Technical Field [0001] The present invention relates to a tuner module and a receiving apparatus capable of being applied to, for example, a television tuner. Background Art [0002] In recent years, television (TV) tuners, which are an example of a high-frequency module, have been embedded in IT devices such as personal computers (PCs) as well as TV receivers. [0003] For example, a first example of a shape of a TV tuner and a method of mounting the TV tuner is disclosed in Patent Literature 1 and a second example thereof is disclosed in Patent Literature 2. [0004] In the first example, in a tuner, a circuit board having electronic parts mounted thereon is embedded in a metal shield housing, and a connector for a connection of a cable from an antenna is fixed to the shield housing. In the tuner, terminals are mounted on the circuit board in the shield casing, drawn toward the outside of the shield housing, and connected and fixed to a mounting board. [0005] In this shape, in a design for an assembly with the outside of the housing, parts connected to the outside, such as the shape of the tuner, an arrangement of the terminals, and a position of the antenna connector, are fixed. This shape is a shape of a tuner used for a general TV. [0006] 3/18 In the second example, a part of a shield cover covering a thin board for a tuner is coupled with an engagement hole provided in a main board (mounting board) on which a tuner module is mounted. Accordingly, a shield housing having a 3-piece configuration as in the first example is unnecessary, the tuner can be mounted on the main board using a simple method, and noise entering from the outside can be eliminated using a low cost method. Citation List Patent Literature [0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 2003-309477 Patent Literature 2: Japanese Patent Application Laid-Open No. 2003-143024 Summary of Invention Technical Problem [0008] However, in the first example described above, when the position of the antenna connector is changed without changing a basic internal circuit on a design of an entire TV or when it is necessary to change positions of contact terminals or an arrangement number, the tuner is often re-designed as a similar but different tuner. That is, it is necessary to change or newly create a mold for a press process used to make the shield housing or to change adjustment equipment according to the terminal arrangement. Thus, in the shape of the tuner of the first example, a degree of freedom of a mechanism design is low, many types of models with a small change as in the example are created, and much design effort is consumed. [0009] However, in the second example, the antenna connector shown in the first example is not included. That is, parts related to an internal tuner circuit and an internal module board covered with the shield housing are less susceptible to a noise, but since there is no description of the 4/18 antenna connector part, a shape of the connector is unclear. [0010] In general, in an F or IEC type plug used for an antenna connector of a TV tuner, a core is not covered with a shield cover or a coating except in special cases, and is fixed to the casing and used as in the first example. In this case, even when the core is not coated with a particular coating, there is no problem since the core is covered with the shield casing together with a circuit board inside the tuner. [0011] However, in the second example, there is no connector mounting structure and no electrical resistance against entering noise is known. In this case, a connection is made using a coated cable including the antenna connector, but it takes much time to make the antenna connector with the coated cable. In most cases, the antenna connector with the coated cable is manually made and becomes very expensive. [0012] As described above, in the TV tuner structure using a related art, there remain disadvantages such as great limitation of an actual use state as well as the shape of the tuner, and high cost necessary for a mounting shape of the antenna connector even when the structure is small and thin. [0013] The present invention provides a tuner module and a receiving apparatus capable of providing great degrees of variation and freedom to a layout in a main board, improving a degree of freedom of design, and achieving low cost. Solution to Problem [0014] According to a first aspect of the present invention, there is provided a tuner module including: a tuner module board on which a tuner functional unit is formed; a main board on which the tuner module board is surface-mounted; and a shield casing including at least one antenna connector, arranged to cover the surface-mounted tuner module board, and fixed to 5/18 the main board. Preferably in the shield casing, a length of a longest long-side is a length equal to or less than 1/4 of a wavelength of a highest received frequency in the air. Preferably in the inside of the shield casing, a partition area having a plurality of partitions formed by inner walls is formed, and a length of a long side of a longest inner wall is a length equal to or less than 1/4 of a wavelength of the highest received frequency in the air. Preferably in the antenna connector, a length of an exposed core is a length equal to or less than 1/4 of a wavelength of a highest received frequency in the air. [0015] According to a second aspect of the present invention, there is provided a receiving apparatus including: an antenna connector connected to an antenna that receives a broadcast wave signal; a tuner module including a frequency conversion function for the broadcast wave signal received via the antenna connector; and a demodulation unit for demodulating the frequency-converted broadcast wave signal, wherein the tuner module includes: a tuner module board on which a tuner functional unit including the frequency conversion function is formed; a main board on which the tuner module board is surface-mounted; and a shield casing including at least one antenna connector, arranged to cover the surface-mounted tuner module board, and fixed to the main board. Advantageous Effects of Invention [0016] According to the present invention, it is possible to provide great degrees of variation and freedom to a layout in a main board, improve a degree of freedom of design, and achieve low cost. Brief Description of Drawings [0017] [Fig. 1] Fig. 1 is a view showing a configuration example of a tuner module according to a first embodiment of the present invention. [Fig. 2] Fig. 2 is an illustrative view of end surface through-holes. 6/18 [Fig. 3] Fig. 3 is an illustrative view defining a length of a core of an antenna connector in the present embodiment. [Fig. 4] Fig. 4 is a view showing a configuration example of a tuner module according to a second embodiment of the present invention. [Fig. 5] Fig. 5 is a view showing a configuration example of a tuner module according to a third embodiment of the present invention. [Fig. 6] Fig. 6 is a diagram showing a configuration example of a receiving apparatus that employs the tuner module according to the present embodiment. Description of Embodiments [0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings throughout which like parts are referred to by like references, and in which: Further, a description will be given in the following order. 1. First embodiment (first configuration example of tuner module) 2. Second embodiment (second configuration example of tuner module) 3. Third embodiment (third configuration example of tuner module) 4. Fourth embodiment (configuration example of receiving apparatus) [0019] <1. First Embodiment Fig. 1 is a view showing a configuration example of a tuner module according to a first embodiment of the present invention. [0020] A tuner module 10 according to the first embodiment includes a tuner module board 11, a main board 12, a shield casing 13, and an antenna connector 14 (-1 to -4). [0021] In the tuner module board 11, for example, a circuit is formed as a functional unit of a television (TV) tuner module. This tuner module board 11 is surface-mounted on the main board 12. [0022] 7/18 The shield casing 13 is formed in a hollow rectangular parallelepiped shape having an opening 13a formed in one face (bottom). At least one antenna connector 14 is fixed to the shield casing 13 by mating caulking, and the shield casing 13 is arranged to cover the surface-mounted tuner module board 11 and fixed to the main board 12, for example, by soldering. [0023] For the shield casing 13 of the present embodiment, a metal generally called nickel silver is used, which is a thin material and is an alloy of copper, nickel and zinc having excellent solderability. However, since there is no problem as long as conductivity is excellent, an inexpensive tin material or something similar may be used as the shield casing 13 if the shape of the shield casing 13 is less limited. [0024] At least one antenna connector 14 is fixed to the shield casing 13 of the present embodiment by mating caulking, as described above. In the present shield casing 13, antenna connectors 14-1 to 14-4 may be fixed to side faces 131, 132 and 133 at end sides and an upper face 134 in a fixed state through a caulking process. The antenna connector 14 of Fig. 1 has a caulking part 141 folded toward the inside of the shield casing 13. The antenna connector 14 is fixed in such a manner that a metal plate constituting the shield casing 13 is sandwiched between this caulking part 141 and a part of the antenna connector 14 outside the shield casing 13. This method is called a caulking process and is used similarly in other embodiments. [0025] The core 15 of the antenna connector 14 is a signal input terminal in a hole 16 positioned with the tuner module board 11 on the main board 12, and is electrically connected to the tuner module board 11 by a pattern on the main board 12. Further, in the example of Fig. 1, a state in which the antenna connectors 14-2 to 14-4 are fixed to the shield casing 13 by the same mating caulking is depicted. Although not shown, the antenna connectors 14-2, 14-3 and 14-4 have the same core as the core 15 of the antenna connector 14-1, and are aligned with the same lines lengths. 8/18 [0026] In the present embodiment, although this will be described later, a length of the longest long-side of the shield casing 13 is set to be equal to or less than 1/4 of a wavelength of a highest received frequency in the air. Further, in the inside of the shield casing 13, a partition area having a plurality of partitions formed by inner walls is formed, and a length of a long side of the longest inner wall is set to a length equal to or less than 1/4 of a wavelength of the highest received frequency in the air. Further, in the antenna connector 14, a length of an exposed part of the core 15 is set to a length equal to or less than 1/4 of a wavelength of the highest received frequency in the air. The tuner module 10 has a structure in which a high-frequency connection is made between the core 15, which is an input signal supply point of the antenna connector 14, and the circuit, which is a functional unit of the tuner, by wirings on the main board 12. The core 15 of the antenna connector 14 is connected to the tuner module board 11 through direct contact with the tuner module board 11. Further, the core 15 of the antenna connector 14 is fixed by directly passing through the tuner functional unit and also passing through the underlying main board 12. [0027] In the present embodiment, as a method of connecting the tuner module board 11 with the main board 12, for example, a solder ball called a Ball Grid Array (hereinafter, BGA) is inserted between the tuner module board 11 and the main board 12 through a reflow process. Alternatively, for example, a method of providing through-holes 111 in ends (end surfaces) of the board as shown in Fig. 2 and connecting the tuner module board 11 and the main board 12 by soldering in the through-holes using only the end surface of half of a cylinder of the through-hole through router cut after plating is used for fixing. [0028] Next, a definition of a length of the core 15 of the antenna connector 14 in the present embodiment will be described. Fig. 3 is an illustrative view defining a length of the core of the antenna connector in the present embodiment. 9/18 [0029] Since high frequency inductances of the core portions of the antenna connectors 14-1 to 14-4 made as described above are substantially the same, high frequency impedance can be the same irrespective of a mounting direction. Accordingly, in the TV tuner module 10 having the present structure, re-design of an electrical characteristic due to a mounting direction of the antenna connector 14 can be omitted, and a TV tuner module having a mounting structure subjected to variations can be provided in a short design time. In addition, in the antenna connector 14 (-1 to -4), the length of the exposed part of the core 15 is set to a length equal to or less than 1/4 of a wavelength of the highest received frequency in the air. [0030] Further, protrusions 13-1, 13-2, 13-3, 13-4, and 13-5 of the shield casing 13 shown in Fig. 1 are solder parts for connection to the main board 12, mainly, through a solder joint. Further, intervals of the soldering protrusion 13-1, 13-2, 13-3, 13-4, 13-5 will be described with reference to Fig. 3. [0031] For the shield casing 13 to have a good shield effect, even when a received frequency of the TV tuner module 10 is an upper limit, a noise is prevented from entering from the interval of the protrusions into the shield and a received signal is prevented from leaking from the internal tuner circuit. Here, the reception frequency of the TV tuner module 10 being the upper limit refers to an upper limit reception frequency at the shortest wavelength when a radio wave is induced. Accordingly, among the solder joint protrusions of the shield casing 13, for example, the interval between the protrusions 13-1 and 13-2 is shorter than 1/4 of a wavelength X of the upper limit reception frequency such that a non-soldering part length L generated when solder-jointed to the main board 12 is set as in the following equation. A/4 indicates a wavelength at which the strongest resonance occurs by way of the antenna in the air, and prevents a void, a pattern or the like in which resonance easily occurs from being formed in the high-frequency module, such as the TV tuner module 10. It is preferable that sense of the solder joint protrusions satisfy a condition of the 10/18 following equation: [0032] [Math. 1] L