A Phase-Locked Loop Circuit for Capturing Weak Carrier Signals

Abstract

The invention provides a phase-locked loop circuit for implementing weak carrier signal acquisition. The phase-locked loop circuit comprises a first phase discriminator, a loop filter, a voltage-controlled oscillator (VCO), an adder and a scanning voltage generation circuit, wherein the first phase discriminator, the loop filter, the adder and the VCO form a loop to acquire and track weak carrier signals, the adder is used for adding loop integral voltage and scanning voltage, and then inputting the sum into the VCO; the scanning voltage generation circuit analyzes and generates scanning voltage by utilizing the input weak carrier signals and signals outputted by the VCO. According to the phase-locked loop circuit, acquisition bandwidth is increased by utilizing the externally added scanning voltage in an acquisition assisting method, so that complete acquisition within Doppler bandwidth is implemented, signal Doppler bandwidth requirements are met, and high-sensitivity broadband acquisition and tracking are achieved with the assistance of digital-control scanning voltage.

Description

technical field

[0001] The invention relates to the field of phase-locked loop circuits, in particular to a phase-locked loop circuit for capturing weak carrier signals. Background technique

[0002] The acquisition of weak carrier signals is a technical difficulty in the design of high-zero-sensitivity receivers, especially in the field of deep space communication. Since the communication distance exceeds one million kilometers, the signal attenuation is very large, and the receiver is required to have high sensitivity. Signal levels below -140dBm. In this regard, the acquisition and tracking of ultra-low signals cannot be achieved by using a conventional phase-locked loop circuit, and the loop acquisition bandwidth must be narrowed. However, the Doppler frequency shift of the moving carrier is generally large, and the narrow capture band is in contradiction with the large Doppler bandwidth, so it is impossible to capture weak carrier signals within the entire Doppler band...

Images