Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
2000-06-12
2003-09-23
Chin, Vivian (Department: 2682)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S226200, C455S207000, C455S313000, C455S314000, C455S423000, C375S316000
Reexamination Certificate
active
06625468
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a digital portable telephone unit suited to play back excellent voice/sound and a method for playing back voice/sound in the digital portable telephone unit.
BACKGROUND OF THE INVENTION
In order to play back excellent voice/sound in digital portable telephone units, it is necessary to measure precisely RSSI (receive signal strength indicator) to each symbol point.
FIG. 1
shows an example of conventional digital portable telephone unit trying such a RSSI measurement.
As shown in
FIG.1
, receive signal received by an antenna
101
is selected at a desired receive frequency, frequency-converted and amplified by a radio section
102
. Then, IF (intermediate frequency)
127
and RSSI (receive signal strength indicator) are output from the radio section
102
to a demodulation section
103
.
IF
127
output to the demodulation section
103
is demodulated and then output, as receive data, to an A/D converter
114
. The A/D converter
114
digitalizes RSSI voltage of RSSI
127
a
and then outputs it.
Concurrently, a control section
109
processes the receive data and outputs voice/sound signal. Also, the control section
109
uses the digitalized RSSI
127
a
for the control of phone-call connection. Voice/sound signal processed by the control section
109
is then converted into analogue signal by an audio processing section
106
, and then is output from a receiver
113
.
On the other hand, voice/sound input from a microphone
112
is converted into digital signal by the audio processing section
106
. The control section
109
conducts the processing to process the voice/sound digital signal into transmit data. After that processing, the transmit data signal is modulated by the radio section
102
, into carrier wave with a normal frequency. Then, the carrier-wave signal with the normal frequency is amplified by the radio section
102
, and then is transmitted through the antenna
101
.
Meanwhile, an operation section
110
controls the user interface to send contents of instruction such as a phone number etc. from the user to the control section
109
. Also, a display section
111
displays various information such as a received phone number etc. A CLK section
105
generates a clock for timing processing, time display etc. A reference oscillator
108
generates a reference frequency used in generating frequency at the radio section
102
and a precise frequency used in the control section
109
and the demodulation section
103
.
An AFC (automatic frequency control) section
104
controls the reference oscillator
108
to coincide with a precise received frequency of base station.
FIG.2
shows the detailed composition of the demodulation section
103
.
In digital portable telephone units, &pgr;/4 shift DQPSK is used as modulation system. In modulation, delay detection system is used.
Thus, IF
127
from the radio section
102
is output as phase DATA
129
at a timing of symbol CLK
132
by a phase detection section
121
which operates using a reference frequency of 14.4 MHz
128
as a clock.
A DATA playback section
122
produces demodulated data
133
from the phase DATA
129
and outputs it. Also, a phase correction section
123
makes a phase correction based on the phase DATA
129
, and outputs a phase-corrected IF
127
to be used at the AFC section
104
as corrected output
130
.
A demodulation CLK section
125
outputs a demodulation CLK of 2.68 MHz
134
to a CLK regenerative section
124
. Here, between the demodulation CLK section
125
and the CLK regenerative-section
124
is composed as a PLL (phase-locked loop) circuit.
The CLK regenerative section
124
outputs symbol CLK
132
(21 kHz) obtained dividing 2.68 MHz demodulation CLK
134
by
128
and DATA CLK (42 kHz)
131
obtained dividing it by 64.
Also, the phase timings of symbol CLK
132
and DATA CLK
131
are adjusted according to the difference in the amount of phase shift between first-half and second-half symbol sections of phase DATA
129
, so that they are made to coincide with the symbol timing of IF signal
127
.
Meanwhile, as a system to decode encoded audio data more excellently, a method of incorporating RSSI as a factor of decoding operation is known.
In this case, it is necessary to measure precisely RSSI to each symbol point of receive signal digital-modulated.
Here, the &pgr;/4 shift DQPSK is characterized in that the signal level at each symbol point becomes constant, however, between symbol points, the signal level varies depending on data values modulated.
So, in order to measure precisely RSSI to each symbol point, it is important to measure the signal level at a precise timing of symbol point.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a digital portable telephone unit that offers an excellent playback of voice/sound by measuring signal level precisely at a timing of symbol point.
It is a further object of the invention to provide a method for playing back voice/sound that offers an excellent-playback of voice/sound by measuring signal level precisely at a timing of symbol point.
According to the invention, a digital portable telephone unit, comprises:
an antenna through which signal is transmitted and received;
a radio section which conducts the frequency conversion of signal and outputs IF (intermediate frequency) and RSSI (receive signal strength indicator);
a demodulation section which demodulates the IF to output receive data;
an A/D converter which outputs digitalizing the voltage of RSSI; and
a control section which receives the receive data and outputs audio signal;
wherein the demodulation section outputs a trigger to indicate a symbol point of RSSI to the A/D converter.
According to another aspect of the invention, a method for playing back voice/sound, comprises:
first step of conducting the transmission/reception of signal;
second step of conducting the frequency conversion of signal and outputting IF (intermediate frequency) and RSSI (receive signal strength indicator);
third step of demodulating the IF to output receive data;
fourth step of outputting digitalizing the voltage of RSSI;
fifth step of processing the receive data to output audio signal; and
sixth step of outputting a trigger to indicate a symbol point when digitalizing the voltage of RSSI.
REFERENCES:
patent: 5461646 (1995-10-01), Anvari
patent: 5617451 (1997-04-01), Mimura et al.
patent: 5875388 (1999-02-01), Daughtry, Jr. et al.
patent: 6-54009 (1994-02-01), None
patent: 6-54012 (1994-02-01), None
patent: 6-140971 (1994-05-01), None
patent: 6-164663 (1994-06-01), None
patent: 7-322354 (1995-12-01), None
patent: 7-336404 (1995-12-01), None
patent: WO95/18486 (1995-07-01), None
Chin Vivian
NEC Corporation
Scully Scott Murphy & Presser
Yun Eugene
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