Receiver

Details Receiver Receiver

2002-04-08

2004-08-03

Chin, Vivian (Department: 2682)

Telecommunications

Receiver or analog modulated signal frequency converter

Frequency conversion between signal source and receiver

C455S142000

Reexamination Certificate

active

06771942

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) In an aspect, this invention relates to a receiver and, more particularly, to a receiver applicable to an automobile audio tuner system.
The trend of electronization of automobiles seems to be practically limitless. In recent years, a so-called keyless entry system has become popular to allow the automobile driver to remotely lock and unlock the door of the automobile.
FIG. 1
of the accompanying drawing is a schematic block diagram of the tuner section of a known keyless entry system.
Referring to
FIG. 1
, tuner
100
comprises an RF (radio frequency) amplifier
102
and a keyless signal generating circuit
103
, wherein a signal wave is emitted from the door key as a switch arranged at the door key
104
is depressed. The signal wave is then entered to the RF amplifier
102
by way of an antenna
101
arranged near the transmission system or the fender of the car. The signal wave is then amplified by the RF amplifier
102
for high frequency amplification. The keyless signal generating circuit
103
generates a keyless signal according to the output signal of the RF amplifier
102
.
The keyless signal is then entered to microcomputer
105
of the keyless entry system. Upon receiving the keyless signal, the microcomputer
105
controls the door lock for locking and unlocking the door. More specifically, the microcomputer
105
recognizes the status of door lock mechanism
106
of the automobile so that it unlocks the door when it receives a keyless signal while the door is held in a locked state by the door lock, whereas it locks the door when it receives a keyless signal while the door is held in an unlocked state by the door lock.
The tuner of a keyless entry system is either of an FM tuner system that utilizes FM signals or of an AM tuner system that utilizes AM signals.
Referring to
FIG. 2
of the accompanying drawing, the keyless signal generating circuit
103
of an FM tuner system typically comprises a converter
103
3
for frequency conversion including a mixer
103
1
and an oscillator circuit (OSC)
103
2
, an IF (intermediate frequency) limiter amplifier
103
4
and an FM detector circuit
103
5
.
Referring to
FIG. 3
of the accompanying drawings, the keyless signal generating circuit
103
of an AM tuner system, on the other hand, typically comprises a converter
103
8
for frequency conversion including a mixer
103
6
and an oscillator circuit (OSC)
103
7
, an IF amplifier provided with an AGC (automatic gain control) function and an AM detector circuit
103
10
.
Meanwhile, an automobile is provided with an mobile radio receiving set as a standard or optional equipment. Such a mobile radio receiving set comprises an FM (frequency modulation) tuner and an AM (amplitude modulation) tuner.
FIG. 4
of the accompanying drawing is a schematic block diagram of the FM/AM tuner section of a mobile radio receiving set.
Referring to
FIG. 4
, the tuner
200
comprises an RF antenna for FM broadcast, a regenerative circuit
203
for FM broadcast and a stereophonic demodulation circuit
204
.
The FM tuner section of the tuner
200
includes an RF amplifier
202
for FM broadcast, a regenerative circuit
203
for FM broadcast and a stereophonic demodulation circuit
204
. An FM wave is fed to the RF amplifier
202
for FM broadcast by way of the antenna
201
. Then, the FM wave is amplified for high frequency amplification. The regenerative circuit
203
for FM broadcast generates an FM composite signal on the basis of the output signal of the RF amplifier
202
for FM broadcast. The stereophonic demodulation circuit
204
generates a left/right signal for FM broadcast on the basis of the FM composite signal.
Referring to
FIG. 5
of the accompanying drawing, the regenerative circuit
203
for FM broadcast typically comprises a converter
203
3
for frequency conversion including a mixer
203
1
a VCO
203
2
for FM broadcast, an IF limiter amplifier
203
4
and an FM detector circuit
203
5
.
The stereophonic demodulation circuit
204
typically includes a pulse noise reduction circuit and a stereophonic decoder.
The AM tuner section of the tuner
200
, on the other hand, includes an RF amplifier
205
for AM broadcast and a regenerative circuit
206
for AM broadcast. An AM wave is fed to the RF amplifier
205
for AM broadcast by way of the antenna
201
. Then, the AM wave is amplified by the RF amplifier
205
for AM broadcast. The regenerative circuit
206
for AM broadcast generates an AM radio signal on the basis of the output signal of the RF amplifier
205
for AM broadcast.
As shown in
FIG. 6
of the accompanying drawing, the regenerative circuit
106
for AM broadcast typically comprises a converter
203
8
for frequency conversion including a mixer
203
6
and a VCO
203
7
for AM broadcast, an IF amplifier
203
9
having an AGC (automatic gain control) function and an AM detector circuit
203
10
.
As seen from the above description, the known keyless entry system and the automobile audio system have respective histories of technological development. One of the reasons for this may be that the reception frequency (about 300 MHz to 430 MHz) of the tuner of any known keyless entry system is higher than those of the MW band and the VHF band used for the FM/AM tuner of any existing automobile audio system. Therefore, the tuner section of the keyless entry system and the FM/AM tuner section of the automobile audio system have respective configurations that are different from each other in an automobile.
However, referring to
FIG. 7
of the accompanying drawings, the signal wave is typically used digitally to express the existence of a signal (“1”) and the nonexistence of a signal (“0”) in an AM tuner type keyless entry system for both transmission and reception. If such is the case, the tuner section may not need an AGC function because the tuner section can process the received signal wave without distortion.
Therefore, the IF amplifier of an AM tuner type keyless entry system may be replaced by a limiter amplifier that is normally used in an FM tuner type keyless entry system.
Additionally, a keyless entry system comprises and an automobile audio system have components that are common in both of them.
Thus, it is an object of the present invention to provide a tuner section that can be used commonly for a keyless entry system and an automobile audio system in order to reduce the number of components in an automobile equipped with a keyless entry system and hence the manufacturing cost such a keyless entry system.
(2) In another aspect, the present invention relates to a crystal oscillator and, more particularly, it relates to a crystal oscillator to be suitably used for generating a master clock for the tuner and the station selecting PLL (phase locked loop) circuit of a radio or a television receiver.
FIG. 8
of the accompanying drawing is a schematic block diagram of a principal part of a known radio receiver.
The radio receiver comprises an FM tuner, an AM tuner and a PLL circuit.
The FM tuner includes an RF (radio frequency) amplifier
11
, a mixer
12
and a band-pass filter
13
.
The high frequency signal caught by the antenna
10
of the radio receiver is fed to the RF amplifier
11
and amplified. The output of the RF amplifier
11
is sent to the mixer
12
and the PLL circuit
31
to select a station. The output of the mixer
12
is turned into an IF (intermediate frequency) signal as it passes through the band-pass filter
13
.
The AM tuner includes an RF amplifier
21
, mixers
22
a
and
22
b
, band-pass filters
23
a
and
23
b
and a crystal oscillator
24
.
The high frequency signal received by the antenna
10
is sent to the RF amplifier
21
and amplified. The output of the RF amplifier
21
is sent to the mixer
22
a
to select a station. The output of the mixer
22
a
is sent to the mixer
22
b
by way of the PLL circuit
23
a
and subjected to frequency conversion in the mixer
22
b
. The mixer
22
b
is fed with the clock generated by the crystal oscillator
24
. The output of the mixer
22
b
is turned int

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