Abstract: A digital frequency shift keying (FSK) transmitter provides direct frequency modulation in a wide bandwidth loop. In one embodiment, a discriminator circuit recovers from the output signal of the transmitter a base band signal, which is then compared with the input base band signal to provide an error signal for controlling the output oscillator circuit. In another embodiment, the output oscillator is controlled by a phase detector detecting the phase difference between the base band modulating signal and the output signal of the transmitter. An additional narrow bandwidth loop can be added to compensate for frequency drift in the output oscillator due to temperature or other environmental changes.

Abstract: An insertion filter is described for existing waveguide without modification. The filter includes a resilient bifurcated dielectric member (11) which conforms to the internal geometry of the waveguide (21). The dielectric member secures the position of a dielectric resonator (15) and a tuning screw (17) and retains their relative positions. A stud (18) is mounted on one of the bifurcations of the dielectric member to compensate electrically for the presence of the member in the waveguide while the dielectric resonator attenuates waveguide energy in a prescribed frequency band.

Abstract: A launching and/or receiving network is disclosed capable of coupling radio signals in a first frequency band, e.g., 2 GHz into and/or out of an existing antenna system without perturbing the signals being transmitted in other frequency bands, e.g., 4, 6 and/or 11 GHz. The first frequency band signal is launched through an evanescent mode waveguide filter which is both coupled to the flared sidewall of a feedhorn through an H-plane, T-junction, and provides a very broad stopband for the signals in the other frequency bands being launched in the feedhorn. To minimize mode conversion for the signals in the other frequency bands, a dummy evanescent mode waveguide filter is connected at one end thereof to the feedhorn facing the first frequency band launching network and at the other end thereof to a matched load through a waveguide section.

Abstract: A waveguide hybrid coupler having a pair of intersecting, rectangular, waveguides formed in a planar block of material. The coupling region at the intersection of such waveguides has two pairs of opposed corners wherein at least one pair of opposed corners projects into the coupling region.Additionally, a commutating hybrid is formed by connecting two such crossguide hybrid couplers with a pair of rectangular waveguide sections of unequal length. The commutating hybrids are then further connected in cascade to form a channel branching network which will combine and/or separate a plurality of frequency channels presented to the network.