Itt Corporation

David A Willems

Inder J Bahl

Kenneth S Karsten, Jr

Virender K Sadhir

Victor E Steel

Edward L Griffin

Michael D Pollman

There is disclosed a tunable notch filter which has a bandpass characteristic and where a tunable notch is added to the bandpass filter by placing a resonator outside the input or output probe of the bandpass filter. The bandpass filter is a resonant type of filter and comprises a plurality of parallel, spaced apart resonators. The tunable notch resonator is positioned near the input or output probe and operates to direct a substantial amount of energy from the filter at the frequency at which the notch resonator is tuned. In this manner a notch is created within the bandpass characteristic of the filter and which notch resonator can be tuned to provide the notch anywhere in the filter passband or above or below the band edges.

Tunable microwave filter apparatus having a notch resonator

An equalizer circuit for equalizing RF frequencies implemented as an MMIC or MIC having a series of microstrip transmission lines between an RF input terminal and an RF output terminal and having at least one shunt path comprised of a series combination of a FET able to be switched between a conducting state and a nonconducting state and a stud tuner microstrip transmission line, wherein the FET is used as a voltage variable resistor to selectively de-Q the stub tuner and thereby control the depth of the equalization curve. In a modified embodiment, artificial transmission lines which include a plurality of inductive elements and FETs are coupled to each shunt path, wherein the shunt paths may be selectively shorted by changing the state of the FETs, thereby permitting the center frequency of the equalizer circuit to be shifted as well.

Electronically tunable gain equalizer

A coupled line structure for microwave signals employs a gallium-arsenide substrate having an embedded metallic line located on a surface of the substrate. The surface of the substrate is covered with a thin dielectric layer and at least another metallic line is positioned on the dielectric layer and parallel to the embedded line with a portion of the lines overlapping one another for coupling. A third line can also be disposed on the dielectric layer which line is parallel to the other lines and where the embedded line is connected by a via hole to one of the lines on the dielectric.

Broadband tight coupled microstrip line structures

An FET crossbar switch device is implemented by using a split gate electrode and a shared source and drain pad to implement source and drain electrodes on an integrated circuit substrate. First and second inputs to the device are associated with first and second transmission lines, each of which is directly connected to a first and second source electrode areas. Disposed between the source electrode areas are respective drain electrode sections, each of which is coupled to an associated output transmission line. The input and output transmission lines are fabricated directly on the integrated circuit substrate. Gate fingers or electrodes are directed between respective drain electrodes and adjacent source electrodes. By properly biasing the gate electrodes, one can direct the first input to the first output with the second input directed to the second output. In a second state the first input can be connected to the second output with the second input disconnected or connected to the first output. In this manner, the device operates as a crossbar switch while providing extremely efficient operation at high microwave frequencies due to the symmetry of the device as employing transmission line geometry. The construction of the device reduces the need for matching networks. The entire device is implemented by microwave monolithic integrated circuit techniques and is extremely reliable and efficient.

FET crossbar switch device particularly useful for microwave applications

The present invention is an equalizer circuit for RF frequencies comprising a microstrip transmission line having a stub tuner extending transversely therefrom and further having resistive means coupled to the stub tuner to de-Q the stub tuner, thereby selectively determining an attenuation profile for the equalizer circuit.

Monolithic compatible, absorptive, amplitude shaping network

A broadside microstrip coupler employs a first transmission line which consists of a series of capacitor plates which alternate between a dielectric layer from a first location to a second location and each of the series of plates are connected together with a top plate on the top surface of the dielectric and a bottom plate located a given distance beneath the dielectric layer. A second transmission line alternates between the top and bottom layers of the dielectric and consists of a second series of plates where each capacitor is connected to an adjacent plate with the top plate of the first connecting to the bottom plate of the second and the bottom plate of the first connecting to the top plate of the second and so on. This pattern is repeated so that the conductive plate path alternates from the top to the bottom plate. The coupler allows for tight coupling between inputs and outputs and enables the even and odd mode phase velocity differences to be compensated for due to the fact that the odd mode travels between the two conductors and the even mode travels between the conductor and the ground plate.

Microstrip twisted broadside coupler apparatus

A broadband microstrip filter structure employs a first transmission line which basically consists of a series of capacitor plates which extend between a dielectric layer from a first location to a second location and each of the series of plates are connected together with a top plate on the top surface of the dielectric and a bottom plate located a given distance beneath the dielectric layer. A second transmission line alternates between the top and bottom layers of the dielectric and consists of a second series of capacitive plates whereby each capacitor is connected to an adjacent capacitor with the top plate of the first connecting to the bottom plate of the second and the bottom plate of the first connecting to the top plate of the second and so on. This pattern is repeated so that the conductor path alternates from the top to the bottom plate. Various capacitors are selected to provide predetermined length resonators while various other capacitors are provided to provide coupling sections. In this configuration each of the above-noted lines provide switching from the top to the bottom so that each conductor averages the same distance from the ground plane insuring identical impedances in each line. The structure allows tight coupling and enables the even and odd mode phase velocity differences to be compensated for due to the fact that the odd mode travels between the two conductors and the even mode travels between the conductor and the ground plane. In this manner the odd mode travels faster but further, thus the even mode and the odd mode move down the structure in synchronism.

Broadband microstrip filter apparatus having inteleaved resonator

A transmission line structure operates as a transformer and includes at least two intertwined serpentine planar transmission lines positioned on a substrate with the lines repeatedly crossing each other with said areas of crossing including an airbridge or other structure which physically isolates one line from the other.

Microstrip transformer apparatus

A reflection-type phase shifter employs an artificial delay line which is constructed of high impedance transmission line sections for the series inductive elements in the transmission line. Each junction between inductances in the transmission line is associated with a separate FET pair. The FET pair includes a first FET having the source to drain path coupled between the junction and a point of reference potential. The gate electrode of the first FET is coupled via the source to drain path of a second FET to the point of reference potential. The gate electrode of the second FET is coupled to one terminal of a resistor which is of a larger value compared to the ON resistance of the FET. This resistor has another terminal coupled to a control voltage source. Each junction or tap between inductors is returned to ground through an additional circuit where the gate electrode of the second FET in each circuit is coupled to that resistor which is also coupled to the gate electrode of each first FET in the FET pair. In this manner, when a given FET is selected and biased ON to implement a given length line, each FET device which is further down the chain is also operated, based on the cascade arrangement of FETs. In circuit operation, each FET which is further down the chain automatically conducts due to the difference in the ON resistance of the FET as compared to the value of the above-noted resistor. The circuit eliminates the need for complex digital control by automatically switching all the FETs ON between the FET selected and the shorted end of the transmission line.

Switched transmission line phase shifter apparatus employing multiple

A high efficiency harmonic injection power amplifier has a power amplifier circuit, and at least a second-harmonic termination circuit which is coupled in parallel with the power amplifier circuit so to sample a small portion of the input signal and to inject into the power output signal an amplified harmonic signal which is phase-shifted for proper harmonic termination. The second-harmonic termination circuit includes a frequency multiplier for multiplying the frequency of the sampled input signal to twice the fundamental frequency, i.e., to 2f.sub.o, an amplifier for amplifying the 2f.sub.o signal to the level of the corresponding harmonic component of the power amplifier output signal, and a phase shifter for shifting the phase of the second-harmonic signal for proper harmonic termination. Additional harmonic termination circuits may be provided for terminating third- and higher-order harmonics.

High efficiency harmonic injection power amplifier

An active-type broadband power divider has a pair of distributed amplifiers which are coupled together by a distributed capacitive coupling to provide a predetermined phase shift between respective output signals thereof. The distributed amplifiers are in the form of a row of three-terminal transistors having their gates and drains connected to gate and drain lines. The gate and drain lines are artificial transmission lines. By distributing the capacitive coupling between the gate and/or drain lines, a constant 90 degree phase shift is obtained over the entire bandwidth of the artificial transmission lines. For a 180 degree phase shift, a third distributed amplifier is provided with distributed capacitive coupling between its gate or drain line and that of the second distributed amplifier.

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Salem, VA, United States of America

David A Willems