Matched Filter Detector

 

  
Figure 4.8: Matched Filter Detector Control Window

The Matched filter detector as developed in section 3.1.1 and depicted in figure 3.1 is controlled by this control window. The matched filter is the least complex of the fixed detectors, but requires the exact timing of the users, the spreading codes and power. The detector was implemented in the m-file, cdma_matched_filt.m, where input to the file includes the spreading waveforms, power, and timing. The control windows for the fixed detectors are very similar, and all provide the same performance measures.

• Desired user to be demodulated. When new data is generated, this pulldown menu is updated to include or remove new or old users.
• Desired delay of the desired user. For the matched filter detector, there is only one delay.
• Perform demodulation using the matched filter of the desired user. Automatically plots the Squared Error in the Squared Output Error Figure.
• Color of trace plotted on the Squared Output Error Figure after simulation.
• The achieved Bit Error Rate calculated from the last 1000 symbols.
• The achieved mean squared error in dB calculated from the last 1000 symbols simulated.
• Outputs a figure similar to figure 4.10 with the following plots
  • Convolution of the desired user's spreading code and channel impulse response.
  • The impulse response of the equalizer
  • The combined system impulse response
  • The combined system frequency response
• Plots the eye diagram and constellation diagram of the last 500 transmitted symbols.
• This figure is accessed by all of the fixed and adaptive receivers to plot the squared output error after the simulation is run. (Squared Output Error ) The traces and legend are cleared by the Clear Traces control button on the main control window, see section 4.3.1. The figure also displays, in a dashed line, the minimum MSE achieved by the MMSE receiver for the given user and delay. See figure 4.9.
    
  Figure 4.9: Squared Output Error Figure generated when any of the fixed or adaptive receivers are simulated. The traces are cleared from the main window.
  
    
    
  Figure 4.10: (a) 1. combined channel and spreading code 2. Equalizer Impulse Response 3. Overall system impulse response 4. Overall system frequency response. This plot is generated from any of the adaptive or fixed detector control windows (b) Constellation and Eye Diagram. This plot is generated from any of the adaptive or fixed detector control windows.