Telecommunications – Receiver or analog modulated signal frequency converter – Remote control of receiver
Reexamination Certificate
1999-11-29
2004-07-06
Maung, Nay (Department: 2684)
Telecommunications
Receiver or analog modulated signal frequency converter
Remote control of receiver
C455S345000, C340S005720, C340S005610, C340S005640, C340S870030
Reexamination Certificate
active
06760579
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile receiver wherein an antenna and part of a receiving circuit is used for a keyless entry system or the like for remotely controlling the lock/unlock of vehicle doors, trunk and the like are also used as those of a mobile radio receiver, and to an antenna device wherein an antenna is used both for receiving remote control signals for remotely controlling a drive mounted on a vehicle and for receiving radio broadcast waves.
2. Description of the Relevant Art
Hitherto, the keyless entry system whereby the lock/unlock of vehicle doors and the like is remotely controlled has a construction entirely separate from a mobile radio receiver. Therefore, an antenna and receiving circuits for keyless entry system are mounted on a vehicle without finding sufficient space for the placement thereof, resulting in complication of the placement construction thereof and a high cost.
In order to solve the above problems, a system was proposed, wherein an antenna and part of a receiving circuit for a keyless entry system also serves as those of a mobile radio receiver so as to make the construction of the automobile equipment control system more compact and reduce the placement space thereof (Japanese Utility Model Publication No. 06-67748).
FIG. 1
is a block diagram schematically showing the principal part of a radio receiver. In the figure, reference numeral
11
represents an antenna for a radio receiver, and a high frequency signal input to the antenna
11
is amplified in a high frequency amplifier circuit
12
. The amplified signal and a local oscillation signal from a local oscillator circuit
14
B are mixed in a mixing circuit
13
B, and are taken as an intermediate frequency signal. The intermediate frequency signal from the mixing circuit
13
B is amplified in an intermediate frequency amplifier circuit
19
B. The amplified signal is detected in a detector circuit
20
, and then, is amplified in a low frequency amplifier circuit
21
. It is output as a voice through a speaker
22
. A PLL circuit
15
B performs the phase lock of the oscillation signal from the local oscillator circuit
14
B under the control of a CPU
16
B, so as to stabilize the intermediate frequency output signal from the mixing circuit
13
B.
FIG. 2
is a block diagram schematically showing the principal part of a conventional mobile receiver disclosed in the above publication. In the figure, reference numeral
31
represents a frequency switching means to switch between an oscillation signal sent out from a local oscillator circuit
14
c
for radio and that for keyless entry system. The frequency switching means comprises a PLL circuit
15
c
and a CPU
16
c.
A mixing circuit
13
c
is connected through a change-over switch
17
which is switched depending on the operating positions of an ignition switch
18
to an intermediate frequency amplifier circuit
23
for keyless entry system. The output from the intermediate frequency amplifier circuit
23
is input through a detector circuit
24
to a controller
25
, which controls a motor
26
or the like, being a door lock/unlock drive, in response to the output from the detector circuit
24
.
The voltage of a battery
27
mounted on a vehicle is constantly applied to a keyless circuit
28
which is enclosed with the dotted lines, while it is selectively supplied to an ACC (accessory) contact
18
a
, an ignition contact
18
b
and a start contact
18
c
depending on the operating positions of the ignition switch
18
. The keyless side becomes capable of operation when the ignition switch
18
is in an off contact (OFF), while the radio side becomes capable of operation when the ignition switch
18
is in the ACC contact
18
a.
FIG. 3
is a block diagram schematically showing the principal part of a conventional receiver for keyless entry system. A battery
27
is connected through a power line
8
for supplying electric power to each receiving circuit (high frequency amplifier circuit
2
, mixing circuit
3
B, local oscillator circuit
4
B, intermediate frequency amplifier circuit
5
B, detector circuit
6
and signal processing circuit
7
). A switch
9
which is intermittently make-and-break controlled by a CPU
10
is interposed in the power line
8
, so that electric power is intermittently supplied to each receiving circuit (e.g. electric power is supplied thereto for 10 msec every 100 msec), resulting in a controlled power consumption.
FIG. 4
is a timing chart showing an example of the relationship between the timing of the output of on/off control signals from the CPU
10
and that of the power supply to each receiving circuit.
Since the receiving frequencies of a radio receiver are 100 MHz and less, the PLL circuit
15
B only for radio receiver shown in
FIG. 1
is only required to lock phases within that range.
On the other hand, the receiving frequency band in the keyless entry system is usually 300-400 MHz, which is 3-4 times higher than the receiving frequencies of the radio receiver. Therefore, the PLL circuit
15
C in the mobile radio and keyless entry system receiver shown in
FIG. 2
must be able to lock phases covering a wider range than that only for radio broadcasting, resulting in a higher cost and difficulty in tuning.
When the ignition switch
18
is in the off contact (the engine is not running), or when it is originally desired that the power consumption should be kept as low as possible, the mobile radio and keyless entry system receiver must keep being supplied with electric power.
Since the mode changes between the radio receiving mode and the keyless receiving mode depending on the operating positions of the ignition switch
18
, the keyless signals cannot be received during the radio receiving mode.
Hitherto, the keyless entry system whereby a drive mounted on a vehicle, for example, a drive to perform the lock/unlock of doors and the like is remotely controlled and has a construction entirely separate from a car radio. Therefore, antenna and receiving circuits for keyless entry systems are often mounted on a vehicle without finding sufficient space for the placement thereof, resulting in the complication of the placement construction thereof and a high cost.
In order to solve the above problems, a system was proposed, wherein an antenna and part of the receiving circuits for a car radio receiver are also used as those for keyless entry system so as to make the construction of the automobile equipment control system more compact and to reduce the placement space thereof.
As an antenna for a car radio receiver, a pole antenna having a form of a metal pole projected from the body shell is exemplified. The antenna length of the pole antenna is set to approximately 100 cm, which is not sufficient considering the wavelength of AM broadcast waves, but is suitable for receiving FM broadcast waves. As the construction of the pole antenna, there are pole antennas which can be stowed away into the vehicle body and those which cannot be stowed therein. In the stowage-type pole antennas, some are stowed by manual system, and others are stowed by electromotive systems, which may include a long and slender telescopic pipe which comprises several segmented portions is caused to vertically move. antennas which can be stowed away into the vehicle body and those which cannot be stowed therein. In the stowage-type pole antennas, some are stowed by manual system, and others are stowed by electromotive systems. A long and slander telescopic pipe which is several-sigmented is caused to vertically move.
By stowing the antenna away into the vehicle body when it is not needed, the antenna can be protected from damage caused by touching an obstacle, mischief of the wrong-minded, and the like. Especially when the antenna is left long in the stop state of the vehicle, the risk of suffering mischief is high. Therefore, it is extremely effective to keep the antenna inside the body during the vehicle stop.
However, when a pole antenna is used both for the keyless entry system
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