Patent ID: 8170511

Claim:
An equalizer system for emitting a quasi-constant power output radio frequency (RF) signal in a first frequency band, the system comprising: a programmable RF signal generator configured to provide a modulated signal; a variable gain amplifier configured to receive the modulated signal and to generate an RF signal to a small capacitive antenna; a sensing devices configured to provide a sensing signal which is at least a one of a signal proportional with the RF signal and a signal proportional with a supply current of the variable gain amplifier; a user interface configured to determine an initial RF frequency signal; an adjusting circuit configured to provide a control signal to the variable gain amplifier based on the initial RF frequency signal and the sensing signal, the adjusting circuit comprising an arithmetic unit configured to calculate a value of the control signal; and a filter circuit configured to receive the RF signal and to provide a further RF signal to the antenna, the filter circuit comprising a first resonant circuit at a first resonant frequency inside the first frequency band and a second resonant circuit at a second resonant frequency outside the first frequency band to provide the RF signal having a substantial same power in the first frequency band; wherein the filter circuit comprises a first capacitor in series with a second capacitor in which the series combination is configured in parallel with an inductor that is parallel with the small capactive antenna, the inductor, the first capacitor and the capacitive antenna is configured to determine the second resonance frequency and the inductor, the first capacitor, the second capacitor and the capacitive antenna is configured to determine the first resonant frequency.