CN101958734A - Integrated wireless coverage solution - Google Patents
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- CN101958734A CN101958734A CN2010105116805A CN201010511680A CN101958734A CN 101958734 A CN101958734 A CN 101958734A CN 2010105116805 A CN2010105116805 A CN 2010105116805A CN 201010511680 A CN201010511680 A CN 201010511680A CN 101958734 A CN101958734 A CN 101958734A
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Abstract
The invention discloses an integrated wireless coverage solution which is used for realizing signal relay and eliminating Doppler frequency offset caused by high-speed operation in a signal. The solution comprises the following steps: a Doppler frequency offset tracking unit is added for obtaining a frequency error function between a downlink pilot signal contained in a downlink intermediate-frequency signal and a reference signal, and the function value is maintained at zero by adjusting the frequency of the signal generated by a controlled frequency source so as to control the downlink tracking signal generated by the controlled frequency source; the downlink tracking signal is mixed with the downlink signal via a lower variable frequency channel of a down link to eliminate forward Doppler frequency offset; and an uplink tracking signal, namely a backward Doppler frequency offset signal of the downlink tracking signal is mixed with an uplink signal via an upper variable frequency channel of an uplink to preset backward Doppler frequency offset. The solution of the invention can help effectively eliminate the Doppler frequency offset in communication between a mobile station in a high-speed motion carrier and a base station or a remote radio unit, thus playing a role in ensuring communication quality.
Description
[technical field]
The present invention relates to the wireless network coverage optimization field of mobile communication, relate in particular to a kind of no Doppler frequency shift relay and corresponding relay method, and then a kind of bullet train wireless shrouding system, scheme are proposed, to be applicable to the mobile communication application on the high-speed mobile carrier.
[technical background]
In the high-speed railway mobile communication environment, if adopt the base station that wireless coverage is directly carried out in the railway zone, for fear of frequent handover, the covering radius of each base station need reach more than ten kilometers, for the railway zone of wire, the efficient of the direct coverage mode in this base station is very low.In order to improve covering efficient, the mode that can adopt the base station to add Remote Radio Unit realizes wireless coverage.A base station can dispose a plurality of Remote Radio Unit, and is in one line along railway.Therefore for the covering radius of base station, the covering radius of each Remote Radio Unit is all little, can be easy to realize the effective covering to the wire railway zone more than ten kilometers.
Since a base station configuration a plurality of Remote Radio Unit, therefore in the overlapping area of coverage of two Remote Radio Unit, the travelling carriage in the railway car will be received the same signal of base station that sends from two different directions Remote Radio Unit.If travelling carriage can't be distinguished the signal of this both direction,, communication quality is seriously descended just these two signals have constituted artificial multipath interference each other so.(annotate: in the high-speed railway mobile communication environment that adds the Remote Radio Unit covering with the base station, signal has very strong direct path between from the Remote Radio Unit to the train, therefore natural multipath disturbs much more weak than artificial multipath interference, so consider mainly that here artificial multipath disturbs.)
Suppose that travelling carriage can distinguish the artificial multipath signal of this both direction, the method that so just can use rake to merge is utilized these signals.Because under the environment of high-speed mobile, the signal of this both direction has all been introduced very big Doppler frequency shift, and the direction of frequency displacement is opposite, therefore before merging, need to eliminate respectively this both direction signal Doppler frequency shift separately.
In sum, in order to improve the quality of communicating by letter in the high-speed railway mobile communication environment, need solve following problem effectively, that is:
1, distinguishes the signal of different directions.
2, eliminate different directions signal Doppler frequency shift separately.
3, merge the signal of different directions, disturb thereby eliminate artificial multipath.
In order to eliminate Doppler frequency shift, improve the communication quality between the travelling carriage and fixed base stations or Remote Radio Unit in the high-speed mobile vehicles, have the following mode can be for reference:
The first is introduced the Doppler frequency shift calibration function in the base station, in this mode, therefore the base station demand side need be followed the tracks of respectively and offset the travelling carriage of a plurality of different moving directions and rate travel at the direction and the size of different mobile stations Doppler frequency shift, implements comparatively complicated;
It two is to introduce the Doppler frequency shift calibration function in travelling carriage, consider the factor such as cost, volume, power consumption, heat radiation of travelling carriage, thereby and place the high-speed mobile vehicles to be influenced effect correction precision etc. when travelling carriage by vehicles shielding action, so its feasibility is not high relatively;
Moreover, as the basis that the present invention is suggested, can on the vehicles, place a repeater as relay, the signal of fixed base stations or Remote Radio Unit is directly put the back vehicle interior is covered.At this moment, repeater static or low speed for the travelling carriage of vehicle interior moves, but but is high-speed mobile for base station or Remote Radio Unit.
The fundamental difference of this mobile repeater and traditional fixedly repeater just is that mobile repeater need possess the function of distinguishing signal, eliminating Doppler frequency shift and combined signal, for communicating by letter between the travelling carriage in fixed base stations or Remote Radio Unit and the high-speed mobile vehicles provides the wireless coverage of no Doppler frequency shift environment.Wherein eliminating the realization of Doppler frequency shift function, is emphasis of the present invention place.
[summary of the invention]
Echo mutually with aforementioned, primary and foremost purpose of the present invention will provide a kind of no Doppler frequency shift relay exactly, make by its signal of equipment room of realizing the two ends of relaying and can remove because of the Doppler frequency shift factor that high-speed mobile or other reason produced the proper communication quality of assurance signal.
Another object of the present invention is to provide a kind of no Doppler frequency shift trunking method, in the signal path of intercommunication mutually, remove Doppler frequency shift, ensure communication quality because of high-speed mobile or the caused signal of other reason.
A further object of the present invention is to provide a kind of bullet train wireless shrouding system, makes the signal between the outer mobile communications network of interior travelling carriage of bullet train and car realize no Doppler frequency shift transmission, guarantees the communication quality of travelling carriage.
A further object of the present invention is to provide a kind of bullet train wireless coverage scheme, to scheme to be suitable for the needs of high ferro development.
Last purpose of the present invention is to provide a kind of doppler frequency shift tracking unit, to realize the versatility of product of the present invention, is convenient to standardized production, installation and maintenance.
For realizing this purpose, the present invention adopts following technical scheme:
A kind of doppler frequency shift tracking of the present invention unit is used to follow the tracks of the Doppler frequency skew of the signal that causes because of high-speed motion of relay, and this tracking cell comprises:
Coupler is used for being coupled out one road downstream signal at the radio-frequency front-end of relay down link;
The controlled frequency source produces the descending tracking signal that comprises the descending forward Doppler frequency shift factor under the control of correcting unit;
The down-conversion passage, the frequency of the descending tracking signal that produces with the controlled frequency source is a benchmark, and downstream signal is carried out down-conversion;
Reference unit is used to produce a reference signal for the correcting unit reference;
Correcting unit is used to ask for down-bound pilot frequency signal that downstream signal comprised after the down-conversion and the frequency error function between the described reference signal, and the frequency of regulating the descending tracking signal that the controlled frequency source produces makes this functional value be maintained zero;
Converter unit is transformed to this descending tracking signal the up tracking signal that comprises the up reverse Doppler frequency shift factor.
Disclose according to one embodiment of the invention, described reference unit comprises frequency multiplier and the intrinsic reference frequency source of relay, and the signal that reference frequency source produces becomes described reference signal after the frequency multiplier frequency multiplication.
Disclose according to another embodiment of the present invention, described reference unit comprises frequency multiplier and described controlled frequency source, and the descending tracking signal that the controlled frequency source produces becomes described reference signal after the frequency multiplier frequency multiplication.
Be operated in analog domain or numeric field corresponding to correcting unit, described controlled frequency source is VCXO (VCXO) or numerically-controlled oscillator (NCO).
Be connected in series a frequency multiplier between described controlled frequency source and the down-conversion passage the descending tracking signal that the controlled frequency source produces is carried out the frequency multiplication computing.
This tracking cell also comprises filter, and it is serially connected with between down-conversion passage and the correcting unit, and the downstream signal after the down-conversion is carried out being transferred to described correcting unit after the filtering.
Described converter unit comprises:
Frequency multiplier is used for the signal that the existing reference frequency source of relay produces is carried out the frequency multiplication computing of preset multiple;
Frequency mixer produces described up tracking signal thereby utilize the operation result of this frequency multiplier and descending tracking signal to carry out mixing;
Filter is used for described up tracking signal is carried out exporting after the filtering.
A kind of no Doppler frequency shift relay of the present invention, the Doppler frequency that is used to realize signal relay and eliminate the signal that causes because of high-speed motion is offset, and it comprises down link and up link, also comprises:
Aforesaid doppler frequency shift tracking unit;
Down-conversion passage in the down link, the descending tracking signal of exporting with this tracking cell is that local oscillator is carried out mixing to eliminate the forward Doppler frequency shift in the downstream signal to the downstream signal in the down link;
Up-conversion passage in the up link, the up tracking signal of exporting with this tracking cell is that local oscillator is carried out mixing to preset reverse Doppler frequency shift in upward signal to the upward signal in the up link.
This device comprises donor antenna and be used for and base station or the wireless electric connection of Remote Radio Unit by main antenna, donor antenna, be used for and the wireless electric connection of travelling carriage by main antenna.Described donor antenna adopts omnidirectional or directional antenna, the described leaky cable that is subjected to main antenna to adopt the one lengthwise.
Described reference frequency source adopts stability to be better than ± crystal oscillator of 0.01ppm.
A kind of no Doppler frequency shift trunking method of the present invention is used for realizing that signal relay and erasure signal are offset because of the Doppler frequency that high-speed motion causes, it comprises the steps:
1) from the down link radio-frequency front-end, is coupled out one road downstream signal;
2) produce line trace signal;
3) following line trace signal is that benchmark downconverts to intermediate frequency or zero intermediate frequency territory with this radio frequency downstream signal;
4) ask for down-bound pilot frequency signal and frequency error function that supplies between the reference signal of reference that this intermediate frequency or zero intermediate frequency territory downstream signal are comprised, and regulating step 3) the middle frequency that produces descending tracking signal, so that this functional value is maintained zero;
5), be that local oscillator is carried out mixing to eliminate the forward Doppler frequency shift in the downstream signal to downstream signal with this descending tracking signal for down link;
6) for up link, earlier this descending tracking signal is transformed to the up tracking signal that presets reverse Doppler frequency shift, be that local oscillator is carried out up-conversion to upward signal with this up tracking signal again, in upward signal, to preset reverse Doppler frequency shift.
Disclose according to one embodiment of the invention, the reference signal in the described step 4) is obtained after the frequency multiplication computing by the signal that a reference frequency source produces.
Disclose according to another embodiment of the present invention, the reference signal in the described step 4) is by described step 2) descending tracking signal after the frequency multiplication computing, obtain.
Step 4) is if adopt analog form to carry out, and described descending tracking signal is produced by a controlled VCXO (VCXO), if adopt digital form to carry out, then produces (NCO) by numerically-controlled oscillator.
Descending tracking signal in the described step 3) has been passed through the frequency multiplication computing.
Frequency domain in the described step 4) or zero intermediate frequency territory downstream signal have passed through filtering.
In the step 6), filtering after the frequency multiplication operation result mixing of the signal that described up tracking signal is produced by described descending tracking signal and a reference frequency source and getting.
A kind of bullet train wireless shrouding system of the present invention, it adopts aforesaid no Doppler frequency shift relay, and its donor antenna is placed on the bullet train top, and it is laid along the compartment one lengthwise of bullet train by main antenna.
A kind of bullet train wireless coverage scheme of the present invention is applicable to the train of relative radio repeater station high-speed mobile, and it comprises the steps:
1) on bullet train, installs the repeater, and base station or Remote Radio Unit signal that this repeater receives only a direction at any time are set, ignore the signal of other direction;
2) down link for this repeater provides the descending tracking signal that can follow the tracks of the forward Doppler frequency shift, for the up link of this repeater provides the up tracking signal that has preset reverse Doppler frequency shift.
3) descending tracking signal is used for the down-conversion passage and the up-conversion passage of this repeater down link, eliminates the Doppler frequency shift that relatively moves and in downstream signal, introduce because of train, so that travelling carriage receives the downstream signal of no Doppler frequency shift in the train;
4) up tracking signal is used for the down-conversion passage and the up-conversion passage of the up link of this repeater, in upward signal, presets reverse Doppler frequency shift, so that radio repeater station receives the upward signal of no Doppler frequency shift.
Compared with prior art, because the present invention has realized the Doppler frequency shift calibration function on relay, be applicable to the repeater such as frequency-selecting, shift frequency, wideband, to radio repeater stations such as base station or Remote Radio Unit and travelling carriage without any influence, therefore can directly apply in any existing and mobile communications network that plan is built, also be that it has higher portability and application feasibility.Conventional art is eliminated the technology of Doppler frequency shift in base station and Remote Radio Unit or travelling carriage relatively, and it has tangible progressive, is in particular in:
One, introducing Doppler frequency shift calibration function is compared with this function of introducing in base station (or Remote Radio Unit) and is mainly contained following advantage in relay:
1, therefore the base station demand side need be followed the tracks of respectively and offset the travelling carriage of a plurality of different moving directions and rate travel at the direction and the size of different mobile stations Doppler frequency shift, implements complexity; And relay (mobile repeater) only needs base station or Remote Radio Unit in the face of a direction, therefore only needs to follow the tracks of and offset the Doppler frequency shift of a direction and size, implements simple;
2, relay (mobile repeater) can make full use of the correction that down-bound pilot frequency signal is carried out Doppler frequency shift; And in the base station,, then can't accomplish this point if do not have pilot signal in the upward signal, cause technology to realize the birth defects that can't overcome.
Its two, in relay (mobile repeater), introduce the Doppler frequency shift calibration function and in travelling carriage, introduce this function and compare that then advantage is more obvious:
1, travelling carriage has harsh requirement to cost, volume and power consumption, and is much then loose for mobile repeater.Mobile repeater is equivalent to for all travelling carriages in the vehicles provide a public radio-frequency front-end, the Doppler frequency shift calibration function of each travelling carriage is focused in the mobile repeater realizes, than be dispersed in realize in each travelling carriage more reasonable;
2, mobile repeater can use the directed tracing antenna (mainly being meant its donor antenna) that places outside the vehicles and the reference frequency source of high stability, eliminates the shielding action of the vehicles, improves the precision that Doppler frequency shift is proofreaied and correct; And in travelling carriage, these all are difficult to realize.
[description of drawings]
Fig. 1 is that the present invention does not have Doppler frequency shift relay application scenarios schematic diagram.
Fig. 2 is the theory diagram of no Doppler frequency shift relay in the first embodiment of the invention, and this embodiment is applicable to the intermediate frequency scheme.
Fig. 3 is the theory diagram of doppler frequency shift tracking unit in the first embodiment of the invention.
Fig. 4 is the theory diagram of no Doppler frequency shift relay in the second embodiment of the invention, and this embodiment is applicable to the zero intermediate frequency scheme.
Fig. 5 is the theory diagram of doppler frequency shift tracking unit in the second embodiment of the invention.
Fig. 6 is the theory diagram of no Doppler frequency shift relay in the third embodiment of the invention, and its intermediate frequency scheme by first embodiment derives a unified intermediate frequency scheme.
Fig. 7 is the theory diagram of no Doppler frequency shift relay in the fourth embodiment of the invention, and its zero intermediate frequency scheme by second embodiment derives a unified zero intermediate frequency scheme.
[embodiment]
The present invention is further illustrated below in conjunction with drawings and Examples:
As a comprehensive bullet train wireless coverage scheme, the application scenarios that its concrete application is a bullet train wireless shrouding system of the present invention as shown in Figure 1.On the carrier of high-speed mobile (vehicles with train of high-speed railway and so on are example) 101,111,112, two mobile repeaters 111,112 of two mobile repeaters are installed are realized by the present invention's no Doppler frequency shift relay described later.Each mobile repeater respectively has one to possess the donor antenna of directed tracing ability or share omnidirectional's donor antenna, receive the signal of former and later two nearest base stations or Remote Radio Unit 122,121 respectively, realize communicating by letter with base station or the wireless electric connection of Remote Radio Unit.Two mobile repeaters are subjected to main antenna (i.e. the antenna of communicating by letter with the wireless electric connection realization of travelling carriage) by shared one of mixer (not shown), and this is subjected to main antenna to adopt one to cover the leaky cable that carrier inside is promptly laid along railway car longitudinally one lengthwise.
No matter adopting directed tracing still is omnidirectional's donor antenna, will guarantee that all each mobile repeater can only receive the base station or the Remote Radio Unit signal of a direction in former and later two directions of train, and the signal of other direction is little of ignoring.The former is used for guaranteeing that the latter guarantees by frequency division, time-division or code division multiplexing by spatial division multiplexing.Therefore can be similar to and think that each mobile repeater only introduced the Doppler frequency shift of a direction, in a single day each mobile repeater has eliminated Doppler frequency shift, and the wireless coverage environment on the bullet train promptly is considered as not having the wireless coverage environment of Doppler frequency shift.
As previously mentioned, mobile repeater comprises frequency selecting repeater, frequency-shift repeater and wideband repeater etc., adopts no Doppler frequency shift relay of the present invention to realize.This relay is used to realize signal relay, and eliminate by the Doppler frequency shift of the signal of relaying, the key of eliminating Doppler frequency shift is to follow the tracks of the Doppler frequency shift factor, the process of following the tracks of the Doppler frequency shift factor realizes by a doppler frequency shift tracking unit, two kinds of implementations are arranged, and the first is followed the tracks of the frequency domain downstream signal, claims the intermediate frequency scheme, another then is that zero intermediate frequency territory downstream signal is followed the tracks of, and claims the zero intermediate frequency scheme.Among the present invention, two kinds of schemes are specifically described with first and second embodiment respectively.
Below with common first embodiment that discloses employing intermediate frequency scheme of the present invention of Fig. 2 and Fig. 3.
The no Doppler frequency shift relay of first embodiment of the invention is by donor antenna 201, be subjected to main antenna 202, duplexer 211,212, amplifier 221,222,223,224,225,226,227,228, frequency mixer 231,232,233,234, if bandpas filter 241,242, frequency multiplier 251,252,253,254, reference frequency source 261, doppler frequency shift tracking unit 271, and coupler 281 constitutes.Wherein, amplifier 221, frequency mixer 231, amplifier 222 constitute the descending down-conversion passage of mobile repeater; Amplifier 225, frequency mixer 233, amplifier 226 constitute the descending up-conversion passage of mobile repeater.Descending down-conversion passage, if bandpas filter 241, descending up-conversion passage constitute the down link of mobile repeater together.Amplifier 228, frequency mixer 234, amplifier 227 constitute the up down-conversion passage of mobile repeater; Amplifier 224, frequency mixer 232, amplifier 223 constitute the up up-conversion passage of mobile repeater.Up down-conversion passage, if bandpas filter 242, up up-conversion passage constitute the up link of mobile repeater together.Coupler 281, doppler frequency shift tracking unit 271, reference frequency source 261, frequency multiplier 251,252,253,254 constitute the frequency synthesizer of mobile repeater, are called for short synthetizer.Wherein, doppler frequency shift tracking unit 271 has the doppler frequency shift tracking ability, for descending down-conversion passage and up up-conversion passage provide the local frequency source; And reference frequency source 261 served as by the crystal oscillator of high stability (for example stability is better than ± the constant-temperature crystal oscillator TCXO of 0.01ppm), for descending up-conversion passage and up down-conversion passage provide the local frequency source.
After donor antenna 201 and duplexer 211, deliver to descending down-conversion passage from the downlink radio-frequency signal of base station or Remote Radio Unit and carry out down-conversion.Down-conversion adopts low local oscillator lower sideband scheme, and the descending intermediate-freuqncy signal that obtains is delivered to descending up-conversion passage and carried out up-conversion after if bandpas filter 241.Up-conversion is used low local oscillator upper sideband scheme, and the downlink radio-frequency signal that obtains is through duplexer 212 and be subjected to main antenna 202 to send to travelling carriage in the compartment.
Stand to deliver to up down-conversion passage after main antenna 202 and the duplexer 212 from the up radiofrequency signal of travelling carriage in the compartment and carry out down-conversion, down-conversion adopts low local oscillator lower sideband scheme, and the up intermediate-freuqncy signal that obtains is delivered to up up-conversion passage and carried out up-conversion after if bandpas filter 242.Up-conversion adopts low local oscillator upper sideband scheme, and the up radiofrequency signal that obtains sends to base station or Remote Radio Unit after duplexer 211 and donor antenna 201.
The signal that the doppler frequency shift tracking unit 271 of present embodiment adopts 261 generations of local reference frequency source is directly as the reference signal of inner automatic frequency correction unit, and its theory diagram as shown in Figure 3.The controlled frequency source 461 that doppler frequency shift tracking unit 271 is served as by amplifier 421,422, frequency mixer 431,432, if bandpas filter 441,442, automatic frequency correction (AFC) unit (calling correcting unit in the following text) 471, use VCXO (VCXO), frequency multiplier 451,452,453 constitute.It should be noted that, amplifier 421 wherein, 422 have constituted the down-conversion passage with frequency mixer 431, and coupler 281 can downconvert to frequency domain with the downstream signal of radio frequency domains with this down-conversion passage and this if bandpas filter 441, uses thereby offer described correcting unit 471.Described frequency multiplier 453, frequency mixer 432 and 442 in filter have constituted converter unit jointly, are used for the direction of the Doppler frequency shift factor of figure signal.
There are two input signals and two output signals in doppler frequency shift tracking unit 271.Two input signals are respectively the downlink radio-frequency signals that contains down-bound pilot frequency signal that obtain by coupler 281 couplings from the down link radio-frequency front-end and are f by the frequency that reference frequency source 261 provides
0Reference frequency signal; Two output signals are respectively that the frequency that can follow the tracks of descending forward Doppler frequency shift is f '
0Descending tracking signal and the frequency that has preset up reverse Doppler frequency shift be f "
0Up tracking signal, up tracking signal and descending tracking signal all stem from this controlled frequency source 461, wherein up tracking signal is the signal of original tracking signal after the converter unit conversion.
In doppler frequency shift tracking unit 271, it is descending tracking signals that controlled frequency source (VCXO) 461 is subjected to the signal of correcting unit 471 control outputs, its frequency f '
0Be subjected to the control of the control signal of automatic frequency correction unit 471 generations.One road input signal of automatic frequency correction unit 471 is the intermediate frequency pilot signal that obtains after the frequency-doubled signal mixing, filtering of the signal of down-bound pilot frequency signal and controlled frequency source (VCXO) 461 outputs; Another road input signal of automatic frequency correction unit 471 is that reference signal is the frequency-doubled signal of reference frequency source signal.The function of automatic frequency correction unit 471 is exactly to detect the existence of down-bound pilot frequency signal, and under the situation that down-bound pilot frequency signal exists, calculate the frequency error function between down-bound pilot frequency signal (through frequency conversion) and the local reference frequency signal (through frequency multiplication), produce control signal corresponding and regulate the output frequency in controlled frequency source (VCXO) 461, keeping the said frequencies error is zero.
In converter unit, descending tracking signal is carried out mixing with 2 frequency-doubled signals of local reference frequency source signal again, and getting and obtaining frequency after the latter and the former the difference frequency signal filtering is f "
0=2f
0-f '
0Up tracking signal.
In conjunction with Fig. 2 and Fig. 3, the standard frequency of setting capable radiofrequency signal carrier wave is f
d, the standard frequency of up radiofrequency signal carrier wave is f
u, the standard frequency of down-bound pilot frequency signal is f
p, the standard frequency of descending intermediate-freuqncy signal carrier wave is f
Id, the standard frequency of up intermediate-freuqncy signal carrier wave is f
Iu, the standard frequency of descending intermediate frequency pilot signal is f
IpMake x=f
d/ f
0, y=f
u/ f
0, z=f
p/ f
0, w=f
Id/ f
d=f
Iu/ f
u=f
Ip/ f
pThe multiplier parameter of getting frequency multiplier 251,253 is d=d '=x (1-w), the multiplier parameter of frequency multiplier 252,254 is u=u '=y (1-w), the multiplier parameter of frequency multiplier 451 is p=z (1-w), and the multiplier parameter of frequency multiplier 452 is q=zw, and the multiplier parameter of frequency multiplier 453 is 2.
The frequency of the down-bound pilot frequency signal that mobile repeater is received is f
p+ Δ f
p, Δ f wherein
pBe its Doppler frequency shift.This signal and frequency are f '
0The frequency-doubled signal pf ' of descending tracking signal
0Obtaining frequency after mixing, the filtering is f '
Ip=f
p+ Δ f
p-pf '
0The intermediate frequency pilot signal.Automatic frequency correction unit 471 calculates the intermediate frequency pilot signal and frequency is f
Ip=qf
0The frequency-doubled signal of reference frequency source signal between the frequency error function, and control controlled frequency source 461 according to this, serve as zero to keep frequency error, i.e. f '
Ip-f
Ip=0.Therefore, when automatic frequency correction unit 471 enters tracking mode, pf ' is arranged
0=f
p+ Δ f
p-f
IpAt this moment, the frequency of descending tracking signal is f '
0=(f
p+ Δ f
p-f
Ip)/p=f
0(the 1+ Δ/(1-w)), and the frequency of up tracking signal is f "
0=2f
0-f '
0=f
0(the 1-Δ/(1-w)).This shows frequency f in descending tracking signal '
0In contain down-Doplet frequency-shifting operator+Δ, and in the frequency f of up tracking signal "
0In contain the up reverse Doppler frequency shift factor-Δ.
In down link, be df ' with obtaining frequency after the descending tracking signal process d frequency multiplication
0=f
d+ Δ f
d-f
IdLocal oscillation signal be used for descending down-conversion passage; Is d ' f with the reference frequency source signal through the frequency that obtains after d ' frequency multiplication
0=f
d-f
IdLocal oscillation signal be used for descending up-conversion passage.And in up link, be u ' f with the reference frequency source signal through obtaining frequency after u ' frequency multiplication
0=f
u-f
IuLocal oscillation signal be used for up down-conversion passage; With obtaining frequency after the up tracking signal process u frequency multiplication is uf "
0=f
u-Δ f
u-f
IuLocal oscillation signal be used for up up-conversion passage.
For down direction, what send to mobile repeater by base station or Remote Radio Unit is that the carrier wave standard frequency is f
dDownlink radio-frequency signal.Because the high-speed mobile of train, the downlink radio-frequency signal carrier frequency that arrives mobile repeater is f
d+ Δ f
d, Δ f wherein
dIt is the Doppler frequency shift of introducing.Downlink radio-frequency signal is f through the local oscillation signal frequency
d+ Δ f
d-f
IdDescending down-conversion passage to become carrier frequency be f
IdDescending intermediate-freuqncy signal, be f through the local oscillation signal frequency again
d-f
IdDescending up-conversion passage to become carrier frequency be f
dDownlink radio-frequency signal, send to the travelling carriage in the compartment.Since on the train in mobile repeater and the compartment relative movement speed of travelling carriage can ignore, so travelling carriage receives will be the standard downlink radio-frequency signal of no Doppler frequency shift.
Otherwise for up direction, what travelling carriage sent to mobile repeater on the train in the compartment is that the carrier wave standard frequency is f
uUp radiofrequency signal.Since on the train in mobile repeater and the compartment relative movement speed of travelling carriage can ignore, so the carrier frequency of the up radiofrequency signal received of mobile repeater still is f
uUp radiofrequency signal is f through the local oscillation signal frequency
u-f
IuUp down-conversion passage to become carrier frequency be f
IuUp intermediate-freuqncy signal, be f through the local oscillation signal frequency again
u-Δ f
u-f
IuUp up-conversion passage to become carrier frequency be f
u-Δ f
uUp radiofrequency signal, send to base station or Remote Radio Unit.Because mobile repeater has preset a reverse Doppler frequency shift-Δ f in up radiofrequency signal
u, the Doppler frequency shift Δ f that causes with the train high-speed mobile
uOffset, what therefore arrive base station or Remote Radio Unit will be the up radiofrequency signal of standard that does not have Doppler frequency shift.
Please continue to consult Fig. 4 and Fig. 5, its common second embodiment of the present invention that discloses, the main difference part of this embodiment and last embodiment can obviously draw by the contrast between figure and the figure, and be: at first, the relay of present embodiment is operated in the zero intermediate frequency territory but not frequency domain; Secondly, the reference signal of the automatic frequency correction unit 571 of present embodiment is derived from the feedback signal in controlled frequency source 561 (descending tracking signal) but not local reference frequency source signal; Moreover the signal processing of being distinguished the inside, doppler frequency shift tracking unit that causes by aforementioned two places changes.
Be to help understand first embodiment that adopts the intermediate frequency scheme and the detailed difference of adopting second embodiment of zero intermediate frequency scheme, followingly second embodiment done further announcement in conjunction with Fig. 4 and Fig. 5.
The no Doppler frequency shift relay of second embodiment of the invention is by donor antenna 301, be subjected to main antenna 302, duplexer 311,312, amplifier 321,322,323,324,325,326,327,328, frequency mixer 331,332,333,334, zero intermediate frequency low pass filter 341,342, frequency multiplier 351,352,353,354, reference frequency source 361, doppler frequency shift tracking unit 371, and coupler 381 constitutes.Wherein, amplifier 321, frequency mixer 331, amplifier 322 constitute the descending down-conversion passage of mobile repeater; Amplifier 325, frequency mixer 333, amplifier 326 constitute the descending up-conversion passage of mobile repeater.Descending down-conversion passage, low pass filter 341, descending up-conversion passage constitute the down link of mobile repeater together.Amplifier 328, frequency mixer 334, amplifier 327 constitute the up down-conversion passage of mobile repeater; Amplifier 324, frequency mixer 332, amplifier 323 constitute the up up-conversion passage of mobile repeater.Up down-conversion passage, zero intermediate frequency low pass filter 342, up up-conversion passage constitute the up link of mobile repeater together.Coupler 381, doppler frequency shift tracking unit 371, reference frequency source 361, frequency multiplier 351,352,353,354 constitute the frequency synthesizer of mobile repeater.Wherein, doppler frequency shift tracking unit 371 has the doppler frequency shift tracking ability, for descending down-conversion passage and up up-conversion passage provide the local frequency source; And reference frequency source 361 served as by the crystal oscillator of high stability (for example stability is better than ± the constant-temperature crystal oscillator TCXO of 0.01ppm), for descending up-conversion passage and up down-conversion passage provide the local frequency source.
After donor antenna 301 and duplexer 311, deliver to descending down-conversion passage from the downlink radio-frequency signal of base station or Remote Radio Unit and carry out down-conversion, the descending zero intermediate frequency signals that obtains is delivered to descending up-conversion passage and is carried out up-conversion after zero intermediate frequency low pass filter 341, the downlink radio-frequency signal that obtains thus is through duplexer 312 and be subjected to main antenna 302 to send to travelling carriage in the compartment.
Stand to deliver to up down-conversion passage after main antenna 302 and the duplexer 312 from the up radiofrequency signal of travelling carriage in the compartment and carry out down-conversion, the up zero intermediate frequency signals that obtains is thus delivered to up up-conversion passage and is carried out up-conversion after zero intermediate frequency low pass filter 342, the up radiofrequency signal that obtains sends to base station or Remote Radio Unit after duplexer 311 and donor antenna 301.
The feedback signal that the doppler frequency shift tracking unit 371 of present embodiment adopts controlled frequency source (VCXO) 561 to produce is the reference signal of descending tracking signal as the automatic frequency correction unit 571 of inside, and its theory diagram as shown in Figure 5.The controlled frequency source 561 that Doppler frequency shift unit 371 is served as by amplifier 521,522, frequency mixer 531,532, if bandpas filter 541,542, automatic frequency correction (AFC) unit 571, use VCXO (VCXO), frequency multiplier 551,552,553 constitute.It should be noted that, amplifier 521 wherein, 522 have constituted the down-conversion passage with frequency mixer 531, and coupler 381 can downconvert to the downstream signal of radio frequency domains the zero intermediate frequency territory with this down-conversion passage and this low pass filter 541, uses thereby offer described correcting unit 571.Described frequency multiplier 553, frequency mixer 532 and 542 in filter have constituted converter unit jointly, are used for the direction of the Doppler frequency shift factor of figure signal.
There are two input signals and two output signals in doppler frequency shift tracking unit 371.Two input signals are respectively the downlink radio-frequency signals that contains down-bound pilot frequency signal that obtain by coupler 381 couplings from the down link radio-frequency front-end and are f by the frequency that reference frequency source 361 provides
0Reference frequency signal; Two output signals are respectively that the frequency that can follow the tracks of descending forward Doppler frequency shift is f
0' descending tracking signal and the frequency that has preset up reverse Doppler frequency shift be f
0" up tracking signal.
In doppler frequency shift tracking unit 371, it is descending tracking signals that controlled frequency source (VCXO) 561 is subjected to the signal of the control output of correcting unit 571, its frequency f
0' be subjected to the control of the control signal that automatic frequency correction unit 571 produces.One road input signal of automatic frequency correction unit 571 is the intermediate frequency pilot signal that obtains after the frequency-doubled signal mixing, filtering of the signal of down-bound pilot frequency signal and controlled frequency source (VCXO) 561 outputs.Another road input signal of automatic frequency correction unit 571 is that reference signal is that controlled frequency source 561 feedback signals are the frequency-doubled signal of descending tracking signal.The function of automatic frequency correction unit 571 is exactly to detect the existence of down-bound pilot frequency signal, and under the situation that down-bound pilot frequency signal exists, calculate the frequency error function between down-bound pilot frequency signal (through frequency conversion) and this feedback signal (through frequency multiplication), produce control signal corresponding and regulate the frequency in controlled frequency source (VCXO), keeping the said frequencies error is zero.
In converter unit, descending tracking signal is carried out mixing with 2 frequency-doubled signals of local reference frequency source signal again, and getting and obtaining frequency after the latter and the former the difference frequency signal filtering is f
0=2f
0-f
0' up tracking signal.
In conjunction with Fig. 4 and Fig. 5, the standard frequency of setting capable radiofrequency signal carrier wave is f
d, the standard frequency of up radiofrequency signal carrier wave is f
u, the standard frequency of down-bound pilot frequency signal is f
p, the standard frequency of descending intermediate frequency pilot signal is f
i, make x=f
d/ f
0, y=f
u/ f
0, z=f
p/ f
0, v=f
i/ f
0The multiplier parameter of getting frequency multiplier 351,353 is d=d '=x, and the multiplier parameter of frequency multiplier 352,354 is u=u '=y, and the multiplier parameter of frequency multiplier 551 is p=z-v, and the multiplier parameter of frequency multiplier 552 is q=v, and the multiplier parameter of frequency multiplier 553 is 2.
The frequency of the down-bound pilot frequency signal that mobile repeater is received is f
p+ Δ f
p, Δ f wherein
pBe its Doppler frequency shift.This signal and frequency are f
0' the frequency-doubled signal pf ' of descending tracking signal
0Obtaining frequency after mixing, the filtering is f
i'=f
p+ Δ f
p-pf
0' the intermediate frequency pilot signal.Automatic frequency correction unit 571 calculates the intermediate frequency pilot signal and frequency is qf
0' the frequency-doubled signal of controlled frequency source feedback signal between the frequency error function, and regulate VCXO 561 according to this, serve as zero to keep frequency error, i.e. qf
0'-f
i'=0.Therefore, when automatic frequency correction unit 571 enters tracking mode, f is arranged
p+ Δ f
p-pf
0'=qf
0'.At this moment, the frequency of descending tracking signal is f
0'=(f
p+ Δ f
p)/(p+q)=f
0(1+ Δ), and the frequency of up tracking signal is f
0"=2f
0-f
0'=f
0(1-Δ).This shows frequency f in descending tracking signal
0' in contain the descending forward Doppler frequency shift factor+Δ, and in the frequency f of up tracking signal
0" in contain the up reverse Doppler frequency shift factor-Δ.
In down link, be df with obtaining frequency after the descending tracking signal process d frequency multiplication
0'=f
d+ Δ f
dLocal oscillation signal be used for descending down-conversion passage; Is df with the reference frequency source signal through the frequency that obtains after d ' frequency multiplication
0'=f
dLocal oscillation signal be used for descending up-conversion passage.And in data feedback channel, be u ' f with the reference frequency source signal through obtaining frequency after u ' frequency multiplication
0=f
uLocal oscillation signal be used for up down-conversion passage; With obtaining frequency after the up tracking signal process u frequency multiplication is uf
0"=f
u-Δ f
uLocal oscillation signal be used for up up-conversion passage.
For down direction, what send to mobile repeater by base station or Remote Radio Unit is that the carrier wave standard frequency is f
dDownlink radio-frequency signal.Because the high-speed mobile of train, the downlink radio-frequency signal carrier frequency that arrives mobile repeater is f
d+ Δ f
d, Δ f wherein
dIt is the Doppler frequency shift of introducing.Downlink radio-frequency signal is f through the local oscillation signal frequency
d+ Δ f
dDescending down-conversion passage become descending zero intermediate frequency signals, be f through the local oscillation signal frequency again
dDescending up-conversion passage to become carrier frequency be f
dDownlink radio-frequency signal, send to the travelling carriage in the compartment.Since on the train in mobile repeater and the compartment relative movement speed of travelling carriage can ignore, so travelling carriage receives will be the standard downlink radio-frequency signal of no Doppler frequency shift.
Otherwise for up direction, what travelling carriage sent to mobile repeater on the train in the compartment is that the carrier wave standard frequency is f
uUp radiofrequency signal.Since on the train in mobile repeater and the compartment relative movement speed of travelling carriage can ignore, so the carrier frequency of the up radiofrequency signal received of mobile repeater still is f
uUp radiofrequency signal is f through the local oscillation signal frequency
uUp down-conversion passage become up zero intermediate frequency signals, be f through the local oscillation signal frequency again
u-Δ f
uUp up-conversion passage to become carrier frequency be f
u-Δ f
uUp radiofrequency signal, send to base station or Remote Radio Unit.Because mobile repeater has preset a reverse Doppler frequency shift-Δ f in up radiofrequency signal
u, the Doppler frequency shift Δ f that causes with the train high-speed mobile
uOffset, what therefore arrive base station or Remote Radio Unit will be the up radiofrequency signal of standard that does not have Doppler frequency shift.
By above-mentioned two embodiment as can be seen, no Doppler frequency shift relay of the present invention (mobile repeater) is to have introduced the doppler frequency shift tracking unit 271 or 371 with doppler frequency shift tracking ability with the fundamental difference of traditional fixedly repeater in the repeater.If doppler frequency shift tracking unit 271 or 371 usefulness reference frequency source are replaced, mobile repeater is just identical with traditional fixedly repeater so.
It is to be noted, for the broad band repeater that comprises a plurality of frequency division carrier waves, because of its have only a broadband on/down going channel, on being somebody's turn to do/the radiofrequency signal carrier frequency of down going channel can not be all identical with the frequency of each frequency division carrier wave, therefore after proofreading and correct through Doppler frequency shift, in each frequency division carrier wave, also may have remaining Doppler frequency shift, but the residue Doppler frequency shift is no more than Δ B/2, wherein Δ is the Doppler frequency shift factor, and B is the bandwidth of broad band repeater.For the frequency selecting repeater that comprises a plurality of frequency division carrier waves, because of its have a plurality of arrowbands on/down going channel, on each/down going channel is all corresponding with a frequency division carrier wave, after therefore proofreading and correct through Doppler frequency shift, can eliminate the Doppler frequency shift in each carrier wave fully.
More than doppler frequency shift tracking unit among two kinds of embodiment, both can adopt analog circuit to realize, also can adopt digital circuit to realize.If when adopting digital circuit to realize, the above-mentioned VCXO (VCXO) that uses as the controlled frequency source should change numerically-controlled oscillator (NCO) into.If when adopting analog circuit to realize, adopt the intermediate frequency scheme usually.For the frequency selecting repeater of simulation, wish that also the IF-FRE of each passage when doing band limiting filtering is identical usually.But in above-mentioned intermediate frequency scheme, the IF-FRE of each passage is also inequality.At this moment can on the basis of above-mentioned two kinds of basic schemes, derive two kinds of unified intermediate frequency schemes, as third and fourth embodiment of the present invention.
The unified intermediate frequency scheme that is derived from by the intermediate frequency scheme of above-mentioned first embodiment is as the third embodiment of the present invention, as shown in Figure 6.Compare with intermediate frequency scheme shown in Figure 2, in descending up-conversion passage, increased amplifier 625, secondary mixing device 633, amplifier 626, unified intermediate-frequency filter 641 and frequency multiplier 653; And unified intermediate-frequency filter 642, amplifier 628, secondary mixing device 634, amplifier 627 and frequency multiplier 654 in up up-conversion passage, have been increased.The descending intermediate frequency that descending secondary mixing device will have nothing in common with each other originally this moment mixes on the unified descending intermediate frequency and carries out band limiting filtering again; Up secondary mixing device then mixes the up unified intermediate frequency behind the band limiting filtering and carry out up-conversion again to different up intermediate frequency.Identical in multiplier parameter d, u and the former intermediate frequency scheme, multiplier parameter d ", u ", d ', u ' then get xw-v, yw-v, x-v, y-v, wherein v=f respectively
i/ f
0, f
iBe unified IF-FRE.
The unified zero intermediate frequency scheme that is derived from by the zero intermediate frequency scheme of above-mentioned second embodiment is as the fourth embodiment of the present invention, as shown in Figure 7.Compare with zero intermediate frequency scheme shown in Figure 3, increased frequency mixer 735,736, local oscillation signal filter 743,744, frequency multiplier 755, change original zero intermediate frequency low pass filter 341 and 342 into unified zero intermediate frequency filter 741 and 742 in addition.The local oscillation signal of descending down-conversion changed the signal that is obtained after through the d frequency multiplication by descending tracking signal and passed through the signal mixing that obtains after the v frequency multiplication with reference frequency and obtain this moment; The local oscillation signal of up up-conversion then changes the signal that is obtained after through the u frequency multiplication by up tracking signal to be passed through the signal mixing that obtains after the v frequency multiplication with reference frequency and obtains.Multiplier parameter v=f wherein
i/ f
0, f
iBe unified zero intermediate frequency frequency.
As seen from the above-described embodiment, in no Doppler frequency shift relay of the present invention, the automatic frequency correction unit is its core.In no Doppler frequency shift relay of the present invention, except the function of tracking correction frequency, in down-bound pilot frequency signal is not (for example down-bound pilot frequency signal is intermittently to send in the gsm mobile communication system) under the situation about always existing, and the automatic frequency correction unit also needs to detect the existence of pilot signal.Detect the algorithm of pilot signal and can formerly apply for a patent " based on the digitlization automatic frequency detection method of real signal " (patent publication No.: CN101471727) with reference to the applicant, and the algorithm of automatic frequency correction can formerly be applied for a patent " based on the digitlization automatic frequency correcting method of real frequency reference signal " (patent publication No.: CN101471726), can certainly adopt other algorithm with reference to the applicant.Those of ordinary skills can know this accommodation after reading over the present invention.
In sum, the Doppler frequency shift when the present invention can eliminate travelling carriage in the high-speed motion carrier effectively and communicates by letter with base station or Remote Radio Unit plays the effect that guarantees communication quality.
The foregoing description is a preferred implementation of the present invention, but and not only is restricted to the described embodiments.For example in the conversion process of the foregoing description, can adopt different high and low local oscillators and upper and lower sideband scheme, at this moment as long as the multiplier parameter of corresponding each frequency multiplier of adjustment just can be realized different frequency conversion schemes; The local oscillation signal of upper and lower converter unit also can exchange in the uplink and downlink passage in addition.Therefore other any do not deviate from change, the modification done under spirit of the present invention and the principle, substitute, combination, abbreviation, all should be considered as equivalent replacement mode of the present invention, and be included within protection scope of the present invention.
Claims (20)
1. doppler frequency shift tracking unit is used to follow the tracks of the Doppler frequency skew of the signal that causes because of high-speed motion of relay, it is characterized in that this tracking cell comprises:
Coupler is used for being coupled out one road downstream signal at the radio-frequency front-end of relay down link;
The controlled frequency source produces the descending tracking signal that comprises the descending forward Doppler frequency shift factor under the control of correcting unit;
The down-conversion passage, the frequency of the descending tracking signal that produces with the controlled frequency source is a benchmark, and downstream signal is carried out down-conversion;
Reference unit is used to produce a reference signal for the correcting unit reference;
Correcting unit is used to ask for down-bound pilot frequency signal that downstream signal comprised after the down-conversion and the frequency error function between the described reference signal, and the frequency of regulating the descending tracking signal that the controlled frequency source produces makes this functional value be maintained zero;
Converter unit is transformed to this descending tracking signal the up tracking signal that comprises the up reverse Doppler frequency shift factor.
2. doppler frequency shift tracking according to claim 1 unit is characterized in that, described reference unit comprises frequency multiplier and the intrinsic reference frequency source of relay, and the signal that reference frequency source produces becomes described reference signal after the frequency multiplier frequency multiplication.
3. doppler frequency shift tracking according to claim 1 unit is characterized in that, described reference unit comprises frequency multiplier and described controlled frequency source, and the descending tracking signal that the controlled frequency source produces becomes described reference signal after the frequency multiplier frequency multiplication.
4. doppler frequency shift tracking according to claim 1 unit is characterized in that, described controlled frequency source is VCXO (VCXO) or numerically-controlled oscillator (NCO).
5. doppler frequency shift tracking according to claim 1 unit is characterized in that, is provided with a frequency multiplier between described controlled frequency source and the down-conversion passage the descending tracking signal that the controlled frequency source produces is carried out the frequency multiplication computing.
6. according to any described doppler frequency shift tracking unit in the claim 1 to 5, it is characterized in that, this tracking cell also comprises filter, and it is serially connected with between down-conversion passage and the correcting unit, and the downstream signal after the down-conversion is carried out being transferred to described correcting unit after the filtering.
7. according to any described doppler frequency shift tracking unit in the claim 1 to 5, it is characterized in that described converter unit comprises:
Frequency multiplier is used for the signal that the existing reference frequency source of relay produces is carried out the frequency multiplication computing of preset multiple;
Frequency mixer produces described up tracking signal thereby utilize the operation result of this frequency multiplier and descending tracking signal to carry out mixing;
Filter is used for described up tracking signal is carried out exporting after the filtering.
8. no Doppler frequency shift relay is used to the Doppler frequency skew that realizes signal relay and eliminate the signal that causes because of high-speed motion, and it comprises down link and up link, it is characterized in that, this device also comprises:
As any described doppler frequency shift tracking unit in the claim 1 to 7;
Down-conversion passage in the down link, the descending tracking signal of exporting with this tracking cell is that local oscillator is carried out mixing to eliminate the forward Doppler frequency shift in the downstream signal to the downstream signal in the down link;
Up-conversion passage in the up link, the up tracking signal of exporting with this tracking cell is that local oscillator is carried out mixing to preset reverse Doppler frequency shift in upward signal to the upward signal in the up link.
9. no Doppler frequency shift relay according to claim 8, it is characterized in that, this device comprises donor antenna and be used for and base station or the wireless electric connection of Remote Radio Unit by main antenna, donor antenna, be used for and the wireless electric connection of travelling carriage by main antenna.
10. no Doppler frequency shift relay according to claim 9 is characterized in that, described donor antenna adopts omnidirectional or directional antenna, the described leaky cable that is subjected to main antenna to adopt the one lengthwise.
11. any described no Doppler frequency shift relay in 10 is characterized in that according to Claim 8, described reference frequency source adopts stability to be better than ± crystal oscillator of 0.01ppm.
12. a no Doppler frequency shift trunking method is used for realizing that signal relay and erasure signal because of the Doppler frequency skew that high-speed motion causes, is characterized in that it comprises the steps:
1) from the down link radio-frequency front-end, is coupled out one road downstream signal;
2) produce line trace signal;
3) following line trace signal is that benchmark downconverts to intermediate frequency or zero intermediate frequency territory with this radio frequency downstream signal;
4) ask for down-bound pilot frequency signal and frequency error function that supplies between the reference signal of reference that this intermediate frequency or zero intermediate frequency territory downstream signal are comprised, and regulating step 2) the middle frequency that produces descending tracking signal, so that this functional value is maintained zero;
5), be that local oscillator is carried out mixing to eliminate the forward Doppler frequency shift in the downstream signal to downstream signal with this descending tracking signal for down link;
6) for up link, earlier this descending tracking signal is transformed to the up tracking signal that presets reverse Doppler frequency shift, be that local oscillator is carried out up-conversion to upward signal with this up tracking signal again, in upward signal, to preset reverse Doppler frequency shift.
13. no Doppler frequency shift trunking method according to claim 12 is characterized in that, the reference signal in the described step 4) is obtained after the frequency multiplication computing by the signal that a reference frequency source produces.
14. no Doppler frequency shift trunking method according to claim 12 is characterized in that the reference signal in the described step 4) is by described step 2) descending tracking signal after the frequency multiplication computing, obtain.
15. no Doppler frequency shift trunking method according to claim 12 is characterized in that, described descending tracking signal is produced by a controlled VCXO (VCXO) or a numerically-controlled oscillator (NCO).
16. no Doppler frequency shift trunking method according to claim 12 is characterized in that the descending tracking signal in the described step 3) has been passed through the frequency multiplication computing.
17., it is characterized in that frequency domain in the described step 4) or zero intermediate frequency territory downstream signal have passed through filtering according to any described no Doppler frequency shift trunking method in the claim 12 to 16.
18. according to any described no Doppler frequency shift trunking method in the claim 12 to 16, it is characterized in that, in the step 6), filtering after the frequency multiplication operation result mixing of the signal that described up tracking signal is produced by described descending tracking signal and a reference frequency source and getting.
19. bullet train wireless shrouding system, it is characterized in that: it adopts as any described no Doppler frequency shift relay in the claim 8 to 11, its donor antenna is placed on the bullet train top, and it is laid along the compartment one lengthwise of bullet train by main antenna.
20. a bullet train wireless coverage scheme is applicable to the train of relative radio repeater station high-speed mobile to it is characterized in that it comprises the steps:
1) on bullet train, installs the repeater, and base station or Remote Radio Unit signal that this repeater receives only a direction at any time are set, ignore the signal of other direction;
2) down link for this repeater provides the descending tracking signal that can follow the tracks of the forward Doppler frequency shift, for the up link of this repeater provides the up tracking signal that has preset reverse Doppler frequency shift.
3) descending tracking signal is used for the down-conversion passage and the up-conversion passage of this repeater down link, eliminates the Doppler frequency shift that relatively moves and in downstream signal, introduce because of train, so that travelling carriage receives the downstream signal of no Doppler frequency shift in the train;
4) up tracking signal is used for the down-conversion passage and the up-conversion passage of the up link of this repeater, in upward signal, presets reverse Doppler frequency shift, so that radio repeater station receives the upward signal of no Doppler frequency shift.
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