SDARS INTEGRATED
FRONT-END RECEIVER

Functional Description




Project: The SDARS Integrated Front-End Receiver

Group Members: Kara Bendix, Carlos Anaya, and Nitin Malhotra

Project Advisor: Dr. Prasad Shastry

Date: October 6, 2002


This senior capstone project involves the design, fabrication, testing, and measurements of an integrated front-end receiver for the SDARS (Satellite Digital Audio Radio Service). The goal of this project is to receive the SDARS signal utilizing multiple components, and convert it to an intermediate frequency, and test the receiver using the tuner now available in the market.

Figure 1 [1] shows the process of the digital radio signal transmission. The signal originates at the radio studios from where it is transmitted to the three Sirius satellites that will then broadcast to earth. Ground repeaters are also implemented to transmit the signal and make possible a clear sound even through tunnels and potential attenuating factors such as buildings. A receiver picks up the best input of the broadcasted signals and reproduces the high quality audio contained in the signal from the satellites.




Figure 1 Satellite Digital Audio Radio Signal System Functionality


The front-end receiver consists of a circularly polarized antenna, a low-noise amplifier and a down-converter. This project involves the design, test, fabrication and measurements of these components individually as well as the integrated module consisting of these components.

Figure 2 shows a block diagram of the SDARS system. The circularly polarized antenna will capture the satellite digital audio-radio signal. A low-noise amplifier amplifies this signal adding very little noise of their own. This signal is then fed to a down converter. The down converter consists of a mixer driven by a local oscillator. Then, signal passes through the mixer where it is converted to a lower frequency. Then, the intermediate frequency signal is filtered and amplified. The Sirius Radio satellite Digital Audio Signal has a transmitting bandwidth from 2.320 GHz to 2.3325GHz. Sirius Radio has 100 channels within this bandwidth.




Figure 2 System Block Diagram


The input and output signals in Figure 2 are listed below.

    1. Input to the Antenna is the signal from the Sirius satellites
    2. Output signal from the Antenna (satellite signal)
    3. Input to the low noise amplifier
    4. Amplified satellite signal
    5. Input signal to the down converter that converts the signal to lower frequency for processing
    6. Amplified signal from down converter (lower frequency). Modulated intermediate frequency digital audio signal



[1] Figure 1 is from the Sirius website, www.sirius.com