Our Senior Project is to design and build an active integrated antenna to be used to receive an S.D.A.R.S.(Satellite Digital Audio Radio Service) signal.  This signal will be transmitted digitally via satellites and will be resistant to fading, allowing the user to receive the signal nationwide.  The satellites will transmit in the S-Band from 2.320GHz to 2.345GHz.  Terrestrial stations located throughout the U.S.A. near urban areas and major tunnels will supplement this signal so that reception will never be lost.  This technology will be available in January 2001, and will be provided by two competing companies that split the allocated bandwidth equally, resulting in 12.5MHz bandwidth for each company.
     Figure 1 shows how the digital radio will be transmitted.  First, the radio station will upload the signal to the satellites, which will then broadcast over the entire nation.  The receiver will acquire the transmission to be heard on a personal radio.  In urban areas and near major tunnels, terrestrial repeaters will receive the satellite signal and then transmit to areas with potentially poor reception.

     This project focuses on the front end of a personal receiver.  A passive antenna integrated with a low noise amplifier will be designed, fabricated, and interfaced to a mixer.  The block diagram for the project is shown below.  The input is the digital audio radio signal, which will be received by the passive antenna.  The RF signal will pass through a low noise amplifier used to enhance the sensitivity of the receiver.  This signal will then enter into a mixer, which is also receiving a lower frequency from the voltage controlled local oscillator.  These two frequencies are mixed together resulting in many carrier frequencies and their sidebands.  One of the resulting frequencies is RF freq – LO freq = Intermediate frequency (IF).  The IF signal is the same digital audio signal received from the satellite but at a lower frequency.  A band-pass filter is used to separate this signal from the many frequencies generated from the mixer.  The IF signal is amplified to output a strong digital audio radio signal ready for decoding.