ANTENNA DEVICE AND PORTABLE RADIO DEVICE

Abstract: An antenna device is provided with a spiral first antenna and linear second antenna which slides in the first antenna in the axial direction. When this antenna device is housed, the upper end of the conductor portion of the second antenna is passed through the first antenna and placed apart from the lower end of the first antenna and, when the antenna device is pulled out, the lower end of the conductor portion of the second antenna is electrically connected to the upper end of the first antenna. Therefore, the length of the second antenna can be short in accordance with the wavelenght of electromagentic waves used. As a result, the housing space of the antenna device can be reduced further.

Description: TECHNICAL FIELD This invention relates to an antenna assembly, and more particularly to an antenna assembly suitable for use in a compact portable radio apparatus. BACKGROUND ART In recent years, portable radio apparatuses have been reduced in size and weight. Accordingly, antenna assemblies used for such portable radio apparatuses are also required to be smaller. As an antenna assembly which satisfies the above requirements, many manufacturers are developing whip antennas which can be retracted into the housing body when it is used for communications. In earlier stage, portable radio apparatuses of relatively simple structure have utilized as this type of whip antenna. However, such a simple antenna has the following problem. Specifically, the antenna, when extended from the housing body, is operative as a monopole antenna, whereas it cannot obtain a sufficient gain when retracted in the housing body. It can be considered that this is because the antenna retracted in the housing body is placed near the ground to cause an input impedance to increase, whereby impedance matching can be hardly established. Thus, to improve the gain of the antenna when retracted in the housing body, a whip antenna of a so-called top loading type came into use instead of the simple whip antenna described above. The top loading type whip antenna refers to an antenna assembly which has a helical antenna electrically connected to the top end of a rod antenna. When this type of whip antenna is extended from the housing body for use, radio waves can be radiated from both of the helical antenna and the rod antenna. When the antenna is retracted into the housing body, radio waves can be radiated from the helical antenna. However, this type of whip antenna includes the rod antenna which does not contribute to the radiation of radio waves when it is retracted. This portion operates as an open stub. The open stub may badly affect the input impedance of the antenna. Specifically, the open stub causes the impedance matching state to delicately come off due to the distance between the rod antenna and a circuit board in the housing space and so on. Thus, it cannot be said that this type of whip antenna is well designed. In addition, the whip antenna of top loading type, if not shielded completely, also has several problems that signals invade from the retracted rod antenna, signals go into a shielded portion, and so on. Then, as a result of investigations for solving the above-mentioned problems, an antenna assembly has been developed, in which a rod antenna, when retracted into the housing body, is electrically isolated from a helical antenna. A prior art example of such an antenna assembly will be described with reference to Figs. 1 to 6. Figs. 1 to 6 show two states of the antenna assembly equipped in a portable radio apparatus, i.e., an extended state and a retracted state. It should be noted that in the drawings, illustration of the whole portable radio apparatus is omitted, and the antenna assembly and portions of the portable radio apparatus associated with the connection to the antenna assembly only are described. Also, corresponding parts in the various drawings are designated the same reference numerals. First, the structure of an antenna assembly 1 shown in Figs. 1 and 2 will be described. The antenna assembly 1 is composed of two antenna portions, i.e., a rod antenna 1A and a helical antenna 1B. The rod antenna 1A is operative mainly when the antenna assembly 1 is extended from a housing body 2, while the helical antenna 1B is operative when the antenna assembly 1 is retracted into the housing body 2. The antenna assembly 1 is attached to the housing body 2 by screwing an antenna connection fitting 1C on the antenna side into an antenna fixture 2A arranged in a non-metallic housing body 2. The housing body 2 contains a circuit board 3 on which a variety of circuits as well as a power supply circuit 3A for the antenna assembly 1 are integrated. The power supply circuit 3A not only supplies the antenna assembly 1 with electric power through a power supply spring 3B but also has a function of matching a characteristic impedance of a transmitter/receiver circuit with an input impedance of the antenna assembly 1. The power supply circuit 3A is, as shown in Fig. 1, electrically connected to the antenna assembly 1 when the antenna assembly 1 is extended from the housing body 2 and an extended-state limiter 1D arranged around a lower end portion of the rod antenna 1A is mechanically coupled to the antenna connection fitting 1C. Specifically, the power supply circuit 3A is electrically connected to the rod antenna 1A by way of the antenna fixture 2A, antenna connection fitting 1C, extended-state limiter 1D, and stopper 1E in this order. In this way, the rod antenna 1A is brought into an operable state as a monopole antenna which has its ground level at the ground of the circuit board 3 and a shielding case. Incidentally, the stopper 1E is provided for preventing the antenna assembly 1 from falling out. The extended-state limiter 1D and the stopper 1E are both made of a single metal part. The rod antenna 1A is caulked with the stopper 1E for establishing electrical and mechanical connection therebetween. Also, the rod antenna 1A is entirely covered with an antenna cover 1F or the like so as to prevent a human body from directly touching the rod antenna 1A. On the other hand, when the antenna assembly 1 is retracted into the housing body 2 as shown in Fig. 2, the antenna connection fitting 1C is mechanically and electrically connected to a retracted-state limiter 1G, so that the helical antenna 1B can be powered from the power supply circuit 3A. In this state, the helical antenna 1B is operative as a helical antenna which has its ground level at the ground of the circuit board 3 and the shielding case. The helical antenna 1B is also entirely covered with an antenna cover 1H so as to prevent a human body from directly touching it. The antenna cover 1H is utilized as a handle with which the user extends the antenna assembly 1, and also functions as a stopper for preventing the antenna assembly 1 from falling into the housing body of the radio apparatus when it is retracted. As described above, since different antenna portions 1A, 1B individually operate when the antenna assembly 1 is extended and when it is retracted, favorable characteristics can be provided using the same matching circuit if impedances of the respective antenna portions are optimized. An antenna assembly 4 shown in Figs. 3 and 4 is also known as an antenna assembly which provides favorable characteristics as described above. Although the antenna assembly 4 is also composed of a rod antenna 4A and a helical antenna 4B, it differs from the antenna assembly 1 in the way each antenna is powered. More specifically, the helical antenna 4B is always powered from a power supply circuit 3A, while the rod antenna 4A is powered only when the antenna assembly 4 is extended. When the antenna assembly 4 is extended from a housing body 2, the rod antenna 4A extends through the inside of the helical antenna 4B, as shown in Fig. 3. This causes the rod antenna 4A to electromagnetically couple to the helical antenna 4B; whereby the rod antenna 4A can be powered. In this state, the rod antenna 4A is operative as a monopole antenna which has its ground level at the ground of a circuit board 3 and a shielding - case. The rod antenna 4A is fixed to an antenna connection fitting 4C by an extended-state limiter 4E disposed near the lower end thereof when the antenna assembly 4 is extended. Strictly speaking, the extended-state limiter 4E is mechanically engaged with a non-metallic extended-state fixture 4D arranged in the antenna connection fitting 4C. The rod antenna 4A and the helical antenna 4B of this example are also covered with antenna covers 4G and 4H, respectively, so as to prevent a human body from directly touching them. A non-metallic stopper 4F is provided for preventing the antenna assembly 4 from falling out. Fig. 4 shows connections at various portions of the antenna assembly 4 when it is retracted in the housing body 2. When the antenna assembly 4 is retracted into the housing body 2, the antenna assembly 4 is fixed by a retracted-state limiter 4J formed near the top end of the antenna assembly 4 which is mechanically engaged with a retracted-state fixture 4I arranged in the antenna cover 4G. In this state, since the distance G from a handle 4K to the upper end of the rod antenna 4A is larger than the length HL of the helical antenna 4B, the upper end of the rod antenna 4A is located below an antenna fixture 2A, so that the rod antenna 4A is electrically isolated from the helical antenna 4B. Therefore, the helical antenna 4B only is operative in the retracted state of the antenna assembly 4. The helical antenna 4B is operative as a helical antenna which has its ground level at the ground of the circuit board 3 and the shielding-case. The handle 4K also serves as a stopper for preventing the antenna assembly 4 from falling into the housing body 2. The antenna assembly 4 thus constructed also provides favorable characteristics when it is extended as well as when it is retracted. An antenna assembly 5 shown in Figs. 5 and 6 is also known as an antenna assembly which provides favorable characteristics, similarly to the above-mentioned ones. The antenna assembly 5 has substantially the same structure as the antenna assembly shown in Figs. 3 and 4. The feature of the antenna assembly 5 lies in that a rod antenna 5A operable when the antenna assembly 5 is extended is not powered through electromagnetic coupling but through mechanical and electrical connection. More specifically, when the antenna assembly 5 is extended from a housing body 2, the rod antenna is fixed by mechanical and electrical connection of an extended-state limiter 5B arranged near the lower end of the rod antenna 4A to an antenna connection fitting 5A. The rest of the structure is similar to that of the antenna assembly 4. In addition, a stopper 5C is also provided for preventing the antenna assembly 5 from falling out. After the antenna assembly 5 is extended from the housing body 2, the rod antenna 4A is mainly operative as an antenna which has its ground level at the ground of a circuit board 3 and a shielding case. Although a helical antenna 4B is also powered in this state, it is operative as an accessory of the rod antenna 4A. On the other hand, when the rod antenna 4A is retracted into the housing body 2, the rod antenna 4A is electrically isolated from the helical antenna 4B since the distance G from a handle 4K to the upper end of the rod antenna 4A is larger than the length HL of the helical antenna 4B. As a result, the helical antenna 4B only is operable in the retracted state. In this way, the antenna assembly 5 favorably operates when it is extended as well as when it is retracted. However, the above-mentioned three kinds of antenna assemblies 1, 4, 5 have implied a problem associated with a reduction in size of the portable radio apparatus. The problem is caused by the fact that the antenna length L must be shorter than the length of the housing body 2 for housing the rod antenna 1B or 4A in the housing body 2. However, since the antenna length L is essentially determined from wavelengths of used frequencies, it cannot be made shorter in order to reduce the size of the housing body 2. Generally, the antenna length L should be approximately one quarter to one half of wavelengths of used frequencies. Therefore, if a portable radio apparatus is to be made smaller than ever, an antenna assembly designed according to the conventional scheme may not be completely housed within the housing body of the radio apparatus. For example, when the antenna assembly shown in the prior art example is used in a portable radio apparatus for a frequency band of 800 [MHz], the antenna length L must be approximately 90 [mm] even if it is determined from one-quarter wavelength. Thus, the antenna assembly cannot be used in a portable radio apparatus with a housing body, the size of which is 90 [mm] or less. Also, with the antenna assembly 5 having the structure shown in Figs. 5 and 6, when the rod antenna 4A is extended, the rod antenna 4A and the helical antenna 4B are always connected simultaneously to the antenna fitting 5A, so that the rod antenna 4A is not operative as a simple monopole antenna. This constitutes the cause of lower design freedom. Antenna assembly designs are known from EP-A-0 511 577 and EP-A-0 467 822. EP-A-0 511 577 forms the basis of the precharacterising portion of claim 1. DISCLOSURE OF INVENTION The present invention relates to an antenna assembly and a portable radio apparatus using same which solve the problem described above. According to the present invention, there is provided an antenna assembly having a first helical antenna and a second rod antenna extending through the inside of said first antenna in the axial direction, wherein when said second antenna is retracted, the upper end of a conductive portion of said second antenna passes through said first antenna and positioned below the lower end of said first antenna; and when the second antenna is extended, the lower end portion of the conductive portion of said second antenna is electrically connected to the. upper end portion of said first antenna; characterised in that the antenna assembly further comprises: a non-metallic bar member having a length equal to or more than the length of said first antenna is connected to the upper end of the conductive portion of said second antenna, said bar member being placed inside said first antenna when said second antenna is retracted; and a third helical antenna is fixed to the top portion of said bar member, and the upper end of said first antenna is electrically connected to the lower end of said third antenna, when said second antenna is retracted, so that said first and third antennas are operable as a single helical antenna. In this way, in the antenna assembly according to this invention, when the second rod antenna is extended, the lower end of the second antenna is electrically connected to the upper end of the first antenna, so that the two antennas are operative as an apparently single antenna. Thus, the length of the second antenna can be shorter than a length determined based on radio communication frequency. Therefore, a space for housing the antenna can be reduced correspondingly. In addition when the rod antenna is retracted the two helical antennas are operative as a single antenna. Consequently, favourable radiation can be realized in both cases when the antenna is extended and the antenna is retracted. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a cross-sectional view showing the connections of various portions when the antenna is used in the extended state in a conventional antenna assembly; Fig. 2 is a cross-sectional view showing the connections of various portions when the antenna is used in the retracted state in a conventional antenna assembly; Fig. 3 is a cross-sectional view showing the connections of various portions when the antenna is used in the extended state in a conventional antenna assembly; Fig. 4 is a cross-sectional view showing the connections of various portions when the antenna is used in the retracted state in a conventional antenna assembly; Fig. 5 is a cross-sectional view showing the connections of various portions when the antenna is used in the extended state in a conventional antenna assembly; Fig. 6 is a cross-sectional view showing the connections of various portions when the antenna is used in the retracted state in a conventional antenna assembly; Fig. 7 is a cross-sectional view showing the connections of various portions when the antenna is used in the extended state in an antenna assembly of an improved design; Fig. 8 is a cross-sectional view showing the connections of various portions when the antenna is used in the retracted state in the antenna assembly of Fig. 7; Fig. 9 is a cross-sectional view showing the connections of various portions when the antenna is used in the extended state in the antenna assembly according to this invention; Fig. 10 is a cross-sectional view showing the connections of various portions when the antenna is used in the retracted state in the antenna assembly of Fig. 9; BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will hereinafter be described with reference to the accompanying drawings, along with further examples of antenna assemblies of another design. (1) First Example In Figs. 7 and 8, an antenna assembly is generally designated reference numeral 11. It should be noted that parts in Figs. 7 and 8 corresponding to those in Figs. 5 and 6 are designated the same reference numerals. The antenna assembly 11 is composed of two antenna portions, i.e., a rod antenna 11A and a helical antenna 11B. These two antenna portions are connected such that the rod antenna 11A is mainly operative when the antenna assembly 11 is extended, whereas the helical antenna 11B is always operative. The antenna assembly 11 of this example, however, differs from the prior art in the way the rod antenna 11A is powered. Specifically, the rod antenna 11A is not powered through an antenna connection fitting 5A and an extended-state limiter 5B, but through an antenna fixture 11C and an extended-state limiter 11D which are connected to the top end part of the rod antenna 11B. Stated another way, when the antenna is extended, the rod antenna 11A and the helical antenna 11B are combined to operate as a combined antenna. This is the reason that the length L of the rod antenna 11A can be made shorter. The antenna assembly 11 is attached to a housing body 2 by the connection fitting. More specifically, the antenna assembly 11 is attached to the housing body 2 by screwing an antenna connection fitting 5A on the antenna side into an antenna fixture 2A arranged in a non-metallic housing body 2. The housing body 2 contains a circuit board 3 on which a variety of circuits as well as a power supply circuit 3A are integrated. The power supply circuit 3A not only supplies the antenna assembly 11 with electric power through a power supply spring 3B but also has a function of matching a characteristic impedance of a transmitter/receiver circuit with an input impedance of the antenna assembly 11. It should be noted that the two antennas constituting the antenna assembly 11, i.e., the rod antenna 11A and the helical antenna 11B have their surfaces covered with antenna covers 4H and 4G, respectively, such that a human body is prevented from directly touching the antennas. The rod antenna 11A is provided around a lower end portion thereof with a stopper 11E for preventing same from falling out. With the structure described above, the operation of the antenna assembly 11 will be next described for two cases: when the antenna assembly 11 is used with the rod antenna extended from the housing body 2 (extended state) and with the rod antenna left retracted in the housing body 2 (retracted state). First, when the antenna assembly 11 is used with the rod antenna extended from the housing body 2 (Fig. 7), a power supply line between the power supply circuit 3A and the antenna assembly 11 is formed through mechanical and electrical connection between the retracted-state limiter 11D arranged around a lower end portion of the rod antenna 11A and the antenna fixture 11C. More specifically, the power supply circuit 3A is electrically connected to the rod antenna 11A through the power supply spring 3B, antenna fixture 2A, antenna connection fitting 5A, and helical antenna 11B in order. The rod antenna 11A is thus connected in series with the helical antenna 11B, whereby the two antennas 11A and 11B are operative as a combined antenna. This combined antenna has its ground level at the ground of the circuit board 3 and the shielding case. On the other hand, when the antenna assembly 11 is used with the rod antenna 11A retracted in the housing body 2 (Fig. 8), a retracted-state limiter 4J is engaged with a recess formed in the antenna fixture 11C. In this state, if the distance G from a handle 4K to the upper end of the rod antenna 11A is set larger than the length HL of the helical antenna 11B, the upper end of the retracted rod antenna 11A is located below the antenna connection fitting 5A. Thus, the rod antenna 11A, when retracted, is electrically isolated from the helical antenna 11B, with the result that the always powered helical antenna 11B is only operable. In this event, the helical antenna 11B is operative as a helical antenna which has its ground level at the ground of the circuit board 3 and the shielding case. As described above, the rod antenna 11A and the helical antenna 11B are operative as a single antenna when the antenna assembly 11 is extended, while the helical antenna 11B is only operative when the rod antenna 11A is retracted. Consequently, favorable radiation can be realized in both cases when the antenna is extended and the antenna is retracted. According to the foregoing structure, since the combined antenna formed of a series connection of the helical antenna 11B fixed to the housing body 2 and the rod antenna 11A can be used as a transmission/reception antenna when the rod antenna 11A is extended, the length L of the rod antenna 11A can be made shorter than one-quarter wavelength. This structure allows the realization of an antenna assembly having a length shorter than prior art antenna assemblies, i.e., an antenna assembly requiring a smaller housing space and hence a portable radio apparatus equipped with such a shorter antenna assembly. Further, since the rod antenna 11A is connected to extend upward from the upper end of the helical antenna 11B, overlapping of the rod antenna 4A and the helical antenna 4B, as is the case of the prior art examples, can be eliminated. Therefore, when the rod antenna 11A having the same length as the prior art example is used, the antenna length can be made longer in its extended state, thus improving the sensitivity of the antenna assembly and the portable radio apparatus as compared with the prior art. (2) Embodiment of the invention regarding the antenna desigh with two helical antennas: In Figs. 9 and 10, in which parts corresponding to those in Figs. 7 and 8 are designated the same reference numerals, reference numeral 12 generally indicates an antenna assembly of this embodiment. The antenna assembly 12 has a structure similar to that of the antenna assembly 11 described in the previous section, except that a second helical antenna 12A is additionally provided in a handle. More specifically, when the antenna assembly 12 is retracted into a housing body 2, the helical antenna 12A arranged in the handle is electrically connected in series with a helical antenna 11B fixed to the housing body 2 through a retracted-state limiter 12B and an antenna fixture 11C, such that the two helical antennas are operative as a single antenna. The remaining. structure of the antenna assembly 12 is similar to that of the antenna assembly 11. The helical antenna 12A in the handle is also covered with an antenna cover 12C so as to prevent a human body from directing touching it. With the foregoing structure, the operation of the antenna assembly 12 will be described for two cases: when the antenna assembly 12 is used extended from the housing body 2 (extended state) and when it is used left retracted in the housing body 2 (retracted state). First, when the antenna assembly 12 is used in the extended state (Fig. 9), a rod antenna 11A is powered from a power supply circuit 3A through mechanical and electrical connection of an extended-state limiter 11D arranged around a lower end portion of the rod antenna 11A to the antenna fixture 11C. More specifically, the power supply circuit 3A is electrically connected to the rod antenna 11A through a power supply spring 3B, antenna fixture 2A, antenna connection fitting 5A, and helical antenna 11B in order. This results in a series connection of the rod antenna 11A with the helical antenna 11B, whereby the two antennas 11A and 11B are operative as a single combined antenna. This combined antenna operates with its ground level taken at the ground of a circuit board 3 and a shielding case. On the other hand, when the antenna assembly 12 is used with the rod antenna 11A left retracted in the housing body 2 (Fig. 10), the retracted-state limiter 12B is engaged with a recess formed in the antenna fixture 11C to establish electrical and mechanical connection therebetween. This causes the second helical antenna 12A in the handle to be electrically connected in series with the helical antenna 11B on the housing body side, whereby the two helical antennas are operative as a single antenna. If the distance G from the upper end of the antenna cover 4G to the upper end of the rod antenna 11A is made larger than the length HL1 of the helical antenna 11B in the retracted state, the upper end of the retracted rod antenna 11A is located below the antenna connection fitting 5A. Thus, the electromagnetic coupling between the rod antenna 11A and the helical antenna 11B is not produced, so that the two antennas 11A and 11B are electrically isolated from each other. Consequently, the helical antennas 11B and 12A, which are connected with each other through the antenna fixture 11C and the retracted-state limiter 12B, are only placed in an operable state. In this event, the two helical antennas 11B and 12A are operative as a single helical antenna which has its ground level at the ground of the circuit board 3 and a shielding case. In this way, the rod antenna 11A and the helical antenna 11B are operative as a single antenna when the antenna assembly 12 is in the extended state, while the two helical antennas 11B and 12A are operative as a single antenna when the antenna assembly 12 is in the retracted state. Consequently, favorable radiation can be realized in both cases when the antenna is extended and the antenna is retracted. According to the foregoing structure, the following advantages can be obtained in addition to those described in connection with the first embodiment in the previous section. That is, by setting parameters so as to provide the rod antenna 11A and the helical antenna 12A in the handle with the same electrical characteristics, it is possible to present substantially the same input impedance characteristics when the antenna assembly 12 is in the extended state and in the retracted state. This results in realizing favorable radiation characteristics in both the states by using a single matching circuit. (3) Other Examples/Further Embodiments The antenna assembly designs described above have dealt with the case where the housing body is made of a non-metallic material. However, the present invention is not limited this, but the housing body can be made of a metallic material. However, if a metallic housing body is employed, a spacer or the like must be inserted to prevent the antenna fixture 2A from directly conducting with the metallic housing body. Also, the antenna assembly designs discussed above have dealt with the case where this invention is applied to an antenna assembly having a rod antenna of the simplest structure. However, the present invention is not limited to this particular type of rod antenna, but can be applied to an antenna assembly which employs a rod antenna of two-stage or multiple-stage retractable type. If a multiple-stage retractable rod antenna is employed, a housing space required therefore can be further reduced. Further, the antenna assembly designs discussed above have dealt with the case where the rod antenna 11A, has been shown as made of linear wire materials. However, the present invention is not limited to this particular form of rod antenna. Alternatively, an employed rod antenna can be made of helical windings of small diameter formed in a rod shape. Further, the antenna assembly designs discussed above have dealt with the case where a transmitter/receiver circuit is connected to the power supply circuit 3A and matching circuits. However, the present invention is not limited to this, but can be applied to a circuit only having a transmitter circuit or a receiver circuit connected thereto. Further, the antenna assembly designs discussed above have dealt with the case where matching circuits are provided at a previous stage or a rear stage of the power supply spring 3B to match input impedance for two kinds of switchably used antennas. However, the present invention is not limited to this, but does not require such a matching circuit depending on a switched antenna. Further, the antenna assembly designs discussed above have dealt with the case, when a rod antenna is retracted, a helical antenna attached to a movable portion of the antenna assembly is electrically connected to a helical antenna fixed to the housing body. However, the present invention is not limited to this, but the antenna to be connected to the helical antenna fixed to the housing body can be other than the helical type. Further, the antenna assembly designs discussed above have dealt with the case where a handle and a retracted-state limiter are integrally formed or a case, contrary to this, where the handle and the retracted-state limiter are separately formed. However, the formation of the handle portion can be either of the two options. Further, the antenna assembly designs discussed above have dealt with the case where a non-metallic spacer is inserted between an antenna support ring for supporting a helical antenna and another antenna support ring for supporting a rod antenna for providing a switching mechanism on a movable shaft of the antenna assembly. However, the present invention is not limited to this, but two grooves can be formed in an antenna cover for fixedly fitting the two metallic support rings, such that they are electrically isolated. Further, the antenna assembly designs discussed above have dealt with a portable telephone as a radio apparatus utilizing the antenna assembly. However, the present invention is not limited to this, but can be applicable to other apparatuses. INDUSTRIAL APPLICABILITY An antenna assembly according to the present invention is applicable to a portable radio apparatus such as a portable telephone, a mobile radio-phone, and a portable information terminal.

Claims: An antenna assembly having a first helical antenna (11B) and a second rod antenna (11A) extending through the inside of said first antenna in the axial direction, wherein when said second antenna is retracted, the upper end of a conductive portion of said second antenna (11A) passes through said first antenna (11B) and positioned below the lower end of said first antenna; and when the second antenna is extended, the lower end portion of the conductive portion of said second antenna is electrically connected to the upper end portion of said first antenna; characterised in that the antenna assembly further comprises: a non-metallic bar member (4H) having a length equal to or more than the length of said first antenna (11B) is connected to the upper end of the conductive portion of said second antenna (11A), said bar member being placed inside said first antenna when said second antenna is retracted; and a third helical antenna (12A) is fixed to the top portion of said bar member, and the upper end of said first antenna (11B) is electrically connected to the lower end of said third antenna (12A), when said second antenna is retracted, so that said first and third antennas are operable as a single helical antenna. The antenna assembly according to claim 1, comprising switching means for switching a power supply state to said second antenna (11A) or said third intenna (12A) via a first member (2A) and a second member (11C) in accordance with the state of said second antenna (11A), said first member (2A) for supporting said first antenna (11B) and said second member (11C) for supporting said second antenna (11A) when said second antenna is extended from. The antenna assembly according to claim 2, wherein said switching means includes an electric circuit. A portable radio apparatus comprising: an antenna assembly according to claim 1; a housing (2) for fixing said antenna assembly and for accommodating said second antenna (11A) inside when said second antenna is retracted; and a power supply circuit for supplying a power to said antenna assembly. The antenna assembly according to claim 4, comprising switching means for switching a power supply state to a first member (2A) or a second member (22D) in accordance with the state of said second antenna, said first member for supporting said first antenna (11B) and said second member for supporting said second antenna (11A) when said second antenna is extended being electrically isolated from each other. The portable radio apparatus according to claim 4, wherein the upper end and the lower end of said first antenna electrically shorted by the conductive portion of said second antenna, when said second antenna is extended.

Inventors: ITO HIROKI, KANAYAMA YOSHIKI, KURODA SHINICHI, TORIYAMA ICHIRO, TSUDA SHINICHIRO, ITO, HIROKI, KANAYAMA, YOSHIKI, KURODA, SHINICHI, TORIYAMA, ICHIRO, TSUDA, SHINICHIRO
Applicants: SONY CORP, SONY CORPORATION
Application year: 1995
Main classification: H01Q1
IPC codes: H01Q11, H01Q1, H01Q21, H01Q9