JPH0537204A - Microwave filter - Google Patents

Abstract

PURPOSE:To realize the inexpensive microwave filter with small size and light weight without giving effect onto the electric performance. CONSTITUTION:Two open stubs 5a, 5b whose length is 1/8 wavelength with respect to a fundamental wave are sticked onto a strip line 1c of an output board of a solid-state power amplifier 2 in parallel with each other at an interval of 1/4 wavelength with respect to the fundamental wave. Then the open stubs 5a, 5b are in series resonance with respect to a 2nd harmonic wave to block the passing of the 2nd harmonic wave and the transmission loss by the microwave filter is minimized with respect to the fundamental wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave filter used in an output section of a microwave amplifier or the like.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing an output section of a conventional solid-state power amplifier. In the figure, 1a and 1b are strip lines for transmitting microwaves, 2 is a field effect transistor for power amplification provided between the strip lines 1a and 1b, and 3 is a waveguide mode for microwaves from the strip line 1b. A stripline-waveguide converter 4 for converting into a waveguide is a microwave filter constituted by a waveguide for removing the second harmonic of the mode-converted microwave.

Next, the operation will be described. The microwave input through the strip line 1a is input to the field effect transistor 2 and is amplified. At this time, due to the non-linear operation characteristic of the field-effect transistor 2, a harmonic wave of an integral multiple of the input frequency is generated, and this harmonic wave is output together with the fundamental wave of the same frequency as the input frequency. Of the above harmonics, the output level of the second harmonic is particularly high, so it is necessary to block this second harmonic.

The fundamental wave and the second harmonic wave output from the field effect transistor 2 are converted into the waveguide mode by the stripline-waveguide converter 3 through the stripline 1b. Next, the above-mentioned second harmonic wave is attenuated by the microwave filter 4 constituted by a waveguide.
As a technique similar to the above-mentioned conventional example, for example, JP-A-63-309002 and JP-A-59-21200.
There is one described in Japanese Patent Publication No.

[0005]

Since the output part of the conventional solid-state power amplifier is constructed as described above, the microwave filter 4 constituted by the waveguide is connected to the stripline-waveguide converter 3. Need to be installed after. Since the microwave filter 4 has a large external size and weight, the output part of the solid-state power amplifier becomes large. Also,
The microwave filter 4 has problems such as being expensive.

The present invention has been made in order to solve the above-mentioned problems and provides good electric characteristics and
The aim is to obtain a compact, lightweight, and inexpensive microwave filter.

[0007]

A microwave filter according to the invention of claim 1 is (2n + 1) λ / 8 (n = 0, 1,
Two open stubs having a length of 2, 3, ..., λ = wavelength of the fundamental wave) are provided at 1/4 λ intervals.

The microwave filter according to the invention of claim 2 is one in which two short stubs having a length of nλ / 4 (n = 1, 2, 3, ...) Are provided at an interval of 1 / 4λ. Is.

[0009]

In the first aspect of the invention, the two open stubs resonate in series with the second harmonic of the fundamental wave to attenuate the second harmonic.

The two short stubs according to the invention of claim 2 resonate in series with the second harmonic of the fundamental wave to attenuate the second harmonic.

[0011]

EXAMPLES Example 1. An embodiment of the invention of claim 1 will be described below with reference to the drawings. In FIG. 1, parts corresponding to those in FIG. In FIG. 1, 1c is a strip line having a length of 1/4 wavelength of the fundamental wave, and 5a and 5b are open stubs having a length of 1/8 wavelength of the fundamental wave, which are connected to both ends of the strip line 1c. There is. 6 is a microwave filter including a stripline 1c and open stubs 5a and 5b,
It is provided between the stripline 1b and the stripline-waveguide converter 3.

Next, the operation will be described. A fundamental wave that is a microwave is input to the field effect transistor 2 through the strip line 1a. The second harmonic generated due to the non-linear operation characteristic of the field effect transistor 2 is series-resonated by the open stubs 5a and 5b having a length of 1/8 wavelength of the fundamental wave, that is, 1/4 wavelength of the second harmonic. Therefore, the passage can be blocked.

Next, the fundamental wave is reflected to the field effect transistor 2 side by the two open stubs 5a and 5b, but is reflected by the open stub 5a by the strip line 1c having a quarter wavelength of the fundamental wave. Since the phase of the wave is opposite to the phase of the fundamental wave reflected by the open stub 5b, the reflected waves cancel each other out, and the microwave filter 6
Passage loss due to can be suppressed to a minimum.

In the first embodiment, the open stub 5 is used.
The length of a and 5b is set to 1/8 wavelength of the fundamental wave, but in general, (2n + 1) λ / 8 (where n = 0, 1, 2, 3, ...
, Λ = wavelength of the fundamental wave), series resonance for the second harmonic wave can be obtained. Further, the number of open stubs 5a and 5b is not limited to two, and an even number may be provided.

Example 2. FIG. 2 shows an embodiment of the invention of claim 2. In FIG. 2, 7a and 7b are n / 4 λ (n =
1, 2, 3, ..., λ = wavelength of input wave),
It is a short stub with its tip grounded. In this case as well, the second harmonic becomes series resonance due to the short stubs 7a and 7b as in the case where the open stub is pasted, and the second harmonic can be prevented from passing.

[0016]

As described above, according to the first aspect of the invention, two open stubs that are in series resonance with the second harmonic wave are arranged at 1/4 λ intervals. The waves can be effectively blocked, and the passage loss can be reduced. In addition, since only two stubs need to be attached at the time of manufacturing, there are advantages that the size and weight can be reduced and the cost can be reduced.

According to the second aspect of the present invention, since the two short stubs that are in series resonance with the second harmonic are arranged at 1/4 λ intervals, the second harmonic is effectively blocked. It is possible to reduce the passage loss. In addition, since only two stubs need to be attached and grounded at the time of manufacture, it is possible to achieve the effects of being small in size and weight and being inexpensive.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a microwave filter according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a microwave filter according to an embodiment of the present invention.

FIG. 3 is a configuration diagram showing an output section of a conventional solid-state power amplifier.

[Explanation of symbols]

5a, 5b open stub 6 microwave filter 7a, 7b Short stub 8 microwave filter

Claims (2)

[Claims] 1. A length that resonates in series with a second harmonic of a fundamental wave of an input microwave, and is arranged in the microwave transmission line with an interval of 1/4 wavelength of the fundamental wave. A microwave filter with at least two open stubs. 2. A length that resonates in series with the second harmonic of the fundamental wave of the input microwave and is arranged in the microwave transmission line with an interval of 1/4 wavelength of the fundamental wave. A microwave filter with at least two short stubs.