Group SD0806
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Contents |
Weather Satellite Receiver and Display:
Group Members: Sheldon Aldridge, Brent Bachmeier, Joel Millage, and Jacob Lien.
Advisor: Dr. Roger Green.
Project Introduction:
Signals transmitted by the Polar Orbiting Environmental Satellites (POES) put up by the U.S. National Oceanic and Atmospheric Administration (NOAA) contain weather images we intend to collect with earth based receivers. The intent of this project is to build a receiver to capture and display the signal. The RF signal is first received through an antenna where it is amplified and filtered. Next, the signal is down converted into an intermediate frequency (IF). The signal then goes through a digital signal processor (DSP) which demodulates the signal. The demodulated signal is then processed to recover the Automatic Picture Transmission (APT) signal, and output to an attached display. Every time the satellite passes over the image is refreshed. Figure 1 illustrates the basic steps of this procedure.
Requirements:
Analog Front End:
• Put a jack on the PCB to receive antenna signal
• Build Quadrifilar Helix Antenna
• Use low-noise amplifiers and signal conditioning
• Down convert to an audio IF
• FM Demodulation done with IC
Digital Front End:
• A/D conversion at an audio sampling frequency
• AM Demodulation done on DSP
• Convert APT format to display format
Display Interface:
• Hook up to suitable graphics display
Optional Features:
• Save images
• Provide image loops
• Develop example labs for appropriate ECE 443 use
Image Extraction:
• We have successfully extracted an Image using a 15 min sample signal found online using Matlab
Schematis, PCBs, and Test Circuits:
Final Analog Front End Board:
Intermediate Frequency Demodulation Circuit:
LCD Graphics Controller Test Setup:
Old Test Boards:
DSP PCB Schematics and Layout:
Timeline and Roles:
Jacob Lien will be in charge of the analog signal reception part of the project. He will need to Research, Design and successfully implement the analog portion of the design. This includes receiving the signal with an antenna and getting it down to an intermediate frequency as well as FM demodulating the signal down to 2.4kHz. Joel Millage will be in charge of the Algorithms for this project. This will include doing AM demodulation on the signal after it has been reduced to an intermediate frequency as well as extracting the image out of the signal and displaying it on the LCD screen. Sheldon Aldridge will be in charge of the Hardware research, design and implementation. This will include designing the DSP board and additional hardware, such as an external display. Brent Bachmeier will be in charge of the DSP research, design and implementation. This will include receiving the image signal and converting so that it can be displayed on the external display. See below figure for preliminary start and end dates.
Quadrifilar Helix Antenna:
A common antenna used for receiving Weather Satellite Signals is the Quadrifilar Helix Antenna. They are relatively easy to build and they can receive the 137.5MHz Satellite signal rather easily. Below is a picture of the finished antenna that we built. We were able to successfully test and receive a signal using the antenna and we had approximately a 10dB signal to noise ratio on the reception.
DSP Software:
Attached below is the main portion of the code that I wrote. The Display.c and Display.h files are used for writing data to the display using GPIO on the 6713 DSK. The files are based of the LCD datasheet for LCD timing. The ISRs.c file handles the sampling from the audio codec at 48kHz and does the AM demodulation in real time as well as the image extraction portion. The sync.h file is generated in Matlab to be used in cross correlation with the signal to determine where the beginning of each line begins. Finally Main.c is our Main routine that is in a while loop forever that is driven by interrupts.
Assignments and Presentations:
