Abstract: A waveguide low pass filter is composed of an assembly of an outer waveguide, an inner waveguide shorter in length than the outer waveguide, and a printed circuit filter substrate. The outer and inner waveguides have split block constructions. The inner waveguide is mounted within the outer waveguide so as to form a constriction within the outer waveguide limiting propagation of energy within the outer waveguide to the fundamental TE.sub.10 waveguide mode. The printed circuit filter substrate is mounted to extend longitudinally between the assembled split halves of the respective outer and inner waveguides, and is constructed of a substantially planar dielectric substrate element and upper and lower conductive plate elements on the substrate and lying in the plane thereof. The conductive plate elements define a tapered dual ridge transformer section. The lower plate element has longitudinally spaced vertical slots formed therein defining an open stub slotted filter array.

Abstract: The position of a printed circuit filter array is mechanically moved from e sidewall to the center of the waveguide to thereby tune the cut-off frequency of the waveguide. An array of printed circuit elements is placed in the E-plane inside a waveguide and serves as a high pass filter. The printed circuit elements make no contact with the guidewalls that are suspended on a dielectric substrate. A sidewall screw tuner is mechanically coupled through the waveguide wall to the dielectric substrate to physically move the dielectric substrate containing the filter elements to selected positions within the waveguide. The substrate may be moved from a position adjacent the waveguide narrow wall wherein no variation of waveguide cut-off frequency occurs to a position at the center of the waveguide wherein the increase in the waveguide cut-off frequency is maximized.

Abstract: A waveguide bandpass filter employs a waveguide section and a printed cirt filter assembly having a dielectric substrate positioned in the waveguide between the narrow walls thereof and a row or array of half-wavelength conductive metal plate elements lying in a surface plane of the dielectric substrate that is oriented substantially parallel to narrow walls and orthogonal to broad walls of the waveguide. The half-wavelength conductive metal plate elements, defining a parallel resonant array, are spaced in non-conductive relation from one another and from the broad and narrow walls of the waveguide so as to divide and transform a dominant waveguide propagation mode into a transformed propagation mode that approximates upper and lower microstrip sections interconnected by a metallic conductor.

Abstract: A fin line circuit card containing a fin line slot feeds a dipole antenna ich extends a quarterwave outside the waveguide and provides an energy beam focal point at or near the open end of the waveguide. The dipole antenna thus maintains a wide and nearly constant beamwidth, low VSWR and a circular symmetric radiation pattern for use in electronic warfare direction finding and surveillance applications.

Abstract: Arrays of printed circuit elements are placed in the E-plane inside waveges to reflect and pass selected bands of frequencies. The elements make no contact with the guide walls but are suspended on dielectric substrates and are held in place with foam dielectric.

Abstract: A slotline directional coupler is disclosed that introduces a 180.degree. phase reversal in one of the arms of the coupler in order to isolate opposite ports of the coupler. One of the arms of the coupler is split and a quarter wave shorted slotline is added to each portion of the split coupler arm. The split coupler arm is bridged by a short conductive strap that, in a first embodiment, is grounded on both ends to the slotline ground plane or in a second embodiment, is extended to appear as though grounded. In the first embodiment, the conductive strap is separated from the ground plane by air. In the second embodiment the dielectric substrate of the coupler separates the strap from the ground plane. The conductive strap serves as a slotline-to-microstrip-to-slotline transition which introduces a 180.degree. phase shift in a signal propagating through it.

Abstract: A microwave hazard alarm that indicates the presence of microwave radiation from microwave ovens or other transmitting sources by means of a light indicator. The alarm comprises a handheld microwave receiver including an antenna, a detector, a battery powered amplifier, a light emitting diode and a unique circuit connecting the components on a small printed circuit board. The indicating light emitting diode (LED) blinks on and off periodically when the detected microwave power level is safe and below a predetermined power level. At greater power levels the LED stops blinking and glows continuously.

Abstract: A broadband high pass microwave filter and method of manufacturing thereof hat maximizes the frequency separation between the desired passband of the filter and spurious passbands. A strip of dielectric material has alternately spaced capacitor plates formed on both sides thereof such that parallel plate capacitors are formed at the overlapping sections of the capacitor plates. The dielectric strip is folded in accordian-like fashion and inductive leads are electrically connected to the capacitor plates at each of the folds. The folded dielectric strip is mounted on an MIC substrate, the end plates of the strip are electrically connected to microstrip conductors on the substrate and the inductive leads are connected to the ground plane of the microstrip substrate to thereby form the high pass microwave filter.

Abstract: A microwave or other r.f. radiation detector in which a tunnel diode or other negative resistance device exhibiting the proper I-V (current-voltage) characteristics is biased in the positive resistance region near the voltage point at which the peak current occurs. Microwave or any other r.f. signal is picked up and detected by the tunnel diode such that an oscillation circuit connected thereto is caused to oscillate. The frequency of oscillation varies in accordance with the amplitude of the detected r.f. and is monitored with an earphone and/or a meter.

Abstract: A microstrip hybrid directional coupler in which the 180.degree. phase sh is effectuated by a twisted pair of parallel conductors.

Abstract: A transition apparatus for changing from a waveguide to a coaxial connect A tapered or stepped ridge waveguide section is electrically connected to a section of microstrip which is electrically connected to a coaxial connector, the coaxial connector being in line with the waveguide.

Abstract: A balanced microcircuit mixer for down converting microwave and millimeter ave frequencies. A pair of beam lead diodes and an IF filter are mounted on a reverse-phased hybrid ring coupler providing a wide bandwidth mixer.

Abstract: This invention is a mechanism for connecting a spiral antenna to a wavegu with very low transmission and reflection losses. The invention provides a smooth broadband transition from a spiral, balanced transmission line through a printed circuit fin-line transition and then to a waveguide TE.sub.10 E-plane transition and extends the use of spiral antennas to millimeter wave frequencies.