Telecommunications – Transmitter and receiver at same station – Having particular application of a transceiver
Reexamination Certificate
2000-06-09
2004-05-18
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at same station
Having particular application of a transceiver
C455S575100, C455S128000, C455S129000, C455S550100, C343S895000, C333S173000, C333S032000, C333S124000
Reexamination Certificate
active
06738603
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio communication apparatus and an impedance matching method and more particularly, to a radio communication apparatus with a retractable antenna and an impedance matching method of a radio communication apparatus of this sort, which make it possible to match the impedance between the antenna and the circuit connected to the antenna in a situation where the antenna environment is similar to a free space and another situation where the antenna environment is dissimilar from a free space.
2. Description of the Related Art
The portable telephone, which is a typical one of radio communication apparatuses, has several operation states, such as the stand-by state for waiting incoming messages or data, the dial-inputting state for inputting phone numbers, and the communication state for the transmission or reception operation. These operation states can be categorized into two classes, i.e., the “communication states” where the telephone performs the transmission or reception operation and the “non-communication” states where the telephone does not perform the transmission or reception operation.
In the “non-communication states”, the environment of the antenna is similar to a free space and therefore, it can be approximated as a free space. In the “communication states”, however, the environment of the antenna is not similar to a free space. This is because the telephone is often used in a location near the head of the user for the purpose of exchanging voice messages using the microphone and receiver on the telephone. Thus, it is typical that the environment of the antenna is unable to be approximated as a free space in the communication states.
Moreover, considering the state that the telephone is used for data transmission, this state belongs to the “communication states”; in this state, however, the telephone is usually used in a location far from the head of the user. This is because the microphone and receiver for exchanging voice messages is not necessary and because the telephone is usually operated along with a portable computer. As a result, the environment of the antenna can be approximated as a free space in the data transmission state.
Accordingly, if the operation states of the telephone are classified with respect to the environment of the antenna, they are categorized into two situations, i.e., the first situation similar to a free space and the second situation dissimilar from a free space. Thus, the input impedance of the antenna needs to be changed according to which one of these two situations is applicable.
Additionally, the antenna of the portable telephone is usually retractable and therefore, the environment of the antenna varies according to whether or not the antenna is retracted into the casing too.
Taking the above-described change in the antenna environment into consideration, conventionally, the configuration of portable telephones has been designed and developed. This is applicable to any other radio communication apparatuses having a retractable antenna.
FIG. 1
shows schematically the configuration of a prior-art radio communication apparatus, which is configured as a portable telephone.
As shown in
FIG. 1
, the prior-art radio communication apparatus
101
comprises a whip antenna
102
, a matching circuit
105
, a switch
106
with three terminals for switching the transmission and reception operations, a terminal matching circuit
107
, a transmission circuit
111
, a reception circuit
112
, a control circuit
113
, and a casing
120
. The matching circuit
105
, the switch
106
, the terminal matching circuit
107
, the transmission circuit
111
, the reception circuit
112
, and the control circuit
113
are located in the casing
120
. The antenna
102
is fixed to the casing
120
so as to be retractable into the casing
120
.
The whip antenna
102
includes a straight element
104
and a helical element
103
. The straight element
104
is supported by the casing
120
so as to be extendable from the casing
120
to the outside and retractable into its inside. The helical element
103
is connected in series to the straight element
104
. The antenna
102
emits a transmitting signal TS supplied from the transmission circuit
111
in the form of a radio wave and generates a reception signal RS from a radio wave received from the outside.
In the state where the straight element
104
is retracted into the casing
120
(which may be said that the whip antenna
102
is retracted hereinafter), only the helical element
103
protrudes from the casing
120
. On the other hand, in the state where the straight element
104
is extended to the outside of the casing
120
(which may be said that the whip antenna
102
is extended hereinafter), both the helical and straight elements
103
and
104
protrude from the casing
120
.
One terminal of the terminal matching circuit
107
is connected to a connector
121
and the other terminal thereof is connected to the ground. The circuit
107
has predetermined, specific impedance.
One terminal of the matching circuit
105
is connected to a connector
122
and the other terminal thereof is connected to a first terminal of the switch
106
. The circuit
105
serves to match the impedance between the antenna
102
and the transmission or reception circuit
111
or
112
.
When the whip antenna
102
is retracted into the casing
120
, as shown in
FIG. 1
, the bottom end of the straight element
104
is contacted with the connector
121
. Thus, the terminal matching circuit
107
is connected to the bottom end of the element
104
. The upper part of the element
104
is contacted with the connector
122
, thereby connecting the matching circuit
105
to the element
104
.
When the whip antenna
102
is extending from the casing
120
, the bottom end of the straight element
104
is apart from the connector
121
and as a result, the terminal matching circuit
107
is disconnected from the element
104
. The element
104
is kept in contact with the connector
122
and as a result, the matching circuit
105
is kept connected to the element
104
in this state.
The second and third terminals of the switch
106
are connected to the output terminal of the transmission circuit
111
and the input terminal of the reception circuit
112
, respectively. The switch
106
alternately connects one of the transmission and reception circuits
111
and
112
to the matching circuit
105
.
The transmission circuit
111
generates the transmission signal TS by modulating the carrier wave with specific transmission data. The data TS is outputted from the output terminal of the circuit
111
to the whip antenna
102
by way of the switch
106
and the matching circuit
105
. The operation of the circuit
111
is controlled by a transmission control signal TCS supplied from the control circuit
113
.
The reception signal RS, which is generated by the antenna
102
, is inputted into the input terminal of the reception circuit
112
by way of the matching circuit
105
and the switch
106
. The reception circuit
112
demodulates the reception signal RS thus supplied and extracts the data contained in the signal RS. The operation of the circuit
112
is controlled by the reception control signal RS.
If the reception signal RS contains a disconnection signal DCS, the reception circuit
112
outputs the signal DCS to the control circuit
113
. In this case, the circuit
113
stops the reception operation of the circuit
112
using the control signal RCS.
The control circuit
113
generates the switch control signal SCS, the transmission control signal TCS, and the reception control signal RCS and then, supplied them to the switch
106
, the transmission circuit
111
, and the reception circuit
112
, respectively.
The prior-art radio communication apparatus
101
operates in the following way.
On signal transmission, the switch
106
is operated to connect the transmission circuit
111
to the matching circuit
105
. The transmission sig
Gantt Alan T.
Maung Nay
NEC Corporation
Scully Scott Murphy & Presser
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