Abstract: A ridge-waveguide filter with a signal input port at a first end and a signal output port at a second end contains a cascade assembly of metal-bounded ridge-waveguide sections with interspersed metal-bounded evanescent-mode coupling regions, and also contains low-loss ridge-waveguide port coupling networks to impedance-match the ends of the assembly to respective signal-port reference impedances. A frequency multiplexer with a composite-signal port and a plurality of channeled-signal ports is composed of a plurality of ridge-waveguide filters that are series-connected through a ridge-waveguide manifold containing a multiplicity of three-way waveguide junctions and quasi-lumped waveguide elements.

Abstract: A ridge-waveguide filter with a signal input port at a first end and a signal output port at a second end contains a cascade assembly of metal-bounded ridge-waveguide sections with interspersed metal-bounded evanescent-mode coupling regions, and also contains low-loss ridge-waveguide port coupling networks to impedance-match the ends of the assembly to respective signal-port reference impedances. A frequency multiplexer with a composite-signal port and a plurality of channeled-signal ports is composed of a plurality of ridge-waveguide filters that are series-connected through a ridge-waveguide manifold containing a multiplicity of three-way waveguide junctions and quasi-lumped waveguide elements.

Abstract: A method of fabricating a waveguide filter includes forming a monolithic polymeric dielectric core configured for fabricating a dielectric-filled cavity, where the core includes a plurality of spaced-apart depressions; applying a layer of conducting metal to an outer surface of the core to form a metallized core with a conductive metal layer, wherein the metal layer includes port openings at opposite ends of the metallized core, and wherein metallized depressions thereby formed are the ridges of the filter's ridge-waveguide sections; and mounting the metallized core on a supporting carrier. A desired number of such filters can be connected with an electrical-series-type connection among one port of each filter to form a frequency multiplexer having a waveguide manifold.

Abstract: A waveguide filter with a signal input port at a first end and a signal output port at a second end includes a dielectric core of moldable material where the outer surface of its periphery has a metal layer with nonmetallized openings positioned at opposite ends of the filter to accommodate the input and output ports. The filter's periphery is configured to provide a cascade connection of a plurality of metal-bounded ridge-waveguide sections with interspersed metal-bounded evanescent-mode coupling regions. The filter can be joined through a manifold to realize a frequency-multiplexer, with the manifold containing a cascade connection of electrically short waveguide segments and quasi-lumped waveguide circuit components, such as irises. The filter and multiplexer are amenable to the application of cost-effective injection molding techniques to manufacture the dielectric core.

Abstract: A method of fabricating a waveguide filter includes forming a monolithic polymeric dielectric core configured for fabricating a dielectric-filled cavity, where the core includes a plurality of spaced-apart depressions; applying a layer of conducting metal to an outer surface of the core to form a metallized core with a conductive metal layer, wherein the metal layer includes port openings at opposite ends of the metallized core, and wherein metallized depressions thereby formed are the ridges of the filter's ridge-waveguide sections; and mounting the metallized core on a supporting carrier. A desired number of such filters can be connected with an electrical-series-type connection among one port of each filter to form a frequency multiplexer having a waveguide manifold.

Abstract: A waveguide filter with a signal input port at a first end and a signal output port at a second end includes a dielectric core of moldable material where the outer surface of its periphery has a metal layer with nonmetallized openings positioned at opposite ends of the filter to accommodate the input and output ports. The filter's periphery is configured to provide a cascade connection of a plurality of metal-bounded ridge-waveguide sections with interspersed metal-bounded evanescent-mode coupling regions. The filter can be joined through a manifold to realize a frequency-multiplexer, with the manifold containing a cascade connection of electrically short waveguide segments and quasi-lumped waveguide circuit components, such as irises. The filter and multiplexer are amenable to the application of cost-effective injection molding techniques to manufacture the dielectric core.

Abstract: A new type of frequency-tunable active notch filter achieves frequency selectivity through interaction among input derived signal components that are passed through parallel signal channels in a forward-only direction. The notch filter differs from earlier channelized notch filters by using multiple, instead of just one, bandpass channels that maintain required forward signal flow in the main, passband-determining signal path without signal distortion at passband frequencies. The new approach has been experimentally verified with a hybrid-integrated three-channel filter whose 40-dB-deep band-reject notch can be continuously tuned, with the help of voltage-controlled variable-capacitance elements, from 9.5 to 10.5 GHz. A single-pole bandpass filter tunes in frequency with the help of only one variable capacitance element, yet still maintains constant passband width across the tuning span.

Abstract: A new type of frequency-tunable active notch filter achieves frequency selectivity through interaction among input derived signal components that are passed through parallel signal channels in a forward-only direction. The notch filter differs from earlier channelized notch filters by using multiple, instead of just one, bandpass channels that maintain required forward signal flow in the main, passband-determining signal path without signal distortion at passband frequencies. The new approach has been experimentally verified with a hybrid-integrated three-channel filter whose 40-dB-deep band-reject notch can be continuously tuned, with the help of voltage-controlled variable-capacitance elements, from 9.5 to 10.5 GHz.

Abstract: A channelized active bandpass filter having only two branches which provide respective frequency-selective feed-forward signal paths. The two signal aths have overlapping frequency response bands such that the combination of the two paths provides a composite filter with a bandpass response. The two branches may be provided with bandpass transfer characteristics of different orders and shapes, such as a second-order response and a fourth-order response. Two-way signal splitting and combining to define the two channels may be performed with in-phase splitters and combiners, for example, or diplexer circuits, each composed of two bandpass filters with different characteristics but overlapping frequency responses and preferably approximately equal center frequencies. Combinations of the two splitting and combining arrangements are also usable.

Abstract: A channelized protection circuit for protecting the front-end of a receiver rom the detrimental effects of interference signals within the bandwidth of received signals is disclosed.

Abstract: A multiplexer includes a first channel segment having first components derived from a first logarithmic-periodic multiplexer circuit. The first channel segment receives a composite signal from a composite-signal port, selects a first channel having a first bandwidth and first center frequency from the composite signal, and directs a first channelized signal to the first channelized-signal port responsive to the first channel. In addition, the multiplexer incenses a second channel segment, connected to the first channel segment and having second components derived from a second logarithmic-periodic multiplexer circuit. The second channel segment receives the portions of the composite signal from the composite-signal port via the first segment, selects a second channel having a second bandwidth and second center frequency from the composite signal, and directs a second channelized signal to a second channelized-signal port responsive to the second channel.

Abstract: A limited-bandwidth microwave transversal or recursive filter, compatible with microwave monolithic integrated circuit (MMIC) design requirements is described in this invention. The device comprises a means to split an incident signal into multiple parts for distribution among a plurality of input ports of frequency-selective feedforward and feedback network branches comprising filter elements and active devices so designed as to provide a desired degree and type of signal filtration. After filtration, the resulting signals from these branches are combined to form a composite filter output signal.

Abstract: A multiport microwave multiplexer having components which are log-periodically scaled structures is shown and described. Circuit parameter values and characteristic frequencies are determined and a first output port is linked by a constant ratio to corresponding quantities that define the response of other networks. A capacitively end-coupled channelizer filter is used for each channel of the multiplexer.

Abstract: A photoconductive reflectometer for characterizing semiconductor devices at millimeter wavelength frequencies where a first photoconductive circuit element (PCE) is biased by a direct current voltage source and produces short electrical pulses when excited into conductance by short first laser light pulses. The electrical pulses are electronically conditioned to improve the frequency related amplitude characteristics of the pulses which thereafter propagate along a transmission line to a device under test. Second PCEs are connected along the transmission line to sample the signals on the transmission line when excited into conductance by short second laser light pulses, spaced apart in time a variable period from the first laser light pulses. Electronic filters connected to each of the second PCEs act as low-pass filters and remove parasitic interference from the sampled signals and output the sampled signals in the form of slowed-motion images of the signals on the transmission line.

Abstract: A pulse generator for characterizing semiconductor devices at millimeter wavelength frequencies where a photoconductive circuit element (PCE) is biased by a direct current voltage source and produces short electrical pulses when excited into conductance by short laser light pulses. The electrical pulses are electronically conditioned to improve the frequency related amplitude characteristics of the pulses which thereafter propagate along a transmission line to a device under test.

Abstract: A field-effect transistor performs four functions, namely signal demodulation, generation of a local oscillator signal, generation of harmonics of this local oscillator signal through frequency multiplication, and mixing of the demodulated signal with either the local oscillator signal or one of its harmonics to produce a signal at a lower intermediate frequency; the field-effect transistor being the key element in a demodulator-downconversion circuit.

Abstract: A broadband high frequency power oscillator employing a GaAs FET transistor and a two-port coupling network whose input port is connected across the drain and source terminals of the GaAs FET. The coupling network consists of 3 branches in T- or .pi.-configuration. One branch includes a matching network and the load. The other two branches are purely reactive and each includes at least one independently tunable reactance element, such as a varactor.

Abstract: A broadband microwave recursive filter that provides sharp transitions in the frequency domain between adjacent stop and passbands comprising a signal input node; a signal output node; a filter circuit connected between the signal input node and the signal output node for providing a signal flow therebetween which has a predetermined frequency bandwidth characteristic; a microwave transistor circuit, with the microwave transistor circuit being band-limited to provide gain in only a restricted window of frequencies within the predetermined frequency bandwidth and connected for providing amplification to signals flowing in the filter circuit between the signal input node and the signal output node while suppressing out-of-window signals resulting from design approximations.

Abstract: A microwave frequency divider circuit. The frequency divider comprises a nonlinear amplifier including input and output ports for amplifying signals applied to the input port. The amplifier exhibits a nonlinear transconductance characteristic between its input and output ports. The amplifier input port is adaptable to receive a first signal having a frequency f.sub.l. The frequency divider further includes a feedback network coupled between the amplifier output and input ports to couple a second signal having a frequency f.sub.o appearing at the amplifier output port back to the input port. The first and second signals combine at the amplifier input port to modulate the nonlinear transconductance of the amplifier such that said first and second signals are mixed together and amplified. The circuit regeneratively oscillates such that the frequency f.sub.o equals a frequency f.sub.l /2. The frequency f.sub.l of the first signal is thus divided by the circuit.

Abstract: A microwave transistor oscillator/doubler comprising a Field-Effect Transistor with Terminals G, D and S in combination with a coupling network connected to the terminals G, D and S and composed of microstrip lines with lengths equal to a quarter wavelength at the second harmonic of a fundamental frequency. The doubler further comprises a bias circuit for supplying appropriate voltages to the FET terminals, and an impedance coupler for coupling from the FET D-S terminals to a waveguide load. The coupling network optimizes feedback at the second harmonic between the D-S and G-S ports of the FET to prevent destructive harmonic feedback interaction with the desired signal while providing optimum conditions for feedback at the fundamental frequency. The bias circuit is connected to the coupling network and includes a second network of transmission line elements of lengths equal to a quarter wavelength at the fundamental in order to prevent dissipation of the fundamental frequency therein.