Communications: electrical – Continuously variable indicating – With meter reading
Reexamination Certificate
1999-08-06
2004-03-09
Zimmerman, Brian (Department: 2635)
Communications: electrical
Continuously variable indicating
With meter reading
C341S176000, C340S870030, C455S115200
Reexamination Certificate
active
06703941
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to radio frequency (RF) trainable transmitters that are capable of learning the characteristics of a received RF signal, storing the characteristics in memory, and re-creating and transmitting the learned signal based upon the stored characteristics.
RF trainable transmitters have many applications. The primary application is to physically and permanently incorporate the trainable transmitter in a vehicle accessory, such as a visor, rearview mirror, or overhead console, in order to allow the trainable transmitter to be used to learn a garage door opening RF signal for subsequent transmission to the garage door opening mechanism mounted in a garage. As disclosed in U.S. Pat. No. 5,903,226, another application of RF trainable transmitters is to control household lights and appliances.
RF trainable transmitters are capable of learning the RF carrier frequency, modulation scheme, and data code of an existing portable remote RF transmitter associated with an existing receiving unit located in the vehicle owner's garage. Thus, when a vehicle owner purchases a new car having such a trainable transmitter, the vehicle owner may train the transmitter to the vehicle owner's existing clip-on remote RF transmitter without requiring any new installation in the vehicle or home. Subsequently, the old clip-on transmitter can be discarded or stored.
Because the trainable transmitter is an integral part of a vehicle accessory, the storage and access difficulties presented by existent clip-on remote transmitters are eliminated. Some examples of trainable transmitters are disclosed in U.S. Pat. Nos. 5,442,340; 5,479,155; 5,583,485; 5,614,885; 5,614,891; 5,619,190; 5,627,529; 5,646,701; 5,661,651; 5,661,804; 5,686,903; 5,699,054; 5,699,055; and 5,708,415, as well as in U.S. Pat. Nos. 5,903,22 and 5,854,593, all of which are commonly assigned to Prince Corporation.
A block diagram representing a typical RF trainable transmitter is shown in FIG.
1
. As described in more detail below, the RF trainable transmitter includes a signal generator
10
for generating the signals to be transmitted and for generating a reference signal used during the training process to identify the RF carrier frequency and to demodulate the received signal. Signal generator
10
operates under control of a microprocessor
16
, which selects the carrier frequency of the signal generated by signal generator
10
by applying a signal frequency control signal to input terminal b of signal generator
10
. Microprocessor
16
may also cause signal generator
10
to modulate the generated signal in accordance with a DATA signal applied to input terminal a of signal generator
10
. When transmitting a modulated signal, signal generator
10
outputs the modulated signal to a transmit amplifier
27
through output terminal d. The modulated signal is thus amplified and passed to an antenna
2
that transmits the RF signal as signal B to a remotely controlled apparatus
6
.
When the trainable transmitter is receiving a signal A from an original remote control transmitter
4
during the training mode, the received signal is fed from antenna
2
to an input of a mixer
8
. A reference signal output from terminal c of signal generator
10
is supplied to a second input of mixer
8
. Mixer
8
mixes the reference signal and the received signal A to generate a mixed output signal. The mixed output signal passes through a bandpass filter
12
and a processing circuit
14
to an input of a microprocessor
16
where it is further processed.
The RF trainable transmitter also includes user input switches
18
coupled to microprocessor
16
through a switch interface circuit
20
, to allow the user to initiate either training of a signal or transmission of a signal. Additionally, one or more light emitting diodes (LEDs)
22
or some other display or indicator circuit may be coupled to an output of microprocessor
16
to provide feedback information to the user. The RF trainable transmitter also includes a power supply circuit
24
that may be permanently or detachably coupled to the battery of a vehicle.
The RF trainable transmitter shown in
FIG. 1
typically operates in either a training mode or a transmit mode. To cause the trainable transmitter to enter the training mode, a user presses one of switches
18
. Upon detecting that a switch
18
has been depressed for a predetermined time period, microprocessor
16
enters the training mode. During the training mode, the user activates original remote control transmitter
4
associated with a garage door opening mechanism (e.g., remotely controlled apparatus
6
) to cause original remote control transmitter
4
to transmit the signal to be learned (A). While signal A is transmitted, microprocessor
16
first identifies the carrier frequency of signal A.
To identify the RF carrier frequency of the received signal, microprocessor
16
generates and supplies a frequency control signal (FREQ) to input terminal b of signal generator
10
. Signal generator
10
responds to the frequency control signal by generating an unmodulated RF reference signal having a frequency dictated by the frequency control signal received from microprocessor
16
. Antenna
2
supplies the RF reference signal to mixer
8
, which mixes the reference signal with the received signal A. Mixer
8
outputs a signal including the data code encoded in the received RF signal and having a carrier frequency that is equal to the difference between the carrier frequencies of the received RF signal and the RF reference signal. Narrow bandpass filter
12
is provided to pass a signal only when the carrier frequency of the signal from mixer
8
is 10.7 MHz. The output of bandpass filter
12
is passed through a processing circuit
14
back to microprocessor
16
. In this manner, microprocessor
16
can selectively vary the carrier frequency of the RF reference signal output from signal generator
10
until a signal is detected from processing circuit
14
. When a signal is detected from processing circuit
14
, microprocessor
16
will know that the carrier frequency of the received RF signal is 3 MHz different from the known carrier frequency of the RF reference signal. Once microprocessor
16
identifies and verifies the carrier frequency, it stores the value of the frequency control signal in its internal memory and digitizes and stores the data code that is demodulated by processing circuit
14
.
Subsequently, when a user wishes to cause the trainable transmitter to transmit a signal (B) to the garage door opening mechanism
6
, the user presses the associated switch
18
to instruct microprocessor
16
to begin transmitting the RF signal. Microprocessor
16
responds by reading the frequency data from its memory and providing a corresponding frequency control signal to signal generator
10
, while also reading from its memory the data code at the same rate at which it was recorded and supplying this data signal (DATA) to input terminal a of signal generator
10
. Signal generator
10
then generates a carrier signal having the selected frequency and modulates the amplitude of the signal with the data signal supplied from microprocessor
16
. This modulated RF signal (B) is output through antenna
2
to the remotely controlled garage door opening mechanism
6
. It should be noted that a plurality of switches
18
is provided to enable a plurality of signals to be learned and subsequently transmitted.
An early version of an RF trainable transmitter is disclosed in U.S. Pat. No. 5,614,885. In this version, signal generator
10
was generally constructed as shown in FIG.
2
. Specifically, signal generator
10
employed a voltage controlled oscillator (VCO)
110
, which generates a sinusoidal signal having a frequency dictated by the analog voltage level applied at its voltage control input terminal. To allow microprocessor
16
to control the voltage level applied to the voltage control input of VCO
110
using a digital value that may easily be stored in its m
Foley & Lardner
Johnson Controls Technology Company
Zimmerman Brian
LandOfFree
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