JP2008054051A - Rf circuit and radio device incorporating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RF circuit which surge voltage countermeasures are applied to without increasing components, and also to provide a radio device incorporating the same. <P>SOLUTION: The RF circuit 100 comprises: a power amplification portion 10 for power-amplifying a transmission signal; a switching portion 20 for switching over between transmission and reception signals; and an RF line 30 for connecting the switching portion 20 and an antenna terminal 40. The RF circuit 100 also includes: a first varistor 13 connected between a connection node between the power amplification portion 10 and the switching portion 20 and ground; and a second varistor 32 connected between one of the ends of the RF line 30 and ground. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to surge voltage protection technology for preventing malfunction of a circuit due to surge voltage or destruction of a semiconductor element. More specifically, the present invention incorporates an RF circuit with a countermeasure against surge voltage by suppressing an increase in the number of parts of the RF circuit and the same. It relates to radio equipment.

  The final stage amplifier of the power amplifier that constitutes the final stage of the transmission circuit has the highest gain in the transmission circuit, and the higher the gain, the weaker it is against electrostatic surges. It has been subjected. Conventionally, as a countermeasure for surge voltage protection, protection by electronic parts such as a spark gap part or a neon tube, the shape of a printed circuit board or chassis, wiring, and protection by adding a sheet metal have been performed.

  FIG. 2 is a diagram showing a main part of the printed circuit board described in Patent Document 1. As shown in FIG. In FIG. 2, the patterns 1 and 2 and the solder portions 1a and 1b are formed by photolithography so that the crests t are in contact with each other so that the gap g is 0.15 mm. The patterns 1 and 2 are coated with an insulating material resist, and the solder portions 1a and 1b are soldered by a reflow soldering method to reduce impedance. Since static electricity has a low impedance pattern and a characteristic of escaping to a narrow gap, when static electricity falls to the pattern 1 side, it discharges to the grounded pattern 2 side that contacts the peak t of the solder part 1a, and the pattern 1 side Prevent block malfunction or semiconductor destruction.

By the way, when individual components for electrostatic discharge are mounted on a printed circuit board, the number of parts increases, the printed circuit board becomes larger, and the price increases. When dealing with the shape of the printed circuit board or chassis, there is a disadvantage that the cost increases due to an increase in design and processing time. Further, the measures by routing the wiring or adding the sheet metal involve a plurality of trial experiments in the determination of the layout of the wiring and the shape of the sheet metal, and there is a problem that the effect varies widely and it is difficult to reflect it in mass production.
JP-A-5-67851

  The present invention has been made to solve such problems, and an object of the present invention is to provide an RF circuit in which an increase in the number of RF circuit components is suppressed and a surge voltage countermeasure is taken, and a radio apparatus incorporating the RF circuit. There is to do.

  An RF circuit of the present invention is an RF circuit having a power amplifying unit that amplifies a transmission signal, a switching unit that switches transmission and reception signals, and an RF line that connects the switching unit and the antenna terminal. The RF line includes a varistor for surge voltage protection and impedance matching.

  The RF circuit of the present invention is connected in place of a capacitor for impedance matching connected between a connection node between the power amplification unit and the switching unit and the ground, surge voltage protection between the power amplification unit and the switching unit, and a connection node And a second varistor connected between the antenna terminal and the ground, for performing surge voltage protection between the RF line and the switching unit, and performing impedance matching of the RF line. It is characterized by.

  The radio of the present invention is characterized by incorporating the RF circuit.

  According to the present invention, by using a varistor for impedance matching of a final amplifier of an RF circuit, an increase in the number of components can be eliminated, and a surge voltage countermeasure that suppresses an increase in component costs and mounting costs can be taken. Moreover, by applying to the RF line, the transmission / reception changeover switch and the RF line can be protected from the surge voltage. Furthermore, by incorporating these into a radio device, it is possible to provide a radio device that is resistant to surge voltage.

  Embodiments of an RF circuit according to the present invention will be described with reference to the drawings. FIG. 1 is a circuit block diagram of an RF circuit according to the present invention. In FIG. 1, the RF circuit 100 includes a power amplification unit 10 that receives a transmission signal and amplifies the power, a switching unit 20 that switches a transmission / reception signal, and an RF line 30 that connects the switching unit 20 and the antenna terminal 40.

  The power amplifying unit 10 includes a final stage amplifier 11, a capacitor 12, and a varistor 13. The final stage amplifier 11 receives the transmission signal, amplifies the power to a predetermined level, and outputs it to the first contact 21-1 of the switching unit 20. Conventionally, a plurality of capacitors having different capacities are connected between the connection node between the output terminal of the final stage amplifier 11 and the first contact 21-1 of the transmission / reception selector switch 21 of the switching unit 20 and the ground for impedance matching. It was.

  For example, when handling a transmission signal of 400 to 520 MHz, two capacitors of 47 pF and 12 pF were used. By replacing this 12 pF capacitor with a varistor 15, both impedance matching and surge voltage countermeasures can be satisfied simultaneously. Since the capacitance of the varistor can be selected from an element with an arbitrary capacitance in the range of approximately 3 pF to 1000 pF, the capacitance of the varistor should be appropriately selected according to the impedance matching requirement according to the frequency of the transmission signal and the component cost of the varistor Can do.

  The switching unit 20 includes a transmission / reception changeover switch 21, and an output terminal of the final amplifier 11 is connected to the first contact 21-1, and a power-amplified transmission signal is input thereto. The second contact 21-2 is connected to an input terminal of a receiving circuit (not shown) and inputs a reception signal received by an antenna connected to the antenna terminal 40. The third contact 21-3 is connected to the antenna terminal 40 through the RF line 30. For this reason, the transmission / reception change-over switch 21 is controlled by the control signal and performs switch switching between sending a transmission signal to the antenna connected to the antenna terminal 40 or sending a reception signal received by the antenna to the reception circuit.

  The RF line 30 includes a low pass filter (LPF) 31 and a varistor 32. The low pass filter (LPF) 31 cuts harmonics of the transmission signal and sends a transmission signal having a predetermined frequency to the antenna connected to the antenna terminal 40. By the way, the RF line 30 is not always subjected to surge voltage protection measures by a conventional method. However, when a semiconductor switch using a GaAs substrate is used for the transmission / reception change-over switch 21, it is desirable to be protected from the property of being vulnerable to static electricity. For this reason, a varistor 32 that also serves as impedance matching at the antenna terminal is installed on the antenna terminal 40 side of the RF line 30 that is susceptible to external surge voltage. As a result, the transmission / reception selector switch 21 and the low-pass filter (LPF) 31 can be protected from the surge voltage.

  As described above, according to the present invention, by using a varistor for impedance matching of a final amplifier of an RF circuit, it is possible to eliminate the increase in the number of components and to take a countermeasure against surge voltage while suppressing an increase in component costs and mounting costs. It becomes. In addition, by similarly applying to the RF line, both the transmission / reception changeover switch and the LPF can be protected from the surge voltage. Furthermore, by incorporating these into a radio device, it is possible to provide a radio device that is resistant to surge voltage.

The circuit block diagram of RF circuit by this invention. The diagram which shows the principal part of the printed circuit board of patent document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power amplification part 11 Final stage amplifier 12 Capacitor 13 Varistor 20 Switching part 21 Transmission / reception changeover switch 21-1 1st contact 21-2 2nd contact 21-3 3rd contact 30 RF line 31 Low pass filter (LPF)
32 Varistor 40 Antenna terminal 100 RF circuit

Claims (3)

In an RF circuit having a power amplifying unit for amplifying a transmission signal, a switching unit for switching a transmission / reception signal, and an RF line connecting the switching unit and an antenna terminal,
The RF circuit, wherein the power amplification unit, the switching unit, and the RF line include a varistor for performing surge voltage protection and impedance matching. The power amplifying unit and the switching unit are connected in place of a capacitor for impedance matching connected between a connection node and the ground, surge voltage protection between the power amplifying unit and the switching unit, and impedance of the connection node A first varistor that performs matching;
An RF circuit comprising a second varistor connected between the antenna terminal and the ground and performing surge voltage protection between the RF line and the switching unit and impedance matching of the RF line.   A radio device incorporating the RF circuit according to claim 1.

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