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Complementary Code Keying

Complementary Code Keying. with PIC based microcontrollers for The Wireless Radio Communications. Common problems with digital Radio Communications. Interference from other radio communication devices Direct Sequence Spread Spectrum (DSSS) solve this problem

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Complementary Code Keying

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  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 • Transmitter’s part of the CCK transceiver is a low cost effective, but the receiver’s part is more complex • The CCK waveform has better Eb/N0 performance than DPSK • DSSS with use of Barker’s code is more stable according to the longrange and distance between transmitter and receiver in comparison with CCK

  10. Thank you!

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