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: 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 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: 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: 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: An artificial anisotropic dielectric material is used as a microstrip patch antenna substrate and can achieve dramatic antenna weight reduction. The artificial dielectric is comprised of a periodic structure of low and high permittivity layers. The net effective dielectric constant in the plane parallel to the layers is engineered to be any desired value between the permittivities of the constituent layers. These layers are 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. Substrate weights can be reduced by factors of from 6 to 30 times using different types of high permittivity layers. This concept has numerous applications in electrically small and lightweight antenna elements, as well as in resonators, microwave lenses, and other electromagnetic devices.

Abstract: A patch antenna is provided with one or more tuning strips spaced therefrom and RF switches to connect or block RF currents therebetween. When a control system for the antenna selectively connects and isolates RF currents between certain of the tuning strips and the patch, the tuning strips change the effective length of the patch and thus the antenna's resonant frequency, thereby frequency tuning the antenna electrically over a relatively broad band of frequencies. The control system includes circuitry for rapidly switching the antenna to a desired frequency with minimal delay and with superior isolation from the antenna, making it suitable for use in DAMA, TDMA, and other frequency hopping applications.

Abstract: An oscillator having the ability to oscillate at a plurality of discrete frequencies in response to an applied digital signal is disclosed. A crystal-controlled, resonant circuit utilizing passive components as frequency determining elements and a PIN diode switching scheme allows the oscillator to demonstrate a tendency for each of the plurality of discrete frequencies to drift equally in response to temperature changes. A two-transistor, emitter coupled amplifying section uses a current mirror for biasing and provides an impedance matching network.