Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
2000-11-03
2004-03-30
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S552100, C455S553100, C455S414400, C375S350000, C708S313000
Reexamination Certificate
active
06714796
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a mobile communication terminal device such as a portable telephone, a car telephone, a radio transceiver, or the like.
In recent years, with the higher speed of data communication, various applications of the mobile communication terminal device are thought about in addition to the application of sound communication as a basic function. As one of them, there may be listed a music broadcasting service. This music broadcasting service is provided to playback the digital audio music data, in that the digital audio music data stored in the CD (Compact Disk), etc., are broadcasted from the external source via the network, etc. and they are reproduced by the mobile communication terminal device. In order to meet such service, a new hardware must be added to the existing mobile communication terminal device.
In case a music playback function is added to the mobile communication terminal device, such mobile communication terminal device must be equipped with a sound communication function portion and a music playback function portion.
The sound communication function portion includes a pulse code modulation (abbreviated as “PCM” hereinafter) CODEC having an analog-to-digital (abbreviated as “A/D” hereinafter) converter portion for converting a transmitting analog signal, which is transmitted, into a transmitting digital signal, and a digital-to-analog (abbreviated as “D/A” hereinafter) converter portion for converting a receiving digital signal, which is received, into a receiving analog signal.
While, the music playback function portion has a music playback function used in the CD player, etc., and includes an audio D/A converter for converting an audio digital signal, which is broadcasted, into an audio analog signal.
FIG. 9
shows a configuration of the existing mobile communication terminal device.
At the time of transmission, the transmitting analog signal, which is output from a microphone, is converted into the transmitting digital signal by an A/D converter constituting PCM-CODEC
203
, and then transmitted via a TX (transmitter portion)
201
and an antenna
205
.
At the time of reception, the receiving digital signal, which is received via the antenna
205
, is converted into the receiving analog signal by a D/A converter constituting the PCM-CODEC
203
via an RX (receiver portion)
202
, and then output as the receiving sound via a loudspeaker.
FIG. 10
shows a configuration of the mobile communication terminal device equipped with an audio D/A converter to meet the music broadcasting service.
At the time of transmission, the transmitting analog signal, which is output from the microphone, is converted into the transmitting digital signal by the A/D converter constituting the PCM-CODEC 203, and then transmitted via the TX (transmitter portion)
201
and the antenna
205
.
At the time of reception, the receiving digital signal, which is received via the antenna
205
, is converted into the receiving analog signal by the D/A converter constituting the PCM-CODEC
203
via the RX (receiver portion)
202
, and then output as the receiving sound via the loudspeaker.
Meanwhile, audio digital signals containing the left channel (L-ch) and the right channel (R-ch), which are received via the antenna
205
based on the music broadcasting service, are converted into audio analog signals by an audio D/A converter
204
via the RX (receiver portion)
202
, and then are output as audio sounds via the loudspeaker.
FIG. 11
shows a configuration of the PCM-CODEC
203
shown in FIG.
9
and FIG.
10
.
The PCM-CODEC
203
includes an over-sampling type A/D converter
101
for converting the transmitting analog signal, which is output from the microphone, into the transmitting digital signal; an over-sampling type D/A converter
102
of the delta-sigma modulation system, for converting the receiving digital signal into the receiving analog signal to output it to the loudspeaker; a digital filter
105
for executing the decimation process of the A/D-converted transmitting digital signal; and a digital filter
106
for executing previously the interpolation process of the receiving digital signal to be D/A-converted.
It is normal that the PCM-CODEC
203
has a 8-bit data word length of the &mgr;-law, but the CODEC which is extended up to 14 bit in place of the &mgr;-law may be used according to the specification. The sampling frequency is 8 kHz.
FIG. 12
shows a configuration of the audio D/A converter
204
.
The audio D/A converter
204
converts the audio digital signals containing the L-ch and the R-ch into analog signals, and includes digital filters
107
,
108
for executing the interpolation process the L-ch and R-ch digital signals respectively, and over-sampling type D/A converter
103
,
104
for converting the L-ch and R-ch digital signals, which have been subjected to the interpolation process, in the analog signal respectively.
The audio D/A converter
204
is employed in the digital audio such as CD, etc. The data word length is 16 bit (there is 24 bit in DVD (Digital Video Disk), etc.). The sampling frequency is 44.1 kHz in the CD, and is about 32 kHz to 48 kHz in other digital audio systems.
An operation of the PCM-CODEC
203
shown in
FIG. 11
will be explained hereinafter.
At the time of transmission, the transmitting analog signal, which is output from the microphone, is converted into the transmitting digital signal by the over-sampling type A/D converter
101
by using the delta-sigma modulation system, then is input into a digital filter
105
to accept the decimation process, and then is sent out to the transmitter portion as the transmitting output.
As the over-sampling frequency, the sampling clock which is several tens to several hundreds times the sampling clock used in the A/D conversion of the normal sound signal, for example, is employed. In the portable telephone, etc., the sampling frequency of 8 kHz is standard for the sound and the over-sampling frequency of 1.024 MHz which is 128 times the sampling frequency, for example, is employed.
In the A/D converter
101
of such delta-sigma modulation system, the so-called noise shaping operation and the over-sampling operation are performed, and the output (noise shaping output) is a 1-bit signal which has been subjected to the PDM (Pulse Density Modulation). The 1-bit PDM bit stream output is down-sampled up to 8 kHz, which is the sampling frequency of the sound data, by the digital (decimation) filter
105
and is also converted into digital data of a predetermined bit number.
At the time of reception, the receiving digital signal, which is supplied from the outside as the receiving input, is over-sampled by the digital filter
106
to limit the bandwidth, and then input into the over-sampling type D/A converter
102
. Here, the sound signal being converted into the receiving analog signal is supplied to the loud speaker and output as the telephone sound.
The digital filter
106
executes the quadruple over-sampling process and the bandwidth limiting process of the digital signal being input at the sampling frequency of 8 kHz. In addition, the digital filter
106
attenuates these fold-over frequency components simultaneously with the over-sampling process. Over-sampling data being processed by the digital filter
106
are input into the over-sampling type D/A converter
102
consisting of a noise shaper and an analog integration circuit, and then a 32-tuple over-sampling/ noise shaping process, for example, is applied to the data by the noise shaper to generate digital data as 1-bit stream data (compression waves generated by PDM). Also, this digital data is converted into the analog signal by the analog integration circuit by applying the integration process.
With the above, the operation of the PCM-CODEC
203
is explained. In this case, the digital filter
106
and the D/A converter
102
constituting the PCM-CODEC
203
and the audio D/A converter
103
,
104
shown in
FIG. 12
are different in the sampling frequency, the over-sampling rate, the c
Amemoto Ken
Mizukoshi Ryuji
Matsushita Electric - Industrial Co., Ltd.
Maung Nay
Pearne & Gordon LLP
Sharma Sujatha
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