aperture and feed to act as a slip plane. The slip plane allows the glass to move laterally. In one embodiment, as discussed above, this may be useful for thermal expansion or thermal mismatch between layers.FIG. 2Aillustrates an example of the slip plane location211.

In one embodiment, the material is thin film in nature and of a plastic material such as, for example, Acrylic, Acetate, or Polycarbonate and is adhered to the underside of the glass or top of the housing of waveguide201. In addition to cushioning glass layers202and providing a slip plane to waveguide201, the thin sheet material when attached to the glass provides some additional structural support and scratch resistance to the glass. The attachment may be made using an adhesive.

In one embodiment, the radial feed is designed such that each individual component can operate over a large bandwidth, i.e., >50% bandwidth. The constituent components that make up the feed are: RF launch205, 180° layer transition210, termination206, intermediate ground plane203(guide-plate), the dielectric loading of dielectric transition204, and RF choke assembly220.

In one embodiment, RF launch205has a stepped transition from the input (co)axial mode (direction of propagation is through the conductor) to the radial mode (direction of propagation of the RF wave occurs from the edges of the conductor toward its center). This transition shorts the input pin to a capacitive step that compensates for the probe inductance, then impedance steps out to the full height of radial waveguide201. The number of steps needed to transition is related to the desired bandwidth of operation and the difference between the initial impedance of the launch and the final impedance of the guide. For example, in one embodiment, for a 10% change in bandwidth, a one-step transition is used; for a 20% change in bandwidth, a two-step transition is used; and for a 50% change in bandwidth, a three (or more) step transition is used.

Shorting the pin to ground plane203(the top plate of waveguide201) allows for higher operating power levels by conducting generated heat away from the center pin of RF launch205into the housing of waveguide201which in one embodiment is metal (e.g., aluminum, copper, brass, gold, etc.). Any risk of dielectric breakdown is reduced by controlling the gaps between the stepped RF launch205and the bottom of the housing of waveguide201and breaking the sharp edges at the impedance steps.

The top termination transition of RF launch205is designed in the same manner with impedance compensation added for the presence of the slow wave dielectric material. By designing the impedance transitions using discrete steps, RF launch205is easily manufactured using a three-axis computer numeric control (CNC) end mil.

In one embodiment, 180° layer transition210is accomplished in a similar manner to the launch and termination design. In one embodiment, a chamfer or single step is used to compensate for the inductance of the 90° bends. In another embodiment, multiple steps are used and can individually be tuned to accomplish a broadband match. In one embodiment, the slow wave dielectric transition204of the top waveguide is placed at the top 90° bend, thus adding asymmetry to the full 180° transition. This dielectric presence can be compensated for by adding asymmetry to the top and bottom transition steps.

The equivalent RF grounding connection is accomplished by adding RF choke assembly220to the feed waveguide/glass interface such that the RF energy within the intended frequency band is reflected from RF choke assembly220interface without radiating into free space, and in-turn adding constructively with the propagating feed signal. In one embodiment, these chokes are based on traditional waveguide choke flanges that help ensure robust RF connection for high power applications. Such chokes may also be based on electromagnetic band gap (EBG) structures as described in further detail below. Several RF chokes can be added in series to provide a broadband choke arrangement for use at transmit and receive bands simultaneously.

In one embodiment, RF choke assembly220includes waveguide style chokes having one or more slots, or channels, that are integrated into waveguide201.FIGS. 2A and 2Billustrate two slots. Note that in one embodiment as waveguide201is radial, the slots are rings that are inside the top of waveguide201. In one embodiment, the slots are designed to be placed at an odd integer multiple of a quarter wavelength (e.g., ¼, ¾, 5/4, etc.) from the inside of the RF feed junction (i.e., the outer most edge of the inner portion of waveguide201through which the feed wave propagates, shown as inner edge250inFIG. 2A). In one embodiment, the choke channels are also one quarter of a wavelength deep such that the reflected power is in phase at the top of the choke channel. In one embodiment, the total phase length of the choke assembly will in turn be out of phase with the propagating feed signal, which gives the choke assembly (e.g., between the top and bottom of the slot(s)) the equivalent RF performance of an electrical short. This electrical short equivalence maintains the continuity of the feed structure walls without the need for a physical electrical connection.

Note that two choke slots (channels) may be used for each frequency band of the feed wave. For example, two choke slots may be used for one receive frequency band while another two slots are used for a different receive frequency band or a transmit frequency band. For example, transmit and receive frequency bands may be Ka transmit and receive frequency bands, respectively. For another example, the two receive frequency bands may be the Ka and Ku frequency bands, or any band in which communication occurs. The spacing of the slots is the same as above. That is, the slots would be designed to be placed at an odd integer multiple of a quarter wavelength (e.g., ¼, ¾, 5/4, etc.) from the inside of the RF feed junction (e.g., inner edge250) to create a low impedance short. In one embodiment, the slots of ¼λ deep with a width sized for high impedance (where the λ is that of the frequency to be blocked). While each of the slots resonate at one frequency (to block energy at that frequency), the choke will likely block a band of frequencies. For example, while the slots resonate at one frequency of the Ku band, the choke covers the entire Ku band.

Cross-Section Views of RF Launch

FIG. 4illustrates cross-section view of one embodiment of an RF launch in relation to the waveguide of one embodiment of an antenna. The antenna may be any flat panel antenna, including, for example, those described in more detail below.

Referring toFIG. 4, coaxial to radial transition103is coupled to a rectangular waveguide to coaxial transition102. In one embodiment, rectangular waveguide to coaxial transition102comprises a rectangular waveguide to coaxial stepped transition102. Rectangular waveguide to coaxial transition102is coupled to rectangular waveguide401. Coaxial to radial transition103is coupled to the waveguide of an apparatus. In one embodiment, the apparatus comprises an antenna, such as, for example, the antenna shown inFIGS. 2A and 2Bor an antenna described in more detail herein. In one embodiment, coaxial to radial transition103has a coaxial transmission line with a dielectric constant that is higher than air

The coaxial transmission line dielectric104is shown surrounding the coaxial interface between coaxial to radial transition103and a rectangular waveguide to coaxial stepped transition102. In one embodiment, coaxial transmission line dielectric104is polytetraflouroethylene (PTFE).

In one embodiment, the top of coaxial to radial transition103aligns with the ground plane of the bottom plate/layer402of a parallel plate waveguide.

FIG. 5Aillustrates one embodiment of a rectangular waveguide to coaxial stepped transition. Referring toFIG. 5A, the rectangular waveguide to coaxial stepped transition includes three steps. In an alternative embodiment, the rectangular waveguide to coaxial stepped transition has as stepped structure500and a pin receptacle501. In one embodiment, stepped structure500is coupled to pin receptacle501via a solder joint (e.g., solder joint503ofFIG. 5D).

In one embodiment, stepped structure500includes three steps. In an alternative embodiment, stepped structure500includes four steps. The number of steps may be greater than four or less than three. The number of steps and step size is selected based on the frequency of the RF energy propagating through the rectangular waveguide to coaxial stepped transition to achieve no more than a predetermined amount of loss and no more than a predetermined amount of reflection. In one embodiment, each step has a capacitive component and an inductive component that can be set in a well-known manner through circuit modeling to set the length and width of the steps to achieve a desired amount of energy transfer and reduced reflection. Note that the number of steps increases if a larger bandwidth is desired.

In one embodiment, the stepped structure is made from brass. However, any good conductor may be used, such as, for example, copper, aluminum, or any other easily-machined, yet high-conductivity metal.

Pin receptacle501is designed to receive a pin of the coaxial to radial transition103, such as shown pin502inFIG. 5B. In one embodiment, pin502is a split, or press fit pin. In one embodiment, pin receptacle is made from a highly conductive material, such as, a metallic material like, for example, Beryllium copper (gold plated), aluminum, magnesium, etc.

FIG. 5Billustrates one embodiment of a coaxial to radial transition. Referring toFIG. 5B, pin502includes a lip that has an extra width. In other words, pin502has a first, smaller width at the end that is inserted into the pin receptacle of the rectangular waveguide to coaxial stepped transition than the width of pin502closer to the body of the coaxial to radial transition. In one embodiment, the width of the lip is the same diameter as that of the receptacle. However, this is not required. A larger lip may provide more mechanical strength for the pin since the part connecting to the coaxial to radial transition has a larger diameter. A larger lip might help the transfer of heat from the pin to the coaxial to radial transition for very high power scenarios. In one embodiment, the lip (and its associated extra width) is not included, so that pin502has the same uniform width.

FIG. 5Cillustrates the coupling of the coaxial to radial transition and the rectangular waveguide to coax stepped transition. Referring toFIG. 5C, pin502of the coaxial to radial transition is inserted in pin receptacle501of the rectangular waveguide to coaxial stepped transition. In one embodiment, pin502slides in and out of pin receptacle501due to thermal expansion during antenna operation. Thus, the coupling of the coaxial to radial transition and the rectangular waveguide to coaxial stepped transition is not via solder or any other attachment mechanism that prevents pin502from sliding in and out of pin receptacle501.

FIG. 5Dillustrates the coaxial to radial transition coupled to the rectangular waveguide to coaxial stepped transition.

FIGS. 5E and 5Fillustrate one embodiment of the rectangular waveguide interface. Referring toFIGS. 5E and 5F, the rectangular waveguide interface includes an O-ring groove510and a slot to the rectangular waveguide to coaxial stepped transition102. In one embodiment, a coaxial interface511between the rectangular waveguide to coaxial stepped transition102and the coaxial to radial transition has a PTFE (or other insulating material) insert (coaxial dielectric)512. Other materials may be used in place of Teflon. In one embodiment, the coaxial dielectric512has a higher dielectric than air and keeps the pin (e.g., pin502of depicted inFIGS. 5B and 5C) centered with respect to its connection between the coaxial to radial transition and the rectangular waveguide to coaxial stepped transition and with respect its interface on the coaxial to radial transition.

In an alternative embodiment, rather than metallic pins and machined metal transitions, circuit boards are used to transition from waveguide to radial mode (i.e., two modes of RF propagation). In such a case, the circuit board replaces the coaxial center conductor, the stepped transitions of the waveguide and the radial transition.

FIGS. 6A and 6Billustrate alternative embodiments of a launch for the coaxial to radial transition.FIG. 6Aillustrates a 90° bend, stepped launch601with 4 steps. In one embodiment, stepped launch601has a return loss greater than 25 dB from 11 GHz to 14 GHz. Note that the number of steps may be more or less than four.FIG. 6Billustrates a 90° bend, ramped launch. Referring toFIG. 6B, ramped launch602includes a linear sweep profile. In one embodiment, ramped launch602has a return loss greater than 20 dB over a 10 GHz to 14.85 GHz band. The size of the ramp, including the length of the ramp and its height, to achieve the desired return loss and reflection profiles.

FIG. 15illustrates one embodiment of an alternative RF launch with a metallic radial stub. Referring toFIG. 15, a radial waveguide1501is coupled to lower metal waveguide1504. A transition substrate1503is shown between radial waveguide1501is coupled to lower metal waveguide1504. A pin1505is used to transfer RF energy to radial stub1502, which transfers the energy into radial waveguide1501. In one embodiment, there is a single step to radial stub1502. In alternative embodiments, there are multiple steps to the radial stub. Note that in one embodiment, a coaxial dielectric, such as, for example, described above, is around pin1505.

The probe, pin1505, extruding from the coax creates a time-varying electric field which propagates down the radial waveguide1501. In one embodiment, radial stub1502is etched or attached to the top of pin1505and the substrate transition1503aka a dielectric jacket

In one embodiment, the wave impedance (Zw) coming from the coax is primarily inductive and 50 Ohms and radial waveguide1501is capacitive with low impedance as give by the equation immediately below:

Therefore, in such a case, transition1503transforms the wave impedance from inductive to capacitive and a 50 ohm impedance to the impedance of a radial waveguide (radial waveguide, Z<<impedance of coax, 50 Ohms).

Radial stub1502increases the capacitance of the transition from the coax (which is primarily inductive) to provide a better match as the wave needs to be more capacitive to account for the impedance of the radial waveguide.

The increased area provided by radial stub1502increases the capacitance of the transition such as provided with the equation below:

As can be seen from this equation, the distance from the top of the waveguide to pin1502should be decreased in increase capacitance, and due to manufacturing limitations this value should be as high as possible.

To shorten pin1505to a manufacturable and repeatable length (decreasing ‘distance’), one can add a higher dielectric material (increasing ε0) to increase the capacitance—this was done with the substrate transition1503.

In one embodiment, rexolite/polystyrene is used for substrate transition1503(dielectric constant=2.53) because it's low loss, plentiful, cheap, and structurally rigid (easy to manufacture and add features).

Having a dielectric layer above pin1505could also improve capacitance (improve match as well). Alternatively, if there are mechanical limitations, in one embodiment, air is used.

In addition to the single stub, additional steps below pin1505could be added to create a better match and increase bandwidth.

In one embodiment, transition substrate1503has a combination of substrates with different dielectric constants to provide better matching.

FIG. 16illustrates one embodiment of an alternative RF launch with a waveguide stepped transition. Referring toFIG. 16, a radial waveguide1601is coupled to lower metal waveguide1602. A transition substrate1603is shown between radial waveguide1601is coupled to lower metal waveguide1602. A pin1604is used to transfer RF energy to into radial waveguide1601. A number of steps1605are embedded in the waveguide that lead up to radial waveguide1601. Note that in one embodiment, a coaxial dielectric, such as, for example, described above, is around pin1604.

The probe, pin1604, extruding from the coax creates a time-varying electric field which propagates down the radial waveguide1601.

In the RF launch1600, the steps that lead up to radial waveguide1601and substrate transition1603aka a dielectric jacket are important. As described previously, a goal of the RF launch is to create a transition that is capacitive and low impedance in order to match the impedance of radial waveguide1601.

In one embodiment, to increase the capacitance and decrease impedance, there are three features taking place pin1604, transition steps, and a dielectric jacket. Pin1604works by creating the time-varying E-field and the top adds capacitance set by its distance from the top of the waveguide. The dielectric jacket helps by adding capacitance and preventing the necessity of pin1604being too close to the top of the waveguide. The air pocket above and around pin1604serves the purpose of tuning the capacitance in a small, fine-tune way. The steps work by transitioning the coax impedance to the radial waveguide impedance.

In one embodiment, the steps allow for gradual radial waveguide height transition to the desired radial waveguide height—this height (and length) determines the radial waveguide characteristic impedance which is <<coax impedance. In other words, in one embodiment, the first step sets the starting impedance for approximately 1 wavelength and the following steps act as a quarter-wave transition to the desired characteristic impedance (see the equation below)

The steps also offer higher bandwidth, such that the more steps the higher the bandwidth

Length of first transition step,L˜λ0*√{square root over (μr/εr)}

One could also add a radial stub (similar toFIG. 15discussed before) to pin1604to create a better match (increase capacitance) and increase bandwidth.

With respect to the dielectric jacket, its purpose is to decrease the height of pin1604so it will not have to be so close to the top of radial waveguide1601. Since the transition is going form a inductance (coax) to capacitance (parallel plate) there needs to be a high level of capacitance. One way of obtaining that is a large area with a low distance to the top of radial waveguide1601, such as provided with the equation below:

A purpose behind the airgap on top is mechanical limitations in the construction of the rexolite and pin1604. If there was no air, the rexolite is difficult to manufacture and build, and the pin length and accuracy would need to be <+/−0.5 mil.

Note that the techniques described herein are not limited to coaxial transitions. Other transitions may be used, such as, for example, a stripline transition may be used. In such a case, the rectangular waveguide to coaxial transition and the coaxial to radial transition are replaced with a rectangular waveguide to stripline transition and a stripline to radial transition, respectively.FIG. 17illustrates one embodiment of an RF launch with a stripline transition. Referring toFIG. 17, a metallic stripline on a printed circuit board (PCB) transitions RF energy from a rectangular waveguide to a radial waveguide via a transition substrate.

In the description that follows, a number of example antenna embodiments are disclosed that could use any of the RF launch embodiments described above to transfer RF energy. However, even though the focus in the description is on such antenna embodiments, it should be known that that the waveguide to radial mode transitions described above may be used in other RF components such as, for example, but not limited to, splitters, diplexers, etc.

Examples of Antenna Systems

In one embodiment, the flat panel antenna with the RF launch described above is part of a metamaterial antenna system. Embodiments of a metamaterial antenna system for communications satellite earth stations are described. In one embodiment, the antenna system is a component or subsystem of a satellite earth station (ES) operating on a mobile platform (e.g., aeronautical, maritime, land, etc.) that operates using either Ka-band frequencies or Ku-band frequencies for civil commercial satellite communications. Note that embodiments of the antenna system also can be used in earth stations that are not on mobile platforms (e.g., fixed or transportable earth stations).

In one embodiment, the antenna system uses surface scattering metamaterial technology to form and steer transmit and receive beams through separate antennas. In one embodiment, the antenna systems are analog systems, in contrast to antenna systems that employ digital signal processing to electrically form and steer beams (such as phased array antennas).

In one embodiment, the antenna system is comprised of three functional subsystems: (1) a wave guiding structure consisting of a cylindrical wave feed architecture; (2) an array of wave scattering metamaterial unit cells that are part of antenna elements; and (3) a control structure to command formation of an adjustable radiation field (beam) from the metamaterial scattering elements using holographic principles.

Antenna Elements

FIG. 7Aillustrates the schematic of one embodiment of a cylindrically fed holographic radial aperture antenna. Referring toFIG. 7A, the antenna aperture has one or more arrays651of antenna elements653that are placed in concentric rings around an input feed652of the cylindrically fed antenna. In one embodiment, antenna elements653are radio frequency (RF) resonators that radiate RF energy. In one embodiment, antenna elements653comprise both Rx and Tx irises that are interleaved and distributed on the whole surface of the antenna aperture. Examples of such antenna elements are described in greater detail below. Note that the RF resonators described herein may be used in antennas that do not include a cylindrical feed.

In one embodiment, the antenna includes a coaxial feed that is used to provide a cylindrical wave feed via input feed652. In one embodiment, the cylindrical wave feed architecture feeds the antenna from a central point with an excitation that spreads outward in a cylindrical manner from the feed point. That is, a cylindrically fed antenna creates an outward travelling concentric feed wave. Even so, the shape of the cylindrical feed antenna around the cylindrical feed can be circular, square or any shape. In another embodiment, a cylindrically fed antenna creates an inward travelling feed wave. In such a case, the feed wave most naturally comes from a circular structure.

In one embodiment, antenna elements653comprise irises and the aperture antenna ofFIG. 7Ais used to generate a main beam shaped by using excitation from a cylindrical feed wave for radiating irises through tunable liquid crystal (LC) material. In one embodiment, the antenna can be excited to radiate a horizontally or vertically polarized electric field at desired scan angles.

In one embodiment, the antenna elements comprise a group of patch antennas. This group of patch antennas comprises an array of scattering metamaterial elements. In one embodiment, each scattering element in the antenna system is part of a unit cell that consists of a lower conductor, a dielectric substrate and an upper conductor that embeds a complementary electric inductive-capacitive resonator (“complementary electric LC” or “CELC”) that is etched in or deposited onto the upper conductor. As would be understood by those skilled in the art, LC in the context of CELC refers to inductance-capacitance, as opposed to liquid crystal.

In one embodiment, a liquid crystal (LC) is disposed in the gap around the scattering element. This LC is driven by the direct drive embodiments described above. In one embodiment, liquid crystal is encapsulated in each unit cell and separates the lower conductor associated with a slot from an upper conductor associated with its patch. Liquid crystal has a permittivity that is a function of the orientation of the molecules comprising the liquid crystal, and the orientation of the molecules (and thus the permittivity) can be controlled by adjusting the bias voltage across the liquid crystal. Using this property, in one embodiment, the liquid crystal integrates an on/off switch for the transmission of energy from the guided wave to the CELC. When switched on, the CELC emits an electromagnetic wave like an electrically small dipole antenna. Note that the teachings herein are not limited to having a liquid crystal that operates in a binary fashion with respect to energy transmission.

In one embodiment, the feed geometry of this antenna system allows the antenna elements to be positioned at forty-five degree (45°) angles to the vector of the wave in the wave feed. Note that other positions may be used (e.g., at 40° angles). This position of the elements enables control of the free space wave received by or transmitted/radiated from the elements. In one embodiment, the antenna elements are arranged with an inter-element spacing that is less than a free-space wavelength of the operating frequency of the antenna. For example, if there are four scattering elements per wavelength, the elements in the 30 GHz transmit antenna will be approximately 2.5 mm (i.e., ¼th the 10 mm free-space wavelength of 30 GHz).

In one embodiment, the two sets of elements are perpendicular to each other and simultaneously have equal amplitude excitation if controlled to the same tuning state. Rotating them +/−45 degrees relative to the feed wave excitation achieves both desired features at once. Rotating one set 0 degrees and the other 90 degrees would achieve the perpendicular goal, but not the equal amplitude excitation goal. Note that 0 and 90 degrees may be used to achieve isolation when feeding the array of antenna elements in a single structure from two sides.

The amount of radiated power from each unit cell is controlled by applying a voltage to the patch (potential across the LC channel) using a controller. Traces to each patch are used to provide the voltage to the patch antenna. The voltage is used to tune or detune the capacitance and thus the resonance frequency of individual elements to effectuate beam forming. The voltage required is dependent on the liquid crystal mixture being used. The voltage tuning characteristic of liquid crystal mixtures is mainly described by a threshold voltage at which the liquid crystal starts to be affected by the voltage and the saturation voltage, above which an increase of the voltage does not cause major tuning in liquid crystal. These two characteristic parameters can change for different liquid crystal mixtures.

In one embodiment, as discussed above, a matrix drive is used to apply voltage to the patches in order to drive each cell separately from all the other cells without having a separate connection for each cell (direct drive). Because of the high density of elements, the matrix drive is an efficient way to address each cell individually.

In one embodiment, the control structure for the antenna system has 2 main components: the antenna array controller, which includes drive electronics, for the antenna system, is below the wave scattering structure, while the matrix drive switching array is interspersed throughout the radiating RF array in such a way as to not interfere with the radiation. In one embodiment, the drive electronics for the antenna system comprise commercial off-the shelf LCD controls used in commercial television appliances that adjust the bias voltage for each scattering element by adjusting the amplitude or duty cycle of an AC bias signal to that element.

In one embodiment, the antenna array controller also contains a microprocessor executing the software. The control structure may also incorporate sensors (e.g., a GPS receiver, a three-axis compass, a 3-axis accelerometer, 3-axis gyro, 3-axis magnetometer, etc.) to provide location and orientation information to the processor. The location and orientation information may be provided to the processor by other systems in the earth station and/or may not be part of the antenna system.

More specifically, the antenna array controller controls which elements are turned off and those elements turned on and at which phase and amplitude level at the frequency of operation. The elements are selectively detuned for frequency operation by voltage application.

For transmission, a controller supplies an array of voltage signals to the RF patches to create a modulation, or control pattern. The control pattern causes the elements to be turned to different states. In one embodiment, multistate control is used in which various elements are turned on and off to varying levels, further approximating a sinusoidal control pattern, as opposed to a square wave (i.e., a sinusoid gray shade modulation pattern). In one embodiment, some elements radiate more strongly than others, rather than some elements radiate and some do not. Variable radiation is achieved by applying specific voltage levels, which adjusts the liquid crystal permittivity to varying amounts, thereby detuning elements variably and causing some elements to radiate more than others.

The generation of a focused beam by the metamaterial array of elements can be explained by the phenomenon of constructive and destructive interference. Individual electromagnetic waves sum up (constructive interference) if they have the same phase when they meet in free space and waves cancel each other (destructive interference) if they are in opposite phase when they meet in free space. If the slots in a slotted antenna are positioned so that each successive slot is positioned at a different distance from the excitation point of the guided wave, the scattered wave from that element will have a different phase than the scattered wave of the previous slot. If the slots are spaced one quarter of a guided wavelength apart, each slot will scatter a wave with a one fourth phase delay from the previous slot.

Using the array, the number of patterns of constructive and destructive interference that can be produced can be increased so that beams can be pointed theoretically in any direction plus or minus ninety degrees (90°) from the bore sight of the antenna array, using the principles of holography. Thus, by controlling which metamaterial unit cells are turned on or off (i.e., by changing the pattern of which cells are turned on and which cells are turned off), a different pattern of constructive and destructive interference can be produced, and the antenna can change the direction of the main beam. The time required to turn the unit cells on and off dictates the speed at which the beam can be switched from one location to another location.

In one embodiment, the antenna system produces one steerable beam for the uplink antenna and one steerable beam for the downlink antenna. In one embodiment, the antenna system uses metamaterial technology to receive beams and to decode signals from the satellite and to form transmit beams that are directed toward the satellite. In one embodiment, the antenna systems are analog systems, in contrast to antenna systems that employ digital signal processing to electrically form and steer beams (such as phased array antennas). In one embodiment, the antenna system is considered a “surface” antenna that is planar and relatively low profile, especially when compared to conventional satellite dish receivers.

FIG. 7Billustrates a perspective view of one row of antenna elements that includes a ground plane and a reconfigurable resonator layer. Reconfigurable resonator layer1230includes an array of tunable slots1210. The array of tunable slots1210can be configured to point the antenna in a desired direction. Each of the tunable slots can be tuned/adjusted by varying a voltage across the liquid crystal.

Control module1280is coupled to reconfigurable resonator layer1230to modulate the array of tunable slots1210by varying the voltage across the liquid crystal inFIG. 8A. Control module1280may include a Field Programmable Gate Array (“FPGA”), a microprocessor, a controller, System-on-a-Chip (SoC), or other processing logic. In one embodiment, control module1280includes logic circuitry (e.g., multiplexer) to drive the array of tunable slots1210. In one embodiment, control module1280receives data that includes specifications for a holographic diffraction pattern to be driven onto the array of tunable slots1210. The holographic diffraction patterns may be generated in response to a spatial relationship between the antenna and a satellite so that the holographic diffraction pattern steers the downlink beams (and uplink beam if the antenna system performs transmit) in the appropriate direction for communication. Although not drawn in each figure, a control module similar to control module1280may drive each array of tunable slots described in the figures of the disclosure.

Radio Frequency (“RF”) holography is also possible using analogous techniques where a desired RF beam can be generated when an RF reference beam encounters an RF holographic diffraction pattern. In the case of satellite communications, the reference beam is in the form of a feed wave, such as feed wave1205(approximately 20 GHz in some embodiments). To transform a feed wave into a radiated beam (either for transmitting or receiving purposes), an interference pattern is calculated between the desired RF beam (the object beam) and the feed wave (the reference beam). The interference pattern is driven onto the array of tunable slots1210as a diffraction pattern so that the feed wave is “steered” into the desired RF beam (having the desired shape and direction). In other words, the feed wave encountering the holographic diffraction pattern “reconstructs” the object beam, which is formed according to design requirements of the communication system. The holographic diffraction pattern contains the excitation of each element and is calculated by whologram=w*inwout, with winas the wave equation in the waveguide and woutthe wave equation on the outgoing wave.

FIG. 8Aillustrates one embodiment of a tunable resonator/slot1210. Tunable slot1210includes an iris/slot1212, a radiating patch1211, and liquid crystal1213disposed between iris1212and patch1211. In one embodiment, radiating patch1211is co-located with iris1212.

FIG. 8Billustrates a cross section view of one embodiment of a physical antenna aperture. The antenna aperture includes ground plane1245, and a metal layer1236within iris layer1233, which is included in reconfigurable resonator layer1230. In one embodiment, the antenna aperture ofFIG. 8Bincludes a plurality of tunable resonator/slots1210ofFIG. 8A. Iris/slot1212is defined by openings in metal layer1236. A feed wave, such as feed wave1205ofFIG. 8A, may have a microwave frequency compatible with satellite communication channels. The feed wave propagates between ground plane1245and resonator layer1230.

Reconfigurable resonator layer1230also includes gasket layer1232and patch layer1231. Gasket layer1232is disposed between patch layer1231and iris layer1233. Note that in one embodiment, a spacer could replace gasket layer1232. In one embodiment, iris layer1233is a printed circuit board (“PCB”) that includes a copper layer as metal layer1236. In one embodiment, iris layer1233is glass. Iris layer1233may be other types of substrates.

Openings may be etched in the copper layer to form slots1212. In one embodiment, iris layer1233is conductively coupled by a conductive bonding layer to another structure (e.g., a waveguide) inFIG. 8B. Note that in an embodiment the iris layer is not conductively coupled by a conductive bonding layer and is instead interfaced with a non-conducting bonding layer.

Patch layer1231may also be a PCB that includes metal as radiating patches1211. In one embodiment, gasket layer1232includes spacers1239that provide a mechanical standoff to define the dimension between metal layer1236and patch1211. In one embodiment, the spacers are 75 microns, but other sizes may be used (e.g., 3-200 mm). As mentioned above, in one embodiment, the antenna aperture ofFIG. 8Bincludes multiple tunable resonator/slots, such as tunable resonator/slot1210includes patch1211, liquid crystal1213, and iris1212ofFIG. 8A. The chamber for liquid crystal1213is defined by spacers1239, iris layer1233and metal layer1236. When the chamber is filled with liquid crystal, patch layer1231can be laminated onto spacers1239to seal liquid crystal within resonator layer1230.

A voltage between patch layer1231and iris layer1233can be modulated to tune the liquid crystal in the gap between the patch and the slots (e.g., tunable resonator/slot1210). Adjusting the voltage across liquid crystal1213varies the capacitance of a slot (e.g., tunable resonator/slot1210). Accordingly, the reactance of a slot (e.g., tunable resonator/slot1210) can be varied by changing the capacitance. The resonant frequency of slot1210also changes according to the equation

where f is the resonant frequency of slot1210and L and C are the inductance and capacitance of slot1210, respectively. The resonant frequency of slot1210affects the energy radiated from feed wave1205propagating through the waveguide. As an example, if feed wave1205is 20 GHz, the resonant frequency of a slot1210may be adjusted (by varying the capacitance) to 17 GHz so that the slot1210couples substantially no energy from feed wave1205. Or, the resonant frequency of a slot1210may be adjusted to 20 GHz so that the slot1210couples energy from feed wave1205and radiates that energy into free space. Although the examples given are binary (fully radiating or not radiating at all), full gray scale control of the reactance, and therefore the resonant frequency of slot1210is possible with voltage variance over a multi-valued range. Hence, the energy radiated from each slot1210can be finely controlled so that detailed holographic diffraction patterns can be formed by the array of tunable slots.

In one embodiment, tunable slots in a row are spaced from each other by λ/5. Other spacings may be used. In one embodiment, each tunable slot in a row is spaced from the closest tunable slot in an adjacent row by λ/2, and, thus, commonly oriented tunable slots in different rows are spaced by λ/4, though other spacings are possible (e.g., λ/5, λ/6.3). In another embodiment, each tunable slot in a row is spaced from the closest tunable slot in an adjacent row by λ/3.

FIGS. 9A-Dillustrate one embodiment of the different layers for creating the slotted array. The antenna array includes antenna elements that are positioned in rings, such as the example rings shown inFIG. 7A. Note that in this example the antenna array has two different types of antenna elements that are used for two different types of frequency bands.

FIG. 9Aillustrates a portion of the first iris board layer with locations corresponding to the slots. Referring toFIG. 9A, the circles are open areas/slots in the metallization in the bottom side of the iris substrate, and are for controlling the coupling of elements to the feed (the feed wave). Note that this layer is an optional layer and is not used in all designs.FIG. 9Billustrates a portion of the second iris board layer containing slots.FIG. 9Cillustrates patches over a portion of the second iris board layer.FIG. 9Dillustrates a top view of a portion of the slotted array.

FIG. 10illustrates a side view of one embodiment of a cylindrically fed antenna structure. The antenna produces an inwardly travelling wave using a double layer feed structure (i.e., two layers of a feed structure). In one embodiment, the antenna includes a circular outer shape, though this is not required. That is, non-circular inward travelling structures can be used. In one embodiment, the antenna structure inFIG. 10includes a coaxial feed, such as, for example, described in U.S. Publication No. 2015/0236412, entitled “Dynamic Polarization and Coupling Control from a Steerable Cylindrically Fed Holographic Antenna”, filed on Nov. 21, 2014.

Referring toFIG. 10, a coaxial pin1601is used to excite the field on the lower level of the antenna. In one embodiment, coaxial pin1601is a 50Ω coaxial pin that is readily available. Coaxial pin1601is coupled (e.g., bolted) to the bottom of the antenna structure, which is conducting ground plane1602.

Separate from conducting ground plane1602is interstitial conductor1603, which is an internal conductor. In one embodiment, conducting ground plane1602and interstitial conductor1603are parallel to each other. In one embodiment, the distance between ground plane1602and interstitial conductor1603is 0.1-0.15″. In another embodiment, this distance may be λ/2, where λ is the wavelength of the travelling wave at the frequency of operation.

Ground plane1602is separated from interstitial conductor1603via a spacer1604. In one embodiment, spacer1604is a foam or air-like spacer. In one embodiment, spacer1604comprises a plastic spacer.

On top of interstitial conductor1603is dielectric layer1605. In one embodiment, dielectric layer1605is plastic. The purpose of dielectric layer1605is to slow the travelling wave relative to free space velocity. In one embodiment, dielectric layer1605slows the travelling wave by 30% relative to free space. In one embodiment, the range of indices of refraction that are suitable for beam forming are 1.2-1.8, where free space has by definition an index of refraction equal to 1. Other dielectric spacer materials, such as, for example, plastic, may be used to achieve this effect. Note that materials other than plastic may be used as long as they achieve the desired wave slowing effect. Alternatively, a material with distributed structures may be used as dielectric1605, such as periodic sub-wavelength metallic structures that can be machined or lithographically defined, for example.

An RF-array1606is on top of dielectric1605. In one embodiment, the distance between interstitial conductor1603and RF-array1606is 0.1-0.15″. In another embodiment, this distance may be λeff/2, where λeffis the effective wavelength in the medium at the design frequency.

The antenna includes sides1607and1608. Sides1607and1608are angled to cause a travelling wave feed from coaxial pin1601to be propagated from the area below interstitial conductor1603(the spacer layer) to the area above interstitial conductor1603(the dielectric layer) via reflection. In one embodiment, the angle of sides1607and1608are at 45° angles. In an alternative embodiment, sides1607and1608could be replaced with a continuous radius to achieve the reflection. WhileFIG. 10shows angled sides that have angle of 45 degrees, other angles that accomplish signal transmission from lower level feed to upper level feed may be used. That is, given that the effective wavelength in the lower feed will generally be different than in the upper feed, some deviation from the ideal 45° angles could be used to aid transmission from the lower to the upper feed level. For example, in another embodiment, the 45° angles are replaced with a single step. The steps on one end of the antenna go around the dielectric layer, interstitial the conductor, and the spacer layer. The same two steps are at the other ends of these layers.

In operation, when a feed wave is fed in from coaxial pin1601, the wave travels outward concentrically oriented from coaxial pin1601in the area between ground plane1602and interstitial conductor1603. The concentrically outgoing waves are reflected by sides1607and1608and travel inwardly in the area between interstitial conductor1603and RF array1606. The reflection from the edge of the circular perimeter causes the wave to remain in phase (i.e., it is an in-phase reflection). The travelling wave is slowed by dielectric layer1605. At this point, the travelling wave starts interacting and exciting with elements in RF array1606to obtain the desired scattering.

To terminate the travelling wave, a termination1609is included in the antenna at the geometric center of the antenna. In one embodiment, termination1609comprises a pin termination (e.g., a 50Ω pin). In another embodiment, termination1609comprises an RF absorber that terminates unused energy to prevent reflections of that unused energy back through the feed structure of the antenna. These could be used at the top of RF array1606.

FIG. 11illustrates another embodiment of the antenna system with an outgoing wave. Referring toFIG. 11, two ground planes1610and1611are substantially parallel to each other with a dielectric layer1612(e.g., a plastic layer, etc.) in between ground planes. RF absorbers1619(e.g., resistors) couple the two ground planes1610and1611together. A coaxial pin1615(e.g., 50Ω) feeds the antenna. An RF array1616is on top of dielectric layer1612and ground plane1611.

In operation, a feed wave is fed through coaxial pin1615and travels concentrically outward and interacts with the elements of RF array1616.

The cylindrical feed in both the antennas ofFIGS. 10 and 11improves the service angle of the antenna. Instead of a service angle of plus or minus forty-five degrees azimuth (±45° Az) and plus or minus twenty-five degrees elevation (±25° El), in one embodiment, the antenna system has a service angle of seventy-five degrees (75°) from the bore sight in all directions. As with any beam forming antenna comprised of many individual radiators, the overall antenna gain is dependent on the gain of the constituent elements, which themselves are angle-dependent. When using common radiating elements, the overall antenna gain typically decreases as the beam is pointed further off bore sight. At 75 degrees off bore sight, significant gain degradation of about 6 dB is expected.

Embodiments of the antenna having a cylindrical feed solve one or more problems. These include dramatically simplifying the feed structure compared to antennas fed with a corporate divider network and therefore reducing total required antenna and antenna feed volume; decreasing sensitivity to manufacturing and control errors by maintaining high beam performance with coarser controls (extending all the way to simple binary control); giving a more advantageous side lobe pattern compared to rectilinear feeds because the cylindrically oriented feed waves result in spatially diverse side lobes in the far field; and allowing polarization to be dynamic, including allowing left-hand circular, right-hand circular, and linear polarizations, while not requiring a polarizer.

Array of Wave Scattering Elements

RF array1606ofFIG. 10and RF array1616ofFIG. 11include a wave scattering subsystem that includes a group of patch antennas (i.e., scatterers) that act as radiators. This group of patch antennas comprises an array of scattering metamaterial elements.

In one embodiment, each scattering element in the antenna system is part of a unit cell that consists of a lower conductor, a dielectric substrate and an upper conductor that embeds a complementary electric inductive-capacitive resonator (“complementary electric LC” or “CELC”) that is etched in or deposited onto the upper conductor.

In one embodiment, a liquid crystal (LC) is injected in the gap around the scattering element. Liquid crystal is encapsulated in each unit cell and separates the lower conductor associated with a slot from an upper conductor associated with its patch. Liquid crystal has a permittivity that is a function of the orientation of the molecules comprising the liquid crystal, and the orientation of the molecules (and thus the permittivity) can be controlled by adjusting the bias voltage across the liquid crystal. Using this property, the liquid crystal acts as an on/off switch for the transmission of energy from the guided wave to the CELC. When switched on, the CELC emits an electromagnetic wave like an electrically small dipole antenna.

Controlling the thickness of the LC increases the beam switching speed. A fifty percent (50%) reduction in the gap between the lower and the upper conductor (the thickness of the liquid crystal) results in a fourfold increase in speed. In another embodiment, the thickness of the liquid crystal results in a beam switching speed of approximately fourteen milliseconds (14 ms). In one embodiment, the LC is doped in a manner well-known in the art to improve responsiveness so that a seven millisecond (7 ms) requirement can be met.

The CELC element is responsive to a magnetic field that is applied parallel to the plane of the CELC element and perpendicular to the CELC gap complement. When a voltage is applied to the liquid crystal in the metamaterial scattering unit cell, the magnetic field component of the guided wave induces a magnetic excitation of the CELC, which, in turn, produces an electromagnetic wave in the same frequency as the guided wave.

The phase of the electromagnetic wave generated by a single CELC can be selected by the position of the CELC on the vector of the guided wave. Each cell generates a wave in phase with the guided wave parallel to the CELC. Because the CELCs are smaller than the wave length, the output wave has the same phase as the phase of the guided wave as it passes beneath the CELC.

In one embodiment, the cylindrical feed geometry of this antenna system allows the CELC elements to be positioned at forty-five degree (45°) angles to the vector of the wave in the wave feed. This position of the elements enables control of the polarization of the free space wave generated from or received by the elements. In one embodiment, the CELCs are arranged with an inter-element spacing that is less than a free-space wavelength of the operating frequency of the antenna. For example, if there are four scattering elements per wavelength, the elements in the 30 GHz transmit antenna will be approximately 2.5 mm (i.e., ¼th the 10 mm free-space wavelength of 30 GHz).

In one embodiment, the CELCs are implemented with patch antennas that include a patch co-located over a slot with liquid crystal between the two. In this respect, the metamaterial antenna acts like a slotted (scattering) wave guide. With a slotted wave guide, the phase of the output wave depends on the location of the slot in relation to the guided wave.

Cell Placement

In one embodiment, the antenna elements are placed on the cylindrical feed antenna aperture in a way that allows for a systematic matrix drive circuit. The placement of the cells includes placement of the transistors for the matrix drive.FIG. 12illustrates one embodiment of the placement of matrix drive circuitry with respect to antenna elements. Referring toFIG. 12, row controller1701is coupled to transistors1711and1712, via row select signals Row1and Row2, respectively, and column controller1702is coupled to transistors1711and1712via column select signal Column1. Transistor1711is also coupled to antenna element1721via connection to patch1731, while transistor1712is coupled to antenna element1722via connection to patch1732.

In an initial approach to realize matrix drive circuitry on the cylindrical feed antenna with unit cells placed in a non-regular grid, two steps are performed. In the first step, the cells are placed on concentric rings and each of the cells is connected to a transistor that is placed beside the cell and acts as a switch to drive each cell separately. In the second step, the matrix drive circuitry is built in order to connect every transistor with a unique address as the matrix drive approach requires. Because the matrix drive circuit is built by row and column traces (similar to LCDs) but the cells are placed on rings, there is no systematic way to assign a unique address to each transistor. This mapping problem results in very complex circuitry to cover all the transistors and leads to a significant increase in the number of physical traces to accomplish the routing. Because of the high density of cells, those traces disturb the RF performance of the antenna due to coupling effect. Also, due to the complexity of traces and high packing density, the routing of the traces cannot be accomplished by commercially available layout tools.

In one embodiment, the matrix drive circuitry is predefined before the cells and transistors are placed. This ensures a minimum number of traces that are necessary to drive all the cells, each with a unique address. This strategy reduces the complexity of the drive circuitry and simplifies the routing, which subsequently improves the RF performance of the antenna.

More specifically, in one approach, in the first step, the cells are placed on a regular rectangular grid composed of rows and columns that describe the unique address of each cell. In the second step, the cells are grouped and transformed to concentric circles while maintaining their address and connection to the rows and columns as defined in the first step. A goal of this transformation is not only to put the cells on rings but also to keep the distance between cells and the distance between rings constant over the entire aperture. In order to accomplish this goal, there are several ways to group the cells.

In one embodiment, a TFT package is used to enable placement and unique addressing in the matrix drive.FIG. 13illustrates one embodiment of a TFT package. Referring toFIG. 13, a TFT and a hold capacitor1803is shown with input and output ports. There are two input ports connected to traces1801and two output ports connected to traces1802to connect the TFTs together using the rows and columns. In one embodiment, the row and column traces cross in 90° angles to reduce, and potentially minimize, the coupling between the row and column traces. In one embodiment, the row and column traces are on different layers.

An Example of a Full Duplex Communication System

In another embodiment, the combined antenna apertures are used in a full duplex communication system.FIG. 14is a block diagram of another embodiment of a communication system having simultaneous transmit and receive paths. While only one transmit path and one receive path are shown, the communication system may include more than one transmit path and/or more than one receive path.

Referring toFIG. 14, antenna1401includes two spatially interleaved antenna arrays operable independently to transmit and receive simultaneously at different frequencies as described above. In one embodiment, antenna1401is coupled to diplexer1445. The coupling may be by one or more feeding networks. In one embodiment, in the case of a radial feed antenna, diplexer1445combines the two signals and the connection between antenna1401and diplexer1445is a single broad-band feeding network that can carry both frequencies.

Diplexer1445is coupled to a low noise block down converter (LNB)1427, which performs a noise filtering function and a down conversion and amplification function in a manner well-known in the art. In one embodiment, LNB1427is in an out-door unit (ODU). In another embodiment, LNB1427is integrated into the antenna apparatus. LNB1427is coupled to a modem1460, which is coupled to computing system1440(e.g., a computer system, modem, etc.).

Modem1460includes an analog-to-digital converter (ADC)1422, which is coupled to LNB1427, to convert the received signal output from diplexer1445into digital format. Once converted to digital format, the signal is demodulated by demodulator1423and decoded by decoder1424to obtain the encoded data on the received wave. The decoded data is then sent to controller1425, which sends it to computing system1440.

Modem1460also includes an encoder1430that encodes data to be transmitted from computing system1440. The encoded data is modulated by modulator1431and then converted to analog by digital-to-analog converter (DAC)1432. The analog signal is then filtered by a BUC (up-convert and high pass amplifier)1433and provided to one port of diplexer1445. In one embodiment, BUC1433is in an out-door unit (ODU).

Diplexer1445operating in a manner well-known in the art provides the transmit signal to antenna1401for transmission.

Controller1450controls antenna1401, including the two arrays of antenna elements on the single combined physical aperture.

The communication system would be modified to include the combiner/arbiter described above. In such a case, the combiner/arbiter after the modem but before the BUC and LNB.

Note that the full duplex communication system shown inFIG. 14has a number of applications, including but not limited to, internet communication, vehicle communication (including software updating), etc.

There is a number of example embodiments described herein.

Example 1 is an apparatus comprising: a radial waveguide having at least one plate; a radio-frequency (RF) launch coupled to the radial waveguide comprising a rectangular waveguide, a rectangular waveguide to coaxial transition coupled to the rectangular waveguide, and a coaxial to radial transition coupled to the rectangular waveguide to coaxial transition.

Example 2 is the apparatus of example 1 that may optionally include that the rectangular waveguide has a radial non-symmetric mode and the coaxial to radial transition has a radial symmetric mode.

Example 3 is the apparatus of example 1 that may optionally include that the rectangular waveguide to coaxial transition is coupled to the rectangular waveguide at a 90° angle.

Example 4 is the apparatus of example 1 that may optionally include that the coaxial to radial transition has a coaxial transmission line with a dielectric constant that is higher than air.

Example 5 is the apparatus of example 4 that may optionally include that the coax is configured to maintain a pin of the coaxial to radial transition in a centered position with respect to the coaxial to radial transition.

Example 6 is the apparatus of example 1 that may optionally include that the rectangular waveguide to coaxial transition is coupled to the coaxial to radial transition via a pin.

Example 7 is the apparatus of example 6 that may optionally include that the coaxial to radial transition has a pin and the pin is fit in a pin receptacle of the rectangular waveguide to coaxial transition.

Example 8 is the apparatus of example 6 that may optionally include that the pin is a press fit pin.

Example 9 is the apparatus of example 6 that may optionally include that the rectangular waveguide to coaxial transition comprises brass, copper, or aluminum and has a pin receptacle comprising copper, aluminum, or magnesium.

Example 10 is the apparatus of example 1 that may optionally include that the coaxial to radial transition comprises an interface shaped into concentric tiers.

Example 11 is the apparatus of example 1 that may optionally include that the radial waveguide comprises a parallel plate waveguide.

Example 12 is the apparatus of example 1 that may optionally include that the RF launch is operable to input a feed wave that propagates concentrically from the RF launch.

Example 13 is an apparatus comprising: a radial waveguide having at least one plate; a radio-frequency (RF) launch coupled to the radial waveguide comprising a rectangular waveguide, a rectangular waveguide to stripline transition coupled to the rectangular waveguide, and a stripline to radial transition coupled to the rectangular waveguide to coaxial transition.

Example 14 is the apparatus of example 13 that may optionally include that the rectangular waveguide has a radial non-symmetric mode and the stripline to radial transition has a radial symmetric mode.

Example 15 is an antenna comprising: a radial parallel plate waveguide; a radio-frequency (RF) launch coupled to the radial parallel plate waveguide comprising a rectangular waveguide having a radial non-symmetric mode, a rectangular waveguide to coaxial stepped transition coupled to the rectangular waveguide, and a coaxial to radial transition coupled to the rectangular waveguide to coax stepped transition and having a radial symmetric mode.

Example 16 is the antenna of example 15 that may optionally include that the rectangular waveguide to coaxial stepped transition is coupled to the rectangular waveguide at a 90° angle.

Example 17 is the antenna of example 15 that may optionally include that the coaxial to radial transition has a coaxial transmission line insulator with a dielectric constant that is higher than air.

Example 18 is the antenna of example 17 that may optionally include that the coaxial transmission line is configured to maintain a pin of the coaxial to radial transition in a centered position with respect to the coaxial to radial transition.

Example 19 is the antenna of example 15 that may optionally include that the rectangular waveguide to coaxial stepped transition is coupled to the coaxial to radial transition via a pin.

Example 20 is the antenna of example 19 that may optionally include that the coaxial to radial transition has the pin and the pin is fit in a pin receptacle of the rectangular waveguide to coaxial stepped transition.

Example 21 is the antenna of example 20 that may optionally include that the pin is a press fit pin.

Example 22 is the antenna of example 15 that may optionally include that the coaxial to radial transition comprises an interface shaped into concentric tiers.

Example 23 is an antenna comprising: a radial parallel plate waveguide; a radio-frequency (RF) launch coupled to the radial parallel plate waveguide comprising a rectangular waveguide having a radial non-symmetric mode, a rectangular waveguide to coaxial stepped transition coupled to the rectangular waveguide and having a pin receptacle, and a coaxial to radial transition coupled to the rectangular waveguide to coaxial stepped transition and having a radial symmetric mode, wherein the coaxial to radial transition has a pin that is coupled to the pin receptacle.

Example 24 is the antenna of example 23 that may optionally include that the coaxial to radial transition has a coaxial with a dielectric constant that is higher than air and is configured to maintain the pin of the coaxial to radial transition in a centered position with respect to the coaxial to radial transition.

Example 25 is the antenna of example 23 that may optionally include that the coaxial to radial transition comprises an interface shaped into concentric tiers.