Patent Grant
11063365
The present invention relates generally to dipole antennas and particularly how they can be folded to maximize its resonant response at desirable frequencies.
Antennas are used in sensors, radars and radio communication systems to transmit and/or receive electromagnetic signals wirelessly at frequencies over which the antenna element(s) experience electromagnetic resonance. Resonant dipole antennas are a class of antennas where the electromagnetic radiation emissivity/sensitivity is pronounced at the antenna's fundamental frequency and harmonics of the fundamental frequency. Resonant dipoles have low to moderate gain, which is useful in transceiver systems that require general insensitivity to the relative direction (and/or orientation) of transmit and receive antennas, such as mobile communications. They also have relatively high efficiency at resonance, which is commonly represented as a low return loss. In general, a dipole antenna spanning a length (l) will exhibit its fundamental resonance frequency ffund (also known as the first harmonic) over electromagnetic emissions having wavelength(s) given by:
2l≅λfund (1)
As shown in
As a result of this general landscape within the industry, a single service provider will likely require mobile wireless devices that contain multiple antennas/radio systems to faultlessly navigate its domestic territory or provide global portability. The better broadband antennas will electrically communicate with 33% bandwidth (Δf/fcenter) and have a peak efficiency of 70-80%, where Δf=fupper−flower. These broadband antennas would allow a single antenna element to cover two bands that are closely positioned in frequency, such as the GSM 1700 and GSM 1800 bands (see TABLE 2), but not all the frequency bands at which the mobile wireless unit must communicate and certainly not at peak efficiency. Multiple antenna elements are undesirable since each element adds to the overall cost and occupied volume.
Filtering components are electrically coupled with the antenna system in the RF front-end to isolate specific frequency bands of interest for a given transceiver (radio/radar) application. The filtering components prevent electromagnetic emissions that fall outside of the desired frequency range(s) from interfering with the signal(s) of interest and are generally required to isolate the chosen frequency band from any undesirable frequency emissions to a level −40 dB or more in most applications. As shown in TABLE 2, mobile communications system designate a portion (subband) of the communications band for uplink frequencies (from the mobile device to the tower) and another portion for downlink frequencies (from the tower to the mobile device). The RF front-end must fully isolate these distinct signaling frequencies from one another and operate simultaneously if full duplex mode communications is desired. Acoustic-wave filters are generally used in cellular communications systems to isolate uplink frequencies 3 from downlink frequencies 4 and provide the requisite better than −40 dB signal isolation as shown in
Mobile wireless devices have radios with fixed frequency tuning, so a single radio system will only communicate over a specific frequency band. As a result of the fixed uplink/downlink tuning most mobile devices will have multiple radio systems since a given wireless carrier may not have license to operate at the premium (required) frequency bands shown in TABLE 1 throughout an entire nation. A given wireless service provider will be less likely to have access to the premium or required frequencies in foreign countries. The need for additional radios in their mobile systems is undesirable as it adds considerable cost to the service.
The following is a representative sampling of the prior art.
The term “active component” is herein understood to refer to its conventional definition as an element of an electrical circuit that that does require electrical power to operate and is capable of producing power gain.
The term “amorphous material” is herein understood to mean a material that does not comprise a periodic lattice of atomic elements, or lacks mid-range (over distances of 10's of nanometers) to long-range crystalline order (over distances of 100's of nanometers).
The terms “chemical complexity”, “compositional complexity”, “chemically complex”, or “compositionally complex” are herein understood to refer to a material, such as a metal or superalloy, compound semiconductor, or ceramic that consists of three (3) or more elements from the periodic table.
The terms “discrete assembly” or “discretely assembled” is herein understood to mean the serial construction of an embodiment through the assembly of a plurality of pre-fabricated components that individually comprise a discrete element of the final assembly.
The term “emf” is herein understood to mean its conventional definition as being an electromotive force.
The term “integrated circuit” is herein understood to mean a semiconductor chip into which at least one transistor element has been embedded.
The term “LCD” is herein understood to mean a method that uses liquid precursor solutions to fabricate materials of arbitrary compositional or chemical complexity as an amorphous laminate or free-standing body or as a crystalline laminate or free-standing body that has atomic-scale chemical uniformity and a microstructure that is controllable down to nanoscale dimensions.
The term “liquid precursor solution” is herein understood to mean a solution of hydrocarbon molecules that also contains soluble metalorganic compounds that may or may not be organic acid salts of the hydrocarbon molecules into which they are dissolved.
The term “meta-material” is herein understood to define a composite dielectric material that consists of a low-loss host material having a dielectric permittivity in the range of 1.5≤εR≤5 with at least one dielectric inclusion embedded within that has a dielectric permittivity of εR≥10 or a dielectric permeability μr≠1 that produces an “effective dielectric constant” that is different from either the dielectric host or the dielectric inclusion.
The term “microstructure” is herein understood to define the elemental composition and physical size of crystalline grains forming a material substance.
The term “MISFET” is herein understood to mean its conventional definition by referencing a metal-insulator-semiconductor field effect transistor.
The term “mismatched materials” is herein understood to define two materials that have dissimilar crystalline lattice structure, or lattice constants that differ by 5% or more, and/or thermal coefficients of expansion that differ by 10% or more.
The term “MOSFET” is herein understood to mean its conventional definition by referencing a metal-oxide-silicon field effect transistor.
The term “nanoscale” is herein understood to define physical dimensions measured in lengths ranging from 1 nanometer (nm) to 100's of nanometers (nm).
The term “passive component” is herein understood to refer to its conventional definition as an element of an electrical circuit that that does not require electrical power to operate and is not capable of producing power gain.
The term “standard operating temperatures” is herein understood to mean the range of temperatures between −40° C. and +125° C.
The terms “tight tolerance” or “critical tolerance” are herein understood to mean a performance value, such as a capacitance, inductance, or resistance that varies less than ±1% over standard operating temperatures.
In view of the above discussion, it would be beneficial to have methods to have antenna systems that reduce the cost, component count, power consumption and occupied volume in fixed wireless and mobile wireless systems by either using a single antenna element to selectively filter multiple bands. For the same purposes, it would also be beneficial to have a high radiation efficiency narrow band antenna that eliminates the need for additional filtering components in the RF front-end. It would also be beneficial to have a high radiation efficiency narrow band that can be actively tuned to vary its center frequency to mitigate the need for multiple radio systems in a globally portable wireless device.
It is an object of the present invention to provide a single antenna element that is strongly resonant over multiple selective frequency bands or all communications bands of interest for a particular device to eliminate the need for multiple antenna systems, thereby minimizing cost, component count, and occupied volume without compromising the mobile system's signal integrity.
It is a further object of the present invention to provide a single antenna element that has a sufficiently narrow conductance band (25 MHz to 60 MHz) to isolate uplink frequencies from the downlink frequencies in the same communications band, thereby eliminating the need to add filtering components, like acoustic-wave filters, to the RF front-end to minimize cost, component count and occupied volume.
It is yet another object of the present invention is to provide a narrow band (25 MHz to 60 MHz) antenna system that can actively retune the center frequency of a narrow conductive pass band to accommodate a plurality of communications frequency band tunings with a single antenna element.
The present invention generally relates to a single dipole antenna element that is tuned to have a frequency-selective resonant response, and in particular to folded dipole antennas in which high dielectric density ceramic material (εR≥10 and/or μR≥10) has been selectively deposited into electromagnetically coupled regions that function as “reactive tuning elements” to produce the desired spectral response and/or to maximize the dipole's radiation efficiency.
The dipole arms are folded in a pre-determined manner to create a distributed network filter consisting of reactive tuning elements inserted along the length of the dipole arms. Inductive and/or capacitive tuning elements are configured in series or in parallel to produce one or more desirable conductive pass bands with suitable voltage standing wave ratios to achieve high instantaneous bandwidth. Reactive tuning elements are configured in series connection by introducing coupling within a dipole arm, and are configured in parallel connection by introducing coupling between the dipole arms.
High dielectric density ceramic material is inserted into electromagnetically coupled regions to strengthen the coupling of the reactive loading of a reactive tuning element. The coupling length of a reactive tuning element may be divided into a plurality of segments, in which each segment may contain a compositionally distinct high dielectric density ceramic material, or the absence of a high dielectric density ceramic, to fine tune the reactive loading of the segmented reactive tuning element.
Temperature stability of the dielectric properties of the ceramic material inserted into the electromagnetically coupled regions is essential to providing stable RF performance over any range of temperatures the dipole antenna would be expected to perform.
The distributed network filter so formed may tune the folded dipole antenna to produce multiple frequency-selective electromagnetic resonances that match a plurality of useful frequency bands.
Alternatively, the distributed network filter so formed may also tune the folded dipole antenna to produce a conductance pass band that is sufficiently narrow and sharp to isolate a communications uplink or a communications downlink sub-band when configured with a quarter-wave transformer in electrical communication with the dipole antenna feed point.
The resonance center frequency and band edges of a narrow and sharp conductance pass band antenna can be shifted by adaptively tuning the reactance of quarter-wave transformer by altering the capacitance and/or inductance in the feed network electrically communicating with dipole antenna's feed point.
One embodiment of the present invention provides a dipole antenna, comprising electrical dipole conductors folded to form distributed inductive and/or capacitive reactive loads between selected portions of one or more coupled line segments of the individual dipole conductors or between one dipole conductor to another, wherein the electrical dipole conductors form a selective frequency filter.
The dipole antenna may be formed on and/or in a substrate. The antenna may further comprise one or more dielectric elements having precise dielectric permittivity and/or permeability formed on and/or in the substrate and located in proximity to the coupled line segments for determining an enhanced distributed reactance in the inductive and/or capacitive reactive loads. The ceramic dielectric elements may have dielectric property that vary less than ±1% over temperatures between −40° C. and +125° C. The substrate may be a low-loss meta-dielectric material consisting of amorphous silica. The dipole antenna may form a distributed network that filters a wireless communications band. The dipole antenna may form a distributed network that filters multiple communications bands. A wireless device may the antenna described above.
Another embodiment of the present invention provides an antenna, comprising a substrate, electrical conductors formed on and/or in the substrate, and one or more ceramic dielectric elements having relative permittivity εR≥10 and/or relative permeability μR≥10 formed on and/or in the substrate between selected portions of the electrical conductors for determining a distributed reactance within the selected portions.
The antenna may be a dipole antenna. The electrical conductors of the dipole antenna may be folded to form a distributed network filter. A wireless device maybe constructed using this antenna.
Yet another embodiment of the present invention provides a folded dipole antenna, comprising conducting dipole arms, a distributed network filter having distributed reactance within and between the conducting dipole arms, and a tunable reactance connected to an input of the distributed network filter for adjusting a resonant frequency of the antenna.
The distributed reactance within and between the conducting dipole arms that forms through the electromagnetic coupling of adjacent current vectors traveling within co-linear segments of the conducting dipole arms: has distributed series capacitance along co-linear conductor segments where the adjacent current vectors are traveling in the same dipole arm and have anti-parallel alignment; has distributed series inductance along co-linear conductor segments where the adjacent current vectors are traveling in the same dipole arm and have parallel alignment; has distributed parallel capacitance along co-linear conductor where the adjacent current vectors are traveling in different dipole arms and have anti-parallel alignment; and; the distributed reactance so configured forms a distributed network filter through the purposeful arrangement of capacitive and inductive loads in series and/or in parallel.
The folded dipole antenna may form a distributed network that filters frequencies used in a wireless communications band. The folded dipole antenna may form a distributed network that filters frequencies used in a plurality of wireless communications bands. The folded dipole antenna may form a narrow conductance distributed network filter that isolates frequencies used in an uplink or a downlink sub-band of a wireless communications band. The narrow conductance distributed network filter can switch between an uplink sub-band or a downlink sub-band in one wireless communications band to the uplink sub-band or the downlink sub-band in an adjacent wireless communications band by switching the distributed reactive loading in the feed network of the folded dipole antenna. A mobile wireless device may be constructed using this antenna.
The present invention is illustratively shown and described in reference to the accompanying drawings, in which:
The present invention is illustratively described above in reference to the disclosed embodiments. Various modifications and changes may be made to the disclosed embodiments by persons skilled in the art.
This application incorporates by reference all matter contained in de Rochemont '698, U.S. Pat. No. 7,405,698 entitled “CERAMIC ANTENNA MODULE AND METHODS OF MANUFACTURE THEREOF”, its divisional application de Rochemont '002, filed U.S. patent application Ser. No. 12/177,002 entitled “CERAMIC ANTENNA MODULE AND METHODS OF MANUFACTURE THEREOF”, de Rochemont '159 filed U.S. patent application Ser. No. 11/479,159, filed Jun. 30, 2006, entitled “ELECTRICAL COMPONENTS AND METHOD OF MANUFACTURE”, and de Rochemont '042, U.S. patent application Ser. No. 11/620,042, filed Jan. 6, 2007 entitled “POWER MANAGEMENT MODULE AND METHOD OF MANUFACTURE”, de Rochemont and Kovacs '112, U.S. Ser. No. 12/843,112 filed Jul. 26, 2010, entitled “LIQUID CHEMICAL DEPOSITION PROCESS APPARATUS AND EMBODIMENTS”, and de Rochemont '222, U.S. Ser. No. 13/152,222 filed Jun. 2, 2011 entitled “MONOLITHIC DC/DC POWER MANAGEMENT MODULE WITH SURFACE FET”.
A principal objective of the invention is to develop means to design and construct a high-efficiency frequency selective antenna system that uses a single dipole antenna element to isolate one or more RF frequency bands by folding the dipole arms in a manner that causes it to function as a distributed network filter. Reference is now made to
Network analysis mathematically develops network functions from a series of interconnected ports from port transfer functions that relate the currents 44A,44B,44C,44D entering/leaving a given port with the voltages 46A,46B,46C,46D at that specific port through the impedance functions, Z(s)=V(s)/I(s), internal to that port. These well known techniques are used to construct multiple stage filters that have well-defined pass bands and varying bandwidths, as desired, at multiple center frequencies. Pass bands can be worked out mathematically by hand and bread-boarded. Alternatively, optimization software allows a user to define pass band characteristics at one or more center frequencies and the computer simulator will determine the optimal filtering component values to achieve a desired output for a given multi-stage filter architecture.
The following lumped circuit phasor expressions can be used to approximate impedance functions along a transmission line or among the components connected within a port when the physical size of the circuit/antenna element is much smaller than the electromagnetic wavelength of signals passing through the system and time delays between different portions of the circuits can be ignored.
V=jωLI (2a)
I=jωCV (2b)
V=IR (2c)
In many instances that may not be the case, so the following distributed circuit equations are needed to have a more precise representation of functional performance within a port if the impedance transfer function is mathematically derived.
−(dV/dx)=(R+jωL)I (3a)
−(dI/dX)=(G+jωC)V (3b)
Reference is now made to
The coupling length 210 and coupling gap 212 determine the frequency-dependent value of the reactance by a coupled line segment introduced into the distributed network folded dipole antenna 200. A simplified equation for the capacitance (in Farads) generated by line segment coupling (anti-parallel current vector alignment) between two parallel round wire segments in the absence of a ground plane can be given by:
C=lπεoεr ln(d/r) (4)
where l is the coupling length, d is gap between the wires and r is the radius of the wire, all in meters, εo is the permittivity of free-space, and εr is the relative permittivity of the material separating the parallel wires.
An equation for the inductance in Henrys generated by inductive coupling between two parallel wire segments in the absence of a ground plane can be given by:
where l is the coupling length, d is gap between the wires and r is the radius of the wire, all in meters, μo is the free-space permeability, and μr is the permeability of the material separating the parallel wires. The self-inductance of round wires in Henrys is given by:
where l is the wire length in meters, a is the wire diameter, μr is the relative permeability of the conducting material, and μ0 is the free-space permeability. Other equations would apply when the dipole arms do not comprise cylindrical wire. It should also be noted that any conducting wire shape can be used to form the folded dipole, however, the use of cylindrical wire in the folded dipole using the construction methods taught by de Rochemont '698 and '002 are preferred because of the stronger inductive coupling they provide.
It should be straightforward to anyone skilled in the art of network filter and antenna design that the ability to control the distributed reactance using the techniques described above permits the development of a more sophisticated multi-stage folded dipole antenna element that has multiple resonances with frequency-selective pass bands that are not limited to the characteristic resonant excitations of a fundamental frequency and its higher order harmonics as shown in
Reference is now made to
The maintenance of high instantaneous bandwidth is a necessary property for high efficiency narrow conductance band antennas. To achieve this it is necessary to develop a network filter that provides a VSWR bandwidth that is substantially larger than the antenna conductance bandwidth and has a minimum value ≤2.75 over the desired frequency range, but rises sharply outside the band edges. The wider VSWR bandwidth allows a quarter-wave transformer network to square off and sharpen the edges the antenna's conductance band as taught by de Rochemont '042, incorporated herein by way of reference.
Reference is now made to
The application of LCD methods to antenna element assembly on a substrate, a substrate that contains an artificial ground plane, or within a meta-material dielectric body are discussed in de Rochemont '698, '002, and '159, which are incorporated herein by reference. The LCD process and the types of advanced materials it enables, including the manufacture of compositionally complex materials having a high dielectric density with properties that remain stable with temperature, are discussed in de Rochemont and Kovacs '112, which is incorporated herein by reference. The application of LCD methods to build fully integrated monolithic integrated circuitry and power management devices is discussed in de Rochemont '042 and '222, which are incorporated herein by reference.
As evidenced by equation 4, the relative permittivity (εR) of an inserted dielectric material 404 positioned in the gap of electromagnetically coupled line segments 406 within the folded dipole antenna formed between conductors carrying instantaneous currents having vectors anti-parallel alignment will proportionally increase the distributed capacitance of the coupled line segment. Similarly, as evidenced by equation 5, the relative permeability (μR) of a material situated in the gap of coupled line segments within the folded dipole antenna formed between conductors carrying instantaneous currents having vectors in parallel alignment will proportionally increase the distributed inductance of the coupled line segment. The linear relationship between reactive loading and the relative dielectric strength (εR,μR) of material inserted within gaps 406 between coupled line segments makes insertion of high density material into the folded dipole a reliable means to precisely tune the distributed reactance of a coupled line segment to achieve a specific filtering objective or to enhance radiation efficiency. This is only the case if the operational temperature of the antenna remains constant or the dielectric properties of the inserted dielectric material 404 are stable with varying temperature because any changes to the strength of the inserted dielectric material 404 will compromise performance characteristics by proportionally changing the reactance distributed within the coupled line segment. LCD alleviates these concerns through its ability to selectively deposit compositionally complex electroceramics that have atomic scale chemical uniformity and nanoscale microstructure controls. This enables the construction of distributed networks having reactive loads that meet critical performance tolerances by maintaining dielectric values within ≤±1% of design specifications over standard operating temperatures. The combination of atomic scale chemical uniformity and nanoscale microstructure are strictly required when inserting a high permittivity (εR10) electroceramics. As shown in
Higher reactive loading may be desired for several reasons, including a need for achieving higher levels of distributed capacitive/inductance over a shorter line coupling length, a desire to extend the electrical length (shorten the physical length) of the filtering antenna element, or a desire to improve antenna radiation efficiency. High radiation efficiencies are achieved in folded dipole antennas that have reactive tunings that cause the distributed magnetic energy at resonance to occupy a surface area (or volume in 3-dimensional folded dipole configurations) that is equal to the surface area (or volume) of the distributed electrical energy at resonance. High radiation efficiencies are also achieved with reactive tunings that concentrate the resonant magnetic energy at the feed point and distribute the resonant electrical energy over the surface (or volume) of the folded dipole antenna. To achieve these conditions it is often necessary to vary the reactive tuning along the length of a coupled line segment 406. It is therefore a preferred embodiment of the invention to subdivide a coupled line segment 406 into a plurality of dielectric subdivisions 410A, 410B, 410C, 410D, 410E (shown in close up view in
Final embodiments of the invention relate to a tunable narrow conductance band antenna 500 which allows the center frequency 501 and pass band of such a high-Q filtering antenna to be shifted 502 up or down in frequency over a limited frequency range and its use in a mobile wireless device 550. (See
While it would be possible to use a substance have variable dielectric properties as an inserted dielectric material 404 within the coupled line segments 406 of a folded dipole antenna 408, materials that have dielectric constants that can be varied in response to an applied stimulus generally have dielectric properties that are very sensitive to changes in temperature, which would complicate the antenna system by requiring temperature sensors and control loops to maintain stable filtering functions under normal operating conditions. Therefore, it is preferable to use LCD methods to integrate advanced dielectric materials that satisfy critical performance tolerances and use alternative means to alter the resonance properties of the folded dipole antenna. As noted above, the feed network 203 (
Regarding substrate materials amorphous silica is among the most transparent electromagnetic materials available in nature. It has the lowest real dielectric permittivity (ϵ=3.9) among the environmentally safe ceramic oxides, and it has a room temperature dielectric loss tangent tan .δ.=2.times.10.sup.-5 that is roughly two orders of magnitude better than the ceramics used in tape cast assemblies. Titania is also a loss (tan .δ.=9.times.10.sup.-4) high-.kappa. (.ϵ..sub.R=90) dielectric. However, both materials have such highly refractory thermal properties that their use is prohibited in their pure form in conventional multilayer assemblies, as the temperatures needed consolidate disparate powders incorporated into green tapes would destroy any high conductivity metallic elements designed into the structure. Conventional silica-based or titania-based tapes must include chemical additives that lower the sintering temperature needed to consolidate a tape stack to temperatures below the melting point of the metals incorporated into the assembly. These additives increase both the dielectric loss tangent (tan .δ.) and the real permittivity of a dielectric body. The ability to fabricate amorphous silica at temperatures .ltoreq.450.degree. C. provides a means to incorporate this ultra-low loss material as a host material in a meta-material dielectric body, rather than as a supplemental layer, to increase the radiation efficiency of a miniaturized antenna embedded within the meta-material dielectric.
The methods and embodiments disclosed herein can be used to fabricate an antenna element that functions as a filtering network that is selectively tuned to have high-efficiency at specific resonant frequencies and to have pre-determined bandwidth at those resonant frequencies.
This application is a continuation of U.S. patent application Ser. No. 14/618,029 filed Feb. 10, 2015, which is a continuation in part of U.S. patent application Ser. No. 13/163,654 filed Jun. 17, 2011, which claims priority of U.S. Provisional Patent Application Ser. No. 61/355,755, filed Jun. 17, 2010 and is a continuation in part of U.S. patent application Ser. No. 12/818,025 filed Jun. 17, 2010, which claims priority to U.S. Provisional Patent Application 61/187,687 filed Jun. 17, 2009, all of which applications are hereby incorporated herein by reference in their entirety.
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| 20180248266 A1 | Aug 2018 | US |
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