Passive keyless entry system

• US 20050017840A1
• Filed: 07/22/2004
• Published: 01/27/2005
• Est. Priority Date: 07/25/2003
• Status: Abandoned Application

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Masudaya, Hideki
• Application Number:
  US10/896,450
• Publication Number:
  US 20050017840A1
• Time in Patent Office: Days
• US Class Current: 340/5.640
• 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

Abstract

The portable device 2 is provided with a control IC 3, an antenna 4 having both ends thereof connected to input and output terminals of the control IC 3 for wirelessly transmitting or receiving signals, a level detector 5 for detecting the receiving level of the antenna 4, a Qdump circuit 6 that operates only when the level detector 5 detects the receiving level which exceeds an allowable value of the control IC 3 and that varies the quantity of Qdump in accordance with the receiving level of the antenna 4, and a time constant circuit 7 or a latch circuit 8 for holding the Qdump circuit 6 in its operational state in an OFF period of an LF modulation signal.

Claims

1. A passive keyless entry system comprised of a fixed device and a portable device, wirelessly transmitting a wake-up signal and a data signal from the fixed device to the portable device, and wirelessly transmitting a command signal from the portable device, which has received the wake-up signal and the data signal, to the fixed device, thereby remotely controlling a device to be controlled provided at the fixed device, wherein the portable device comprises:

a detector circuit;

an antenna having both ends thereof connected to input and output terminals of the detector circuit for wirelessly transmitting or receiving signals;

a level detector for detecting athe receiving level of the antenna;

a Qdump circuit that operates only when the level detector detects a receiving level which exceeds an allowable value of the detector circuit, and that varies the quantity of Qdump in accordance with the receiving level of the antenna; and

an operation holding circuit for holding the Qdump circuit in an operational state, even in an OFF period when signals are not transmitted from the fixed device.

2. The passive keyless entry system according to claim 1, wherein the operation holding circuit includes a time constant circuit.

3. The passive keyless entry system according to claim 1, wherein the operation holding circuit includes a latch circuit.