Abstract: A four-port folded interdigitated coupler has two short conductive strips and three full length conductive strips disposed between the short strips. The full length strips are 1/4 wavelength long at a design frequency. The sum of the lengths of the short strips is 1/4 wavelength at that design frequency. The ends of the short strips remote from the ports are connected together and to the center one of the three full length strips by conductive jumpers. In one embodiment the two full length strips which are not connected to the short strips are connected by a conductive jumper at substantially the same longitudinal position as the jumpers which connect the ends of the two short strips. In this embodiment, the two short strips may have equal lengths or they may have unequal lengths. When their lengths are unequal, their jumpers and the associated jumper between the two outer full length strips are positioned off-center with respect to the longitudinal length of the full length strips.

Abstract: An N-way, lumped element, matched, isolated branch power divider in planar form is disclosed. Lumped inductors are disposed on the top surface of a dielectric substrate, an isolation resistor network is disposed on the bottom surface of the substrate and the substrate is suspended above a ground conductor by lumped element capacitors. The capacitance values of the capacitors and the inductance values of the inductors are selected to provide between the common terminal and each branch terminal a lumped element .pi. network transmission line having a phase shift of about 90.degree. at frequencies within an operating range of frequencies.

Abstract: An electronically adjustable capacitor (varactor), an active element such as a Field Effect Transistor arranged to exhibit negative resistance, and an inductor are arranged as a frequency tunable resonator suitable for use at microwave frequencies. The negative resistance of the active element may be adjusted to compensate for the resistance of the other resonator components such that the resonator exhibits very high Q and therefore high selectivity and low loss. The resonator may be used as a filter element in a tunable filter. Alternatively the negative resistance of the active element may be adjusted such that the resonator exhibits net negative resistance and may be incorporated in a tunable reflection type amplifier.

Abstract: A variable feedback and tuning capacitor, which is fabricated from a brac with bendable metallic prongs, is attached to the input transmission line of a microwave transistor amplifier. The prongs are placed in close proximity to the collector pad metalization of the carrier and provide a convenient and novel means for RF tuning the amplifier after the transistor is carrier mounted and DC tested.