Receiver of radio frequency signals

Abstract

There is described a receiver of at least one radiofrequency modulated signal deriving from an antenna external to the receiver; the receiver comprises a first stage for the low noise amplification of the radiofrequency modulated signal and a demodulation stage of the above-mentioned signal. The receiver comprises a SAW filter adapted to act as a pass band filter about a predetermined frequency for the signal deriving from the first stage, a logarithmic amplifier adapted to amplify the signal deriving from the SAW filter, a peak detector of the output signal of the logarithmic amplifier, means adapted to control the gain of the first stage for the amplification of the radiofrequency modulated signal as a function of the output signal (Vopeak) of the peak detector.

The invention claimed is: 
     
       1. A receiver of at least one radiofrequency modulated signal deriving from an antenna external to the receiver, said receiver comprising a first stage for the low noise amplification of the radiofrequency modulated signal and a demodulation stage of the radiofrequency modulated signal, characterized by comprising a SAW filter adapted to act as a pass band filter about a predetermined frequency for the signal deriving from the first stage, a logarithmic amplifier adapted to amplify the signal deriving from the SAW filter, a peak detector of the output signal of the logarithmic amplifier, means to control the gain of the first stage for the adapted amplification of the radiofrequency modulated signal as a function of the output signal (Vopeak) of the peak detector, said output signal (Vodet) of the logarithmic amplifier and said output signal (Vopeak) of the peak detector being in input to the demodulation stage. 
     
     
       2. The receiver according to  claim 1 , wherein said means are adapted to reduce the gain of the first stage of the amplification of the radiofrequency modulated signal in correspondence of a value increase of the output signal of the peak detector, said means being adapted to increase the gain of the first stage of amplification of the radiofrequency modulated signal in correspondence of a value reduction of the output signal of the peak detector. 
     
     
       3. A The receiver according to  claim 1 , wherein said means comprise a first common emitter bipolar transistor the base terminal of which is controlled by the output signal (Vopeak) of the peak detector, said first amplification stage comprising a second common emitter bipolar transistor, the current flowing through the base terminal of said second bipolar transistor depending on the current flowing through the collector terminal of the first bipolar transistor. 
     
     
       4. The receiver according to  claim 1 , wherein said peak detector comprises at least one capacitor the value of which determines the decay constant of the output signal of the peak detector. 
     
     
       5. The receiver according to  claim 4 , wherein said peak detector comprises a operational amplifier having the output signal of the logarithmic amplifier at the non-inverting input terminal, the output terminal connected with the anode of a diode having the cathode connected with the inverting input terminal of the operational amplifier and with one terminal of a resistance having the other terminal connected with one terminal of said capacitor having the other terminal connected to a reference voltage. 
     
     
       6. The receiver according to  claim 1 , wherein said demodulator comprises means adapted to average the output signal of the logarithmic amplifier, said means comprising at least a further capacitor. 
     
     
       7. An LTCC package comprising the receiver as defined in  claim 1  which is manufactured in a ceramic material substrate and wherein the at least one capacitor and at least a further capacitor are external to the package. 
     
     
       8. The LTCC package according to  claim 7 , wherein by comprising a microcontroller manufactured in said ceramic material substrate, said receiver being adapted to interact with said microcontroller.