Telecommunications – Transmitter and receiver at same station – With frequency stabilization
Reexamination Certificate
2000-10-04
2001-11-27
Chang, Vivian (Department: 2682)
Telecommunications
Transmitter and receiver at same station
With frequency stabilization
C455S086000, C455S112000, C455S119000
Reexamination Certificate
active
06324385
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmitting and receiving apparatus arranged in a mobile wireless installation or the like.
2. Description of Related Art
FIG. 1
is a constitutional diagram showing a conventional transmitting and receiving apparatus. In
FIG. 1
,
1
indicates an antenna,
2
indicates a duplexer (hereinafter, called DUP) for outputting a reception wave Rx received in the antenna
1
to a receiving unit
9
and outputting a transmission wave Tx output from a transmitting unit
14
,
3
indicates a carrier wave generating unit for generating a reception carrier wave L
0
having the same frequency as a reception frequency f
RX
of the reception wave Rx and generating a transmission carrier wave L
1
having the same frequency as a transmission frequency f
TX
of the transmission wave Tx,
4
indicates a local oscillating unit, indicates a phased-lock-loop (hereinafter, called PLL) for generating the reception carrier wave L
0
having a frequency f
L0
(=f
RX
),
6
indicates a distributing unit for distributing the reception carrier wave L
0
generated in the PLL
5
,
7
indicates a PLL for generating a signal of which a frequency is equivalent to a difference value between the frequency f
RX
and the frequency f
TX
, and
8
indicates a mixer (hereinafter, called MIX) for mixing the signal generated in the PLL
7
with the reception carrier wave L
0
and outputting the transmission carrier wave L
1
.
Also,
9
indicates the receiving unit for mixing the reception carrier wave L
0
generated in the carrier wave generating unit
3
with the reception wave Rx and outputting reception signal,
10
indicates an amplifying unit for amplifying the reception wave Rx,
11
indicates a band pass filter,
12
indicates a filter for removing higher harmonic waves from the reception carrier wave L
0
generated in the carrier wave generating unit
3
, and
13
indicates an MIX for mixing the reception carrier wave L
0
with the reception wave Rx.
In addition,
14
indicates the transmitting unit for mixing the transmission carrier wave L
1
generated in the carrier wave generating unit
3
with the transmission signal and outputting the transmission wave Tx,
15
indicates a filter for removing higher harmonic waves from the transmission carrier wave L
1
generated in the carrier wave generating unit
3
,
16
indicates an MIX for mixing the transmission carrier wave L
1
with the transmission signal,
17
indicates a band pass filter, and
18
indicates an amplifier for amplifying the transmission wave Tx.
Next, an operation is described.
In this transmitting and receiving apparatus, the transmission of the transmission wave Tx and the reception of the reception wave Rx are simultaneously performed. However, a direct converter method is adopted to reduce both a size of the receiving unit
9
and a size of the transmitting unit
14
. In this direct converter method, the reception wave Rx is directly converted into the reception signal of a desired frequency, and the transmission signal is directly converted into the transmission wave Tx of a desired frequency.
More precisely, the reception carrier wave L
0
having the same frequency as the reception frequency f
RX
of the reception wave Rx is generated in the carrier wave generating unit
3
to directly obtain the reception signal of the desired frequency from the reception wave Rx.
Thereafter, when the reception carrier wave L
0
of the frequency f
L0
, which agrees with the reception frequency f
RX
, is generated in the carrier wave generating unit
3
, the reception carrier wave L
0
is mixed with the reception wave Rx in the receiving unit
9
, and the reception signal is output from the receiving unit
9
.
Therefore, the reception signal of the desired frequency can be taken in.
Also, because the transmission carrier wave L
1
having the same frequency as the transmission frequency f
TX
of the transmission wave Tx is generated in the carrier wave generating unit
3
to directly obtain the transmission wave Tx of the transmission frequency f
TX
from the transmission signal.
Thereafter, when the transmission carrier wave L
1
, of which the frequency f
L1
agrees with the transmission frequency f
TX
, is generated in the carrier wave generating unit
3
, the transmission carrier wave L
1
is mixed with the transmission signal in the receiving unit
14
, and the transmission wave Tx is output from the transmitting unit
14
.
Therefore, the transmission signal Tx of the transmission frequency f
TX
can be transmitted.
Because the conventional transmitting and receiving apparatus has the above-described configuration, the size of the receiving unit
9
and the size of the transmitting unit
14
can be made small. However, because the frequency f
L0
of the reception carrier wave L
0
agrees with the reception frequency f
RX
, the reception carrier wave L
0
leaks out to a front end unit (the antenna
1
and the DUP
2
) and functions as interference wave. Therefore, there is a problem that a DC offset occurs in the reception signal.
Also, because the frequency f
L1
of the transmission carrier wave L
1
agrees with the transmission frequency f
TX
, the transmission wave Tx leaks out to interfere with the carrier wave generating unit
3
. As a result, there are following problems. That is, the transmission carrier wave L
1
become unstable, a modulation precision of the transmitting unit
14
becomes worse, floor noise occurring in the modulating unit is increased, and electric power cannot be reduced in an electric power control operation which is performed in a CDMA or the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide, with due consideration to the drawbacks of the conventional transmitting and receiving apparatus, a transmitting and receiving apparatus in which the occurrence of a DC offset and the degradation of a modulation precision are prevented without increasing an area occupied by constituent elements of the transmitting and receiving apparatus.
The object is achieved by the provision of a transmitting and receiving apparatus, comprising;
carrier wave generating means for generating a reception carrier wave of which a frequency agrees with a reception frequency, generating a first transmission carrier wave of which a frequency is equivalent to 2N (N is a natural number) times of a difference value between the reception frequency and a transmission frequency, and generating a second transmission carrier wave of which a frequency is equivalent to a difference value between the frequency of the first transmission carrier wave and the reception frequency; receiving means for mixing the reception carrier wave generated by the carrier wave generating means with a reception wave and outputting a reception signal;
modulating means for de-multiplying by 2N the frequency of the first transmission carrier wave generated by the carrier wave generating means, mixing the first transmission carrier wave, of which the frequency is de-multiplied by 2N, with a transmission signal, and outputting a modulated wave; and
transmitting means for mixing the second transmission carrier wave generated by the carrier wave generating means with the modulated wave output from the modulating means, and outputting a transmission wave.
Therefore, because the frequency of the transmission carrier wave does not agree with the transmission frequency, there is no probability that a transmission wave leaks out to interfere with a carrier wave generating means. As a result, the degradation of a modulation precision on a transmission side can be prevented, and a spuriously occurring wave can be easily attenuated in a filter.
In a transmitting and receiving apparatus according to the present invention, it is preferred that the second transmission carrier wave is generated by mixing the first transmission carrier wave and a reception carrier wave.
Therefore, in cases where a mixer, which can be easily arranged in an integrated circuit and can be made small,
Itoh Kenji
Mori Kazuhiro
Nagano Hiroaki
Chang Vivian
Mitsubishi Denki & Kabushiki Kaisha
Ramos-Feliciano Eliseo
Rothwell Figg Ernst & Manbeck
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