KR100579665B1 - Antenna device and portable radio communication device comprising such an antenna device - Google Patents

Abstract

Ground connectable to ground and divergent element 10 of the first conductive plane having a supply portion 12 operable in at least the first and second frequency bands and connectable to the supply RF of the radio communication device A diverging element 20 of the second conductive plane having a portion. A controllable switch 30 is arranged between the first and second divergent elements to selectively connect or disconnect the divergent elements from one another, the switch state being controlled by a control voltage input (V _switch ). do. A first filter 16 is arranged between the supply portion and the control voltage input, where the first filter is arranged to block propagation frequency signals. By providing a high pass filter 32 between the first and second diverging elements that are generally planar provided above the ground plane, quad-band operation is provided with high efficiency in a physically small antenna device.

Portable radiocommunication devices, antenna devices, divergent elements, switches

Description

TECHNICAL DEVICE AND PORTABLE RADIO COMMUNICATION DEVICE COMPRISING SUCH AN ANTENNA DEVICE

1 is an explanatory diagram of a conventional monopole antenna;

2A is a schematic diagram of a PIFA antenna according to the present invention;

2B and 2C show the PIFA antenna of FIG. 2A in a first and second mode of operation.

FIG. 2D shows the frequencies of the operating modes of the antenna shown in FIG. 2A; FIG.

3 is a schematic diagram of a printed circuit board arranged to fit in a portable communication device and having an antenna device according to the invention;

4 illustrates an embodiment of an antenna in which capacitive coupling between divergent elements is provided by a conductive sheet.

5 shows another embodiment of an antenna in which capacitive coupling between divergent elements is provided by a meandering interface between the divergent elements.

6 illustrates a divergent element structure of another embodiment.

7a shows a variant embodiment of an antenna arrangement according to the invention in which three divergent elements are provided.

7B-E illustrate different modes of operation of the antenna device shown in FIG. 7A.

The present invention relates generally to antenna devices and, more particularly, to controllable internal multiband antenna devices for use in portable radio communication devices, such as mobile telephones.

The invention also relates to a portable radiocommunication device comprising such an antenna device.

Internal antennas have been used for some time in portable radio communication devices. There are many advantages associated with using internal antennas, one of which is that the internal antennas are small and light, making them suitable for applications such as mobile phones where size and weight are of importance. An internal antenna type often used in portable radio communication devices is the so-called Planar Inverted F Antenna (PIFA).

However, the application of internal antennas to a mobile phone places some constraints on the structure of the antenna, such as, for example, the exact location of the divergent element or elements, the supply and ground portions, and the like. These constraints may make it difficult to find an antenna structure that provides a wide operating band. This is especially important for antennas intended for multiband operation, ie adapted to operate in two or more separate frequency bands. In a typical dual band telephone, the lower frequency band is concentrated around 900 MHz, the so-called GSM 900 band, while the upper frequency band is concentrated around 1800 MHz, which is the DCS band or 1900 MHz, which is the PCS band. If the upper frequency band of the antenna device is made wide enough to cover both 1800 MHz and 1900 MHz, a telephone operating in three different standard bands is obtained. In the near future, antenna devices are expected to operate four or even different frequency bands.

The number of frequency bands in passive antennas is limited by the antenna size. Active frequency control may be used to enable further increase in the number of frequency bands and / or to further reduce antenna size. An example of active frequency control is disclosed in the summary of Japanese Patent Laid-Open No. 10-190347, which discloses a patch antenna device capable of coping with a plurality of frequencies. Basic patch parts and additional patch parts are provided for this purpose, which are connected to each other by PIN diodes arranged to selectively connect or disconnect these patch parts from one another. Although this is against frequency control, the antenna device is still large enough to be suitable for switching between two or more relatively distinct frequency bands, such as for example between GSM and DCS / PCS bands. It doesn't work. Instead, this example of conventional devices is typical in that switching in and out of additional patches is used for tuning instead of generating an additional frequency band at a distance from the first frequency band.

Summary of Japanese Patent Application Laid-Open No. 2000-236209 discloses a monopole antenna including a linear conductor on a dielectric substrate, as shown in FIG. The diverging parts of the antenna consist of at least two metal pieces connected via diode switch circuits. The divergent elements have supply points connected at one end of the filter circuit to block high frequency signals. The signal (V _switch ) is used to control the diode switch. The disclosed structure is limited to monopole or dipole antennas. Furthermore, the object of the antenna according to the above-mentioned Japanese document is not to provide an antenna having a small size.

Therefore, a problem with conventional antenna devices is that it does not provide a PIFA type multiband antenna having a small size, volume and wide frequency bands while having good performance.

It is an object of the present invention to provide an antenna device of the kind described above in which the overall size of the antenna device is small while the frequency characteristics are contrasted to four relatively wide frequency bands.

It is still another object of the present invention to provide an antenna device having better multiband performance than conventional devices.

The present invention provides the antenna such that the first portions of the two divergent elements are connected to each other for propagation frequency signals and the second portions of the divergent elements are selectively connectable to each other by a switch controlled by a direct current voltage. This is based on the idea that by arranging several frequency bands can be provided for a physically very small antenna. This DC voltage is applied to the control input, where the filter portion provided between the radio frequency supply portion and the DC control input blocks the radio frequency signals.

According to a first aspect of the invention there is provided an antenna arrangement as defined in claim 1.

According to a second aspect of the invention there is provided a portable radio communication device as defined in claim 10.

Preferred embodiments are also defined in the dependent claims.

The present invention provides an antenna device and a portable radio communication device, in which problems with conventional devices are avoided or at least alleviated. Thus, a multi-band antenna device having an antenna volume as small as about 3 cm ³ is provided, which means that the antenna size is small compared to standardized multi-band patch antennas, but radio frequency performance is still maintained. In addition, the bandwidths of the antenna device according to the present invention can be improved compared to the corresponding conventional devices without any increase in physical size, which is believed to be the result of the use of the dual band antenna structure.

A PIN diode is preferred, wherein the switch has good characteristics when operating as an electrically controlled radio frequency switch.

The invention is now described by way of example with reference to the accompanying drawings.

In the following, a detailed description will be given of preferred embodiments of the antenna device according to the invention. In the detailed description, for purposes of explanation rather than limitation, specific details are set forth in order to provide a thorough understanding of the present invention, such as, for example, specific hardware, applications, techniques, and the like. However, it will be apparent to those skilled in the art that the present invention may be used in other embodiments that depart from these specific details. In some cases, detailed descriptions of well-known methods, devices, and circuits are omitted so as not to obscure the description of the present invention because of unnecessary details.

1 will not be treated anymore because it has been described in the prior art description.

2a shows an antenna device, generally designated 1. The antenna device comprises, as in the prior art, a generally planar first planar rectangular diverging element 10 made of an electrically conductive material such as a sheet metal or a flexible film. Like the electrical circuits of the portable radio communication device, a source RF of radio frequency signals of radio frequency signals is connected to the supply portion 12 of the first diverging element.

The antenna device also includes a second planar rectangular diverging element 20 which is generally planar. The switch element 30 is provided between the two divergent elements 10, 20. Such a switch element is preferably a PIN diode, ie a silicon junction diode having a high purity intrinsic layer that acts as a dielectric barrier between the p and n layers. Ideally, the PIN diode switch is characterized as an open circuit with infinite breaking in open mode and as a short circuit without loss of resistance in closed mode, making it suitable as an electrical switch. In practice, the PIN diode switch is not ideal. In open mode the PIN diode switch has a capacitive characteristic (0.1-0.4 kHz) resulting in finite blocking (15-25 kHz @ 1 kHz), and in closed mode the switch has resistive losses (0.05-0.2 Ω). It has a resistive property (0.5-3 Ω) which leads to).

The first and second diverging elements 10, 20 are also capacitively connected to each other by a high pass filter, shown as capacitor 32 in the figures. The high pass filter passes radio frequency signals, which means that the two diverging elements are one single element in terms of radio frequency as further described with reference to FIGS. 2B-2D.

The first and second diverging elements 10, 20 are arranged at a distance above a ground plane, such as a printed circuit board described below, for example, with reference to FIG. 3.

The direct current control input for controlling the operation of the PIN diode, indicated by the V _switch in the figures, is connected to the first diverging element 10 via a filter block 16 to the radio frequency characteristics of the antenna device. Do not affect. This means that the filter characteristics of the filter block 16 are designed to block radio frequency signals. In a preferred embodiment, the filter block 16 comprises a low pass filter.

Finally, the second diverging element is connected directly to ground at ground portion 22. This ground portion operates on both radio frequency signals emanating from the RF input and direct current signals emanating from the control input.

The antenna is preferably set to 50Ω.

The switching of the antenna functions as follows. The RF source and other electronic circuits of the communication device operate at a given voltage level, for example 1.5 volts. This determination is that the voltage level is high enough to generate the required voltage drop through the PIN diode, ie about 1 volt. This means that the control voltage (V _switch ) is switched between high and low voltages, for example 1.5 volts and 0 volts. When the control voltage (V _switch ) is the upper voltage, there is a voltage drop through the PIN diode 30 and thus a current drop of about 5-15 mA. This voltage drop makes the diode energized to electrically connect the two diverging elements 10, 20 to the diode 30.

In a state where the control voltage V _switch is a low voltage Low, there is insufficient voltage drop in the diode to bring the PIN diode 30 into an energized state. It is open. The second diverging element is then effectively connected to the first diverging element only via a capacitor 32.

The size and structure of the two divergent elements yield, for example, 850 and 1800 MHz bands with the switch open and 900 and 1900 MHz bands with the switch closed to obtain the desired resonance frequencies. Is selected together.

Turning now to FIG. 2B, FIG. 2B shows how from the radio frequency point of view two divergent elements 10, 20 act as one single divergent element with a C-shape overall. This is because capacitor 32, which acts as a high pass filter, acts as an RF bridge between two divergent elements. The switch 30 in the form of a PIN diode is in an open state, i.e. in a non-conductive state in FIG. 2B, because the control voltage (V _switch ) is low, i. No direct current flows through the diode. The C-shape of the combined divergent elements cooperates with the position of the supply portion 12 to cause the antenna device to resonate at two frequencies, effectively making it suitable for dual band operation.

In Fig. 2C, the switch 30 is in the closed state, that is, the diode is in the energized state. This state is achieved when a high control voltage (V _switch ) is applied to the control input, as shown in FIG. 2A. This voltage passes through the low pass filter 16, across the first diverging element 10, and then through the diode 30, across the second diverging element and then through the ground portion 22. To generate a direct current that flows to ground. With the switch closed, i.e. with the diode energized, the radio frequency bridge between the two divergent elements is extended. This is clearly seen in FIG. 2C when compared to FIG. 2B.

Changing the geometry of these efficient divergent elements adjusts the resonant frequencies of the antenna device. This is shown in FIG. 2D, where the curves of the dashed line correspond to the operating mode shown in FIG. 2B and the curves of the solid line correspond to the operating mode shown in FIG. 2C. This means, for example, that an antenna device is obtained which can operate in four different frequency bands, such as the 850, 900, 1800, 1900 MHz bands described above.

The adjustment of the resonant frequencies shown in FIG. 2D can be usefully used in so-called foldable telephones. In communication devices of this kind, the resonant frequency of the internal antenna element tends to move downward in frequency when the position of the telephone is changed from fold mode to non-fold mode. In the antenna device according to the present invention, when the telephone is in the non-folded state, movement of the resonant frequencies can be prevented by closing the switch 30. Therefore, when the telephone is in the folded state, the control voltage (V _{switch 2} ) becomes low and when the telephone is in the non-folded state, the control voltage becomes high. The antenna then operates as a dual band antenna with a constant resonant frequency independent of the operating mode of the communication device (folded / non-folded).

The reconciliation of the resonant frequencies shown in FIG. 2D may also be usefully used in dual band bar type telephones. In the frequency bands used for mobile communication, the transmit (TX) and receive (RX) frequencies are separated by about 45-90 MHz. Using frequency adjustment, efficiency can be obtained by adjusting the near-optimal efficiency by fitting the frequencies to the transmit and receive frequencies instead of the wider frequency band incorporating the transmit and receive frequencies.

In FIG. 3 the two diverging elements 10, 20 are arranged in parallel and spaced apart entirely on a printed circuit board 70 which is adapted for mounting to a portable communication device 80 such as, for example, a mobile telephone. It is shown. The printed circuit board functions as a ground plane of the antenna device. Overall contours of the communication device are shown in dashed lines in FIG. 3. In typical dimensions of the antenna device 1 the height is about 4 mm and the total volume is about 3 cm 3.

All components except the two divergent elements 10, 20, the switch element 30 and the capacitor 32 may be provided on the printed circuit board to facilitate easy assembly of the antenna device. Will be recognized. This assembly is made easier by the fact that there is no separate supply for the switch element.

A conventional manufacturing method for an antenna device is to provide a conductive layer in which divergent portions of the antenna are formed on a carrier made of a nonconductive material such as, for example, a polymer or other plastic material. Thus, since the carrier is made of a heat sensitive material, it is required that a small heating area be kept as low as possible when soldering components to the antenna device.

4 shows how the capacitive bridge can be provided by a conductive sheet 34 provided below a portion of the two diverging elements 10, 20 in the radio frequency bridge position. have. When a flexible film having a plurality of layers is used to provide the divergent elements, the divergent elements 10 and 20 are provided on one side of the flexible film and the conductive sheet 34 is provided on the other side. Can be. In this way, it is possible to provide capacitive coupling between the divergent elements without separately separating the components.

5 shows how a capacitive bridge can be provided by a meandering interface between the two divergent elements 10, 20. Also in this way, it is possible to provide capacitive coupling between the divergent elements without separating the components separately.

6 shows the structure of a variant embodiment of the divergent element. In all respects, the antenna operates as described above with reference to FIGS. 2A and 2B-2D.

In FIG. 7A, in a variant embodiment, indicated generally as 100, an additional third diverging element 140 is connected to the third diverging element via a low pass filter 142 and has a second control input (V _{switch). 2} ). The third diverging element is connected to the second diverging element 120 by a second switch 144 in the form of a PIN diode.

In addition, in the embodiment shown in FIG. 7A, the first diverging element 110 is connected to ground at ground portion 114 via a high pass filter 118 that blocks direct current signals. Finally, the second diverging element 120 is connected to ground at ground portion 124 via a low pass filter 124 that blocks radio frequency signals. Thus, in this embodiment, there are separate ground portions for radio frequency signals and direct current (ie, control) signals.

The antenna device of FIG. 7A operates as follows. The first control voltage (V _switch ) acts as in the first embodiment shown in FIG. 2A. Thus, a high voltage flows through the first switch 130 and produces a current flowing through the low pass filter 124 to ground. In a state where the second control voltage V _{switch 2} is low, the second switch 144 is in a non-energized state. This means that the third diverging element 140 is effectively disconnected from the second diverging element, as shown in FIGS. 7B and 7C.

With the positions of the first switch 130 and the supply 112 open as shown in FIG. 7B, the first and second diverging elements 110, 120 connected to each other by a capacitor 132. Resonates at the first frequency. With the first switch closed, as in FIG. 7C, the combination of the first and second divergent elements resonates at a second frequency.

As shown in FIGS. 7D and 7E, the first, second, and third diverging elements 110, 120, and 140 are in the closed state, that is, in a state where the second control voltage is high. Is resonant at the third or fourth frequency, depending on whether the first switch 130 is open or closed. Thus, quad band operation is also provided for this structure.

Preferred embodiments of the antenna device according to the invention have been described. It should be appreciated, however, that they may be modified within the scope of the appended claims. Thus, a PIN diode has been described as the switch element. It will be appreciated that other kinds of switch elements may also be used.

In FIGS. 2 a, 3 and 7 a the divergent elements are planar and described as generally rectangular. It will be appreciated that the divergent elements can take any suitable shape, for example bent to fit the case of the portable radio communication device on which the antenna device is mounted.

One switch is shown connecting the two divergent elements to each other. It will be appreciated that one or more switches, for example several parallel PIN diodes, can be used without departing from the spirit of the invention.

According to the present invention as described above, the overall size is small while the frequency characteristics are prepared for at least four relatively wide frequency bands and have a better multi-band performance than conventional antennas and portable wireless communication comprising such an antenna device. There is an effect that can provide a device.

Claims (12)

An antenna device for a portable radiocommunication device operable in at least first and second frequency bands, A first conductive divergent element (10; 10 '; 10 "; 110) having a supply portion (12; 112) connectable to a supply (RF) of the radio communication device; A second conductive divergent element 20; 20 '; 20' '; 120 having a ground portion 22; 122 connectable to ground; Controllable switch 30 arranged in between the first and second divergent elements to selectively connect or diverge the divergent elements from one another and in a switched state controlled by a control voltage input (V _switch ) 130); And A first filter (16; 116) arranged between the supply portion (12; 112) and the control voltage input (V _switch ) and arranged to block propagation frequency signals; Including; Further comprising a high pass filter (32; 132) connected between the first and second diverging elements and passing radio frequency signals, Wherein the first and second diverging elements are planar and arranged at a distance above the ground plane (70). The method of claim 1, And the controllable switch (30; 130) comprises a PIN diode. The method of claim 1, And the first filter (16; 116) is a low pass filter. The method of claim 1, And the second diverging element (20) is directly connected to ground. The method of claim 1, And the first and second diverging elements (10, 20; 110, 120) have a C-shape with the high pass filter (32; 132). The method of claim 1, The high pass filter (32) comprises an electrically conductive sheet (34) provided under a portion of the two diverging elements (10, 20). The method of claim 6, A flexible film having a plurality of layers, wherein the diverging elements 10, 20 are provided on one side of the flexible film and the conductive sheet 34 is on the other side of the flexible film. Antenna device, characterized in that provided. The method of claim 1, The high pass filter (32) comprises an meandering interface between the first and second diverging elements (10 ', 20'). The method of claim 1, The third diverging element 140 is connected to a third diverging element 140 together with a second control input (V _{switch 2} ), which is connected to the third diverging element via the first low pass filter 142. With the second switch 144 connected to the second diverging element 120, The second diverging element 120 and the second ground portion 114 arranged on the first diverging element 110 connected to ground via a second high pass filter 118 that blocks direct current signals. And a second low pass filter (124) arranged between the ground and ground. A portable radio communication device comprising a printed circuit board that is planar, and an antenna device connected to a grounding device and a supply device (RF) having an electrical circuit prepared for transmitting and receiving radio frequency signals, The antenna device,  A first conductive divergent element (10; 10 '; 10 "; 110) having a supply portion (12; 112) connectable to a supply (RF) of the radio communication device; A second conductive divergent element 20; 20 '; 20' '; 120 having a ground portion 22; 122 connectable to ground; A controllable switch 30 arranged between the first and second divergent elements to selectively connect or disconnect the divergent elements from one another, the switch being in a switched state controlled by a control voltage input (V _switch ); 130); And A first filter (16; 116) arranged between the supply portion (12; 112) and the control voltage input (V _switch ) and arranged to block propagation frequency signals; Is in a state containing, A high pass filter connected between the first and second diverging elements to pass radio frequency signals, Wherein said first and second diverging elements are planar and arranged at a distance from above the ground plane. The method of claim 10, The communication device is a collapsible telephone, When the communication device is in the folded state, the control voltage applied to the control voltage input (V _switch ) is low, When the communication device is in the unfolded state, the control voltage applied to the control voltage input (V _switch ) is high, And the antenna device operates as a dual band antenna having a constant resonance frequency independent of the operating mode of the communication device. The method of claim 10, When the communication device is operating in the transmission mode, the control voltage applied to the control voltage input (V _switch ) is low, and And the control voltage applied to the control voltage input (V _switch ) is high when the communication device is operating in a reception mode.

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