CN101521518B - Broadband signal digital frequency-selective system based on software radio technology - Google Patents
Broadband signal digital frequency-selective system based on software radio technology Download PDFInfo
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Abstract
The invention provides a broadband signal digital frequency-selective system based on software radio technology, comprising an ADC subsystem, a digital intermediate frequency processing subsystem, an MCU control subsystem, and a D/A converter; the digital intermediate frequency processing subsystem is respectively connected with the ADC subsystem, the D/A converter and the MCU control subsystem; the MCU control subsystem is also respectively connected with the ADC subsystem and the D/A converter. The system not only can improve the out-off-band inhibition index, but also can improve the application performance of product, and also has low cost, thus having broad market prospect.
Description
Technical field
The present invention relates to wireless communication technology field, relate in particular to a kind of broadband signal digital frequency-selective system based on software and radio technique.
Background technology
At present; In the systems such as base station, base station sub-system, repeater and carrier dispatching of communication systems such as GSM, CDMA, TD-SCDMA, WCDMA; The general analogue technique that all adopts realizes the inhibition with outer unwanted signal is handled, to realize the frequency-selecting function to mobile communication signal.Shown in Figure 1 is in the present analog communication system, uses more a kind of signal frequency-selecting treatment technology, and it is connected to form by frequency mixer, amplifier, SAW filter (SAW), amplifier and frequency mixer successively.The Frequency mixing processing that the radiofrequency signal of input is at first passed through frequency mixer; The output analog if signal; Pass through amplifier again, offset the differential loss that Frequency mixing processing is introduced, realize Filtering Processing out of band signal through SAW filter; Filtered intermediate-freuqncy signal is passed through amplifier and frequency mixer again, the radiofrequency signal of output and input same frequency.Adopt this kind technology to carry out the frequency-selecting of signal, if exist being with outer spuious inhibition requirement very high, this kind frequency-selecting processing method does not often reach the shortcoming that good band suppresses index outward.At present; In order to overcome the shortcoming that the band that does not reach high request suppresses index outward; Usually the mode that adopts 2 local oscillation signal sources of employing shown in Figure 2 to carry out the multistage SAW filter level chain of Frequency mixing processing is carried out; But in the system of reality,, often can not adopt the SAW filter level chain more than 3 grades or 3 grades to handle because cost is too high and the product productibility is very poor.
In sum, present employed employing analogue technique carries out having more defective in the mode of frequency-selecting, is embodied in: the local oscillation signal poor stability that analogue device produces, and frequency of occurrences skew easily causes the input of system, output frequency to squint; The linear characteristic of analog multiplier is bad, and the phase place after the mixing can change, and differential loss needs amplifier offset, thereby introduces more active noise; The analog filter filtering characteristic is difficult to regulate and is difficult for changing with concrete demands of applications; The inconsistency of analog discrete components makes the amplitude of signal and the consistency of phase place be difficult to be guaranteed; Small product size is bigger, and weight is heavier, is difficult to realize miniaturization, lightness design; The analog hardware circuit of function singleness, very flexible is difficult to be fit to the wireless communication system of different communication system, multiband nowadays.
Development along with chip technology and signal processing technology; The conventional analogue technology is progressively replaced by digital processing technology; And the current communication system cycle of updating progressively shortens, and mobile communication equipment must can adapt to different communication system requirements, therefore; Press for the applicability that improves communication products, to satisfy the demand that communication system updates.
Summary of the invention
The objective of the invention is to overcome the shortcoming and defect of above-mentioned prior art; Provide a kind of and can improve the outer index that suppresses of band, can improve the broadband signal digital frequency-selective system based on software and radio technique (being called for short the wideband digital frequency-selecting system) of the applicable performance of product again.
The object of the invention is realized through following technical proposals: based on the broadband signal digital frequency-selective system of software and radio technique; Comprise ADC (analog-to-digital conversion) subsystem, Digital IF Processing subsystem, MCU (microprocessor) RACS and D/A converter; Described Digital IF Processing subsystem links to each other with ADC subsystem, D/A converter and MCU RACS respectively, and described MCU RACS also links to each other with ADC subsystem and D/A converter respectively.
Described ADC subsystem comprises A/D converter, AGC (Automatic Gain Control: automatic gain control) decision device and AGC controller; Described AGC decision device links to each other with A/D converter and AGC controller respectively; Described AGC controller links to each other with A/D converter, and described A/D converter also links to each other with described MCU RACS.
Described Digital IF Processing subsystem comprises DDC (Digital Down Convert) submodule, interface module, DUC (Digital Up Convert) submodule and gain controller; Described DDC submodule links to each other with interface module, DUC submodule and gain controller successively; Described DDC submodule also links to each other with described A/D converter; Described gain controller also links to each other with described D/A converter, and described DDC submodule, interface module, DUC submodule and gain controller link to each other with the MCU RACS respectively.
Described DDC submodule comprises frequency mixing module, NCO (digital controlled oscillator) generation module, DDC self-adaptive decision device, multiple variable extraction filter and base band formed filter; Two output output cos of described NCO generation module link to each other with an input of frequency mixing module respectively with the sin signal; Another input of frequency mixing module links to each other with the output of described A/D converter, and the output of frequency mixing module links to each other with DDC self-adaptive decision device, multiple variable extraction filter and base band formed filter successively.
Described DUC submodule comprises DUC self-adaptive decision device, the variable interpolation filter group of multiple and I, the multistage modulation module of Q signal; The output of described DUC self-adaptive decision device links to each other with the variable interpolation filter group of multiple and I, the multistage modulation module of Q signal successively, and the input of said DUC self-adaptive decision device links to each other with the output of described interface module.
The present invention compared with prior art has following advantage and beneficial effect:
(1) based on software and radio technique; Improve the reusability and the extensibility of product greatly, the objective demand that can satisfy current multiple communication system and deposit is keeping under the constant situation of hardware platform; Software in the upgrade-system can adapt to the demand of different application occasion;
(2) adopt digital if technology realize to digital medium-frequency signal extraction, interiorly insert, mixing and Filtering Processing; Abandoned the processing method of utilizing SAW filter SAW filtering in the simulation direct discharging station fully; Reduced the use of analogue device; Improve the consistency of systematic function, be convenient to system debug and production;
(3) method of employing digital filtering; It is very little that the passband fluctuation of filter can be done, and is with very high that outer inhibition can do, and improved the performance of signal filtering; The phase place of digital filter has good linear characteristic, has avoided the influence of the phase nonlinear of SAW to systematic function;
(4) native system has the AGC controlled function, improves the dynamic range of A/D work, has reduced the performance requirement to A/D simultaneously;
(5) utilize digital technology, digitized cos and sin signal are exported in the local oscillation signal source, and digital NCO can produce high-precision local oscillation signal, can effectively reduce frequency shift (FS);
(6) characteristic of the frequency of carrier wave and phase place, filter etc. is easy to adjust according to demands of applications, and amplitude, the phase equalization of output signal improve a lot;
(7) be easy to realize the miniaturization and the microminiaturization of wideband digital frequency-selecting system.
Description of drawings
Fig. 1 is a kind of simulation frequency-selecting Processing Structure sketch map that utilizes SAW filter commonly used at present;
Fig. 2 is the simulation frequency-selecting Processing Structure sketch map that adopts 2 grades of SAW filter level chains at present;
Fig. 3 is an overall structure sketch map of the present invention;
Fig. 4 is the DDC sub modular structure sketch map among the present invention;
Fig. 5 is the DUC sub modular structure sketch map among the present invention;
Fig. 6 is the application example of the present invention in digital radio repeater system.
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention is done to specify further, but execution mode of the present invention is not limited thereto.
As shown in Figure 3; Native system is made up of ADC subsystem, Digital IF Processing subsystem, MCU RACS and D/A converter; And the ADC subsystem links to each other with Digital IF Processing subsystem and D/A converter successively, and the MCU RACS then links to each other with ADC subsystem, Digital IF Processing subsystem and D/A converter respectively.
Can know that by Fig. 3 the ADC subsystem comprises A/D converter, AGC decision device and AGC controller.Wherein, A/D converter is one of Primary Component of native system, and it is used to receive the analog if signal of input, and this analog if signal is carried out analog-to-digital conversion process, the digital medium-frequency signal of output two-forty.Because Digital IF Processing subsystem having relatively high expectations to A/D converter; The A/D converter that generally needs high speed, wide dynamic range; Therefore; In order to reduce the requirement to front-end A/D transducer, this wideband digital frequency-selecting system has added AGC controller and AGC decision device, to improve the dynamic range of A/D.The output of said A/D converter is connected with the input of AGC decision device, and the output of AGC decision device is connected with the input of AGC controller, and the output of AGC controller links to each other with an input of A/D converter.A/D converter, AGC decision device and AGC controller form an AGC reponse system, to realize that the analog if signal that is input to A/D converter is carried out the AGC control and treatment.
AGC control and treatment flow process in the said ADC subsystem is following: the digital signal through behind the A/D converter is input in the AGC decision device; The AGC decision device is according to characteristics such as the amplitude of input signal, energy, power; Generate corresponding control information, be input to again in the AGC controller; The control information that the AGC controller provides according to the AGC decision device realizes amplification or attenuation processing to the front end analog if signal, promptly when the front end input signal amplitude excessive; Then carry out attenuation processing; Preventing that analog if signal from surpassing the maximum input level scope of A/D converter, and cause the blasting of quantification, when the front end input signal amplitude too small; For improving the receiving sensitivity of wideband digital frequency-selecting system, need carry out processing and amplifying to input signal.The AGC controller can increase the dynamic range of A/D converter when playing the protection A/D converter, improve the performance of wideband digital frequency-selecting system.
Described Digital IF Processing subsystem comprises DDC submodule, interface module, DUC submodule and gain controller.Wherein, interface module is mainly used in the switching to the system works clock zone of DDC submodule and DUC submodule, and functions such as the Gain Automatic adjusting of the transmission of realization DDC discriminative information and DDC and control.The input of described DDC submodule links to each other with the output of A/D converter; The output of DDC submodule links to each other with the input of interface module; The output of interface module links to each other with the input of DUC submodule; The output of DUC submodule links to each other with the input of gain controller, and the output of gain controller also links to each other with the input of D/A converter.Gain controller mainly is the gain through fine tuning DUC submodule, to satisfy the gain requirement of Digital IF Processing subsystem.
The configuration of the running parameter of the responsible whole wideband digital frequency-selecting of described MCU RACS system and the monitoring of control and digital frequency-selection system operating state.The output of MCU RACS links to each other with another input of A/D converter, DDC submodule, interface module, DUC submodule, gain controller and D/A converter respectively, to realize the control to A/D converter, DDC submodule, interface module, DUC submodule, gain controller and D/A converter.Be embodied in: the MCU subsystem is used to control index parameters such as the switching bandwith, switching rate, dateout figure place of A/D converter; Index parameters such as the switching bandwith of control D/A converter, switching rate, dateout figure place; Parameters such as the rate selection of control DDC submodule, DUC submodule, the selection of filter counting; Control the gain of whole Digital IF Processing subsystem etc.Described MCU subsystem also is used for each sub-module of wideband digital frequency-selecting system is monitored and alarming processing in real time through system bus, if a certain subsystem or operation irregularity appears in submodule, then carries out system reset and handles and carry out alarm report and handle.The MCU RACS also provides the program of whole system to download and upgrade, like the download of FPGA, DSP program etc.
D/A converter is the same with A/D converter also to be one of the key component of native system, and it is mainly used in the output signal of reception from the gain controller of Digital IF Processing subsystem, realizes the digital-to-analogue conversion of digital medium-frequency signal is handled the output analog if signal.D/A converter conversion accuracy and intermodulation index have very big influence to the performance of native system.So, need be according to the application demand of frequency-selective system, the corresponding index request of coupling system is reasonably selected corresponding D/A transducer.
(Free Space OpticalCommunication: digital direct discharging station such as repeater FSO) also goes for carrier tank dispatching patcher, digital RF far-drawing system and base station sub-system etc. applicable to wireless, optical fiber, FSO in this wideband digital frequency-selecting system.
As shown in Figure 4; The DDC submodule of Digital IF Processing subsystem mainly is digital medium-frequency signal to be carried out processing such as digital mixing, extraction and digital filtering; Realization is moved zero intermediate frequency to intermediate-freuqncy signal, the digital signal of two-forty is extracted the function of the baseband digital signal that is low rate.
Described DDC submodule comprises frequency mixing module, NCO generation module, DDC self-adaptive decision device, multiple variable extraction filter and base band formed filter.Two outputs of said NCO generation module are exported cos and sin signal; Link to each other with input of frequency mixing module respectively; Another input of frequency mixing module is connected with the output of A/D converter; The output of frequency mixing module links to each other with the input of DDC self-adaptive decision device, and the output of DDC self-adaptive decision device links to each other with the input of multiple variable extraction filter, and the output of described multiple variable extraction filter links to each other with the input of base band formed filter.
The DDC submodule is following to the Signal Processing flow process: the DDC submodule receives the digital medium-frequency signal from the output of A/D modular converter; Cos and sin signal that digital medium-frequency signal and NCO generation module produce are input in the frequency mixing module simultaneously, and output is through zero intermediate frequency I, Q signal after the Frequency mixing processing; Zero intermediate frequency I, the Q signal of frequency mixing module output are input in the DDC self-adaptive decision device; DDC self-adaptive decision device is according to the characteristic information of I, Q signal; Like information such as data speed, processing bandwidth, adaptive selection meets data pick-up multiple and the filter coefficient that speed, bandwidth etc. require; Multiple variable extraction filter receives from the output information of DDC self-adaptive decision device and I, Q signal, and according to the information that DDC self-adaptive decision device provides, carries out the extraction and the Filtering Processing of data, I, Q signal after output is handled through filtering extraction; The I of output, Q signal are with outside external compensation and the band at entering base band formed filter and are suppressed to handle, and generate baseband I, Q signal.
Described variable multiple decimation filter and base band formed filter can be the filter of FIR, IIR, CIC, HB filter or other form.
As shown in Figure 5; Processing such as the DUC submodule is inserted in being used to realize the baseband I, the Q signal that generate carried out, digital filtering and digital mixing; Be modulated to predetermined intermediate frequency to signal, with the digital signal interpolation of low rate for satisfying the digital signal of intermediate frequency Nyquist (Nyquist) sampling thheorem.Described DUC submodule comprises DUC self-adaptive decision device, the variable interpolation filter group of multiple and I, the multistage modulation module of Q signal.The output of said DUC self-adaptive decision device links to each other with the input of the variable interpolation filter group of multiple; The output of the variable interpolation filter group of multiple is connected with the input of I, the multistage modulation module of Q signal, and the input of described DUC self-adaptive decision device links to each other with the output of interface module.
The DUC submodule is following to signal processing flow: baseband I, Q signal through after the conversion of the data clock territory of interface module, the gain-adjusted, be input in the DUC self-adaptive decision device, and DUC self-adaptive decision device is according to characteristic informations such as the speed of baseband I, Q signal, bandwidth; And combine the digital intermediate frequency system to require the requirements such as data rate, bandwidth of output, adaptive selection meets the interpolation of data multiple that speed, bandwidth etc. require, and according to multiple confirm to select to insert in the one-level handle or multistage in slotting processing; And according to inserting treatment requirement in each level; Reasonably select the coefficient of interpolation filter etc., also promptly according to speed, the bandwidth of importing data, under the requirement of Nyquist (Nyquist) sampling thheorem; Select suitable interior slotting multiple; And, select the suitable filters coefficient, like the 28MHz bandwidth according to interior slotting multiple, data rate and clock frequency requirement; Baseband I, the Q signal of 65MSPS (million samples/sec); Be inserted into 130MSPS in needing, then need select the interior filter of inserting 2 times of one-level to realize that the parameter of filter is configured according to interior slotting multiple, data rate and clock frequency; The variable interpolation filter group of received of said multiple is from the output information of DUC self-adaptive decision device and I, Q signal; And the information that provides according to DUC self-adaptive decision device; Carry out the interior of data and insert and Filtering Processing, I, Q signal after output is handled through suitable interpolation filtering; I, Q signal after the interior slotting and Filtering Processing of the variable interpolation filter group of process multiple are input in I, the multistage modulation module of Q signal and go, through the multistage mixing and the modulation treatment of I, the multistage modulation module of Q signal, and digital intermediate frequency I, the Q signal of output high speed.
Wherein, the variable interpolation filter group of described multiple can be made up of one-level interpolation filter group, also can be made up of multistage interpolation filter group, generally speaking, only needs to use 1～2 grade of interpolation filter to get final product.I, the multistage modulation module of Q signal generally are made up of 1～2 grade of mixed modulated module, if in the follow-up DAC submodule, have the one-level mixed modulated and handle, and then I, the multistage modulation module of Q signal can omit the processing of one-level mixed modulated.Filter in the variable interpolation filter group of said multiple can be the filter of FIR, IIR, CIC, HB filter or other form.
Fig. 6 is the instance of this wideband digital frequency-selecting system applies in digital radio repeater.This digital radio repeater system comprises donor antenna, duplexer, radio-frequency transmitter subsystem, wideband digital frequency-selecting system, radio frequency sending set subsystem, retransmitting antenna, repeater power subsystem and monitoring repeater subsystem composition.Wherein, the wideband digital frequency-selecting system mainly realizes the digital frequency-selecting filter function to broadband signal, guarantees that digital radio repeater transmits needed signal, and the unwanted interference signal of good restraining.
Digital Signal Processing in the native system can utilize special-purpose ASIC to realize, also can utilize programmable logic devices such as DSP, FPGA, CPLD, EPLD to realize.Native system can application and the systems such as base station, base station sub-system, radio frequency stretch system, digital high-frequency amplification station and carrier dispatching of communication system such as GSM, CDMA, DCS, JDC, TD-SCDMA, WCDMA, CDMA2000.
As stated, just can realize the present invention preferably.
Claims (2)
1. based on the broadband signal digital frequency-selective system of software and radio technique; It is characterized in that; Comprise ADC subsystem, Digital IF Processing subsystem, MCU RACS and D/A converter; Described Digital IF Processing subsystem links to each other with ADC subsystem, D/A converter and MCU RACS respectively, and described MCU RACS also links to each other with ADC subsystem and D/A converter respectively;
Described Digital IF Processing subsystem comprises DDC submodule, interface module, DUC submodule and gain controller; Described DDC submodule links to each other with interface module, DUC submodule and gain controller successively; Described DDC submodule also with the ADC subsystem in A/D converter link to each other; Described gain controller also links to each other with D/A converter, and described DDC submodule, interface module, DUC submodule and gain controller link to each other with the MCU RACS respectively;
Described DDC submodule comprises frequency mixing module, NCO generation module, DDC self-adaptive decision device, multiple variable extraction filter and base band formed filter; Two outputs of described NCO generation module link to each other with an input of frequency mixing module respectively; The output of the A/D converter in another input of said frequency mixing module and the ADC subsystem is connected, and the output of said frequency mixing module links to each other with DDC self-adaptive decision device, multiple variable extraction filter and base band formed filter successively;
Described DUC submodule comprises DUC self-adaptive decision device, the variable interpolation filter group of multiple and I, the multistage modulation module of Q signal; The output of described DUC self-adaptive decision device links to each other with the variable interpolation filter group of multiple and I, the multistage modulation module of Q signal successively, and the input of said DUC self-adaptive decision device links to each other with the output of described interface module.
2. the broadband signal digital frequency-selective system based on software and radio technique according to claim 1; It is characterized in that; Described ADC subsystem comprises A/D converter, AGC decision device and AGC controller; Described AGC decision device links to each other with A/D converter and AGC controller respectively, and described AGC controller links to each other with A/D converter, and described A/D converter also links to each other with described MCU RACS.
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| CN2191437Y (en) * | 1994-03-25 | 1995-03-08 | 刘仁杰 | Computerized autocontrol frequency selective detector |
| CN200941617Y (en) * | 2005-12-19 | 2007-08-29 | 京信通信技术(广州)有限公司 | Mobile communicating directly releasing station system adopting digital IF way |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN2191437Y (en) * | 1994-03-25 | 1995-03-08 | 刘仁杰 | Computerized autocontrol frequency selective detector |
| CN200941617Y (en) * | 2005-12-19 | 2007-08-29 | 京信通信技术(广州)有限公司 | Mobile communicating directly releasing station system adopting digital IF way |
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| 罗敬.CDMA直放站无线选频系统的研究与实现.《中国优秀博硕士学位论文全文数据库(硕士)信息科技辑》.2007,第2、17-18页. * |
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