US 6,275,684 B1Granted

ALC circuit for a transmitter device

AssigneeNEC Corporation

InventorsTomoya Kaneko, Makoto Akaishi

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Abstract

An object of the present invention is to provide an ALC circuit for a transmitter device and its method which are capable of obtaining a detected voltage of sufficient and stable voltage over a wide high-frequency output power range. A signal extracted from a part of a transmission output signal by a directive coupler and a signal obtained by branching and amplifying a part of a local oscillation signal which is inputted to a first mixer for an up-convertor are inputted as a local oscillation signal of a second mixer. After the local oscillation signal has been down-converted into an intermediate frequency signal, it is inputted to a logarithmic amplifier through a band pass filter. The output signal of the logarithmic amplifier is extracted as a detected signal through a diode detector and amplified by a differential amplifier. The variable attenuator is controlled according to the amplified output to obtain a transmission output power.

Claims5

Dependent claims

An ALC circuit for a transmitter device having a frequency up-convertor of microwaves and millimeter waves, a variable attenuator and a power amplifier which comprises:

a first mixer that inputs an oscillation signal of a local oscillator;
a second mixer that inputs a part of the oscillation signal of said local oscillator and a part of a transmission output signal amplified up to a predetermined level by said power amplifier to output a down-converted intermediate frequency signal;
a logarithmic amplifier that amplifies the intermediate frequency signal outputted by said second mixer to a predetermined level;
a detector that obtains a level monitor voltage proportional to the logarithm of a signal level outputted by said logarithmic amplifier;
a differential amplifier that compares the output signal of said detector with a DC reference voltage that determines the transmission output power to amplify the comparison result;
and
said variable attenuator the quantity of attenuation is controlled according to the output of said differential amplifier.

4 more elements

Dependencies are inferred from the claim text.