Abstract:
The present invention relates to an economical and highly reliable receiving apparatus for receiving radio signals transmitted from a mobile communication terminal within radio zone. The receiving apparatus has antenna sections that receive radio signals transmitted from the mobile communication terminal and are provided in each of a plurality of sectors divided from the radio zone, and receiving units that are provided in each of the antenna sections and that perform a predetermined process to the radio signals received by the antenna section.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This patent application claims priority from Japanese patent application No. 2001-232929 filed on Jul. 31, 2001, the contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a receiving apparatus for receiving radio signal that is transmitted from a mobile communication terminal. More particularly, the present invention relates to a receiving apparatus having cooling section that cools receiving unit that performs a predetermined process to the radio signal. 
   2. Description of the Related Art 
   Recently, mobile communication terminals such as car phone, mobile phone of PDC (Personal Digital Cellular), or PHS (Personal Handy Phone System), are widely popularized. 
   These mobile communication terminals transmit and/or receive radio signal with radio base station. The receiving apparatus that is provided as a receiving system of the radio base station, has an antenna section, a receiving unit for performing processes such as amplification of the radio signal that is received in the antenna section, and a receipt processing circuit for performing predetermined signal processes to the radio signal that is, for example, amplified in the receiving unit. The antenna section is provided with a plurality of antennas for diversity, and a plurality of the receiving units and a plurality of receipt processing circuits may be provided, accordingly. 
   The receiving unit has receipt filter that is provided for removing interference, and amplifier for compensating reduction in noise figure caused by cable loss between the antenna and the receipt processing circuit or distribution loss to the receipt processing circuit. The receiving unit is provided near the antenna. The amplifier is, for example, low noise amplifier (LNA). 
   On the other hand, in the event that mobile communication terminal is concerned, radio zone covered by one radio base station is divided into a plurality of areas (Each of the areas is referred to as a “sector,” hereinafter.), each of which is provided with antenna section, receiving unit, and receipt processing circuit, and thereby, one radio system is constructed for every sector. 
   However, noise figure of the receiving unit is limited to about 3 db. 
   It can be considered that the noise of the receiving unit (in particular, amplifier) can be reduced by cooling the entire receiving unit in a cooler or that the noise figure is improved by about 0.5 db for the entire receiving unit by using a receipt filter that is made from high-temperature super-conductive material. 
   However, such a cooler is expensive and does not have sufficient reliability. Therefore, if the cooler is used, the receiving apparatus becomes expensive and its reliability decreases. When a radio zone is divided into a plurality of sectors, or when the radio zone corresponds to diversity, the number of the cooler increases accordingly, thereby increasing costs and decreasing the reliability. 
   SUMMARY OF THE INVENTION 
   The objective of the present invention is to provide a receiving apparatus, which is capable of overcoming the above drawbacks accompanying the conventional art. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention. 
   The receiving apparatus according to the first aspect of the present invention comprises antenna sections that are provided in each of a plurality of divided sectors of radio zone and that receive radio signal transmitted from a mobile communication terminal, receiving units that are provided in each of the antenna sections and that performs a predetermined process to the radio signal received by the antenna section, and cooling section for cooling two or more receiving units. 
   The cooling section cools the receiving units provided in a plurality of sectors. Further, the cooling section may cool the same number of the receiving units in every said sector. The antenna and the receipt filter that are provided in each of said plurality of sectors correspond to each other in the plurality of sectors, based on the operation of said antenna section and the receiving unit, and the cooling section cools the receiving units corresponding to each other between the sectors. 
   The cooling section may cool some of said receiving units among the plurality of said receiving units provided in the predetermined sector. A plurality of the receiving units may be provided in every sector and the cooling section may cool receiving unit belonging to the same sector. Further, the cooling section cools a first receiving unit provided in each of the sectors. 
   The cooling sections may be two or more. Further, the plurality of the cooling sections cool all of said receiving units provided in each of said sectors. 
   The receiving unit may have a receipt filter for filtering the radio signal. The receiving unit may further have amplifier for amplifying signal that is obtained using the radio signal. The cooling section cools at least the receipt filter included in the receiving unit. The cooling section may cool the receipt filter and the amplifier that are included in the receiving unit. At least a part of the receipt filter may be made from super-conductive material. 
   The summary of the invention does not necessarily describe all necessary features of the present invention. The present invention may also be a sub-combination of the features described above. The above and other features and advantages of the present invention will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a block diagram of the receiving apparatus according to the first embodiment of the present invention. 
       FIG. 2  shows a first example of arrangement of a cooling section of the receiving apparatus according to the first embodiment. 
       FIG. 3  shows a second example of arrangement a cooling section of the receiving apparatus according to the first embodiment. 
       FIG. 4  shows a third example of arrangement of a cooling section of the receiving apparatus according to the first embodiment. 
       FIG. 5  shows a fourth example of arrangement of a cooling section of the receiving apparatus according to the first embodiment. 
       FIG. 6  shows a fifth example of arrangement of a cooling section of the receiving apparatus according to the first embodiment. 
       FIG. 7  shows a sixth example of arrangement of a cooling section of the receiving apparatus according to the first embodiment. 
       FIG. 8  shows other embodiment of receiving unit  20 . 
       FIG. 9  shows another embodiment of receiving unit  20 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention will now be described based on the preferred embodiments, which do not intend to limit the scope of the present invention, but exemplify the invention. All of the features and the combinations thereof described in the embodiment are not necessarily essential to the invention. 
     FIG. 1  shows a block diagram showing the receiving apparatus according to the first embodiment of the present invention. Receiving apparatus  100  has antenna section  10  having diversity antenna and receiving unit  20  provided near antenna section  10 , for example, in each of the four sectors divided from the radio zone covered by one radio base station. Receiving unit  20  has receipt filter  22  for removing interference, and LNA  30  (low noise amplifier) for compensating reduction in noise figure caused by cable loss between antenna section  10  and receipt processing circuit and distribution loss to the receipt processing circuit. In this embodiment, each receipt filter  22  is made from super-conductive material. Receiving unit  20  receives radio signal transmitted from a mobile communication terminal (not shown) that exists in each sector. Antenna section  10 , receiving unit  20  and receipt processing circuit constitute one radio system for each sector. 
   Processing section  50  (shown in  FIG. 2  described below) for processing output signal from the plurality of receiving units  20  is provided, in a rear end of receiving unit  20 . Processing section  50  has receipt processing circuit and the like, and realizes diversity effect by performing predetermined processes. The antenna system for diversity is referred to as “branch.” In this embodiment, the two-branch diversity system using antenna sections  10  of branch  1  and branch  2  will be described in the following. 
   Antenna section  10 , receiving unit  20  and receipt processing circuit constitute one radio system in each sector. In the event that one receiving system consisting of one antenna section  10 , receiving unit  20  and receipt processing circuit is regarded as a receiving block, receiving apparatus  100  has a plurality of receiving blocks in each sector. As shown in the figure, receiving apparatus  100  of the first embodiment has two receiving blocks, corresponding to the two antennas for diversity. 
   In the reference symbols of x-y-f regarding receipt filter  22  and x-y-a regarding LNA  30 , “x” represents the sector number divided from the radio zone and “y” indicates the branch number of each antenna. Further, “f” means that the referenced element is receipt filter  22  and “a” means that the referenced element is LNA  30 . 
     FIG. 2  shows a first example of arrangement of a cooling section for cooling receiving unit  20 . In the first example, the radio zone covered by one radio base station is divided into four sectors. In every sector, receiving apparatus  100  has processing section  50  for processing output signal from receiving unit  20  of the two branches that received radio signal, respectively, in rear end of LNA  30  of the apparatus. Processing section  50  has receipt processing circuit and, for example, performs processes for obtaining diversity effect. Further, in every branch, receiving apparatus  100  has two cooling sections  401 ,  402  for cooling receipt filter  22  within the two receiving units  20 . Cooling sections  401  and  402  have a chamber (case) surrounding receipt filter  22  and cooler that is housed within the chamber. The chamber is maintained as being substantially vacuum. 
   In the figure, the reference symbols with respect to receipt filter  22  and LNA  30  are the same as  FIG. 1 . In the following examples, the meanings of reference symbols are the same as described above. 
   The cooler uses, for example, heat exchange cycle where helium gas is compressed and expanded and is very low temperature cooler that can maintain very low temperature of dozens of Kelvin (K) for long time. 
   In the first example, one cooling section  401  or  402  cools two receipt filters  22  of  1 - 1 - f  and  2 - 1 - f  among each receiving unit  20 . Cooling sections for cooling other receipt filter  22  (for example,  3 - 1 - f  and the like) and LNA  30  are not provided. That is, all LNAs  30  may be used in the room temperature or higher temperature than the temperature within the cooling section. 
   In the first example, since one cooling section  401  or  402  cools two receipt filters, noise figure of the received signal can be improved and the numbers of cooling sections can be decreased compared to the conventional structure in which one cooling section cools one receipt filter  22 , thereby saving the cost. 
   Further, the cooling section is provided in every branch. Generally, since the cooling sections in both branches usually do not malfunction at the same time, even if a cooling section in one branch becomes malfunction, the cooling section in the other branch would normally operate. Thus, the performance of a radio system of each sector does not fallen off drastically. (This is referred to as “unique effect of the first embodiment”, hereinafter.) 
     FIG. 3  shows a second example of arrangement of a cooling section of receiving apparatus  100  of the first embodiment. Receiving apparatus  100  has cooling sections for cooling receipt filter  22  within two receiving units  20 . That is, the number of cooling sections provided in each branch is determined so that all of receipt filters  22  belonging to a plurality of sectors can be cooled. (In this example, the number of cooling sections is two for each branch.) Cooling sections  411 ,  412 ,  421 ,  422  cool the same number of receipt filter  22 , respectively. On the other hand, cooling section for cooling each LNA  30  is not provided. That is, all LNAs  30  may be used in the room temperature or higher temperature than the temperature within the cooling section. 
   In the second example, the number of cooling sections can be lowered compared to the conventional structure in which one cooling section is required to cool one receipt filter  22 , thereby saving the cost, as in the first embodiment. Further, in the second example, since the cooling section is provided in every branch, the unique effect of the first embodiment also can be provided. 
     FIG. 4  shows a third example of arrangement of a cooling section of receiving apparatus  100  of the first embodiment. Receiving apparatus  100  has two cooling sections  451 ,  452  that cool receipt filter  22  within two receiving unit  20  belonging to one sector, along with cooling receipt filter  22  within the receiving unit belonging to the other sector. That is, the number of cooling sections (in this example, two) to be provided is determined so that all of receipt filters  22  belonging to a plurality of branches and sectors can be cooled. Cooling sections  451 ,  452  cool the same number of receipt filter  22 , respectively. 
   The third example can provide the same effects of the second example. However, since one cooling section cools receipt filters  22  in all branches within the sector at the same time, the unique effect of the first embodiment cannot be provided. However, the number of the cooling sections can be decreased. 
     FIG. 5  shows a fourth example of arrangement of a cooling section of receiving apparatus  100  of the first embodiment. Receiving apparatus  100  has cooling sections  401 ,  402  for cooling receipt filter  22  and LNA  30  within two receiving units  20  in each branch. In the fourth example, cooling section  401  cools receipt filters  22  of  1 - 1 - f  and  2 - 1 - f  and LNA  30  in each receiving unit  20 . Cooling section for cooling other receiving units  22  (such as  3 - 1 - f ) and LNA  30  (such as  3 - 1 - a ) is not provided. 
   In the fourth example, since one cooling section  401  cools two receipt filters  22  and LNA  30 , i.e., since a cooling section cools LNA as well as receipt filter, noise figure of the received signal can be more improved compared to the first to third examples. 
   Further, since the cooling section is provided in each branch, the fourth example can provide the unique effect of the first embodiment. 
     FIG. 6  shows a fifth example of arrangement of a cooling section of receiving apparatus  100  of the first embodiment. Receiving apparatus  100  has four cooling sections  411 ,  421 ,  412 ,  422  for cooling receipt filter  22  and LNA  30  within two receiving units  20 . That is, the number of cooling sections are determined so that all of receipt filters  22  and LNA  30  that belong to a plurality of sectors can be cooled. The cooling sections cool the same number of receipt filter  22  and LNA  30 , respectively. 
   The fifth example also provides cost reduction as the above-mentioned examples in cost reduction, since the number of cooling sections is decreased compared to the conventional arrangement in which one cooling section is required to cool one receipt filter  20 . Since the cooling section is provided in each branch, in the fifth example, the unique effect of the first example also can be provided. 
     FIG. 7  shows a sixth example of arrangement of a cooling section of receiving apparatus  100  of the first embodiment. In the sixth example, cooling sections  451 ,  452  of the third example are modified to cool LNA  30  as well as receipt filter  22 . The sixth example provides the same effects as the third example. 
   In the first embodiment, it is described that the cooling section cools a plurality of receipt filters  22  and/or LNA  30 . However, other embodiment may be possible as long as each of the cooling section cools two or more receiving units. For example, if each of the receiving units includes receipt filter and amplifier, the cooling section may cool at least one of the receipt filter and the amplifier in the receiving unit. 
   Although the present invention has been described by way of exemplary embodiments, the scope of the present invention is not limited to the embodiments. Those skilled in the art might make many changes and improvements. It is clearly understood from the claims that the changes and improvements fall within the scope of the present invention. 
   In the first, second, third, fourth, fifth and sixth examples, the object to be cooled is combinations of sectors  1  and  2 , and sectors  3  and  4 . However, the object to be cooled maybe combinations of sectors  2  and  3 , and sectors  1  and  4 . 
   Further, in the examples, receiving unit  20  consists of receipt filter  22  and LNA  30 . However, as shown in  FIG. 8 , the receiving unit may include a circuit where receipt filter  22 , isolator  24  (using symbol of  1 - 1 - ai  and the like) and amplifier  30  are connected in series. Further, as shown in  FIG. 9 , the receiving unit may include a circuit wherein distributor  26  (indicated by reference symbol of  1 - 1 - b  and the like) and synthesizer  28  (indicated by reference symbol of  1 - 1 - g  and the like) are arranged in this order and a plurality of amplifiers  30  (for example, two) are parallel connected between distributor  26  and synthesizer  28 . It is shown in  FIGS. 8 and 9  that only receipt filter  22  is cooled by cooling sections  401 ,  402 , but amplifier  30  also may be cooled. Further, the entire receiving unit including isolator  24  and distributor  26  and the like may be cooled by cooling section  401 ,  402 . 
   According to the receiving apparatus of the present invention, the number of cooling sections (that is, cooler) can be decreased compared to the conventional arrangement in which one cooling section is required to cool one receipt filter, and thus the cost can be saved. Further, in the event that the cooler is provided in each branch, even if a cooler of a branch becomes disabled, the system is prevented from stopping since the cooler of the other branch would operate.