Described are an amplifier circuits, systems, and methods for amplifying a plurality of sinusoid signals having a relative phase difference to each other. The amplifier circuit comprises a first sequence of at least three transistor amplifiers, wherein a first terminal of each transistor amplifier of the first sequence is configured to receive one respective signal of the plurality sinusoid signals. The amplifier further comprises a second sequence of at least three transistor amplifiers. A second terminal of each transistor amplifier of the second sequence is connected to a third terminal of one respective transistor amplifier of the first sequence. A first terminal of each transistor amplifier of the second sequence is connected to the third terminal of a next transistor amplifier of the second sequence. The first terminal of a last transistor amplifier is connected to the third terminal of a first transistor amplifier.

A frequency multiplier includes an input section having inputs to receive an input signal having an input frequency, a mixer section, and an output section magnetically coupled to the input section and generating an output signal in response to the input signal. The mixer section may be coupled to the input section by a common mode node forming a path for a common mode current to flow to the mixer section and be magnetically coupled to the common mode node. The input section may generate a signal current, and the mixer section may be magnetically coupled to the input section and be directly capacitively coupled to the input section through a capacitor in a signal current path. The mixer section may have differential inputs capacitively coupled to the input section and also be coupled to the input section through a current path. A current helper section may be coupled to the current path.

According to one embodiment, a transceiver includes: a radio transmitter including a power amplifier; a detector circuit including: a squaring circuit configured to receive an output of the power amplifier of the radio transmitter and configured to produce an output current; and a DC current absorber electrically connected to an output terminal of the squaring circuit.

Local oscillator (LO) leakage and Image are common and undesirable effects in typical transmitters. Typically, fairly complex hardware and algorithms are used to calibrate and reduce these impairments. A single transistor that draws essentially no dc current and occupies a very small area detects the LO leakage and Image signals. The single transistor operating as a square-law device is used to mix the signals at the input and output ports of a power amplifier. The mixed signal generated by the single transistor enables the simultaneous calibration of the LO leakage and Image Rejection.

Systems and methods for power conversion are described. Symmetric topologies and modulation schemes are described that may reduce common-mode noise. For example, a system may include a transformer including a first secondary winding and a second secondary winding; a rectifier, including a set of switches, that connects taps of the first secondary winding and the second secondary winding to a first terminal and a second terminal, wherein the rectifier is symmetric with respect to the first secondary winding and the second secondary winding; a battery connected between the first terminal and the second terminal; and a processing apparatus that is configured to control the set of switches to rectify a multilevel voltage signal on the transformer, including: selecting a modulation scheme from among two or more modulation schemes based on a measured voltage level of the battery.

Multi-input downconversion mixers, systems, and methods are provided with input switching in the intermediate frequency or baseband domain. One illustrative mixer embodiment includes: multiple differential pairs of transistors and multiple pairs of switches. Each differential transistor pair has their bases or gates driven by a differential reference signal, their emitters or sources connected to a common node having a current or voltage driven based on a respective one of multiple receive signals, and their collectors or drains providing a product of the differential reference signal with the respective one of the multiple receive signals. Each of the switch pairs selectively couples differential output nodes to the collectors or drains of a respective one of the multiple differential pairs, enabling the differential output nodes to convey an output signal that is a sum of products from selected ones of the multiple differential pairs.

An active mixer for frequency conversion used in a wireless communication system improves conversion gain and noise figure by improving switching characteristics of a mixer using a LO signal without requiring additional power consumption of an active mixer block. Further disclosed is a method for improving conversion gain and noise figure of an active mixer. The active mixer includes a switching stage for receiving a LO signal and selectively performing a switching-on/off operation for frequency conversion, a body signal generator for generating a body signal to be applied to a body of an NMOS transistor of the switching stage based on the LO signal, and a voltage controller for controlling the body signal generator to selectively apply the body signal to the body of the NMOS transistor based on to the switching-on/off operation of the switching stage to control a threshold voltage of the transistor of the switching stage.

Multi-input downconversion mixers, systems, and methods are provided with input switching in the intermediate frequency or baseband domain. One illustrative mixer embodiment includes: multiple differential pairs of transistors and multiple pairs of switches. Each differential transistor pair has their bases or gates driven by a differential reference signal, their emitters or sources connected to a common node having a current or voltage driven based on a respective one of multiple receive signals, and their collectors or drains providing a product of the differential reference signal with the respective one of the multiple receive signals. Each of the switch pairs selectively couples differential output nodes to the collectors or drains of a respective one of the multiple differential pairs, enabling the differential output nodes to convey an output signal that is a sum of products from selected ones of the multiple differential pairs.

A low power transmitter includes a low frequency feedback loop, a high frequency switching element embedded within the low frequency feedback loop, and a mixer electrically communicating with the low frequency feedback loop and the high frequency switching element. The low frequency feedback loop employs either a voltage mode interface or a current mode interface. The high frequency switching element includes a first transistor, a second transistor, and a pair of inductive elements. Alternatively, the high frequency switching element includes a single transistor and a single inductive element.

A frequency multiplier includes an input section to receive a quadrature phase input signal having an input frequency, a mixer section coupled to the input section by a common mode node that forms a path for the common mode signal current to flow to the mixer section and magnetically coupled to the common mode node or capacitively coupled to the input section to generate a differential switching voltage at odd multiples of twice the input frequency, which switching voltage is applied to inputs of the mixer section, and an output section magnetically coupled to the mixer section, the output section being configured to generate an output voltage having a dominate frequency and sub-dominate frequencies spaced apart by the first multiple, the dominate frequency of the output voltage being a second multiple of the input frequency, where the second multiple is greater than the first multiple. Various arrangements are provided.