Abstract: An integrated circuit (IC) antenna structure includes a micro-electromechanical (MEM) area, a feed point, and a transmission line. The micro-electromechanical (MEM) area includes a three-dimensional shape, wherein the three dimensional-shape provides an antenna structure. The feed point is coupled to provide an outbound radio frequency (RF) signal to the antenna structure for transmission and to receive an inbound RF signal from the antenna structure. The transmission line electrically coupled to the feed point.

Abstract: An antenna includes a feedpoint support plate (10) which is provided with terminal connectors (27, 28) to attach feed wires (25, 26) to dipole lines (31, 32). A balun (33) of one size may be connected to the plate (10) by fastening assemblies (43, 44, 45) received at apertures (29, 30) in the plate (10) and at apertures (41) of the balun (33). Baluns of other sizes may also be connected to the plate (10) by fastening assemblies (64, 65, 66) received at apertures (62, 63) in the plate (10) and at holes (60, 61) provided with the coil (57). The plate (10) can also carry a strain relief bracket (70) which includes grip members (76) which engage the feed line (24) at two spaced locations with a loop (79) formed therebetween to isolate a coupling (34) from any strain.

Abstract: A feeding apparatus for a monopole antenna having a radiating unit and a grounding unit is for transmitting a multimedia signal to a multimedia player device coupled to the radiating unit. The feeding apparatus includes a first feeding unit coupled to an inner conductor of a coaxial cable for feeding the multimedia signal transmitted by the coaxial cable to the radiating unit, and a second feeding unit coupled to a conducting mesh of the coaxial cable for connecting to the grounding unit.

Abstract: An antenna (8), mounted to a roof (3) of a building (1), receives digital broadcast transmissions and feeds a signal through a cable (9) to a desk stand (2). The desk stand has an amplifier and a loop antenna. A mobile telephone handset (6) capable of receiving digital broadcast transmissions also includes a loop antenna. Using inductive coupling, the signal is transmitted from the desk stand to the mobile telephone handset.

Abstract: An antenna structure includes a substrate, a signal transmission unit and at least one fixing unit. The substrate is made of a dielectric material and has at least a through hole. The signal transmission unit has a transmission path and goes through the through hole. The fixing unit is made of a flexible or deformable material, and is in contact with the signal transmission unit and the inner surface of the through hole to fix the signal transmission unit on the substrate.

Abstract: Improved feed line networks for antenna arrays operating at millimeter wave frequencies are provided for constructing planar antenna arrays printed on the surface of a dielectric substrate. A planar antenna array includes an array of planar radiator elements interconnected through a feed line network of planar coplanar transmission lines that enable high-efficiency operation, at millimeter wave operating frequencies. For example, a feed network may be formed with a network of coplanar strip line transmission lines including one or more coplanar strip line (CPS) and one or more coplanar waveguide (CPW) transmission line, which are interconnected using balun structures, to enable high efficiency operation at millimeter wave frequencies.

Abstract: A low-visibility, fixed-tune, wideband, and field-diverse antenna provides cross-polarized fields enhancing signal communications but having helical antenna characteristics without severe circular polarization radiation thereby promoting a modern, futuristic, and disguised look for reliable communications. A generally flat, but helical, antenna is achieved in conjunction with a core substrate about which the antenna is wrapped, wound, or fixed. The core substrate, pitch or angle of the helix, length of the transmitting antenna, and copper traces thickness are chosen for a specific resonant frequency range. The length and width of the helix are chosen in order to dimension the helical antenna between its linear and circular polarization modes to thereby deliver field-diverse and cross-polarized transmission modes. In order to optimize the manufacturing process, holes may be created within the substrate.

Abstract: A multi-input and multi-output antenna system is disclosed. The antenna system includes a predetermined quantity of dual-feed and dual-band antennas that are arranged into a polygon on a plane. The dual-feed and dual-band antenna includes a substrate, a grounding unit disposed on the substrate and having two opposite sides, a first radiating unit disposed on the substrate near one side of the grounding unit, and a second radiating unit disposed on the substrate near the other side. The second radiating unit has a shorting element that is electrically connected to the grounding unit. The polygon is bounded by lengthwise projection lines of the dual-feed and dual-band antennas.

Abstract: A signal carrying apparatus (101) for transmitting a signal by variation of electromagnetic field comprises a meshed first conductor portion (111) which serves as a conductor in the frequency band of the electromagnetic field, and a second conductor portion (121) of which external shape is sheet-like and which serves as a conductor in the frequency band of the electromagnetic field and arranged substantially in parallel with the first conductor portion (111). In the interval region (131) between the external shape of the first conductor portion (111) and the external portion of the second conductor portion (121), and in the planar leak region (141) located oppositely to the interval region (131) across the external shape of the first conductor portion (111), the electromagnetic field propagating in that frequency band has a strength attenuating exponentially with the distance from the external shape of the first conductor portion (111) in the leak region (141).

Abstract: An antenna feeding network including at least one antenna feeding line, each antenna feeding line including a coaxial line having a central inner conductor and a surrounding outer conductor. The outer conductor (4) is made of an elongated tubular compartment (5) having an elongated opening (6) along one side of the compartment (5), and that the inner conductor (3) is suspended within the tubular compartment (5) by dielectric support elements (7).

Abstract: An antenna grounding system comprises an electronic device having at first member movably coupled to a second member, at least one cable extending between the first and second members and coupled to an antenna, and a clip having at least two fingers configured to receive the at least one cable therebetween and provide grounding for the at least one cable.

Abstract: An antenna system for remote control applications including a communications module, a printed circuit board including an antenna assembly disposed thereon, and a radio frequency cable having a first connection end and a second connection end. The first connection end may be coupled to the communications module and the second connection end may be coupled to the printed circuit board. The second connection end includes a center conductor for communicating signals and a coaxial shield encircling the center conductor. A portion of the center conductor may extend from the coaxial shield and have a substantially 90 degree bend above a connection point of the printed circuit board and center conductor.

Abstract: An electromagnetic field sensor or generator employing a radio frequency microstrip transmission channel formed by a low-loss dielectric substrate sandwiched between a non-resonant microstrip conductor and a conductive ground plane. A discontinuity in said microstrip conductor that substantially alters its cross-sectional dimensions causes electrical signals in the microstrip conductor to be inductively coupled to near field electromagnetic radiation in the vicinity of the discontinuity. The discontinuity may be defined by one or more holes, slots, slits or stubs in the microstrip. The sensor/generator may be used in numerous applications, including NMR spectrometry, as a near field scanning device to inspect operating integrated circuits, or to read or write data on magnetic materials.

Abstract: A method for determining an array space of an array antenna by using a genetic algorithm and an array antenna having a soft structure with irregular array spacing are disclosed. The array antenna having a sofa structure with irregular array spacing, includes: a plurality of radiation elements having an inclined angle based on a horizontal plane and arranged with irregular array spacing for radiating and receiving an radio wave; a plurality of phase shifters for amplifying radiation signals radiated from the plurality of radiation elements and receiving signals received from the plurality of radiation elements, and controlling phases of the radiation signals and the receiving signals; and a radio wave signal coupler for dividing a transmitting signal to the radiation signals, transferring the divided radiation signals to the plurality of phase shifters and coupling the receiving signals from the plurality of phase shifters.

Abstract: Radiant electromagnetic energy beam steering method achieved following antenna conversion from electrical current and voltage characterized signals to radiant wave characterized signals by way of the influence of gaseous plasma of controlled plasma density and electron density on the electromagnetic energy. Reflection and refraction mechanisms are used to impose plasma influence on the steered electromagnetic energy. The employed plasma properties are determined by an electrically energized array of electrodes disposed along the plasma extent. Adaptation of the method to widely differing wavelength parts of the electromagnetic energy spectrum is included. A plurality of prior art patents is identified in supplement of present disclosure of the invention.

Abstract: An attachment rack apparatus with antenna is provided, including a first connection unit, a second connection unit and an antenna unit. The first connection unit includes a first attachment plate and a second attachment plate. One end of the first and second attachment plates are connected together. The two attachment plates are arcs facing each other to form a non-closed space. The bottom of the second connection unit is attached to the joint of the first and the second attachment plates. The top of the second connection unit is attached to the antenna unit. The second connection unit provides the antenna unit with space and mechanism for adjustment in angles, positions and orientations. The present invention is applicable to a holder with suction disc for holding electronic devices in a vehicle.

Abstract: A portable audio wireless communication device cooperating with a portable electrical apparatus with a display component has a plug for matting with the portable electrical apparatus, a speaker and a cable connected the plug and the speaker. The plug has a signal contact connected one end of a signal wire of the cable, a ground contact connected one end of a matching antenna wire of the cable, a first antenna contact connected one end of a first antenna wire and one end of the matching antenna, and a second antenna contact connected one end of the second antenna of the cable. When the portable audio wireless communication device operates at wireless communication, cooperation of the first antenna wire and the matching antenna wire resonates at UHF broadcast band, and the second antenna wire resonates at FM broadcast band and VHF broadcast band.

Abstract: An antenna comprises a lower section, an upper section, and a junction connecting them to each other. The junction has a key and a keyway to permit joining them only one way. In one embodiment, a whip assembly is joined to a mount assembly by a keyed junction.

Abstract: A system and method are provided for regulating the electrical length of an antenna. The method comprises: communicating transmission line signals at a predetermined frequency between a transceiver and an antenna; sensing transmission line signals; and, modifying the antenna electrical length in response to sensing the transmission line signals. Sensing transmission line signals typically means sensing transmission line signal power levels. In some aspects, the antenna impedance is modified. Alternately, it can be stated that the transmission line signal strength is optimized between the transceiver and the antenna. More specifically, communicating transmission line signals at a predetermined frequency between a transceiver and an antenna includes accepting the transmission line signal from the transceiver at an antenna port. Then, sensing transmission line signals includes measuring the transmission line signal reflected from the antenna port.

Abstract: A balun used in high-power applications capable of accommodating a transmission line includes a core with a top surface and a bottom surface formed from soft iron material. At least two holes are provided through the core between the top surface and the bottom surface to accommodate at least one winding of the transmission line. For a given amount of core material and transmission line wound through the core, the balun serves to maximize the amount impedance on the outside surface of the transmission line to decrease the amount of electrical flux generated where the transmission line is attached to the transmission lines of an antenna.

Abstract: An interchangeable Gametenna used in conjunction with a wireless telephone to play a game. The Gametenna includes an antenna having at least one radiating element for receiving and transmitting wireless signals, and a memory device which is physically coupled to the radiating element by at least one non-conductive mount which electrically isolates the memory device from the radiating element. The wireless telephone includes a transceiver, a first external interface electrically coupled to the transceiver, a processor and a second external interface electrically coupled to the processor. The Gametenna expands the capabilities of the wireless telephone when connected to the first and second external interfaces. The transceiver receives and transmits wireless signals via the first external interface and the radiating element of the antenna. The processor accesses data stored in the memory device via the second external interface. The data may include instructions for playing a game.

Abstract: A unitary feed structure for sliding installation in a passage in the insulative core of a dielectrically-loaded antenna comprises the unitary combination of a tubular outer shield conductor and elongate inner conductor which extends through the shield conductor and is insulated from the latter. The shield conductor and inner conductor have oppositely directed radially extending connection members at an end of the feed structure, these connection members being integrally formed as part of the respective conductors so that the feed structure can be inserted as a unit into the passage in the antenna core so that the connection members engage respective connection portions formed on an end face of the core adjacent on end of the passage. Soldering of the connection members to the connection portions can be performed as a single operation so as to connect the feed structure to conductive antenna elements plated on the outer surface of the core.

Abstract: A biconical antenna; an entry conic having an entry base opposite an entry vertex and a termination conic having a termination base opposite a termination vertex. The entry and termination conics share substantially the same axis and the entry vertex is adjacent the termination vertex. The transmission line is received by the entry conic and terminated in the termination conic. Together, the entry conic and the termination conic phase correct energy emanating from the transmission line. Another embodiment of the antenna comprises an entry conic having at least two sub-conics and a termination conic having at least two sub-conics. Each of the sub-conics having an integer multiple of a half-angle. The biconical antenna may also include a multi-conductor transmission line, wherein the biconical antennas are arranged in a co-linear relationship. Each of the multi-conductors is coupled to at least one of the plurality of biconical antennas.

Abstract: A compact fixturing means is disclosed that delivers two or more phase tracked channels of high power (e.g., 1000 Watts) to an antenna that can produce a multiplicity of polarization depending on the phase relationship of the delivered signals. Coaxial cables are used as a service loop to provide two or more channels of phase tracking and high power signals to the multi-polarized antenna. A flat spiral spring is configured within the fixture to the guide two (or more) coaxial cables along a spiral loop to allow approximately equal tension on the cables as the fixture is rotated. The flat spiral spring is operatively coupled to a rotation plate and progresses form an inner radius proximate the fixture input to an outer radius proximate the fixture output.

Abstract: An antenna device comprises a coaxial cable that has a central conductor and an outer conductor and is folded into an L-shape at an end portion. An L-shaped first-conductor-portion is electrically connected to the central conductor at the end portion of the coaxial cable. An L-shaped second-conductor-portion is electrically connected to the outer conductor at the end portion of the coaxial cable and is disposed along an outer circumferential face of the coaxial cable. The first and second conductor portions as a whole are formed into an approximate U-shape.

Abstract: To attain the advantages of and in accordance with the purpose of the present invention, a connector for an antenna is provided. The connector comprises a nut, insulator, contact pin, sleeve, and a captive housing. The connector is such that the housing can be positioned and angled relatively to a radio frequency device as desired and then locked in place by tightening the nut (or interface) on the device.

Abstract: A system and method are provided for regulating the electrical length of an antenna. The method comprises: communicating transmission line signals at a predetermined frequency between a transceiver and an antenna; sensing transmission line signals; and, modifying the antenna electrical length in response to sensing the transmission line signals. Sensing transmission line signals typically means sensing transmission line signal power levels. In some aspects, the antenna impedance is modified. Alternately, it can be stated that the transmission line signal strength is optimized between the transceiver and the antenna. More specifically, communicating transmission line signals at a predetermined frequency between a transceiver and an antenna includes accepting the transmission line signal from the transceiver at an antenna port. Then, sensing transmission line signals includes measuring the transmission line signal reflected from the antenna port.

Abstract: A device for connecting an antenna to a hazardous enclosure. The device includes an intrinsically safe barrier for protection against electrical surges, and an explosion-proof device enclosure to contain the force of an explosion.

Abstract: A low profile antenna for use in a vehicle remote communication system in accordance with the present invention includes a printed circuit board having a copper ground plane mounted on a first side thereof. A dielectric spacer is mounted to the first side of the printed circuit board. A lineal antenna trace is disposed on the dielectric spacer. The antenna also includes a transmission line having first and second signal conductors. The first conductor is coupled to a feed point on the lineal antenna trace and the second conductor is coupled to both the ground plane and a second point on the lineal antenna trace spaced from the feed point.

Abstract: A wireless communication system for closed environments including a plurality of antennas parallel line coupled to the coaxial cable of a coaxial cable radio frequency transmission system. Each RF coupler assembly includes a quarter wavelength long conductor positioned between the center and outer conductors of the coaxial cable. The conductor is supported by a conductive bar clamped to the exterior of the coaxial cable, and is axially aligned to the cable and insulated from the center and outer conductors by the cable's dielectric core. The conductor is connected to a radiating or non-radiating element which transfers RF energy between the interior of the coaxial transmission cable to a point at which an antenna or other coaxial cable line can be attached.

Abstract: An antenna comprises an antenna feed line having first and second conductors. It also comprises an antenna driver section having a pair of opposing cones. Each of the cones has an apex region and the cones are arranged so that the apex regions are spaced apart and are adjacent. One of the cones is connected to the first conductor and a second of the cones is connected to the second conductor. The antenna also comprises an antenna beam shaper section. This section has a beam shaper element with a beam shaping surface chosen to provide selected antenna operating characteristics and also has a conforming surface that is in substantial conformity with a crotch defined between the two cones.

Abstract: A transmission line structure comprises a plurality of conductive lines over an insulating layer. With three conductive lines, a center conductive line is disposed between the outer conductive lines to define a gap distance therebetween that is less than their height. In a further aspect, a conductive layer (e.g., a ground plane) contacts the insulating layer on a side thereof opposite the plurality of conductive lines. A ratio for the height of the conductive lines relative to the distance therebetween is kept greater than another ratio for the width of the center conductor relative to the thickness of the insulating layer.

Abstract: A wireless communication system for closed environments including a plurality of antennas parallel line coupled to the coaxial cable of a coaxial cable radio frequency transmission system. Each antenna includes a quarter wavelength long conductor positioned between the center and outer conductors of the coaxial cable. The conductor is axially aligned to the cable and insulated from the center and outer conductors by the cable's dielectric core. The conductor is connected to a quarter wavelength radiator supported by a conductive bar clamped to the exterior of the coaxial cable.

Abstract: A broad band antenna uses a bicone antenna configuration as a feed transformer and exponentially tapered reflector fins to radiate the antenna's energy. The bicone antenna design is used to match the antenna's impedance to coaxial cable impedance. The fins function to reduce the traditional bicone antenna diameter. Reflection between the cones and the attached reflector fins as well as return loss are reduced by wrapping the reflector fins with metallic foil.

Abstract: An inventory control system and method that tracks inventories of items with RFID tags, includes a reader unit and an intelligent station that tracks RFID tags to determine item information of items to be inventoried. The reader unit transmits and receives RF signals. The intelligent station includes a first RF antenna connected to the reader unit by a first transmission cable through a first switch, and one or more additional RF antennae connected to the reader unit by the same first transmission cable through additional switches. An inventory control processing unit receives item information from the intelligent stations to update inventory information regarding the items to be inventoried.

Abstract: A choke coupled coaxial connector includes a hybrid transmission line center conductor including an open-circuited transmission line having one-quarter electrical wavelength, which presents an effective short-circuit at a gap in the center conductor structure. The choke coupled connector also includes an open-circuited hybrid transmission line outer conductor also one quarter-wavelength long, which presents an effective short-circuit in a gap in the outer conductor structure. According to an aspect of the invention, certain interior surfaces of the connector are coated with dielectric to prevent galvanic contact and for reduced mating forces. According to another aspect of the invention, the male and female portions of the choke coupled coaxial connector are prevented from rotating. In a particularly advantageous embodiment, an array of choke coupled coaxial connectors.

Abstract: A network of localizers determines relative locations in three-dimensional space to within 1 cm by cooperatively measuring propagation times of pseudorandom sequences of electromagnetic impulses. Ranging transmissions may include encoded digital information to increase accuracy. The propagation time is determined from a correlator circuit which provides an analog pseudo-autocorrelation function sampled at discrete time bins. The correlator has a number of integrators, each integrator providing a signal proportional to the time integral of the product of the expected pulse sequence delayed by one of the discrete time bins, and the non-delayed received antenna signal. With the impulses organized as doublets the sampled correlator output can vary considerably in shape depending on where the autocorrelation function peak falls in relation to the nearest bin. Using pattern recognition the time of arrival of the received signal can be determined to within a time much smaller than the separation between bins.

Abstract: A novel method for producing improved RF transmission lines for satellite beamforming networks and printed circuit antenna(s) comprising the steps of (1) bonding together (a) a central conductor strip or trace comprising a dielectric layer or circuit board having on one or both surfaces thereof conductive strip circuitry; (b) upper and lower core layers of lightweight closed-cell plastic foam bonded to (a), and (c) upper and lower surface layers or faceskins of conductive metal foil or of dielectric material bonded to metal foil layers inside and/or outside, to form ground planes, bonded to the surfaces of the adjacent foam core layers.

Abstract: A bicone antenna that facilitates the passage of cables for at least one other radiating antenna. The bicone antenna has a plurality of inductive shorts spaced approximately one-quarter wavelength (at the cut-in frequency) from the antenna axis. Each inductive short provides a pathway for a cable for another antenna. Consequently, an antenna cable from each of one or more other antennas can be led to a center point on the bicone antenna, directed radially along a cone to an inductive short, led through the inductive short and directed along the surface of the other cone to the center line. The outer conductor of each antenna cable attaches to an antenna surface.

Abstract: An antenna assembly (1) for connection to a wireless communications device (27) for adjusting the signals of amplifiers and line extenders of a broadband communications cable, has, an antenna coil (3) connected in one end of a conducting sleeve (4), a length of coaxial cable (5) having a central conductor (14) connected in another end of the sleeve (4), the sleeve (4) having a force fit connection in an axial bore (16) through a nonconducting housing (6), the coil (3) projecting outward of the housing (6) and being enclosed by an insulating hollow radome (2) that is mounted to the housing (6), and the housing (6) being adapted for connection to an exterior panel (26) of a portable, wireless communications device (27) for adjusting signals of amplifiers and line extenders of a broadband communication cable.

Abstract: A selected length of antenna for a device under test is placed within a conductive inner cylinder, forming an unterminated “input” coaxial transmission line. The inner cylinder is in turn within and coaxial with a conductive outer cylinder, forming an “output” transmission line. The inner cylinder is the center conductor of the output transmission line, and in a region extending beyond the extent of the antenna therein, conically tapers to being a normal center conductor of solid cross section. The outer cylinder matches this taper to maintain a constant characteristic impedance Z0out (say, 50 &OHgr;) for the output transmission line, which then delivers its output signal to a matched terminating load in measurement equipment via either a coaxial connector or an interconnecting length of auxiliary transmission line.

Abstract: The present invention provides a radio communication device having a multi-band swivel antenna assembly. The antenna assembly includes a multi-band radiating antenna element and a multi-band sleeve which allows the antenna to be tuned to multiple resonances. The multi-band antenna element and sleeve are attached to the chassis of the communication device via a coaxial feeding cable which serves to isolate those elements from the chassis.

Abstract: A coaxial IF interconnect structure that is compressible in the z-axis and provides its own environmental seal against moisture and coolant. The structure (50) includes three components, a center conductor (60), dielectric spacer structure (70), and outer conductor shield (80), all fabricated of compressible materials. The center conductor is a compressible metal interconnection element formed by die compressing 1 mil diameter fine wire to a desired shape and density. The coaxial dielectric structure supports the compressible center conductor, and is fabricated from a fluorinated elastomer (FM) known as fluorosilicone. The compressible coaxial outer conductor shield functions as an IF gasket in the form of an round flat washer surrounding the dielectric structure and center conductor.

Abstract: A ridged coaxial transmission line assembly including a plurality of parallel transmission paths is fabricated from an extrusion incorporating a plurality of slotted, longitudinal bores provided with centrally located conductors held in position by insulating stand-offs provides a structure performing the dual functions of electrically integral antenna mast and signal conductors for a linear array of antenna elements supported by the mast.

Abstract: A method and system that provides power to an antenna clearing device through a coaxial cable used to transmit the satellite signals is disclosed. Receiver decoder box for receiving satellite signals via an LNB is connected to the LNB by the coaxial cable. The antenna clearing device is also connected to the coaxial cable. A power source within the box provides power to the LNB and the antenna clearing device via the coaxial cable.

Abstract: An improved coaxial-collinear antenna comprising a pair of continuous inner conductors each having a plurality of dielectric spacers mounted thereon for supporting a plurality of individual outer conductors in coaxial alignment with the continuous inner conductor. The outer conductors are equidistantly spaced along each continuous inner conductor by an amount substantially equal to the length of each outer conductor. The pair of continuous inner conductors are parallel, and the outer conductors mounted on each continuous inner conductor are electrically connected to the other continuous inner conductor between outer conductors consecutively mounted on that other inner conductor.

Abstract: An omnidirectional antenna with minimal gain variation over the 360.degree. azimuth. A plurality of biconical antennas are stacked vertically. A radome covering the antenna and cylindrically encasing the antenna supports the stack of biconical antennas. A bundle of transmission lines is helically wound about the cylindrical periphery of the biconical antennas, preferably at an angle between 37.degree. and 41.degree.. Each biconical antenna is formed by two truncated flared apart reflecting surfaces that are connected by a nonconductive spacing collar between their truncated portions.

Abstract: A dipole antenna is inserted into a waveguide to couple EM energy into and out of a waveguide. The dipole antenna is printed on a substrate of a module that contains electronic components. The substrate includes a coupled coplanar strip transmission line connecting the dipole antenna to a slotline. EM energy is electromagnetically coupled between the slotline and a microstrip transmission line. The EM energy is provided to and from the hermetically sealed electronic components by the microstrip transmission line.

Abstract: A low cost antenna assembly is disclosed which is formed from a flexible wire and a pair of suction cups for supporting the wire in a substantially linear fashion. A feed line couples the wire antenna to a receiver. Further, a method for fabricating the antenna is disclosed.

Abstract: A radio antenna which takes the form of a flexible elongated transmission cable. This cable encloses a pair of conductors which are insulated from each other. The cable is encased in an electrically conductive sheath. The received signal is picked up by the sheath and transmitted through an impedance matching network and into the pair of conductors. The length of the sheath is correlated to a preselected fractional value of the wavelength of the received signal.