Summary of the invention
The invention provides a kind of method and apparatus that is used for handling a plurality of signals that take public frequency by wall scroll RF cable.Method and apparatus of the present invention can comprise one or more HPA, and it is positioned at the base portion of the antenna structure that is used for forward link transmissions.Under the situation of rl transmission, method and apparatus of the present invention does not need to be positioned at the HPA of antenna structure base portion, but but needs to be positioned at the preamplifier of antenna structure masthead.Should be appreciated that such preamplifier power is relatively low, therefore have suitable reliability on the masthead, and do not damage value of the present invention for being placed on.
Base portion at the antenna structure with unlike signal (on public frequency) uses under the situation of a plurality of HPA, and this HPA is positioned in and merges these signals and they are fed to before the wall scroll RF cable.Using under the situation single HPA, alternative, this single HPA be positioned in merge after these signals, but at the signal of presenting this merging before the wall scroll RF cable.Any forward link transmissions that all is very suitable for of both of these case, and should easily understand, under the situation that does not deviate from this method and device preset range, the particular location of one or more HPA and placement can change owing to the realization that the present invention provides.In addition, the present invention does not need even the existence of a HPA.More properly, method and apparatus of the present invention is suitable for not using the rl transmission of HPA.Under these circumstances, reliable relatively, lower powered preamplifier will be located in the antenna masthead of antenna structure.
The present invention is practicable in the following manner and for forward link transmissions, that is: merge a plurality of signals (before or after amplifying) at the antenna structure base portion by aforesaid one or more HPA, the signal that should merge via wall scroll RF cable transmission is to the antenna masthead, and these a plurality of signals be transferred to one group of antenna port with carry out from it signal propagate before signal relief merging to being merged.
The present invention is practicable in the following manner and for rl transmission, that is: the masthead place of antenna structure use low power amplifier amplify a plurality of signals in advance after again with its merging, be somebody's turn to do the signal of merging to the antenna base portion via wall scroll RF cable transmission, and being transferred to one group of input port (such as the input of, base station receiver) at these a plurality of signals merges the signal relief that is merged with carry out the signal transmission from it before.
Feature about in same frequency, merging a plurality of signals and subsequently such gathering signal relief is merged of the present invention, for the RF system (such as but not limited to, have the cdma system of masthead HPA and RF cable laying) in reduced expensive high-power RF circuit element the part relevant with antenna.In fact, the present invention is system's (that is, being independent of modulation format) independently, and in this, any RF system of transmitting a plurality of signals with public frequency on wall scroll RF cable will benefit from disclosed method and apparatus of the present invention here.
Method and apparatus of the present invention is finished by the modulation/demodulation scheme of using Walsh (Walsh) sign indicating number and improved Wilkinson (Wilkinson) combiner.Walsh code modulation/demodulation scheme is further discussed hereinafter.Basic conception among the present invention is the same for forward direction or reverse link.That is to say, the forward direction and the rl transmission that occur within the scope of the present invention all comprise following favourable feature: modulation has the signal of public frequency, merge such signal so that transmit the signal of this merging along wall scroll RF cable, and the signal of this merging removed merge and demodulation, thereby there are severe attrition, distortion or cross-talk ground not to reconstitute this primary signal.
In the situation of forward link transmissions, have public frequency each free short walsh code phase sequence (phase sequence) of a plurality of (N) signal, modulate by the corresponding phase shifter on each in N is imported.Specifically, these a plurality of signals are according to a short walsh modulation sequence (length that 4 chips are arranged in illustrated example) and by phase shift.This phase shift signal is merged to form a gathering signal then.Then this gathering signal passes a single HPA by transmission and is exaggerated.Replacedly, as mentioned above, these signals can be exaggerated before being modulated by walsh code sequences and be merged subsequently.A wall scroll RF cable that upwards reaches antenna structure length is passed in the gathering signal transmission that this permission will be amplified.At the antenna masthead, the gathering signal of this amplification is separated together with the Wilkinson combiner of revising via delay line, then via the Walsh demodulation scheme by demodulation.The signal of each relevant demodulation, phase shift is passed to the predetermined relevant antenna port that is used for from wherein propagating afterwards.
In the rl transmission situation, a plurality of (N) signal with public frequency is received at each antenna port, passes each low-power preamplifier that is positioned at this antenna masthead by transmission then and is exaggerated.Each signal that is exaggerated is by a short walsh code phase sequence, by each phase shifter and modulated afterwards.Specifically, these a plurality of signals are according to a short walsh modulation sequence (being the length of 4 chips in illustrated example) and by phase shift.This phase shift signal is merged to form the gathering signal then.The gathering signal transmission that this permission will be amplified is passed one to the wall scroll RF cable of assigning antenna structure length.At the base portion of antenna structure, the gathering signal of this amplification is separated together with the Wilkinson combiner of revising via delay line, then via the Walsh demodulation scheme by demodulation.The signal of each relevant demodulation, phase shift is passed to one group and is used to carry out the input port that signal receives (such as, base station receiver input) afterwards.
Though may use the present invention according to a certain mode, this mode of relying on can arrange this method and device to receive or transmission so that provide as the above signal of summarizing, but the embodiment of more detailed argumentation for the sake of clarity, will mainly concentrate on forward link.Should finely understand, for the those of ordinary skill of digital processing field, the variation that will recognize that reverse link is also fully in preset range of the present invention.Equally, person of skill in the art will appreciate that detailed realization will need circuit details, it is below only with general term discussion.In addition, any such general introduction is for the preferred embodiments of the present invention clearly are described.
Detailed Description Of The Invention
Only be for illustrative purpose, will come that present invention is described in conjunction with some embodiment; Yet, being appreciated that other purpose of the present invention and advantage, will become apparent description by following according to accompanying drawing of the present invention.Though disclose preferred embodiment, do not meant that to be only limited to this.More properly, here the General Principle of Chan Shuing is regarded as merely the explanation to the scope of the invention, and can further be interpreted as under the situation that does not depart from the scope of the invention and can make many changes.
At cdma system or any relevant RF system run duration, may reach peak traffic capacity corresponding to a sector of a multi-sector antenna, and need maximum power usually.Routinely, for example in one three sector cell, when three cables along antenna tower rise and the HPA that has three correspondences when sending signal separately along corresponding cable, if the power of sector needs then has no idea to make power to shift between each sector more than other two sectors.In the present invention, because signal is merged, so power is shared between three sectors effectively, and total power always can be used any sector effectively.This is to finish via the relay feature of a HPA and a cable.
With reference to figure 1, it has illustrated the example that uses the first embodiment of the invention 100 of the modulating/demodulating of realizing via walsh code.Though only show two signal input channels 10,11 that are used for corresponding sector, should be appreciated that for the present invention to have a plurality of sectors and corresponding signal (that is N signal).As shown, these two channels 10,11 (such as, CDMA forward link sector or wave beam) will be modulated via quick chip Walsh modulator 12,13.
Generally speaking, walsh modulation/demodulation involves and utilizes walsh code to distinguish different signals during the transmission.Those skilled in the art will understand and have several different extended codes that it can be used in cdma communication system data-signal is separated from each other.These extended codes include but not limited to pseudo noise (PN) sign indicating number and walsh code.Walsh code is corresponding to single row or column of hadamard (Hadamard) matrix.For instance, in 64 channel CDMA spread spectrum systems, specific mutually orthogonal walsh code can be elected from the set of 64 walsh codes in 64 * 64 hadamard matrixs.And specific data-signal can be separated so that expand this specific data-signal with other data-signals by using specific walsh code.
In addition, those skilled in the art will understand that extended code can be used to data-signal is carried out chnnel coding.This data-signal is carried out chnnel coding, so that by making transmission signals can resist the influence of different channel impairments (for example noise, decline and obstruction) better, and improves the performance of this communication system.At modulated data signal so as subsequently the transmission before, walsh code can be used to this data-signal is carried out chnnel coding.Under the situation that does not depart from preset range of the present invention, other quadrature or quasi-orthogonal method also can be used to modulation in being used for the method and apparatus of equivalent embodiment of the present invention.In order to use walsh code in signal extension or chnnel coding, this walsh code must be easy to obtain so that use.A kind of technology that makes walsh code be easy to obtain is: generate walsh code by place the walsh code of wanting in based on the look-up table of memory.Subsequently, when each walsh code of needs, must from this look-up table, retrieve it.
In the present invention, the modulation of use is the long walsh code of 4 chips-such as, 4x4 walsh code matrix.Continuation all is to carry out two-phase PSK (BPSK) modulation by the walsh code (in modulator 12,13) from unique (and different) in these 4 available walsh codes with reference in 1, two input channel of figure 10,11 each.This modulation rate is synchronized with normal CDMA spreading rate, but this speed (that is, N 4Fc) doubly.The effect of this (fast) walsh code modulation on normal CDMA chip is: produce Sin (x)/x frequency spectrum that has with the carrier frequency sideband that is the center, separates by N*Fc.Consideration input channel 10 usefulness fast walsh code zero (0) are modulated.The signal component that is used for input channel 10 will enter " homophase " separator 16 and by 1/2 at a slow speed chip (that is two " fast " chip delay lines 17) postpone discriminatively.
Continuation is with reference to figure 1, and walsh code modulated signals is merged into a RF stream by combiner 14 then.If the generation forward link transmissions, shown in Figure 1A, input signal 10,11 can be exaggerated by corresponding high power amplifier (HPA) 30,31 before modulation separately so.Replacedly, shown in Figure 1B, be placed on combiner 14 public HPA 32 afterwards and also can be used for forward link realization of the present invention.Importantly will note: such merging allows to use wall scroll RF cable 15 between one or more HPA and demodulating unit 12a, 13a at the masthead (not shown).Though need bigger a little cable, to the windage of these antenna tower and relevant structural upgrading by a utilization cable 15 and being reduced significantly only.Preliminary experiment is the result show, with regard to the present invention, depends on that power consumption in the single cable of required cable length can minimize or may be better than loss in the demodulation that strengthens.
Then, two differential signals are applied in hybrid circuit (hybrid), and this hybrid circuit will be assembled in Signal Separation to the two different path.The effect of similar " comb filter " is played in the combination of two " fast " chip delay lines 17 and four " fast " chip delay lines 18 (with associated switch circuit 19,20), force " homophase " port that appears at the Wilkinson combiner 22 of modification from the difference RF signal of walsh code 0 and 1, appear at " anti-phase " port of same combiner 22 simultaneously from the difference RF signal of walsh code 2 and 3.Therefore, the combination of the Wilkinson combiner 22 of switching delay line filter (being as general as unit 16,17,18,19,20 and 21) and modification is served as a plurality of decomposers 300 with the form of high-power RF walsh code discriminator.
The Wilkinson combiner 22 of this modification is configured to a 4-port, relative phase discriminator.The signal that this means two input ports (port one and port 2) that appear at " homophase " is merged at summation output (port 3), and the signal that appears at the input port of " anti-phase " occurs at difference port (port 4).Main modification to standard Wilkinson combiner is: the balancing resistor of the inversion signal energy that will just be commonly used to dissipate replaces with the RF transformer, and it provides the low-loss path of leading to difference port (port 4).Yet, being purpose of the present invention, any (low-loss) circuit that can distinguish input signal two " homophases " or " anti-phase " effectively all can be used in and replace Wilkinson combiner 22.
When signal by demodulator 12a, when 13a reconstitutes, the final stage of this processing procedure occurs, demodulator 12a, 13a are actual in the operation to modulator 12,13 to be the same.Filter 23,24 guarantees that further this output signal 10a that reconstitutes, 11a and input signal 10,11 are basic identical and does not contain any distortion.Should be readily appreciated that under the situation that does not depart from preset range of the present invention, except the top forward link of mentioning at Figure 1A and 1B, transmission also can be in reverse link.In this situation of the rl transmission under the present invention, will not use HPA.More properly, with the low-power preamplifier 33,34 of needs as shown in Fig. 1 C.
In the illustrated embodiment of Fig. 1, modulator 12,13 and demodulator 12a, 13a comprise λ/2 circuits, and it is switched on or switched off by pin diode switch, and pin diode switch is controlled by the clock signal that derives from the N*Fc clock of transceiver.Though what here describe is PIN diode, those skilled in the art should understand at an easy rate: any suitable switch element can be used.Following table 1 has been indicated the signal processing that appears in Fig. 1.
Table 1
Fig. 2 shows a series of signal emulation with plotting mode.Each shown diagrammatic representation is corresponding to the moment of the signal processing of Fig. 1.Among Fig. 2, input signal 10,11 is by graph of a correspondence 80,81 expressions.In modulation 12,13 and merge after 14, this gathering signal is used respectively in figure 82 corresponding to signal 1 component of input signal 10 and 11 and signal 2 components and is illustrated.This gathering signal is transmitted through one section RF cabling 15.A plurality of decomposition occur in the other end of this RF cabling 15, and by shown in a plurality of decomposers 300 expression, and produce figure 83 and 84 corresponding to each modulation signal 1 and signal 2 components.Then each through signal a plurality of decomposition, modulated by the demodulator 12a of correspondence, 13a demodulation to form signal 10a, the 11a of the recovery shown in figure 85 and 86.
Represent separator 16 at a plurality of decomposers 300 shown in Fig. 1 and 2, delay line 17,18,19,20,21 and the Wilkinson combiner of revising 22.In operation, a plurality of decomposers 300 differentiate that by relative narrow band filter each signal (being the sector) with different walsh code precodings this relative narrow band filter constitutes together with the Wilkinson combiner of revising 22 with delay line 17,18,19,20,21.Because walsh code has been expressed their mutually orthogonal property in frequency domain, so such filter is fulfiled its discriminating task.Specifically, merge the situation of two sectors for one four chip walsh code group, have four to divide the frequencies of opening by Fc/4, it can be merged to produce each chip in the four walsh code chip set.For instance, first walsh code (that is, walsh code zero) has the zero offset frequency from input signal.That is to say that this primary signal is constant after with walsh code acyclic homologically trioial system.Therefore, unique frequency spectrum of walsh code zero is only occupied at deviation frequency zero place.The frequency spectrum of this frequency spectrum and walsh code 2 forms contrast, and walsh code 2 has its energy at deviation frequency 1*Fc/4 and 3*Fc/4 place.
Ideally, have distinguish strange and even deviation frequency (that is, the zero-sum 2*Fc/4 in this example or 1 and 3*Fc/4) high-power, the low loss filter of small component tally function can distinguish walsh code zero-sum walsh code 2.According to the present invention, simple delay line filter (being as general as 17 among Fig. 1,18,19,20,21) is fulfiled odd number/even frequency and is differentiated, wherein F (t)/2+F (t+2 chip)/2 only transmits walsh code zero-sum 1 (from this group of four), and F (t)/2-F (t+2 chip)/only transmit walsh code 2 and 3 from this group.Therefore, connection delay and undelayed chip make even deviation frequency (walsh code zero-sum 1) appear at normal (even-mode) output to two combiner inputs of the Wilkinson combiner of revising, and make strange deviation frequency (walsh code 2 and 3) stride the appearance of the 4th (odd mode) Wilkinson port.The 4th Wilkinson port generally has one 100 ohm resistor, but it is modified to and comprises 50 ohm resistor according to the present invention.Should be noted that it also is possible using one 4 port, 90 degree hybrid circuits for this purpose, as long as there is low RF loss less than 0.2dB.
Aforesaid, the present invention can be used in a plurality of signals.Though only so described two signals for the present invention, Fig. 5 shows the example of the basic inventive concept that is applied to three sectors layout.
Fig. 5 shows the block diagram of handling three (3) input signals 40,41,42 according to the present invention.At as described in Fig. 1, each input signal 40,41,42 is via modulator 43,44,45 modulation as above.This modulation signal is merged by combiner 46 and makes it to pass one section RF cabling 47 then.Though not shown, can be during forward link transmissions provide a plurality of HPA or single HPA in mode as mentioned above.After via 46 transmission of RF cabling, this gathering signal flow passes first separator 50 and passes more than first and second decomposer of arranging with cascade system (stack up is respectively 50-56 and 60-66).Below table 2 show the signal processing that always reaches till these RF cabling 47 length.
Table 2
More particularly, this gathering signal flow passes first delay line (being as general as 51,52,53,54,55) and passes the first Wilkinson combiner of revising 56 in mode as described in Figure 1 subsequently.Yet, in this three sector configuration, the signal 42a that the difference port transmission of first combiner 56 reconstitutes with output to demodulator 45a and filter 72 corresponding to the signal component of input signal 42, it is basic identically corresponding to input signal 42.In summation port transmission many decomposers of residual signal component to the second (being as general as 60-66) of first combiner 56 corresponding to input signal 40,42.This residual signal component is separated by second separator 60 and is handled by second delay line (being as general as 61,62,63,64,65), and is handled in mode as described in Figure 1 by the second Wilkinson combiner of revising 66 once more subsequently.
In this, the signal 40a that the difference port transmission of first combiner 56 reconstitutes with output to demodulator 43a and filter 70 corresponding to the signal component of input signal 40, it is basic identically corresponding to input signal 40.The summation port of second combiner 66 transmits corresponding to the residual signal component of input signal 41 to demodulator 44a and filter 71 to export regenerated signal 41a, and it is basic identically corresponding to input signal 41.Following table 3 has been indicated the signal processing that occurs after inherent this section RF of Fig. 3 cabling 47.
Table 3
Should be readily appreciated that, reduce the traditional approach that uses a plurality of HPA and cable by the present invention, and reduced system cost, because HPA is one of the most expensive element in base station.Yet, should be noted that also a plurality of HPA still can have benefited from the demodulation configurations of the present invention's general introduction.
Further, within preset range of the present invention, even if use a plurality of HPA, the sum of HPA also can reduce, because input signal can appear at this system Anywhere to the relation of the N:1 that assembles signal.Therefore, the relation of cdma communication system or the like 1:N that will still benefit from the demodulation of the antenna end of tower.In such a case, having realized that still needs many cables upwards to arrive antenna along tower, but by demodulating equipment of the present invention and method, will eliminate the existence of the HPA on the masthead.
Generally speaking, the present invention provides the improvement of significant capacity to communication system (such as but not limited to, CDMA Cellular System).These improvement are that base station section relaying usefulness can be from the direct result of the individual usefulness that obtains of every sector power amplifier above those.This causes by the following fact, and promptly in CDMA Cellular System, the mobile service amount distributes and crosses over normally that each sector distributes unequally.Therefore, sector through be everlasting other and additional user be blocked be linked into this sector before, reach its maximum power (that is traffic peak) ability.Yet the present invention allows to be re-routed to the heavy sector of load from the RF power of other under-utilized sector.Therefore, can hold the much bigger traffic carrying capacity that is supplied to before stopping generation, this has increased the maximum traffic capacity of base station effectively.
It can both be available in any sector that the present invention makes all the RF power from all sectors, arbitrary to mate (arbitrarily) sector traffic load combination.This processing procedure is automatically, although and therefore sector load imbalance, also improved the service in base station capacity.Further, reduce the quantity and the size of antenna tower RF cable, help the operator of system to require to control their capital expenditure by the reinforcing that reduces tower.And if antenna tower are shared by the operators of system or rented, then rental expenses usually increase when cable increases.Importantly be that under such situation, system operator may be prevented from the number (load of supporting business amount increases required) of extended antenna tap cable.Certainly, this directly influence increase of income in the future in those places.
The nearest introducing of antenna system makes the problem aggravation of speaking of above, and antenna system needs more RF cable than traditional system usually, particularly when HPA is not installed in cat head.The present invention by allow base station RF interface keep relatively simple (every sector only has one or two transmitter and receiver ports) and still can interface in and utilize phased array system with six, eight or more inputs and output port, and overcome this point.
Should be appreciated that the preferred embodiment of mentioning only is illustrative for the present invention here.In view of following claim, under the situation that does not deviate from this disclosed preset range of the present invention and field, can be envisaged in has multiple change in the design and use of the present invention.