A method of detecting a change (that is, an increase or a decrease) in the level of fluid in tissue in a first area of a body includes the steps of: applying electromagnetic energy, preferably in the frequency range of approximately 300 MHz to approximately 30 GHz, to a first volume of the body; measuring a resultant or returned signal; comparing the signal to a reference signal to determine if the fluid level in the tissue has changed. In one embodiment, the method detects changes in the level of fluid in tissue of a body by applying electromagnetic energy to a first volume of the body over a period of time (for example, using an antenna or antennae); measuring a resultant signal or a signal returned from the tissue; and comparing the signal to a reference signal to determine if a level of fluid in the tissue has changed during the period of time.

Detection of fluids in tissue

Tissue sensors house one or more sensor elements. Each element has a housing mounted substrate and a superstrate with a planar antenna between. A transitional periphery (TP) of a superstrate outer surface interconnects a base to a plateau. At least some of the TP has a generally smooth transition. Plural elements are spaced by the housing. Alternately, the superstrate TP is flat, the housing extends to the outer superstrate surface and a shield surrounds the element. The housing is flush with or recessed below the superstrate and defines a TP between the housing and superstrate. A method converts a reference signal to complex form; plots it in a complex plane as a reference point (RP); converts a measurement signal to complex form; plots it in the complex plane as a measurement point (MP); determine a complex distance between the MP and the RP; and compares complex distance to a threshold.

Electromagnetic sensors for biological tissue applications and methods for their use

A dual frequency stacked microstrip patch antenna is comprised of a pair of circular radiating patches separated by a layer of dielectric, the two upper patches being further separated by another layer of dielectric from a pair of separated ground planes. A modal shorting pin extends between the patches and ground planes, and the patches are fed through a pair of feed pins by a backward wave feed network. A pair of modified shape feed through holes in the lower patch through which the feed pins pass result in an extended bandwidth.

Dual frequency microstrip patch antenna with capacitively coupled feed pins

A microwave-frequency microstrip antenna (10) simultaneously usable for both transmitting and receiving microwave-frequency signals that have dual orthogonally polarized components. The components may be either linearly or circularly polarized. A radiating patch (26) is mounted on a first dielectric (12). A ground plane (20) abuts the first dielectric (12) and has two elongated coupling apertures (32,31) at right angles to each other. A second dielectric (22) abuts the ground plane (20) and has embedded thereon two substantially identical conductive planar feed networks (52,51) that are disposed at right angles to each other. At least one additional optional dielectric layer (16,18) having a conductive patch (36,34) may be interposed between the first dielectric (12) and the ground plane (20) for purposes of broadening the bandwidth of the antenna (10). A meanderline polarizer (45) or a 3 dB 90° hybrid coupler (40) may be used for converting from linear polarization to circular polarization.

Planar dual polarization antenna

A three resonator capacitively coupled microstrip antenna structure includes an inverted stacked array of elements with a lowermost driven element directly connected to a transmission line connector, and passive elements stacked above the driven element and separated from the driven element and from one another by dielectric layers. The dimensions, spacings and quality factors of the elements are chosen so that at least one, and possibly two elements are resonant at any given frequency within a desired frequency operating range. The resulting antenna structure offers very broad bandwidth at relatively low VSWR in a compact, rugged package. The manner in which parameters of the stacked antenna structure are specified to achieve desired VSWR bandwidth and radiation efficiency is also described.

Three resonator parasitically coupled microstrip antenna array element

The structure includes a ground plane and at least two stacked microstrip elements with each microstrip element comprising a conducting plane and a layer of dielectric material. The conducting planes and the intermediate dielectric layers are configured so that they resonate at closely spaced frequencies. Each conducting plane in the structure, except the top one, includes an opening which is large enough to permit sufficient electric field coupling to occur between the microstrip elements so that the individual response characteristics of the conducting planes merge to form a broadband response characteristic. The antenna of the present invention thus has a substantially improved bandwidth over prior art microstrip antennas.

James S. Yee

Papers

Microstrip antenna structure having stacked microstrip elements