Abstract: Systems and methods for measurement of signal power, when the signal is substantially variable or otherwise time varying. A log-linear VGA is coupled in a feedback configuration to a difference-of-squares detector and an integrator. The log-linear VGA includes a set of selectable amplifier cells. A sliding current generator selects one or more amplifier cells, wholly or partially, producing a sum of outputs. Some of the selectable amplifier cells have differential amplification, while others have similar amplification but are differentially attenuated. Switches turn off to isolate amplifier cells when the cell is not selected. Canceling circuits produce an output opposite to unselected amplifier cells, providing a sum near zero. Temperature compensation and other adjustment include two components: when the output y and the input x have the relation y=a+b log x the log-linear VGA can adjust either the offset or slope.

Abstract: A directional coupler has a first port, a second port, a third port, and a fourth port. A first inductor has a first connection to the first port and a second connection to the second port. A second inductor has a first connection to the third port and a second connection to the fourth port. A first compensation capacitor is connected to the first port and the third port. A second compensation capacitor is connected to the first port and the fourth port. The first inductor is inductively coupled to the second inductor by a predefined coupling factor, the third port is isolated from the first port by a predefined first isolation factor, and the fourth port is isolated from the first port by a predefined second isolation factor. An inductance of the second inductor is substantially greater than an inductance of the first inductor.

Abstract: A cascode amplifier circuit having substantial linearity, while maintaining other advantages of cascode amplifiers such as relatively high input-to-output isolation and relatively high gain. The cascode amplifier circuit also provides substantially matched impedance between input and output, at least within a selected frequency band, with the effect of providing a circuit that is well-suited for use in a communication system. The cascode amplifier circuit includes feedback loops, such as for example DC feedback loops and AC feedback loops, and bias optimization, with the effect of improving linearity, maintaining gain, minimizing return loss, and providing a relatively high dynamic range.