Input device with capacitive antenna

Abstract

An input device having a housing and electronic circuitry for detecting user inputs, and transmitting signals corresponding to those inputs to an electronic device, such as a computer. An antenna is provided for transmitting or receiving signals. A hand detection circuit is provided, which uses said antenna for detecting the proximity of a user's hand to the housing and producing a hand detect signal in response. In one embodiment, the antenna is a capacitive antenna. A capacitor is switched in parallel with the antenna when it is used in antenna mode, so that the impact on the antenna signaling of the capacitance of a user's hand is minimized. In one embodiment, a sleep mode is provided for the electronic circuitry to conserve power. The hand detect signal will awaken the input device from its sleep mode.

What is claimed is:  
     
         1 . An input device comprising: 
 a housing;    user input electronic circuitry for detecting user inputs and transmitting signals corresponding to said inputs to an electronic device;    an antenna;    an antenna circuit coupled to said antenna for transmitting or receiving signals; and    a hand detection circuit coupled to said antenna for detecting the proximity of a user's hand to said housing using said antenna and producing a hand detect signal.    
     
     
         2 . The input device of  claim 1  wherein said antenna is an inductive antenna.  
     
     
         3 . The input device of  claim 1  wherein said antenna is a capacitive antenna.  
     
     
         4 . The input device of  claim 3  further comprising: 
 a capacitor; and  
 a switch for coupling said capacitor in parallel with said capacitive antenna when said antenna is used for transmitting or receiving signals instead of being used for hand detection.  
 
     
     
         5 . The input device of  claim 4  wherein said capacitor has a value more than double the capacitance of a hand.  
     
     
         6 . The input device of  claim 4  wherein said capacitor has a value more than ten times the capacitance of a hand.  
     
     
         7 . The input device of  claim 4  wherein said capacitor has a value of at least 10 pico farads.  
     
     
         8 . The input device of  claim 1  further comprising: 
 a sleep-mode circuit, coupled to said user input electronic circuitry, for activating a reduced power operation of said user input electronic circuitry;  
 said sleep mode circuit being responsive to said hand detect signal to awaken said user input electronic circuitry from said reduced power operation.  
 
     
     
         9 . The device of  claim 1  wherein said input device is a pointing device and said electronic device is a computer.  
     
     
         10 . The device of  claim 1  wherein: 
 said antenna comprises first and second electrodes on said housing for capacitive connection with a user's hand; and  
 said hand detection circuit comprises  
 a first circuit, coupled to said first electrode, for determining an amount of time for charging of a capacitance connected to said first circuit, and  
 a second circuit, coupled to said second electrode, for determining an amount of time for discharging of a capacitance connected to said second circuit.  
 
     
     
         11 . The device of  claim 10  wherein said first circuit comprises: 
 a comparator;  
 a controller coupled to an output of said comparator;  
 a voltage divider feedback circuit coupled between an output and a reference voltage input of said comparator;  
 a detection capacitor coupled between said first electrode and a signal input of said comparator; and  
 a switching circuit selectively coupling said signal input of said comparator to high and low voltage supplies.  
 
     
     
         12 . The device of  claim 1  wherein said input device is a mouse, and said user input electronic circuitry is an optical module for reflecting light off a surface and detecting movement of said mouse relative to said surface.  
     
     
         13 . An input device comprising: 
 a housing;    user input electronic circuitry for detecting user inputs and transmitting signals corresponding to said inputs to an electronic device;    a capacitive antenna;    an antenna circuit coupled to said antenna for transmitting or receiving signals;    a hand detection circuit coupled to said antenna for detecting the proximity of a user's hand to said housing using said antenna and producing a hand detect signal;    a capacitor; and    a switch for coupling said capacitor in parallel with said capacitive antenna when said antenna is used for transmitting or receiving signals instead of being used for hand detection.    
     
     
         14 . An input device comprising: 
 a housing;    user input electronic circuitry for detecting user inputs and transmitting signals corresponding to said inputs to an electronic device;    a capacitive antenna;    an antenna circuit coupled to said antenna for transmitting or receiving signals;    a hand detection circuit coupled to said antenna for detecting the proximity of a user's hand to said housing using said antenna and producing a hand detect signal;    a capacitor, said capacitor having a value of at least 10 pico farads;    a switch for coupling said capacitor in parallel with said capacitive antenna when said antenna is used for transmitting or receiving signals instead of being used for hand detection;    a sleep-mode circuit, coupled to said user input electronic circuitry, for activating a reduced power operation of said user input electronic circuitry; and    said sleep mode circuit being responsive to said hand detect signal to awaken said user input electronic circuitry from said reduced power operation.    
     
     
         15 . A method for operating an input device comprising: 
 detecting user inputs and transmitting signals corresponding to said inputs to an electronic device external to said input device;    transmitting or receiving signals using an antenna; and    detecting the proximity of a user's hand to said input device using said antenna and producing a hand detect signal.    
     
     
         16 . The method of  claim 15  wherein said detecting the proximity of a user's hand detects a change in capacitance due to said proximity of a user's hand.  
     
     
         17 . The method of  claim 16  further comprising switching a capacitor in parallel with said antenna when said antenna is used for transmitting or receiving signals instead of being used for hand detection.