Communications device

Details Communications device Communications device

1999-04-21

2003-04-15

Bost, Dwayne (Department: 2681)

Telecommunications

Transmitter

Diversity

C455S078000, C455S277100

Reexamination Certificate

active

06549760

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a communications device, and more particularly, to a communications device for communicating by selecting a predetermined antenna from a plurality of antennae.
2. Description of the Related Art
FIG. 4
is a block diagram of a conventional communications system. The conventional communications device
1
comprises a first antenna
2
and a second antenna
3
for transmitting and receiving; a switching circuit
4
for switching the first and second antennae
2
,
3
; a transmitter circuit
5
for supplying transmission signals to the first and second antennae
2
,
3
via the switching circuit
4
; a receiver circuit
6
supplied with reception signals received at the first and second antennae
2
,
3
via the switching circuit
4
; and a signal processing circuit
7
for modulating transmission signals and supplying them to the transmission circuit
5
and at the same time demodulating and outputting reception signals supplied from the receiver circuit
6
.
The first antenna
2
comprises an antenna element capable of transmitting and receiving, the antenna element being used as a transmission antenna during transmission and as a reception antenna during reception.
The second antenna element chiefly comprises an antenna element for receiving, the antenna element being used as a reception antenna element during reception. Both the first and second antennae
2
,
3
are connected to the switching circuit
4
.
FIG. 5
is a block diagram of a conventional connection switching circuit. The connection switching circuit
4
comprises a first switch
11
for selecting one or the other of either antenna
2
or antenna
3
and a second switch
12
for selecting one or the other of either the transmitter circuit
5
or the receiver circuit
6
.
The first switch
11
is an antenna selection switch. A first fixed contact t
1
is connected to the first antenna
2
, a second fixed contact is connected to the second antenna
3
and a moving contact t
3
is connected to the second switch
12
.
The moving contact t
3
of the first switch
11
is connected to either the first fixed contact t
1
or the second fixed contact t
2
according to an antenna selection signal supplied from the signal processing circuit
7
. When the antenna selection signal supplied by the signal processing circuit
7
is HIGH the moving contact t
3
is connected to the first fixed contact t
1
; when the antenna selection signal supplied by the signal processing circuit
7
is LOW the moving contact t
3
is connected to the second fixed contact t
2
.
The second switch
12
controls the switching between transmission and reception. A first fixed contact t
11
is connected to the transmitter circuit
5
, a second fixed contact t
12
is connected to the receiver circuit
6
and a moving contact t
13
is connected to the moving contact t
3
of the first switch
11
.
The moving contact t
13
of the second switch
12
is connected to either the first fixed contact t
11
or the second fixed contact t
12
according to a transmission-reception switching control signal supplied from the signal processing circuit
7
. When the transmission-reception switching control signal supplied by the signal processing circuit
7
is HIGH the moving contact t
13
is connected to the first fixed contact t
11
; when the transmission-reception switching control signal supplied by the signal processing circuit
7
is LOW the moving contact t
13
is connected to the second fixed contact t
12
.
The transmission circuit
5
comprises a power amplifier
21
and amplifies transmission signals generated by the signal processing circuit
7
. It should be noted that the transmitter circuit
5
does not in fact comprise only the power amplifier
21
but also includes other circuits as well.
The receiver circuit
6
comprises a low-noise amplifier
22
, and amplifies reception signals received by the first antenna
2
and the second antenna
3
and supplies them to the signal processing circuit
7
. It should be noted that the receiver circuit
6
does not in fact comprise only the low-noise amplifier
22
but also includes other circuits as well.
A description will now be given of the signal processing circuit
7
with reference once more to FIG.
4
.
As shown in
FIG. 4
, the signal processing circuit
7
has a transmission signal input terminal Ttx for inputting transmission signals; a reception signal output terminal Trx for outputting reception signals; a transmission enable signal input terminal Ttx-en to which is input a transmission enable signal for switching a processing mode of the signal processing circuit
7
to the transmit mode; and a reception enable signal input terminal Trx-en to which is input a reception enable signal for switching the signal processing mode of the signal processing circuit
7
to the receive mode.
When a signal is transmitted, the transmission enable signal input to the transmission enable signal input terminal Ttx-en is HIGH and the reception enable signal supplied to the reception enable signal input terminal Trx-en is LOW. As a result, the signal processing circuit
7
processing mode switches to the transmission mode, the transmission signal supplied to the transmission signal input terminal Tx is modulated and the modulated signal supplied to the connection switching circuit
4
. Additionally, the signal processing circuit
7
sets the transmission-reception switching control signal supplied to the first switch
11
of the connection switching circuit
4
or the antenna selection signal supplied to the second switch
12
of the connection switching circuit
4
to HIGH.
Additionally, when a signal is received, the transmission enable signal supplied to the transmission enable signal input terminal Ttx-en is LOW and the reception enable signal supplied to the reception enable signal input terminal Trx-en is HIGH. As a result, the signal processing circuit
7
processing mode switches to receive mode, the reception signal supplied from the receiver circuit
6
is demodulated and the demodulated signal output from the reception signal output terminal Trx. Additionally, the signal processing circuit
7
sets the antenna switching control signal supplied to the first switch
11
of the switching control circuit
4
to LOW and sets the transmission-reception switching signal supplied to the second switch
12
to either HIGH or LOW depending on the quality of the reception signals supplied from the first and second antennae
2
,
3
.
If, for example, the quality of the reception signals received at the first antenna
2
is better than the quality of the reception signals received at the second antenna
3
, then the signal processing circuit
7
sets the antenna selection signal sent to the first switch
11
to HIGH. With the antenna selection signal supplied from the signal processing circuit
7
at HIGH, the moving contact t
3
of the first switch
11
is connected to the first fixed contact t
1
, thus connecting the first antenna
2
to the receiver circuit
6
and supplying the reception signals received at the first antenna
2
to the signal processing circuit
7
.
Additionally, if the quality of the reception signals received at the first antenna
2
is worse than the quality of the reception signals received at the second antenna
3
, then the signal processing circuit
7
sets the antenna selection signal sent to the first switch
11
to LOW. With the antenna selection signal supplied from the signal processing circuit
7
at LOW, the moving contact t
3
of the first switch
11
is connected to the second fixed contact t
2
, thus connecting the second antenna
3
to the receiver circuit
6
and supplying the reception signals received at the second antenna
3
to the signal processing circuit
7
.
However, in the conventional communications device the second switch
12
for switching between transmission and reception and the first switch
11
for selecting either the first or second antenna are connected in series betwe

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