Extendable Antenna for a Radio Transceiver

This present invention is related to an extendable antenna for a radio transceiver and more particularly to an antenna for a portable radio transceiver.

Extendable antennas have been developed to reduce the size of the portable radio tranceiver. A conventional antenna is shown in FIG. 8, 9 and 10. In FIG. 10, a dash line shows the state of the antenna retracted into a housing 1 of a radio transceiver 2. This state is defined as a retracted mode in the description below. A two-dot chain line shows the state of the antenna extended. This state is defined as an extended mode. The extended mode is shown in FIG. 8. A printed circuit board 5 (a PC board 5) is disposed in the housing 1, and high frequency components are mounted on the PC board 5. A coupling member 7 is mounted on the PC board 5 and connected with a duplexer (not shown). The duplexer is connected with a transmitter and a reciver (not shown), also on the PC board 5. The duplexer the transmitter and the receiver act as the circuitry of the transceiver 2.

A metal ring 9 has a female-screw portion and is inserted into the housing 1 and fitted. The coupling member 7 is connected with the metal ring 9. A holding member 11 has a male-screw portion, and the male-screw portion is screwed into the metal ring 9. The holding member 11 has some elastic tongues 11a for holding an antenna 3. Since the holding member 11 is metal, the coupling member 7 is electrically connected with the holding member 11.

The antenna 3 has a stopper portion 3a at a bottom portion, a top end cap 3b at a top portion, and a core portion 3c coupled to the stopper portion 3a and the top end cap 3b.

As shown in FIG. 8, when the antenna 3 is extended from the housing 1, the stopper portion 3a is engaged with a top of the tongues 11a and the stopper portion 3a is held by the tongues 11a. Since the stopper portion 3a and the core portion 3c are conductive material, the core portion 3c is electrically connected with the circuitry of the transceiver 2.

On the other hand, as shown in FIG. 9, when the antenna 3 is pushed down toward the housing 1, the top end cap 3b is held in the tongues 11a. In this state the top end cap 3b is held by the toungues 11a. However, the top end cap 3b is plastic, therefore the antenna 3 is not electrically connected with the circuitry. Accordingly, the antenna 3 does not detect a radio frequency signal (RF signal) in the retracted mode.

When an operator does not wish to operate the transceiver, he often retracts the extendable antenna and thus reduces the antenna's projection to make the transceiver a suitable size for carrying. When the RF signal comes to the trasceiver 2 in the retracted mode, the antenna 3 does not detect the RF signal. Therefore, to detect the RF signal, the operator must extend in advance the antenna 3 out of the housing.

To solve this deficiency, it is considered that a top end cap is conductive material and that the circuitry is electrically connected with the top end cap and an antenna core portion in the retracted mode. However, the electrical length of the top end cap is much less than the well known length of whip antennas having large gain (for example, a quarter wavelength). Accordingly the top end cap does not detect the RF signal. Furthermore in the retracted mode, almost all of the antenna core portion is located into the housing. However, there are shielding cases povided on the PC board to shield components (on the PC board) against interfering electric waves. These cases and the operator's hand interupt the RF signal which comes to the antenna core and therefore result in much reduction in a radiation efficiency. Accordingly the antenna core does not detect the RF signal.

To solve deficiency above, it is considered that the transceiver has an inner antenna and a rod antenna. The inner antenna may detect the RF signal when the rod antenna is retracted into the housing 10. However, the transceiver must detect the state in which the rod antenna is retracted and needs to have switching means for switching from the rod antenna to the inner antenna. Furthermore, the transceiver needs to have a conductive partition wall between the components and the inner antenna so that the components are not radiated by the inner antenna. Thus the transceiver needs to contain the inner antenna, the switching means and the conductive patition wall, therefore the size of the housing is large. Furthermore, the inner antenna is obliged to be disposed at an upper portion of the housing so that the inner antenna is not interrupted by the operator's hand when the RF signal comes to the transceiver. Therefore, other components may not disposed at the upper portion of the housing, as a result the inner antenna limits the area of possible location of the components.

Accordingly, it is an object of the present invention to provide an improved extendable antenna which detects a RF signal when the antenna's projection is reduced to make the transceiver a suitable size for carrying.

It is also the object of the present invention to provide an improved extendable antenna for the transceiver which eliminates the need of an inner antenna in the housing.

FIG. 1 is a partially cut-away elevational view which illustrates a portable radio transceiver including a preferred embodiment of the invention in the extended mode.

FIG. 2 is a partially cut-away elevational view which illustrates a portable radio transceiver including a preferred embodiment of the invention in the retracted mode.

FIG. 3 is a cut-away elevational view which illustrates the antenna.

FIG. 4 is a perspective view which illustrates the portable radio transceiver including the preferred embodiment of the invention.

FIG. 5 is a cut-away side view which illustrates the portable radio transceiver.

FIG. 6 is a partially cut-away elevational view which illustrates a portable radio transceiver including another embodiment of the invention in the extended mode.

FIG. 7 is a perspective view which illustrates the portable radio transceiver including another embodiment of the invention.

FIG. 8 is a partially cut-away elevational view which illustrates a portable radio transceiver including a conventional antenna in the extended mode.

FIG. 9 is a partially cut-away elevational view which illustrates the portable radio transceiver including the conventinal antenna in the retracted mode.

FIG. 10 is a perspective view which illustrates the portable radio transceiver including the conventional antenna.

As shown in FIG. 4, an extendable antenna 20 is provided at a housing 10 of a portable radio transceiver 12. The antenna 20 comprises a first antenna portion 20b and a second antenna portion 20c connected with the first antenna portion 20b.

The first antenna portion 20b has a circular top end cap 21. A holding member 18 is provided at the the top of housing 10, and has elastic tongues 18a. The holding member 18 is conductive material and has a circular hole. The diameter of the top end cap 21 is larger than the inner diameter of the circular hole of the holding member 18. Therefore, when the second antenna portion 20c is retracted into the housing 10, the top end cap 21 strikes against the top surface of the housing 10 and is located out of the housing.

As shown in FIG. 3, a loading coil 22 is enclosed in the top end cap 21. The loading coil 22 is a helical winding composed of a piano wire. An outer housing of the top end cap 21 is plastic. The outer housing of the top end cap 21 is composed of a case 21a and a cover 21b. A metal fitting 30 is inserted and fitted into the case 21a. A bottom portion 22b of the loading coil 22 is inserted into the metal fitting 30. The cover 21b is fitted to the case 21a. The case 21a has a groove 23. When an operator rants to extend the antenna 20 from the housing 10, he may handle the groove 23.

An enclosed fitting 24 is brass. The metal fitting 30 is inserted into one end of the enclosed fitting 24. A portion 30a of the enclosed fitting 24 is compulsorily gripped and reformed by a tool. Therefore, the loading coil 22 is electrically connected with the metal fitting 30 and the enclosed fitting 24.

As shown in FIG. 2, when the second antenna is retracted into the housing (this state is defined as a retracted mode), the enclosed fitting 24 is held by the tongues 18a of a holding member 18. This holding member 18 is fitted to a metal ring 19, and the metal ring 19 is fitted in the top portion 10a of the housing and connected with a coupling member 17. The coupling member 17 is connected with the circuitry of the trnsceiver 12 (not shown) on a printed cicuit board 15 (a PC board 15). Therfore, in the retracted mode, the loading coil 22 is electrically connected with the the circuitry of the trnsceiver 12 via the enclosed fitting 24 and the holding member 18. Thus, the enclosed fitting 24 acts as a connecting portion which connects the loading coil 22 with the circuitry of the transceiver in the retracted mode, and connects the first antenna portion 20b with the second antenna portion 20c. Furthermore, the holding member 18 acts as a feeding portion.

As shown in FIG. 3, an antenna core 26 is composed of a flexible stainless wire. Pipe 28 is composed of a flexible polyoxymethylene. The antenna core 26 is inserted into the pipe 28. The pipe 28 is inserted into other end of the enclosed fitting 24.

The second antenna portion 20c has a stopper portion 20a composed of brass. The pipe 28 having the antenna core 26 is inserted into the stopper portion 20a. An end portion 26b of the stopper portion 20a is compulsorily gripped and reformed a tool. Thus, the antenna core 26 is electrically connected with the stopper portion 20a.

As shown in FIG. 1, when the antenna 20 is extented, the stopper portion 20a is engaged with the top of the tongues 18a and is held by the tongues 18a. Accordingly, when the antenna is extended (this state is defined as an extended mode), the antenna core 26 is electrically connected with the circuitry of the transceiver 12 via the stopper portion 20a and the holding member 18.

As shown in FIG. 3, the loading coil 22 is helically wound, and its electrical length from a top portion 22a to the bottom portion 22b is a quarter wavelength, while its physical length is much less than a quarter wavelength. When the second antenna portion 20c is retracted into the housing 10, the bottom portion 22b of the loading coil 22 is located at the top portion 10a of the housing 10. Accordingly, the bottom portion 22b of the loading coil 22 is electrically connected with the holding member 18 (the feeding portion). That is to say, the retracted mode is equivalent to a state in which a quarter wavelength rod antenna is located on the top portion 10a of the housing 10.

On the other hand, the length from a top portion 26a to a bottom portion 26b of the antenna core 26 is a quater wavelength. As a result, the electrical length from the bottom portion 26b to the top portion 22a of the loading coil 22 is a half wavelength. Therefore, the extended mode is equivalent to a state in which a half wavelength rod antenna is located on the top portion 10a.

As shown in FIG. 4, in the retracted mode, since the second antenna portion 20c is entirely retracted into the housing 10, the second antenna portion 20c does not detect the RF signal. However other components in the housing should not be radiated by the second antenna portion 20c to operate normally To realize this object, as shown in FIG. 5 the stopper portion 20a cotacts a ground portion 32 (on the PC board 15) when the second antenna portion 20c is retracted into the housing 10. The length from the coupling member 17 to the ground portion 32 (via the second antenna portion 20c) is a quarter wavelength. When the holding member 18 is assumed to a standard point, the impedance Z of the second antenna portion 20c is described in the expression below.

1: the lengh of the top 26a to the bottom 26b of the second antenna portion 20c

.lambda.: wavelength

As in the description above. 1 is a quarter wavelength, thus Z is infinity. Furthermore 1 may be N times as long as a quarter wavelength where N is an odd number (1=1/4.lambda.,3/4.lambda.,5/4.lambda.. . . ). Accordingly, the circuitry of the transceiver 12 does not feed a transmitting signal to the second antenna portion 20c, therefore the second antenna portion 20c does not radiate other components in the housing 10. Thus, other components are not radiated and not badly influenced by the seccond antenna portion 20c, therfore these components operate normally.

As mentioned above, when the second antenna portion 20c is retracted into the housing 10, the loading coil 22 being a quarter wavelength is located out of the housing 10. Therefore, even if the second antenna portion 20c is retracted, the extendable antenna 20 detects the RF signal.

Generally when the operator does not wish to operate the transceiver, the operator reduces the antanna's projection to make the transceiver a suitable size for carrying. When the RF signal comes to the antenna in the retracted mode, the loading coil 22 detects the RF signal. Therefore, the extendable antenna 20 deters in either mode, and when the transceiver 12 is not being used, the extendable antenna 20 does not require to be extended in advance to detect the RF signal.

Furthermore, it is unnecessary to provide a portable transceiver with the inner antenna, switching means, and the conductive partition wall between the inner antenna and the other components required in the prior art, therefore the size of the housing is reduced. And since the transceiver does not need the inner antenna in a upper portion of the housing, other components may be disposed at the upper portion.

Furthermore, since the loading coil 22 is enclosed into the top end cap 21, when the transceiver 12 is carried, the loading coil 22 is not injured or broken. The loading coil 22 does not vibrate in the top end cap 21, and the quality of voice signal is kept to be good.

After the portable radio transceiver 12 detects the RF signal in the retracted mode, it is preferrable for the operator to extend the antenna until the stopper portion 20a is engaged with the tongues 18a so that the gain of the antenna becomes larger than the gain of the antenna in the retracted mode.

In the above embodiment, the second antenna portion 20c is only one rod portion. However, the second antenna portion may be extendable itself. This second embodiment is shown in FIG. 6 and FIG. 7. An extendable antenna 40 is provided at the housing or a radio transceiver 50. The antenna 40 has a second antenna portion 40c. The second antenna portion 40c has a pipe portion 44, a whip portion 46, and a stopper portion 40a. The pipe portion 44 is composed of metal. The whip portion 46 is composed of a stainless wire core and a polyoxymethylene coat.

The loading coil 22 is inserted and fitted into a top end of the pipe portion 44. A top end side of the whip portion 46 is inserted and engaged into the pipe portion 44. An engagement portion 46a is provided at the top end side of the whip portion 46. The engagement portion 46a is a board-shaped spring, therefore the whip portion 46 is slidably engaged in the pipe portion 44. The elastic power of the engagement portion 46a is determined to be smaller than that of the tongues 18a. In the extended mode, when the top end cap 21 is pushed down toward the housing 10, the engagement portion 46a slides in the pipe portion 44 toward the loading coil 22 and strikes against the bottom portion 48a of the loading coil 22. When the top end cap 21 is pushed more and more, the pipe portion 44 slides in the tongues 18a, and the second antenna portion 40c is retracted into the housing 10. Accordingly the shortened second antenna portion 40c is retracted into the housing 10, therefore the size of the shortened second antenna 40c in the retracted mode is smaller than the size of the second antenna 20c, and the space for the shortened second antenna in the housing 10 is smaller than the space for the second antenna 20c.

In the description above, the holding member acts as the feeding portion. Instead, the holding member may not be the same as the feeding portion. For example, the feeding portion being differrent from the holding member may be mounted on the PC board.

Furthermore, the loading coil is not always provided with only the first antenna portion. Instead, the loading coils may be provided with the first and second antenna portion. The space for the second antenna in the housing 10 is thus made smaller than the space for the second antenna 20c.

The loading coil may be provided at all of the first antenna portion or may be provided at a part of the first antenna portion.

The loading coil is not always enclosed into the top end cap. For example, the loading coil may be exposed or coated by plastic.

The electrical length of the first and second antenna is substatially a quarter wavelength and adjusted and decided so that the antenna may detect the RF signal best.

The electrical length of the first antenna portion may be substantially N times as long as a quarter wavelength where N is an integral number, for example, a half wavelength and three quarters wavelength. Furthermore the electrical length of first antenna portion may be substantially three-eighth wavelength. These lengths are well known as proper lengths of whip antennas.

The ground portion is not always required when other components are entirely shielded and not badly influenced by the second antenna in the retracted mode in the housing. In this embodiment, the length of the second antenna portion is not limited to be N times as long as a quarter wavelength where N is an odd number, therefore the length of the second antenna portion may be the well known proper length.

In the description above, the loading coil acts as a loading portion. Instead, the loading portion may be a ring-shaped capacity or a board-shaped capacity, as is known in the art. The loading portion has an impedance which is equivalent to the impedance of the loading coil being the proper length, for example a quarter wavelength.

In these embodiments, the feed portion is shown touching to the boundary of the first and second antennas. Instead, if the length from the touched position to the top portion of the loading coil is proper, the feed portion may contacts the antenna at another position in retracted mode.

Furthermore, when the transceiver is operated in the area where received signals strength is high, even a loading coil having the electrical length less than a quater wavelength detects RF signal. Therefore, the transceiver is operated in this area, the length of the loading coil may be less than a quater wavelegth.