| 摘要 |
PURPOSE: A demodulator of a CDMA system is provided to render an on-time signal to be stronger than an early signal or a late signal against a communication environment by outputting a lock detect signal only when a receive signal strength indicator of the on-time signal is greater than that of the early signal or the late signal of a PN(pseudo noise) sequence and greater than a reference value of a lock comparing unit. CONSTITUTION: An on-time back diffusion unit(2b) and an early-late back diffusion unit(2e) multiply a signal of an in-phase component(I) and an orthogonal component(Q) as received and a PN sequence having a different phase, back-diffuse it, multiply and add a correlation value for the back-diffused in-phase component(I) and the orthogonal component(Q), thereby calculating an energy value for the correlation value of the in-phase and orthogonal components. A receive signal strength comparing unit(30) compares values outputted from on-time, early and late receive signal strength detecting units(5,10,20), and outputs a value to a lock comparing unit(6) if the on-time receive signal strength is greater than the early and late receive signal strength. The lock comparing unit(6) compares the on-time receive signal strength with a pre-set reference value, and outputs a lock detect signal if the on-time receive signal strength is greater than the pre-set reference value. The lock detect signal enables a time tracking unit(8), and if the early receive signal strength is greater than the late receive signal strength calculated by an early-late subtracter(7), the lock detect signal advances the phase of a PN sequence generator, while if the early receive signal strength is not greater than the late receive signal strength, the phase of the PN sequence generator is rendered to be slow, which is repeatedly performed until a synchronization is obtained.
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