CN103149574B - Method and device for simulating link channel between navigation satellites - Google Patents

Abstract

The invention discloses a navigation satellite inter-satellite link channel simulation method, which at least includes the following steps: using a first frequency to store the original signal; using a second frequency to read the stored signal; and using the stored signal to perform carrier wave Modulation: performing power control on the stored signal modulated by the carrier and then outputting it. At the same time, the present invention also discloses a channel simulation device, including: a signal reading and writing module for storing the original signal by using the first frequency, and reading the stored signal by using the second frequency; A signal modulation module; a power control module for controlling the power of the stored signal modulated by the carrier. The invention can add time delay, Doppler frequency shift and power attenuation to the original signal, thereby simulating the transmission of the original signal in the channel.

Description

Navigation satellite inter-satellite link channel simulation method and device

technical field

The invention belongs to the technical field of satellite navigation, and relates to a navigation satellite inter-satellite link channel simulation method and device.

Background technique

The global satellite navigation system represented by the GPS of the United States has recently added inter-satellite links, so as to realize the autonomous navigation of networked satellites without the support of the ground master control station. At present, GPS has improved the user positioning accuracy from 5000m to 6m within a 180-day forecast period through this technology, which has significantly improved the usability of GPS in war and other special environments. my country's Beidou satellite navigation system is currently designing the Beidou satellite inter-satellite link scheme, and the navigation satellite inter-satellite link signal simulation method can provide the ground design verification of the scheme.

The satellite navigation constellation inter-satellite link signal generation system is the key equipment to solve the ground verification problem of navigation satellite onboard equipment. Radio frequency signal simulation According to the mathematical simulation model of the intersatellite link, the real intersatellite link signal is simulated, and the intersatellite link radio frequency signal is generated in real time, which can be used for the verification of the intersatellite link scheme and the research and development of the intersatellite link receiver.

Due to the foreign blockade of the inter-satellite link technology, it is not yet possible to find relevant literature on foreign inter-satellite link signal generation systems. However, domestic navigation satellite inter-satellite link signal generation technology is still in its infancy. Moreover, most of the current simulations of inter-satellite link signals use software simulation, and the simulation effect is close to the theoretical analysis results, and the authenticity is poor. For navigation satellite inter-satellite links, the use of radio frequency signal simulation will increase the authenticity of signal simulation, and can carry out ground verification of future engineering implementation schemes in real time.

Contents of the invention

The technical problem solved by the present invention is: on the one hand, the present invention provides a navigation satellite inter-satellite link channel simulation method, by which time delay, Doppler frequency shift and power attenuation can be added to the original signal, so that the original signal can be simulated The transmission of signals in a channel.

At the same time, the present invention also provides a channel simulation device, which realizes the delay of the original signal and the addition of Doppler frequency offset by using different frequencies to read and write the original signal, and uses the signal modulation module and the power control module An analog signal suitable for the signal characteristics is obtained.

Technical solution of the present invention is:

A navigation satellite inter-satellite link channel simulation method at least includes the following steps:

storing the original signal by using the first frequency;

Using a second frequency to read the stored signal, the second frequency may be equal to or different from the first frequency;

performing carrier modulation on the stored signal;

and outputting the stored signal after carrier modulation after power control.

The original signal is a baseband spread spectrum signal.

The original signal is a single-channel signal or a two-channel signal that is mutually orthogonal.

The power control is to add attenuation to the stored signal modulated by the carrier.

A channel simulation device, comprising:

A signal reading and writing module that stores the original signal by using the first frequency, and reads the stored signal by using the second frequency;

A signal modulation module that performs carrier modulation on the stored signal;

The power control module performs power control on the stored signal modulated by the carrier.

It also includes a signal demodulation module for obtaining the original signal through demodulation; the original signal is a baseband spread spectrum signal.

The power control module is used for adding attenuation to the stored signal modulated by the carrier.

Compared with the prior art, the present invention has the following advantages:

The present invention sequentially reads and stores the original signal through the first frequency and the second frequency, thereby utilizing the difference between the two frequencies to complete the operation of adding code Doppler and carrier Doppler to the original signal, and at the same time, After the code Doppler and carrier Doppler are added, the modulated signal is further power controlled, thus completing the simulation of signal attenuation during transmission. In the specific engineering stage, the signal simulation process can determine the first frequency, second frequency and power control parameters used according to the specific conditions of code Doppler, carrier Doppler and signal attenuation, so the implementation is simple and can be Strong scalability.

Description of drawings

Fig. 1 is the simulation process diagram of Doppler frequency offset;

Fig. 2 is a block diagram of the signal simulation module;

Detailed ways

The present invention will be further introduced below in conjunction with the accompanying drawings.

The transmission of the signal in the channel will cause time delay, Doppler frequency deviation and power attenuation. In one embodiment of the present invention, in order to generate the analog signal of the navigation satellite, it is necessary to add the simulation of the channel to the analog navigation satellite signal modulated on the carrier generated locally according to the situation of the navigation satellite channel, that is, the simulation of the channel for the analog navigation satellite The signal produces time delay, Doppler frequency shift and power attenuation.

In order to achieve the above purpose, in this embodiment, the original signal can be the signal obtained after demodulation of the above-mentioned analog navigation satellite signal, which is stored according to the first frequency, and the stored signal is read according to the second frequency after the storage is completed. The signal is thus added to the original signal by the time difference between storing and reading as a delay in transmission over the channel. Moreover, the first frequency is different from the second frequency, so that a frequency offset may be generated during storage and reading, that is, a Doppler frequency offset is added to the original signal.

The time delay and Doppler frequency offset can be set according to the condition of the channel to be simulated. Since in the signal transmission process, the Doppler of the carrier and the code are opposite frequency offsets in some cases (such as in the ionosphere), it is necessary to separate the Doppler of the carrier and the code for simulation.

The simulation process is shown in Figure 1, assuming that the carrier frequency of the original signal is fRF, the bandwidth is B, the relative speed of the signal transmitting and receiving ends is v, and the speed of light is c, then its Doppler Δf=fRF*v/c, and the receiving end receives The signal bandwidth B'=B*(1+v/c), and the radio frequency carrier is: fRF'=fRF+Δf=fRF*(1+v/c).

The Doppler simulation generated by the signal during propagation is simulated on the carrier and the code respectively. The whole process is that the original signal is first down-converted to the intermediate frequency fc, and the baseband signal is obtained after the carrier is stripped by phase-locked loop mixing and filtering. Sampling at fw rate and storing in memory; reading memory data at fr rate, modulated to the carrier frequency of fc+Δf, and modulated to radio frequency through up-conversion to realize Doppler function of channel simulation. This process performs Doppler simulations on the carrier and code separately.

● Carrier Doppler simulation

On the carrier, set the carrier frequency modulated by the intermediate frequency output signal at the back end as fc+Δf, and after up-conversion to radio frequency, the carrier frequency is fRF+Δf, realizing the Doppler simulation of the carrier.

● Code Doppler simulation

On the code, the relationship between the storage read clock and the corresponding bandwidth is fr/B`=fw/B; when the read clock is set to fr=fw*(1+v/c), its bandwidth is B`= B*(1+v/c), so when the signal is stored with fw and the signal is read with fr, the Doppler simulation of the code can be realized.

In the above process, the original signal can be a baseband signal on a carrier after demodulation, or a spread spectrum signal obtained by demodulating an analog navigation satellite signal.

After the addition of the above-mentioned time delay and Doppler frequency offset is completed, the signal can be systemized into the carrier by using the carrier modulation technology. The carrier modulation technology can be BPSK or QPSK, etc., so as to generate a corresponding single-channel signal or I/Q two-way signal.

For the signal modulated by the carrier, the signal is further attenuated through power control, so as to complete the simulation after the signal passes through the entire channel.

In another embodiment of the present invention, the channel simulation of the original signal can be completed by using the channel simulation device, as shown in FIG. 2 , the channel simulation device includes a signal reading and writing module, a signal modulation module and a power control module.

The signal reading and writing module uses two different frequencies to store and read the original signal, and can process one or two parallel input original signals. One implementation method includes input/output FIFO, the first frequency Generator, second frequency generator, peripheral RAM.

The first frequency generator is used to generate the frequency fw for storing the original signal, and the second frequency generator is used for generating the frequency fr for reading the original signal. The input FIFO first receives the input original signal, and the signal in the input FIFO is stored in the peripheral RAM according to the frequency fw. After the storage is completed, it is read from the peripheral RAM according to the frequency fr, and is processed again through the output FIFO. output.

The signal modulation module performs carrier modulation on the signal output by the signal reading and writing module. The carrier modulation method can modulate the signal according to the carrier modulation mode of the analog transmission signal in the channel. For example, in the application of navigation satellites, the carrier modulation adopts QPSK , therefore, its carrier modulation can adopt QPSK.

The signal output by the signal modulation module is power controlled in the power control module. In order to adapt to the signal attenuation of channel transmission, in this module, the signal after carrier modulation is multiplied by the attenuation coefficient to obtain the power control. Attenuates the signal.

In the above device, in order to obtain the original input signal, the device can also include a signal demodulation module, the signal demodulation can remove the carrier of the input signal, but retain the spreading code of the input signal, so as to obtain the original signal of the spread spectrum, or All the carrier spreadable codes of the input signal are removed, so as to obtain the original non-spread spectrum. One implementation of this module is to include a local carrier generator and a phase detector. The local carrier generator generates a local carrier suitable for the carrier of the input signal, and the carrier of the input signal is removed by the local carrier so that the input signal can be modulated to Baseband, the input signal after removing the carrier is output to the phase detector at the same time, and the phase detector adjusts the carrier output of the local carrier generator according to the input baseband signal, so as to further generate a local signal suitable for the input signal carrier carrier. In another implementation manner of the module, it may further include a spreading code generator, configured to generate a spreading code to spread the baseband signal.

Parts not described in detail in the present invention belong to the common knowledge of those skilled in the art.

Claims (2)

1. a Navsat inter-satellite link channel simulation method, is characterized in that at least comprising the following steps:

First frequency is utilized original signal to be stored;

Utilize second frequency to read and store rear signal;

Signal after described storage is carried out carrier modulation;

Carry out exporting after power controls to the described storage signal after carrier modulation;

Described original signal is base-band spread-spectrum signal;

Described original signal is one-channel signal or simple two-way signal orthogonal each other;

Described power controls as adding decay to the storage signal after described carrier modulation.

2. a channel simulation device, is characterized in that, comprising:

Utilize first frequency original signal to be stored, and utilize second frequency to read the signal module for reading and writing storing rear signal;

Signal after described storage is carried out to the signal madulation module of carrier modulation;

Storage signal after carrier modulation is carried out to the power control module of power control;

Also comprise the signal receiving module being obtained described original signal by demodulation; Described original signal is base-band spread-spectrum signal;

Described power control module is used for the storage signal after for described carrier modulation and adds decay.