Digital system and method of estimating non-energy parameters of signal carrier

摘要

Navigation satellite receivers have a large number of channels, where phase discriminators and loop filter of a PLL operate in phase, with data bits and control of numerically controlled oscillator (NCO) carried out simultaneously on all channels. Since symbol boundaries for different satellites do not match, there is a variable time delay between the generation of control signals and NCO control time. This delay may be measured by counting a number of samples in the delay interval. A proposed system measures non-energy parameters of the BPSK signal carrier received in additive mixture with noise when a digital loop filter of PLL controls NCO with a constant or changing in time delay. A control unit controls bandwidth and a LF order by changing transfer coefficients based on analyzing estimated signal parameters and phase tracking error at a PD output.

主权项

1. A system for estimating non-energy parameters of a signal carrier, the system comprising:
a digital phase locked loop (PLL) that tracks an input signal and includes
(i) a digital numerically controlled oscillator (NCO) configured to generate a complex sinusoidal signal,(ii) a digital mixer configured to down-convert a digitized version of the input signal to a base-band complex signal centered at a zero frequency using the output of the NCO,(iii) an accumulator unit (AU) including two accumulators with a reset connected to outputs of the digital mixer, and(iv) a phase discriminator (PD) coupled to outputs of the AU;(v) a digital loop filter (LF) connected to the PD output for controlling the NCO, wherein a time delay of the PD output is variable; an estimator unit (EU) connected to the LF and estimating a phase of the input signal and derivatives of the phase as the non-energy parameters; and a delay meter measuring a delay of the PD output and providing the delay to the LF and EU.