Abstract: A quadrifilar helical antenna comprising two pairs of filars having unequal lengths and phase quadrature signals propagating thereon. A conductive H-shaped impedance matching element matches a source impedance to an antenna impedance. The impedance matching element having a feed terminal at the center thereof from which current is supplied to the two filars of each filar pair disposed about an edge of the impedance matching element and symmetric with respect to a center of the impedance matching element. The impedance matching element further comprises a reactive element for matching the antenna and source impedances.

Abstract: A method and apparatus for dynamically adjusting the impedance between a transmitter's power amplifier (PA) and antenna to efficiently transfer power from the PA to the antenna. The impedance between the PA and the antenna is adjusted based on power level measurements and/or PA direct current (DC) consumption measurements, depending on whether the PA is a linear PA or a switch-mode PA. In another embodiment, a hybrid PA including a first stage linear PA and a second stage switch-mode PA is implemented in a transmitter. The hybrid PA selectively connects the output of the first stage linear PA to one of the input of the second stage switch-mode PA and the output of the hybrid PA, depending on the output power level of the first stage linear PA, the output power level of the hybrid PA, or a requirement indicated by a transmit power control (TPC) command.

Abstract: An RFIC tag includes an IC chip and a thin metal plate. The IC chip is mounted approximately in the center of a slit part on the thin metal plate. The thin metal plate has connecting parts at both longitudinal-direction ends fixed on a metal member by soldering, and the undersurface of the slit part, which has an L-shaped slit thereon, is lifted a predetermined height from the surface of the metal member. The total length (L2+L1+L2) is ¼ or shorter than the communication wavelength ?.

Abstract: A Radio Frequency (RF) structure services an antenna having a characteristic impedance and includes a differential Power Amplifier (PA), a differential Low Noise Amplifier (LNA), and a balun transformer. The differential PA has a differential PA output with a PA differential output impedance. The differential LNA has a differential LNA input with an LNA differential input impedance. The balun transformer has a singled ended winding coupled to the antenna, a differential winding having a first pair of tap connections coupled to the differential PA output and a second pair of tap connections coupled to the differential LNA input, and a turns ratio of the single ended winding and the differential winding. The turns ratio and the first pair of tap connections impedance match the PA differential output impedance to the characteristic impedance of the antenna. The turns ratio and the second pair of tap connections impedance match the LNA differential input impedance to the characteristic impedance of the antenna.

Abstract: Devices and methods are provided to enhance magnetic field communication. One aspect of the present subject matter relates to a method for transmitting and receiving signals using an antenna element electrically connected to a driver and an amplifier. According to various embodiments of the method, a first signal is transmitted from the antenna element and a second signal that was induced in the antenna element is received. Transmitting the first signal includes driving the first signal through the antenna element using the driver, and monitoring the first signal through an input impedance of the amplifier. Receiving the second signal includes reducing the input impedance of the amplifier, and receiving the second signal at the amplifier through the reduced input impedance. Various embodiments shield the antenna element from electric and electromagnetic fields. Other aspects are provided herein.

Abstract: An antenna device which is connected to a radio module performing radio communications with a system using a first band and a system using a second band, has an antenna element which transmits/receives radio signals in the first and second bands. The antenna device has first and second matching circuits corresponding to the first and second bands, and also disposes a switching circuit between the first and second bands and the radio module. A first filter circuit is connected between the first matching circuit and the antenna element. The first filter circuit passes the radio signal in the first band and also attenuates the radio signal in the second band. Meanwhile, a second filter circuit is connected between the second matching circuit and the antenna element. The second filter circuit passes the radio signal in the second band and also attenuates the radio signal in the first band.

Abstract: An antenna configuration for a flip type mobile phone is disclosed. The antenna configuration is designed to reduce, to a hearing aid compatibility (HAC) M3 rating or better, any scattered EM field effects that can cause interference to an active hearing aid. The antenna configuration comprises a halfwave type antenna extendable from the lower portion of the mobile phone. The antenna does not share the same vertical axis as the lower portion of the mobile phone when extended. Rather, it forms a tilt angle (?) that extends the antenna away from the upper portion of the mobile phone creating a greater separation distance between the speaker and the antenna. An antenna feed contact couples the antenna to components within the mobile phone. An antenna matching network can tune and attenuate the antenna configuration to enhance operation in the GSM frequency bands.

Abstract: An impedance matching means according to the present invention is used with an antenna and is realized by a parasitic element (3) for tuning an impedance of the antenna. The antenna comprises a grounding plate (2), an radiating body (1) arranged on the grounding plate (2) and a transmission line (4) coupled to said radiating body (1) and grounding plate (2). The parasitic element (3) formed of a narrow metal sheet and configured as a bridge shape is arranged on the grounding plate (2). The parasitic element (3) has a first and a second ends (311, 321), both of which are electrically connected to the grounding plate (2). The arrangement of the parasitic element (3) results in a change of the impedance of the antenna, so the impedance matching between the antenna and the transmission line (4) can be achieved.

Abstract: The specification and drawings present a new apparatus, method and software product for using a cover antenna (e.g., conductive, metallic, etc.) in an electronic device, with multiple coupled feeds (e.g., dual feed) to the antenna and with one or more switches and a matching circuit. Then it is possible to use a metal plate as a metal cover, e.g., for mobile devices, which will act as an antenna with multiple feedings for cellular and non-cellular radios.

Abstract: An inverted-F antenna (1) used in a portable electrical device formed in a metal patch and includes a radiating element (2), a grounding element (5), and an impedance matching element (3) with an impedance matching space (8). The impedance matching element (3) connects the radiating element (2) and the grounding element (5). A metal foil (7) locates in the impedance matching space and connects to the impedance matching element (3) for modulating impedance matching of the inverted-F antenna. A feeding line (4) includes an inner conductor (40) soldered with the impedance element (3) and a braiding layer (41) soldered with the grounding element (5).

Abstract: An antenna device which is connected to a radio module performing radio communications with a system using a first band and a system using a second band, has an antenna element which transmits/receives radio signals in the first and second bands. The antenna device has first and second matching circuits corresponding to the first and second bands, and also disposes a switching circuit between the first and second bands and the radio module. A first filter circuit is connected between the first matching circuit and the antenna element. The first filter circuit passes the radio signal in the first band and also attenuates the radio signal in the second band. Meanwhile, a second filter circuit is connected between the second matching circuit and the antenna element. The second filter circuit passes the radio signal in the second band and also attenuates the radio signal in the first band.

Abstract: An antenna module has a substrate, first and second coupling elements, and first and second resonant circuits disposed on the substrate. The first and second coupling elements are mounted to the substrate and particularly adapted to couple respective first and second frequency bands to a ground plane through respective first and second ports. The first resonant circuit has a plurality of components having electrical values selected so as to function as a band-pass filter within the first frequency band and to present a high impedance at least in the second frequency band. The second resonant circuit is coupled to the second port and has a plurality of components that have electrical values selected so as to function as a band-pass filter within the second frequency band and to present a high impedance at least in the first frequency band.

Abstract: A method and apparatus for improving the efficiency of a multi-band antenna in a wireless terminal over a wide range of frequencies is described herein. To compensate for the undesirable coupling that occurs in a low frequency band between a parasitic antenna and a primary antenna in certain designs, a matching network is connected to at least one ground port of the multi-band antenna. The matching network controls the multi-band antenna performance based on the current transmission frequency band. In some embodiments, the matching network is configured to operate as an open circuit when multi-band antenna operates in the low frequency band, and to operate as a short circuit when multi-band antenna operates in the high frequency band.

Abstract: An improved antenna structure for RFID tags uses a pair of bent dipole antennas having arms that extend substantially about an outer edge of an RFID substrate. The antennas can be adjusted to resonance at about a half-wavelength of an applied electromagnetic field in the conductive material of the antennas. The antennas can be shorted together using a shorting path, the position of which can be adjusted to adjust an input impedance of the antenna structure. A shorting stub can be used to couple the antenna structure to a supply voltage connection of an RFID device used for the tag. The overall length of the shorting stub can be adjusted to match the impedance of the antenna structure to the impedance of the RFID device. These antenna structures can be used with RFID devices such as CDIP devices and bumped die packages.

Abstract: A wide-band antenna comprises a series-resonant antenna and a resonant circuit. The antenna has a radiative element and a feed pin. The resonant circuit comprises an inductive element connected to the feed pin and a capacitor connected in parallel to the inductive element, which has a center tap for adjusting the impedance of the resonant circuit relative to the antenna impedance. The antenna can be a low-impedance PILA, a helix, monopole, whip, stub or loop antenna. The wide-band antenna can be used for the low (1 GHz range) or high (2 GHz range) band. The antenna can be made to simultaneously cover both 850 & 900 bands with the ground plane small enough to be implemented in a mobile phone or the like. The center tap is either connected to the feed of the antenna or connected to an RF front-end dependent upon the impedance level of the antenna element.

Abstract: Disclosed is an antenna matching device of a folder type portable wireless terminal with a built-in antenna. In the antenna matching device, a ?-type matching circuit is connected between an built-in antenna and a duplexer, one end of a passive element is shunted between the ?-type matching circuit and the duplexer, and an active element opens or connects the other end of the passive element to ground according to the opening or closing of a folder of the terminal. The antenna matching device lowers antenna impedance difference between the opened and closed states of the folder, such that the terminal can constantly maintain its radiation performance, such as VSWR and resonant frequency, regardless of the opened or closed position of the folder.

Abstract: The present invention provides for low loss tunable matching circuits at rf frequencies. Ferro-electric materials are used to produce low loss tunable capacitors and inductors for use in matching circuits.

Abstract: An RF-energy modulation system dynamically adjusts tuned receiving circuits within a plurality of slave devices, thereby regulating the level of power reception in each slave device. The slave devices receive power from a single master device, through coupling of a primary antenna in the master device with a secondary antenna in each slave device. The amount of the power received by each slave device is a function of the antenna separation distance, and is thus different at each slave device location. The RF-energy modulation system monitors the power requirements of the slave device within which the modulation system is included, and modulates the tuning of the secondary antenna to maintain the proper power reception level. Advantageously, such modulation controls the power reception by the slave device, versus dissipating energy already received by the slave device.

Abstract: A wide band mobile antenna assembly having a whip, a base defining a housing, an adaptor extending on top of the base above the housing, and a mounting element extending in the housing. The mounting element has two opposite PCB mounting side surfaces and two opposite coil mounting surfaces. A PCB is mounted on each of the corresponding PCB mounting side surfaces. A matching circuitry is integrated on the two PCBs. The matching circuitry has a conductor for connection to the whip when the whip is inserted in the adaptor, and a conductor for external cable connection. The matching circuitry has a series resonant network operatively connected to a parallel resonant network for increasing a bandwidth of the antenna assembly. The series and resonant networks each have a coil mounted to the corresponding coil mounting surface.

Abstract: Disclosed is a circuit and method for automatic tuning of a resonant circuit in a transceiver having a receiver and a transmitter that includes a power amplifier for driving the resonant circuit. During a transmit mode of the transceiver, a resonance voltage of the resonant circuit is compared to an input voltage signal to the power amplifier to determine an error signal that is converted into a control word. The control word drives an adjustable capacitance bank that is part of the resonant circuit. During a receive mode of the transceiver, the control word value is held constant to substantially maintain resonance of the resonant circuit during operation of the receiver.

Abstract: A system and method is provided for full-duplex antenna impedance matching. The method comprises: effectively resonating a first antenna at a frequency selectable first channel in a first frequency band; generating a first antenna impedance at the first channel frequency; effectively resonating a second antenna at a frequency selectable second channel in the first frequency band; generating a second antenna impedance at the second channel frequency; supplying a first conjugate impedance match at the first channel frequency; and, supplying a second conjugate impedance match at the second channel frequency. For example, the first antenna may be used for transmission, while the second antenna is used for received communications. The antennas effectively resonant in response to: supplying frequency selectable conjugate impedance matches to the antennas; generating frequency selectable antenna impedances; and/or selecting the frequency of antenna resonance.

Abstract: A system and method for providing auxiliary reception in a wireless communications system includes a wireless communications device. The wireless communications device includes a first antenna and a second antenna. The wireless communications device can, for example, establish two-way communications with a wireless communications network. The wireless communications device can also use the second antenna in at least one of a mobile assisted hand off (MAHO), a diversity antenna system and a global positioning system (GPS) system.

Abstract: An electrical signal is fed from one terminal of an antenna element, and the other terminal thereof is terminated by a variable reactance circuit. A reactance value of the variable reactance circuit is changed according to use state of a device to optimally set its directivity. Matching conditions at an electricity feeding point are controlled to match an impedance of the electricity feeding point which fluctuates according to the value of the variable reactance circuit. With the above construction, there are provided an antenna device that is downsized, can control its directivity, and does not deteriorate a communication quality depending on a use state, and a radio communication apparatus provided with the antenna device.

Abstract: A mobile terminal can include a printed circuit board with a reference voltage conductor, an antenna coupled to the first side of the printed circuit board, and a parasitic resonator coupled to the second side of the printed circuit board. More particularly, the parasitic resonator can be connected to the printed circuit board by first and second couplings, which provide first and second impedances, respectively, between the parasitic resonator and the reference voltage conductor. The impedances can be of different values, and can be provided by discrete impedance components. The resonant frequency of the parasitic resonator can be adjusted by altering the impedances of the first and second couplings.

Abstract: A multistage voltage multiplying circuit for single chip passive RF tags is provided, wherein the parasitic capacitance of the diodes of each stage of the voltage multiplying circuit is much less than the parasitic capacitance of the diodes of the preceding stage.

Abstract: An antenna module having at least one reception antenna for converting electromagnetic waves to electrical signals, at least one transmission antenna for converting electrical signals to electromagnetic waves, at least one first coil for adjusting the electrical signals received through the reception antenna, at least one second coil for adjusting the electrical signals transmitted to the transmission antenna, at least one third coil for adjusting a magnitude of impedance for grounding, and one feed point for both transmitting the electrical signals received from the reception antenna to a receiver, and for transmitting electrical signals transmitted from a transmitter to the transmission antenna.

Abstract: A portable receiver includes an antenna to which at least FM broadcast wave is inputted, a matching circuit to which the signal input to the antenna is supplied via minute resistance component, an FM receiver unit with the output of the matching circuit connected thereto, and an earphone connected to the output of the FM receiver unit. The antenna is formed from rigid metal, and its length is shorter than the quarter wavelength of the FM broadcast wave. The matching circuit is formed by reactance element having fine DC resistance. The impedance value of the resistance component as viewed via the resistance component from the matching circuit is nearly equal to the impedance of the matching circuit.

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 differential antenna structure configured to connect to an electronic circuit having differential inputs and output. The antenna structure includes differential feeding points which are connected to the electronic circuit differential inputs/outputs through capacitors thus eliminating the need for baluns. The antenna structure is also configured to connect to multiple differential inputs/outputs thus eliminating the need for a separate antenna for each differential input/output included on an electronic circuit chip set. The antenna structure can include feeding arms which act as differential feeding points. The antenna can also include tongues for adjusting the capacitive part of the antenna to allow for 1 to n frequencies. The antenna can comprise multiple antenna elements in various arrangements and configurations.

Abstract: An antenna window with a high-frequency electric component placed fixedly on one of its surfaces, which is electrically connected to a conductor structure provided on the same surface of the window. The high-frequency component has at least one flat coupling electrode, which is kept at a specific distance from the flat conductor structure conducting high-frequency antenna signals, by an intermediate dielectric layer, to form the electrical connection.

Abstract: Proximity of a user body part can be detected by measuring the effects such proximity has on antenna impedance mismatches. The amount of mismatch affects the amount of RF signal energy reflected back into a transmission line connecting the antenna to a RF signal source. A directional coupler has a main line electrically connected to the transmission line, as well as a coupled line. The directional coupler produces a signal on its coupled line in relation to the magnitude of reflected energy on the transmission line; the amount of reflected energy varies in response to how well the antenna impedance matches the transmission line impedance. A signal detector is electrically connected to the coupled line, and responds to signals produced in the coupled line by the main line. The signal detector output is then used to determine whether a body part is in proximity. Other aspects the invention include an adaptive algorithm to adjust a threshold for proximity determination.

Abstract: An antenna is constituted in which a variable capacitance capacitor portion Ct is connected between an antenna element and a ground. In the variable capacitance capacitor, a plurality of variable capacitance elements using a thin film dielectric layer whose dielectric constant is changed by a voltage applied are connected in parallel with regard to direct current component and in series with regard to high frequency component between an antenna-element-side terminal and a ground-side terminal. The capacitance change ratio of the variable capacitance capacitor that depends on the bias signal can be utilized to the maximum so as to perform impedance matching so that the electrical length of the antenna element is changed, and thus, the operating frequency can be changed. In addition, the antenna having small waveform distortion and intermodulation distortion, high power handling capability and low loss at high frequencies can be realized.

Abstract: An automatic matching and tuning unit (AMTU), which connects the output from a low or medium frequency, high power radio transmitter, which requires a 50 ohm terminating impedance, to an antenna with an input impedance comprising low resistance in series with a high capacitive reactance. Sensors measure the phase angle between the input current and voltage. The inductance of a series connected loading coil is continuously varied to resonate the antenna capacitance. The resulting input resistance is transformed to 50 ohms using a matching transformer and pair of resonant, mutually coupled coils with adjustable mutual coupling. Sensors measure the input resistance and continuously adjust the mutual coupling coefficient to maintain the required 50 ohm input impedance. Sensors measure the antenna current and vary the transmitter power level to keep it constant. A microcontroller processes all of the sensor outputs and provides serial communication with the transmitter.

Abstract: A technique is provided for interconnecting an embedded antenna with external circuitry. The antenna may be formed on an intermediate layer of a layered structure, such as a laminate. The interconnection may be made by providing an aperture through the laminate structure and a terminal pad of the antenna, and making a physical connection by means of a fastener or similar structure extending through the laminate structure. A conductive fluid or other intermediary material such as epoxy may be provided between the fastener and the embedded antenna terminal pad. Similar connection may be made by capacitive coupling with a terminal pad on an exterior surface of the laminate structure.

Abstract: In accordance with the present invention, an aperture rectenna is provided where the substrate is transparent and of sufficient mechanical strength to support the fabricated structure above it. An aperture antenna is deposited on the transparent substrate and a metal-insulator-metal (MIM) diode is constructed on top of the aperture antenna. There is an insulating layer between the aperture antenna metal and the metal ground plane optimized to maximize the collection of incident radiation. The top of the structure is capped with a metal ground plane layer, which also serves as the DC connection points for each rectenna element.

Abstract: In an antenna matching circuit including a parallel resonant section connected to a radiation element constituting an antenna, the parallel resonant section includes a series resonant portion composed of an inductance component and a capacitance component. The series resonant portion realizes antenna matching and band widening. The parallel resonant section can be inserted in a feeder line connected to the radiation element or inserted in a GND line connected to the radiation element.

Abstract: A wireless device includes a first antenna element resonating with a first frequency, a first feeding point coupled to the first antenna element and disposed on a ground plane in the wireless device, and a first matching circuit of which its first end is coupled to the first feeding point. The wireless device also includes a second antenna element resonating a second frequency higher than the first frequency, a second feeding point coupled to the second antenna element and disposed on the ground plane, a second matching circuit of which one end is coupled to the second feeding point, and a radio circuit coupled via a transmission line to a common connection point shared by respective second ends of the first and second matching circuits.

Abstract: Disclosed is a circuit and method for continuous automatic tuning of a resonant circuit. A resonance voltage of the resonant circuit is phase shifted by a predetermined phase shift ? degrees and an input voltage signal to a power amplifier driving the resonant circuit is phase shifted by ?±90 degrees to place the signals in quadrature. The phase shifted signals are mixed to obtain a error signal. The error signal is compared to a predetermined voltage range in order to generate control signals for a control word generator, such as an up-down counter. The control word generator produces a control word that drives a capacitance bank that is part of the resonant circuit. The present invention continuously automatically adjusts the capacitance of the capacitance bank to tune the resonant circuit.

Abstract: A matching device causes an antenna to match a receiving section arranged to receive a signal in a first frequency band and a signal in a second frequency band lower than the first frequency band. The matching device includes a first terminal arranged to be connected to the antenna, a first inductor connected between the first terminal and a first node, a second inductor connected between the first node and a ground, a first capacitor connected between the first node and a second node, a second terminal arranged to be connected to the receiving section, the second terminal being connected to the second node, and a third inductor connected between the second node and the ground. The second inductor has a capacitive impedance in the first frequency band, and has an inductive impedance in the second frequency band. This matching device can supply a signal in the second frequency band received by the antenna to the receiving section with a small loss.

Abstract: A multi-band inductive circuit in an integrated circuit, including at least two parallel branches respectively including a first inductance and a second inductance in series with a capacitor, the two inductances being coupled to each other.

Abstract: According to the present invention, the resistance to interference of a transmitting device, which is particularly embodied as a high frequency transmitter with a transmitter amplifier may be improved, whereby a loss-affected network, for example, in the form of a matching resistance, is coupled to the output of the transmitter amplifier, particularly in the case of low output power of the transmitter amplifier, in order to introduce an impedance-matching at the output of the transmitter amplifier. As such, the reflection of an interference signal coming from a transmitter antenna at the output of the transmitter amplifier can thus be reduced.

Abstract: Disclosed is a mobile communication wide band antenna that comprises a radio wave radiator for receiving transmission signals and power and radiating radio waves corresponding to the transmission signals; and an operating state display for receiving the radio waves radiated by the radio wave radiator and displaying operating states of the radio wave radiator according to the received radio waves. The radio wave radiator comprises a ground surface for functioning as ground; a radiation element supported by the ground surface to have a first gap from the ground surface and radiating the radio waves; and a microstrip feeder supported by the ground surface, having a second gap and a third gap from the ground surface, and for receiving the transmission signals and the power and having an electromagnetic coupling with the radiation element, the third gap being provided to be located between the ground surface and the radiation element.

Abstract: A multi-frequency antenna having a small size, light weight and excellent productivity and being suitable for transmitting and receiving electric waves in Ghz band, is constituted such that an orthogonal coordinate X-Y is set, a first antenna element 21 having an electric wavelength of ?a/4 and a second antenna element 22 having an electric wavelength of ?b/4 are placed in parallel to the X axis respectively, one edge of each of said elements is positioned near the Y axis, said two elements are connected electrically with a ground plate 8 by a short-circuit line 4 along the Y axis, a point where an impedance is 50 ? (code 50) of the first antenna element 21 and a point where an impedance is 50 ? of the second antenna element 22 are made to be a power feed point respectively, and said power feed points are connected with a coaxial cable 7 through a power feed line 6.

Abstract: An antenna structure (142) having a retractable element (124) and a reactive antenna circuit (118). The antenna structure components conductively disconnect the reactive circuit (118) from the RF drive (138) when the retractable element (124) is extended, and conductively reconnect them when the retractable element (124) is retracted. The retractable element (124) is also conductively connected to the RF drive (138) when the retractable element (124) is extended and conductively disconnected when the retractable element (124) is retracted. The reactive circuit (118) maintains substantially similar impedance to the retractable element (124) for an RF antenna circuit when the retractable antenna (142) is in both the extended and the retracted positions.

Abstract: An antenna device comprises an antenna element formed in a sufficiently shorter length as compared with the wavelength of transmission or reception wave, a resistor, a matching circuit including at least a reactance element, and an output terminal connected to outside, which are connected in series in this sequence. As a result, an antenna device of smaller size and small loss is obtained.

Abstract: A circuit arrangement for deriving electrical power from a received electromagnetic field to power a transponder includes a detuning unit connected between two antenna terminals for limiting the power absorbed by the antenna. The detuning unit includes a component having an impedance that passively varies or is actively varied dependent on the field strength of the field prevailing at the antenna. One arrangement of the detuning unit includes two varactor diodes connected anti-parallel between the antenna terminals. Another arrangement of the detuning unit includes a varactor arranged in series between two capacitors between the antenna terminals, a field strength detector, and a controllable voltage source connected to apply to the varactor a control voltage that varies depending on the detected field strength. Thereby, the input impedance varies depending on the field strength, to achieve impedance matching for a low field strength, and a mis-matched condition for a high field strength.

Abstract: Devices and methods are provided to enhance magnetic field communication. One aspect of the present subject matter relates to a method for transmitting and receiving signals using an antenna element electrically connected to a driver and an amplifier. According to various embodiments of the method, a first signal is transmitted from the antenna element and a second signal that was induced in the antenna element is received. Transmitting the first signal includes driving the first signal through the antenna element using the driver, and monitoring the first signal through an input impedance of the amplifier. Receiving the second signal includes reducing the input impedance of the amplifier, and receiving the second signal at the amplifier through the reduced input impedance. Various embodiments shield the antenna element from electric and electromagnetic fields. Other aspects are provided herein.

Abstract: A broadband loaded antenna and matching network with related methods for design optimization are disclosed. The loaded antenna structures may preferably be either monopole or dipole antennas, but the particular methods and techniques presented herein may be applied to additional antenna configurations. The load circuits positioned along an antenna may comprise parallel inductor-resistor configurations or other combinations of passive circuit elements. A matching network for connecting an antenna to a transmission line or other medium preferably includes at least a transmission line transformer and a parallel inductor. Various optimization techniques are presented to optimize the design of such broadband monopole antennas. These techniques include implementation of simple genetic algorithms (GAs) or micro-GAs. Component modeling for selected components may be effected through either lumped element representation or curved wire representation.

Abstract: An antenna including a feed network; four or more helical radiating elements, and four or more impedance matching stubs each coupling a respective radiating element to ground in parallel with the feed network. The shunt stubs provide a reactance in parallel with the radiating elements to rotate the desired frequency locus about a constant admittance curve. Specifically, the shunt stubs rotate the desired frequency locus from a low resistance, capacitive impedance to 50 ohms purely resistive. The length of the stubs can be adjusted to control the inductance.

Abstract: An RF antenna coupling structure includes a first transformer, a second transformer, and a transformer balun. The first transformer includes a primary winding and a secondary winding, wherein the primary winding of the first transformer is operably coupled to a power amplifier, and wherein the secondary winding of the first transformer has a desired output impedance corresponding to the operational needs of the power amplifier. The second transformer includes a primary winding and a secondary winding, wherein the primary winding of the second transformer is operably coupled to a low noise amplifier, and wherein the secondary winding of the second transformer has a desired output impedance corresponding to the needs of the low noise amplifier. The transformer balun includes a differential winding and a single-ended winding, wherein the differential winding is operably coupled to the secondary windings of the first and second transformers and the single-ended winding is operably coupled to an antenna.