Automatic gain control unit for a low power receiver or transceiver

摘要

The automatic gain control unit for a radiofrequency receiver includes a first current source for charging a storage capacitor by a first current, four comparators for comparing on the lower side an in-phase positive intermediate signal, an in-phase negative intermediate signal, a quarter-phase positive intermediate signal, a quarter-phase intermediate signal with a first reference threshold to a high amplitude level of the intermediate signals. Each comparator controls a MOS transistor connected in series between a second current source and the storage capacitor in order to discharge the storage capacitor when each transistor is in a conductive state. A bi-stable trigger element is connected to the storage capacitor and to provide an AGC signal depending on the voltage level on the storage capacitor for attenuating or not the gain of the low noise amplifier or of a mixer unit amplifier of the receiver.

主权项

1. An automatic gain control unit for a low power receiver or transceiver, said receiver or transceiver comprising:
at least one antenna for receiving radio frequency signals, at least one low noise amplifier for amplifying the signals received by the antenna, a local oscillator for supplying oscillating signals, at least one mixer unit for mixing the amplified incoming signals with the oscillating signals supplied by the local oscillator, in order to produce alternative intermediate signals, wherein the automatic gain control unit includes:
a first current source for charging or discharging by a first current at least one storage capacitor,at least one comparator for comparing at least a first alternative intermediate signal among the alternative intermediate signals and a first reference threshold, which is defined for a comparison with an upper side or a lower side of the first alternative intermediate signal to determine an amplitude level of the first alternative intermediate signal,a gate controlled transistor by an output of the comparator, the transistor being conductive when the first alternative intermediate signal is greater than the first reference threshold for a comparison on the upper side, or lower than the first reference threshold for a comparison on the lower side, the transistor being connected in series between a second current source and the storage capacitor in order to discharge or charge by a second current the storage capacitor inversely to the first current, the second current being supplied to the storage capacitor when the transistor is conductive, and the second current having a value greater than the first current, anda bi-stable trigger element connected to the storage capacitor and to provide an AGC signal depending on the voltage level on the storage capacitor for tuning the gain of the low noise amplifier or of a mixer unit amplifier.