Transmitter apparatus and communication system employing the same

• US 20030123567A1
• Filed: 11/07/2002
• Published: 07/03/2003
• Est. Priority Date: 12/27/2001
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Nakao, Yoshihiro, Shigemasa, Haruhiko
• Granted Patent: US 7,145,960 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

A transmitter apparatus has a modulator for modulating a carrier wave to produce a modulated wave having communication data superimposed thereon and a transmitter for transmitting the modulated wave to a receiver apparatus. Before starting communication, the transmitter apparatus transmits a predetermined dummy pulse to the receiver apparatus so as to bring the communication data restored by demodulation in the receiver apparatus into a logic state in which the communication data should be kept when no communication is taking place. This makes it possible to perform correct communication even if the communication data demodulated in the receiver apparatus before the start of communication is not kept in the logic state in which it should be kept when no communication is taking place.

Claims

1. A transmitter apparatus comprising:

a modulator for modulating a carrier wave to produce a modulated wave having communication data superimposed thereon; and

a transmitter for transmitting the modulated wave to a receiver apparatus,

wherein, before starting communication, the transmitter apparatus transmits a predetermined dummy pulse to the receiver apparatus so as to bring communication data restored by demodulation in the receiver apparatus into a logic state in which the communication data should be kept when no communication is taking place.

2. A transmitter apparatus comprising:

a modulator for amplitude-modulating a carrier wave to produce a modulated wave having communication data superimposed thereon; and

a transmitter for transmitting the modulated wave to a receiver apparatus,

wherein the modulator, before reducing an amplitude of the modulated wave to indicate a head of the communication data, reduces the amplitude of the modulated wave temporarily and then restores the amplitude of the modulated wave to an original level so as to bring communication data restored by demodulation in the receiver apparatus into a logic state in which the communication data should be kept when no communication is taking place.

3. A transmitter apparatus as claimed in claim 2,

wherein a degree in which the amplitude of the modulated wave is reduced temporarily is equal to a degree in which the amplitude of the modulated wave is reduced during normal modulation.

4. A transmitter apparatus as claimed in claim 2,

wherein, immediately after the amplitude of the modulated wave is reduced temporarily, the modulated wave is kept unmodulated for a period equal to or shorter than a period required to transmit one-bit data.

5. A communication system comprising:

a transmitter apparatus as claimed in claim 2;

and

a receiver apparatus that receives the modulated wave and restores the communication data by demodulating the modulated wave, the receiving apparatus starting communication by detecting a transition of the communication data from the logic state in which the communication data should be kept when no communication is taking place to a predetermined logic state.

6. A communication system as claimed in claim 5,

wherein the transmitter apparatus and the receiver apparatus are a non-contact-type IC card and a reader/writer apparatus that performs data communication with the IC card.