CN117614530A - Radio frequency signal optical transmission delay control method - Google Patents

Abstract

The invention relates to the technical field of optical fiber communication, in particular to a radio frequency signal optical transmission delay control method, wherein a transmitter sets transmitter parameters, and a receiver sets receiver parameters; powering up the transmitter to send PPS measurement pulses to the receiver; the receiver carries out delay measurement on the PPS measurement pulse and carries out arithmetic average to obtain a delay value; the method comprises the steps of firstly transmitting PPS pulse before transmitting the radio frequency signal, measuring the delay value of the transmitted PPS pulse relative to the local PPS pulse at a receiver, and then adjusting the reading position of the FIFO of the receiver to adjust the radio frequency transmission delay to a set value, so that the aim of adjusting the radio frequency transmission delay is achieved, the method is suitable for the radio frequency signal digital optical fiber transmission system, has good universality, can automatically adjust the radio frequency signal transmission delay amount, and ensures the stability of the radio frequency signal transmission delay.

Description

Radio frequency signal optical transmission delay control method

Technical Field

The invention relates to the technical field of optical fiber communication, in particular to a method for controlling delay of optical transmission of radio frequency signals.

Background

In the radio frequency signal optical fiber transmission system, the transceiver is installed at different transmission nodes to complete the transmission and reception of service signals.

In the radio frequency signal analog optical fiber transmission system, a transmission link consists of an amplifier, an electric/optical conversion laser, an optical/electric conversion detector, an optical cable and the like. At the transmitter, the analog radio frequency signal is converted into an optical signal by a laser and output, and then transmitted to the receiver through an optical fiber, and a photoelectric detector of the receiver converts the input optical signal into an electric signal to recover the analog radio frequency signal. The whole transmission process is not processed by digital signals, the transmission delay of the radio frequency signals is determined by the physical characteristics of the transmission link device, and the transmission delay stability of the analog radio frequency signals can reach ps-level under the current manufacturing technical conditions depending on the working stability of the device.

In the radio frequency signal digital optical fiber transmission system, in a transmitter, the radio frequency signal needs to be subjected to analog-to-digital sampling, analog radio frequency signal is converted into a digital signal, then digital signal processing (including digital down conversion, interpolation filtering, JESD204B encoding and decoding, time scale data insertion, multi-channel high-speed data multiplexing, data line encoding and the like) is performed, the digital signal is packaged into a high-speed digital signal, then the high-speed digital signal is converted into an optical signal by a digital optical module, the optical signal is transmitted to a receiver through an optical fiber, the input optical signal is converted into a high-speed digital electric signal by the receiver optical receiving module, then digital signal processing (data line decoding, high-speed data de-multiplexing, time scale data decoding, radio frequency sampling data, interpolation filtering, digital up/down conversion and the like) is performed, and then the digital signal is converted into a radio frequency analog signal by a DAC circuit to be output. In the transmission process, the digital signal processing is performed, the initial states of the data signal processing are different, the radio frequency signal transmission delay is different, the equipment is actually measured to be turned on and off for multiple times, and the radio frequency delay variation range is about 40ns at maximum, namely the transmission delay stability is 40ns.

In a radar system, the transmission delay of a radio frequency signal is related to the distance of a measured object, and if the stability of the transmission delay is good, the distance accuracy of the measured object is high. The noise figure NF of the radio frequency signal transmitted by the digital optical fiber is irrelevant to the transmission distance, and has a longer transmission distance than that of the analog optical fiber. Aiming at the remote transmission requirement of radio frequency signals, a control circuit and a control method for the data optical transmission delay of the radio frequency signals need to be developed, and the requirement of the stability of the transmission delay of the radio frequency signals is met.

Disclosure of Invention

The invention aims to provide a control method for the optical transmission delay of a radio frequency signal, and aims to develop a control circuit and a control method for the optical transmission delay of data of the radio frequency signal, so as to meet the requirement of the stability of the transmission delay of the radio frequency signal.

In order to achieve the above object, the present invention provides a method for controlling delay of optical transmission of radio frequency signals, comprising the steps of:

setting transmitter parameters by a transmitter, and setting receiver parameters by a receiver;

powering up the transmitter to send PPS measurement pulses to the receiver;

the receiver performs delay measurement on the PPS measurement pulse and performs arithmetic average to obtain a delay value;

and adjusting the FIFO reading pointer based on the delay value, and switching the PPS measurement pulse signal into a transmission radio frequency signal to realize stable radio frequency signal transmission delay.

The transmitter comprises an ADC module, a first FPGA module, an electric/optical conversion module, a first filter and a first frequency synthesis module, wherein the first frequency synthesis module is respectively connected with the ADC module and the first FPGA module, the filter is respectively connected with the ADC module and the first FPGA module, and the electric/optical conversion module is connected with the first FPGA module.

The receiver comprises an optical/electrical conversion module, a second FPGA module, a DAC module, a second filter, a detection module, a shaping module and a second frequency synthesis module, wherein the optical/electrical conversion module is connected with the second FPGA module, the second FPGA module is connected with the shaping module, the second frequency synthesis module and the DAC module respectively, the DAC module is connected with the second FPGA module, the second frequency synthesis module and the second filter respectively, and the detection module is connected with the second filter and the shaping module respectively.

The transmitter parameter setting comprises ADC module parameter setting, first FPGA module parameter setting, electric/optical conversion module parameter setting and first frequency synthesis module parameter.

The receiver parameters comprise second frequency synthesis module parameter setting, optical/electrical conversion module parameter, detection module parameter setting and shaping module setting.

According to the method for controlling the optical transmission delay of the radio frequency signals, the transmitter parameters are set through the transmitter, and the receiver parameters are set through the receiver; powering up the transmitter to send PPS measurement pulses to the receiver; the receiver performs delay measurement on the PPS measurement pulse and performs arithmetic average to obtain a delay value; according to the method, before the radio frequency signals are transmitted, PPS pulses are transmitted, the delay value of the transmitted PPS pulses relative to local PPS pulses is measured at a receiver, and then the reading position of the FIFO of the receiver is adjusted, so that the radio frequency transmission delay is adjusted to a set value, the purpose of adjusting the radio frequency transmission delay is achieved, the method is suitable for a radio frequency signal digital optical fiber transmission system, the universality is good, the radio frequency signal transmission delay amount can be automatically adjusted, the transmission delay stability is less than or equal to 5ns, the stability of the radio frequency signal transmission delay is ensured, the setting is simple, the maintainability is good, and the method is simple and practical.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic connection diagram of an optical transmission delay control system for a radio frequency signal according to the present invention.

Fig. 2 is a schematic diagram of the optical transmitter operation of the present invention.

Fig. 3 is a schematic diagram of receiver FIFO delay adjustment.

Fig. 4 is a receiver workflow block diagram.

Fig. 5 is a flowchart of a method for controlling optical transmission delay of a radio frequency signal according to the present invention.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.

Referring to fig. 1 to 5, the present invention provides a method for controlling delay of optical transmission of radio frequency signals, comprising the following steps:

s1, setting transmitter parameters through a transmitter, and setting receiver parameters by a receiver;

specifically, the transmitter comprises an ADC module, a first FPGA module (FPGA module 1), an electric/optical conversion module (electric/optical conversion module 1), a first filter (filter 1) and a first frequency synthesis module (frequency synthesis module 1), where the ADC module CH1 is connected to the output of the filter 1, CH2 is connected to the external radio frequency signal input, the ADCCLK is connected to the frequency synthesis module 1, and the ADC module output is connected to the FPGA module 1; the FPGA module 1 is connected with the SPI of the frequency synthesis module 1, the 250MHz clock, the input of the filter 1 and the external PPST input, and the GTX output of the FPGA module 1 is connected with the input of the electric/optical conversion module; the input of the filter 1 is connected with the FPGA module 1, and the output of the filter is connected with the input of the ADC module CH 1; the input of the electric/optical conversion module is connected with the output of the FPGA module 1GTX, and the output is connected with an external transmission optical cable; the input of the frequency synthesis module 1 is connected with an external 100MHz reference clock T, and the output of the frequency synthesis module is respectively connected with the ADC module and the FPGA module 1;

the receiver comprises an optical/electrical conversion module (optical/electrical conversion module 2), a second FPGA module (FPGA module 2), a DAC module, a second filter (filter 2), a detection module, a shaping module and a second frequency synthesis module (second frequency synthesis module), wherein the input of the optical/electrical conversion module is connected with an external optical cable, the output of the optical/electrical conversion module is connected with the GTX input of the FPGA module 2, and the FPGA module 2 is also connected with the SPI of the DAC module and the frequency synthesis module 2 and a 250MHz clock; the DAC module data input is connected with the FPGA module 2, the CH1 is connected with the filter 2 input, and the CH2 outputs a radio frequency signal to the outside; the output of the filter 2 is connected with the input of the detection module, and the output of the detection module is connected with the input of the shaping module;

the ADC module is a dual-channel TXADC, the resolution is 14bit, the highest sampling frequency is 1.25GHz, the full-power bandwidth of analog input is 2GHz, JESD204B (subtype) codes serial digital output, the FPGA module 1 and the FPGA module 2 are provided with an XC7K325T-2FFG900 as a main chip, the filter 1 and the obtained filter 2 are DC-475 MHz low-pass filters, the passband ripple is 0.5dB, the insertion loss is less than or equal to 1.0dB, the rectangular coefficient of the frequency bandwidth is less than or equal to 0.5dB and less than or equal to 60dB, the frequency synthesizer module is a ZERO DELAY phase locking module, the reference frequency input range is DC-250 MHHz, the input level CMOS, LVDS or LVPECL level, the output is CMOS or LVPECL level, the output frequency range is 0-1.5 GHz, the number of output channels is 12, the additional jitter is less than or equal to 225fs, and the inter-channel output DELAY error is less than or equal to 16ps.

The electric/optical conversion module and the optical/electric conversion module are DWDM CH34 channel standard wavelength (1550.12 nm), the number of channels is 1, the output optical power is-5 dBm-0 dBm, the receiving sensitivity is less than or equal to-24 dBm, the saturated receiving power is more than or equal to 0dBm, the transmission data rate is less than or equal to 11.3Gb/s, and the maximum transmission distance is 100km.

The DAC module is a double-channel TxDAC, the resolution is 16 bits, the conversion rate is 1600Mb/s, the digital interpolation filter is not/2X/4X/8X/16V optional, and the inherent delay difference of TxDAC conversion is less than or equal to 2 DACCLK cycles.

The detection module is a microwave detector, the input frequency range is 0.01-4 GHz, the in-band fluctuation is less than or equal to +/-0.3 dB, and the low-level sensitivity (-30 dBm) is more than or equal to 0.5mV.

The shaping module is used for limiting the amplitude amplifier, the frequency bandwidth of-3 dB is 500MHz, the gain is 20dB, the output level is 0-4V, and the rising rate is 1350V/us.

S2, starting up and powering up the transmitter to send PPS measurement pulses to the receiver;

specifically, the transmitter is powered on by continuously transmitting PPS measurement pulses for 10 seconds to the receiver.

S3, the receiver carries out delay measurement on the PPS measurement pulse and carries out arithmetic average to obtain a delay value;

specifically, the receiver performs delay measurement on each received PPS measurement pulse with a local PPS pulse as a reference, and then selects the arithmetic average of the data with 6 delay values closest to each other, and the average value is used as the delay value of the transmission link.

Link delay measurement

When the power-on is started, the first frequency synthesizer module performs zero delay synchronous phase locking and frequency multiplication on an externally input 100MHz reference to generate a 1GHZ sampling clock (ADCCLK), a 1GHZ conversion clock (DACCLK) and a 250MHz FPGA data processing clock which have a fixed phase relation with the 100MHz reference.

When the transmitter is started, the FPGA module 1 generates a 300MHz clock by an input 250MHz clock, then the 300MHz clock and externally input PPST pulse are subjected to phase-to-phase, so that PPS measurement pulses are obtained, and the PPS measurement pulses are 300MHz FSK modulation signals with the period of 1 second.

And then the PPS measurement pulse is input to CH1 of an ADC module for analog-to-digital conversion, converted into ADC high-speed data, subjected to 375MHz data down-conversion and 4X interpolation filtering, converted into zero intermediate frequency IQ data, and then transmitted to the FPGA module 1 through a JESD204B high-speed interface.

The FPGA module 1 decodes and multiplexes the JESD204B sent by the ADC module, converts the JESD204B into a high-speed data stream after 8B10B encoding, and outputs the high-speed data stream to the electric/optical conversion module by using a GTX high-speed circuit.

The electrical/optical conversion module converts the high-speed data stream into a single-mode optical signal at a wavelength of 1550 nm. And then transmitted through the optical cable.

The second optical/electrical receiving module performs photoelectric conversion on the input optical signal, recovers a high-speed data galvanic signal, and inputs the high-speed data galvanic signal to the FPGA module 2 through the differential circuit.

And the FPGA module 2GTX interface receives and decodes the high-speed signal, recovers IQ data and outputs the IQ data to the DAC module.

The DAC module performs interpolation filtering and digital orthogonal up-conversion on the input IQ data, converts a baseband signal into a 375MHz digital radio frequency signal, and then performs digital-to-analog conversion on the DAC module to output a PPS measurement pulse analog signal.

The PPS measuring pulse analog signal is filtered by a filter 2 to obtain an image, then the image is input into a detection module to carry out amplitude detection to recover a PPS pulse signal, and the PPS measuring pulse is recovered after being shaped by a shaping module.

The PPS measurement pulse 2 is input to the FPGA module 2 to perform delay measurement with the local PPSR pulse as a time reference. The transmitter transmits PPS measurement pulses 1 for 10 seconds, for a total of 10 PPS measurement pulses. The receiver measures the delay value of each pulse separately, and then selects the mathematical average of the 6 closest delay values as the transmission delay value (Tpf) for this power-on.

The furthest distance (100 km) between the transmitting station and the receiving station sets the delay value Tpf0 to 800us.

S4, based on the delay value, adjusting the FIFO reading pointer, and switching the PPS measurement pulse signal into a transmission radio frequency signal, so as to realize stable radio frequency signal transmission delay.

Specifically, the FIFO read pointer of the FPGA module 2 is adjusted according to the calculated delay value, so that the delay after the IQ data output to the DAC module is converted into the radio frequency signal meets the requirement, and then the transmitter transmits the PPS measurement pulse signal and switches to transmit the radio frequency signal, so as to realize stable transmission delay of the radio frequency signal. The 100MHz reference clock and the PPS signal used by the device are synchronous coherent signals provided by the Beidou time service device.

Delay adjustment:

the delay time delta T=800 us-Tpf to be adjusted is that the FIFO read pointer of the FPGA module 2 is adjusted according to delta T, so that the link transmission is delayed to the set value.

And stopping PPS measurement pulse sampling of the ADC module, starting radio frequency signal analog-to-digital sampling of the ADC module CH2, converting the radio frequency signal analog-to-digital sampling into radio frequency ADC high-speed data, then replacing the PPS measurement pulse high-speed data with the radio frequency high-speed data for processing, transmitting the PPS measurement pulse in the same processing process, and finally converting and outputting a radio frequency analog signal by the DAC module.

Before FIFO adjustment, the delay Tpf of the PPS measurement pulse 2 relative to PPSR adjusts the FIFO read pointer of the FPGA module 2 according to the measurement value, so that the PPS measurement pulse 2 is delayed to the position of Tpf 0. The magnitude of Tpf0 is determined by the transmitter and receiver maximum transmission delay values (about 100 ns) and the maximum fiber transmission distance (150 km) before adjustment. Tpf0 should be equal to or greater than 100ns+100km 5 us/km=600us, with the device Tpf0 set to 800us. A receiver FIFO delay adjustment schematic is shown in fig. 3.

The above disclosure is merely illustrative of a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and those skilled in the art will understand that all or part of the above embodiments may be implemented and equivalent changes made in the claims of the present invention still fall within the scope of the invention.

Claims (5)

1. The radio frequency signal light transmission delay control method is characterized by comprising the following steps:

setting transmitter parameters by a transmitter, and setting receiver parameters by a receiver;

powering up the transmitter to send PPS measurement pulses to the receiver;

the receiver performs delay measurement on the PPS measurement pulse and performs arithmetic average to obtain a delay value;

and adjusting the FIFO reading pointer based on the delay value, and switching the PPS measurement pulse signal into a transmission radio frequency signal to realize stable radio frequency signal transmission delay.

2. The method for controlling optical transmission delay of RF signal according to claim 1, wherein,

the transmitter comprises an ADC module, a first FPGA module, an electric/optical conversion module, a first filter and a first frequency synthesis module, wherein the first frequency synthesis module is respectively connected with the ADC module and the first FPGA module, the filter is respectively connected with the ADC module and the first FPGA module, and the electric/optical conversion module is connected with the first FPGA module.

3. A method for controlling optical transmission delay of RF signal according to claim 2, wherein,

the receiver comprises an optical/electrical conversion module, a second FPGA module, a DAC module, a second filter, a detection module, a shaping module and a second frequency synthesis module, wherein the optical/electrical conversion module is connected with the second FPGA module, the second FPGA module is connected with the shaping module and the second frequency synthesis module respectively, the DAC module is connected with the second FPGA module, the second frequency synthesis module and the second filter respectively, and the detection module is connected with the second filter and the shaping module respectively.

4. A method for controlling optical transmission delay of RF signal according to claim 2, wherein,

the transmitter parameter setting comprises ADC module parameter setting, first FPGA module parameter setting, electric/optical conversion module parameter setting and first frequency synthesis module parameter.

5. A method for controlling optical transmission delay of RF signal according to claim 3,

the receiver parameters comprise second frequency synthesis module parameter setting, optical/electrical conversion module parameter, detection module parameter setting and shaping module setting.