The present invention relates to an electromagnetic antenna loop layout, and more particularly to an electromagnetic antenna loop layout with integrated terminals of the antenna loops.
Conventional coordinate input apparatus such as a digitizer or a digital tablet usually include a pointer such as a stylus or an electromagnetic pen and an electromagnetic antenna loop layout. The electromagnetic antenna loop layout includes a plurality of sensor coils or antenna loops arranged along x and y axes to constitute an induction plane. The pointer usually includes a resonance circuit or signal receiving, processing and transmitting circuits therein depending on the types of the pointer. The coordinates of the pointer are obtained through the transmitting and receiving of electromagnetic signals between the pointer and the antenna loops.
Each sensor coil or antenna loop of the coordinate input apparatus comprises conductive lines to transmit electromagnetic signals to the pointer and receive electromagnetic signals from the pointer. Each antenna loop has two terminals. One of the terminals connects to a switch and finally to a control circuit, while the other terminal connects to a ground end (COM). As shown in
The portions of each antenna loop connecting to the switch and the ground end occupy partial area of the electromagnetic antenna board of the coordinate input apparatus. The area of the electromagnetic antenna board occupied by the antenna loops is a detectable area where the coordinates of a pointer can be obtained through the transmitting and receiving of electromagnetic signals between the pointer and the antenna loops. The area of the electromagnetic antenna board occupied by the portions of each antenna loop connecting to the switch and the ground end is an undetectable area or an invalid area. Moreover, the sizes of the connector, the printed circuit board having the electromagnetic antenna board and the control circuit board depend on the total number of the terminals, and thus the total cost also increases as the total number of the terminals increases. Particularly for a large size coordinate input apparatus with a large number of antennal loops and terminals, how to enlarge the detectable area and to shrink the invalid area is a crucial issue.
In order to solve the above-mentioned drawbacks of the conventional electromagnetic antenna loop layout, a new electromagnetic antenna loop layout is thus provided to enlarge the detectable area and to shrink the invalid area.
An object of the present invention is to provide a new electromagnetic antenna loop layout to reduce the total number of terminals such that the total number of terminals of the antenna loops can be decreased from 2(Nx+Ny) to 3/2(Nx+Ny).
According to the object, one embodiment of the present invention provides an electromagnetic antenna loop layout of an electromagnetic coordinate input apparatus. The electromagnetic antenna loop layout comprises a plurality of antenna loops parallel arranged along x and y axes, wherein a first terminal of each the antenna loop connects to a switch and second terminals of at least two adjacent antenna loops connect to a ground end.
The present invention further provides an electromagnetic coordinate input apparatus comprising a pointer, a micro controller, a signal processing circuit and an electromagnetic antenna loop layout. The electromagnetic antenna loop layout comprises a plurality of antenna loops arranged parallel to each other, wherein a first terminal of each the antenna loop connects to a switch and second terminals of every two antenna loops connect to a ground end, each the switch is controlled by the micro controller to switch the antenna loop to transmitting and receiving electromagnetic signals between the pointer and the electromagnetic antenna loop layout, the signal processing circuit processes the electromagnetic signals received by the antenna loops.
The accompanying drawings illustrate various embodiments of the present invention and are a part of the specification. The illustrated embodiments are merely examples of the present invention and do not limit the scope of the invention.
The detailed description of the present invention will be discussed in the following embodiments, which are not intended to limit the scope of the present invention, but can be adapted for other applications. While drawings are illustrated in details, it is appreciated that the scale of each component may not be expressly exactly.
In one embodiment of the invention, an electromagnetic coordinate input apparatus comprises a micro controller, a plurality of sensor coils or antenna loops arranged along x and y axes on an electromagnetic antenna board and a signal processing circuit including, but not limited to a signal amplifier, a filter, a rectifier, a phase detector and an analog to digital converter. The embodiment can be practiced via any well-known prior art, and one with ordinary skill in the art can make and use the invention based on ordinary level of skill. Each antenna loop on the electromagnetic antenna board connects to a switch controlled by a control circuit to switch the antenna loop to transmitting and receiving electromagnetic signals. The control circuit is drove by the micro controller. The control circuit controls a frequency generating circuit and a selecting circuit to switch and select antenna loops to transmit electromagnetic signals. The electromagnetic signals are transmitted to a pointer to resonate with a resonance circuit (batteryless pointer) or to activate a control circuit of the pointer (pointer with battery) to transmit electromagnetic signals. When the antenna loops temporarily interrupt transmitting electromagnetic signals, the pointer transmits electromagnetic signals back to the antenna loops and received by the antenna loops. The electromagnetic signals received by the antenna loops are then processed and analyzed by the signal amplifier, the filter, the rectifier, the phase detector and the analog to digital converter.
When the pointer moves on the electromagnetic antenna board, the pointers and the antennas loops repeatedly transmit and receive signals continuously and alternatively.
The antenna loops on the trace of the pointer are switched by the micro controller sequentially to transmit and receive signals continuously and alternatively. The micro controller sequentially switching the antenna loops is also referred as scanning. The sequentially switching of the antenna loops is performed by multiplexers controlled by the micro controller.
The position detection of the pointers begins from detecting no any signals from the pointers to completely calculating the coordinates of the pointers including x and y coordinates. The micro controller controls a signal/frequency generating circuit and a selection circuit to sequentially switch the antenna loops to transmit and receive signals alternatively to perform a full region scan, and thus any signal received by any antenna loop can be detected and processed. If the pointers are on the detection region of the electromagnetic antenna board, the antenna loops corresponding to the positions of the pointers will receive signals with maximum values, and thus the positions of the pointers can be roughly located. Then the micro controller controls the signal/frequency generating circuit and the selection circuit to sequentially switch the antenna loops within a certain region with the position of the pointer as the center to transmit and receive signals alternatively to perform a partial region scan. The partial region scan only switches the antenna loops adjacent the antenna loops receiving the signals with maximum values to transmit and receive signals. The coordinates of the pointers are located if signals with maximum values are received and the accurate coordinates of the pointers are calculated through further signal processing.
Each antenna loop of the electromagnetic antenna board has two terminals, wherein one of the terminals connects to a switch and finally to a control circuit, while the other terminal connects to a ground end (COM). The portions of each antenna loop connecting to the switch and the ground end occupy partial area of the electromagnetic antenna board of the coordinate input apparatus. The area of the electromagnetic antenna board occupied by the antenna loops is a detectable area where the coordinates of a pointer can be obtained through the transmitting and receiving of electromagnetic signals between the pointer and the antenna loops. The area of the electromagnetic antenna board occupied by the portions of each antenna loop connecting to the switch and the ground end is an invalid area. For a coordinate input apparatus, the detectable area must be enlarged and the invalid area must be decreased.
Although specific embodiments have been illustrated and described, it will be appreciated by those skilled in the art that various modifications may be made without departing from the scope of the present invention, which is intended to be limited solely by the appended claims.
Number | Date | Country | Kind |
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099114318 | May 2010 | TW | national |