CN102590787A - Double early-late loop tracking method of spread spectrum receiver - Google Patents

Abstract

The invention relates to a dual early-late loop tracking method for a spread spectrum receiver, which is composed of two early-late tracking loop circuits, an energy comparison module, a control signal gating module, and a tracking loop output module. The invention has the advantage of providing a tracking method for a spread spectrum receiver, which effectively improves the tracking accuracy of the receiver while ensuring the dynamic performance of the tracking loop, thereby improving the positioning accuracy including but not limited to real-time positioning systems.

Description

Double Early-Late Loop Tracking Method for Spread Spectrum Receiver

technical field

The invention relates to a new tracking method for a spread spectrum receiver. More specifically, it is a spread spectrum tracking method that uses parallel two-way tracking loops to reduce the jitter of the local spread spectrum code, thereby reducing the positioning error of the spread spectrum positioning system due to the jitter of the local code of the receiver.

Background technique

A general spread spectrum positioning system consists of a transmitting tag and a spread spectrum receiver. The basic positioning principle is to calculate the positioning by the time difference between the signal transmitted by the tag and the receiver placed in different positions. The jitter of the spread spectrum receiver tracking the ring local code sooner or later is one of the important sources of positioning errors in the positioning system using spread spectrum technology. In order to improve the positioning accuracy, the common method is to increase the clock frequency and reduce the loop bandwidth, but this method will cause the dynamic performance of the loop to deteriorate, which is not conducive to the despreading and demodulation of burst signals, and has a greater impact on the hardware performance of the receiver. strict requirements.

The double early-late loop tracking method of the spread spectrum receiver is an effective method to improve the positioning accuracy. It uses two identical tracking loops with opposite clock phases and wide bandwidth to track the spread spectrum signal, compares the four leading and lagging signals output by the two tracking loops, and then adjusts the phase of the final local code. While ensuring the tracking dynamic performance, the tracking accuracy is effectively improved. Under the condition of the same tracking accuracy, the required system clock frequency can be reduced by half, so the requirement for hardware resources can be effectively reduced.

Contents of the invention

The purpose of the present invention is to propose a new tracking method for a spread spectrum receiver, which can effectively improve the tracking precision while ensuring the dynamic performance of the tracking loop, and reduce the requirement for hardware performance under the same tracking precision condition.

The technical solution of the present invention is: a double early-late loop tracking method of a spread spectrum receiver, which is composed of two early-late tracking loop circuits, an energy comparison module, a control signal gating module, and a tracking loop output module, the control The frequency of the clock signal includes but is not limited to 160MHz. The system global clock and its antiphase clock each control a tracking loop to track the captured signal; the energy comparison module makes a judgment on the leading and lagging signals generated by the two tracking loops NCO, and outputs the control signal according to the judgment result The control signal gating module gates the control clocks and NCO clocks of the two tracking loops according to the control signals, and the tracking loop output module uses the gated clock signals and code clock control signals to output higher-precision tracking results. The bandwidth of the receiver tracking loop is the same as that of tracking loops 1 and 2, so the same tracking dynamic performance is maintained while the tracking accuracy is improved

The invention has the advantages of providing a dual early-late loop tracking method applicable to a spread spectrum receiver including but not limited to a real-time positioning system. This method can effectively improve the tracking accuracy of the spread spectrum receiver while ensuring the dynamic performance of the tracking loop under limited hardware conditions, thereby improving the positioning accuracy of the system.

Description of drawings

Figure 1 is a block diagram of a spread spectrum receiver.

Figure 2 is the native pseudocode trace result in the oscilloscope.

Detailed ways

The present invention will be further described in detail below. Referring to Fig. 1, the present invention is composed of two early and late tracking loop circuits, an energy comparison module, a control signal gating module, and a tracking loop output module.

The functions completed by the two early and late tracking loop circuits are: respectively track and lose capture judgment on the captured intermediate frequency signal. If the judgment is lost capture, the recapture control signal is set to 0, and the capture circuit performs recapture.

The function completed by the B energy comparison module is: if the two tracking loops have realized the signal tracking, the energy comparison module performs square operation on the input energy values of the leading and lagging four signals generated by the two tracking loops NCO and then compares them , if the energy maximum value is generated in the tracking loop 1, the clock selection signal is set to 0, otherwise it is set to 1.

The functions completed by the C control signal gating module are: since the control clocks of the two tracking loops are reversed, that is, the sequence is different, so this module uses methods including but not limited to logic assignment to control the control clocks of the two tracking loops and the NCO clock. strobe. When the clock selection signal is 0, the control clock and NCO clock of tracking loop 2 are output, and if the clock selection signal jumps to 1, the control clock and NCO clock of tracking loop 1 are output.

The functions completed by the D tracking loop output module are: use the gated control clock and NCO clock to control the NCO to generate a new set of local pseudo codes for despreading and demodulation, and reduce the jitter range of the local pseudo code signal to tracking Half of the jitter range of the local pseudo-code signal output by loops 1 and 2.

This method is used in the spread spectrum real-time positioning system receiver (not limited to) equipment, when the frequency of the control clock and its inverse clock is 160MHz, the oscilloscope tracking result is shown in Figure 2, the upper signal is the pseudo code transmitted by the tag, The signal below is the local pseudo code generated by the output module of the receiver tracking loop (there is a fixed processing delay and path delay). The ultimate level of tracking accuracy can be achieved under 320MHz clock control.

Claims (5)

1. A kind of new double early-late loop tracking method of spread spectrum receiver, it is made of two early-late tracking loop circuits, energy comparison module, control signal gating module, tracking loop output module. 2. The tracking method according to claim 1, characterized in that the system control clock and its inverted clock each control a tracking loop to track the captured signal. 3. The tracking method according to claim 1, characterized in that the leading and lagging signals produced by the two tracking loops NCO are sent to the energy comparison module, and the clock selection signal is output after a large decision is made. 4. The tracking method according to claim 1, characterized in that the control signal gating module gates the control clocks and NCO clocks of the two tracking loops using methods including but not limited to logic assignment. 5. The despreading demodulation method according to claim 1, characterized in that the tracking loop output module uses the clock signal after gating and the NCO clock control signal to output a higher precision tracking result.

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