The method for detecting isolation between antennas of digital radio repeater system
Technical field
The present invention relates to the digital radio repeater system design field, specifically be meant the method for detecting isolation between antennas of digital radio repeater system.
Background technology
Along with the professional rapid growth of mobile communication, there is active demand in operator to the lifting of brand effect separately, and the corresponding network quality requirement is also improving.Now each underground shelter, rural area, highway, railway, etc. construction project expansion just like a raging fire.Wireless discharging-directly station (comprising digital radio repeater and artificial antenna repeater) has unlimited potentiality as effectively extending network coverage means.As shown in Figure 1, general digital radio repeater system can (but being not limited only to) comprise: up link, down link; Described down link is connected to form successively by duplexer (301), low noise amplifier LNA (101), down conversion module (102), digital processing element (103), up-conversion module (104), descending amplifier AMP (105), duplexer (302); Described up link is connected to form successively by duplexer (302), low noise amplifier LNA (205), down conversion module (204), digital processing element (203), up-conversion module (202), upstream amplifier AMP (201), duplexer (301); Described duplexer (301) is connected with base station signal (501) by donor antenna (401), and duplexer (302) is connected with cellphone subscriber (502) by retransmitting antenna (402).And this invention realizes the detection of isolation between antennas in down link according to the downlink power and the metastable condition that gains thereof.
As shown in Figure 2, in digital radio repeater system, described digital processing element can comprise (but being not limited only to) A/D converter (1031), DDC Digital Down Convert passage (1032), digital filtering module (1033), FPGA (1034), DUC Digital Up Convert passage (1035), D/A converter (1036).Wherein the effect of A/D converter (1031) be with analog signal be transformed to digital signal, DDC Digital Down Convert passage (1032) to this digital signal be down-converted to digital baseband signal, digital filtering module (1033) carries out low-pass filtering to signal, FPGA (1034) handles baseband signal, signal is after DUC Digital Up Convert passage (1035) up-conversion, by D/A converter (1036) output analog signal then.
But in the process that wireless discharging-directly station is opened and moved, a key factor need considering when the isolation of antenna is system and project installation.If the isolation between donor antenna and the retransmitting antenna is less than the requirement (general wireless system requires: the isolation between donor antenna and the retransmitting antenna is than gaining greater than 15dB) of system, then can cause system signal distortion, power dissipation, decreased performance, can cause system's self-excitation when serious, cause the damage of equipment, the covering of the whole network of influence.In application of practical project, the influence that is subject to environment, weather and surrounding building owing to donor antenna and retransmitting antenna makes isolation produce certain variation, so the isolation of antenna detects and becomes particularly important in digital radio repeater.
Method for the wireless discharging-directly station isolation degree test, generally there are three kinds: as shown in Figure 3, a kind of is at donor antenna and the retransmitting antenna two ends respectively connect a signal source and a frequency spectrograph carries out the test of isolation between antennas, but this generally is when opening the station or the engineering staff makes in this way when on-the-spot, all be somewhat expensive and move inconvenient equipment, so this has brought some difficulties for the wireless discharging-directly station isolation degree test because of signal source and frequency spectrograph; Another kind method is to be with a signal source and a frequency spectrograph to test isolation in inside, repeater, the interference that this can increase the cost of equipment undoubtedly and cause signal; The third is to synthesize by radio frequency detection, signal, increase the detection that control circuit reaches isolation between antennas, but this method can increase cost, and the precision that detects is not high yet.
Summary of the invention
The objective of the invention is to overcome the shortcoming and defect of above-mentioned prior art, the method for detecting isolation between antennas of digital radio repeater system is provided, this method is utilized the principle of software radio, according to the downlink power of digital radio repeater and the metastable condition that gains thereof, in down link, realize the detection of isolation between antennas, system is workable, the monitoring accuracy height, need not increase any hardware cost.
Purpose of the present invention realizes by following proposal: the method for detecting isolation between antennas of this digital radio repeater system, and its step comprises:
(1) in down link digital processing element (103) lining, select an idle DDC passage to do and detect use, in bandwidth range, change the down-conversion frequency of this DDC passage from low to high;
(2) add up the digital power of this DDC passage, make an uproar the end of with and compare, if described digital power makes an uproar the end of near, be-80~-90dBm, just think that current frequency leaves unused, continue to seek idle frequency otherwise return step (1);
(3), use an idle DUC passage, the frequency of this DUC and this DDC passage correspondence in down link digital processing element (103) lining;
(4) the FPGA (1034) of down link digital processing element (103) produce one-20~-the point-frequency signal X of 30dBm, it is arrowband or direct current signal, the watt level of this point-frequency signal X is decided by the power of used repeater and the gain of system;
(5) the point-frequency signal X that produced of described FPGA (1034) carries out Digital Up Convert through DUC Digital Up Convert passage (1035), carries out D/A converter (1036) then digital signal is become analog if signal;
(6) analog if signal becomes the analog intermediate frequency letter and enters down link digital processing element (103) through descending up-conversion module (104), descending amplifier (105), duplexer (302), retransmitting antenna (402), donor antenna (401), duplexer (301), low noise amplifier (101), down conversion module (102);
(7) after analog if signal enters down link digital processing element (103), become digital medium-frequency signal through A/D converter (1031), become digital baseband signal Y through DDC Digital Down Convert passage (1032) then, Y=X+G-IL, wherein G is that system gain, IL are the isolation between donor antenna (401) and the retransmitting antenna (402), and the isolation of repeater is IL=G+X-Y just.
For realizing the present invention better, the specific implementation hardware of described down link digital processing element (103) and framework can have multiple, as FPGA, and CPLD, DSP etc.
Described above-mentioned idle DDC passage and idle DUC passage can be the fixing passages of using for test, also can be the idle channels when night, telephone traffic was few.
The standard of described digital radio repeater system can be GSM, CDMA, and WCDMA, or other mixes standard etc.
Described digital radio repeater can be that digital radio carrier wave repeater, digital radio broad band repeater, digital radio carrier wave frequency selecting repeater, digital radio frequency-shift repeater, digital radio self-excitation offset repeater and other digital radio repeaters.
The method for detecting isolation between antennas of this digital radio repeater system compared with prior art has the following advantages and beneficial effect:
(1) comparatively advanced software radio theory is adopted in the design of complete machine, and simplicity of design under the situation that does not increase hardware, can realize isolation degree test flexibly, can save cost to greatest extent;
(2) possess digital processing element, signal is carried out effective processing capacity at numeric field;
When (3) detecting isolation, utilize idle frequency range, can not influence the signal of normal communication;
(4) effectively avoided the artificial antenna repeater to come observation line isolation, greatly reduced the cost of equipment by increasing built-in signal source and frequency spectrograph.
The method of (4) utilization numeral is carried out the detection of isolation, has optimized detection means and has improved the precision that detects;
(5) this system not only is applicable to digital radio carrier wave repeater, also is applicable to the repeater in digital radio broadband simultaneously, and in other digital radio repeater.
Description of drawings
Fig. 1 is the structure principle chart of existing digital radio repeater system;
Fig. 2 is a down link baseband processing unit internal structure schematic diagram shown in Figure 1;
Fig. 3 is that existing simulation antenna isolating level of direct amplifying station with antenna detects schematic diagram;
Fig. 4 is the isolation between antennas testing process schematic diagram of digital radio repeater system of the present invention;
Embodiment
Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited thereto.
Embodiment one
As shown in Figure 1, adopt existing digital radio repeater system, direct discharging station is a wireless carrier frequency selecting repeater system, comprising: up link, down link; Described down link is connected to form successively by duplexer (301), low noise amplifier LNA (101), down conversion module (102), digital processing element (103), up-conversion module (104), descending amplifier AMP (105), duplexer (302); Described up link is connected to form successively by duplexer (302), low noise amplifier LNA (205), down conversion module (204), digital processing element (203), up-conversion module (202), upstream amplifier AMP (201), duplexer (301); Described duplexer (301) is connected with base station signal (501) by donor antenna (401), and duplexer (302) is connected with cellphone subscriber (502) by retransmitting antenna (402).
As shown in Figure 2, down link digital processing element (103) comprises A/D converter (1031), DDC Digital Down Convert passage (1032), digital filtering module (1033) (the main effect of described digital filtering module is outer spuious, the raising carrier wave selectivity of filtering band), FPGA (1034), DUC Digital Up Convert passage (1035), the D/A converter (1036) that connects successively.
As shown in Figure 4, it is such that this GSM digital radio repeater system carries out isolation between antennas testing process: in the down link digital processing element, select an idle DDC passage to do and detect use, in bandwidth range, change the down-conversion frequency of this DDC passage from low to high; Add up the digital power of this DDC passage, make an uproar the end of with and compare, if described digital power near the end make an uproar (be-80~-90dBm) just think that current frequency leaves unused; In the down link digital processing element, use an idle DUC passage, the frequency of this DUC and this DDC passage correspondence.
In down link digital processing element (103) lining, produce a suitable point-frequency signal X by FPGA (1034), it is arrowband or direct current signal, and the watt level of this point-frequency signal is decided by the power of used repeater and the gain of system, can be taken as-20~-30dBm; This signal X carries out Digital Up Convert through DUC (1035), by D/A converter (1036) digital signal is become analog if signal then, analog if signal becomes analog if signal and enters baseband processing unit (103) through descending up-conversion module (104), descending amplifier (105), duplexer (302), retransmitting antenna (402), donor antenna (401), duplexer (301), low noise amplifier (101), down conversion module (102).
After the analog intermediate frequency letter enters down link digital processing element (103), become digital medium-frequency signal through A/D converter (1031), become digital baseband signal Y (Y=X+G-IL, wherein G is that system gain, IL are the isolation between donor antenna and the retransmitting antenna) through DDC (1032) then.
The point-frequency signal X that this digital baseband signal Y and former FPGA produce compares and can draw: Δ=X-Y=X-(X+G-IL)=IL-G.According to system requirements: the isolation between donor antenna (401) and the retransmitting antenna (402) is than the big 15dB of gain, as long as so compare Δ 〉=15dB, then detecting system's isolation meets the demands, if compare Δ<15dB, then detecting system's isolation does not meet the demands, at this moment direct amplifying station monitoring sends the isolation alarm, or reduces system gain automatically, to satisfy system requirements.
Described down link digital processing element (103) adopts FPGA, CPLD, DSP etc.
Described above-mentioned idle DDC passage and (1032) idle DUC passages (1035) can be the fixing passages of using for test, also can be the idle channels when night, telephone traffic was few.
The standard of described digital radio repeater system can be GSM, CDMA, and WCDMA, or other mixes standard etc.
Described digital radio repeater can be that digital radio carrier wave repeater, digital radio broad band repeater, digital radio carrier wave frequency selecting repeater, digital radio frequency-shift repeater, digital radio self-excitation offset repeater and other digital radio repeaters.
Originally the introducing that has the GSM digital radio repeater system of isolation between antennas measuring ability can not cause bad influence to base station and this direct discharging station, because FPGA can seek idle frequency earlier automatically before producing point-frequency signal X, can not choose signal like this, when testing, can not produce and disturb useful signal in usefulness.
As mentioned above, just can realize the present invention preferably, the foregoing description is preferred embodiment of the present invention only, is not to be used for limiting practical range of the present invention; Be that all equalizations of doing according to content of the present invention change and modification, all contained by claim of the present invention scope required for protection.