外文翻譯--天線的選擇

1、<p>　　Lee Kong Haw,華為技術(shù)有限公司</p><p><b>　　天線的選型</b></p><p>　　在移動(dòng)通信網(wǎng)絡(luò)中，天線的選擇是主要的一部分，應(yīng)根據(jù)網(wǎng)絡(luò)的覆蓋要求、話務(wù)量、干擾和網(wǎng)絡(luò)服務(wù)質(zhì)量等實(shí)際情況來(lái)選擇天線。天線選擇得當(dāng)，可以增大覆蓋面積，減小干擾，改善服務(wù)質(zhì)量。由于天線的選型是與覆蓋要求緊密相關(guān)的，根據(jù)地形和話務(wù)量的分布要求可

2、以把天線使用的環(huán)境分為城區(qū)、郊區(qū)、農(nóng)村和公路四種類型。</p><p>　　天線使用中存在的問(wèn)題</p><p>　　較少考慮實(shí)際的地形與天線方向圖的關(guān)系，而僅僅考慮覆蓋的話務(wù)量分布來(lái)選擇天線。比如在全向天線的選擇方面，全網(wǎng)都使用同一種型號(hào)的全向天線，天線高低較高時(shí)，由于垂直面波束很窄，造成“塔下黑”的現(xiàn)象。</p><p>　　在使用天線時(shí)，如果機(jī)械傾角很大，方向

3、圖就畸變，造成覆蓋或干擾的問(wèn)題。仿真表明，真對(duì)不同增益的天線，應(yīng)該有不同的下傾角限制要求。</p><p>　　過(guò)于追求天線的高增益性能，而忽略了高增益天線的一下缺點(diǎn)。導(dǎo)致幾乎全網(wǎng)使用的天線增益都很高，高增益天線的缺點(diǎn)表現(xiàn)為體積大、重量大、副瓣高、零瓣深和垂直面波束窄。</p><p>　　沒(méi)有考慮到雙極化天線和垂直極化天線在使用中的區(qū)別，只是從安裝角度考慮使用雙極化天線。</p&g

4、t;<p>　　城區(qū)基站天線應(yīng)用原則</p><p>　　在城區(qū)，由于基站分布密集，要求單個(gè)基站覆蓋范圍小，盡量減少越區(qū)覆蓋，減少基站之間的干擾，提高頻率復(fù)用率，原則上對(duì)天線有以下幾方面的要求。</p><p>　　天線水平半功率波束寬度的選擇</p><p>　　由于城區(qū)天線基站分布數(shù)量一般較多，重疊覆蓋和頻率干擾成為網(wǎng)絡(luò)中一個(gè)恒嚴(yán)重的問(wèn)題。為減少相

5、鄰扇區(qū)的重疊區(qū)，降低基站之間的可能干擾，天線的水平半功率波束寬度應(yīng)該小一些，通常選擇水平半功率波束寬度為65○的天線</p><p><b>　　天線增益的選擇</b></p><p>　　由于市區(qū)基站一幫不要求覆蓋大的范圍，因此建議使用中等增益天線，</p><p>　　這樣天線垂直面波束可以變寬，可以增加覆蓋區(qū)內(nèi)的覆蓋效果。同時(shí)，天翔體積和

6、重量可以變小，有利于安裝并降低成本。對(duì)于目前天線型號(hào)，建議市區(qū)天線增益選擇15dBi(900MHZ)15-18dBi(1800MHZ)。</p><p>　　對(duì)于城市邊緣基站，如果要求覆蓋范圍擴(kuò)大，可選用高增益天線如17dBi和18dBi.</p><p>　　原則上，在城區(qū)實(shí)際基站覆蓋時(shí)，應(yīng)選擇具有固定電下傾角的天線，下傾角的大小根據(jù)具體情況而定（建議6○－9○）。</p>

7、<p>　　在城區(qū)，為了提高頻率利用率，減小越區(qū)干擾，可以選擇上第一副瓣抑制、下第一零點(diǎn)填充的賦形技術(shù)天線。</p><p>　　由于市區(qū)基站天線安裝空間往往存在限制，一般建議選用雙極化天線。在相同貨相近電氣指標(biāo)下，應(yīng)選用尺寸較小的天線。</p><p>　　郊區(qū)基站天線應(yīng)用原則</p><p>　　在郊區(qū)，情況差別比較大，可以根據(jù)需要的覆蓋面積來(lái)估算大

8、致需要的天線類型。一般可以遵循以下幾個(gè)基本原則。</p><p>　　可以根據(jù)情況選擇水平半功率波束寬度為65○或90○的天線。當(dāng)周圍的基站比較少時(shí)，應(yīng)該優(yōu)先選用水平半功率波束寬度為90○的天線。</p><p>　　若周圍基站天線分布很密集，可以參考城區(qū)基站天線選擇原理進(jìn)行處理。</p><p>　　考慮到將來(lái)的平滑擴(kuò)容，一般不建議采用全向天線。</p>

9、;<p>　　鄉(xiāng)村基站天線應(yīng)用原則</p><p>　　在鄉(xiāng)村環(huán)境下，一般話務(wù)量較小，而且較分散，部分站點(diǎn)要求覆蓋廣，天線應(yīng)用時(shí)應(yīng)遵循以下原則。</p><p>　　考慮到建設(shè)成本，對(duì)覆蓋要求小、話務(wù)量低的站點(diǎn)建議采用全向基站覆蓋。但是全向基站天線由于增益低，覆蓋距離不如定向天線遠(yuǎn)。當(dāng)基站要去覆蓋距離較遠(yuǎn)時(shí)，則需要采用定向天線來(lái)實(shí)現(xiàn)覆蓋。建議采用水平半功率波束寬度為90○，且

10、增益較高的垂直極化天線。</p><p>　　需要注意的是，如果基站位置過(guò)高，而需要覆蓋的區(qū)域位置較低（傾角大于5○），當(dāng)采用全向天線時(shí)，可以考慮采用預(yù)置下傾或零點(diǎn)填充特性的全向天線來(lái)改善這些地區(qū)的覆蓋，避免可能出現(xiàn)的“塔下黑”現(xiàn)象和覆蓋不均勻而產(chǎn)生的信號(hào)波動(dòng)現(xiàn)象。</p><p>　　公路覆蓋天線應(yīng)用原則</p><p>　　對(duì)于公路覆蓋地區(qū)，天線的選用原則如下：

11、</p><p>　　對(duì)以覆蓋鐵路、公路沿線為目標(biāo)的基站，可以采用窄帶波束的定向天線；</p><p>　　如果覆蓋目標(biāo)為公路及周圍零星分布的村莊，可以考慮采用全向天線；</p><p>　　如果覆蓋目標(biāo)僅為高速公路，則可以考慮勇8字型天線，這樣可以節(jié)約基站的數(shù)量，實(shí)現(xiàn)高速公路的覆蓋。</p><p>　　如果是對(duì)公路以及公路一側(cè)城鎮(zhèn)的覆蓋，

12、可以根據(jù)情況考慮用水平半功率波束寬度為210○的天線來(lái)進(jìn)行覆蓋。</p><p>　　建議在進(jìn)行高速公路的覆蓋上有限考慮8字型天線和210○天線。圖4－1和圖4－2分別是兩種天線的應(yīng)用示意圖。</p><p>　　圖4－1 210○天線示意圖</p><p>　　圖4－2 8字型天線示意圖</p><p><b>　　天線應(yīng)用的

13、其它考慮</b></p><p>　　上面主要給出了不同場(chǎng)合下天線選用的基本原則。實(shí)際上，天線的選用還要考慮到將來(lái)的擴(kuò)容因素和設(shè)備的基本性能問(wèn)題。</p><p>　　舉一個(gè)簡(jiǎn)單的例子說(shuō)明：</p><p>　　加入在一個(gè)小鎮(zhèn)附近的公路覆蓋選用210○的天線，采用單小區(qū)滿足覆蓋。就要考慮該地區(qū)為來(lái)話務(wù)量是否會(huì)增加，是否需要增加載頻數(shù)量來(lái)滿足擴(kuò)容需求。在一

14、般情況下，基站增加負(fù)載往往會(huì)伴隨合路方式的改變以及合路損耗的增大，因此擴(kuò)容后將會(huì)導(dǎo)致覆蓋距離下降，在天線選型時(shí)要遇見(jiàn)到這些問(wèn)題，在天線增益的選取合站型選擇上做好前期規(guī)劃。</p><p><b>　　天線選用參考</b></p><p>　　天線選用參考見(jiàn)表4－2</p><p>　　表4－2 天線選用參考</p><p&

15、gt;　　Lee Kong Haw. Huawei Technologies Co., Ltd. 公司內(nèi)部資料</p><p>　　Antenna Selection</p><p>　　The antenna selection is a very important part in a mobile communication network. The a

16、ntenna must be selected according to the actual conditions, such as coverage requirement, traffic volume, interference, and the quality of service of the network. A proper antenna can enlarge coverage area, reduce interf

17、erence, and improve the quality of service.</p><p>　　Because antenna selection is closely related to coverage requirement, the antenna application environment can be divided into four types according to land

18、forms or traffic distribution. They are: urban area, suburban area, rural area, and highroad.</p><p>　　Problems Present in Antenna Selection</p><p>　　This section introduces the problem present

19、in antenna application from the following perspectives:</p><p>　　The antenna is selected only based on the covered traffic distribution, but little consideration is given to the relationship between landform

20、s and antenna directional diagram. For example, if all antennas used in a network are of the same type, when the antenna is installed at a high position, the phenomenon of "blind under tower” will be present because

21、 the width of the beams in vertical plane is narrow.</p><p>　　Too large antenna mechanical tilt angle results in the distortion of the directional diagram. In this case, coverage problem or interference prob

22、lem will occur. Emulation shows that the restrictions on tilt angles must vary in accordance with the antennas with different gains.</p><p>　　Too much attention is focused on the high gain performance of the

23、 antenna but little attention is given to its drawbacks. As a result, the gains of almost all the antennas used in a network are quite high. A high gain antenna has many drawbacks, including large size, great weight, hig

24、h side lobe, deep zero lobe, and narrow vertical beams.</p><p>　　No consideration is given to the difference between the vertical polarization antenna and dual polarization antenna in terms of application. T

25、he dual polarization antenna is selected from the perspective of installation.</p><p>　　Principles for Selecting Base Station Antenna in Urban Areas</p><p>　　Base stations are densely distribute

26、d in urban areas. Therefore, it is required that the coverage area of each base station is as small as possible so as to reduce cross coverage and interference among base stations, and enhance frequency reuse rate as wel

27、l. In this case, an antenna must meet the following requirements in principle.</p><p>　　Selection of antenna horizontal half power beam width</p><p>　　Because a large number of base stations are

28、 distributed in urban areas, overlapping coverage and frequency interference rises as serious problems in a network. To reduce the overlapping areas of neighbor sectors and the interference between base stations, you can

29、 set the beam width of the antenna horizontal half power to a smaller value. Generally, antennas whose horizontal half power beam width is 65° are selected, but antennas whose horizontal half power beam width is abo

30、ve 90° are not selecte</p><p>　　Selection of antenna gain</p><p>　　The base stations in urban areas are not required to cover a large area, so the antennas with medium gain are recommended.

31、 Thus the antenna vertical beam can be wider, which can improve the coverage quality within the areas to be covered. In addition, the size and weight of the antenna with medium gain are small, which is helpful for instal

32、ling the antenna and reducing cost. According to present antenna specifications, antennas with a gain of 15dBi (900MHz) and 15-18 dBi (1800 MHz) are recommend</p><p>　　For the base stations on the outskirt o

33、f a city, if it is required to cover a large distance, you can select the antennas with higher gains, such as 17dBi and 18dBi.</p><p>　　In principle, when designing base station coverage in urban areas, you

34、should select the antennas with a fixed electrical tilt angle. The degrees of the electrical tilt angle can be set according to actual conditions (the recommended value is 6° to 9°).</p><p>　　In ur

35、ban areas, to enhance frequency reuse rate and reduce cross interference, you can select the shaped-beamed antenna with the first upper side lobe suppressed and the lower side lobe filled.</p><p>　　Because s

36、pace restriction is present in the antenna installation in urban areas, the dual polarization antenna is recommended. And it is better to select the antenna with a smaller size when the electrical specifications of the a

37、ntennas are the same or nearly the same.</p><p>　　Principles for Selecting Base Station Antenna in Suburban Areas</p><p>　　Because the environment is suburban areas are largely different from th

38、at in urban areas, antennas used in suburban areas can be selected according to the required coverage area. Generally, in suburban areas, an antenna can be selected according to the following principles:</p><p

39、>　　The antennas whose horizontal half power beam width is 65° or 90° can be selected according to actual conditions. If base stations are sparsely distributed, the antennas whose horizontal half power beam w

40、idth is 90° is first considered.</p><p>　　If the base stations are densely distributed, the antennas are selected by referring to the principles for selecting base station antenna in urban areas.</p&

41、gt;<p>　　Omni antennas are not recommended for the purpose of smooth expansion in the future.</p><p>　　Principles for Selecting Base Station Antenna in Rural Areas</p><p>　　In rural areas

42、, traffic volume is small and base station are sparsely distributed, so some base stations are required to cover a large area. In this case, the antennas are selected based on the following principles:</p><p&g

43、t;　　Considering the construction cost, you are recommended to select an omni antenna for the base stations whose coverage area is small and traffic volume is low. However, because the gain of the omni antenna is low, the

44、 coverage of an omni antenna is shorter than that of a directional antenna. When the base station is required to cover a long distance, the directional antenna must be selected to realize the coverage. Generally, a high

45、gain vertical polarization antenna whose horizontal half power b</p><p>　　One point needs to be noted. That is, if the base station antenna is installed at a high position, but the area needs to be covered l

46、ies in a low location (the depression angle is greater than 5°), when an omni antenna is used, the kind with a preset tilt angle or with zero point filling function are recommended to improve the coverage quality of

47、 this area. In this case, the phenomenon of “blind under tower” and the signal fluctuation caused by uneven coverage can be avoided. </p><p>　　Principles for Selecting Base Station Antenna along Highroads<

48、;/p><p>　　The principles for selecting antennas along highroads are as follows:</p><p>　　For the base stations designed to cover the areas along railways and highroads, a directional antenna with n

49、arrow beams can be selected.</p><p>　　For the base station designed to cover the highroads and the villages scattered around the highroads, an omni antenna can be selected.</p><p>　　For the base

50、 station designed to cover highroads only, an 8-shaped antenna can be selected, because the 8-shaped antenna help realize the highroad coverage with only a few base stations.</p><p>　　For the base station de

51、signed to cover the highroads and the towns on both sides of the highroads, the antenna whose horizontal half power beam width is 210° can</p><p>　　be selected according to actual conditions. It is reco

52、mmended to give the priority to the 8-shaped antenna and the 210°antenna for highroads coverage.</p><p>　　Figure 4-1shows the application of a 210° antenna.</p><p>　　Application of a 2

53、10° antenna</p><p>　　Figure 4-2 shows the application of an 8-shaped antenna</p><p>　　Application of an 8-shaped antenna</p><p>　　Other Considerations for Antenna Selection<

54、/p><p>　　Apart from the basic principles for selecting the antenna in different places are provided in the previous parts, other factors, such as system expansion and equipment performance, must be considered f

55、or antenna selection.</p><p>　　Hereunder is an example:</p><p>　　If the 210° antenna and used to cover the highroads nearby a small town, and only a cell is used to promise the coverage req

56、uirements, you should consider whether the traffic of this area will increase in the future and whether to meet the expansion requirements by adding carriers. Generally, once a carrier is added to the base station, the c

57、ombiner loss will increase, so the coverage distance will decrease after the expansion. Therefore, when selecting an antenna, you should consider these prob</p><p>　　Antenna Selection Reference</p>&l