JP3971668B2 - Transmission / reception control circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmission / reception control circuit that is used in a mobile communication device that can use a plurality of transmission / reception control methods and is arranged between an antenna, a transmission circuit, and a reception circuit.
[0002]
[Prior art]
Electronic devices such as cellular phones have built-in transmission / reception control devices such as high-frequency switch parts, and in recent years, the circuit configuration has become complicated so that a plurality of transmission / reception communication systems can be used.
[0003]
As a transmission / reception control circuit of such a conventional electronic apparatus, for example, as shown in FIG. 4, an antenna 41, a first transmission circuit 44a, a second transmission circuit 44b, a first reception circuit 45a, and a second transmission are provided. The transmission / reception signal of the first transmission / reception communication method is connected to the antenna 41 and the first transmission circuit 44a or the first reception circuit 44b, and is connected to the circuit 45b to perform transmission / reception in a higher frequency band than the first transmission / reception signal The transmission / reception signal of the second transmission / reception communication system is switched between the antenna 41 and the second transmission circuit 45a or the second reception circuit 45b.
[0004]
The antenna 41 is connected to a low-pass filter 42a through which transmission / reception signals of the first transmission / reception communication system pass and a high-pass filter 42b through which transmission / reception signals of the second transmission / reception communication system pass, and the low-pass filter 42a includes: A first switch circuit 43a for switching the first transmission / reception signal to the first transmission circuit or the first reception circuit is connected between the first transmission circuit 44a and the first reception circuit 44b, and the high-pass filter 2b. And a second switch circuit 43b for switching the second transmission / reception signal to the second transmission circuit 45a or the second reception circuit 45b is connected between the second transmission circuit 5a and the second reception circuit 5b. ing.
[0005]
Although not shown in the drawing, the first switch circuit 43a and the second switch circuit 43b are composed of diodes, inductors (strip lines), capacitors, and the like that switch the circuits on and off. In recent years, the circuits are integrated. Semiconductor switch circuits are also used. In particular, if a GaAs switch circuit is used, the current consumption of the circuit can be reduced. Therefore, in the case of a mobile phone, the battery life can be extended.
[0006]
[Problems to be solved by the invention]
However, while the GaAs switch circuit improves the circuit characteristics, it has a drawback of being easily destroyed by static electricity. That is, since the transmission / reception control circuit is the circuit closest to the antenna, it is directly damaged by an electrostatic surge voltage of about 300 to 500 MHz that is generated when the antenna is touched by a human body. For this reason, countermeasures against static electricity have been applied to the antenna, or a static elimination circuit has been provided between the antenna and the transmission / reception control circuit. However, such a method also contributes to the deterioration of the reception sensitivity of the mobile phone. It was.
[0007]
The present invention has been devised in view of the above-described drawbacks, and an object of the present invention is to provide a transmission / reception control circuit with good reception sensitivity and low current consumption while removing static electricity.
[0008]
[Means for Solving the Problems]
The transmission / reception control circuit of the present invention is connected to the antenna, the first and second transmission circuits, and the first and second reception circuits, and transmits / receives a transmission / reception signal of the first transmission / reception communication system to the antenna and the first transmission. A switch for connection to the circuit or the first receiving circuit, and a transmission / reception signal of a second transmission / reception communication scheme that performs transmission / reception operation in a higher frequency band than a transmission / reception signal of the first transmission / reception communication scheme. A transmission / reception control circuit for switching connection to the transmission circuit or the second reception circuit, wherein a transmission / reception signal of the first transmission / reception communication system passes through the antenna and a transmission / reception signal of the first transmission / reception communication system. A low-pass filter that blocks a signal in a higher frequency band, and a transmission / reception signal of the second transmission / reception communication method passes and transmits / receives the second transmission / reception communication method. A high-pass filter that blocks signals in a frequency band lower than the signal is connected, and the low-pass filter is connected to the first transmission circuit and the first reception circuit via an antistatic circuit. A first GaAs switch circuit that switches a transmission / reception signal of the first transmission / reception communication method to the first transmission circuit or the first reception circuit is connected, and the high-pass filter, the second transmission circuit, and the second And a second GaAs switch circuit for switching a transmission / reception signal of the second transmission / reception communication method to the second transmission circuit or the second reception circuit. To do.
[0009]
The transmission / reception control circuit of the present invention is characterized in that, in the above configuration, the first GaAs switch circuit and the second GaAs switch circuit are formed in the same GaAs element.
[0010]
Furthermore, the transmission / reception control circuit according to the present invention is configured such that, in the above configuration, a signal in a higher frequency band of a transmission signal of the first transmission / reception control method is provided between the second GaAs switch circuit and the second transmission circuit. This is characterized in that a harmonic prevention filter for preventing the above is arranged.
[0011]
Furthermore, the transmission / reception control circuit according to the present invention is characterized in that, in the above-described configuration, the second transmission / reception communication system has two communication systems in which frequency bands of transmission / reception signals are close to each other.
[Action]
According to the transmission / reception control circuit of the present invention, the first low-pass filter is connected to the first transmission circuit and the first reception circuit via the antistatic circuit (high-pass filter, inductor element, varistor element). The first GaAs switch circuit is protected by an antistatic circuit while being easily destroyed by static electricity by connecting the first GaAs switch circuit that switches the transmission / reception signal to the first transmission circuit or the first reception circuit. Therefore, a transmission / reception control circuit resistant to static electricity can be obtained.
[0012]
At this time, since the second GaAs switch circuit is prevented from being destroyed by static electricity being blocked by the high-pass filter connected to the previous stage, there is no need to form an antistatic circuit and there are no extra parts. Thus, a transmission / reception control circuit with excellent reception sensitivity can be obtained.
[0013]
Further, according to the transmission / reception control circuit of the present invention, since the first GaAs switch circuit and the second GaAs switch circuit are formed in the same GaAs element, circuit components are reduced. In the case of manufacturing a device constituted by, it can be a small device.
[0014]
Furthermore, according to the transmission / reception control circuit of the present invention, the harmonic prevention filter for blocking the signal in the frequency band of the transmission signal of the first transmission / reception control method between the second GaAs switch circuit and the second transmission circuit. Since this signal is not transmitted to the second GaAs switch circuit even when the transmission signal of the first transmission / reception control method leaks to the second transmission circuit, the transmission / reception control circuit with good isolation is provided. can do.
[0015]
Still further, according to the transmission / reception control circuit of the present invention, the second transmission / reception communication system has two communication systems that are close to each other, thereby having two communication system transmission circuits. A transmission / reception control circuit that can use another transmission / reception communication system close to the frequency band of the transmission / reception signal of the transmission / reception communication system can be provided.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a circuit diagram of a transmission / reception control circuit according to an embodiment of the present invention. The transmission / reception control circuit shown in FIG. 1 schematically shows that a transmission / reception signal input / output to / from an antenna 1 includes a low-pass filter 2a and a high-pass filter. The connection is switched to the first and second transmission circuits and the reception circuit by the 2b, first and second GaAs switch circuits.
[0017]
In one embodiment of the present invention, for example, the first transmission / reception communication method is a GSM method (frequency band is 900 MHz band), and the second transmission / reception communication method is a DCS method (frequency is 1.8 GHz) higher than this. The transmission / reception control circuit is an example.
[0018]
The low-pass filter 2a and the high-pass filter 2b are circuits called diplexers. The diplexer is a circuit having a function of distributing transmission / reception signals of two transmission / reception communication systems so as not to interfere with each other. Specifically, in the received signal, the received signal of the first transmission / reception communication method input to the antenna 1 passes through the low-pass filter 2a, but is blocked by the high-pass filter 2b and does not pass. Further, the received signal of the second transmission / reception communication method input to the antenna 1 passes through the high-pass filter 2b, but is blocked by the low-pass filter 2a and does not pass.
[0019]
In the transmission signal, the transmission signal of the first transmission / reception communication scheme that has passed through the low-pass filter 2a is output from the antenna 1 without being blocked by the high-pass filter 2b. Further, the transmission signal of the second transmission / reception communication system that has passed through the high-pass filter 2b is output from the antenna 1 without being blocked by the low-pass filter 2a.
[0020]
Thus, each of the low-pass filter 2a and the high-pass filter 2b is required to have a function of passing a transmission / reception signal of one transmission / reception communication method and blocking a transmission / reception signal of the other transmission / reception communication method. As the filter component, a coaxial dielectric resonator or an LC resonant circuit in which an inductor or a capacitor is built in a dielectric multilayer substrate is used.
[0021]
The first GaAs switch circuit 3a switches the reception signal of the first transmission / reception communication system that has passed through the low-pass filter 2a to be output to the first reception circuit 4b, and is output from the first transmission circuit 4a. The transmission signal of the first transmission / reception communication system is switched so as to be output from the first transmission circuit 4a to the low-pass filter 2a.
[0022]
The second GaAs switch circuit 3b switches the reception signal of the second transmission / reception communication method that has passed through the high-pass filter 2b to be output to the second reception circuit 5b, and the second GaAs switch circuit 3b outputs the second transmission circuit output from the second transmission circuit. The transmission signal of the second transmission / reception communication method is switched so as to be output from the second transmission circuit 5a to the high-pass filter 2b.
[0023]
The first and second GaAs switch circuits 3b and 3b are composed of GaAs semiconductor elements that have good high-frequency characteristics and can realize low current consumption. The first and second transmission circuits 4a and 5a are configured by a power amplifier that amplifies the transmission signal, and the first and second reception circuits 4b and 5b are configured by a low noise amplifier that amplifies the reception signal. .
[0024]
The transmission / reception control circuit 10 configured as described above switches the transmission / reception signal of the first transmission / reception communication method to the antenna 1 and the first transmission circuit 4a or the first reception circuit 4b, and is higher than the first transmission / reception signal. The transmission / reception signal of the second transmission / reception communication system that performs transmission / reception in the frequency band is switched between the antenna 1 and the second transmission circuit 5a or the second reception circuit 5b.
[0025]
In the transmission / reception control circuit of the present embodiment, the low-pass filter 2a includes an antistatic circuit (hereinafter referred to as a high-pass filter, an inductor, a varistor, etc.) between the first transmission circuit 4a and the first reception circuit 4b. A first GaAs switch circuit 3a for switching the first transmission / reception signal to the first transmission circuit 4a or the first reception circuit 4b is connected via an antistatic filter 6). Accordingly, the first GaAs switch circuit 3a is protected by the antistatic filter 6 while being easily destroyed by static electricity, so that a transmission / reception control circuit resistant to static electricity can be obtained. In the present embodiment, the antistatic filter 6 is effective even with the same configuration as the high-pass filter 2b, and as another embodiment, for example, a band elimination filter of 100 to 600 MHz is also effective.
[0026]
At this time, since the second GaAs switch circuit 3b is prevented from being destroyed by static electricity being blocked by the high-pass filter 2b, it is not necessary to form a filter between the antenna 1 and the second GaAs switch circuit 3b. . Therefore, for example, compared to when an antistatic circuit is arranged between the antenna 1 and the diplexer, at least in the second transmission / reception communication system, a transmission / reception control circuit having excellent reception sensitivity can be obtained.
[0027]
In addition, if the first GaAs switch circuit 3a and the second GaAs switch circuit 3b are formed in the same GaAs element, the number of circuit components can be reduced. In the case of manufacturing a device composed of a circuit to be used, it can be a small device.
[0028]
Further, as shown in FIG. 2, a harmonic prevention filter for blocking signals in the frequency band of the transmission signal of the first transmission / reception control method between the second GaAs switch circuit 3b and the second transmission circuit 5a. 7 is arranged. Accordingly, the power amplifier constituting the transmission circuit becomes an integral part capable of outputting two transmission signals, and the isolation is deteriorated, so that the transmission signal of the first transmission / reception control method leaks to the second transmission circuit 5a. Even in this case, this signal is not transmitted to the second GaAs switch circuit 3b. That is, if a transmission signal of the first transmission / reception control method leaks to the second transmission circuit 5a and a harmonic is generated while passing through the second GaAs switch circuit 3b, for example, the second harmonic is passed through the high-pass filter 2b. Will pass. As a result, harmonics of the transmission signal of the first transmission / reception communication system pass through the high-pass filter 2b from the second GaAs switch circuit 3b and are output from the antenna 1, and this is transmitted as the transmission signal of the first transmission / reception control system. This is prevented by arranging a harmonic prevention filter 7 that blocks signals in the higher harmonic frequency band. Therefore, a transmission / reception control circuit with good isolation can be obtained.
[0029]
The harmonic prevention filter 7 may have a configuration in which a ground terminal is provided between the second GaAs switch circuit 3b and the second transmission circuit 5a and is disposed between the signal line and the ground terminal. In the present embodiment, the same configuration as that of the high-pass filter 2b is also effective.
[0030]
Furthermore, ... by having two communication methods. Furthermore, since the second transmission / reception communication method has two communication methods that are close to each other, a transmission / reception control circuit that can use the three transmission / reception communication methods can be provided. For example, as shown in FIG. 3, a transmission circuit is also used for a PCS system (frequency is 1.8 GHz band) that is close to a frequency band of a DCS system transmission / reception signal that is a communication system used in an embodiment of the present invention. It is possible to use the PCS system in addition to the GSM system and the DCS system by arranging a port shared with the DCS system and switching to the third receiving circuit 5c for the PCS system in addition to the second GaAs switch circuit 3b. A simple transmission / reception control circuit.
[0031]
【The invention's effect】
The transmission / reception control circuit of the present invention is a circuit using a GaAs switch circuit, and an antistatic filter is arranged between the low-pass filter and the GaAs switch circuit, so that reception sensitivity is good while removing static electricity. In addition, a transmission / reception control circuit with low current consumption can be provided.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a transmission / reception control circuit according to an embodiment of the present invention.
FIG. 2 is a circuit diagram of a transmission / reception control circuit according to another embodiment of the present invention.
FIG. 3 is a circuit diagram of a transmission / reception control circuit according to another embodiment of the present invention.
FIG. 4 is a circuit diagram of a conventional transmission / reception control circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Antenna 2a ... Low pass filter 2b ... High pass filter 3a ... First GaAs switch circuit 3b ... Second GaAs switch circuit 4a ... First First transmission circuit 5a ... second transmission circuit 5b ... second reception circuit 5c ... third reception circuit 6 ... static electricity Prevention circuit (antistatic filter)
7: Filter for preventing harmonics

Claims (4)

Connected to the antenna, the first and second transmission circuits, and the first and second reception circuits, the transmission / reception signal of the first transmission / reception communication method is transmitted to the antenna and the first transmission circuit or the first reception circuit. And the transmission / reception signal of the second transmission / reception communication system that performs transmission / reception operation in a higher frequency band than the transmission / reception signal of the first transmission / reception communication system is transmitted to the antenna and the second transmission circuit or the second transmission circuit. A transmission / reception control circuit for switching connection to a receiving circuit,
A low-pass filter through which a transmission / reception signal of the first transmission / reception communication scheme passes through the antenna and a signal in a higher frequency band than the transmission / reception signal of the first transmission / reception communication scheme is blocked; and the second transmission / reception communication scheme Is connected to a high-pass filter that passes through the transmission / reception signal of the second transmission / reception communication system and blocks a signal in a lower frequency band than the transmission / reception signal of the second transmission / reception communication method,
The low-pass filter transmits the transmission / reception signal of the first transmission / reception communication method to the first transmission circuit or the first transmission circuit or the first reception circuit via an antistatic circuit. A first GaAs switch circuit for switching to the first receiver circuit is connected;
Between the high-pass filter and the second transmission circuit and the second reception circuit, a second transmission / reception communication system transmission / reception signal is switched to the second transmission circuit or the second reception circuit. A transmission / reception control circuit, wherein two GaAs switch circuits are connected.   The transmission / reception control circuit according to claim 1, wherein the first GaAs switch circuit and the second GaAs switch circuit are formed in the same GaAs element.   Between the second GaAs switch circuit and the second transmission circuit, a harmonic prevention filter for blocking a signal in a harmonic frequency band of the transmission signal of the first transmission / reception control method is disposed. The transmission / reception control circuit according to claim 1 or 2, characterized in that:   4. The transmission / reception control circuit according to claim 1, wherein the second transmission / reception communication system includes two communication systems in which frequency bands of transmission / reception signals are close to each other.

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