ELEC9725

Satellite Navigation: Systems, Signals and Receivers

Matlab Assignment No.2: Acquiring GPS Signals Objectives:

To use some of the techniques learnt in class to acquire GPS signals in the midst of noise. The aim is to use data recorded by an RF front end, received from a GNSS signal simulator.

Requirements:

The assignment has some basic requirements that cover the fundamentals of acquisition. The extra, “bonus” requirements are not required in order to pass the assignment, but will result in higher marks being awarded.

A satellite signal is supplied and is downloadable from {KeaIF_Dataset1.bin}

In this data file, there are several satellite signals buried in the noise in a ~1000ms set of data. Satellite 19 has the lowest Doppler, and should be able to be acquired without a Doppler search. The supplied Matlab file {ReadIFData.m} can be used to read the data from that file. It has embedded the key signal parameters: intermediate frequency and sampling frequency.

Minimum requirements:

• Run the Matlab file and explain the three figures produced

• Write your own Matlab routine to generate each of the 32 GPS satellite 1023-

chip codes. This can either be as [0, 1] (for checking) or [-1, +1] signals but

obviously [-1, +1] is required for the next sections.

• Create a sampled version of these signals at the required sampling frequency,

assuming that the codes are clocked at 1.023Mchip/s.

• Write a routine to use either time-domain or frequency-domain acquisition.

Remember the signal will still be hidden in the noise until it is passed through

a narrowband filter.

• Find satellite 19, and identify what its delay is.

Bonus requirements:

• Use the type of acquisition not used above (time or frequency) and repeat the task.

• Find as many satellites as you can

volts

S=1, M=1

S=1, M=0

S=0, M=0

S=0, M=1

   t

  Figure 1 How sign and magnitude bits are assigned

The program must be written up in a technical report. A typical report will be about 10 pages long.

Assessment:

Program: 50% of total mark. Clearly a fully operational program will attract more marks. Also well commented code will be rewarded.

Report: 50% of total mark. Guidelines for report writing and a report marking scheme are on the course website.

Of the final assessment of the course, this assignment is worth 20%. The approximate minimum investment of student time should be 6-10 hours (depending on level of mastery of MATLAB and GNSS study materials).

Penalties for late submission are described in the course outline.

Penalties for plagiarism will be severe. In other words, submissions with substantially similar reports or programs will be marked at a much lower level than they would otherwise.

Submission:

The submission is to be submitted via Moodle using the submission box under week 8. If that does not work, email to Prof Andrew Dempster (address: [email protected]) by 1700 Friday 5th April (week 8), and must be structured as follows:

1. The complete submission should include: (a) the report (in Word DOC format), (b) the Matlab m-file source code.

2. They should be compressed into one zip file (YourFullName_StudentNo_V#.zip) and be attached to the email, where V# is the version number of Matlab used. The Matlab version should also be specified in the report.

3. The subject of the email submission should be "Assignment No 1 YourFullName_StudentNo_V#", where V# is the version number of Matlab used.

4. There should be no text in the body of the email. If there is the need to explain the submission and it is not appropriate to be included in the report, put it in a file "Notes.txt" and add it to the zipped file.

5. By organising the submissions in this way, the assessment will be made solely based on the submitted zip file.

A. Dempster