JPH1168613A - Transmission reception circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission reception circuit provided with a function of controlling transmission power where the circuit configuration is simplified, the circuit area and the cost are reduced. SOLUTION: This transmission reception circuit that has an RF switch 3 used to select transmission/reception controls power of a transmission signal by using the fact that the signal sent from a transmission system 1 is transmitted with a smaller power from an antenna 4 because of leakage in the RF switch 3 when contacts S, A in the RF switch 3 are open to disconnect the transmission system 1 and the antenna 4 than that when the transmission system 1 and the antenna 4 are connected to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission / reception circuit for transmitting and receiving a signal, and more particularly to a transmission / reception circuit having a function of controlling power of a transmission signal.

[0002]

2. Description of the Related Art For example, in a mobile communication device such as a PHS terminal, the power of a transmission signal is increased when the distance to the base station is long, and when the distance to the base station is short, the power of the transmission signal is naturally increased. As in the case where the distance is long, the power of the transmission signal may be kept large. However, especially in the case of battery-powered devices, the driving time is required to be extended, so the purpose is to reduce the power consumption. The power of the transmission signal is reduced.
In order to realize this, a conventional transmission / reception circuit uses a transmission power control circuit (hereinafter, referred to as a transmission power control circuit) for controlling the power of a transmission signal.
An APC circuit) is provided in a transmission system that generates a transmission signal.

[0003]

As described above, in the conventional transmitting / receiving circuit, in order to control the transmission power, A
The provision of the PC circuit has caused problems such as a complicated circuit configuration, an increase in circuit area, and an increase in cost. Also,
The APC circuit is composed of an amplifying element such as a transistor, and controls the transmission power by controlling the gain of the transistor. However, when it is necessary to extend the control range of the transmission power, a single amplifying element is used. However, since the controllable range is not so wide, it is necessary to configure an APC circuit with a plurality of amplifying elements, and the above problem has become more serious.

Accordingly, an object of the present invention is to provide a transmission / reception circuit having a function of controlling transmission power, which simplifies the circuit configuration, reduces the circuit area, and reduces the cost. .

[0005]

In order to achieve the above object, a transmitting / receiving circuit according to the present invention is a transmitting / receiving circuit having a switch for switching between transmission and reception, wherein the power of a transmission signal is controlled using the switch. .

Here, when the switch for switching between transmission and reception is switched to the transmission side, the transmission signal is output to the transmission medium as it is. However, the switch is switched to the reception side and the inside of the switch is switched. Even when the path through which the transmission signal is output to the transmission medium is in the open state, the transmission signal leaks in the switch depending on the degree of isolation, so that the switch is switched to the transmission side. The transmission power is lower than when the transmission is performed, and the transmission signal is output to the transmission medium. That is, transmission power can be controlled using the switch. The present invention focuses on this point.

According to the configuration of the present invention in which transmission power is controlled using a switch for switching between transmission and reception, it is not necessary to provide an APC circuit depending on the range in which transmission power is controlled. Also, if the transmission power is controlled by using both the APC circuit and the switch, the transmission power can be controlled in a wider range than when the transmission power is controlled using only the APC circuit. In other words, when controlling the transmission power within the same range, the APC
This also means that the number of amplification elements required for the circuit will be reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a transmitting / receiving circuit according to an embodiment of the present invention. In the figure, 1
Is a transmission system, 2 is a reception system, 3 is an RF switch, 4 is an antenna, 5 is a reception level detection circuit, and 6 is a microcomputer (hereinafter abbreviated as “microcomputer”).

The RF switch 3 has three terminals S, R, A and a control terminal C. The terminal S is on the output side of the transmission system 1, the terminal R is on the input side of the reception system 2, and the terminal A Is antenna 4
Side, and a signal input to the control terminal C causes a short circuit between the terminal S and the terminal A,
Alternatively, whether or not the terminal R and the terminal A are short-circuited is switched. And this RF switch 3
Conventionally, it is used only for switching between transmission and reception, but in the present embodiment, it is also used for controlling transmission power as described later.

The control terminal C of the RF switch 3 is provided with a control signal C3 from the microcomputer 6,
Switches between two terminals that are short-circuited in the RF switch 3. Also, control signals C1 and C2 are supplied from the microcomputer 6 to the transmission system 1 and the reception system 2, respectively, and the microcomputer 6 controls the operation / non-operation of the transmission system 1 and the reception system 2.

The operation performed by the microcomputer 6 at the time of reception and transmission in the above configuration will be described. First, at the time of reception, the microcomputer 6 determines whether the contact R of the RF switch 3 is
Is short-circuited to connect the receiving system 2 and the antenna 4 to each other, and the receiving system 2 is set to the operating state. In this way, the reception system 2 performs a predetermined process on the reception signal input from the antenna 4 via the free space as the transmission medium.

In addition, the reception level detection circuit 5
It is connected to the output side of the receiving system 2 and detects the level of the received signal. Then, the microcomputer 6 performs predetermined control according to the reception level detected by the reception level detection circuit 5, and a good reception state is ensured.
The reception level detected by the reception level detection circuit 5 is held until the next reception.

On the other hand, at the time of transmission, when the reception level detected by the reception level detection circuit 5 at the time of the last reception is smaller than a predetermined level, the microcomputer 6 determines whether the contact S and the contact A of the RF switch 3 are connected. The transmission system 1 and the antenna 4 are connected to each other by short-circuiting, and the transmission system 1 is set to an operation state.

Conversely, if the reception level detected by the reception level detection circuit 5 at the time of the last reception is equal to or higher than a predetermined level, the microcomputer 6 communicates with the communication partner (for a PHS terminal or the like, the base station). ) Is short, and it is determined that communication is possible even if the transmission power is reduced, so that the contact R and the contact A of the RF switch 3 are short-circuited and the reception system 2 and the antenna 4 are connected.
Are connected, that is, the transmission system 1 and the antenna 4
And the transmission system 1 is put into operation.

As described above, at the time of transmission, the distance to the communication partner is determined based on the reception level at the time of the last reception. A transmission / reception circuit for switching transmission / reception by the RF switch 3 is incorporated. Since the device normally communicates by repeating transmission and reception in a time-division manner, there is no great deviation between the determined distance and the actual distance.

Here, when the transmission system 1 and the antenna 4 are in a connected state, the transmission signal emitted from the transmission system 1 is naturally output from the antenna 4 to a free section as a transmission medium. However, even when the transmission system 1 and the antenna 4 are in a cutoff state, depending on the degree of isolation between the contact S and the contact A in the RF switch 3, the RF Since the switch 3 leaks from the contact S to the contact A, the signal is output from the antenna 4 in a form in which the transmission power is smaller than when the connection between the transmission system 1 and the antenna 4 is in a connected state. Specifically, the output of the transmission signal input to the terminal S is s [dB
m], and if the isolation between the contact S and the contact A in the RF switch 3 is i [dB], si [dBm]
Is input to the terminal A and output from the antenna 4.

That is, in the transmitting / receiving circuit of this embodiment,
When the microcomputer 6 performs the control as described above, the transmission power is controlled by using the RF switch 3 which has conventionally been used only for switching between transmission and reception. By doing so, it is not necessary to provide a conventional APC circuit depending on the control range of the transmission power.

As shown in FIG. 2, an APC circuit 7 may be provided in the transmission system 1 as in the prior art, and the transmission power may be controlled by using the RF switch 3 and the APC circuit 7 together. By doing so, it is possible to extend the range in which the transmission power is controlled as compared with the case where the transmission power is controlled using only the APC circuit 7. In other words, when controlling the transmission power in the same range, the number of amplifying elements required for the APC circuit 7 is reduced.

In a transmission / reception circuit for switching transmission / reception by the RF switch 3, transmission and reception are alternately repeated, for example, in a time-division manner, so that transmission and reception are not performed simultaneously. Since the system 2 is in the non-operating state, the contact S of the RF switch 3 is opened at the time of transmission, and the transmission signal from the transmission system 1
Even if the switch 3 leaks from the contact S, the receiving system 2
Does not adversely affect Similarly, at the time of reception, the transmission system 1 is inactive and no transmission signal is generated. Therefore, at the time of reception, the contact S of the RF switch 3 is open, but there is no signal leaking from the contact S. It does not adversely affect system 2. However, RF switch 3
The degree of isolation between the terminal S to which the transmission system 1 is connected and the terminal R to which the reception system 2 is connected and the terminal A to which the antenna 4 is connected are increased. It is desirable to keep.

The present invention is not limited to the above-described embodiment, but may take various forms without departing from the structure of the present invention. For example, in each of the above-described embodiments, the microcomputer performs each control including the control of the transmission power, but the above-described units may be controlled by another method.

[0021]

As described above, according to the transmission / reception circuit of the first aspect, it is not necessary to provide an APC circuit depending on the range in which the transmission power is controlled, thereby simplifying the circuit configuration and reducing the circuit area. Thus, cost reduction can be realized.

Further, according to the transmitting / receiving circuit of the present invention, the range of controlling the transmission power can be expanded as compared with the case where the transmission power is controlled using only the APC circuit. The control range of the transmission power can be expanded without increasing the area and the cost. From a different point of view, when controlling the transmission power in the same range, the number of amplifying elements required for the APC circuit is reduced, which simplifies the circuit configuration, reduces the circuit area, and reduces the cost. It is also possible to realize.

The above-mentioned effects obtained by the present invention are as follows.
This is very effective because it directly leads to downsizing and cost reduction of the device in which the transmitting / receiving circuit is incorporated.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmission / reception circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of a transmitting / receiving circuit according to an embodiment of the present invention, which is different from the block diagram shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmission system 2 reception system 3 RF switch 4 antenna 5 reception level detection circuit 6 microcomputer 7 APC circuit

Claims (2)

[Claims] 1. A transmission / reception circuit having a switch for switching between transmission and reception, wherein the power of a transmission signal is controlled using the switch. 2. A transmission power control circuit for controlling power of a transmission signal, wherein the switch and the transmission power control circuit are used together to control the power of the transmission signal. 2. The transmitting / receiving circuit according to claim 1.