Abstract
A dipole antenna forms a distributed network filter.
Claims
1. A dipole antenna, comprising: electrical dipole conductors formed on and/or in a substrate and 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, and one or more ceramic 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, wherein the electrical dipole conductors form a selective frequency filter.
2. The antenna of claim 1, wherein the dipole antenna is formed on and/or in a substrate.
3. The antenna of claim 1, wherein the ceramic dielectric elements have dielectric property that vary less than ±1% over temperatures between −40° C. and +125° C.
4. The antenna of claim 1, wherein the substrate is a low-loss meta-dielectric material consisting of amorphous silica.
5. The antenna of claim 1, wherein the dipole antenna forms a distributed network that filters a wireless communications band.
6. The antenna of claim 1, wherein the dipole antenna forms a distributed network that filters multiple communications bands.
7. A wireless device using the antenna of claim 1.
8. An antenna, comprising: a substrate; electrical conductors formed on and/or in the substrate; and one or more ceramic dielectric elements having relative permittivity ∈.sub.R≧10 and/or relative permeability μ.sub.R≧10 formed on and/or in the substrate between selected portions of the electrical conductors for determining a distributed reactance within the selected portions, wherein the electrical dipole conductors form a selective frequency filter.
9. The antenna of claim 8, wherein the antenna is a dipole antenna.
10. The antenna of claim 9, wherein the electrical conductors of the dipole antenna are folded to form a distributed network filter.
11. A wireless device using the antenna of claim 8.
12. 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, wherein the distributed reactance includes ceramic dielectric elements having precise dielectric permittivity and/or permeability formed on and/or in a substrate and in proximity to the conducting dipole arms.
13. The antenna of claim 12, wherein 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.
14. The antenna of claim 12, wherein the folded dipole antenna forms a distributed network that filters frequencies used in a wireless communications band.
15. The antenna of claim 12, wherein the folded dipole antenna forms a distributed network that filters frequencies used in a plurality of wireless communications bands.
16. The antenna of claim 12, wherein the folded dipole antenna forms a narrow conductance distributed network filter that isolates frequencies used in an uplink or a downlink sub-band of a wireless communications band.
17. The antenna of claim 12, wherein the 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 tunable reactance.
18. A mobile wireless device using the antenna of claim 12.
Description
BRIEF DESCRIPTION OF THE TABLES AND DRAWINGS
(1) The present invention is illustratively shown and described in reference to the accompanying drawings, in which:
(2) FIG. 1 depicts the resonance frequency (pass band) response of a dipole antenna element;
(3) FIGS. 2A,2B depict the pass bands of acoustic wave filters used to isolate uplink and downlink bands in a mobile wireless device.
(4) FIGS. 3A,3B depict a transmission line circuit and its equivalent circuit model.
(5) FIGS. 4A,B,C depict a distributed network filtering circuit and its equivalent representation using one-port, two-port and multi-port network analysis.
(6) FIGS. 5A,B,C a dipole antenna element and its equivalent circuit models.
(7) FIGS. 6A,B depicts co-linear current vector alignment in a folded dipole antenna element and its equivalent electrical circuit behavior when interpreted as a distributed network.
(8) FIG. 7 depicts the return loss of a free-space folded dipole antenna element that is tuned to produce internal distributed reactance that allows it have resonant pass bands at multiple frequency ranges useful to mobile wireless communications.
(9) FIGS. 8A,8B,8C,8D depict an equivalent circuit model of a distributed network filter useful as a narrow pass band filter, a diagram of co-linear current vector alignment that reproduces distributed reactance in a narrow pass band folded dipole element, and the conductance band and VSWR bands of a dipole antenna element folded to function as a filter for the GSM 1800 uplink frequency band.
(10) FIGS. 9A,9B depicts a folded dipole antenna element that has distributed reactance enhanced by dielectric loading
(11) FIG. 10A depicts material requirements for providing capacitive dielectric loads that are stable with varying temperature.
(12) FIG. 11 depicts material system requirements for providing inductive dielectric loads that are stable with varying temperature.
(13) FIG. 12 depicts the pass band of a tunable narrow conductance pass band antenna system.
(14) FIG. 13 depicts the use of a tunable narrow conductance pass band antenna system in a mobile wireless device.
(15) FIG. 14 depicts a basic circuit assembly useful in making a tunable narrow conductance pass band antenna system.
DETAILED DESCRIPTION OF THE INVENTION
(16) 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.
(17) 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”.
(18) 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 FIGS. 3A,3B thru 4A,4B,4C to review the basic characteristics of electromagnetic transmission lines and distributed network filters and, by extension, to illustrate the basic operational and design principles of the invention. It is not the purpose of this disclosure to derive solutions from first principles, but merely to illustrate how well-known characteristics of distributed circuits and networks can be applied to designing a folded dipole selective-frequency antenna element. A more rigorous analysis on the physics of transmission lines can be found in “Fundamentals of Microwave Transmission Lines” by Jon C. Freeman, publisher John Wiley & Sons, Inc. 1996, ISBN 0-471-13002-8. A more rigorous analysis on the electrical characteristics of distributed networks is found in “Network Analysis, 3.sup.rd Edition” by M. E. Van Valkenburg, publisher Prentice Hall, 1974, ISBN 0-13-611095-9.
(19) FIGS. 3A & 3B show the basic structure of a simple electromagnetic transmission line (TL) 10 consisting of a signal line 12 and a return line 14. An equivalent circuit 16 representation is often used to approximate and model functional characteristics per unit TL length that are useful in appraising impedance, line loss, and other time-dependent or frequency-dependent wave propagation properties of the transmission line 10. The unit length TL equivalent circuit 16 is characterized as having a series resistance 18, a series inductance 20, a shunt capacitance 22 and a shunt conductance 24.
(20) FIGS. 4A,4B & 4C generally shows how network analysis is used to segment a complex discrete component filtering network 30 into a series of isolated ports 32, 34, 36, 38. Although for the purposes of this disclosure only one-port and two-port circuit isolations are needed to adequately describe the simple planar folded-dipole examples provided below, it should be evident from this description that multi-port segments 40,42 would be needed if any additional branches that might extend conducting elements within the plane or protrude out of the plane of the folded dipole.
(21) 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.
(22) 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)
(23) Reference is now made to FIGS. 5A-6B to illustrate how the filtering characteristics of a distributed network filter can be replicated within a single dipole antenna element by folding the dipole arms in a manner that reproduces the desired distributed reactance (inductive and capacitive loads) that produces the pass band characteristics of the multi-stage filter. This is accomplished by viewing the dipole antenna 100 as a transmission line having a signal feed 102 and a signal return line 104 that are each terminated by a capacitive load 106A,106B as shown in FIG. 5A. The arrows 108A and 108B symbolize the instantaneous current vectors of the signal feed 102 and the signal return 104. The capacitive loads 106A,106B are characterized by the amount of charge that collects on the terminating surfaces of the antenna element as the radiating electromagnetic signal cycles. This simple transmission line structure is represented as a simple transmission line segment 110 (see FIG. 5B) that is terminated by the capacitive load 112. It is electrically characterized in FIG. 5C as a lumped circuit 120 with a transmission line, having series resistance 121 and inductance 122 from the wires' self-inductance and a parallel-connected (shunt) capacitance 124 and conductance 125 from capacitive coupling between the wires, that is terminated by the capacitive load 112.
(24) FIGS. 6A,B illustrates how folding the arms of a folded dipole antenna 200 modifies the simple transmission line structure of a conventional dipole shown in FIGS. 5A,5B,5C to distribute controllable levels of reactance either in series or in parallel at specific points within the circuit and, thereby, can be used to produce a distributed network filter having pre-determined pass band characteristics. FIG. 6A depicts the co-linear alignment and distribution of instantaneous current vectors 201A,201B that electromagnetically excite the folded dipole antenna 200. When viewed as a distributed network, one arm is represented as the signal line 202A, while the other arm is the circuit's return line 202B. As shown, the folds in the dipole arms create distributed reactance in coupled line segments internal to and between the dipole arms 202A,202B through parallel and anti-parallel co-linear current vector alignment over the coupled line segment. Although only three (3) reactive coupled line segments are highlighted in FIG. 6A, it should be understood that some of these coupled line segments may not be required by a given design objective, and that a plurality of coupled line segments may useful to other designs. Coupled line segments having parallel current vector alignment distribute inductive reactance over that length of the distributed network. Conversely, coupled line segments having anti-parallel current vector alignment contribute capacitive reactance over that length of the distributed network. Feed point reactance 203 has anti-parallel alignment and is generated by the coupled line segment spanning the antenna's physical feed point 204 and the first folds 205A,205B in the dipole arms 202A,202B. Feed point reactance 203 is capacitive and non-radiative because the anti-parallel coupling cancels emissions over that region. As shown by the equivalent circuit model 250 depicted in FIG. 6B, the feed point reactance 203 contributes parallel capacitive reactance 252 because it is generated by anti-parallel current vector coupling between the dipole arms 202A,202B. Series capacitance 254 is added to the distributed network by introducing folds that produce line segment coupling with anti-parallel current vector alignment within the dipole arms 202A,202B as shown in coupled line segments 206A,206B, respectively. Similarly, series inductance 256 is added to the distributed network by introducing folds that produce line segment coupling with parallel current vector alignment within the dipole arms 202A,202B as shown in coupled line segments 208A,208B. Additional parallel reactance 258 is added to the distributed network by introducing folds that produce coupling between the dipole arms 202A,202B as shown in coupled line segment 210. Line segments that are either uncoupled or in parallel coupling with additional line segments are the radiating elements of a distributed network filter folded dipole 200, and therefore contribute to the overall efficiency of the antenna when those line segments are resonantly excited. As is the case with the simple transmission line model depicted in FIGS. 5A,5B,5C, the equivalent circuit model of a distributed network filtering folded dipole antenna element 200 is terminated by a capacitive load 112 determined by the cross-sectional geometry of the conductor element used to form the arms of antenna's signal 260A and return 260B lines. It should also be noted that the individual folds in the dipole arms 202A,202B will also contribute small series inductance, but it is not shown here for the purpose of clarity.
(25) 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=lπ∈.sub.o∈.sub.r 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, ∈.sub.o is the permittivity of free-space, and ∈.sub.r is the relative permittivity of the material separating the parallel wires.
(26) 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:
(27)
where l is the coupling length, d is gap between the wires and r is the radius of the wire, all in meters, μ.sub.o is the free-space permeability, and μ.sub.r is the permeability of the material separating the parallel wires. The self-inductance of round wires in Henrys is given by:
(28)
where l is the wire length in meters, a is the wire diameter, μ.sub.r is the relative permeability of the conducting material, and μ.sub.o 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.
(29) 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 FIG. 1. A specific embodiment of the invention (see FIG. 7) uses the techniques to design and construct a single dipole antenna element that is resonant over the major communications bands 300 used in a mobile device, such as the GSM 900/850 band 302, GPS band 1575.42 MHz 304, UMTS 1700 306, and WiFi 2400 MHz 308.
(30) Reference is now made to FIGS. 8A,8B,8C,8D to illustrate specific aspects of the invention that relate to high-efficiency narrow conductance band antennas with fixed tuning. When establishing wireless signal communications it is desirable to minimize losses between the transmitter and the receiver and maximizing signal-to-noise (“SNR”) ratios. This is accomplished by enhancing the radiation efficiencies of the antenna elements and by minimizing the losses internal to the transmitter and the receiver. SNR is improved by blocking radio frequencies that do not carry useful signal information. Most filtering components contribute 1.5 dB to 3 dB of loss a piece. Therefore, it is desirable to develop methods to tune high efficiency antenna elements that are only sensitive to the electromagnetic frequencies used in an uplink or a downlink. The ability to use an antenna element as an uplink/downlink filtering system would enable considerable savings in component count, cost, occupied volume, and lost power in a mobile wireless transceiver. Table 3 shows the components that could be eliminated from a CMDA system and the direct power savings that would be achieved in the RF front-end alone by replacing the multi-component RF chain with a single antenna element. Greater power savings to the mobile device are realized since lower insertion losses in the path to the antenna would allow the power amplifier to be operated at a higher efficiency, so it consumes less power as well to produce the same RF power output.
(31) TABLE-US-00003 TABLE 3 Comparative Power Loss Analysis Conventional CDMA Narrow Band Antenna RF Input Power DC Input Wasted RF Input Power DC Input Wasted Component Power Lost Power Power Power Lost Power Power Secondary Band Filter 1 mW 1 mW 1 mW 1 mW — — Power Amplifier (PA) 1 mW −506 mW 1267 mW 761 mW 1 mW −250 mW 629 mW 379 mW PA/Duplexer matching 507 mW 23 mW 23 mW — — SAW Duplexer 484 mW 212 mW 212 mW — — Coupler 272 mW 6 mW 6 mW — — Band Select Switch 266 mW 15 mW 15 mW — — Power to Antenna 251 mW 251 mW — — 1018 mW 379 mW
(32) 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. FIG. 8A depicts a representative equivalent circuit of a distributed network filter 330 that could be used, among others, to construct a narrow band antenna element. The equivalent circuit of the distributed network filter 330 consists of a power source 331 that excites the signal 332 and return 333 lines (dipole arms), a feed point stage 334, a first intra-arm coupling stage 336 having large series inductance 338, an inter-arm stage 340 having weak parallel capacitive coupling 341, a second intra-arm coupling stage 342 having large series inductance 343, a third intra-arm coupling stage 344 having high series capacitance 346 prior to the termination 348. Additional intra-arm and inter-arm stages could be added to improve the filtering characteristics, but are not shown here for clarity.
(33) FIG. 8B is a schematic representation of a co-linear current vector alignment 349 for a folded dipole antenna that would distribute reactive loads in a manner consistent with the equivalent circuit distributed network filter 330. FIG. 8C is the narrow conductance band 350 exhibiting better than −40 dB signal isolation at the GSM 1800 uplink center frequency in the return loss of a folded dipole antenna element assembled to be consistent with vector alignment 331. FIG. 8D is the VSWR bandwidth 352 of the folded dipole antenna element assembled to consistent with vector alignment 349. A large serial inductance 338 in the folded dipole arms is needed to produce the desired VSWR and instantaneous bandwidth, which, in this instance, has VSWR values ≦2.75 between the upper 357 and lower 358 frequencies of the GSM 1800 uplink band. The large serial inductance 338 is produced in a free-space antenna by having co-linear current vectors in parallel alignment over long length segments 354A,354B of the folded dipole arms. The narrow conductance band 350 is produced by inserting a high series capacitance 346 just prior to the antenna's termination 348. This high series capacitance 346 is produced by having multiple parallel current vector alignments 356A,356A′ aligned in anti-parallel configuration with other multiple parallel current vector alignments 356B,356B′. Multiple co-linear current vector alignment configurations can be used to achieve or improve upon these results. The configuration shown in FIG. 8B is utilized here to for its simplicity and clarity.
(34) Reference is now made to FIGS. 9 thru 13 to discuss additional embodiments of the invention. Although only free-space folded dipole antennas have been discussed so far, these models may not always reflect practical conditions for certain applications. Free-space antennas are idealized in the sense that the electromagnetic properties of their surrounding environment (vacuum) are stable. Also, a free-space antenna is not electromagnetically interacting with substances positioned in its surrounding environment. Both of these scenarios can compromise antenna performance, however, the associated constraints can be mitigated or overcome by embedding the filtering antenna element in an ultra-low loss meta-material dielectric body that has electromagnetic properties that remain stable with temperature. Therefore, a preferred embodiment (see FIG. 9A) of the invention assembles the folded dipole element 400 on a substrate surface 402 or within a low loss dielectric (not shown for clarity) or meta-material dielectric. In this embodiment LCD methods are applied to selectively deposit compositionally complex electroceramics (inserted dielectric material 404) within coupled line segments 406 the distributed network filter to further refine performance of the folded dipole antenna 408. LCD methods reliably integrate high dielectric density (∈.sub.R,μ.sub.R≧10) dielectrics having properties that remain stable with varying temperature.
(35) 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.
(36) As evidenced by equation 4, the relative permittivity (∈.sub.R) 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 (μ.sub.R) 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 (∈.sub.R,μ.sub.R) 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 (∈.sub.R≧10) electroceramics. As shown in FIG. 10, the dielectric constant of the barium strontium titanate ceramic remains stable over standard operating temperatures when its average grain size is less than 50 nanometer (nm) 420, but will vary by ±15% when the average grain size is 100 nm 421 and by ±40% when the average grain size is 200 nm 422. FIG. 11 depicts the initial permeability of a magnesium-copper-zinc-ferrite dielectric as a function of temperature for five different compositions, wherein the concentration of copper (Cu) is substituted for magnesium (Mg) according to the compositional formula Mg.sub.(0.60−x)Cu.sub.(x)Zn.sub.(0.40)Fe.sub.2O.sub.4, with x=1 mol % 430, x=4 mol % 431, x=8 mol % 432, x=12 mol % 433, and x=14 mol % 434. Invariance in the permeability of magnetic materials is generally achieved in chemically complex compositions, and then only over narrow or specific compositional ranges, such as for x=1 mol % 430 and x=8 mol % 432 in the Mg.sub.(0.60−x)Cu.sub.(x)Zn.sub.(0.40)Fe.sub.2O.sub.4 system. Although permeability is a function of microstructure, grain size has a more pronounced effect on loss. However, the atomic scale compositional uniformity and precision of LCD methods is needed to maintain “critical tolerances” throughout the body of any high electromagnetic density magnetic material inserted into the folded dipole antenna 408 if it is to function as a reliable distributed network filter over standard operating temperatures.
(37) 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 FIG. 9B) in which compositionally distinct dielectric materials are inserted along the length of the coupled line segment 406. Variable-length reactive tuning is often desirable when the folded dipole antenna is embedded in a meta-material dielectric comprising an ultra-low loss host dielectric (not shown for clarity in FIGS. 9A,9B) and at least one dielectric inclusion 412. The variable reactive tuning along length of the coupled line segment 406 is used to compensate or accommodate any reactive coupling between the folded dipole antenna 408 and the dielectric inclusion 412 of an optional meta-material dielectric (not shown in FIG. 9A).
(38) 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 FIGS. 11,12&13). An RF front-end comprising a tunable narrow pass band antenna that adaptively reconfigures its filtering characteristics eliminates the need for a mobile wireless system to require multiple radio systems to navigate a fragmented communications frequency spectrum. Fixed frequency tunings require a mobile wireless device to have several radios, wherein each radio supports a dedicated communications band. In contrast, a mobile device having a wireless interface consisting of a tunable narrow conductance band antenna 500 would a allow a single radio to reconfigure itself for operation at a nearby frequency range, such as GSM 1800, GSM 1900, and UMTS 1700 IX, or GSM 900 and GSM 850 (see Table 1), thereby lowering the component count, cost, and occupied volume of the system.
(39) 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 (FIG. 6A) is an integral element of the distributed network filter that can does not contribute to the radiation profile because its current vectors mutually cancel one another through anti-parallel alignment. However, as shown in FIG. 8A, the feed network 203 does form a stage 334 consisting of the distributed network filter 330 that contributes distributed reactance to the network in the form of resistive 375A,375B, capacitive 377 and series inductance 335A,334B that can be altered to modulate the resonance characteristics of the network filter 330.
(40) FIG. 14 illustrates a preferred configuration for the tunable narrow conductance band system 600 that consists of a folded dipole antenna 602 on an upper layer of a substrate 603. A folded dipole antenna 602, configured to operate as a narrow conductance band filter, has a tunable feed network 604 that is in electrical communication with the folded dipole antenna 602 through a via system 605 with inductor 606, resistor 608, and capacitor 610 elements located on a lower circuit layer 612 that may be the backside of the substrate 604 (not shown for clarity) or the surface of an additional substrate, which could comprise and an active semiconductor material. The inductor 606, resistor 608, and capacitor 610 elements are monolithically integrated onto the lower circuit layer 612 using LCD methods described in de Rochemont '159, '042 and '222, with a switching element 614 that allows the inductance, resistance, and capacitance of the inductor 606, resistor 608, and capacitor 610 elements to be varied in ways that shift the center frequency and pass bands of the folded dipole antenna 602 to retune its filtering pass band from one communications band to another communications band at an adjacent frequency. The inductor 606, resistor 608, and capacitor 610 elements on the lower circuit layer may comprise a plurality of individual passive elements configured as a lumped circuit in series and/or in parallel, with each lumped circuit being dedicated to a particular frequency output of the folded dipole antenna 602. Alternatively, the inductor 606, resistor 608, and capacitor 610 elements may be arranged in a manner that allows the switching element to vary the inductance of the inductor element 606 by modulating the number of turns that are actively used in the coil.
(41) 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.
