Gain compensating apparatus for use with amplifying portion in code division multiple access communication system

A gain compensating apparatus for use with a amplifying portion corresponding to direct sequence code division multiple access system for directly multiplying spread spectrum codes by transmission data, spreading the resultant data on the frequency axis, and multiplexing a plurality of transmission channels on the same frequency band, comprising:

• a spreading/combining portion for inputting a plurality of transmission data, multiplying the transmission data by different spread spectrum codes, spreading the transmission data, generating spread spectrum data, converting the spread spectrum data into modulation data on the base band, adding the modulation data of individual transmission channels, multiplexing the modulation data, generating a multiplexed signal, obtaining quantized amplitude data, cumulating the amplitude data for a predetermined time period, and obtaining transmission average value information;
• a D/A converting portion for inputting the amplitude data from said spreading/combining portion and converting the amplitude data into an analog base band signal;
• a modulating portion, having a local oscillating portion and a modulator, for inputting the base band signal as a first input signal and a carrier generated by the local oscillating portion as a second input signal and outputs a modulation signal;
• a variable ATT portion for inputting the modulation signal, controlling an attenuation amount corresponding to a control signal, and controlling the level of the transmission output signal;
• an amplifying portion for inputting the modulation signal of which the level of the transmission power has been controlled by said variable ATT portion and amplifying the modulation signal;
• an HYB (distributor) for branching the output signal of said amplifying portion, the output signal of said HYB being sent to the outside of the apparatus as a transmission output signal;
• a detecting portion for detecting the output signal of said HYB and outputting a detected signal as voltage information;
• an A/D converting portion for quantizing the detected signal and converting the detected signal into digital transmission power data;
• and
• a comparing/controlling portion for inputting the transmission average value information received from said spreading/combining portion as a first input signal and the transmission power data received from said A/D converting portion as a second input signal, cumulating the transmission power data for a predetermined time period, comparing the cumulated signal with the transmission average value information, outputting data for compensating the difference as the compared result, and generating the control signal for controlling said variable ATT portion.