Abstract:
A combination structure of radio front end and antenna for wireless base station and a means of share the antenna for multiple carriers are presented. The front part of the antenna has several independent radiation units for spatial combining radiation of multiple carriers. There is a heat dissipation cavity with natural air flow in back part of the antenna. The radio front end circuits formed a module with heat sink panel are installed in the cavity and on the back panel of the antenna.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a structure design of radio front end and antenna for mobile base station, and a means of share the antenna for multiple carriers. 
       BACKGROUND OF THE INVENTION 
       [0002]    The radio front end of the traditional mobile base station (BS) required power amplifier (PA) with big RF power output. The power consumption of the BS is quite large because: 1. Very low power efficiency of the PA itself but large output power is required. The power efficiency of the PA itself is less than 50% for GSM and about 25% for CDMA and OFDM even using last technology with big cost, complexity and low reliability. For example, 100 W PA release 100 W or 300 W heat; 2. There is large insertion loss by coax cable between antenna and RF front end of the BS. For example, 80% of antenna tower in North America is 30˜50 m high. The cable with two jumpers and several connectors including inside connectors in cabinet of the BS has total 5˜7 dB insertion loss that means 70˜80% RF power became heat; 3. To multiple carriers GSM base station, each carrier needs to be amplified by one itself PA and then be combined to one channel by several combiners. The combined signal is transferred to antenna from BS by a costly, thick, heavy, low loss cable. For example by four carriers GSM BS, combining of the carriers transfer 80% the RF power to heat which is increasing as the number of the carrier is increasing; 4. The fan, exchanger even air conditioner inside of BS are required to dissipate the heat. Especially strong cooling air flow is required for PA because mass heat is concentrated in tiny area, which is much more difficult to dissipate compare with normal electrical circuits. 30% extra heat is distributed typically by fan system and power supply system. 70% of power consumption of BS is come from requirement of PA. Only 2.5% less of the energy consumed by PA become effective radiation power in the antenna port. The 97.5% of the electrical power is transformed to harmful heat inside of the BS which creates very low efficiency and very low reliability as a whole of the BS. The failure rate of the PA module because the high temperature and the failure rate of the fan are highest compared with failure rate of other parts of the BS. The cost, weight, size, power consumption, noise and maintenance frequency of BS are increased dramatically. It is much harder and harder to install the BS in the rooftop of the resident building. The fee for installation place is increasing very fast even higher than BS equipment cost in some area. 
         [0003]    The auto-tuned cavity combiner can reduce the insertion loss but can not solve the all problems synthetically and go with high cost. The remote radio unit (RRU) could reduce the cable insertion loss but ten thousands of components per sector are placed in cabinet with high temperature PA on tower top, as result of which the feasibility to install the RRU on tower top, reliability, maintain ability and cost to clamber tower are all became serious problems. The operators in the Occident would rather put the RRU on the ground than the tower top to avoid excessive failure time and upkeep. 
         [0004]    The purposes of the invention are: 1. Avoid the cable loss to upgrade the PA efficiency of normal wireless BS while reduce the complexity of the equipment installation on tower top and ensure the high reliability and easy maintenance; 2. The PA are separated from BS cabinet to reduce 70% heat of the main cabinet. The system of the heat dissipation can be simplified, the power of the power supply can be reduced, the size and weight of the BS cabinet can be much smaller, and the system reliability will be much higher; 3. The PA with much less power as tenth than normal is used. The natural heat dissipation by fully utilizing of previous mechanical structure of the antenna is adopted to avoid use of low reliable turning parts like fan and heavy heat sink. The total weight of the equipment is reduced and the reliability of the tower equipment is increased; 4. The combiner is not used or less used for multiple carriers GSM BS to farther increase the efficiency of the GSM BS; 5. The coax cable with large diameter which is heavy, costly, hard to install and easy to fail is avoided; 6. The radiation power and the electrical down tilt of the sub-antenna for different carrier with specified zone are set differently according the distance of the specified zone and traffic, by which the less power is consumed by BS, less co-channel interference of wireless net is created so that the data rate can be higher and communication quality is better. On all accounts, 70% of the power consumption of the whole system is saved; the communication reliability is increased; the weight, size, heat, noise, CAPEX, failure rate, failure time and OPEX of the mobile BS will be reduced dramatically. 
         [0005]    The most techniques of the invention can be used for any standard of wireless communication BS. 
       SUMMARY OF THE INVENTION 
       [0006]    It is a primary object of the present invention to provide a structure design of the radio front end and antenna for BS to reduce the cost, heat and failure rate. The special designs are 1. The radio front end parts are moved out from BS. Several special designed RF modules composed of much smaller power PA or LNA or some other structures, are installed in back panel of the antenna with hot swap function; 2. The back mechanical structure of the antenna is modified to a special cavity for natural heat dissipation of the RF modules; 3. Adopt directional antenna with dual rows and dual polarizations to combine carriers in space instead of traditional combiner; the two rows of vertical array have different electrical down tilt; 4. Adopt a cable bundle with several thin cables instead of traditional very thick cable. According this project, each carrier is amplified itself by one small PA. The small PA is installed in back panel of antenna on tower top instead of in tank of BS on ground. The power requirement of PA has inverse ratio with number of carriers. Take example by four carriers BS, 7 dB loss is for combine of four carriers, 5 dB is for cable loss so that four of small PA with one fifteenth power of the traditional PA can be used, which are easily to installed to back panel of antenna from the view of weight, size, heat and reliability. 
         [0007]    The antenna adopted in this project has dual rows and dual polarizations which are isolated each other to form four independent sub-antennas. The each polarization of the each row produces one radio beam with 65 degree or 90 degree of beam width. Total four independent beams are created and corresponded to the four independent sub-antennas. 
         [0008]    When one or two carriers are used, the output ports of one or two PA are connected to one or two feed ports of the dual polarization of one row of the antenna. The input ports of the one or two PA are connected to relative ports of the cable bundle. The two ports of the dual polarization of another row of the antenna are connected to two input ports of the two LNA to make diversity receiving. 
         [0009]    When the number of the carriers is more than two, the RF front end module (RFE) composed of one PA, one LNA and two duplexers with two ports is required. The RFE has one port to share one sub-antenna for both transmitter and receiver and another port to share one thin cable for signal transfer between RFE and BS. For example, one RFE instead of one LNA is required for share one antenna for both PA and LNA in another row of the antenna when three carriers are used. For same reason, two RFE are used to instead of the two LNA when the BS is working in four carriers. 
         [0010]    Each RF module is waterproofed and installed independently in back panel. A cool waiting structure designed for redundancy of each PA module is doable because the very low cost of the small PA. 
         [0011]    One traditional directional antenna with dual polarization came with one or two RFE modules are doable if the number of the carriers is less than three in future plan. Otherwise, the directional antenna with dual rows and dual polarizations is the better choice. 
         [0012]    Because the cost is much lower, the more power amplifiers, more cables than requirement can be preinstalled in the back panel of the antenna to create RFE channel redundancy which can add the system reliability, reduce the maintenance requirement on tower top and the failure time of the wireless net dramatically. 
         [0013]    If five to eight carriers are used, the PA module or RFE module with dual PA is required. Two PA are replaced one PA with a combiner to form a PA with dual-PA module or RFE with dual-PA module. The dual-PA module now has two ports in cable end but still has one port in antenna end. The cable bundle could be preset up to eight thin cables inside for possible future carrier upgrade. Under the structure of this project, carrier upgrade of the radio front end from one to eight or even more is simple by increase or change of PA module, RFE module or dual-PA module depending on the number of the carriers. These RF modules are installed in back panel of the antenna individually and very easy to exchange by hot swap on tower top without any disturbing to the communication. 
         [0014]    The tuning and retuning of the output power for each carrier is easy and flexible because all of the PA modules are installed separately and independently and also easy to change. The radiation powers for different carriers with specified zone can be set differently according the distance of the specified zone and traffic. The larger power is set to the carrier to respond the terminals from far zone for which the sub-antenna with smaller electrical downtilt is used. The smaller power is set to the carrier to respond the terminals from near zone and the sub-antenna with larger electrical downtilt is adopted. One large power and one small power are separately adopted by two opposite sectors with same reused frequency but being separated by other cells. The arrangement of the different power and different antenna downtilt can reduce the power consumption, co-channel interference and radio pollution to increase communication capacity and quality. The output power can be remote tuned by set up different DC bias of the PA. 
         [0015]    The radiation unit in front part of the antenna is independent and waterproofed. The air tunnel is formed by the back cavity of the antenna with opened up side and down side. The cooling air flow from bottom to top is created naturally when the PA modules installed inside of the cavity are working. The air tunnel is rainproof. 
         [0016]    The PA module or RFE module is combined with heat sink panel to form the PA-Heat sink module or RFE-Heat sink module (simplify to RF-Heat sink module). Some heat pipe could be installed in the heat sink panel if the PA is quite large or the average temperature of the local weather is very high. 
         [0017]    Several installation windows are preset in the back panel of the antenna. The RF-Heat sink modules are installed in these windows by screws or other mechanical method. The connections between the RF module and antenna could be two or three short RF cables or RF penal jack by hot swap to simplify the module exchange. 
         [0018]    There are two or three RF sockets in the back face of the ground panel of the radiator corresponding to each back panel window. One socket is inside connected to the radiator feeding port of one independent antenna above mentioned. Other one or two sockets are inside connected to the antenna feeding socket fixed in back panel of the antenna. The front panel of RF module has two or three RF plugs in correspond locations of the RF sockets above mentioned. One plug is inside connected to PA output. Other one or two plugs are inside connected to PA input or dual-PA inputs. These connectors are waterproofed. 
         [0019]    The electrical connecting, VSWR testing and mechanical fixing between these RF-Heat sink modules, antenna and maybe the cable bundle are all finished in manufactory to ensure the high reliability of the connections. The redundant carrier PA, RFE channels have been preset therefore the changing of the RF module on tower top is only happened when the extra carrier upgrade is required or more than one or two modules are failed which has a little chance. The module exchange is very simple and easy without any variation of antenna stance and performance. Hot swap is feasible without any impact to the communication state. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0020]    Preferred embodiments of the invention are described herein below with reference to the drawing wherein: 
           [0021]      FIG. 1  is a block diagram of a traditional structure of PA and antenna for four carriers BS; 
           [0022]      FIG. 2  is a block diagram of an inventional structure of PA and antenna for four carriers BS; 
           [0023]      FIG. 3  is a block diagram of a PA redundant module including a cool waiting PA; 
           [0024]      FIG. 4  is a block diagram of a working mode of RFE and antenna for one or two carriers BS; 
           [0025]      FIG. 5  is a block diagram of a RFE module structure; 
           [0026]      FIG. 6  is a block diagram of a working mode of RFE and antenna for three or four carriers BS; 
           [0027]      FIG. 7  is a block diagram of a dual-PA module; 
           [0028]      FIG. 8  is a block diagram of a working mode of RFE and antenna for five or six carriers BS; 
           [0029]      FIG. 9  is a side view of an invention antenna; 
           [0030]      FIG. 10   a  is a top view of the invention antenna; 
           [0031]      FIG. 10   b  is a top view of the inventional antenna with an extra heat sink panel; 
           [0032]      FIG. 11  is a side view of an electrical connection configuration between RF module and antenna; 
           [0033]      FIG. 12  is a front view of a back panel of the inventional antenna with installation windows; 
           [0034]      FIG. 13  is a front view of the back panel with windows and RF/Heat sink modules installed on the windows; 
           [0035]      FIG. 14  is a side view of a RF module with a heat sink panel installed on the back panel of the antenna; 
           [0036]      FIG. 15  is a front view of the RF module with the heat sink panel which has heat pipes in it; 
           [0037]      FIG. 16  is a top view of the RF/heat sink module installed on the back panel of the antenna; 
           [0038]      FIG. 17  is a side view of a RF module with a heat sink panel and a window panel installed on the back panel of the antenna; 
           [0039]      FIG. 18  is a front view of the RF module with the heat sink panel installed heat pipes on it, and the window panel; 
           [0040]      FIG. 19  is a top view of the RF/heat sink/window panel module installed on the back panel of the antenna; 
           [0041]      FIG. 20  is a side view of a RF module with a heat sink panel, some metal rails and a window panel installed on the back panel of the antenna; 
           [0042]      FIG. 21  is a front view of the RF module with the heat sink, the metal rails and the window panel; 
           [0043]      FIG. 22  is a top view of the RF/heat sink/rail/window panel module installed on the back panel of the antenna; 
           [0044]      FIG. 23  is shown that each sub-antenna of the base station is set to different radiation down tilt and power for different carrier. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0045]    In the traditional structure of the four carriers GSM BS illustrated on the block diagram of  FIG. 1 , transmitter  6  supplies four driving carriers to the four of high-power PA  5  separately and the four powered carriers are combined to one channel by three combiners in the BS cabinet  3  on the ground. The combined four carriers are transferred to the directional antenna  1  by the thick coax cable  2 . 
         [0046]      FIG. 2  illustrates the improved structure by this invention in which there is no any large PA  5  in the BS cabinet  29  on the ground. Through connector  27 , four cables of cable bundle  26  and connector  25 , the transmitter  28  in BS cabinet  29  supply four driving carriers to four of small-power PA  24  installed on back panel of the antenna  21 . The antenna  21  is composed of front part and back part. The front part is the radiator made of two independent vertical arrays  22  in which each element is made of two cross polarized generator  23 . The four independent sub-antennas are formed by the four vertical series of generator  23 . The four feed ports of the sub-antennas are connected to the four outputs of the PA  24 . The four PA are installed in the back part of the antenna. The two independent vertical arrays  22  can be arranged by horizontal or by vertical. More than two of the vertical arrays maybe are required which could be arranged by both horizontal and vertical. 
         [0047]    With a cool waiting PA part, the Redundant PA module  32  illustrated in  FIG. 3  has higher reliability which is composed of two switches  31  and two PA  24 . The Redundant PA  32  is a good choice because the low PA cost and high reliability. The redundant structure is suitable to other types of RF module mentioned later. 
         [0048]    The RFE/Antenna structure  21  illustrated in  FIG. 4  is working as mode of one or two carriers. The two groups of cross polarized generators  23  in the left vertical array  22  and one or two PA  24  are formed one or two carrier transition units. The two groups of cross polarized generator  23  in the right vertical array  22  and two LNA  41  are formed two diversity receiving units. They are connected to transceiver  28  in BS  29  through connector  25 . 
         [0049]    A RFE module  52  made of one PA  24  or  32 , one LNA  41  and two duplexers  51  is used for share one sub-antenna  23  by both transmitting and receiving when the number of carrier is more than two, which is illustrated in  FIG. 5 . 
         [0050]    One LNA  41  illustrated in  FIG. 4  is replaced by one RFE  52  to share one sub-antenna  23  for both transmitting and receiving when the system is working in mode of three carriers. Two LNA  41  are replaced by two RFE  52  to share two sub-antennas  23  for two carriers as illustrated in  FIG. 6 . 
         [0051]    A Dual-PA module  72  is illustrated in  FIG. 7  which is composed of two PA  24  and one combiner  71  to use for share one generator  23  by two carriers. The module has two input ports and one output port. By same logic, a Dual-PA/RFE module has similar structure. 
         [0052]    When five carriers are adopted, two RFE module  52  are used on the right array of the antenna to amplify two carriers and two receiving signals through the two sub-antennas. On the other hand to the left array, one module is PA  24  to amplify one carrier, another is dual-PA  72  to amplify two carriers but through only one sub-antenna, so that five carriers are amplified as illustrated in  FIG. 8 . Six carriers can be amplified if the two modules of the left side are both dual-PA. 
         [0053]    Anyhow seven, eight even more carriers can be handled by same logic. 
         [0054]    Side view of the antenna  21  is illustrated in  FIG. 9  with front part and back part. The front part in left side of the antenna is radiator  91  in which the electrical structure is illustrated in  FIG. 2 . The back part of the right side of the antenna  21  is composed by ground panel of radiator  91 , back panel  92  of the antenna  21  and cavity  93  by the enclosure structure  91 ,  92 ,  99 A,  99 B and side wall. The cavity is closed surrounding but opened for up side and down side to form an air tunnel  93  in which air flow from bottom to top is created when the PA modules are working. The top side and bottom side are blocked by two screens  99 A,  99 B. The modules  24 ,  32 ,  41 ,  52 ,  72  mentioned above are defined as RF module  95  in  FIG. 9  and installed in separate places of the cavity for easy to heat dissipation. A RF socket  97  is installed on the back panel  92 , which is connected to one feed port of RF module  95  by cable  96   a  and connected to feed port of BS  29  by cable bundle  98 . Another port of the RF module is connected to one feed port of one sub-radiator  91  through cable  96   b.    
         [0055]    The RF module  95  is installed on back panel  92  which is illustrated in top view of  FIG. 10   a.  The back panel  92  acts as heat sink of PA also. 
         [0056]    The other top view of  FIG. 10   b  shows different structure in which RF module  95  is not installed in back panel  92  directly but in a special heat sink panel  101  which is fixed in back panel  92 . The back panel acts both heat sink and havelock. 
         [0057]      FIG. 11  shows an electrical connection between RF module and sub-antenna.  112  are two RF plugs on RF module.  111  are two RF sockets on ground panel of radiator  91 , by which one sub-antenna  23  and one sub-connector of the RF socket  97  on the back panel are connected inside of the antenna. 
         [0058]    The front view of back panel  92  is illustrated in  FIG. 12 . There are four windows  121  on the panel for installation of RF module  95  and its heat sink panel. The size and arrangement of the windows  121  on the panel  92  are different depended the shape of the antenna and the heat amount of the PA. For example, one vertical series of the windows arranged from top to bottom of the panel can be used in slightness antenna. 
         [0059]    The four windows  121  of the back panel  92  with installed RF module  95  and its heat sink panel  131  are showed in  FIG. 13 . 
         [0060]    Side view and top view of the installation of a RF module  95  in a window  121  of the antenna  21  shown in  FIG. 14  and  FIG. 16  is showed that a RF module  95  and its heat sink/window panel  141  are fixed on antenna back panel  92  and ground panel of the radiator  91  through fix bolts  142 , back-up washers  143 . The materiel of the all parts is metal with good thermal conductivity. The thermal resistance of the interfaces between the parts is designed as small as possible. The connection between module  95  and radiator  91  could be short cables  96  or one pair of RF jack and socket by which a direct hot swap of RF module is used for changing of the RF module  95 . The connections of cables  96  are described in  FIG. 9 . 
         [0061]    The RF/heat sink module made of RF module  95  and window/heat sink panel  141  is shown in  FIG. 15  by front view. Part  152  are heat pipes which could be installed in panel  141  depended on heat situation. Screw holes  151  are used to fix the panel  141  to window  121  of the panel  92 . Other configuration of RF/heat sink module and its installation is illustrated in  FIG. 17 ,  FIG. 18  and  FIG. 19 . The difference compared with structure shown in  FIG. 14  is that the heat sink  141  is not fixed to the back panel  92  directly but to a special window panel  171  through some back-up washers or metal supporters  172 . The window panel  171  is fixed to the back panel  92  by screw  142 , supporter  143  and acts as second heat sink and havelock. The configuration has larger area to heat dissipation and less sun heat but more weight. 
         [0062]      FIG. 20 ,  FIG. 21  and  FIG. 22  illustrate one modified configuration compared with above design, in which the supporters  172  are replaced by several metal rails  201  which acts as heat sink, thermal conductor and supporter. The new structure has smaller thermal resistance. 
         [0063]      FIG. 23  illustrate that each sub-antenna  21  above mentioned of each base station ( 300 ,  301 ,  302 ) is set to different radiation down tilt and power for different carrier separately. Base station  300  reuses the same frequency pair with the base station  302  correspondingly which is separated with base station  300  by other base station  301 . The real red line and the real blue line represent the two different carriers. The dot line of red or blue represents the co-channel interference of each carrier in opposite sector correspondingly. The base station  300  uses red line carrier with smaller down tilt and larger power to handle the mobile stations in far zone of the sector but uses blue line carrier with larger down tilt and smaller power to process the mobile stations in near zone of the same sector. Contrariwise, the base station  302  uses blue line carrier with smaller down tilt and larger power for the far zone and uses red line carrier with larger down tilt and smaller power for the near zone. Obviously by using the new antenna structure and frequency plan the smaller co-channel interference and radiation pollution of the wireless network can be achieved by which the data transportation rate and network capacity should be increased.