Abstract: An electromagnetic bandgap material is electrically attached to an edge, and enables high isolation between antennas due to the attenuation of surface waves. The disclosed embodiments further provide narrow reactive edge treatments in the form of artificial magnetic conductors (AMCs) whose physical width is less than 1/10 of a free space wavelength for the frequency of surface currents intended to be suppressed. These embodiments still further provide several AMCs suitable for this purpose, along with several exemplary manufacturing techniques for the AMCs.

Abstract: An antenna comprises a conductive member having an opening for radiating an electromagnetic signal. A circuit board is spaced apart from the conductive member by less than one-quarter wavelength of the electromagnetic signal. The circuit board has a series of conductive cells for suppressing at least one propagation mode propagating between the conductive member and circuit board over a frequency bandwidth range defined by a geometric arrangement of the conductive cells.

Abstract: An artificial magnetic conductor is resonant at multiple resonance frequencies. The artificial magnetic conductor is characterized by an effective media model which includes a first layer and a second layer. Each layer has a layer tensor permittivity and a layer tensor permeability having non-zero elements on the main tensor diagonal only.

Abstract: An artificial magnetic conductor includes a frequency selective surface having a frequency dependent permeability &mgr;1z in a direction normal to the frequency dependent surface, a conductive ground plane, and a rodded media disposed between the frequency selective surface and the conductive ground plane.

Abstract: A tunable artificial dielectric material achieves the weight reductions made possible in U.S. Pat. No. 6,075,485 and further achieves even higher resonant frequency tuning ratios. In one embodiment of the invention, the artificial dielectric substrate for a patch antenna comprises alternating low and high permittivity layers, with the high permittivity layers each comprised of printed capacitive Frequency Selective Surface (FSS). An example FSS of the invention has a voltage tunable effective sheet capacitance by virtue of varactor diodes integrated into each unit cell. By appropriate adjustment of the bias voltage across the varactor diodes, the amount of the electric field stored in the substrate can be varied, which further varies the resonant frequency of the patch antenna.

Abstract: A direct current (DC) inductive shorted patch antenna includes a direct current inductive (DCL) frequency selective surface (FSS) forming the radiating element, a ground plane, a feed, and a radio frequency (RF) short to the ground plane positioned between the feed and the radiating element.

Abstract: An antenna beamformer is disclosed that uses controllable time delay elements distributed in a planar fractal feed network between the input port and multiple output ports. The use of time delay elements, rather than phase shifting elements, allows the beamformer to maintain a constant steering angle independent of frequencies over a broad range of frequencies. In addition, fewer control signals are used to control all of the time delay elements due to distributing the time delay elements throughout the fractal feed network, rather than grouping the delay elements near the output ports.

Abstract: An artificial magnetic conductor is resonant at multiple resonance frequencies. The artificial magnetic conductor is characterized by an effective media model which includes a first layer and a second layer. Each layer has a layer tensor permittivity and a layer tensor permeability having non-zero elements on the main tensor diagonal only.

Abstract: An artificial anisotropic dielectric material can be used as a microstrip patch antenna substrate. The artificial dielectric can be easily designed for the purpose of weight reduction. Preferably, the artificial dielectric is comprised of a periodic stack of low and high permittivity layers. The layers can be oriented vertically below the patch to support electric fields consistent with desired resonant modes. Substrates may be engineered for both linearly and circularly polarized patch antennas. Antenna weight can be reduced to ⅙th up to {fraction (1/30)}th of the original weight using different types of high permittivity layers. This concept has numerous applications in electrically small and lightweight antenna elements such as PIFA antennas. In accordance with one aspect of the invention, the artificial dielectric is comprised of an interlocking structure of low and high permittivity layers for ease of assembly and for overall stability.

Abstract: In an artificial magnetic conductor, the distance between the frequency selective surface and the ground plane is mechanically varied to adjust the effective inductance or capacitance of the structure and thus the resonant frequency of the device.

Abstract: An antenna system includes a beamformer having a feed port and a one-dimensional or two-dimensional arrangement of output ports, radiating antenna elements coupled with output ports of the beamformer, and an antenna control unit coupled with the beamformer to steer a beam of the antenna system. The antenna system forms an electrically steerable, phased array antenna having a beam steering angle which is constant over a very broad band of frequencies. Specific applications for the antenna system include satellite communications including tracking low earth orbiting satellites, radar systems and data links using a steerable antenna for self-installation, self-healing and adaptation.

Abstract: A frequency reconfigurable artificial magnetic conductor (AMC) includes a ground plane, a spacer layer disposed adjacent the ground plane and a plurality of vias in electrical contact with the ground plane and extending from a surface of the ground plane in direction of the spacer layer. The AMC further includes a frequency selective surface (FSS) disposed on the spacer layer and including a periodic pattern of bias node patches alternating with ground node patches, the ground node patches being in electrical contact with respective vias of the plurality of vias, and components between selected bias node patches and ground node patches, the components having a capacitance which is variable in response to a bias voltage. A network of bias resistors between adjacent bias node patches provides the tuning voltage.

Abstract: In a planar inverted F antenna (PIFA), the feed and RF grounding connections are reversed yielding improved performance. Relative positioning of these connections is selected to tailor the characteristics of the antenna, such as resonant frequency and impedance bandwidth.

Abstract: An artificial magnetic conductor is resonant at multiple resonance frequencies. The artificial magnetic conductor is characterized by an effective media model which includes a first layer and a second layer. Each layer has a layer tensor permittivity and a layer tensor permeability having non-zero elements on the main tensor diagonal only.

Abstract: A patch antenna is composed of a segmented patch and MEMS switches which are built on a substrate. The patch segments of the segmented patch can be electrically connected to each other by the MEMS switches to form a contiguous patch and optional tuning strips and to connect or block RF between the contiguous patch and the optional tuning strips. When RF is connected between the tuning strips and the contiguous patch, the tuning strips increase the effective length of the contiguous patch and lower the antenna's resonant frequency, thereby allowing the antenna to be frequency tuned electrically over a relatively broadband of frequencies. When the tuning strips are connected to the patch in other than a symmetrical pattern, the antenna pattern of the antenna can be changed. In another aspect of the invention, the optional tuning strips are continuous structures that are formed by connecting patch segments using switches.

Abstract: A bandpass radome that reduces the number of spurious resonances, and that tends to suppress Transverse Magnetic TM and Transverse Electric TE surface waves, is described. In one embodiment, the radome includes an inductive FSS ground plane layer. First and second capacitive FSS layers are disposed above the inductive ground plane layer. Third and fourth capacitive FSS layers are disposed below the inductive ground plane layer. In one embodiment, the capacitive FSS layers use patch elements and some or all of the FSS patch elements above and below the inductive ground plane layer are electrically connected to the inductive ground plane layer by a conducting posts. The conducting posts form a rodded medium to suppress TM and TE surface waves. In one embodiment the total thickness of the bandpass radome is less than &lgr;/20 at the center frequency of the passband.

Abstract: The invention provides an artificial magnetic conductor (AMC) system and method for manufacturing. The AMC has a post plane with posts and slots. The posts are operatively disposed adjacent to conductive shapes on one or more frequency selective surfaces. The posts formably extend from the post plane.

Abstract: A loudspeaker with an overlay or bifilar wound split voice coil, a coil for driving a higher frequency speaker such as a tweeter, and a push-pull audio amplifier circuit directly coupled with the coils. The configuration of the split coil provides two coaxial voice coils that produce a transformer coupling at high frequencies. This coupling compensates for the normally experienced increased input impedance at high frequencies and results in a fairly constant input impedance over a large frequency range, facilitating uniform power transfer to the speaker. The high frequency voice coil is coupled across the split coaxial coils and is energized at high frequencies by a combined signal which includes the signal directly applied to one of the coaxial coils and the induced signal in the other coaxial coil.

Abstract: A loudspeaker with an overlay voice coil and directly coupled push-pull audio amplifier circuit is disclosed. The overlay configuration compensates for increased input impedance at high frequencies by introducing a transformer coupling between two co-axial voice coils. The resultant input impedance remains fairly constant over a large frequency range, thereby insuring uniform power transfer to the speaker.

Abstract: An angularly adjustable vehicle mirror with vibration damping. A casing, adapted to be secured in a mirror housing, supports a mirror back member for pivoting by a mechanism within the casing. Two rigid projections from the casing have surfaces extending generally in the direction the back member moves when it pivots relative to the casing. Vibration dampers are carried by the mirror back member remote from the pivot point of the mirror. Each damper extends rearwardly of the mirror into contact with the surface of a projection to inhibit vibration of the mirror. The vibration damping members are rigid in the direction the mirror moves but are flexible or articulated for movement transversely of the direction of mirror movement and are biased against the surfaces in slidable, frictional, engagement.