CN103546408B

CN103546408B - Modulating signal source

Info

Publication number: CN103546408B
Application number: CN201310535574.4A
Authority: CN
Inventors: 杨杰; 孙敏; 杨光
Original assignee: Sichuan Jiuzhou Electric Group Co Ltd
Current assignee: Sichuan Jiuzhou Electric Group Co Ltd
Priority date: 2013-11-01
Filing date: 2013-11-01
Publication date: 2017-01-11
Anticipated expiration: 2033-11-01
Also published as: CN103546408A

Abstract

The invention relates to the technical field of digital communication, and discloses a modulating signal source. The modulating signal source comprises two dot frequency sources, a DDS, two frequency mixers and an FPGA control circuit, wherein the output of the first dot frequency source is coupled to the DDS and the first frequency mixer, and serves as a reference clock signal of the DDS and a local oscillator signal of the first frequency mixer, and the output of the second dot frequency source is coupled to the second frequency mixer, and serves as a local oscillator signal of the second frequency mixer. The DDS and the FPGA control circuit carry out interaction, and an output signal inside the DDS serve as a clock signal of the FPGA control circuit. The first frequency mixer and the second frequency mixer are connected to the output end of the DDS in series, and are used for carrying out secondary frequency mixing on the output signal of the DDS. Compared with the prior art, according to the technical scheme, due to the fact that signals generated by the same device can be applied to a plurality of positions at the same time, the system structure can become simple, the module size is reduced, module cost is reduced, and quality of modulating signals is improved.

Description

Modulating signal source

Technical field

The present invention relates to digital communication technology field, particularly to a kind of modulating signal source.

Background technology

MSK(Minimum Shift Keying, minimum shift keying) signal due to have constant-envelope, Phase Continuation, frequency power density concentrate, reliability high, be widely used in microwave, shortwave with And in satellite communication.For MSK modulated signal, its bit rate is the highest, and capacity of resisting disturbance is the strongest, The confidentiality of communication is the best, and data throughput energy is the biggest.

Traditional mode realizing MSK modulated signal is as it is shown in figure 1, its signal source is to utilize two paths of signals to mix Frequently obtaining after superposition, if realizing msk signal by this way, multiple discrete numeral and mould will be used Intending device, this will certainly increase the volume of system, improves the debugging difficulty of system, and increases the exploitation of system Cost.And the scheme in Fig. 1 have employed four mixting circuits and realizes, and for mixting circuit, its Local oscillator leakage and image frequency signal are the biggest on the impact of radiofrequency signal, and this impact can be passed through sometimes Wave filter filters, and is the most but difficult to filter, and it is the most difficult that the most this scheme implements.

Although also having now the most other two ways to realize msk signal: a kind of feature being to utilize DDS, With FPGA(or single-chip microcomputer) control DDS directly produce msk signal；The second is to utilize FPGA to simulate DDS Partial function, after signal is exported by FPGA, through D/A conversion produce msk signal.But both modes depend on So there is a lot of shortcoming, such as output frequency typically at below 100MHz, it is impossible to realize L-band and above frequency The radio frequency output of rate；And record according to disclosed document, the MSK modulated signal realized in both ways, Its bit rate is relatively low, all at below 1Mb/s.

Summary of the invention

For the drawbacks described above of prior art, the technical problem to be solved is such as how simple structure Make the MSK modulated signal realizing high bit rate, high signal quality.

For solving above-mentioned technical problem, the invention provides a kind of modulating signal source, described modulating signal source bag Include: two some frequency sources, a DDS, two frequency mixers and FPGA control circuit, wherein,

The output in first frequency source couples described DDS and the first frequency mixer, simultaneously as described DDS's simultaneously Reference clock signal and the local oscillation signal of described first frequency mixer；

The output in second point frequency source couples the second frequency mixer, as the local oscillation signal of described second frequency mixer；

Described DDS is mutual with described FPGA control circuit, using the output signal within described DDS as institute State the clock signal of FPGA control circuit；

Described first frequency mixer and described second frequency mixer are serially connected with the outfan of described DDS, to described DDS Output signal carry out secondary mixing.

Preferably, the output signal of described DDS is MSK modulated signal.

Preferably, the output signal of described DDS is filtered by said two frequency mixer the most simultaneously.

Preferably, the initial signal end in said two point frequency source couples with same crystal oscillator.

Preferably, the output frequency in said two point frequency source is specified by described FPGA control circuit.

Preferably, described FPGA control circuit provides msk signal control code for described DDS.

Preferably, the output in described first frequency source couples described DDS and described the by a power splitter simultaneously One frequency mixer.

Preferably, the clock signal of described FPGA control circuit is defeated by 4 frequency divider institutes within described DDS Go out.

Preferably, after described secondary mixing, signal frequency is more than L-band.

Preferably, after described secondary mixing, the bit rate of signal is 16Mb/s.

Compared with prior art, the signal that same device produces is applied simultaneously to many by technical scheme Place so that system structure becomes simple, thus reduces module volume, reduces module cost, and improves Modulated signal quality.

Accompanying drawing explanation

Fig. 1 is the structural representation of MSK modulating signal source in prior art；

Fig. 2 is the structural representation of the modulating signal source described in one embodiment of the present of invention；

Fig. 3 is the frequency spectrum of output one the more MSK modulated signal of standard in the preferred embodiments of the present invention Figure；

Fig. 4 is the signal quality schematic diagram of the MSK modulated signal in Fig. 3.

Detailed description of the invention

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clearly Chu, it is fully described by.Obviously, described embodiment is to implement the better embodiment of the present invention, described For the purpose of description is the rule so that the present invention to be described, it is not limited to the scope of the present invention.The present invention Protection domain should be as defined in claim, based on the embodiment in the present invention, this area is general The every other embodiment that logical technical staff is obtained on the premise of not making creative work, broadly falls into The scope of protection of the invention.

Traditional MSK modulating signal source is too much due to the device used, the mutual shadow of signal between each device The MSK modulated signal that sound, very difficult acquisition bit rate and quality are higher.This situation is when signal frequency is the highest It is more obvious, and to suppress spuious that system design and hardware cost are had again higher requirement.The present invention's In embodiment, in order to realize more preferable spurious reduction index, reduce the design difficulty of RF output end wave filter, Use secondary mixing scheme, the signal that same device produces is applied simultaneously to many places, decreases number of devices While decrease the mutual interference between unlike signal, it is achieved thereby that high bit rate, high signal quality as far as possible MSK modulated signal.

In one embodiment of the invention, as in figure 2 it is shown, modulating signal source include two somes frequency sources, one DDS, two frequency mixers and FPGA control circuit, wherein, the output in first frequency source couples DDS simultaneously And first frequency mixer, simultaneously as reference clock signal and the local oscillation signal of the first frequency mixer of DDS；Second The output in some frequency source couples the second frequency mixer, as the local oscillation signal of the second frequency mixer；DDS Yu FPGA is controlled Circuit processed is mutual, using the output signal within DDS as the clock signal of FPGA control circuit；First mixes Frequently device and the second frequency mixer are serially connected with the outfan of DDS, and the output signal of DDS is carried out secondary mixing.Excellent Selection of land, the output signal of DDS is filtered by two frequency mixers the most simultaneously.

In the embodiment shown in Figure 2, it is preferable that the initial signal in two some frequency sources is provided by same crystal oscillator, Thus reduce the impact between number of devices and signal further.Additionally, the output frequency in two some frequency sources also may be used Specified by FPGA control circuit；FPGA control circuit provides msk signal control code for DDS the most simultaneously.More Preferably, the output in first frequency source couples DDS and the first frequency mixer by a power splitter simultaneously.Additionally, The clock signal of FPGA control circuit is to be exported by 4 frequency dividers within DDS.

Only need to arrange reasonably some frequency source output frequency, embodiments of the invention can realize more than L-band frequency The MSK modulated signal output of rate, can be substantially improved the bit rate of output signal.With further reference to Fig. 3,4, It can be seen that the preferred embodiments of the present invention export the frequency of a more MSK modulated signal for standard in Fig. 3 Spectrogram, its mid frequency is 1090MHz, and the spike on both sides is respectively 1086MHz and 1094MHz, it is achieved The bit rate of 16Mb/s.It can be seen that the signal quality of this MSK modulated signal in Fig. 4, its EVM's is equal Root value is 2.3%, and frequency error is 345Hz.It can be seen that utilize the skill of the present invention from Fig. 3 and Fig. 4 The MSK modulating signal source that art scheme realizes, it is achieved that the high-quality MSK modulated signal of L-band, its code Speed has reached 16Mb/s.

Compared with prior art, the signal that same device produces is applied simultaneously to many by technical scheme Place so that system structure becomes simple, thus reduces module volume, reduces module cost, and realizes DDS and the synchronization of FPGA system clock, improve modulated signal quality.Technical scheme can Effectively realize the output of L-band frequencies above, and bit rate has reached 16Mb/s, be suitable for applying to various thunder Reach in system and communication system, and can be effectively used for secret communication.

Described above illustrate and describes some preferred embodiments of the present invention, but as previously mentioned, it should be understood that The present invention is not limited to form disclosed herein, is not to be taken as the eliminating to other embodiments, and can For other combinations various, amendment and environment, and can be in invention contemplated scope described herein, by upper State teaching or the technology of association area or knowledge is modified.And the change that those skilled in the art are carried out and change Without departing from the spirit and scope of the present invention, the most all should be in the protection domain of claims of the present invention.

Claims

1. a modulating signal source, it is characterised in that described modulating signal source includes: two somes frequency source, Individual DDS, two frequency mixers and FPGA control circuit, wherein,

Described DDS is mutual with described FPGA control circuit, using the output signal within described DDS as described The clock signal of FPGA control circuit, and described FPGA control circuit be described DDS provide msk signal control Code processed；

2. modulating signal source as claimed in claim 1, it is characterised in that the output signal of described DDS is MSK modulated signal.

3. modulating signal source as claimed in claim 1, it is characterised in that said two frequency mixer is also simultaneously The output signal of described DDS is filtered.

4. modulating signal source as claimed in claim 1, it is characterised in that said two point frequency source initial Signal end couples with same crystal oscillator.

5. modulating signal source as claimed in claim 1, it is characterised in that the output in said two point frequency source Frequency is specified by described FPGA control circuit.

6. modulating signal source as claimed in claim 1, it is characterised in that the output in described first frequency source Couple described DDS and described first frequency mixer by a power splitter simultaneously.

7. modulating signal source as claimed in claim 1, it is characterised in that described FPGA control circuit time Clock signal is to be exported by 4 frequency dividers within described DDS.

8. modulating signal source as claimed in claim 2, it is characterised in that signal frequency after described secondary mixing Rate is more than L-band.

9. modulating signal source as claimed in claim 2, it is characterised in that signal after described secondary mixing Bit rate is 16Mb/s.