Complementary Code Keying with PIC based microcontrollers for

Complementary Code Keying with PIC based microcontrollers for The Wireless Radio Communications

Common problems with digital Radio Communications 4 Interference from other radio communication devices • Direct Sequence Spread Spectrum (DSSS) solve this problem 4 Interference from multipath signals • Complementary Code Keying (CCK) solve this problem

CCK modulator CCK uses one of 64 nearly orthogonal vectors to generate spreading code word 4 Implementation is based on PIC 16 F 84 4

Code word generation 4 4 “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

QPSK modulator LEGEND: h h h h 1 & 2 - balanced mixers 3 - phase splitter 4 - carrier oscillator 5 - coupler 6 - band-pass filter 7 - power amplifier 8 - antenna 4 QPSK modulator allows transmitting of two independent channels (I and Q) at the same time

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

Circuit diagram of the CCK encoder

Block diagram of the program

Conclusions 4 Improve performance for general multipath environments in radio transmission 4 Transmitter’s part of the CCK transceiver is a low cost effective, but the receiver’s part is more complex 4 The CCK waveform has better Eb/N 0 performance than DPSK 4 DSSS with use of Barker’s code is more stable according to the long range and distance between transmitter and receiver in comparison with CCK

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