Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-02-28
2003-11-25
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S767000
Reexamination Certificate
active
06653977
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a wireless handset, particularly to a wireless handset mounted with independent antennas for transmission and for receiving preferable for a wireless handset used in a communication system in which different frequencies for transmission and for receiving are simultaneously used.
Currently and generally, according to a wireless handset used in a communication system in which different frequencies for transmission and for receiving are simultaneously used, in order to carry out transmission and receiving by a single antenna, there is provided a duplexer between a transmission system circuit and a receiving system circuit and an antenna such that a transmitted signal is directed to the antenna but is not directed to the receiving system circuit and a received signal is directed from the antenna to the receiving system circuit but is not directed to the transmission system circuit. According to such a constitution constructed by the antenna, the duplexer and the transmission/receiving systems, transmission power is lost in the transmission system and minimum receiving power sensitivity is restricted in the receiving system by insertion loss of the duplexer. Loss of passband is increased when an attenuation amount of stopband is intended to sufficiently ensure in a communication system having a wide transmission and receiving bandwidth, particularly a communication system in which frequency interval for transmission and receiving is near, that is, a frequency interval of passband and stopband in a transmission or receiving filter of the duplexer is near. Loss of transmission power in a wireless handset gives rise to a need of ensuring extra battery capacity and hampers downsized formation necessary for the wireless handset. Further, loss of receiving power deteriorates the minimum receiving power sensitivity and hampers promotion of function of wireless device.
SUMMARY OF THE INVENTION
Hence, according to a conventional wireless handset, there is proposed a constitution in which independent narrow band antennas are provided respectively for a transmission and a receiving system, the antennas are directly connected to a transmission system circuit and a receiving system circuit to thereby enable to downsize the handset and promote its function in Japanese Patent Laid-open (Kokai) No. Hei 11-251948. An example of the constitution is shown by FIG.
13
.
In
FIG. 13
, numeral
200
designates a circuit board of a wireless handset and numerals
210
and
220
designate a transmission system circuit and a receiving system circuit respectively provided on the circuit board
200
. A transmitted signal generated by the transmission system circuit
210
is radiated to space from a built-in antenna
160
in which only transmission frequency band constitutes passband via a radio frequency (RF) filter for transmission
301
. A signal to be received in space is caught by a helical antenna
170
in which only receiving frequency band constitutes passband when an exterior antenna is contained and is transmitted from an exterior antenna electricity feed point
172
above the circuit board
200
connected to an electricity feed point
171
of the helical antenna to the receiving system circuit
220
via a receiving radio frequency (RF) filter
302
. When the exterior antenna is extended, by connecting the exterior antenna electricity feed point
172
to an electricity feed point
174
of a monopole antenna
173
in which only the receiving frequency band constitutes passband, a signal caught by the monopole antenna
173
is transmitted to the receiving system circuit
220
.
According to the constitution, the built-in antenna
160
and the helical antenna
170
or the monopole antenna
173
which is the exterior antenna are constructed by constitutions of narrow band. That is, gain is low at a received frequency in the antenna for transmission and sensitivity is low at a transmitted frequency in the antenna for receiving and accordingly, an attenuation amount at stopband is not so much needed in the radio frequency (RF) filters
301
or
302
provided between the antennas and the transmission system circuit
210
or the receiving system circuit
220
. In the case of a filter in which the attenuation amount at stopband is not so much needed, the insertion loss can be restrained low. Therefore, the wireless handset according to the constitution realizes downsized formation by reducing battery capacity by reducing loss of transmission power and realizes promotion of the minimum receiving power sensitivity by reducing loss of receiving power.
According to the conventional wireless handset proposed in Japanese Patent Laid-open (Kokai) No. Hei 11-251948, the transmission and receiving antennas are respectively constructed by the constitutions in narrow band and accordingly, the attenuation amounts at stopband of the radio frequency (RF) filters respectively for transmission and receiving provided respectively between the transmission and receiving antennas and the transmission and receiving circuits may be restrained low. However, even the antenna of narrow band is provided with more or less sensitivity in near frequency band and accordingly, there poses a problem in a communication system in which frequency intervals for transmission and receiving are near to each other, in which the antenna for transmission is provided with more or less sensitivity in receiving band and the antenna for receiving is provided with more or less sensitivity in transmission band, the attenuation amount of stopband of the radio frequency (RF) filter cannot be restrained low in the conventional constitution of the wireless handset and accordingly, the insertion loss cannot be reduced.
It is an object of the present invention to provide a novel wireless handset achieving downsized formation and promotion of function by using independent antennas for transmission and receiving and restraining interference between the transmission and receiving antennas in a communication system in which different and near frequencies for transmission and for receiving are simultaneously used.
The above-described problem of the present invention can effectively be resolved by providing a magnetic current antenna for transmission and a magnetic current antenna for receiving arranged in parallel with each other such that respective magnetic currents are disposed on a straight line in a wireless handset used in a communication system in which different frequencies for transmission and for receiving are simultaneously used.
A plurality of magnetic current antennas can mostly reduce interference among magnetic antennas when the antennas are arranged such that magnetic currents are aligned in a straight line and accordingly, when the magnetic current antennas for transmission and for receiving are arranged in parallel with each other such that respective magnetic currents are disposed on a straight line, interference among the antennas for transmission and for receiving is minimized and there can be reduced signal leakage from a radio frequency circuit for transmission to a radio frequency circuit for receiving which becomes problematic in a wireless handset simultaneously carrying out transmission and receiving. When the signal leakage among the radio frequency circuits for transmission and for receiving is small, there can be reduced attenuation amounts of stopband in radio frequency filters respectively provided between the antennas for transmission and for receiving and the transmission and receiving circuits. Generally, a radio frequency filter having a small attenuation amount of stopband can be fabricated with small loss of passband. Therefore, by adopting such a means, a wireless handset can be downsized by reducing battery capacity since power loss in transmission is reduced and minimum receiving power sensitivity function of a wireless handset can be promoted since power loss of receiving can be reduced.
Further, the above-described problem of the present invention can effectively b
Okabe Hiroshi
Takei Ken
Chen Shih-Chao
Wong Don
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