An in-phase/quadrature (I/Q) clock generator is described. The I/Q clock generated includes a poly-phase filter configured to generate a four-phase quadrature clock signal in response to a two-phase quadrature clock signal generated in response to a single-ended input clock signal. The I/Q clock generated also includes a phase interpolator configured to generate an output four-phase quadrature clock signal from the four-phase quadrature clock signal. The I/Q clock generated further includes a poly-phase filter tune circuit coupled to an output of the phase interpolator. The poly-phase filter tune circuit is configured to generate a control voltage for the poly-phase filter to tune the four-phase quadrature clock signal from the poly-phase filter.

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.

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.

A first input terminal is connected to a point of connection of a drain terminal of a first transistor and a gate terminal of a fourth transistor. A second input terminal is connected to a point of connection of a drain terminal of a third transistor and a gate terminal of a second transistor. One of first through fourth output terminals to is connected to a source terminal of each of the first through fourth transistors to. A gate terminal of the first transistor and a drain terminal of the second transistor are connected, and a gate terminal of the third transistor and a drain terminal of the fourth transistor are connected.

A first input terminal is connected to a point of connection of a drain terminal of a first transistor and a gate terminal of a fourth transistor. A second input terminal is connected to a point of connection of a drain terminal of a third transistor and a gate terminal of a second transistor. One of first through fourth output terminals to is connected to a source terminal of each of the first through fourth transistors to. A gate terminal of the first transistor and a drain terminal of the second transistor are connected, and a gate terminal of the third transistor and a drain terminal of the fourth transistor are connected.

A phase shifter capable of improving phase accuracy by a simple method is provided. The phase shifter includes a hybrid coupler circuit including inductors with mutual inductances, an amplifying circuit, an impedance matching circuit provided between the hybrid coupler circuit and the amplifying circuit. The impedance matching circuit includes a first resistance element connected to an output node of the hybrid coupler circuit, a capacitance element connected between the first resistance element and the ground line in series, another inductor connected in parallel with the first resistance element, and a second resistance element provided between the inductor and the ground line in series.

A phase shifter capable of improving phase accuracy by a simple method is provided. The phase shifter includes a hybrid coupler circuit including inductors with mutual inductances, an amplifying circuit, an impedance matching circuit provided between the hybrid coupler circuit and the amplifying circuit. The impedance matching circuit includes a first resistance element connected to an output node of the hybrid coupler circuit, a capacitance element connected between the first resistance element and the ground line in series, another inductor connected in parallel with the first resistance element, and a second resistance element provided between the inductor and the ground line in series.

A first resistor to a fourth resistor and a first capacitor to a fourth capacitor are connected together in series in a ring shape. A first output terminal to a fourth output terminal are connected to series connection points between the first resistor to the fourth resistor and the first capacitor to the fourth capacitor, a first input terminal is connected to a series connection point between the fourth capacitor and the first resistor, and a second input terminal is connected to a series connection point between the second capacitor and the third resistor. Furthermore, a fifth resistor is connected between a series connection point between the first capacitor and the second resistor and a series connection point between the third capacitor and the fourth resistor.

Apparatus and methods for quadrature combined Doherty amplifiers are provided herein. In certain embodiments, a separator is used to separate a radio frequency (RF) input signal into a plurality of input signal components that are amplified by a pair of Doherty amplifiers operating in quadrature. Additionally, a combiner is used to combine a plurality of output signal components generated by the pair of Doherty amplifiers, thereby generating an RF output signal exhibiting quadrature balancing.

Apparatus and methods for vector modulator phase shifters are provided. In certain embodiments, a phase shifter includes a quadrature filter that filters a differential input signal to generate a differential in-phase (I) voltage and a differential quadrature-phase (Q) voltage, an in-phase variable gain amplifier (I-VGA) that amplifies the differential I voltage to generate a differential I current, a quadrature-phase variable gain amplifier (Q-VGA) that amplifies the differential Q voltage to generate a differential Q current, and a current mode combiner that combines the differential I voltage and the differential Q voltage to generate a differential output signal. A phase difference between the differential output signal and the differential input signal is controlled by gain settings of the I-VGA and the Q-VGA.