Microstrip antenna, wireless tag communication device, and sheet processing device

Abstract

To provide a microstrip antenna that can improve the efficiency of energy conversion from an electric signal to a radio wave.SOLUTION: A microstrip antenna includes a radiating element. The radiating element has a first radiating region having a first major axis parallel to a first direction and a first minor axis perpendicular to the first major axis, and a second radiating region having a second major axis parallel to the first direction and longer than the first major axis, and a second minor axis perpendicular to the second major axis. The length of the second minor axis is shorter than the length of the first minor axis.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a microstrip antenna, a radio tag communication device, and a sheet processing device. [Background technology]

[0002] There are image forming apparatuses that form images on sheets equipped with wireless tags such as RFID (radio frequency identifier) ​​tags. Such image forming apparatuses may exchange information with the wireless tags on the sheets via radio waves using a microstrip antenna equipped with multiple types of radiating elements capable of transmitting and receiving radio waves. However, the efficiency of energy conversion from electrical signals to radio waves using the microstrip antenna has not always been good. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-018943 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a microstrip antenna, a radio tag communication device, and a sheet processing device that can improve the efficiency of energy conversion from an electrical signal to radio waves. [Means for solving the problem]

[0005] The microstrip antenna of the embodiment has a radiating element. The radiating element has a first radiating region having a first major axis that is a major axis parallel to a first direction and a first minor axis that is a minor axis perpendicular to the first major axis, and a second radiating region having a second major axis that is a major axis parallel to the first direction and longer than the first major axis, and a second minor axis that is a minor axis perpendicular to the second major axis. The length of the second minor axis is shorter than the length of the first minor axis. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing an example of an image forming apparatus 10 according to an embodiment. [Figure 2] FIG. 2 is a functional block diagram of the image forming apparatus according to the embodiment. [Figure 3] 4A and 4B are diagrams showing examples of positions where a sheet can be present in the image forming apparatus according to the embodiment. [Figure 4] 5A and 5B are diagrams illustrating an example of the relationship between the arrangement of wireless tags on a sheet and the conveyance direction of the sheet in the embodiment. [Figure 5] FIG. 2 is a diagram showing an example of the configuration of a wireless tag communication device 201 according to an embodiment. [Figure 6] FIG. 2 is a diagram showing an example of a side view of the configuration of an antenna 600 according to an embodiment. [Figure 7] FIG. 3 is an explanatory diagram illustrating an example of a shape of a radiating element in the embodiment. [Figure 8] 6A and 6B are diagrams showing an example of the results of an experiment using an antenna 600 including a radiating element 630 according to an embodiment. [Figure 9] FIG. 10 is an explanatory diagram illustrating an example of the shape of a radiating element 630 in a modified example. [Figure 10] FIG. 10 is a diagram showing an example of the results of an experiment using an antenna 600 equipped with a radiating element 630 according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, a radio tag communication device and a sheet processing device according to an embodiment will be described with reference to the drawings. In the following description, components having the same or similar functions are denoted by the same reference numerals, and descriptions of duplicated components may be omitted.

[0008] 1 is a diagram illustrating an example of an image forming apparatus 10 according to an embodiment. The image forming apparatus 10 is an example of a sheet processing apparatus.

[0009] 1, the image forming apparatus 10 includes a control panel 13, a wireless tag communication device 201, and a printer unit 18. The printer unit 18 includes a control unit 100, paper feed cassettes 161 and 162, etc. The control unit 100 controls the control panel 13, the wireless tag communication device 201, and the printer unit 18. The control unit 100 controls the conveyance of sheets in the printer unit 18. Controlling the conveyance of sheets means controlling the timing of conveying the sheets, the stopping position of the sheets, the conveyance speed of the sheets, etc.

[0010] The control panel 13 includes input keys and a display unit. For example, the input keys accept input from the user. For example, the display unit is a touch panel type. The display unit accepts input from the user and displays it to the user. For example, the control panel 13 displays configurable items related to the operation of the image forming apparatus 10 on the display unit. The control panel 13 notifies the control unit 100 of the items set by the user.

[0011] The paper feed cassettes 161 and 162 store sheets equipped with wireless tags. Of course, the paper feed cassettes 161 and 162 can also store sheets without wireless tags. In the following description, unless otherwise specified, the sheets are assumed to be sheets equipped with wireless tags. The sheets are made of a material such as paper or plastic film.

[0012] The printer unit 18 performs an image forming operation. For example, the printer unit 18 forms an image indicated by image data on a sheet. In the following description, forming an image on a sheet is also referred to as printing. The printer unit 18 includes an intermediate transfer belt 21. The printer unit 18 supports the intermediate transfer belt 21 with a driven roller 41, a backup roller 40, and the like. The printer unit 18 rotates the intermediate transfer belt 21 in the direction of arrow m.

[0013] The printer unit 18 includes four sets of image forming stations 221, 222, 223, and 224. The image forming stations 221, 222, 223, and 224 are used to form images of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The image forming stations 221, 222, 223, and 224 are arranged below the intermediate transfer belt 21 along the rotation direction of the intermediate transfer belt 21.

[0014] The following description will be given taking as an example the Y (yellow) image forming station 221 among the image forming stations 221, 222, 223, and 224. Note that the image forming stations 222, 223, and 224 have the same configuration as the image forming station 221, and therefore detailed description thereof will be omitted.

[0015] The image forming station 221 includes a charger 26, an exposure scanning head 27, a developing device 28, and a photosensitive drum cleaner 29. The charger 26, the exposure scanning head 27, the developing device 28, and the photosensitive drum cleaner 29 are arranged around the photosensitive drum 24 that rotates in the direction of arrow n.

[0016] The image forming station 221 includes a primary transfer roller 30. The primary transfer roller 30 faces the photosensitive drum 24 with the intermediate transfer belt 21 interposed therebetween.

[0017] In the image forming station 221, the photosensitive drum 24 is charged by the electrostatic charger 26 and then exposed by the exposure scanning head 27. The image forming station 221 forms an electrostatic latent image on the photosensitive drum 24. The developing device 28 develops the electrostatic latent image on the photosensitive drum 24 using a two-component developer made of toner and carrier.

[0018] The primary transfer roller 30 performs the primary transfer of the toner image formed on the photosensitive drum 24 onto the intermediate transfer belt 21. The image forming stations 221, 222, 223, and 224 form a color toner image on the intermediate transfer belt 21 by the primary transfer roller 30. The color toner image is formed by sequentially overlapping toner images of Y (yellow), M (magenta), C (cyan), and K (black). The photosensitive cleaner 29 removes any toner remaining on the photosensitive drum 24 after the primary transfer.

[0019] The printer unit 18 includes a secondary transfer roller 32. The secondary transfer roller 32 faces the backup roller 40 across the intermediate transfer belt 21. The secondary transfer roller 32 performs secondary transfer of the color toner images on the intermediate transfer belt 21 onto the sheet all at once. In the following description, the term "toner image" may refer to either a color toner image or a toner image of only one color. The toner image may also be a toner image using a decolorizable toner.

[0020] The conveying path 331 is a conveying path from the junction 441 to the branching portion 442. The conveying path 332 is a conveying path that passes through the inside of the double-sided printing device 38, and is a conveying path from the branching portion 442 to the junction 441. The conveying path 333 is a conveying path from the branching portion 442 to the paper discharge tray 20.

[0021] The leading edge of a sheet taken out from paper feed cassette 161, paper feed cassette 162, or manual feed tray 163 hits the area where two stopped registration rollers 31 are in contact. The sheet hitting registration rollers 31 has its inclination corrected. Controller 100 starts rotation of registration rollers 31 in accordance with the position of the toner image on rotating intermediate transfer belt 21, and moves the sheet to the position of secondary transfer roller 32. Controller 100 performs secondary transfer of the toner image formed on intermediate transfer belt 21 onto the sheet by secondary transfer roller 32. Controller 100 transports the sheet to conveyance path 331, and forms an image by fixing the toner image on the sheet by fixing device 34. Controller 100 transports the sheet with the image formed thereon to conveyance path 333, and then discharges the sheet.

[0022] In the case of double-sided printing, the control unit 100 conveys the sheet with an image formed on its front side to the conveying path 333. After the entire sheet has passed through the branching unit 442, the control unit 100 switches back and conveys the sheet to the conveying path 332. The control unit 100 then conveys the sheet to the junction unit 441 via the conveying path in the double-sided printing device 38, and conveys it to the conveying path 331 via the registration rollers 31. The control unit 100 then fixes the toner image using the fixing unit 34 to form an image on the back side of the sheet. The control unit 100 conveys the sheet with the image formed on its back side to the conveying path 333 and discharges the sheet.

[0023] The RFID tag communication device 201 can communicate with the control unit 100. The RFID tag communication device 201 communicates with the RFID tag on the sheet to read information from the RFID tag and write information to the RFID tag. The RFID tag communication device 201 transmits a signal in the direction of arrow k. The signal is specifically a modulated radio wave. Information is written to the RFID tag on the sheet by the signal transmitted from the RFID tag communication device 201.

[0024] Before the image formed in the printer unit 18 is secondarily transferred by the secondary transfer roller 32, an electrostatic latent image is formed on the photosensitive drum 24 from the exposure scanning head 27. The electrostatic latent image formed on the photosensitive drum 24 is primarily transferred to the intermediate transfer belt 21 as a toner image. Furthermore, the toner image primarily transferred to the intermediate transfer belt 21 is secondarily transferred to the RFID tag sheet transported to the position of the registration roller 31.

[0025] Next, a functional block diagram of the image forming apparatus according to the embodiment will be described with reference to FIG. 2, the image forming apparatus 10 includes a control unit 100, a control panel 13, a printer unit 18, and a wireless tag communication device 201.

[0026] The control unit 100 includes a calculation unit 51 and a storage device 52. The calculation unit 51 controls the control panel 13, the printer unit 18, and the RFID tag communication device 201 in accordance with an image processing program stored in the storage device 52. The control unit 100 outputs, for example, information indicating that sheet conveyance has started (hereinafter referred to as "conveyance start information").

[0027] The arithmetic device 51 is, for example, a CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit). The storage device 52 is, for example, a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), or an SSD (Solid State Drive). The data receiving unit 53 receives print data (e.g., data written in a page description language) indicating an image to be printed from a host such as a PC (Personal Computer), and stores the received print data in the storage device 52. The image data developing unit 54 determines printing conditions from the print data stored in the storage device 52 by the data receiving unit 53, thereby developing the data into data (e.g., raster data) that can be printed by the printer unit 18, and stores the data in the storage device 52.

[0028] The printer unit 18 includes a fixing device 34, a secondary transfer roller 32, and a developing device 28. The printer unit 18 forms an image on a sheet based on data stored in the storage device 52 by an image data developing unit 54.

[0029] 3 is a diagram showing an example of a position where a sheet can be present in image forming apparatus 10 of the embodiment. In FIG. 3, sheet Sb indicates a sheet placed in sheet feed cassette 161. Sheet Sc indicates a sheet placed on sheet discharge tray 20. Sheet Sd indicates a sheet placed on manual feed tray 163. The sheet feed cassettes 161 and 162, sheet discharge tray 20, and manual feed tray 163 are examples of a placement unit.

[0030] Sheet Sa indicates a sheet being conveyed along conveyance path 331. Each sheet is provided with a wireless tag.

[0031] 3, the sheet on which information is to be written to the wireless tag (hereinafter also referred to as the "target sheet") is the sheet being conveyed through the conveyance path 331. Therefore, the sheet Sa is an example of the target sheet.

[0032] 3, the RFID tag communication device 201 transmits a signal in the direction of the arrow k. That is, the k direction is the transmission direction of the signal transmitted by the RFID tag communication device 201. Therefore, the k direction is also the propagation direction of the radio waves emitted by the RFID tag communication device 201.

[0033] Each wireless tag that receives a signal performs an operation according to the content of the received signal. The wireless tag, for example, stores information indicated by the received signal. The wireless tag, for example, responds to the wireless tag communication device 201. Responding specifically means transmitting a signal. The wireless tag communication device 201 receives the signal transmitted from the wireless tag provided on each sheet. In the case of Figure 3, one of the wireless tags that receives the signal is the wireless tag provided on sheet Sa. In Figure 3, sheet Sa is being conveyed.

[0034] A radio tag has a shape with a major axis and a minor axis in a plane perpendicular to the k-direction, and when the wavelength of radio waves is the same, it interacts more strongly with polarized waves whose polarization plane is parallel to the major axis than with polarized waves whose polarization plane is perpendicular to the major axis. A strong interaction means that the radio waves are less likely to penetrate the radio tag and that the radio waves that reach the radio tag are more likely to be absorbed or reflected by the radio tag. Therefore, from the perspective of power consumption and low frequency of communication errors, it is desirable for the radio tag communication device 201 to use radio waves whose polarization plane is parallel to the major axis of the radio tag to exchange information with the radio tag. Note that the occurrence of a communication error means that information exchange between the radio tag communication device 201 and the radio tag is not possible.

[0035] FIG. 4 is a diagram showing an example of the relationship between the arrangement of wireless tags on a sheet and the sheet conveyance direction in an embodiment. In FIG. 4, tags Ta, Tb, Tc, and Td are each an example of a wireless tag provided on a sheet Sa being conveyed along the conveyance path 331. Tag Ta is an example of a wireless tag provided on the sheet Sa such that its major axis is perpendicular to the conveyance direction and perpendicular to the long axis direction of the paper. Tag Tb is an example of a wireless tag provided on the sheet Sa such that its major axis is parallel to the conveyance direction and parallel to the long axis of the sheet Sa. Tag Tc is an example of a wireless tag provided on the sheet Sa such that its major axis is perpendicular to the conveyance direction and parallel to the long axis of the sheet Sa. Tag Tc is an example of a wireless tag provided on the sheet Sa such that its major axis is parallel to the conveyance direction and perpendicular to the long axis of the sheet Sa. Note that while FIG. 4 shows an example in which one wireless tag is provided on one sheet, it is not necessarily required that only one wireless tag is provided on one sheet; multiple wireless tags may be provided on one sheet.

[0036] The sheet transport direction is, for example, a direction perpendicular to the k direction in Fig. 3, and is a direction from bottom to top on the paper surface of Fig. 3. Since the wireless tag is provided on the sheet, the sheet transport direction is also the wireless tag transport direction.

[0037] FIG. 5 is a diagram showing an example of the configuration of a radio tag communication device 201 according to an embodiment. The RFID tag communication device 201 includes an antenna 600 , a RFID tag communication control unit 501 , a transmitting / receiving circuit unit 502 , and an interface unit 503 .

[0038] The antenna 600 transmits a signal. The antenna 600 receives an incoming signal. The carrier of the signal transmitted by the antenna 600 is a radio wave. The carrier of the signal received by the antenna 600 is a radio wave.

[0039] The RFID tag communication control unit 501 is configured using a processor 901 such as a CPU and a memory 902. The RFID tag communication control unit 501 operates when the processor 901 reads and executes a program stored in the memory 902. The RFID tag communication control unit 501 controls the operation of each functional unit included in the RFID tag communication device 201. A write threshold is stored in advance in the memory 902.

[0040] The RFID tag communication control unit 501 receives, for example, sheet conveyance start information. The RFID tag communication control unit 501 controls, for example, the operation of each functional unit included in the RFID tag communication device 201 to cause the RFID tag communication device 201 to transmit a signal. The RFID tag communication control unit 501 demodulates the signal received by the antenna 600 by controlling, for example, the operation of each functional unit included in the RFID tag communication device 201. The RFID tag communication control unit 501 measures, for example, the elapsed time since receiving the conveyance start information.

[0041] The transmitting / receiving circuit section 502 includes a modulation section 504 , a transmission amplifier 505 , a receiving amplifier 506 , a demodulation section 507 , a circulator 508 , and a changeover switch 509 .

[0042] The modulation unit 504 modulates the radio waves emitted by the radio tag communication device 201. More specifically, a modulated voltage is applied to the modulation unit 504 under the control of the radio tag communication control unit 501, and the applied voltage causes the modulation unit 504 to generate a modulated current. The current generated by the modulation unit 504 flows to the transmission amplifier 505, and then the antenna 600 generates radio waves. The radio waves generated by the antenna 600 are the radio waves emitted by the radio tag communication device 201. In this way, the radio waves modulated by the modulation unit 504 are the radio waves emitted from the antenna 600, and therefore the radio waves modulated by the modulation unit 504 are the signals transmitted by the radio tag communication device 201.

[0043] The transmission amplifier 505 controls the strength of the signal transmitted by the RFID tag communication device 201. The circulator 508 separates the signal transmitted by the antenna 600 from the signal received by the antenna 600.

[0044] The changeover switch 509 switches the destination of the voltage application (i.e., the target to which the current modulated by the modulation unit 504 and amplified by the transmission amplifier 505 flows). Specifically, the changeover switch 509 switches the connection destination of the transmission amplifier 505 to one of the power feed lines 641 or 642 described below. The changeover switch 509 is, for example, an RF (radio frequency) switch such as a single-pole double-throw switch. The operation of the changeover switch 509 is controlled by the radio tag communication control unit 501. The changeover switch 509 operates under the control of the radio tag communication control unit 501, thereby switching the destination to which the voltage is applied.

[0045] Receiving amplifier 506 controls the strength of the signal received by antenna 600 to a predetermined strength. Demodulating section 507 demodulates the signal received by antenna 600.

[0046] The interface unit 503 is an interface that electrically connects the RFID tag communication control unit 501 and the control unit 100 .

[0047] 6 is a diagram showing an example of a side view of the configuration of an antenna 600 according to an embodiment. The antenna 600 is a microstrip antenna including a ground conductor plate 610, a dielectric substrate 620, and a radiating element 630. The ground conductor plate 610 is a grounded conductor. The dielectric substrate 620 is a dielectric material in contact with the ground conductor plate 610.

[0048] The radiating element 630 is a conductor located on the opposite side of the dielectric substrate 620 from the ground conductor plate 610, and is in contact with the dielectric substrate 620. The radiating element 630 is connected to feeder lines 641 and 642 that penetrate the dielectric substrate 620 and the ground conductor plate 610. The feeder lines 641 and 642 are conductors. When a voltage is applied to the radiating element 630 via either the feeder line 641 or 642, the radiating element 630 emits radio waves generated by a current generated by the applied voltage. The radiated radio waves are signals. The wave vector of the radio waves radiated by the radiating element 630 is a vector pointing in the k direction. Hereinafter, when there is no need to distinguish between the feeder lines 641 and 642, they will be referred to as the feeder line 640. The end of the feeder line 640 that is not in contact with the radiating element 630 is connected to the selector switch 509.

[0049] For ease of explanation, the plane perpendicular to the k direction will be referred to as the XY plane. Of the two mutually orthogonal vectors that define the XY plane, the vector perpendicular to the conveying direction of the sheet conveyed on the conveying path 331 will be referred to as the X vector, and the vector perpendicular to the X vector will be referred to as the Y vector.

[0050] The shape of the surface of radiating element 630 perpendicular to the k direction is substantially the same regardless of the position in the k direction. The length of radiating element 630 in the k direction is preferably shorter than the wavelength of the radio waves radiated by radiating element 630, and in particular, is preferably less than ¼ of the wavelength.

[0051] 7 is an explanatory diagram illustrating an example of the shape of the radiating element 630 in the XY plane (hereinafter referred to as "radiating element shape") in this embodiment. The direction perpendicular to the paper surface of FIG. 7 is parallel to the k direction.

[0052] The surface surrounded by the radiating element shape (hereinafter referred to as the "radiating element surface") has a first radiating region, a second radiating region, and a third radiating region. That is, the first radiating region, the second radiating region, and the third radiating region are located in the same plane. The first radiating region, the second radiating region, and the third radiating region are regions having a major axis and a minor axis perpendicular to the major axis.

[0053] The first radiation region and the second radiation region satisfy a major axis condition, a minor axis condition, and a direction condition. The major axis condition is a condition that the second major axis, which is the major axis of the second radiation region, is longer than the first major axis, which is the major axis of the first radiation region. The minor axis condition is a condition that the second minor axis, which is the minor axis of the second radiation region, is shorter than the first minor axis, which is the minor axis of the first radiation region. The direction condition is a condition that the first major axis and the second major axis are parallel.

[0054] In Fig. 7, the first radiation region is region 701. In Fig. 7, the second radiation region is region 702. In Fig. 7, the third radiation region is region 703. Therefore, in the example of Fig. 7, the first major axis, the second major axis, and the third major axis, which is the major axis of the third radiation region, are parallel to the X axis. In addition, in the example of Fig. 7, the first minor axis, the second minor axis, and the third minor axis, which is the minor axis of the third radiation region, are parallel to the Y axis.

[0055] 7, feed point 801 located within region 702 is a feed point. Region 701 is in contact with region 702. Region 702 is in contact with region 701 and region 703. Region 702 is in contact with region 703. Therefore, an electrical signal applied to feed point 801 flows through region 701, region 702, and region 703.

[0056] 7, the shapes of regions 701, 702, and 703 are rectangular, which is a type of shape having a major axis and a minor axis. However, the shapes of the first emission region, second emission region, and third emission region are not necessarily limited to rectangular as long as they have a major axis and a minor axis. The shapes may also be ellipses, for example.

[0057] For ease of explanation, the length of the first major axis will be represented as L1, the length of the first minor axis as W1, the length of the second major axis as L2, the length of the second minor axis as W2, the length of the third major axis as L3, and the length of the third minor axis as W3. In the example of FIG. 7, L1 = L3<L2であり、W1=W3> It's W2.

[0058] The first radiating region has a major axis length of L1, so it resonates with a signal with a wavelength equal to twice the length L1. Therefore, the resonant frequency of the first radiating region is the inverse of twice L1. The second radiating region has a major axis length of L2, so it resonates with a signal with a wavelength equal to twice the length L2. Therefore, the resonant frequency of the second radiating region is the inverse of twice L1. The third radiating region has a major axis length of L3, so it resonates with a signal with a wavelength equal to twice the length L3. Therefore, the resonant frequency of the third radiating region is the inverse of twice L3.

[0059] Fig. 8 is a diagram showing an example of the results of an experiment using antenna 600 including radiating element 630 in the embodiment. More specifically, Fig. 8 is a diagram showing an example of the results of measuring S11 for antenna 600 including radiating element 630 in Fig. 7 (hereinafter referred to as "first Kawasaki antenna"). In the experiment, the lengths of radiating element 630 included in the first Kawasaki antenna were L1 = L3 = 75 mm, L2 = 75.8 mm, w1 = w3 = 29 mm, and W2 = 15 mm.

[0060] The horizontal axis represents frequency, and the vertical axis represents S11. Therefore, the value on the vertical axis becomes larger on the negative side as the conversion efficiency of the electrical signal injected into antenna 600 into radio waves increases. In the experiment, the dielectric constant of dielectric substrate 620 was 4.6, and radiating element 630 was made of copper, whose conductivity was 5.8×10 7 [S / m].

[0061] In Figure 8, graph G1 shows the results for the Kawasaki No. 1 antenna, and graph G0 shows the results for the comparison antenna. The comparison antenna differs from the Kawasaki No. 1 antenna in that it does not satisfy the minor axis condition and that W1 = W3 = 15 mm.

[0062] Graph G1 shows peaks near frequencies of 910 MHz and 930 MHz. Because the 910 MHz signal has a longer wavelength than the 930 MHz signal, the peak near 910 MHz is caused by the presence of the second radiation area of ​​the first Kawasaki antenna. The peak near 930 MHz is caused by the presence of the first and third radiation areas of the first Kawasaki antenna.

[0063] The results in Figure 8 show that the S11 of the No. 1 Kawasaki Antenna shows a peak at around 910 MHz that is lower than any of the peaks shown in graph G0. Therefore, the results in Figure 8 show that the No. 1 Kawasaki Antenna was able to improve the efficiency of energy conversion from electrical signals to radio waves compared to the comparative antennas.

[0064] The difference between the first Kawasaki antenna and the comparison antenna is whether the length of the minor axis is uniform or non-uniform. More specifically, the comparison antenna has the same length of the minor axis regardless of the region, but the first Kawasaki antenna's second minor axis is shorter than the first and third minor axes. This difference improves the efficiency of energy conversion from electrical signals to radio waves.

[0065] In the example of Fig. 7, there are three regions, the first to third radiation regions. However, there do not necessarily have to be three regions. If there are first and second radiation regions that satisfy the major axis condition, minor axis condition, and direction condition, the efficiency of energy conversion from electrical signals to radio waves will be improved.

[0066] The antenna 600 configured in this manner includes a radiating element 630 having a first radiating area and a second radiating area that satisfy the major axis condition, the minor axis condition, and the directional condition, and therefore, as experimental results show, the efficiency of energy conversion from an electrical signal to radio waves can be improved.

[0067] Furthermore, since the RFID tag communication device 201 configured in this manner includes the antenna 600, it is possible to improve the efficiency of energy conversion from an electric signal to radio waves. Furthermore, since the image forming apparatus 10 configured in this manner includes the antenna 600, it is possible to improve the efficiency of energy conversion from an electric signal to radio waves. This is not limited to the image forming apparatus 10, but is also true for other sheet processing apparatuses that include the RFID tag communication device 201.

[0068] Other sheet processing devices include, for example, barcode printers used for managing the receipt and shipment of goods, and reading devices attached to goods provided in retail stores such as apparel stores. In such cases, the sheet equipped with a wireless tag is a sheet attached to the goods.

[0069] (Variation) Note that the one end parallel to the first major axis and the one end parallel to the second major axis do not necessarily need to be located on the same axis (i.e., the ends are aligned) as shown in FIG. 7 . This applies not only to the first and second major axes, but also to the third major axis. However, aligning the ends has the effect of increasing gain. If the ends are not aligned, the number of sides of the radiation area increases, dispersing power. Therefore, if the ends are not aligned, less power flows in the major axis direction than if the ends are aligned. As described above, the first to third radiation areas radiate radio waves with a resonant frequency determined by the length of their major axes. Therefore, the more power flows along the major axes, the higher the gain. Therefore, aligning the ends is more desirable than not aligning the ends.

[0070] It is desirable that the distance between the first to third radiation regions be within a few millimeters. By keeping the distance within a few millimeters, the same amount of power flows through each region, and the corresponding resonant frequencies can be obtained simultaneously. This allows for compatibility with a wide band.

[0071] The length of the third major axis does not necessarily have to be the same as the length of the first major axis, as long as the third major axis is a major axis parallel to the first major axis and has a length different from at least one of the lengths of the first major axis and the second major axis.

[0072] Furthermore, the length of the third minor axis does not necessarily have to be the same as the length of the first minor axis. Therefore, for example, the length of the third major axis may be the same as the length of the second major axis, and the length of the third minor axis may be the same as the length of the second minor axis. Alternatively, the length of the third major axis may be shorter than the length of the first major axis, and the length of the third minor axis may be longer than the length of the first minor axis. Alternatively, the length of the third major axis may be longer than the length of the second major axis, and the length of the third minor axis may be shorter than the length of the second minor axis. Alternatively, the length of the third major axis may be longer than the length of the first major axis and shorter than the length of the second major axis, and the length of the third minor axis may be shorter than the length of the first minor axis and longer than the length of the second minor axis.

[0073] Fig. 9 is an explanatory diagram illustrating an example of the shape of the radiating element 630 in a modified example. The direction perpendicular to the paper surface of Fig. 9 is parallel to the K direction. The radiating element 630 in Fig. 9 has a fourth radiating region, a fifth radiating region, and a sixth radiating region in addition to the first radiating region, the second radiating region, and the third radiating region.

[0074] The fourth emitting region has a fourth minor axis that is a minor axis parallel to the first major axis and a fourth major axis that is a major axis perpendicular to the fourth minor axis. A part of the fourth emitting region is common to a part of the first emitting region. Another part of the fourth emitting region is common to a part of the second emitting region.

[0075] The fifth emitting region has a fifth minor axis that is parallel to the first major axis and shorter than the fourth minor axis, and a fifth major axis that is perpendicular to the fifth minor axis. A part of the fifth emitting region is common to a part of the first emitting region that is not common to the fourth emitting region. Another part of the fifth emitting region is common to a part of the second emitting region that is not common to the fourth emitting region.

[0076] The sixth emitting region has a sixth minor axis that is a minor axis parallel to the first major axis and a sixth major axis that is a major axis perpendicular to the sixth minor axis. A part of the sixth emitting region is common to a part of the first emitting region that is not common to the fourth emitting region and the fifth emitting region. Another part of the sixth emitting region is common to a part of the second emitting region that is not common to the fourth emitting region and the fifth emitting region.

[0077] In Fig. 9, region 711 is the first radiation region, region 712 is the second radiation region, region 713 is the third radiation region, region 721 is the fourth radiation region, region 722 is the fifth radiation region, and region 723 is the sixth radiation region. Regions 711 and 712 satisfy the major axis condition, the minor axis condition, and the direction condition. Fig. 9 shows that regions 721, 722, and 723 conform to the above-described definitions of the fourth radiation region, the fifth radiation region, and the sixth radiation region, respectively. Note that in Fig. 9, feed point 802 and feed point 803 are each an example of a feed point.

[0078] The fifth major axis may be shorter than the fourth major axis, but as shown in the example of FIG. 9, the fifth major axis may be longer than the fourth major axis.

[0079] Fig. 10 is a diagram showing an example of the results of an experiment using antenna 600 including radiating element 630 in a modified example. More specifically, Fig. 10 is a diagram showing an example of the results of measuring S11 for antenna 600 including radiating element 630 of Fig. 9 (hereinafter referred to as the "second Kawasaki antenna"). In the experiment, the lengths of radiating element 630 included in the second Kawasaki antenna were L1 = 67 mm, L2 = 80 mm, L3 = 72 mm, W1 = 29 mm, W2 = 15 mm, and W3 = 10 mm. Furthermore, the length of the fourth major axis was L4 = 67 mm, the length of the fourth minor axis was W4 = 29 mm, the length of the fifth major axis was L5 = 80 mm, the length of the fifth minor axis was W5 = 15 mm, the length of the sixth major axis was L6 = 72 mm, and the length of the sixth minor axis was W6 = 10 mm.

[0080] The horizontal axis represents frequency, and the vertical axis represents S11. Note that in the experiment in which the results of Fig. 10 were obtained, the dielectric constant of dielectric substrate 620 was 4.6, and radiating element 630 was made of copper, whose conductivity was 5.8 × 10 7 [S / m].

[0081] In Figure 10, graph G3 shows the results for the No. 2 Kawasaki antenna, and graph G2 shows the results for the comparison antenna. The comparison antenna differs from the No. 2 Kawasaki antenna in that it does not satisfy the minor axis condition and that W1 = W3 = 15 mm.

[0082] The results in Figure 10 show that the S11 of the No. 2 Kawasaki Antenna shows a peak at around 920 MHz that is lower than any of the peaks shown in graph G3. Therefore, the results in Figure 10 show that the No. 2 Kawasaki Antenna is able to improve the efficiency of energy conversion from electrical signals to radio waves compared to the comparative antenna.

[0083] The difference between the No. 2 Kawasaki Antenna and the comparison antenna is whether the short-axis condition is met or not. More specifically, the comparison antenna does not meet the short-axis condition, while the No. 2 Kawasaki Antenna does. This difference results in improved efficiency in converting energy from electrical signals to radio waves.

[0084] 10, there are six regions, from the first emitting region to the sixth emitting region, but there does not necessarily have to be six. It is sufficient that there are the first emitting region and the second emitting region, and for example, there may also be a fourth emitting region or a fifth emitting region.

[0085] Note that one end of the third radiation region parallel to the major axis and one end of the fourth radiation region parallel to the major axis do not necessarily need to be located on the same axis as shown in FIG. 9 (i.e., their ends are aligned). This applies not only to the third and fourth radiation regions but also to the fifth and sixth radiation regions. However, having the ends aligned results in a higher gain. If the ends are not aligned, the number of sides of the radiation region increases, dispersing power. Therefore, if the ends are not aligned, less power flows in the major axis direction than if the ends are aligned. As described above, the radiation portion emits radio waves at a resonant frequency determined by the length of the major axis in the major axis direction, so the more power flows in the major axis direction, the higher the gain. Therefore, having the ends aligned is more desirable than not having the ends aligned.

[0086] The direction of the first major axis does not necessarily have to be perpendicular to the sheet transport direction, but may be parallel to it. Furthermore, the direction of the first major axis does not necessarily have to be perpendicular or parallel to the sheet transport direction. The direction of the first major axis may be perpendicular or parallel to a direction that forms a predetermined angle with the sheet transport direction (hereinafter referred to as the "reference direction"). For example, the X-axis direction in Figures 7 and 9 may be perpendicular to the reference direction, and the Y-axis direction in Figures 7 and 9 may be parallel to the reference direction.

[0087] Whether the radio frequency tag communication device 201 will use the power feeder 641 or 642 to exchange information with the radio frequency tag when using the radio frequency tag communication device 201 may be determined in advance by the user, or may be determined by the radio frequency tag communication device 201 executing a predetermined process. When the user determines in advance, for example, the user determines to use the power feeder 640, which emits polarized waves with a polarization plane parallel to the orientation of the radio frequency tag on the sheet to be processed, for exchanging information.

[0088] When the RFID tag communication device 201 makes a decision, the predetermined process is, for example, the following decision process. In the decision process, first, under the control of the RFID tag communication control unit 501, the power feeder 640 to which voltage is applied is switched at a predetermined cycle before exchanging information with the RFID tag. Then, each time the power feeder 640 is switched, radio waves are emitted and the strength of the radio waves reflected by the RFID tag is measured. The RFID tag communication control unit 501 decides the timing of the switching. The reflected waves are radio waves emitted by the RFID tag. The RFID tag communication control unit 501 measures the reflected waves. The RFID tag communication control unit 501 ends the switching process when a reflected wave of a predetermined strength or greater is observed. The RFID tag communication control unit 501 decides that the power feeder 640 to which voltage was applied at the time the switching is completed is the power feeder 640 to be used for exchanging information with the RFID tag.

[0089] The transmitting / receiving circuit unit 502 is an example of a radiation control unit. The registration rollers 31 are an example of a conveying member.

[0090] The antenna 600 is an example of a microstrip antenna. The X-axis direction, the Y-axis direction, the direction parallel to the reference direction, and the direction perpendicular to the reference direction are all examples of the first direction.

[0091] The functions of the image forming apparatus 10 or the RFID tag communication control unit 501 in the above-described embodiments may be implemented by a computer. In this case, a program for implementing the functions may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into a computer system. Furthermore, the term "computer-readable recording medium" may also include media that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or media that store programs for a fixed period of time, such as volatile memory within a computer system that serves as a server or client. The program may also be a program that implements part of the above-described functions, or may be a program that can be implemented in combination with a program already stored in the computer system.

[0092] According to at least one of the embodiments described above, by having the RFID tag communication device 201, it is possible to reduce the chances of not being able to exchange information with a RFID tag due to differences in the type of RFID tag.

[0093] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

[0094] The following discloses additional notes relating to the above-described embodiments.

[0095] (Appendix 1) a radiating element having a first radiating region having a first major axis that is a major axis parallel to a first direction and a first minor axis that is a minor axis perpendicular to the first major axis, and a second radiating region having a second major axis that is a major axis parallel to the first direction and longer than the first major axis, and a second minor axis that is a minor axis perpendicular to the second major axis; Equipped with The length of the second minor axis is shorter than the length of the first minor axis. Microstrip antenna. (Appendix 2) a third radiation region having a third major axis that is a major axis parallel to the first direction and has a length different from at least one of the first major axis and the second major axis, and a third minor axis that is a minor axis perpendicular to the third major axis; 2. The microstrip antenna of claim 1, further comprising: (Appendix 3) The length of the third major axis is the same as the length of the first major axis, and the length of the third minor axis is the same as the length of the first minor axis. 1. The microstrip antenna of claim 2. (Appendix 4) The length of the third major axis is equal to the length of the second major axis, and the length of the third minor axis is equal to the length of the second minor axis. 1. The microstrip antenna of claim 2. (Appendix 5) The length of the third major axis is shorter than the length of the first major axis, and the length of the third minor axis is longer than the length of the first minor axis. 1. The microstrip antenna of claim 2. (Appendix 6) The length of the third major axis is longer than the length of the second major axis, and the length of the third minor axis is shorter than the length of the second minor axis. 1. The microstrip antenna of claim 2. (Appendix 7) The length of the third major axis is longer than the length of the first major axis and shorter than the length of the second major axis, and the length of the third minor axis is shorter than the length of the first minor axis and longer than the length of the second minor axis. 1. The microstrip antenna of claim 2. (Appendix 8) the radiating element has a fourth radiating region having a fourth minor axis that is a minor axis parallel to the first direction and a fourth major axis that is a major axis perpendicular to the fourth minor axis, a part of the fourth emitting region and a part of the first emitting region are common to each other; Another part of the fourth radiation region and a part of the second radiation region are common to each other. 8. The microstrip antenna of any one of claims 1 to 7. (Appendix 9) the radiating element further includes a fifth radiating region having a fifth minor axis that is a minor axis parallel to the first direction and shorter than the fourth minor axis, and a fifth major axis that is a major axis perpendicular to the fifth minor axis; a part of the fifth emitting region and a part of the first emitting region that is not common to the fourth emitting region are common to each other; Another part of the fifth emitting region and a part of the second emitting region that is not common to the fourth emitting region are common to each other. 9. The microstrip antenna of claim 8. (Appendix 10) the fifth major axis is longer than the fourth major axis; 10. The microstrip antenna of claim 9. (Appendix 11) a microstrip antenna comprising a radiating element having a first radiating region having a first major axis that is a major axis parallel to a first direction and a first minor axis that is a minor axis perpendicular to the first major axis, and a second radiating region having a second major axis that is a major axis parallel to the first direction and longer than the first major axis, and a second minor axis that is a minor axis perpendicular to the second major axis, wherein the length of the second minor axis is shorter than the length of the first minor axis; A wireless tag communication device comprising: (Appendix 12) a conveying member that conveys a sheet; a radio tag communication device including a microstrip antenna, the radio tag communication device including a radiating element having a first radiating region having a first major axis that is a major axis parallel to a first direction and a first minor axis that is a minor axis perpendicular to the first major axis, and a second radiating region having a second major axis that is a major axis parallel to the first direction and longer than the first major axis, and a second minor axis that is a minor axis perpendicular to the second major axis, the length of the second minor axis being shorter than the length of the first minor axis; A sheet processing apparatus comprising: [Explanation of symbols]

[0096] 10...image forming apparatus, 100...controller, 201...wireless tag communication device, 501...wireless tag communication controller, 502...transmitter / receiver circuit section, 503...interface section, 504...modulator section, 505...transmitting amplifier, 506...receiving amplifier, 507...demodulator section, 508...circulator, 509...selector switch, 600...antenna, 610...ground conductor plate, 620...dielectric substrate, 630...radiating element, 640, 641, 642...power feeder line

Claims

1. a radiating element having: a first radiating region having a first major axis that is a major axis parallel to a first direction and a first minor axis that is a minor axis perpendicular to the first major axis; and a second radiating region having a second major axis that is a major axis parallel to the first direction and longer than the first major axis, and a second minor axis that is a minor axis perpendicular to the second major axis; Equipped with The length of the second minor axis is shorter than the length of the first minor axis. Microstrip antenna.

2. a third radiation region having a third major axis parallel to the first direction and having a length different from at least one of the first major axis and the second major axis, and a third minor axis perpendicular to the third major axis; The microstrip antenna of claim 1 further comprising:

3. the radiating element has a fourth radiating region having a fourth minor axis that is a minor axis parallel to the first direction and a fourth major axis that is a major axis perpendicular to the fourth minor axis, a part of the fourth emitting region and a part of the first emitting region are common to each other, Another part of the fourth radiation region and a part of the second radiation region are common to each other.

3. A microstrip antenna according to claim 1 or 2.

4. a microstrip antenna comprising a radiating element having a first radiating region having a first major axis that is a major axis parallel to a first direction and a first minor axis that is a minor axis perpendicular to the first major axis, and a second radiating region having a second major axis that is a major axis parallel to the first direction and longer than the first major axis, and a second minor axis that is a minor axis perpendicular to the second major axis, wherein the length of the second minor axis is shorter than the length of the first minor axis; A wireless tag communication device comprising:

5. a conveying member that conveys a sheet; a radio tag communication device including a microstrip antenna, the radio tag communication device including a radiating element having a first radiating region having a first major axis that is a major axis parallel to a first direction and a first minor axis that is a minor axis perpendicular to the first major axis, and a second radiating region having a second major axis that is a major axis parallel to the first direction and longer than the first major axis, and a second minor axis that is a minor axis perpendicular to the second major axis, the length of the second minor axis being shorter than the length of the first minor axis; A sheet processing apparatus comprising:

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