Complementary Code Complementary Code KeyingKeying

with PIC based microcontrollers forwith PIC based microcontrollers for

The Wireless Radio CommunicationsThe Wireless Radio Communications

Common problems with Common problems with digital Radio digital Radio CommunicationsCommunications

Interference from other radio Interference from other radio communication devicescommunication devices• Direct Sequence Spread Spectrum Direct Sequence Spread Spectrum

(DSSS) solve this problem(DSSS) solve this problem

Interference from multipath signalsInterference from multipath signals• Complementary Code Keying (CCK) Complementary Code Keying (CCK)

solve this problemsolve this problem

CCK modulatorCCK modulator

CCK uses one of 64 nearly orthogonal CCK uses one of 64 nearly orthogonal vectors to generate spreading code wordvectors to generate spreading code word

Implementation is based on PIC16F84Implementation is based on PIC16F84

Code word generationCode word generation

12131321414214314321 ,,,,,,, jjjjjjjj eeeeeeeec

““CC” is the code word with LSB first to MSB last” is the code word with LSB first to MSB last CCK codeword has 4 phase terms. One of them modulates CCK codeword has 4 phase terms. One of them modulates

all of the chips (all of the chips (11) and this is used for the QPSK rotation ) and this is used for the QPSK rotation of the whole code vector. The 3 others modulate every odd of the whole code vector. The 3 others modulate every odd chip (chip (22), every odd pair of chips (), every odd pair of chips (33) and every odd quad ) and every odd quad of chips (of chips (44) respectively) respectively

T ABLE 1 PHASE PARAM ETERS ENCO DING SCHEM E

DBIT PHASE PARAM ET ER (d1, d0) 1 (d3, d2) 2 (d5, d4) 3 (d7, d6) 4

T ABLE 2

DQ PSK M O DULATIO N O F PHASE PARAM ETERS

DBIT (d i+1,d i) PHASE 00 0 01 10 /2 11 -/2

QPSK modulatorQPSK modulator

LEGEND:LEGEND:

1 & 2 - balanced mixers1 & 2 - balanced mixers 3 - phase splitter3 - phase splitter 4 - carrier oscillator4 - carrier oscillator 5 - coupler5 - coupler 6 - band-pass filter6 - band-pass filter 7 - power amplifier7 - power amplifier 8 - antenna8 - antenna

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

Phase splitterPhase splitter

Low cost designLow cost design Constant phase Constant phase

difference among wide difference among wide working frequency driftworking frequency drift

Better performance up Better performance up to few hundred MHzto few hundred MHz

For higher frequency For higher frequency (UHF bands) can be (UHF bands) can be used micro strip lines used micro strip lines with length equal to with length equal to /4/4

Circuit diagram of the CCK Circuit diagram of the CCK encoderencoder

Block diagram of the Block diagram of the programprogram

ConclusionsConclusions

Improve performance for general multipath Improve performance for general multipath environments in radio transmissionenvironments in radio transmission

Transmitter’s part of the CCK transceiver is a low Transmitter’s part of the CCK transceiver is a low cost effective, but the receiver’s part is more cost effective, but the receiver’s part is more complexcomplex

The CCK waveform has better EThe CCK waveform has better Ebb/N/N00 performance performance

than DPSKthan DPSK DSSS with use of Barker’s code is more stable DSSS with use of Barker’s code is more stable

according to the according to the longlong range and distance between range and distance between transmitter and receiver transmitter and receiver in comparison with CCKin comparison with CCK

Thank you!Thank you!