LOW POWER RADIO FREQUENCY TRANSMITTER WITH CONTROLLABLE GAIN

• US 20020028663A1
• Filed: 12/14/1998
• Published: 03/07/2002
• Est. Priority Date: 12/14/1998
• Status: Active Grant

• Current Assignee: Lear Automotive Dearborn, Incorporated (Lear Corporation)
• Original Assignee: Lear Automotive Dearborn, Incorporated (Lear Corporation)
• Inventors: TANG, QINGFENG
• Granted Patent: US 6,597,897 B2
• Time in Patent Office: Days
• US Class Current: 455/127.2
• CPC Class Codes: B60R 25/24 using electronic identifiers containing a code not memorised by the user
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• CPC Class Codes: G07C 9/00182 operated with unidirectional data transmission between data carrier and locks
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04

Abstract

A low power transmitter useful for vehicle remote keyless entry systems, for example, includes a transmitter circuit portion and a gain control circuit portion. The gain control circuit portion preferably includes an inductive load that introduces a resonant frequency that provides radio frequency gain control. The transmitter circuit portion preferably includes a transistor having a collector node and an emitter node. The gain controller circuit preferably includes a capacitive load coupled between the emitter node and the collector node of the transistor. The inductive load preferably is coupled between the emitter node of the transistor and ground.

Claims

1. A remote transmitter for use in a remote keyless entry system, comprising:

a signal transmitter circuit portion having an input for receiving data to be incorporated into a signal and an output for transmitting a radio frequency signal to a remote receiver; and

a gain control circuit coupled with the output of the signal transmitter portion and including an inductive load that introduces a frequency that controls a gain associated with the signal transmitter portion when generating the transmitted signal.

2. The transmitter of claim 1, wherein the signal transmitter portion output includes a transistor having a base node, a collector node and an emitter node and wherein the gain control circuit includes a capacitive load connected in series across the collector and emitter nodes.

3. The transmitter of claim 2, wherein the gain control circuit inductive load is coupled between the emitter node and ground.

4. The transmitter of claim 3, wherein the gain control circuit includes a capacitive load, and a resistive load each coupled between the emitter node and ground.

5. The transmitter of claim 4, wherein the gain control circuit inductive load is in parallel with the capacitive load and the inductive load is in series with the resistive load.

6. The transmitter of claim 4, wherein the gain control circuit inductive load is in series with the capacitive load and in series with the resistive load.

7. A remote transmitter for use in a security system that includes radio frequency signal communications, comprising:

a transmitter circuit portion having an input that receives data to be incorporated into a radio frequency signal and an output for transmitting the radio frequency signal including a transistor amplifier having a base node, a collector node and an emitter node; and

a gain control circuit portion including a capacitive load coupled across the collector node and the emitter node and a voltage dividing load coupled between the emitter node and ground such that the gain control circuit modifies a gain associated with the transmitter circuit portion.

8. The transmitter of claim 7, wherein the gain control circuit includes an inductive load, a second capacitive load, and a resistive load each coupled between the emitter node and ground.

9. The transmitter of claim 8, wherein the gain control circuit inductive load is in parallel with the second capacitive load and the inductive load is in series with the resistive load.

10. The transmitter of claim 8, wherein the gain control circuit inductive load is in series with the second capacitive load and in series with the resistive load.

11. The transmitter of claim 7, wherein the gain control circuit includes a second capacitive load and two resistive loads coupled between the emitter node and ground and wherein the second capacitive load is in series with one of the resistive loads and in parallel with the other resistive load.

12. The transmitter of claim 7, wherein the gain control circuit includes an inductive load and a second capacitive load in series and coupled between the emitter node and ground.

14. The transmitter of claim 13, wherein the gain controlling means includes an inductive load as part of the voltage dividing load.

13. A remote transmitter for use in a security system that includes radio frequency signal communications, comprising:

a transmitter circuit portion having an input that receives data to be incorporated into a radio frequency signal and an output for transmitting the radio frequency signal including a transistor amplifier having a base node, a collector node and an emitter node; and

means for controlling gain in the transmitter circuit portion that includes a capacitive load coupled across the collector node and the emitter node and a voltage dividing load coupled between the emitter node and ground.