Granted Patent B2

US 7,359,448 · App. 10/225,468 · Granted Apr 15, 2008

Abstract

Claims (19)

1. A remote transmitter system for vehicle applications, the system comprising:

a remote transmitter for carrying by a user, the remote transmitter being operative to transmit an amplitude modulated signal at a plurality of different carrier frequencies; and

a receiver for mounting on a vehicle and receiving the amplitude modulated signal wherein the receiver is configured to receive the amplitude modulated signal at a selectable carrier frequency, the receiver including a received signal strength indicator and a data decoder, the receiver being programmed to select the carrier frequency by detecting noise due to unwanted frequency modulated signals when the received signal strength indicator provides a constant direct current (DC) voltage, detecting noise due to unwanted amplitude modulated signals when the data decoder provides data that is of an unexpected type, and changing the selected carrier frequency when either noise becomes excessive.

2. The system of claim 1 wherein the receiver includes a phase locked loop circuit for selecting the carrier frequency.

3. The system of claim 1 wherein the transmitted amplitude modulated signal is on-off keyed.

4. The system of claim 1 wherein the transmitter is configured to transmit the amplitude modulated signal at the plurality of different carrier frequencies at the same time.

5. The system of claim 1 wherein the transmitter is configured to transmit the amplitude modulated signal at the plurality of different carrier frequencies sequentially.

6. A remote transmitter method for vehicle applications, the method comprising:

transmitting an amplitude modulated signal at a plurality of different carrier frequencies;

selecting a carrier frequency;

receiving the amplitude modulated signal at the selected carrier frequency;

detecting noise due to unwanted frequency modulated signals when a received signal strength at the selected carrier frequency is a constant;

detecting noise due to unwanted amplitude modulated signals based-on when a decoded data stream at the selected carrier frequency is of an unexpected type;

changing the selected carrier frequency when either noise becomes excessive.

7. The method of claim 6 wherein the transmitted amplitude modulated signal is on-off keyed.

8. The method of claim 6 wherein transmitting further comprises:

transmitting the amplitude modulated signal at the plurality of different carrier frequencies at the same time.

9. The method of claim 6 wherein transmitting further comprises:

transmitting the amplitude modulated signal at the plurality of different carrier frequencies sequentially.

Assignments (10)