Abstract: A waveguide to microstrip transition for transferring guided electromagne signals from dominant mode rectangular waveguide to microstrip line and vice versa. A microstrip printed circuit card is disposed in parallel to the narrow walls of a waveguide. The printed circuit card includes a microstrip stepped transformer section followed by a linear taper crossover section. The linear taper crossover section leads into a microstrip line conductor and ground plane for completing the transition.

Abstract: An apparatus for frequency stabilizing a microstrip oscillator using an integrated diplexer as a frequency discriminator. The crossover frequency of the microstrip diplexer is used in a feedback arrangement to stabilize a millimeter-wave oscillator. The diplexer is coupled to the output of the oscillator and detects a shift from the desired oscillator output frequency. This shift in frequency is converted to a voltage for controlling the varactor tuning element of the oscillator to thereby return the oscillator to the desired operating frequency. Means are also provided for sensing a temperature change in the diplexer and for insuring that the oscillator output frequency is maintained at the desired frequency regardless of this temperature change.

Abstract: A waveguide to microstrip transition apparatus in which a waveguide coupled o a microstrip circuit is provided with a mode filter for suppressing spurious modes of electromagnetic signal propagation. The mode filter is attached to the end of the waveguide that is coupled to the microstrip circuit and the mode filter extends over a portion of the microstrip circuit.

Abstract: A microstrip instantaneous frequency discriminator operable at frequencies bove 18GHz. A first power divider divides the input signal into equal power outputs which are used as the inputs to second and third power dividers. One of the outputs from each of the second and third power dividers is used as the input to a 180.degree. hybrid and the other output from each of the second and third power dividers is used as the inputs to a 90.degree. hybrid. The outputs of the 90.degree. hybrid and the 180.degree. hybrid are subsequently processed to provide signals suitable for a visual polar display of the instantaneous frequency and power level of the input signal.