Abstract: Apparatus and methods are disclosed for use in electronic circuits that contain Generalized Impedance Converters and shape frequency response. The combined effect of two Generalized Impedance Converters 30 and 34 with their outputs connected to a coupler 32 simulates coupled capacitors FIG. 2(B) or coupled inductors FIG. 2(A) through impedance scaling. The resistors used in the coupler 32 define the degree of coupling between the first and second Generalized Impedance Converter 30 and 34 respectively. In one embodiment, simulated coupled inductors 96, 98 and 100 are used in a bandpass circuit along with additional R-C devices to control upper and lower sideband attenuation and resonant frequency. Here, the resistors in the coupler device 86 simulate the mutual inductance 98 of coupled inductors.

Abstract: The invention is a device for reducing modulation of high frequency signals induced by helicopter rotor blades made of high strength composites and having a metalized leading edge. The device uses a segmented metalized leading edge. The segments are electrically connected by reactive elements selected to alter the self-resonant frequency of the rotor blade and to reduce the antenna Q to a non-interfering frequency range. The reactive elements use "lossy" materials to absorb energy to reduce the magnitude of radio frequency signal induced currents.

Abstract: An antenna comprising a plurality of sections, each section comprising first and second coil forms forming a triangle with a ground plane and having a continuous ribbon cable and a multiconductor cable wound in helical fashion about the coil forms. Selected conductors of the multiconductor cable are terminated at selected sections and connected to PIN switching diodes to switch selected amounts of inductance out of the circuit, thereby providing multiple selectable frequencies of operation for the antenna.

Abstract: A supplementary frequency acquisition circuit in the form of a frequency difference detector called a single sideband quadricorrelator is provided. When used in conjunction with a phase-locked loop of a conventional spread spectrum demodulator, this circuit allows for the rapid acquisition and accurate tracking of the center frequency of a spread spectrum suppressed-carrier bi-phase PSK signal. The invention cancels spurious sum and difference frequency components impulsed at the data rate as well as double difference frequency component and other modulation products without filtering. By eliminating the need for supplementary low pass filtering, the present invention provides rapid acquisition of the suppressed-carrier signal and provides a frequency difference output at twice the amplitude of comparable prior art systems. The tracking error or frequency difference (.omega..sub.i -.omega..sub.o) is obtained by differentiating the quadrature signal and multiplying by the in-phase signal component rotated 180.