CN201018504Y - Ground digital television repeater - Google Patents
Ground digital television repeater Download PDFInfo
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- CN201018504Y CN201018504Y CNU2007201190102U CN200720119010U CN201018504Y CN 201018504 Y CN201018504 Y CN 201018504Y CN U2007201190102 U CNU2007201190102 U CN U2007201190102U CN 200720119010 U CN200720119010 U CN 200720119010U CN 201018504 Y CN201018504 Y CN 201018504Y
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The utility model discloses a ground digital TV repeater, which comprises a low-noise amplifying module, a variable frequency module and a power amplifying module in sequence. Wherein, the low-noise amplifying module is composed of a preamplifier unit, an adjustable attenuator unit, a second-stage power amplifier unit, an automatic gain control unit and a time-delay unit in sequence. Wherein, a signal input terminal of the automatic gain control unit is connected with an output terminal of the second-stage amplifier unit. A control terminal of the automatic gain control unit is connected with an input terminal of the time-delay unit. An output terminal of the time-delay unit is connected with the other input terminal of the adjustable attenuator unit. The automatic gain control unit is designed and provided to properly adjust an output voltage according to intensity of signals output by the second-stage amplifier unit of the low-noise amplifying module, thus ensuring linear index of post stage circuit under various input powers and effectively control damages of post stage power amplifying modules arising from common frequency self-excitation.
Description
Technical field
The utility model relates to digital TV field, especially about a kind of ground digital television repeater.
Background technology
Ground digital television repeater is the network optimization product that designs for terrestrial digital television system.This ground digital television repeater strengthens by the signal that will receive, and through with frequently or change amplify frequently after emission again, the coverage after the forwarding reaches 0.5～5 kilometer, it is suitable for: a) suburbs, rural area, traffic covering along the line; B) covering in shadow region (for example mountain area); C) covering of environment such as heavy construction inside, parking lot, market place builet below the ground, subway system.
Digital television repeater is a kind of wireless relay multiplying arrangement, has played the effect that signal strengthens in the digital television transfer process.Digital television repeater is to enlarge the coverage of building digital TV network, a kind of cost-effective means that solve blind area and outlying district mobile communication.Digital television repeater mainly is divided into intra-frequency repeater and frequency-shift repeater by its transmission means.
See also Fig. 1, the groundwork principle of intra-frequency repeater (also crying with the frequency repeater station) is by donor antenna received signal from existing Digital Television overlay area, is transmitted into once more after processing such as filtering amplification and treats the overlay area.The main feature of intra-frequency repeater is: simple in structure and the signal forwarding time delay is little.
See also Fig. 2, frequency-shift repeater (also being the difference frequency repeater station) is similar substantially to the intra-frequency repeater principle, and difference is: the frequency of signal output has been moved to the frequency range of appointment.The main feature of this frequency-shift repeater is: simple in structure, the signal forwarding time delay is little, and the receiving and transmitting signal of different frequency makes that isolation is guaranteed and can not form self-excitation that engineering construction is the easiest.
But the linearity of existing intra-frequency repeater and frequency-shift repeater is all not high and can not effectively control self-excitation frequently together to the infringement of power amplifier module.
Summary of the invention
Technical problem to be solved by this invention is, overcomes the deficiencies in the prior art, provides a kind of and can have higher linearity and can effectively control with the ground digital television repeater of self-excitation frequently to the infringement of power amplifier module.
The technical solution adopted for the present invention to solve the technical problems is: this ground digital television repeater comprises the low noise amplification module that connects in turn, frequency-variable module and power amplifier module, this low noise amplification module comprises pre-amplifier unit, adjustable attenuator unit and second level amplifying unit, the input of this pre-amplifier unit receives the TV signal of wireless input, the input of its output termination adjustable attenuator unit, the input of the output termination second level amplifying unit of this adjustable attenuator, the output termination frequency-variable module of this second level amplifying unit, described low noise amplification module also comprises automatic gain control unit and delay unit, the signal input part of this automatic gain control unit connects the output of second level amplifying unit, the input of the control termination delay unit of this automatic gain control unit, the decay control end of the output termination adjustable attenuator unit of this delay unit, this automatic gain control unit detects the intensity of the output signal of second level amplifying unit, when this intensity surpassed preset value, the control voltage that this automatic gain control unit outputs to the adjustable attenuator unit reduced.
Described automatic gain control unit is the AD8314 chip.
Described power amplifier module comprises the ﹠amp that connects in turn; Gain control unit, RF pre-distortion unit and final stage power amplifier unit, this promotes ﹠amp; The output of the input termination frequency-variable module of gain control unit, this RF pre-distortion unit is the MAX2010 chip, this final stage power amplifier unit is made up of the MHL9236 power amplifier chip and the MRF9045 power amplifier chip of series connection.
Described frequency-variable module comprises first mixer unit, first order amplifying unit, intermediate frequency Surface Acoustic Wave Filter unit, second level amplifying unit, second mixer unit and the filter cell that connects in turn, the output signal of the second level amplifying unit of low noise amplification module and down-conversion local oscillation signal are input to first mixer unit and carry out mixing, the output signal of the second level amplifying unit of this frequency-variable module and up-conversion local oscillation signal output to second mixer unit and carry out mixing, the output termination power detection of this second amplifying unit; The input of control unit, this Gong Shuaijiance ﹠amp; The input of the output termination first order amplifying unit of control unit.
Described power amplifier module also comprises power, Wen Dujiance ﹠amp; Control unit, this power, Wen Dujiance ﹠amp; The output of the input termination RF pre-distortion unit of control unit, this power, temperature; The output termination of control unit promotes; Another input of gain control unit.
Be serially connected with the operational amplifier chip of the control voltage that is used to amplify automatic gain control unit output between the decay control end of the output of described delay unit and adjustable attenuator unit.
The invention has the beneficial effects as follows, by the design automatic gain control unit, and make its output signal strength adjust output voltage according to the second level amplifying unit of low noise amplification module in good time, thereby control the intensity of the output signal of this second level amplifying unit, so can guarantee the linear index of late-class circuit under various input power situations, and can effectively control with the infringement of self-excitation frequently to back level power amplifier module.
Description of drawings
Fig. 1 is the theory diagram of existing Digital Television intra-frequency repeater.
Fig. 2 is the theory diagram of existing Digital Television frequency-shift repeater.
Fig. 3 is the structured flowchart of the low noise amplification module of the utility model ground digital television repeater.
Fig. 4 is the structured flowchart of the frequency-variable module of the utility model ground digital television repeater.
Fig. 5 is the structured flowchart of the power amplifier module of the utility model ground digital television repeater.
Fig. 6 is the circuit theory diagrams of the low noise amplification module of the utility model ground digital television repeater.
Fig. 7 is the ﹠amp of the utility model ground digital television repeater; The circuit theory diagrams of gain control unit.
Fig. 8 is that the power amplifier module of the utility model ground digital television repeater (does not contain and promotes ﹠amp; Gain control unit) circuit theory diagrams.
Fig. 9 is the circuit theory diagrams of the RF pre-distortion unit of the utility model ground digital television repeater.
Embodiment
See also Fig. 3 to Fig. 9, vertical TV repeater, the utility model ground comprises that low noise amplifies (English abbreviates LNA as) module, frequency-variable module and power amplifier (English abbreviates PA as) module.
This low noise amplification module is used for receiving digital television signal and this signal is amplified in advance, and it comprises pre-amplifier unit 11, adjustable attenuator unit 12, second level amplifying unit 13, automatic gain control unit 15, delay unit 14 and the power subsystem 16 that whole module is powered.Digital television signal input pre-amplifier unit 11, one input of the output termination adjustable attenuator unit 12 of this pre-amplifier unit 11, the input of the output termination second level amplifying unit 13 of this adjustable attenuator unit 12, the signal input part of this automatic gain control unit 15 connects the output of second level amplifying unit 13, the input of the control termination delay unit 14 of this automatic gain control unit 15, the decay control end of the output termination adjustable attenuator unit 12 of this delay unit 14.Pre-amplifier unit 11 is used for that the TV signal of wireless input is carried out the first order and amplifies, this unit adopts the method for existing The low noise amplifier chip and Feedback Design, and lower noise factor (noise factor is less than 1.7dB) and smooth gain (gain flatness is less than 3dB in the 400MHz bandwidth range) are arranged in the scope of broadband (400MHZ).Adjustable attenuator unit 12 is used for the signal from pre-amplifier unit input is carried out automatic gain control, and it is as existing pin diode attenuator, (the 100MHz～3GHz) provide bigger attenuation range (30dB) in the scope in the broadband.Second level amplifying unit 13 adopts the power amplifier chip of high-gain (30dB), and it provides enough gains for whole low noise amplification module, and owing to be placed on the second level, so very little to the noise factor influence.Automatic gain control unit 15 is used to detect the intensity (being the power of signal) of second level amplifying unit 13 output signals and compares with preset value, just can control adjustable attenuator unit 12 above preset value and carry out power control.Automatic gain control unit 15 adopts the AD8314 chip (seeing U4 indication among Fig. 6) of ADI company, this chip U4 gathers voltage signal, it has detection and controls two kinds of use patterns, in the present embodiment, this chip adopts control model, under this control model, but magnitude of voltage of this chip U4 outer setting, represent a power points, when detecting input power (i.e. the power of the output signal of the second amplifying stage unit 13) when being higher than this power points, the control voltage that this chip U4 outputs to adjustable attenuator unit 12 reduces, input power is high more, the output voltage of this chip U4 is low more, thereby the power of the output signal of control second level amplifying unit 13 is in set point.This delay unit 14 as existing RC delay circuit 14, it has guaranteed also can the amplitude modulation phase-modulated signal of terrestrial DTV not to be exerted an influence when automatic gain control unit 15 is controlled, in the present embodiment, this RC delay circuit 14 is made up of the resistance of capacitor C 5 and chip U4 self.In addition, the output of this automatic gain control unit 15 also can meet operational amplifier chip U1 (seeing label 17 indications among Fig. 6), this chip U1 is used to amplify the control voltage of automatic gain control unit output, the control voltage signal of automatic gain control unit 15 outputs is input to this operational amplifier chip U1 after delaying time through delay unit 14, and this chip U1 will control the decay control end that is input to adjustable attenuator unit 12 after voltage signal amplifies.In the present embodiment, this low noise amplification module has adopted the The Wide-Band Design of reaction type, satisfies the bandwidth applications demand of terrestrial DTV from 470MHz to 860MHz, and in the 400MHz bandwidth, noise factor is less than 1.3dB, and gain flatness is less than 3dB.Because the utility model ground digital television repeater is a kind of with the frequency forwarding unit, so the situation of self-excitation may take place in the engineering of installing and using, automatic gain control unit 15 can effectively be controlled with the infringement of self-excitation frequently to back level power amplifier, and this automatic gain control unit 15 can guarantee the linear index of late-class circuit under various input power situations; Digital television signal is a kind of amplitude modulation phase-modulated signal, in the process of automatic gain control, if do not add delay unit 14, can influence the amplitude modulation information of Digital Television because the speed of FEEDBACK CONTROL is too fast, causes signal quality decline even can't play.
Frequency-variable module is used for the signal from the input of low noise amplification module is carried out frequency processing, and signal has better suppressed monkey chatter, thereby guaranteed to export to the spectral purity of power amplifier module after handling through intermediate frequency filtering.This frequency-variable module comprises first mixer unit, first order amplifying unit, intermediate frequency Surface Acoustic Wave Filter unit, second level amplifying unit, second mixer unit, filter cell and Gong Shuaijiance ﹠amp; Control unit, the output signal of the second level amplifying unit of low noise amplification module and down-conversion local oscillation signal are imported first mixer unit simultaneously and are carried out mixing, one input of the output termination first order amplifying unit of this first mixer unit, the input of the output termination intermediate frequency Surface Acoustic Wave Filter unit of this first order amplifying unit, the input of the output termination second level amplifying unit of this intermediate frequency Surface Acoustic Wave Filter unit, the output signal of this second level amplifying unit and up-conversion local oscillation signal are imported second mixer unit simultaneously and are carried out mixing, the output of this second mixer unit connects filter cell, this Gong Shuaijiance ﹠amp; The output of input termination second amplifying unit of control unit, this power detection; Another input of the output termination first order amplifying unit of control unit.From the signal of low noise amplification module input through the first mixer unit mixing, become the intermediate-freuqncy signal of 70MHz, be amplified into intermediate frequency Surface Acoustic Wave Filter unit through first order amplifying unit and carry out filtering, obtain clean 70MHz signal, amplify through second level amplifying unit again, the loss that compensation intermediate frequency sound watchband comes becomes original frequency output through second mixer unit again.In the present embodiment, by Gong Shuaijiance ﹠amp; Power root-mean-square value detection chip in the control unit accurately detects digital television signal intensity, decay chip controls signal strength signal intensity (this detection chip such as AA117-85 by software control, the user is provided with pad value in software, single-chip microcomputer receives this pad value, by controlling the high-low level values of five of this chip control pins, can obtain corresponding pad value), make full use of the input intensity of input signal, guarantee the linearity of back level signal, and to carry out second level protection with self-excitation frequently; Up-conversion local oscillation signal and down-conversion local oscillation signal are produced by existing voltage controlled oscillator (the English VCO of abbreviation), and this voltage controlled oscillator requirement phase noise is low and frequency stability is high.
Power amplifier module is used for signal is finally amplified, and sends into the antenna feeder emission at last.Ground digital television signal adopts the modulation system of OFDM+QPSK/16QAM/64QAM more, (the English PAR that is called for short) is higher for the peak-to-average force ratio of this class signal, and be the amplitude-phase modulation, linearity to power amplifier is had relatively high expectations, at such requirement, need in power amplifier module, adopt the radio frequency distortion technology.This power amplifier module is by power unit 31 power supplies, and it comprises promotion ﹠amp; Gain control unit, RF pre-distortion unit, final stage power amplifier unit 33 and power, Wen Dujiance ﹠amp; Control unit.This promotes ﹠amp; The output of the filter cell of the input termination frequency-variable module of gain control unit, this promotion; The input of the output termination RF pre-distortion unit of gain control unit, the input of the output termination final stage power amplifier unit of this RF pre-distortion unit, this power, temperature detection; The output of the input termination RF pre-distortion unit of control unit, its output termination promotes; Another input of gain control unit.The signal of frequency-variable module output is removed behind the local oscillation signal through promoting through filter; Gain control unit amplifies in advance, enters the RF pre-distortion unit then and carries out pre-distortion, enters final stage power amplifier unit 33 at last and carries out final amplification and last output.In the present embodiment, promote ﹠amp; Gain control unit is used for signal is carried out elementary amplification and control, and it comprises first order amplifier unit 21, PIN pipe attenuator unit 22 and the second level amplifier unit 23 that connects in turn, and the input of this first order amplifier unit 21 connects the filter of frequency-variable module
The output of ripple device unit.The RF pre-distortion unit is carried out pre-distortion by the predistortion chip to signal,The signal of output and the distortion of final stage power amplifier unit 33 generations can be balanced out, thereby produce high linear signal, the MAX2010 chip (seeing the chip IC 1 among Fig. 9) of this RF predistortion chip such as U.S. letter company, this chip IC 1 can change the AM/AM and the AM/PM characteristic of signal, end pin of this chip IC 1 (seeing the FromPrePA indication among Fig. 9) and promotion ﹠amp; The second level amplifier unit 23 of gain control unit connects.This final stage power amplifier unit 33 is that the power amplifier chip of MHL9236 and power amplifier chip that model is MRF9045 are formed by model, the end pin of chip IC 1 (seeing the ToFromPA among Fig. 9) and model are that the input of the power amplifier chip 332 of MHL9236 is connected, and the output of this power amplifier chip 332 and model are that the input of the power amplifier chip 331 of MRF9045 is connected.This power, Wen Dujiance ﹠amp; Output, reflected signal that control unit is used for whole power amplifier carry out power detection, be used to show power output and output standing-wave ratio, and be preset value by software control power output size, automatic gain control unit 15 in its control mechanism and the low noise amplification module is similar, reduces the input signal of power amplifier when the output standing-wave ratio is higher than warning value by the software control attenuation network.This power, Wen Dujiance ﹠amp; Control unit comprises Wen Dujiance ﹠amp; Control unit 34 and Gong Shuaijiance ﹠amp; Control unit 35, this Wen Dujiance ﹠amp; Control unit 34 is exported to single-chip microcomputer after then this magnitude of voltage being amplified by operational amplifier chip U6 and is handled by temperature detection chip U7 detected temperatures (the corresponding magnitude of voltage of this temperature).Gong Shuaijiance ﹠amp; The end pin RFout_coupler of control unit 35 connects the output coupled end of the output coupler of power amplifier module, detect the power output size by chip RFout_detector1 (AD8361 power detection chip), a magnitude of voltage Vout_UP is to single-chip microcomputer in this chip output, can obtain the power output size by software like this; RFre_coupler connects the coupled in reverse wi end of the output coupler of power amplifier module, by chip RFre_detector1 (AD8361 power detection chip) detection of reflected watt level, a magnitude of voltage Vre_UP is to single-chip microcomputer in this chip output, can obtain the reflection power size by software like this, and finally can utilize the size of computed in software output standing-wave ratio.The setting of the final stage power amplifier unit of forming by predistortion chip MAX2010 with by MHL9236 chip and MRF9045 chip 33, make when the ground digital television signal of output 5W power 16QAM modulation, output band shoulder is greater than 40dBc, compare the situation that does not adopt the MAX2010 chip, side channel power ratio (the English ACPR that is called for short) obtains the improvement of nearly 10dB.
The utility model ground digital television repeater has multistage automatic gain control (AGC) and self-excitation defencive function; both made full use of effective input signal (this input signal refers to the wireless digital TV-set signal of receiving from air interface); guarantee under the varying input signal field intensity; the equipment operate as normal has protected equipment can particularly not damage under the situation of self-excitation at excessive input signal again.
The utility model ground digital television repeater has the intermediate frequency Surface Acoustic Wave Filter, by the conversion intermediate frequency, after the filtering, the place that the channel-selective of equipment is better, antijamming capability is stronger, be more suitable for being applied in the spectrum environment complexity, and because the clutter of input final stage power amplifier still less, so output signal is linear better, carrier-to-noise ratio (C/N) height.
The power amplifier module of the utility model ground digital television repeater has the RF pre-distortion unit, effectively raises the linearity of power amplifier, has improved the efficient of whole repeater.
Above content be in conjunction with concrete preferred implementation to further describing that the utility model is done, can not assert that concrete enforcement of the present utility model is confined to these explanations.For the utility model person of an ordinary skill in the technical field, under the prerequisite that does not break away from the utility model design, can also make some simple deduction or replace, all should be considered as belonging to protection range of the present utility model.
Claims (6)
1. ground digital television repeater, comprise the low noise amplification module that connects in turn, frequency-variable module and power amplifier module, this low noise amplification module comprises pre-amplifier unit, adjustable attenuator unit and second level amplifying unit, the input of this pre-amplifier unit receives the TV signal of wireless input, the input of its output termination adjustable attenuator unit, the input of the output termination second level amplifying unit of this adjustable attenuator, the output termination frequency-variable module of this second level amplifying unit, it is characterized in that: described low noise amplification module also comprises automatic gain control unit and delay unit, the signal input part of this automatic gain control unit connects the output of second level amplifying unit, the input of the control termination delay unit of this automatic gain control unit, the decay control end of the output termination adjustable attenuator unit of this delay unit, this automatic gain control unit detects the intensity of the output signal of second level amplifying unit, when this intensity surpassed preset value, the control voltage that this automatic gain control unit outputs to the adjustable attenuator unit reduced.
2. according to the described ground digital television repeater of claim 1, it is characterized in that: described automatic gain control unit is the AD8314 chip.
3. according to claim 1 or 2 described ground digital television repeaters, it is characterized in that: described power amplifier module comprises the ﹠amp that connects in turn; Gain control unit, RF pre-distortion unit and final stage power amplifier unit, this promotes ﹠amp; The output of the input termination frequency-variable module of gain control unit, this RF pre-distortion unit is the MAX2010 chip, this final stage power amplifier unit is made up of the MHL9236 power amplifier chip and the MRF9045 power amplifier chip of series connection.
4. according to the described ground digital television repeater of claim 3, it is characterized in that: described frequency-variable module comprises first mixer unit that connects in turn, first order amplifying unit, intermediate frequency Surface Acoustic Wave Filter unit, second level amplifying unit, second mixer unit and filter cell, the output signal of the second level amplifying unit of low noise amplification module and down-conversion local oscillation signal are input to first mixer unit and carry out mixing, the output signal of the second level amplifying unit of this frequency-variable module and up-conversion local oscillation signal output to second mixer unit and carry out mixing, the output termination power detection of this second amplifying unit; The input of control unit, this Gong Shuaijiance ﹠amp; The input of the output termination first order amplifying unit of control unit.
5. according to the described ground digital television repeater of claim 3, it is characterized in that: described power amplifier module also comprises power, Wen Dujiance ﹠amp; Control unit, this power, Wen Dujiance ﹠amp; The output of the input termination RF pre-distortion unit of control unit, this power, temperature; The output termination of control unit promotes; Another input of gain control unit.
6. according to claim 1 or 2 described ground digital television repeaters, it is characterized in that: the operational amplifier chip that is serially connected with the control voltage that is used to amplify automatic gain control unit output between the decay control end of the output of described delay unit and adjustable attenuator unit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2007201190102U CN201018504Y (en) | 2007-03-16 | 2007-03-16 | Ground digital television repeater |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2007201190102U CN201018504Y (en) | 2007-03-16 | 2007-03-16 | Ground digital television repeater |
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| CN201018504Y true CN201018504Y (en) | 2008-02-06 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNU2007201190102U Expired - Lifetime CN201018504Y (en) | 2007-03-16 | 2007-03-16 | Ground digital television repeater |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100502490C (en) * | 2007-03-16 | 2009-06-17 | 深圳市银波达通信技术有限公司 | Ground digital television repeater |
| CN101841644A (en) * | 2010-04-14 | 2010-09-22 | 华亚微电子（上海）有限公司 | Adjacent channel interference elimination device and method |
| CN101527974B (en) * | 2009-04-10 | 2011-09-28 | 山东大学 | China mobile multimedia broadcasting (CMMB) repeater for optimizing urban CMMB network and control method thereof |
| CN105323022A (en) * | 2014-10-21 | 2016-02-10 | 航天恒星科技有限公司 | Device and method for continuously adjusting G/T value of system quality factor |
-
2007
- 2007-03-16 CN CNU2007201190102U patent/CN201018504Y/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100502490C (en) * | 2007-03-16 | 2009-06-17 | 深圳市银波达通信技术有限公司 | Ground digital television repeater |
| CN101527974B (en) * | 2009-04-10 | 2011-09-28 | 山东大学 | China mobile multimedia broadcasting (CMMB) repeater for optimizing urban CMMB network and control method thereof |
| CN101841644A (en) * | 2010-04-14 | 2010-09-22 | 华亚微电子（上海）有限公司 | Adjacent channel interference elimination device and method |
| CN105323022A (en) * | 2014-10-21 | 2016-02-10 | 航天恒星科技有限公司 | Device and method for continuously adjusting G/T value of system quality factor |
| CN105323022B (en) * | 2014-10-21 | 2019-03-12 | 航天恒星科技有限公司 | A kind of device and method that system quality factor G/T value is continuously adjustable |
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Effective date of abandoning: 20070316 |
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