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Mobile Phone Patent Abstract
A mobile phone hand-free extension device includes a FM radio transmitter
with an active frequency searching circuitry to utilize a vehicular
FM radio receiver for reproducing the audio signals from the mobile
phone. The active frequency searching circuitry in this invention
automatically detects which frequency band the vehicular FM radio
receiver is currently using and set the RF frequency of the FM transmitter
to the detected frequency. The FM transmitter relays the audio signals
from the mobile phone by transmitting the audio signals through
radio wave to the vehicular FM radio receiver to be reproduced by
the speaker of the receiver.
Mobile Phone Patent Claims
What is claimed is:
1. A method to determine the channel frequency setting of an FM
radio receiver, comprising: generating an electrical signal with
a particular pattern; modulating an FM carrier at a frequency within
a commercial FM band with said electrical signal; transmitting said
modulated FM carrier to said FM radio receiver; receiving an audio
signal reproduced by said FM radio receiver and detecting said particular
pattern; determining if the frequency of said FM carrier matches
that of said FM radio frequency receiver by the successful detection
of said particular pattern; and changing the frequency of said FM
carrier and repeating above steps until the frequency of said FM
carrier matches that of said FM radio receiver.
2. A mobile phone hand-free extension device, comprising: a frequency-searching
unit for generating and outputting an electrical signal with a particular
pattern, detecting said particular pattern from an input signal,
and outputting a DC voltage; an FM transmitter using said electrical
signal with a particular pattern to modulate an FM carrier, broadcasting
said FM carrier, and using said DC voltage to control a voltage-controlled-oscillator
inside said FM transmitter; a first microphone for picking up an
audio signal in an environment; a second microphone for picking
up a voice signal from the mobile phone; and a switch for connecting
a signal path either from said second microphone to said FM transmitter
or from said frequency-searching unit to said FM transmitter.
3. The mobile phone hand-free extension device as claimed in claim
2, further comprising an audio coupling device that surrounds said
second microphone and connects to a speaker of the mobile phone
to form an audio channel and to block the sounds in the environment.
4. The mobile phone hand-free extension device as claimed in claim
2, further comprising an audio amplifier coupled to the outputs
of said first microphone and said second microphone.
5. The mobile phone hand-free extension device as claimed in claim
2, further comprising an audio amplifier coupled to an output of
said first microphone or said second microphone.
6. The mobile phone hand-free extension device as claimed in claim
2, further comprising a RF signal detector that activates said frequency-searching
unit when it detects a RF signal at a specified frequency band.
7. The mobile phone hand-free extension device as claimed in claim
6, wherein said RF signal detector detects the RF signal at the
frequency within the range allocated for use of mobile phones.
8. The mobile phone hand-free extension device as claimed in claim
2, further comprising a call activity detector to detect call activities
of the mobile phone, said call activity detector activating said
frequency-searching unit.
9. The mobile phone hand-free extension device as claimed in claim
2, said frequency-searching unit comprising a microprocessor-based
microcontroller and a digital-to-analog converter that outputs said
DC voltage to control said voltage-controlled oscillator inside
said FM transmitter.
10. The mobile phone hand-free extension device as claimed in claim
2, said frequency-searching unit comprising a comparator circuitry
coupled to a microprocessor-based microcontroller and a digital-to-analog
converter that outputs said DC voltage to control said voltage-controlled
oscillator inside said FM transmitter, said comparator circuitry
comparing said input signal to a reference signal with said particular
pattern and outputting a signal to said microcontroller.
11. A mobile phone hand-free extension device, comprising: a frequency-searching
unit generating and outputting an electrical signal with a particular
pattern, detecting said particular pattern from an input signal,
and outputting a DC voltage; an FM transmitter using said electrical
signal with said particular pattern to modulate an FM carrier, transmitting
said FM carrier, and using said DC voltage to control a voltage-controlled-oscillator
inside said FM transmitter; a first microphone picking up an audio
signal in an environment; a switch connecting a signal path either
from an audio output of the mobile phone to said FM transmitter
or from said frequency-searching unit to said FM transmitter; and
a call activity detector detecting call activities of the mobile
phone, and said call activity detector activating said frequency-searching
unit.
12. The mobile phone hand-free extension device as claimed in claim
11, wherein said hand free extension device is encased within the
casing of the mobile phone.
13. The mobile phone hand-free extension device as claimed in claim
11, said frequency-searching unit comprising a microprocessor-based
microcontroller and a digital-to-analog converter that outputs said
DC voltage to control said voltage-controlled oscillator inside
said FM transmitter.
14. The mobile phone hand-free extension device as claimed in claim
11, said frequency-searching unit comprising a comparator circuitry
coupled to a microprocessor-based microcontroller and a digital-to-analog
converter that outputs said DC voltage to control said voltage-controlled
oscillator inside said FM transmitter, said comparator circuitry
comparing said input signal to a reference signal with said particular
pattern and outputting a signal to said microcontroller.
15. The mobile phone hand-free extension device as claimed in claim
11, said frequency-searching unit further comprising: a signal generator
circuitry, outputting said electrical signal with said particular
pattern; a comparator circuitry coupled to a microprocessor-based
microcontroller, said comparator circuitry comparing said input
signal with said electrical signal using said particular pattern,
and outputting a signal to said microcontroller; and a digital-to-analog
converter, outputting said DC voltage to control said voltage-controlled
oscillator inside said FM transmitter.
Mobile Phone Patent Description
FIELD OF THE INVENTION
The present invention relates generally to a mobile phone hand-free
extension device that utilizes the vehicular radio receiver to provide
audio signals to the mobile phone user, and more specifically to
a mobile phone hand-free extension device with a radio frequency
(RF) transmitter and a frequency searching circuitry to automatically
relay the audio signal received from the mobile phone to the vehicular
radio receiver.
BACKGROUND OF THE INVENTION
The technology of mobile phones has made possible mobile voice
communication for millions of people. Mobile phones are carried
and used daily by hundreds of millions of people and become an ordinary
household items worldwide. The mobile phone user quite often makes
the phone call while driving an automobile and therefore creates
a potential hazardous driving condition since the driver has to
hold the mobile phone and drive at the same time.
A hand-free kit is an external accessory to the mobile phone and
its purpose is to free the driver from distraction of holding and
using the mobile phone. Several technologies have been pursued to
enable the driver to use the mobile phone without holding the cellular
phone.
U.S. Pat. No. 6,134,456 discloses a control switch box with cables
linking the mobile phones and the vehicular stereo system. However,
installating such kind of accessory is quite involved and requires
wiring and routing inside the automobile body.
The U.S. Pat. No. 5,867,794 discloses another method that uses
an FM transmitter to send the audio signal from the mobile phone
to the vehicular FM radio. In the disclosure, there is no need to
physically connect the mobile phone and the vehicular audio system.
However, the disadvantage of this approach is that the frequency
of the FM transmitter has to be set to the same channel as the FM
radio receiver that the driver is currently listening to whenever
he wants to use the hand-free kit. The frequency of either the FM
transmitter or the FM radio receiver has to be adjusted and it causes
much inconvenience in application.
It will be an innovative approach to include an apparatus or a
method to detect radio frequency of the FM radio receiver and to
set the frequency of the FM transmitter automatically.
SUMMARY OF THE INVENTION
This invention has been made to overcome the drawbacks of the conventional
mobile phone hand-free kit. The primary object is to provide to
a mobile phone hand-free extension device. The mobile phone hand-free
extension device utilizes the vehicular radio receiver to provide
audio signals to the mobile phone user. It includes a radio frequency
(RF) transmitter and a frequency searching circuitry to automatically
relay the audio signal received from the mobile phone to the vehicular
radio receiver.
The mobile phone hand-free extension device comprises a RF signal
detector, a frequency searching circuitry and an FM transmitter.
The RF signal detector detects the radio frequency communication
between the mobile phone and the base station. Whenever a call activity
between the mobile phone and the base station is detected by the
RF signal detector, the RF signal detector activates the frequency
searching circuitry to find the frequency of the FM radio receiver
if the mobile phone user is listening to the FM radio. As soon as
the frequency is located, the FM transmitter sends a radio wave
modulated by the audio signal of the mobile phone to the FM radio
receiver. On receiving the radio wave, the FM radio receiver demodulates
the radio wave to retrieve the original audio signal, which is further
reproduced by the speaker of the FM radio receiver. The car-driving
mobile phone user therefore has no need to hold the mobile phone
close to his ear since the voice and sound coming out of the mobile
phone is relayed to an external speaker by this invention.
Another object of the present invention is to provide a method
to detect the radio frequency being tuned by a vehicular FM radio
receiver and to relay the audio signal from a mobile phone to the
vehicular FM radio receiver using a radio wave at the frequency
detected.
The foregoing and other objects, features, aspects and advantages
of the present invention will become better understood from a careful
reading of a detailed description provided herein below with appropriate
reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a general schematic diagram showing the audio output
extension for a mobile phone hand-free operation according to the
present invention.
FIG. 2 shows a flow chart for automatically searching the frequency
of an FM radio receiver according to the present invention.
FIG. 3 shows a preferred embodiment of a mobile phone hand-free
extension device using a microprocessor and a digital-to-analog
converter to realize the frequency-searching unit according to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a general schematic diagram showing the audio output
extension device for a mobile phone hand-free operation according
to the present invention. Referring to FIG. 1, the mobile phone
hand-free extension device comprises a microphone 11, an active
frequency-searching unit 12, an FM transmitter 13, a switch 14 and
a second microphone 15.
The following describes in detail how the frequency-searching unit
detects the radio frequency of the FM radio receiver and sets the
frequency of the FM transmitter automatically.
The active frequency-searching unit 12 controls the radio frequency
of the voltage-controlled oscillator (VCO) inside the FM transmitter
13 and sends a signal with a particular pattern at the audio frequency
to modulate the RF carrier of the FM transmitter. The signal sent
with a particular pattern can be either a digital signal or an analog
signal. The radio frequency of the FM transmitter is controlled
in such a way that it starts from the lower band edge of the commercial
FM band such as 88-108 MHz and increases repeatedly by a predetermined
frequency step to the upper band edge. The preferred predetermined
frequency step can be the allocated channel bandwidth of an FM station.
At each frequency point, the FM transmitter will send out the modulated
RF carrier. If the frequency of the FM transmitter matches that
of the FM radio receiver 16, the signal with a particular pattern
at the audio frequency will be demodulated, retrieved and broadcasted
from the speaker 17 that is connected to the FM radio receiver.
The microphone 11 picks up the audio signal from the speaker and
sends it to the active frequency search unit to determine if this
audio signal is the same as the particular signal that the FM transmitter
originally sent out.
FIG. 2 shows a flow chart for automatically searching the frequency
of an FM radio receiver according to the present invention. As shown
in FIG. 2, the frequency stepping process, the signal emitting process,
and the signal comparing process are repeated over and over again
until the original signal sent out by the frequency-searching unit
is received by it again. When this condition is met, the RF frequency
of the FM transmitter is locked on to that of the FM radio receiver.
After the RF frequency of the FM transmitter is set to that of
the FM radio receiver, the switch 14 disconnects the audio signal
generated by the frequency-searching unit 12 and connects the audio
signal picked up by the second microphone 15 to the FM transmitter.
The second microphone is placed close to the internal speaker of
the mobile phone 18 to pick up the audio signal generated by the
voice of the other party on the line. As a result, the audio signal
is relayed to the FM radio receiver 16 and the voice is reproduced
by the speaker 17.
FIG. 3 shows a preferred embodiment of a mobile phone hand-free
extension device using a microprocessor and a digital-to-analog
converter to realize the frequency-searching unit according to the
present invention. Referring to FIG. 3, the frequency-searching
unit is realized by a microprocessor-based microcontroller 21 and
a digital-to-analog converter (DAC) circuitry 22. This embodiment
further includes a RF signal detector 23.
When the RF signal detector detects the signal exchange between
the mobile phone 32 and the base station, it sends a signal into
one of the I/O port of the microcontroller 21 to activate the frequency
searching sequence.
The frequency searching sequence works as follows: the microcontroller
uses a plurality of I/O ports to send a parallel digital data to
the DAC 22. The number of I/O ports used corresponds to the number
of bits of the digital data. The DAC converts the digital data to
a corresponding analog DC voltage value. The DC voltage is used
to control the oscillating frequency of the voltage-controlled oscillator
inside the FM transmitter 24 and as a result the RF frequency of
the FM transmitter is controlled by the microcontroller. The DAC
is configured such that the minimum analog DC voltage converted
from the digital data corresponds to the lower band edge of the
commercial FM bands and the maximum analog DC voltage converted
from the digital data corresponds to the upper band edge of the
commercial FM bands. The microcontroller can increase or decrease
the RF frequency of the FM transmitter by a minimum frequency step
that is determined by the number of bits used for a digital data.
For example, if 10 bits are used for a digital data, the step frequency
will be (108-88) MHz divided by 2.sup.10, i.e. 19.5 KHz. The microcontroller
increases the RF frequency of the FM transmitter from the lower
band edge to the upper band edge or in a reverse way decreases the
frequency from upper band edge to the lower band edge repeatedly
by a frequency step in a programmable way to cover the whole commercial
FM frequency band.
At each frequency point, the microcontroller sends a beacon signal
at audio frequency with a particular pattern from one of its I/O
ports to the FM transmitter through the switch 25. The pattern of
the beacon signal is chosen to be different from any other possible
audio signal, such as a voice signal or a noise signal from the
automobile in the environment. The RF carrier modulated by the beacon
signal is transmitted by the FM transmitter at the RF frequency
set by the microcontroller. If the FM radio receiver 30 is working
at the same RF frequency, the RF radio receiver 30 will receive
and demodulate the beacon signal, which is further broadcasted by
the speaker 31.
The microphone 26 picks up the beacon signal and sends it to the
signal comparator 27 to determine if the received signal has the
same pattern as the original beacon signal. If the signal patterns
is matched, it represents a frequency locking condition, i.e. the
FM transmitter and the FM radio receiver are both working at the
same RF frequency channel. The switch 25 disconnects the signal
path between the microcontroller and the FM transmitter, and establishes
the signal path among the microphone 28, the amplifier 29 and the
FM transmitter 24. The signal comparator 27 can be incorporated
in the microcontroller 21 and implemented as a software sequence
stored in the memory of the microcontroller.
Therefore, the mobile phone hand-free extension device of the invention
has been made to overcome the drawbacks of the conventional hand-free
extension device. Its advantages include that there is no need to
physically connect the mobile phone and the vehicular audio system
and it can detect radio frequency of the FM radio receiver and to
set the frequency of the FM transmitter automatically.
Although the present invention has been described with reference
to the preferred embodiments, it will be understood that the invention
is not limited to the details described thereof. Various substitutions
and modifications have been suggested in the foregoing description,
and others will occur to those of ordinary skill in the art. Therefore,
all such substitutions and modifications are intended to be embraced
within the scope of the invention as defined in the appended claims.
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