US 10,840,868 B1Granted

Logarithmic RMS-detector with servo loop

AssigneeBeRex Corporation Co., Ltd

InventorsAbolfazl Khosrowbeygi, Farbod Behbahani

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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.

Claims15

Dependent claims

A signal power detector, including

a log-linear variable gain amplifier responsive to a control node, the variable gain amplifier including:
(A) a sliding current generator providing a set of current signals in response to the control node, (B) a first set of amplifiers each coupled to an independent output of the sliding current generator, wherein each one amplifier in the first set has decreased gain from a previous amplifier, (C) a second set of amplifiers each coupled to an independent output of the sliding current generator, wherein each one amplifier in the second set has the same gain as a previous amplifier, and has an attenuator coupled between input signal and the each one amplifier in the second set, and (D) a summing circuit coupled to outputs of both the first and second sets of amplifiers;
a detector coupled to an output of the log-linear variable gain amplifier, an output of the detector coupled to the control node of the log-linear variable gain amplifier, the detector computing a product of a difference and a sum of inputs of the detector;
wherein an output of the detector is responsive to a steady-state level of an input signal to the log-linear variable gain amplifier.

1 more element

A method of operating a signal power detector, including steps of

amplifying an input signal in response to a log-linear variable gain amplifier, the log-linear variable gain amplifier responsive to a control node;
wherein the steps of amplifying include steps of:
providing a set of current signals in response to a control node;
using a first set of amplifiers, each responsive to an independent one of the current signals, wherein each one amplifier in the first set has decreased gain from a previous amplifier;
using a second set of amplifiers each responsive to an independent one of the current signals, wherein each one amplifier in the second set has the same gain as a previous amplifier;
attenuating the input signal further for each one of the second set of amplifiers;
summing outputs from at least some of both the first and second sets of amplifiers;
providing an output of a detector of an output of the log-linear variable gain amplifier to the control node of the log-linear variable gain amplifier;
wherein an output of the detector is responsive to a steady-state level of an input signal to the log-linear variable gain amplifier.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 16/026,052Filed 3 Jul 2018
Granted: 17 Nov 2020
Term ends: Not estimatedThe source records don’t support an estimate.

Classification18 codes

H03G 3/30
Automatic control: in amplifiers having semiconductor devices
G01R 27/28
Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom: measuring attenuation, gain, phase…
H03F 1/0205
Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation: in transistor amplifiers
H03F 1/30
Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements: modifications of…