JPH0457502A - High frequency transistor matching circuit - Google Patents

Abstract

PURPOSE:To adjust a capacitance of a capacitor equivalently and to obtain a capacitor with a large capacitance equivalently by connecting an input terminal of a transistor(TR) to ground through a two-terminal circuit and to an output terminal of an input main line. CONSTITUTION:A thin film capacitor 108 and a microstrip line are provided on a base 102 with a main line provided thereto. Then one terminal of a capacitor 108 is connected in series with one terminal of the microstrip line and the other terminal of the capacitor 108 is connected to a matched terminal of a TR 101 and the other terminal portion of the microstrip line is connected to ground while selecting its length. Thus, the capacitance is adjusted easily regardless of the matching circuit employing the capacitor 108 and the ground connection of the capacitor 108 is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a matching circuit for high-frequency transistors that can easily and inexpensively adjust the input and output impedances of transistors used in high-frequency, high-output amplifiers.

2. Description of the Related Art In recent years, the number of communication devices that use radio waves has increased, and the demand for high-frequency power amplification has also increased.

The input/output impedance of the high frequency transistor does not match the characteristic impedance (50 ohms) of the main line at -G. In order to efficiently amplify electrical signals, it is desirable that the input and output impedances of the transistor match the impedances of each input and output as much as possible, and that reflections at that point be minimized. In particular, the input/output impedance of high-frequency, high-output transistors is much lower than 50 ohms, so a low impedance element is usually inserted in parallel with the input/output main line to match the impedance. If we consider the microstrip line that is normally used, the open-ended microstrip line (
The impedance Zos of the oven stub) is Zos=-jcot (βL) =・
= (1) However, β-2π/λ λ is the wavelength on the main line at the frequency to be matched (wavelength within the pipe), and L is given by the length of the microstrip line.

Therefore, Zos becomes smaller as βL approaches π/2, that is, L approaches λ/4, and matching with the transistor can be achieved by selecting an appropriate value. A typical configuration of a conventional high frequency amplifier based on this method is shown in FIG. Fourth
In the figure, 101 is a field effect transistor (FET)
, 102 is an input matching circuit board, 104 is a main line composed of a microstrip line connected to the input terminal,
Reference numeral 105 indicates a main line consisting of a microstrip line connected to the output terminal. Reference numeral 106 indicates a wire connecting the transistor and the input matching circuit board. Reference numeral 107 indicates a wire connecting the transistor and the output matching circuit board. , 301 is an oven stub forming an input matching circuit, 302 is an oven stub forming an output matching circuit,
303304 is an island electrode for adjusting the length of the oven stub, and 305 and 306 are wires for connecting the oven stub and the adjustment pad. In this structure, the input matching circuit and the output matching circuit are adjusted by connecting an adjustment pad to the oven stub with a wire to substantially adjust the length of the oven stub.

As a further improvement of this method, one using a matching chip capacitor is known, and a typical structure thereof is shown in FIG. In the figure, 101 is a field effect transistor (FET), 401 is an input matching circuit board, 402 is an output matching circuit board, 104 is a main line composed of a microstrip line connected to an input terminal, and 105 is a main line connected to an output terminal. 403 is a chip capacitor for input impedance matching, 404 is a chip capacitor for output impedance matching, and the chip capacitors 403 and 404 are both connected to a pedestal whose lower electrodes are grounded. , the upper electrode is connected to the transistor and the main line microstrip board of the input/output matching circuit board by a wire. That is, 405 and 406 are wires connecting the transistor and the chip capacitor, and 407408 are wires connecting the chip capacitor and the main line microstrip line on the input/output matching circuit board. 4
09,410 is a band for adjusting input/output matching, 4
11 and 412 are wires for connecting the main line microstrip line and the adjustment band. In this structure, input/output matching is performed primarily by the inductance of the chip capacitor and the wire connecting it, and is supplementarily performed by connecting an adjustment pad with a wire on the input/output matching circuit board. There is.

FIG. 6 is a Smith chart showing the matching state, and FIG. 7 is an equivalent circuit diagram thereof.

Problems to be Solved by the Invention However, with the adjustment method shown in the first conventional example shown in FIG. 4, it is difficult to match high frequency, high output FETs with low impedance. That is, the impedance of the main line is generally 50 ohms, whereas the high frequency and high output F
The impedance of ET is generally several ohms or less than 1 ohm. Therefore, in order to match this, it is necessary to insert a capacitor with a considerably large capacitance between the main line and the ground. In order to achieve this with the open stub shown in the figure, as can be easily seen from equation (1), the length of the open stub should be very close to 1/4 wavelength of the frequency to be matched. There is a need. However, the impedance of the open stub is cot
sL, and in the vicinity of 1/4 wavelength, even if the length of the stub changes slightly, the value changes greatly, and actual adjustment is extremely difficult. Therefore, the first conventional method is not suitable for matching high frequency, high power FETs. Furthermore, in the case of the configuration described in the second conventional example shown in FIG. 5, in order to connect a large chip capacitor, the first
It is easier to match a high-frequency, high-output FET with lower impedance than in the conventional case, but it is difficult to finely adjust the capacitance value of the chip capacitor, so an open stub is installed on the input/output matching circuit board. It is necessary to finely adjust the alignment by forming an open stub and adjusting the length of this open stub. The difficulty of this adjustment is particularly great in the range β shown in the Smith chart of FIG.

In addition, matching capacitors are inserted between the main line and the ground, so in order to reduce signal transmission loss, losses such as dielectric loss must be extremely small, and as a result, they are inevitably expensive. Become. Furthermore, the number of man-hours required to mount the chip increases during manufacturing, and a separate part is required for mounting the chip, making it difficult to achieve small size and high integration, resulting in high manufacturing costs.

In this way, in a matching circuit using capacitors,
The first problem is that it is difficult to adjust the capacitance value of the capacitor, and the electrical loss is also large when a large capacitance value is used.

Furthermore, it is preferable in terms of the manufacturing process to create the matching circuit all on one board, but if the capacitor is provided outside the board with the main line as shown in Figure 5, the assembly and wiring will be complicated. . In order to install a capacitor on the board,
There is a second problem in that a ground conductor is required on the surface of the board, and a via hole structure is required to connect to the ground conductor on the back surface of the board.

The present invention solves the above problems, and although it is a matching circuit using capacitors, its capacitance can be easily adjusted.
Another object of the present invention is to provide a matching circuit whose capacitor can be easily grounded.

Means for Solving the Problems In order to achieve the above object, the present invention provides a first means for solving the problems, in which a thin film capacitor and a microstrip line are provided on a substrate provided with a main line, and one end of the capacitor is provided with a thin film capacitor and a microstrip line. is connected in series to one end of the microstrip line, the other end of the capacitor is connected to the matching terminal of the transistor, and the length of the other end of the microstrip line is selected and connected to ground.

In addition, the second means for solving the problem is to provide a thin film capacitor and an open-ended 1/4 wavelength microstrip line on a substrate provided with a main line, and connect one end of the capacitor in series to one end of the microstrip line. The other end of the capacitor is connected to the matching terminal of the transistor.

Operation The present invention has the above configuration, and the first means for solving the problem is that a series circuit of a thin film capacitor and a microstrip line operates as an actance, and the capacitance value can be adjusted by changing the ground connection position of the microstrip line. It becomes equivalent to a capacitor.

In addition, as a means for solving the second problem, the impedance of the open-ended 174-wavelength microstrip line becomes zero, and one end of the capacitor is isometrically connected to the ground.

EXAMPLE Hereinafter, a matching circuit for a high frequency transistor according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a top view showing the configuration of a matching circuit according to an embodiment of the first problem solving means of the present invention. As shown in the figure,
The input end of a field effect transistor (hereinafter referred to as FET) 101 is connected to the microstrip line 104 forming the main input line on the substrate 102 by a wire 106, and the output end of the transistor 101 connects to the main output line on the substrate 103. Wire 1 is connected to the constituting microstrip line 105.
Connected at 07. Thin film capacitor 10 on substrate 102
8 and a strip line 110, one end of which is connected to the capacitor 108, and the other end is connected to ground by a wire 117. capacitor 10
The other end of 8 is connected to the input end of the FET by a wire 112. Further, an island-shaped electrode 114 is provided near a position of a specific length from the terminal end of the strip line 104 of the substrate 02,
It is connected to a specific length of the string line by a wire 115. In addition, a thin film capacitor 1 is provided on the substrate 103.
09 and a strip line 111 are provided, one end of the strip line 111 is connected to the capacitor 109, and the other end is connected to ground by a wire 118. capacitor 1
The other end of 09 is connected to the output end of the FET by a wire 113. Further, an island-shaped electrode 114 is provided near a position at a specific length from the input end of the stripline 105, and connected to a position at a specific length of the stripline with a wire 116. Each of the above substrates uses a ceramic substrate such as alumina to reduce electrical loss, Cr-Au is used for the conductor material such as the main line, and thin film capacitors use silicon oxide etc. as the dielectric material. , consisting of a metal-dielectric-metal stacked structure. In addition, the transistor is made of GaAsF.
ET was used.

The operation of the matching circuit having the above configuration will be explained.

The matching circuit of this embodiment has a C-L-C configuration in order to cope with the case where the impedance of the transistor is low, and realizes a capacitor equivalent to a capacitor with a relatively large capacitance.
Further, the capacitance value can be adjusted.

To explain the input matching circuit, thin film capacitor 1
A strip line 110 is connected in series to 08 to form a two-terminal circuit. The electrical length of this stripline can be freely set by selecting the point at which the wire 117 is connected to the stripline, so that the impedance of the two-terminal circuit is variable. That is,
The impedance of the two-terminal circuit is Zin=1/jωc+, JωL−jZo・cot(β1
)...(2) where ω-2πf β-2π/λ f is the frequency to be matched, C is the capacitance of the thin film capacitor, L is the inductance of the connecting wire, and ZO is the characteristic impedance of the strip line. λ is the wavelength 1 within the substrate of the frequency to be matched, which is given by the length of the strip line. (2) As shown in Figure 2, by changing the length l of the strip line at the ground position, the impedance can be set almost arbitrarily, and the impedance Zi
By bringing n closer to zero, a capacitor with a large capacity can be realized.

Further, the island electrode 114 forms a small capacitance capacitor facing the ground plane on the back surface of the substrate, and is connected to a position of a specific length of the string line 104 by a wire 115.

Since the strip line portion of the specific length operates as an inductance, a C-L-C matching circuit is constructed.

FIG. 2 is a Smith chart showing the impedance matching state at the input end of the embodiment, and shows the state where the input impedance of several ohms is matched to the main line impedance of 50 ohms.

According to the matching circuit of one embodiment of the means for solving the first problem described above, the input terminal of the high-frequency transistor is connected to the output terminal of the input pressure line constituted by the first microstrip line installed on the substrate. In the matching circuit, a second microstrip line and a thin film capacitor are provided on the substrate, and the capacitor is connected in series to one end of the second microstrip line to form a two-terminal circuit. The input terminal of the transistor is connected to the ground in the two-terminal circuit and connected to the output end of the main input line, and the electrical length is changed by changing the ground connection terminal of the strip line. By adjusting and setting , the equivalent capacitance of the capacitor can be adjusted, and a large capacitance value can be realized with low loss at high frequencies.

FIG. 3 is a top view showing the configuration of a high frequency transistor matching circuit according to an embodiment of the second problem solving means of the present invention.

Description of common parts shown in FIG. 1 will be omitted. The component 201 of the input matching circuit is a 1/4 wavelength open-ended strip line.
Connect 8 to ground. Other operations are the same as in FIG. 1. Further, adjustment stubs 20 for electrical length adjustment are provided near the open ends of the strip lines 201 and 202.
3 is provided and connected to the P end of the line with a wire to set the electrical length of the line to exactly 1/4 wavelength. Detailed adjustments can be made by providing a plurality of such island-shaped electrodes and wiring wires in series or in parallel. Other operations are the same as those in FIG. 3.

As described above, according to the high-frequency transistor matching circuit according to an embodiment of the means for solving the second problem of the present invention, high-frequency In a matching circuit that connects input terminals of transistors with impedance matching, a second microstrip line with an open end 1/4 wavelength and a thin film capacitor are provided on the substrate, and the capacitor is connected to the second microstrip line. By forming a matching circuit of high-frequency transistors having a configuration in which the input terminal of the transistor is connected in series to the input terminal of the transistor, the input terminal of the transistor is connected to the input terminal of the capacitor, and the output terminal of the main input line is connected. The provided capacitor can be connected to ground (equivalently, without providing a via hole on the board).

The above description has been made regarding the matching circuit at the input end, but since the configuration and operation of the matching circuit at the output end are similar to those of the input end adjustment table, the description thereof will be omitted here.

It goes without saying that the means for solving the first problem and the means for solving the second problem described above can be used selectively at the input terminal and the output terminal of the transistor.

Effects of the invention As is clear from the above embodiments, the first
In a matching circuit that connects the input end of a high-frequency transistor to the output end of a main input line consisting of a microstrip line with impedance matching, a second
A microstrip line and a thin film capacitor are provided, and the capacitor is connected in series to one end of the second microstrip line to form a two-terminal circuit, and the input terminal of the transistor is grounded by the second child circuit. By using a matching circuit of high frequency transistors having a configuration in which the output terminal C of the input ball wire is connected to There are effects that can be obtained.

In addition, in a matching circuit that connects the input end of a high-frequency transistor to the output end of the input main line constituted by the first microstrino pline provided on the substrate with impedance matching, the termination is open 1/4 on the substrate. A second microstrip line with a wavelength and a thin film capacitor are provided, the capacitor is connected in series to the input end of the second microstrip line, the input end of the transistor is connected to the input end of the capacitor, and the By using a matching circuit of high frequency transistors connected to the output end of the main input line, the capacitor can be connected to the ground equivalently to the substrate without providing a via hole structure on the substrate.

[Brief explanation of the drawing]

FIG. 1 is a top view showing the configuration of a high-frequency transistor matching circuit according to an embodiment of the means for solving the first problem of the present invention, and FIG.
The figure is a Smith chart showing the matching state of the input end of the embodiment of FIG. Figure 4 is a top view showing the configuration of a matching circuit for a conventional high frequency transistor, Figure 5 is a top view showing the configuration of a matching circuit for another conventional high frequency transistor, and Figure 6 is a matching state of the circuit in Figure 5. 7 is an equivalent circuit diagram of the circuit shown in FIG. 5. 101...High frequency transistor, 102...
... Board, 104 ... Input main line, 106.
... wire (wire connecting the input end of the transistor to the output end of the input main line), 108 ... thin film capacitor, 110 ... second microstrip line, 112 ... ...Wire (wire L117 that connects the capacitor to the input terminal of the transistor...
...Wire (wire that connects one end of the second microstrip line to ground). Name of agent Patent attorney Shigetaka Awano 1 person 1 image base mV transcription 1 version input 1 contribution (fund) ; Pancreas) Interchange■Kuake] 51 Dragon] J diagonal 7 Ohuhui 7Dsu), Richo 7° lie ν '7k (IJ Te'Q6C'i: 29n included 174 +=(
nlTi Quit T) Waima I'X" 26 My 70s L'le, Goline Lee Yu) Ryo-su 1:5Nls Easy Y) Fig.

Claims (5)

[Claims] (1) In a matching circuit that connects the input end of a high-frequency transistor to the output end of a main input line consisting of a first microstrip line provided on a substrate with impedance matching, a second microstrip line is provided on the substrate. a line and a thin film capacitor, and connect the capacitor to the second
Connect in series to one end of the microstrip line.
A terminal circuit is configured, and the input terminal of the transistor is connected to the second terminal circuit.
A matching circuit of high frequency transistors having a configuration in which the terminal circuit is connected to ground and also connected to the output end of the main input line. (2) In a matching circuit in which the output end of a high-frequency transistor is impedance matched and connected to the input end of an output main line consisting of a first microstrip line provided on a substrate, a second microstrip line is provided on the substrate. a line and a thin film capacitor, and connect the capacitor to the second
Connect in series to one end of the microstrip line.
A terminal circuit is configured, and the output terminal of the transistor is connected to the second terminal.
A matching circuit of high frequency transistors having a configuration in which a terminal circuit is connected to ground and also connected to an input end of the main output line. (3) In a matching circuit in which the input end of a high-frequency transistor is impedance matched and connected to the output end of the input main line constituted by a first microstrip line provided on the board, the termination is open 1/4 on the board. A second microstrip line with a wavelength and a thin film capacitor are provided, the capacitor is connected in series to the input end of the second microstrip line, the input end of the transistor is connected to the input end of the capacitor, and the A matching circuit of high-frequency transistors connected to the output end of the main input line. (4) In a matching circuit in which the output end of a high-frequency transistor is impedance matched and connected to the input end of an output main line constituted by a first microstrip line provided on a substrate, 1/4 of the termination is open on the substrate. A second microstrip line of wavelength and a thin film capacitor are provided, the capacitor is connected in series to the input end of the second microstrip line, the output end of the transistor is connected to the input end of the capacitor, and the A matching circuit of high-frequency transistors connected to the input end of the main output line. (5) The high-frequency transistor matching circuit according to claim (3) or (4), further comprising an island-like electrode for adjusting the length of the tube near the open end of the open-ended quarter-wavelength strip line.