On the basis of coded realization of IJF digital basedand of FPGA
At the beginning of the eighties of the 20th century, Wo, fee Professor He (K.Feher) of the university of China very much of Canada The leader's scientific research group has invented IJF-OQPSK modulation technique. IJF-OQPSK Chinese name is named having intersymbol interference with shaking - mixed with quadrature phase-shift keying. He is that the modern figure envelops one of the new modulation technique in modulation technique permanently.
Carry on the modulation, should first the intersection of logarithmic word and baseband signal go on IJF encode, do not vary it into one and have intersymbol interference and shaking, the spectral main lobe is narrow, base band waveform with fast roll-off, then modulate using OQPSK. In this way, the baseband signal after modulating has the following characteristics: Smooth continuously with the phase place of the wave regulating, and inner phase change of each number will not exceed π / 2, it is enveloped that almost permanent by the enveloping of the wave regulating, the spectral main lobe is narrow, the high-frequency roll-off is fast, out-of-band energy is low.
In the digital transmission system, it is value and deflection of the iderl value on the sampling point of received signal that have direct relation with the bit error rate. If get rid of the influence of the noise, then the error mainly comes from the shaking regularly of intersymbol interference and sampling point in the transmission course. In actual Engineering system, with endure Kui Sri Lankan special pulse, represent the random binary data, his main lobe takes 2b width. Endure Kui Sri Lankan special pulse, tow caudal existence, make, formate corrugate to pass leftwards zero or right deflect, produce and shake regularly. In addition, even can lead to the fact the corrugate range to rise and fall while being tailing, make the bit error rate raise. IJF coded characteristic adopts a kind of new shaping pulse of base band - -The space impulse of one pair of code elements of the time limit, because it does not exist and shake the tail, thus dispelled intersymbol interference and shook regularly.
2.1 IJF code waveform - -One pair of code elements of time limit separates by the raised cosine pulse
One pair of code elements separates by the raised cosine pulse, look on as the coefficient a of the roll-off =At 1 o'clock, its expression is:
Other characteristics are as follows:
( 1) The edge of pulse, namely t =
