Abstract: A radome for providing a relatively wide-band operation which in a preferred embodiment uses at least a pair of panel means mounted adjacent each other, each having a plurality of discontinuous conductive elements applied to a selected surface thereof in an array of parallel paths. The discontinuous elements in each path of the array are interconnected by diode means which can be biased in a non-conductive direction during a first transmit mode and in a conductive direction during a second non-transmit mode. The panels are separated by a distance which is substantially equal to one quarter wave length (.lambda..sub.s /4) at a selected frequency within the wide pass-band of electromagnetic energy which is to be transmitted.

Abstract: A "shutter" type structure for transmitting electromagnetic energy within a selected frequency range and preventing the transmission of such energy outside such range during a first open shutter mode of operation and for preventing the transmission of any electromagnetic energy during a second closed shutter mode of operation. The structure includes an insulative member having an array of symmetrical conductive elements on at least one surface, such elements being interconnected by diode elements in both vertical and horizontal directions. The diodes are placed in their conductive states during the first mode of operation and in their non-conductive states during the second mode of operation.

Abstract: A structure for selectively transmitting electromagnetic energy over a selected frequency range during a first operating mode and for substantially preventing the transmission of electromagnetic energy at any frequency during a second operating mode either by absorption or by reflection of such energy. The structure includes at least one shutter means comprising continuous and discontinuous elements and diode means interconnecting the discontinuous portions of the discontinuous element. The diode means are biased in a non-conductive direction during the first operating mode and are biased in a conductive direction during the second operating mode. The structure can further include filter means which include continuous and discontinuous elements arranged so as to be resonant over the selective frequency range during both operating modes.

Abstract: A structure for transmitting electromagnetic energy within a selected frequency range and preventing such transmission outside such range in which an insulative member has a metallized surface which includes an array of non-metallized regions each having the shape of a Jerusalem cross, the vertical and horizontal cross arms thereof having metallized regions along their length to form non-metallized gaps with the edges thereof.

Abstract: A radome shutter structure for preventing the transmission of electromagnetic energy within a selected frequency range and for permitting the transmission of energy outside such frequency range during a first mode of operation and for permitting the transmission of electromagnetic energy over a relatively wide frequency range which includes such selected frequency range during a second mode of operation. The structure includes an insulative substrate having a symmetrical array of metallized regions, each region preferably in the form of a Jerusalem Cross having discontinuous arms interconnected by diode elements which are placed in a conductive state in the first mode of operation and in a non-conductive state in the second mode of operation.

Abstract: A structure for selectively transmitting electromagnetic energy therethrough which comprises a relatively thin insulative substrate having front and rear surfaces. The surfaces each have a pattern of regions thereon in each of which a first metallized Jerusalem cross is formed. In each region additional metallized Jerusalem crosses are formed in each of the quadrants of the first Jerusalem cross. The dimensions of the Jerusalem crosses on each surface are selected to provide suitable transmission resonances so as to permit transmission of electromagnetic energy through the surface over a selected portion of the frequency spectrum and to prevent transmission outside said portion of the spectrum.

Abstract: A method and an apparatus for measuring the variations of the foetal heart rate particularly during labor. According to this method, an average value is determined from zones where no deceleration occurs. In order to avoid variations due to small parasitic signals, this average value is compared with a filtered value, corresponding to the average value during a small number of periods of the electrocardiogram. This apparatus allows a practitioner to obtain a binary indication on the decelerations of foetal heart rate and accordingly an indication on the possible foetal stress.