A high-selectivity low-loss duplexing system includes a first duplexer having a first port, a second port, a transmit port and a receive port. A second duplexer has a third port, a fourth port, an inverted transmit port and the receive port. The first port and the third port are connected to an antenna by a balun. The transmit port and the inverted transmit port are connected to at least one power amplifier. The receive port is connected to a low noise amplifier. A phase shifter includes a lattice filter configured to short the second port to the third port and the fourth port to the first port at a receive frequency, and short the second port to the first port and the fourth port to the third port at a transmit frequency.

A high-selectivity low-loss duplexing system includes a first duplexer having a first port, a second port, a transmit port and a receive port. A second duplexer has a third port, a fourth port, an inverted transmit port and the receive port. The first port and the third port are connected to an antenna by a balun. The transmit port and the inverted transmit port are connected to at least one power amplifier. The receive port is connected to a low noise amplifier. A phase shifter includes a lattice filter configured to short the second port to the third port and the fourth port to the first port at a receive frequency, and short the second port to the first port and the fourth port to the third port at a transmit frequency.

According to one embodiment, a transformer-based in-phase and quadrature (IQ) includes a differential balun having a first inductor and a second inductor. The first inductor has a first input terminal and a first output terminal. The second inductor has a second input terminal and a second output terminal. Additionally, the IQ generator circuit includes a third inductor magnetically coupled with the first inductor. The third inductor has a first isolation terminal and a third output terminal. The IQ generator circuit also includes a fourth inductor magnetically coupled with the second inductor. The fourth inductor has a second isolation terminal and a fourth output terminal. The IQ generator circuit additionally includes a first transistor coupled to the first input terminal of the first inductor. Further, the generator circuit includes a second transistor coupled to the second input terminal of the second inductor. The first transistor, the second transistor, the first inductor, and the second inductor form a part of a differential amplifier.

There are provided a transformer including inductors, and variable capacitors. Capacitance values of the variable capacitors are controlled by a control signal. One end of the first inductor is connected to a reference potential, the first variable capacitor is connected in series between the other end of the first inductor and a first terminal, the second variable capacitor is connected in series between one end of the second inductor and a second terminal, the third variable capacitor is connected in series between the other end of the second inductor and a third terminal. The capacitance values of the variable capacitors are changed by the control signal to obtain a desired pass phase, a loss is small, and both functions of a single-phase-differential conversion and a phase shifter are realized.

There are provided a transformer including inductors, and variable capacitors. Capacitance values of the variable capacitors are controlled by a control signal. One end of the first inductor is connected to a reference potential, the first variable capacitor is connected in series between the other end of the first inductor and a first terminal, the second variable capacitor is connected in series between one end of the second inductor and a second terminal, the third variable capacitor is connected in series between the other end of the second inductor and a third terminal. The capacitance values of the variable capacitors are changed by the control signal to obtain a desired pass phase, a loss is small, and both functions of a single-phase-differential conversion and a phase shifter are realized.

The isolated port of a 0/90 degree coupler is terminated by a novel complex termination impedance circuit having a reactance. The absolute value of the reactance is at least two ohms. The coupler receives a signal on its input port, and outputs a first signal on its first output port and a second signal on its second output port. A first load is coupled to the first output port without an intervening matching network. A substantial impedance mismatch exists between the first output port and the first load. A second load is coupled to the second output port without an intervening matching network. A substantial impedance mismatch exists between the second output port and the second load. Despite the substantial impedance mismatches, the first and second signals have a phase difference in a range of from 88 degrees to 92 degrees while exhibiting an amplitude imbalance less than 2 dB.

The isolated port of a 0/90 degree coupler is terminated by a novel complex termination impedance circuit having a reactance. The absolute value of the reactance is at least two ohms. The coupler receives a signal on its input port, and outputs a first signal on its first output port and a second signal on its second output port. A first load is coupled to the first output port without an intervening matching network. A substantial impedance mismatch exists between the first output port and the first load. A second load is coupled to the second output port without an intervening matching network. A substantial impedance mismatch exists between the second output port and the second load. Despite the substantial impedance mismatches, the first and second signals have a phase difference in a range of from 88 degrees to 92 degrees while exhibiting an amplitude imbalance less than 2 dB.

A circuit includes a RC-CR circuit and a second circuit. The RC-CR circuit outputs a first signal at a first output node over a RC path, and a second signal at a second output node over a CR path. The second circuit is coupled to the RC-CR circuit at the first output node over the RC path. The second circuit includes an array of capacitors coupled in parallel and a plurality of switches, and each of the array of capacitors is connected, in series, to a corresponding switch in the plurality of switches. Each of the array of capacitors and its corresponding switch are coupled between the first output node and a ground. The plurality of switches is switched on or off such that the first signal and the second signal have a phase difference that falls within a predetermined phase range.

Techniques for tuning a crossed-field antenna are provided. An example of an antenna system includes a D-plate with a D-plate feed conductor, such that the D-plate is a horizontal conductor raised above and insulated from a ground plane, an E-cylinder with an E-cylinder feed conductor, such that the E-cylinder is a vertical hollow conductive cylinder of smaller diameter than the D-plate, which is mounted concentrically above and insulated from the D-plate, a transmitter tuning circuit configured to receive a signal from a transmitter, an E-cylinder tuning circuit operably coupled to the transmitter tuning circuit and the E-cylinder feed conductor, and a D-plate tuning circuit operably coupled to the transmitter tuning circuit and the D-plate feed conductor.

Described herein are systems and methods that allow for correcting a residual frequency offset in the GHz frequency range by using low-complexity analog circuit implementations of a broad-band frequency detector that comprises two analog polyphase filters in a dual configuration. Each filter comprises an RC network of cross-coupled capacitors that facilitate filters with opposite passbands and opposite stop-bands. In various embodiments, the outputs of the two filters are combined to obtain power metrics that when subtracted from each other, deliver a measure of the imbalance between the positive and negative halves of a frequency spectrum. Since the measure is substantially proportional to a frequency offset within a linear range spanning 5 GHz or more, the polyphase filters may be used in a broad-band frequency detector that, based on the measure, adjusts the frequency offset.