Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Reexamination Certificate
2001-01-29
2002-10-15
Issing, Gregory C. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
C342S357490
Reexamination Certificate
active
06466163
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a GPS receiver and a portable communication apparatus, and more particularly, is suitably applied to a receiver for the Global Positioning System (GPS) which is used to measure the position of a moving object, for example.
2. Description of the Related Art
Heretofore, in the GPS, a GPS receiver receives satellite signals transmitted from plural GPS satellites, which are circling around the globe, and analyzes the received satellite signals to calculate the distance between each GPS satellite and the GPS receiver itself. Then, it calculates its current position from the calculated distances.
The satellite signal, which is transmitted from a GPS satellite, is a signal which has been subjected to spread spectrum processing with a pseudo noise (PN) code. This PN code is special for each GPS satellite.
Therefore, the GPS receiver can generate a station PN code for every GPS satellite, make the phase of the generated station PN code match that of the PN code of the satellite signal for synchronization, and perform tracking on the satellite signal for synchronous correction. Then, the GPS receiver performs de-spreading processing to demodulate a navigation message (orbit information for calculating a position) from each GPS satellite. As a result, the current position of the GPS receiver can be calculated from the navigation message.
In addition, such a GPS receiver could have a Code Division Multiple Access (CDMA) transmitting/receiving unit to transmit/receive data to/from the base station in the CDMA cellular system based on the Direct Sequence (DS) scheme conformed with the TIA/IS-95 standard in the United States of America, for example, so that the CDMA transmitting/receiving unit can inform the base station in the CDMA cellular system of its current position calculated.
Actually, as shown in
FIG. 1
, the GPS receiver
1
roughly consists of a GPS receiving unit
1
to demodulate a GPS received signal SI received from each GPS satellite, and a CDMA transmitting/receiving unit
3
to demodulate a CDMA received signal S
2
received from a base station in the CDMA cellular system and to transmit a CDMA transmission signal S
3
, produced by modulating transmission data, to the base station in the CDMA cellular system.
The CDMA transmitting/receiving unit
3
inputs the received CDMA received signal S
2
to a CDMA demodulator
4
. The CDMA demodulator
4
synchronizes the CDMA received signal S
2
to a CDMA demodulation control signal S
4
which is supplied from a CDMA control circuit
5
, performs the demodulation processing on it, and then outputs the resultant received data S
5
to the CDMA control circuit
5
.
Further, the CDMA control circuit
5
transmits transmission data S
7
such as voices to be transmitted, to a CDMA modulator
6
, and also transmits a CDMA modulation control signal S
8
, which is to control the spread spectrum processing in the CDMA modulator
6
, to the CDMA modulator
6
.
The CDMA modulator
6
modulates the transmission data S
7
in accordance with the CDMA modulating control signal S
8
and transmits the resultant signal, which has been subjected to the spread spectrum processing, as a CDMA transmission signal S
3
to a high frequency circuit and to the base station in the CDMA cellular system via a CDMA antenna (not shown).
Further, the CDMA control circuit
5
produces a system time signal S
6
. which is a standard timing of synchronization and demodulation processing, based on the result of demodulation, that is, the received data S
5
, and supplies it to a GPS control circuit
8
of the GPS receiving unit
2
.
The CDMA received signal S
2
is produced based on the GPS time which is obtained in such a manner that the base station in the CDMA cellular system receives and analyzes a satellite signal transmitted from the GPS satellite, so that the GPS control circuit
8
can roughly recognize the acquirement of synchronization and the demodulation timing of the demodulation processing for the GPS received signal SI based on the system time signal S
6
.
As described above, in the GPS receiving unit
2
, the GPS control circuit
8
roughly recognizes the acquirement of synchronization and the demodulation timing of the demodulation processing for the GPS received signal SI based on the system time signal S
6
, and supplies a GPS demodulation control signal S
9
based on the demodulation timing to the GPS demodulator
7
.
The GPS demodulator
7
synchronizes and demodulates the GPS received signal SI, received from each GPS satellite, based on the GPS demodulation control signal S
9
in a short time, thereby making it possible to remarkably reduce power consumption relating to the acquirement of synchronization and the demodulation processing.
Further, the GPS demodulator
7
outputs received data S
10
from every GPS satellite, which is obtained by the demodulation processing, to the GPS control circuit
8
. The GPS control circuit
8
calculates the current position of the GPS receiver
1
from the plurality of received data S
10
, which is obtained by the demodulation processing.
Thus the GPS receiver
1
informs the base station in the CDMA cellular system of its current position in such a manner that the current position obtained by the GPS control circuit
8
is passed through the CDMA control circuit
5
as the transmission data S
7
and is modulated by the CDMA modulator
6
and the resultant CDMA transmission signal S
3
is transmitted to the base station in the CDMA cellular system.
In the GPS receiving unit
2
of the GPS receiver
1
with the above structure, for example, the GPS receiving unit continuously receives the GPS received signal SI as shown in FIG.
2
A. And the CDMA transmitting/receiving unit
3
intermittently receives the control signal transmitted from the base station in the CDMA cellular system during the waiting time, until time Ta, continuously receives the control signal from the base station during the line-using time, between time Ta and time Td, and intermittently receives the control signal from the base station again during the waiting time, after time Td.
At this time, the GPS receiver
1
intermittently transmits line connection request data to the base station at predetermined intervals during the line-connection time, between time Ta and time Tb, and continuously transmits the CDMA transmission signal S
3
to the base station during the talk time, between time Tb and time Tc.
Therefore, the GPS receiver
1
outputs from the high frequency circuit much stronger radio waves than the received signal S
1
which is received by the GPS receiving unit
2
, while transmitting the line connection request data and continuously transmitting the CDMA transmission signal S
3
, which causes a problem in that interference of these radio waves with the GPS received signal S
1
remarkably deteriorates reception quality.
Further, in the GPS receiver
1
, in the case where the GPS receiving unit
2
intermittently receives the GPS received signal S
1
to reduce the power consumption as shown in
FIG. 2B
, at the same transmission/reception timing in the CDMA transmitting/receiving unit
3
as
FIG. 2A
, when the intermittent reception timing of the GPS received signal S
1
, the intermittent transmission timing of the line connection request data during the line connection time, and the continuous transmission timing of the CDMA transmission signal S
3
during the talk time coincide with each other, the strong radio waves, which are outputted when the line connection request data and the CDMA transmission signal S
3
are transmitted, interfere with the GPS received signal S
1
, which remarkably deteriorates reception quality.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of this invention is to provide a GPS receiver and a portable communication apparatus which allow a satellite signal to be demodulated without deterioration of reception quality.
The foregoing object and other objects of the invention have been achieved by the prov
Hasegawa Koji
Hori Katsuya
Naruse Tetsuya
Teranishi Koichiro
Issing Gregory C.
Maioli Jay H.
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