Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-05-31
2003-10-28
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S815000, C725S070000
Reexamination Certificate
active
06639555
ABSTRACT:
TECHNICAL FIELD
The present invention relates, in particular, to an antenna device to be attached to a body of an automobile for receiving, for example, AM, FM, or TV broadcasting or wireless telephone, etc. and to a communication system using such an antenna device.
BACKGROUND ART
With the advance of the car multimedia era, in addition to an AM/FM radio, various radio equipments such as a TV receiver, a wireless telephone set, and a navigation system have been recently installed in the automobile. Also hereafter, information and services may be increasingly provided through radio wave and the importance of an antenna will grow accordingly.
Generally, in the wireless telephone set or any other communication devices which are used for mobile communication and are capable of transmitting and receiving, the antenna is used for both transmitting and receiving and a single terminal connected to that antenna performs a double function of an input terminal for the receiving section and an output terminal for the transmitting section through a common component such as a divider, a mixer, a circulator, or a switch or the like. During the receiving operation, such a common component prevents a received signal from entering the transmitting section through the antenna and allows it to enter the receiving section properly. On the contrary, during the transmitting operation, that component prevents a transmission signal from entering the receiving section from the transmitting section and allows it to be emitted through the antenna.
As described above, however, when an antenna is used for both transmitting and receiving with a common component in a communication device, it may generally require a high costcommon component and the communication device itself may become very expensive. In addition, there is a problem that the reception sensitivity may be degraded with an increased transmission loss by using a single antenna with a common component.
Moreover, since a receiving amplifier and a transmitting amplifier are certainly installed at the side of the communication device, there is a problem that a cable connecting between the antenna and the communication device may degrade the reception level and the transmission power.
DISCLOSURE OF THE INVENTION
In view of these problems of conventional antennas, the present invention aims to provide an antenna device and a communication system which can improve the reception sensitivity with a reduced transmission loss and which can be implemented at a lower cost.
Also, the present invention aims to provide an antenna device which can further improve its gain.
In addition, the present invention aims to provide a digital television broadcasting receiving device and a receiving method which can reduce reception disturbance during the mobile reception of digital data.
A 1st invention of the present invention (corresponding to claim 1) is an antenna device comprising:
a conductive earth substrate;
a receiving element located in the proximity of said conductive earth substrate and having a receiving terminal; and
a transmitting element located in the proximity of said receiving element and having a transmitting terminal,
characterized in that an end of said receiving element and an end of said transmitting element are connected to said conductive earth substrate for grounding through a common portion and the frequency band of said receiving element is different from that of said transmitting element.
A 2nd invention of the present invention (corresponding to claim 2) is an antenna device comprising:
a conductive earth substrate;
a receiving element located in the proximity of said conductive earth substrate and having a receiving terminal; and
a transmitting element located in the proximity of said receiving element and having a transmitting terminal,
characterized in that an end of said receiving element and an end of said transmitting element are connected to said conductive earth substrate for grounding at separate locations and the frequency band of said receiving element is different from that of said transmitting element.
A 3rd invention of the present invention( corresponding to claim 12) is an antenna device comprising:
a conductive earth substrate;
an antenna element having an end connected to said conductive earth substrate for grounding and formed on a common circuit board; and
a feeding terminal pulled out of said antenna element,
characterized in that a resonant circuit is inserted between said feeding terminal and the other end of said antenna element which is not grounded.
A 4th invention of the present invention (corresponding to claim 18) is a communication system comprising:
an antenna device having a conductive earth substrate, an antenna element formed on a common circuit board located in the proximity of said conductive earth substrate, and a receiving amplifier provided on said common circuit board between said antenna element and a feeding terminal;
a receiver having a power supply section to supply electric power to said receiving amplifier of said antenna device; and
a feeding line for connecting said feeding terminal of said antenna device to a signal input section of said receiver,
characterized in that a direct-current blocking capacitor is provided between said receiving amplifier of said antenna device and said feeding terminal and at the input terminal of a receiving amplifier of said receiver, respectively, and electric power is supplied by said power supply section to said receiving amplifier of said antenna device through said feeding line.
A 5th invention of the present invention (corresponding to claim 20) is a communication system comprising:
an antenna device of the present invention (corresponding to claim 15);
a receiver having a receiving channel setting circuit which generates a bias voltage for said voltage-variable capacitor element of said antenna device; and
a feeding line for connecting a signal input section of said receiver to a feeding terminal of said antenna device,
characterized in that said voltage-variable capacitor element of said antenna device is connected to said feeding terminal, a direct-current blocking capacitor is provided between said antenna element and said feeding terminal and at the input terminal of a receiving amplifier of said receiver, respectively, and a receiving channel is established by varying the bias voltage generated by said receiving channel setting circuit.
A 6th invention of the present invention (corresponding to claim 21) is a communication system comprising:
an antenna device of the present invention (corresponding to any one of claims 1 through 10);
a communication device having a receiving amplifier and a transmitting amplifier;
a receiving connection line for connecting the receiving terminal of said antenna device to said receiving amplifier of said communication device; and
a transmitting connection line for connecting the transmitting terminal of said antenna device to said transmitting amplifier of said communication device.
A 7th invention of the present invention (corresponding to claim 22) is a communication system comprising:
an antenna device having a conductive earth substrate, a receiving element having a receiving terminal formed on a common circuit board located in the proximity of said conductive earth substrate, a transmitting element having a transmitting terminal formed on said common circuit board located in the proximity of said receiving element, and a transmitting/receiving changeover circuit provided on said common circuit board and capable of switching said receiving terminal and said transmitting terminal;
a feeding line connected to said transmitting/receiving changeover circuit; and
a communication device connected to said feeding line and capable of both transmitting and receiving, characterized in that said transmitting/receiving changeover circuit of said antenna device is controlled by using a switch signal to change over to the transmission operation in said communication device.
A 8th invention of the present invention (correspondin
Kane Joji
Nomura Noboru
Sasaki Michio
Yamada Satoshi
Yanase Akinori
Ho Tan
Matsushita Electric - Industrial Co., Ltd.
Smith , Gambrell & Russell, LLP
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