Complementary Code Keying

1
Complementary Code Keying

• with PIC based microcontrollers for
• The Wireless Radio Communications

2
Common problems with digital Radio Communications

• Interference from other radio communication
  devices
• Direct Sequence Spread Spectrum (DSSS) solve this
  problem
• Interference from multipath signals
• Complementary Code Keying (CCK) solve this problem

3
CCK modulator

• CCK uses one of 64 nearly orthogonal vectors to
  generate spreading code word
• Implementation is based on PIC16F84

4
Code word generation

• C is the code word with LSB first to MSB last
• CCK codeword has 4 phase terms. One of them
  modulates all of the chips (?1) and this is used
  for the QPSK rotation of the whole code vector.
  The 3 others modulate every odd chip (?2), every
  odd pair of chips (?3) and every odd quad of
  chips (?4) respectively

5
QPSK modulator

• LEGEND
• 1 2 - balanced mixers
• 3 - phase splitter
• 4 - carrier oscillator
• 5 - coupler
• 6 - band-pass filter
• 7 - power amplifier
• 8 - antenna

• QPSK modulator allows transmitting of two
  independent channels (I and Q) at the same time

6
Phase splitter

• Low cost design
• Constant phase difference among wide working
  frequency drift
• Better performance up to few hundred MHz
• For higher frequency (UHF bands) can be used
  micro strip lines with length equal to ? /4

7
Circuit diagram of the CCK encoder
8
Block diagram of the program
9
Conclusions

• Improve performance for general multipath
  environments in radio transmission
• Transmitters part of the CCK transceiver is a
  low cost effective, but the receivers part is
  more complex
• The CCK waveform has better Eb/N0 performance
  than DPSK
• DSSS with use of Barkers code is more stable
  according to the long range and distance between
  transmitter and receiver in comparison with CCK

10
Thank you!