Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
2000-06-14
2003-05-13
Nguyen, Lee (Department: 2683)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S101000, C455S103000, C455S132000, C455S272000
Reexamination Certificate
active
06564069
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication apparatus suitable for use with a combination type portable telephone set which can transmit and receive in accordance with a plurality of transmission/reception systems.
2. Description of the Related Art
In mobile telecommunication wherein a portable telephone set or the like is used, radio wave propagation across a plurality of obstacles is expected upon transmission/reception, for example, in an urban district. Arriving waves having passed through a plurality of paths suffer from significant fading, and as a result, communication failure or communication interruption in mobile communication by standing waves originating from such fading occurs. Therefore, in mobile communication, a diversity system is sometimes used wherein two or more antennae are used for transmission/reception and one of received waves which has a higher level is selected or two waves are combined so that the probability in deterioration of the reception quality may be reduced when compared with another case wherein a single received wave is use. Generally, a portable telephone set uses selection combining wherein only that one of a plurality of fading waves inputted individually using a plurality of antennae which has a maximum envelope level is selectively received.
Conventionally, such a portable telephone set of the PDC (personal digital cellular)/PHS (personal handyphone system) combination type employing the diversity system as shown in
FIG. 5
is known. Referring to
FIG. 5
, the conventional portable telephone set of the PDC/PHS combination type shown includes a PHS transmitter-receiver
30
A, a PDC transmitter-receiver
30
B, and a CPU
312
for controlling the transmitter receivers
30
A and
30
B. The PHS transmitter-receiver
30
A includes a PHS antenna circuit
301
having a single antenna, a PHS reception circuit
302
and a PHS transmission circuit
303
, a transmission/reception switching circuit
301
a
, a phase-locked loop (PLL) IC
304
, and a PHS modulation/demodulation circuit
305
. Meanwhile, the PDC transmitter-receiver
30
B includes a PDC antenna circuit
306
having two antennae, an antenna switching circuit
307
, a PDC reception circuit
308
and a PDC transmission circuit
310
, a PDC local circuit
309
, and a PDC modulation/demodulation IC
311
.
It is expected that such a portable telephone set of the combination type as described above is used such that both of transmission/reception systems operate for reception in order to make up for drawbacks of both of the PDC and PHS signal systems particularly in a reception waiting state. Generally, the PDC system is more advantageous upon high speed movement of the telephone set or in terms of the extent of a service area, and the PHS is more advantageous when the telephone set is used on a subway or on an underground market. Further, where such a great number of other users use telephone sets that connection of a telephone call cannot be established readily, one of the systems which has a comparatively great number of free circuits can be selectively used for a telephone call.
When such a portable terminal set of the combination type as described above is designed, a control system is sometimes used wherein, in order to suppress power consumption or from some other object, operation of the two systems is not controlled finely in a waiting state, but when communication is proceeding using one of the PDC and PHS transmission/communication systems, the power supply to a radio section of the transmission/reception system which is not in use is disconnected.
However, the conventional portable telephone set of the combination type has the following problems.
In particular, the PDC and PHS transmission/reception systems are complicated in control for establishment of synchronism due to measures for prevention of tapping and so forth, and usually they perform transmission/reception operations independently of each other until it is confirmed that reception data from one of the transmission/reception systems is a telephone number of the telephone set of the combination type itself. Accordingly, when either one of the PDC and PHS transmission/reception systems performs a transmission/reception operation such as position registration, the other system side may be at a reception timing of intermittent reception. As a result, the conventional portable telephone set of the combination type is disadvantageous in that one of the two systems cannot perform reception accurately and may possibly come out of synchronism.
Further, if synchronism is lost, then operation such as continuous reception is performed in order to establish synchronism again, resulting in another disadvantage that unnecessary power is dissipated.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a mobile communication apparatus of the diversity system including a plurality of transmitter-receivers of different transmission/reception systems wherein a drop of the antenna reception sensitivity of one system by an output from the antenna of the other system is minimized and the synchronism keeping accuracy is augmented and besides unnecessary dissipation of power is prevented.
In order to attain the object described above, according to the present invention, there is provided a mobile communication apparatus, comprising a first transmitter-receiver for outputting, upon transmission, a gain decrease instruction, the first transmitter-receiver having a transmission antennae, a second transmitter-receiver including a plurality of antennae and operable for selecting one of the plurality of antennae which has a high antenna gain so as to be used for reception, the first and second transmitter-receivers employing different transmission/reception systems from each other, and gain adjustment means for decreasing an antenna gain of one of the plurality of antennae of the second transmitter-receiver which has a high degree of coupling to the transmission antenna of the first transmitter-receiver in accordance with the gain decrease instruction.
The gain adjustment means may operate in response to a transmission control signal from the first transmitter-receiver.
The gain adjustment means may be a Schottky barrier diode which is connected, on a cathode side thereof, to that one of the plurality of antennae of the second transmitter-receiver which has a high degree of coupling to the transmission antenna of the first transmitter-receiver and connected, on an anode side thereof, to the first transmitter-receiver and is turned on in response to arrival of the gain decrease instruction.
Alternatively, the gain adjustment means may be a variable capacity diode which is connected between the first transmitter-receiver and that one of the plurality of antennae of the second transmitter-receiver which has a high degree of coupling to the transmission antenna of the first transmitter-receiver and is turned on in response to arrival of the gain decrease instruction.
The first transmitter-receiver may be a transmitter-receiver of the personal handyphone system, and the second transmitter-receiver may be a transmitter-receiver of the personal digital cellular system.
Where a mobile communication apparatus having such a construction as described above is incorporated in a portable telephone set, the portable telephone set becomes a portable telephone set of the combination type. In this instance, preferably the antennae employ a space diversity system and selective combining is used as a combination reception method.
Where the present invention is applied to a portable telephone set of the PDC/PHS combination type, when the PHS section transmits during intermittent waiting of the PDC section, the gain of one of the two PDC antennae which exhibits higher input power of a PHS transmission wave, that is, the gain of the antenna which has a higher degree of coupling to the PHS antenna, is decreased while the other antenna which exhibits lower input power of the PHS tr
Moorman Earl
NEC Corporation
Nguyen Lee
LandOfFree
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