Abstract: Apparatus and method for eliminating an interference signal from a desired signal where a difference of polarization exists or can be made to exist. The desired signal is received on a first antenna of appropriate polarization and the interference signal is received via another port of the same antenna or a second antenna polarized ninety degrees away from the first. The signal received via the other polarization is adjusted for amplitude and phase so that all interference will be cancelled when both signals are subtracted in a summing junction. In the case where the interference and desired signals do not have polarization differences, provision is made to change the polarization of the desired signal.

Abstract: This invention relates to automatic direction finding methods and systems for an electromagnetic or acoustic signal source by utilizing the concept of adaptive nulling of a narrow or wideband signal received by one sensor from the same signal received by the other, along with appropriate adjustments, in a two-sensors-interferometer. Plurality of sensors can be used to measure two orthogonal angles of arrival of a signal. Inventive methods and devices permit singling out a particular signal of interest among others by allowing a frequency tuning and selective amplification of the particular signal of interest without destroying the differential phase or time delay between the signals received by the sensors that determine the angle measurement. A high degree of signal cancellation during the adaptive nulling process permits a correspondingly high degree of accuracy and resolution for the angle measurement and also permits a relatively short baseline for the interferometer.

Abstract: Devices and methods for selectively reducing an electromagnetic or acoustic interference present in a transmission line by an active adaptive means, are described. For the electromagnetic interference, the transmission line may include a waveguide carrying a desired signal along with an undesired interference, the objective of the invention being to reduce the interference selectively at the output of the transmission line without affecting the desired signal substantially. Similarly, for an acoustic interference, the transmission line may include an exhaust pipe of an auto or Diesel engine carrying an undesired acoustic interference or noise, the objective of the invention being to reduce this noise at the output of the pipe.

Abstract: Apparatus and methods for combining incoherent signals having different carrier frequencies but a common modulation to obtain a coherent summation of the modulations of such signals are described. The apparatus comprises adaptive means of changing the carrier frequencies and corresponding phases of various signals to a common carrier frequency and a common phase, thus enabling the coherent summation of the common modulation and enhancing, thereby, the level of received information content. When the incoherent signals are transponder-signals, radiated from an object or platform in response to a modulated interrogating signal, and are obtained by different frequency offsets from the interrogating signal carrier frequency, the particular offset frequencies being unique to that object or platform, the ability combining of modulations coherently provides a means of unique identification of the object or platform.

Abstract: Devices and methods for minimizing multifrequency acoustic or electromagnetic noise that is propagated from its source to a remote region where the noise is to be abated by adaptive means are described herein. The noise minimization is achieved by sampling a noise, synthesizing from this sample a counternoise, the source of which is close to the noise source, and allowing the counternoise to propagate toward said region such that the noise and counternoise cancel each other as they arrive at said region. A closed-loop control is used to adjust the amplitude and time delay, or phase in case of monochromatic noise, of the counternoise during the synthesis, until the residual noise at said region becomes zero. For closed-loop control, the residual noise is transmitted back to the counternoise source by a communication link so that it can be used for said synthesis of the counternoise.

Abstract: Apparatus and methods for selective removal of specific biological cells or specific antigens or antibodies, from fluid containing their mixture with other biological cells and particulates are described. Filtration by this biochemical filter system is effected in a continuous closed-loop fluid flow path. The apparatus described herein comprises a source of fluid containing specific biological cells, antigens or antibodies to be removed; a source of complementary cells or complementary antibodies for the antigens and complementary antigens for the antibodies which can form large agglutinates following a biochemical reaction a reaction chamber providing conditions favorable for fast clump formation following the reaction; a filter for trapping large agglutinates; one or more pumps to regulate various flow rates; and necessary connecting links to form a closed-loop fluid flow path that includes the sources of biological cells, antigens or antibodies and complementary cells, reaction chamber, and filter chamber.

Abstract: This is an automatic direction finder comprising a separately located first and second sensor means for receiving a first and second representation signal from a remote electromagnetic signal source, an error correction loop means connected to the first and second sensor means for nulling the second representation signal in the second sensor means, and an indicator means responsive to the error correction loop means for computing and displaying an off-boresight direction of the electromagnetic signal when the second representation signal is substantially nulled at the second sensor means.

Abstract: The present invention is a method and apparatus for separating a plurality of radio frequency signals, comprising N number of signal collectors, each signal collector receiving the plurality of signals from a location different than the other signal collectors, and N being an integer from 2 to infinity; N number of transmission means, each transmission means conducting the signals received from one signal collector; and, N (N-1) number of signal cancellation means, each signal cancellation means having reference, error input and output lines, the reference line coupled to one transmission means and the error and output lines coupled to another transmission means; the signal cancellation means and transmission means being interconnected so that each transmission means is coupled to the output and error lines of N-1 signal cancellation means and the reference line of N-1 other signal cancellation means, and no signal cancellation means having the same transmission means coupled to their output and reference lin

Abstract: A low frequency air-to-air and air-to-ground communication system is described. The propagation characteristics of low frequencies and very low frequencies are such that less signal attenuation is encountered at intercontinental ranges when the system is operating in the TE mode as compared to the TM mode. The TE mode is defined as having a dominant vertical magnetic field component and the TM mode is defined as having a dominant vertical electric field. Also, the receiver in an aircraft is subjected to less ambient noise when it is positioned to receive the TE mode. However, ground transmitters are inefficient at transmitting and receiving the TE mode because the ground image tends to cancel out the transmitted and received signals.

Abstract: Apparatus and method for eliminating an interference signal from a desired signal where a difference of polarization exists or can be made to exist. The desired signal is received on a first antenna of appropriate polarization and the interference signal is received via another port of the same antenna or a second antenna polarized ninety degrees away from the first. The signal received via the other polarization is adjusted for amplitude and phase so that all interference will be cancelled when both signals are subtracted in a summing junction. In the case where the interference and desired signals do not have polarization differences, provision is made to change the polarization of the desired signal.