Many modern communication systems include antennas with transmitter/receiver devices (
transceivers) for simultaneously transmitting and receiving independent radio frequency (RF) signals. Transceivers include a transmitter section and a receiver section. The transmitter includes a modulator to superimpose information, i.e., data, onto a suitable radio frequency (RF) carrier signal, such as a microwave frequency carrier signal. The receiver receives data carried by the carrier frequency signal and, in a heterodyning system, downconverts the received signal to a suitable intermediate frequency signal. A commonly used communication technique in RF wireless communications is spread spectrum. Spread spectrum modulation techniques are increasingly desirable for communications, navigation, radar and other applications. The transmitter in a spread spectrum communications system spreads the signal in accordance with the data to be transmitted. Each bit or set of bits to be transmitted is converted into a plurality of chips having a much wider bandwidth than the original data. The receiver despreads the spread spectrum signal in order to recover the original data signal. In direct sequence spread spectrum, the despreading of the signal is accomplished by correlating the received signal with a reference code matching the pseudo noise code used by the transmitter to transmit the information. In high frequency transceivers, the data being transmitted is baseband data which is modulated up to the carrier frequency in a two or three stage process.
