JPH02309801A - High frequency output circuit - Google Patents

Abstract

PURPOSE:To constitute a high pass filter and a matching circuit with less space and to attain matching without revising a pattern even when a different kind of coaxial connector is employed by forming part of a pattern inductance comprising a microstrip line with a ladder pattern and decreasing the entire length of the pattern inductance more than 1/4 of the wavelength of the operating frequency. CONSTITUTION:A microstrip line 2 placed between an output of a high frequency amplifier 1 and a coaxial connector 4 is cut off by a chip capacitor 3 in terms of direct current and part of a pattern inductance 5 comprising the microstrip line whose one terminal connects to the interrupted microstrip line 2 and whose other terminal connects to ground is formed by a ladder pattern 6 and the entire length of the pattern inductance is shorter than 1/4 of the wavelength of the operating frequency. Thus, the high frequency output circuit is constituted with less space without need of the matching circuit and even when a different kind of coaxial connector is employed, it is not required to change the pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an output circuit of a high frequency amplifier using a microstrip line.

[Prior Art] Conventionally, in a circuit that uses a microstrip line 2 to extract the output of a high-frequency amplifier using a coaxial connector, impedance matching between the microstrip line 2 and the coaxial connector 4 is carried out as shown in the conventional example shown in FIG. In order to achieve this, a matching circuit 10 was provided at the output section of the high frequency amplifier 1.

In addition, most high-frequency amplifiers have sufficient gain even at the low frequencies used, so as shown in Figure 10 (a), the noise level remains high even at low frequencies.
In order to adversely affect the noise performance, it is often used to add a bypass filter to the output section of the high frequency amplifier 1, as shown in FIG. 9, consisting of a capacitor 3.3 and a pattern inductance 5. An example of the characteristics of this bypass filter is shown in FIG.
d) shows the noise level when using a filter.

[Problems to be Solved by the Invention] By the way, in a filter using the pattern inductance 5 which is constructed from a microstrip line as described above and whose one end is grounded, the length l of this pattern inductance 5 is
is generally about 1/4 of the line wavelength λg.

This means that the impedance Z of the microstrip line whose tip is short-circuited is Z = j Z otan (2z/
When l becomes λg/4, Z-■
Therefore, it is designed to have almost no effect on the frequency that is desired to be passed at the connection point to the main signal line (point a in FIG. 9). However, at a frequency of about 10 GHz, λ
f! The length of λ2/4 is about 5 cm, but if you try to use it in an IGHz circuit, for example, the output part of a BS converter for satellite broadcasting, it will be very long, with about 50 pairs of λ2/4. Required large board space. Furthermore, the matching circuit 10 between the output section and the coaxial connector 4 is closely related to the wavelength, and has the drawback of requiring a very large circuit.

Furthermore, there is a problem in that the matching circuit 10 must be changed each time there is a change in the shape of the coaxial connector 4 or the method of attachment.

The present invention was made in view of the above-mentioned problems, and its purpose is to configure a bypass filter and a matching circuit in a small amount of space, and to do so without changing the pattern even if the coaxial connector is changed. An object of the present invention is to provide a high frequency output circuit that can perform matching.

[Means for Solving the Problems] The present invention provides a high frequency output circuit in which a coaxial connector is connected to the output of a high frequency amplifier whose basic configuration is a microstrip line on a dielectric substrate. A chip capacitor is used to cut off the microstrip line in between, and one end is connected to the cut-off microstrip line, and the other end is grounded.The part of the pattern inductance formed by the microstrip line is formed in a ladder pattern. , and the total length of the pattern inductance is shorter than 174 wavelengths of the frequency used.

[Function] According to the present invention, since the total length of the pattern inductance is made shorter than 174 wavelengths of the frequency used, the impedance at the connection point of the pattern inductance is not infinite, so the frequency range to be passed is Impedance mismatch also occurs. On the other hand, microstrip lines have mismatches at the connection points where they are connected to coaxial connectors. This mismatch can be offset by adjusting the length of the ladder pattern, eliminating the need to provide an output matching circuit. In addition, since the signal passes through the shortest path in the ladder pattern, by cutting off the remaining parts of the ladder pattern, the length of the pattern inductance can be varied, and even if the coaxial connector to be connected is changed, the pattern This eliminates the need to change the .

[Example] The present invention will be explained below with reference to Examples.

FIG. 1 shows the circuit configuration of an embodiment of the present invention, in which a signal amplified by a high frequency amplifier 1 is transmitted to a microstrip line 2 and outputted via a coaxial connector 4 at the output section. Here, the microstrip line 2 has two chip capacitors 3 interposed on the way, and the microstrip line between the two chip capacitors 3 connects a pattern inductance 5 whose part is a ladder pattern 6. Grounded.

The total length of the pattern inductance 5 including the ladder pattern 6 is made shorter than 174 of the line wavelength λ2 of the frequency used, making it possible to omit the matching circuit between the microstrip line 2 and the coaxial connector 4. In other words, when the length of the pattern inductance 5 is λg/4, the impedance at point a in Figure 1 becomes infinite, and it has no effect on the frequency used.By shortening the length, the impedance can be reduced. If a mismatch occurs, the mismatch between the microstrip line 2 and the coaxial connector 4 is canceled out, making it possible to omit the above-mentioned matching circuit.

Further, in the ladder pattern 6, the signal passes through the shortest line, so by cutting a part of the ladder pattern 6, the total length of the pattern inductance 5 can be changed, and the matching conditions can be varied. Therefore, even if the coaxial connector 4 is changed, impedance matching can be achieved by cutting the ladder pattern 6 at a good position without changing the pattern.

Figure 2 shows the mounting state of an embodiment applied to the output section of a BS converter for satellite broadcasting.In this embodiment, gain adjustment is performed with a π-type attenuator 8, and a coaxial connector
uses an F type connector (C12 type or C15 type).

Here, the pattern inductance 5 including the ladder pattern 6
The total length is approximately 15 m at the shortest length and approximately 301 m at the maximum length, and the wavelength λg in this frequency band is 174 m.
It is sufficiently shorter than about m.

In the embodiment shown in FIG. 2, the length shown in FIG. 3 is 20 m+s, the core diameter is φ1.3+IIm, and the outer diameter is φ2. When using a coaxial connector 4 that uses a lead wire of 0 mm, the lateral remaining portion of the ladder pattern 6 closest to the grounding point is marked with × in Fig. 4.
5th by cutting to obtain the optimum length as shown in
We were able to obtain good return loss characteristics as shown in the figure.

In addition, in the embodiment shown in FIG. 2, the length shown in FIG. 6 is 201 mm, the core diameter is φ1.31, and the outer diameter is φ2. When using a coaxial connector 4 that uses a lead wire of 0.0 mm, the two lateral remaining parts closest to the grounding point of the ladder pattern 6 are cut as shown by the x in Fig. 7 to obtain the optimum length. As a result, good return loss characteristics as shown in FIG. 8 could be obtained.

[Effects of the Invention] According to the present invention, the length of the pattern inductance of the bypass filter used in the high frequency amplifier makes it possible to match it with the coaxial connector of the output section, which eliminates the need to provide a matching circuit. Moreover, since the total length of the pattern inductance is shorter than 174 wavelengths of the frequency used, a high-frequency output circuit can be constructed in a small amount of space.Furthermore, the length of the pattern inductance can be varied by cutting off the horizontal remaining portion of the ladder pattern. This has the effect that even if the coaxial connector to be connected is changed, there is no need to change the pattern.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of an embodiment of the present invention, Fig. 2 is a partially omitted mounting state diagram of another embodiment of the present invention, Fig. 3 is an enlarged side view of the coaxial connector used in the above, and Fig. 4 The figure is an explanatory view of the use of the ladder inductance corresponding to the coaxial connector shown in Fig. 3 of the same above, Fig. 5 is an explanatory view of the characteristics of the same as the above, Fig. 6 is an enlarged side view of the coaxial connector used in the same as the above, and Fig. 7 is the same as the above. An explanatory diagram of the use of ladder inductance corresponding to the coaxial connector in Figure 6,
FIG. 8 is a characteristic explanatory diagram of the same as above, FIG. 9 is a circuit configuration diagram of a conventional example, and FIG. 10 is an explanatory diagram of the same. 1 is a high frequency amplifier, 2 is a microstrip line, 3 is a chip capacitor, 4 is a coaxial connector, 5 is a pattern inductance, and 6 is a ladder pattern. Agent Patent Attorney Ishi 1) Chief 7 Figure 2 Figure 3 Figure 5 Figure 6 Figure 8 Procedure amendment written on his own initiative) July 28, 1999

Claims (1)

[Claims] (1) In a high frequency output circuit in which a coaxial connector is connected to the output of a high frequency amplifier whose basic configuration is a microstrip line on a dielectric substrate, the microstrip line between the output of the high frequency amplifier and the coaxial connector is connected using a chip capacitor. A portion of the pattern inductance is formed by a microstrip line that is DC cut off, one end is connected to this cut off microstrip line, and the other end is grounded, and the entire length of the pattern inductance is set at the operating frequency. A high frequency output circuit characterized in that the wavelength is shorter than 1/4 of the wavelength of the high frequency output circuit.