Delay-lock phase-locked tracking of PN signals (DPTL)

Abstract

A novel pseudonoise (PN) code tracking loop, 'delay-lock phase-locked tracking loop (DPTL)' is described. As a PN code synchronization system, a delay-lock loop (DLL) has been widely used. It is known that the 1 Delta -DLL's tracking performance as high SNR is good, while the 2 Delta -DLL is superior to the 1 Delta -DLL at low SNR. However, the tracking point of the 2 Delta -DLL widely sways near zero point. So, the authors propose a novel PN code tracking loop, which consists of a DLL followed by a phase-locked loop (PLL) to reduce jitter of on-time signal of the DLL; they call this system delay-lock phase-locked tracking loop (DPTL). They evaluate the performance of the DPTL by theory and computer simulation. Moreover, they also evaluate the performance of the DPTL using an improved DLL (IDLL) whose phase comparator characteristics is extended as a DLL (this system is called EDPTL). The following results are obtained: (1) The DPTL is superior to DLL for jitter property and in-lock rate, (2) The EDPTL has the highest in-lock rate performance of the DPTLs under the large noise environment and improves about 2.5(dB) compared with the 1 Delta -DLL and about 1.5(dB) compared with the 2 Delta -DLL. >