JP2005130440A - Wireless interface apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless interface apparatus which extends a communication distance and has low power consumption by reducing a carrier wave frequency and an antenna in size and in which a wireless communication function is provided in a Compact Flash (R) card etc. <P>SOLUTION: The wireless interface apparatus deals with an interface of a memory, and is provided with an antenna having the wireless communication function. In the apparatus, the antenna used for transmission/reception of the carrier wave frequency is configured by a compression rate, at which the antenna length comes within the standard dimensions of the memory, and the antenna is installed inside the wireless interface apparatus 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wireless interface device that is used by being inserted into an external interface such as a PDA (Personal Digital Assistant) and a PC (Personal Computer).

In recent years, communication between a PDA, various information processing systems, and the like has been performed at a short distance, for example, in the same room using an IC card as an interface of the PC card standard (conforming to the standard by PCMIA). (For example, see Patent Document 1).
The IC card is used not only as a data storage medium but also for expansion of peripheral devices.

However, the wireless interface shown in Patent Document 1 is formed in an IC card shape as described above.
Therefore, the above-mentioned wireless interface is externally used for memory expansion such as CF (compact flash (registered trademark)), SD card (registered trademark), smart media (registered trademark) which has become a standard in PDA in recent years. It does not correspond to a memory interface (slot or expansion slot).

In addition, although the 2.4 GHz band and the 5 GHz band used for wireless LAN and the like are used as the carrier wave band for the wireless interface of the IC card, a sufficient communication distance cannot be obtained at these frequencies, and consumption There is a drawback that it has a lot of power and is not suitable for a portable terminal such as a PDA.
On the other hand, unlike the wireless LAN described above, the specific low power radio and weak radio have a long communication distance and low power consumption, but the carrier frequency is low, the wavelength is long, the antenna is large, and the degree of freedom of the PDA is reduced. Appearance is impaired in design.
JP 2001-195553 A

  The present invention has been made in view of such circumstances, and an object thereof is to reduce the carrier frequency, reduce the antenna, extend the communication distance, and reduce the power consumption, and the compact flash (registered trademark). An object of the present invention is to provide a wireless interface device capable of providing a wireless function in a card or the like.

  A wireless interface device according to the present invention is a wireless interface device including an antenna having a wireless communication function and corresponding to a memory interface, wherein an antenna length of the antenna used for transmission / reception of a carrier frequency is equal to that of the memory. The antenna is configured to have a shortening rate that falls within a standard dimension, and the antenna is installed inside the wireless interface device.

  The wireless interface device of the present invention is further characterized in that an adjustment circuit for adjusting the impedance between the antenna and a signal line for supplying a transmission signal is further provided.

  The wireless interface device of the present invention is characterized in that the ground point of the high-frequency circuit is connected to the ground point of the logic circuit through a filter that blocks a signal in a carrier frequency band used for communication.

  In the wireless interface device of the present invention, the antenna includes a substrate, a conductor film provided on a portion of the substrate, a feeding point provided on the substrate, a dielectric material provided on the substrate, and a dielectric material. A loading portion constituted by a linear conductor pattern formed in the longitudinal direction of the element body, an inductor portion connecting one end of the conductor pattern and the conductor film, one end of the conductor pattern, and the inductor portion; And a feeding point that feeds power to the connecting point, and the longitudinal direction of the loading portion is arranged so as to be parallel to the end side of the conductor film.

  According to the wireless interface device of the present invention, even when the carrier wave frequency having the long wavelength described above is used, the antenna is designed with a corresponding shortening rate so that the antenna fits in the wireless interface device. There is no such thing as getting out of the device, and it is possible to obtain an effect that the appearance is not impaired in design even in a small portable terminal such as a PDA.

  Further, according to the wireless interface device of the present invention, since the wireless interface device is inserted into a socket such as a PDA and mounted, impedance matching between the antenna and the transmission signal line can be adjusted. A transmission signal can always be transmitted in the vicinity of the maximum value of the transmission power, and an effect of preventing deterioration of radiation characteristics can be obtained.

  Furthermore, according to the wireless interface device of the present invention, the ground point of the high-frequency circuit is connected to the ground point of the logic circuit through a filter that blocks signals in the carrier frequency band used for communication. Therefore, the carrier frequency band generated in the PDA circuit and the logic circuit of the wireless interface device and the high-frequency current in the vicinity thereof are not input as noise to the GND wiring of the high-frequency circuit, thereby preventing the generation of radiation noise. can get.

  In addition, according to the wireless interface device of the present invention, an antenna length of 1/8 or less of the carrier frequency to be used can be realized, and the antenna shortening rate can be greatly improved. Therefore, a wireless interface device can be mounted on a USB connector or the like.

Hereinafter, a wireless interface device 1 according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the wireless interface device 1 according to the embodiment. In FIG. 1, the wireless interface device 1 is described as a CF card (registered trademark). The interface between the wireless interface device 1 and the PDA 7 is defined in accordance with the interface standard of the wireless interface device 1 (CFA; Compact Flash Association CF card (registered trademark) I / O card version standard).
The dimensions of the wireless interface device 1 are, for example, a length of 42.8 mm, a width of 36.4 mm, and a thickness of 3.3 mm (a CF card (registered trademark) dimension standard), and a PDA-7 CF card socket. Insert into and use.

Therefore, the size of the antenna incorporated in the wireless interface device 1 is limited to 42.8 mm in length. For this reason, if the carrier frequency to be used is from the 300 MHz band of weak radio to the 900 MHz band of specific low-power radio, the chip antenna 2 (see FIG. 2) having a quarter wavelength is used. The length shown in is required.
Frequency 1/4 wavelength 300MHz 250mm
400MHz 188mm
900MHz 83mm

Therefore, in the present embodiment, the 300, 400, and 900 MHz bands are respectively 84% or more and 79% or more so that the chip antenna 2 can be built in 42.8 mm which is the vertical dimension of the wireless interface device 1. , Designed / manufactured with a shortening rate of 50% or more.
Since the chip antenna 2 used in the present embodiment realizes a high shortening rate antenna and a small and high gain antenna as a circuit, a resonant circuit for transmitting and receiving radio waves is configured by a resonant circuit composed of an inductance component and a capacitance component. ing.

  The chip antenna 2 of the wireless interface device 1 according to the present embodiment is configured by incorporating a plurality of resonance circuits in order to obtain a high gain, and is configured by electrically connecting an inductance component and a capacitance component in parallel. Two or more resonant circuits are electrically connected in series. Further, the inductance portion has a coil portion formed of a spiral conductor with an axis as a center or a rectangular conductor that can approximate a spiral. The axis of the coil portion is aligned at substantially the same straight line in at least the adjacent resonance portions, and at least one of the portions that circulate around the axis of the conductor is substantially included in a plane inclined with respect to the axis.

Thereby, the wireless interface device 1 according to the present embodiment can extend the communication distance by using the carrier frequency of the 300 MHz band from the 300 MHz band of the specific low power radio and the weak radio without strict use examination, and Low power consumption can be achieved.
In addition, the wireless interface device 1 according to the present embodiment can design the chip antenna 2 so that the chip antenna 2 can be accommodated in the wireless interface device 1 even when a carrier frequency having a long wavelength is used. That is, the antenna design is performed by determining the shortening rate so that the chip antenna 2 has a length × width that can be built in the wireless interface device 1 such as a memory card. Accordingly, the wireless interface device 1 does not protrude from the PDA 7 in the mounted state, and the appearance of the PDA 7 or the like is not impaired.

  However, since the chip antenna 2 includes an inductance component and a capacitance component, the chip antenna 2 is extremely affected by the surrounding environment. That is, when the wireless interface device 1 is shipped, the impedance of the chip antenna 2 that matches the impedance of the transmission signal line changes due to the influence of the metal housing of the PC or PDA 7, and the radiation characteristics May deteriorate. In order to eliminate the influence of this metal casing, an antenna may be installed at a location away from the PC or PDA 7, but it is mounted on the wireless interface device 1 using the chip antenna 2 with a large shortening rate. It will deviate from its original purpose.

For this reason, the wireless interface device 1 according to the embodiment of the present invention is provided with the impedance adjustment circuit shown in FIG.
In this impedance adjustment circuit, a DC blocking capacitor 6 is connected to one of the parallel connection of the variable capacitance diode 3 and the capacitor 5, and the coil 4 is connected to the other. The other end of the coil 4 is grounded. The connection point R between the variable capacitance diode 3 and the capacitor 5 is connected to the chip antenna 2.

When a transmission signal (RF signal, which is a traveling wave) modulated from a high-frequency carrier wave is reflected at a contact (connection point R) having a different impedance, the traveling wave is affected by the reflected wave, and the traveling wave and the reflected wave are reflected on the line. A wave that combines waves is generated. This is a standing wave. If the ratio of the maximum value | V _max | and the minimum value | V _min | of the standing wave voltage is the voltage standing wave ratio (VSWR), the VSWR is 1 in the case of no reflection. The smaller the value, the less reflection. In the case of a small antenna such as the chip antenna 2, the VSWR at the connection point is about 3 or less.

A control unit (not shown) measures the VSWR at the connection point R, and gives the control voltage so that this ratio is about 3 or less, for example. The variable capacitance diode 3 has a characteristic that the capacitance changes according to the applied control voltage (reverse voltage), thereby adjusting the impedance of the line. The relationship between the reflected power and the control voltage is shown in FIG. The horizontal axis is the control voltage (V), and the vertical axis is the reflected power (VA).
Thereby, in the wireless interface device 1 according to the present embodiment, the control unit adjusts the impedance between the chip antenna 2 and the transmission signal line in a state where the wireless interface device 1 is mounted on the PDA 7 or the like. It becomes possible to always transmit a signal in the vicinity of the maximum transmission power. Therefore, it is possible to prevent deterioration of radiation characteristics and improve reception sensitivity.

When the wireless interface device 1 incorporating the chip antenna 2 is inserted into the socket for the wireless interface device 1 of the PDA-7 (or PC) and used, the digital signal of the PDA-7 is connected via the GND (ground) wiring. Is input to the wireless interface device 1.
As a result, noise due to the high-frequency current is superimposed on the transmission signal, and a transmission wave including a noise component (radiation noise) may be radiated from the chip antenna 2 in some cases.
In particular, when the frequency of the noise is present in and near the carrier frequency band, it is emitted as strong radiation noise, which adversely affects the reception characteristics of other wireless devices using the same carrier frequency band. Become.
However, since the frequency of the radiation noise differs depending on the device, it is difficult to remove this radiation noise on the receiving side.

  Therefore, in the wireless interface device 1 according to the present embodiment, a transmission signal is generated by modulating a carrier wave with a modulated wave, and a high-frequency circuit radiated from the chip antenna 2, a PDA 7 (or PC), transmission data, and a control signal Band reject filter (or band elimination filter) that blocks the GND wiring with the interface circuit that transmits and receives only the specified frequency band (carrier frequency band used by the card and the frequency range including the vicinity thereof) Connected through.

That is, the interface circuit is directly connected to the GND wiring of the PDA 7 via the socket terminal. On the other hand, the GND wiring of the high frequency circuit is connected to the GND wiring of the PDA 7 via a band reject filter, and the high frequency current in the carrier frequency band generated in the PDA 7 circuit and the interface circuit and in the vicinity thereof is connected. Generation of radiation noise is prevented without being input to the GND wiring of the high frequency circuit as noise.
Furthermore, spatial coupling (capacitive coupling) between the GND wiring of the interface circuit and the GND wiring of the high-frequency circuit on the substrate in the wireless interface device 1 is reduced. Therefore, the capacitive coupling can be reduced by forming these GND wirings on the same substrate surface with a predetermined distance through the band reject filter without forming them on the upper and lower sides of the substrate, respectively. Noise can be further reduced.

  According to the wireless interface device 1 of the present embodiment, as shown in FIG. 4, the GND wiring of the high frequency circuit is connected to the logic circuit of the wireless interface device and the GND wiring of the PDA 7 (or PC) via the band reject filter. It is connected. Therefore, the high frequency current in the carrier frequency band generated in the circuit of the PDA 7 and the logic circuit (interface circuit) of the wireless interface device 1 and the range in the vicinity thereof is not input as noise to the GND wiring of the high frequency circuit, and the radiation noise Occurrence can be prevented.

Next, a wireless interface device 10 according to a second embodiment of the present invention will be described with reference to FIGS.
The wireless interface device 10 according to the present embodiment is a wireless interface device used for mobile communication wireless devices such as mobile phones and wireless devices such as specific low power wireless and weak wireless.
As shown in FIGS. 5 and 6, the wireless interface device 10 includes a substrate 8 made of an insulating material such as a resin, a ground portion 9 that is a rectangular conductor film provided on the surface of the substrate 8, and A loading portion 15 disposed on one surface of the substrate 8, an inductor portion 16, a capacitor portion 17, and a feeding point P connected to a high-frequency circuit (not shown) provided outside the wireless interface device 10 It has. The antenna operating frequency is adjusted by the loading unit 15 and the inductor unit 16, and the radio wave is radiated at the center frequency of 430 MHz.

The loading portion 15 is configured by a conductor pattern 12 formed in a spiral shape with respect to the longitudinal direction of the surface of a rectangular parallelepiped element body 11 made of a dielectric material such as alumina.
Both ends of the conductor pattern 12 are respectively connected to connection electrodes 14A and 14B provided on the back surface of the element body 11 so as to be electrically connected to rectangular installation conductors 13A and 13B provided on the surface of the substrate 8. ing. Further, one end of the conductor pattern 12 is electrically connected to the inductor portion 16 and the capacitor portion 17 via the installation conductor 13B, and the other end is an open end.
Here, the loading portion 15 is disposed so that the distance L1 from the end 9A of the ground portion 9 is, for example, 10 mm, and the length L2 in the longitudinal direction of the loading portion 15 is, for example, 16 mm. It has become.

  Since the loading unit 15 has a physical length shorter than ¼ of the antenna operating wavelength, the self-resonant frequency of the loading unit 15 is higher than the antenna operating frequency of 430 MHz. For this reason, when the antenna operating frequency of the wireless interface device 10 is considered as a reference, it cannot be said that it is self-resonant, and therefore has a different property from a helical antenna that self-resonates at the antenna operating frequency. .

The inductor section 16 includes a chip inductor 21 and is connected to the installation conductor 13B via an L-shaped pattern 22 which is a linear conductive pattern provided on the surface of the substrate 8 and is similarly formed on the substrate 8. It is configured to be connected to the ground portion 9 via a ground portion connection pattern 23 which is a linear conductive pattern provided on the surface.
The inductance of the chip inductor 21 is adjusted so that the resonance frequency of the loading unit 15 and the inductor unit 16 is 430 MHz, which is the antenna operating frequency of the wireless interface device 10.
The L-shaped pattern 22 is formed such that the end side 22A is parallel to the ground portion 9, and the length L3 is 2.5 mm. As a result, the physical length L4 of the antenna element parallel to the end side 9A of the ground portion 9 is 18.5 mm.

The capacitor unit 17 includes a chip capacitor 31, and is connected to the installation conductor 13 </ b> B via the installation conductor connection pattern 32 that is a linear conductive pattern provided on the surface of the substrate 8. The power supply point P is connected via a power supply point connection pattern 33 that is a linear conductive pattern provided on the surface.
The capacitance of the chip capacitor 31 is adjusted so as to match the impedance at the feeding point P.

FIG. 7 and FIG. 8 show the frequency characteristics of VSWR (Voltage Standing Wave Ratio) at a frequency of 400 to 450 MHz and the radiation pattern of horizontal polarization and vertical polarization of the wireless interface device 10 configured as described above. Shown in
As shown in FIG. 7, the wireless interface device 10 has a frequency of 430 MHz, a VSWR of 1.05, and a bandwidth of VSWR = 2.5 of 14.90 MHz.

By using the wireless interface device 10 according to the present embodiment, an antenna length of 1/8 wavelength or less of the frequency to be used can be realized, and the shortening rate can be greatly improved. Therefore, the wireless interface device 10 can be built in a USB (Universal Serial Bus) connector which is a standard interface of a PC.
9A to 9C show the shape of a USB connector incorporating the wireless interface device 10 (FIG. 5) of this embodiment. The USB connector 40 is a USB connector corresponding to a series A plug. The USB connector 40 includes a PC connection unit 41 and a wireless communication unit 42.

9A is a front view of the PC connection unit 41, FIG. 9B is a plan view of the USB connector 40, and FIG. 9C is a rear view of the wireless communication unit 42. As the dimensions L5 to L9 of each part of the USB connector 40, for example, L5 = 7.5 mm, L6 = 12.0 mm, L7 = 30.0 mm, L8 = 16.0 mm, and L9 = 10.0 mm.
The dimensions of the wireless interface device 10 shown in FIG. 5 are L1 = 10 mm and L4 = 18.5 mm, which are sufficiently smaller than the shape of the wireless communication unit 42 of the USB connector 40 shown in FIG. The wireless interface device 10 (FIG. 5) can be incorporated in the wireless communication unit 42 of FIG.

  As described in the description of each embodiment, the wireless interface devices (1, 10) according to the first and second embodiments described above are provided with antennas for transmitting and receiving radio waves. In addition to the antenna, the wireless interface device (1, 10) is provided with a transmission / reception circuit for processing a signal received by the antenna, and an interface circuit for exchanging data with the PDA-7 or PC. It is done. In this way, by providing the wireless interface device (1, 10) with the antenna, the transmission / reception circuit, and the interface circuit, it is possible to install the PDA-7, etc. without adding or adding a special function to the PDA-7, etc. Wireless communication can be performed simply by inserting the wireless interface device (1, 10) into the slot.

  In the first and second embodiments described above, each wireless interface device (1, 10) has been described separately. However, the present invention is not limited to this, and it is possible to combine the two. For example, by applying the antenna structure described with reference to FIGS. 5 and 6 to the chip antenna 2 of FIG. 2, a wireless interface device can be configured.

  The embodiments of the present invention have been described above with reference to the drawings. However, the specific configuration is not limited to these embodiments, and design changes and the like can be made without departing from the scope of the present invention. It is.

  An antenna can be mounted not only on a memory but also on a board having a limited size such as an IC card corresponding to a PCMCIA (Personal Computer Memory Card International Association) standard.

It is the schematic which shows the structure of the radio | wireless interface apparatus 1 by the 1st Embodiment of this invention. 2 is a circuit diagram showing a configuration example of an impedance adjustment circuit provided in the wireless interface device 1. FIG. It is a graph which shows the relationship between the control voltage by the said impedance adjustment circuit, and reflected electric power. 2 is a circuit diagram showing a configuration of GND wiring on a substrate in the wireless interface device 1. FIG. It is a top view which shows the wireless interface apparatus 10 by the 2nd Embodiment of this invention. It is a perspective view which shows the wireless interface apparatus 10 by this embodiment. It is a graph which shows the frequency characteristic of VSWR of the radio | wireless interface apparatus 10 by this embodiment. It is a graph which shows the radiation pattern of the radio | wireless interface apparatus 10 by this embodiment. It is a figure which shows the shape of the USB connector 40 which incorporates the wireless interface apparatus 10 by this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 ... Wireless interface apparatus 2 ... Chip antenna 3 ... Variable capacitance diode 4 ... Coils 5, 6 ... Capacitor 7 ... PDA
8 ... Substrate 9 ... Earth part (conductive film)
DESCRIPTION OF SYMBOLS 11 ... Element 12 ... Conductor pattern 13A, 13B ... Installation conductor 14A, 14B ... Connection electrode 15 ... Loading part 16 ... Inductor part 17 ... Capacitor part 21 ... Chip inductor (lumped element)
22 ... L-shaped pattern 23 ... Earth part connection pattern 31 ... Chip capacitor 32 ... Installation conductor connection pattern 33 ... Feed point connection pattern 40 ... USB connector 42 ... Wireless communication part 41 ... PC connection P ... feed point R ... connection point

Claims (4)

A wireless interface device having an antenna that supports a memory interface and has a wireless communication function,
The antenna length of the antenna used for transmission / reception of the carrier frequency is configured with a shortening rate so as to be within the standard size of the memory,
The wireless interface device, wherein the antenna is installed inside the wireless interface device.   The wireless interface device according to claim 1, further comprising an adjustment circuit that adjusts an impedance between the antenna and a signal line that supplies a transmission signal.   3. The radio interface according to claim 1, wherein the ground point of the high-frequency circuit is connected to the ground point of the logic circuit through a filter that blocks a signal in a carrier frequency band used for communication. apparatus. The antenna is
A substrate,
A conductor film provided on a part of the substrate;
A feeding point provided on the substrate;
A loading portion provided on the substrate and configured by a linear conductor pattern formed in a longitudinal direction of an element body made of a dielectric material;
An inductor portion for connecting one end of the conductor pattern and the conductor film;
A feeding point for feeding power to a connection point between one end of the conductor pattern and the inductor part;
The wireless interface device according to claim 1, wherein the loading unit is disposed so that a longitudinal direction of the loading unit is parallel to an end side of the conductor film.

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