Communications: radio wave antennas – Antennas – High frequency type loops
Reexamination Certificate
2002-02-05
2003-08-12
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
High frequency type loops
C343S741000, C343S867000, C343S876000
Reexamination Certificate
active
06606068
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to antenna loops of the electromagnetic-induction system, and more particularly to a layout for multi-antenna loops of the electromagnetic-induction system.
2. Description of the Prior Art
Because a handwriting recognition system could replace the mouse, and is more suitable than the mouse to let the user input words and patterns by user's hands, improvement of the handwriting recognition system is a hot and important field of current computer technology. The original intention of the handwriting recognition system is to replace the mouse. As usual, to enhance the user's convenience, a handwriting recognition system would usually replace the mouse by both wireless pen and tablet. Herein, the pen nib of the wireless pen usually corresponds to the left button of the mouse. Conventional handwriting recognition systems have been developed for many years, but these products are applied to perform only one function, such as drawing or inputting a word.
In the conventional system with electromagnetic-induction, there are usually a digitizer tablet and a transducer/cursor in the form of a pen or a puck. As is well known, there are two operation modes for determining the position of a pointing device on the surface of a digitizer tablet, wherein one is a relative mode, and the other is an absolute mode. A mouse device operates in a relative mode. The computer sensing the inputs from a mouse recognizes only relative movements of the mouse in X and Y directions as it is slid over the surface on which it is resting. If the mouse is lifted and repositioned on the surface, no change in the signal to the computer will be detected. A common approach uses a sensing apparatus inside the mouse to develop a pair of changing signals corresponding to the longitudinal and transversal movements of the mouse. On the contrary, a cursor device in a digitizer tablet system, such as wireless pen, operates in an absolute mode. If a cursor device is lifted and moved to a new position on its supporting surface, its signal to a computer will change to reflect the new absolute position of the cursor device. Nowadays, various methods have been used to determine the position of a cursor device on the surface of its supporting tablet, wherein one common skill which is applied for the absolute mode is electromagnetic field sensing. Early transducer/cursors were connected to the tablet by means of a multi-conductor cable through which the position and button/pressure information are transferred virtually without any problem. The cordless transducer/cursors in some of the prior arts have attempted to use frequency and/or phase changes to transmit the non-positional status of the transducer/cursor functions such as buttons pushed, pen pressure, or the like. However, if there is no sophisticated processing, frequency and phase changes are very prone to false reading resulting from several outside factors such as metal objects, noise, electromagnetic wave and so on. These problems become more apparent, especially in a larger digitizer tablet. Improvements have also been made in the prior arts to allow a user to use pointing devices on a digitizer tablet system in dual modes of operation that can provide information of either a relative movement or an absolute position under the control of the user.
Usually, a handwriting recognition system is a device with electromagnetic-induction. Conventional electromagnetic-induction device comprises: an electromagnetic pen and a tablet. There is an oscillating circuit that consists of LC in the electromagnetic pen. If the pen point is touched, the amount of inductance will be changed that results in the variation of oscillating frequency. The amount of inductance is increased when touching the pen point and increasing pressure so the variation of oscillating frequency is also increased. Therefore, the variation of the pressure on the pen point can be detected by way of the variation of oscillating frequency. There are two switches on the sidewall of the electromagnetic pen, the emitted frequency of the electromagnetic pen can be changed with the capacitance variation of the LC device that is produced by pushing down or setting free the switches. Furthermore, the tablet comprises a detector, an amplifier and an analog-digital converter. In the conventional tablet, there is a detected loop in the center region of the tablet, with antenna loops located on the double faces of the detecting loop, wherein the antenna loops are equidistantly arranged in order by way of using array. The main purpose of the detecting loop is only applied to receive the electromagnetic wave that is emitted by the electromagnetic pen. When the electromagnetic pen emits the electromagnetic wave, the antenna loops receive the electromagnetic wave, and then the tablet can obtain correlative information by the electromagnetic induction.
In general, antenna loops and layout thereof in the conventional electromagnetic-induction device arranges antennas as check network that are distributed with equidistance in the X-direction and Y-direction of two-dimensional Cartesian coordinates to induce the electromagnetic pen and calculate the absolute position thereof. Refer to
FIG. 1A
, it shows a layout for antenna loops distributed in the X-direction of two-dimensional Cartesian coordinates, wherein one terminal of each of the antenna loops
110
A is connected to each switch (X
1
to X
25
) and the other terminal is electrically coupled with a ground wire
105
A, whereby the reduced signal of each of the antenna loops
110
A can be detected by controlling the switches (X
1
to X
25
). Because of the inverse proportion of the magnetic field intensity to the square of distance the electromagnetic pen that can emit electromagnetic wave is away from the tablet to result in more and more weak induced signal that is received by antenna loops; on the contrary, the induced signal that is received by antenna loops is an increasing number of intensity when the electromagnetic pen approaches the tablet. Therefore, CPU of the tablet scans one by one and in turn each of the antenna loops to analyze intensity of induced signals that are received by each antenna loops, so as to detect the position where the cordless pen is located and calculate the coordinates thereof.
However, there is an increasing number of antenna loops in the tablet having much larger area so a great amount of antenna switches is necessary. Nowadays, a method that can decrease amount of antenna switches by forming n-shaped sections
120
in the same antenna loop is provided. Refer to
FIG. 1B
, each of antenna loops (X
1
to X
9
and XA to XC) distributed along the X-direction of two-dimensional Cartesian coordinates (X, Y), and each of antenna loops (X
1
to X
9
and XA to XC) comprises a plurality of logical sections
120
. Regarding to each of the antenna loops (X
1
to X
9
and XA to XC) distributed in the same direction, the adjacent logical sections of each logical section
120
therein belongs to different antenna loops (X
1
to X
9
and XA to XC), whereby the position of electromagnetic pen can be located on the n-shaped section of which the antenna loop is. For example, for the n-shaped section denoted by numbers
120
A of the antenna loop X
5
, its adjacent n-shaped sections
130
and
140
belong to the antenna loops X
4
and X
6
respectively. However, for the next logical section denoted by number
120
B of the antenna loop X
5
, its adjacent n-shaped logical sections
150
and
160
belong to the antenna loops XC and X
2
respectively. Thus, the position of the pen can be decided by the induction voltage produced by physical antenna loops X
5
, X
4
, X
6
, XC and X
2
whether the electromagnetic pen (not shown) moves above the n-shaped section denoted by number
120
A of the antenna loop X
5
, or above the n-shaped logical section denoted by number
120
B of the antenna loop X
5
. As foregoing description, amount of the switches in
FIG. 1B
, suc
Chao Ching-Chuan
Chen Chih-An
Wang I-Wen
Aiptek International Inc.
Phan Tho
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