JPH04290003A - Frequency converter - Google Patents

Abstract

PURPOSE:To realize the frequency converter with a small conversion loss and a low spurious characteristic by solving a problem such that a conversion loss of the frequency converter for a transmission system at a microwave band is high and a level of a spurious signal is high due to leakage of a local oscillation signal or the like. CONSTITUTION:A mixer 4, an input low pass filter 3, an input band pass filter 9, and an output band pass filter 6 are formed on a dielectric board contained in a metallic case 13 are formed by a microstrip line. The conversion loss is reduced by connecting the high pass filter 17 comprising a rectangular waveguide in cascade to the rear side of the metallic case 13 and the frequency converter of a low spurious characteristic is realized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency converter used in a transmission system of a data communication device using a microwave band.

0002

[Prior Art] Figures 7 to 9 regarding conventional frequency converters
Explain using. Fig. 7 is a block diagram showing the configuration of a conventional frequency converter, Fig. 8 is a plan view showing the implementation state of the frequency converter shown in Fig. 7, and Fig. 9 shows an example of a transmission system using the same frequency converter. FIG.

In FIGS. 7, 8, and 9, 1 is an intermediate frequency signal input terminal, 2 is an amplifier, 3 is an input low-pass filter, 4 is a mixer, 5 is a local signal input terminal, 6 is an output band-pass filter, 8 is an output terminal, 9 is an input bandpass filter, 10 is a dielectric substrate, 11 is a microstrip line, 12 is a half-wavelength resonator, and 13 is a metal case. Further, the input low-pass filter 3, mixer 4, input band-pass filter 9, and output band-pass filter 6 are each constructed by a microstrip line 11 on a dielectric substrate 10, and the output band-pass filter 6 and the input band-pass filter 9 was constructed using a half-wavelength resonator 12.

The operation of the conventional frequency converter configured as described above will be explained below.

An intermediate frequency signal (Fi) input to an intermediate frequency signal input terminal 1 is amplified by an amplifier 2, passes through an input low-pass filter 3, and is input to a mixer 4. In the mixer 4, the local oscillator signal (Fl) input from the local oscillator signal input terminal 5
As a result, two microwave signals (Fl±
Fi) occurs. These two microwave signals (Fl±
One microwave signal (Fl+Fi) is extracted from the microwave signal (Fl+Fi) by the output bandpass filter 6 and output to the output terminal 8.

FIG. 9 shows an example of a transmission system using the frequency converter shown in FIGS. 7 and 8, in which the microwave signal (
The frequency converter 13 and the microwave power amplifier 26 are connected to the coaxial cable 28.
It was connected and configured.

[0007]

[Problems to be Solved by the Invention] However, in the conventional configuration described above, there is a problem in that the microwave signal (Fl-Fi) and the local oscillator signal (Fl), which are unnecessary signals generated in the mixer 4, leak to the output terminal 8. Become. Particularly in the case of frequency converters used in transmission systems, the local oscillator signal (Fl) is a microwave signal (Fl).
In the case of the output bandpass filter 6 using the microstrip line 11, the Q value is low and the local oscillator signal (Fl) cannot be sufficiently attenuated, resulting in deterioration of spurious characteristics. Ta.

To solve this problem, if the number of stages of the input bandpass filter 9 is increased in order to obtain a desired amount of attenuation, the insertion loss increases and the level of the intermediate frequency signal (Fi) input to the mixer 4 becomes high. As a result, spurious signals are generated due to distortion in the mixer 4.

Furthermore, as the coaxial cable 28 for connecting the frequency converter 13 and the microwave power amplifier 26 becomes longer, the insertion loss increases.
In order to increase the gain of 6, it is necessary to increase the number of transistors, resulting in an increase in the size and cost of the microwave power amplifier 26.

The present invention solves the above-mentioned conventional problems, and aims to provide a frequency converter with low conversion loss and low spurious characteristics, and also to provide a small and inexpensive transmission system. be.

[0011]

[Means for Solving the Problem] In order to solve this problem, the frequency converter of the present invention includes a mixer, an input low-pass filter, an input band-pass filter, and an output band-pass filter on a dielectric substrate using microstrip lines. A high-pass filter made of a rectangular waveguide is connected to the output of the output band-pass filter, and a metal cover is placed on the open surface of a cavity provided on the back surface of a metal case housing a dielectric substrate. It consists of a rectangular waveguide formed by combining, a microstrip waveguide conversion section that connects the rectangular waveguide and the output bandpass filter, and a waveguide coaxial conversion section that also connects the output terminal. It is something.

0012

[Operation] By creating a high-pass filter configured using the cutoff frequency of a rectangular waveguide, a filter with small insertion loss can be constructed because the amount of attenuation of spurious signals is greater than that of a band-pass filter using a microstrip line. Conversion loss can be reduced.

Furthermore, since the rectangular waveguide is provided on the back surface of the metal case, the output terminal of the rectangular waveguide can be placed near the input terminal of the microwave power amplifier.
Rectangular waveguides can shorten coaxial cables, and at the same time, compared to coaxial cables, rectangular waveguides have lower insertion loss, and can reduce connection losses between frequency converters and microwave power amplifiers, increasing the gain of microwave power amplifiers. There is no need to raise it.

Therefore, it is possible to construct a frequency converter with low conversion loss and low spurious characteristics, and it is also possible to construct a small and inexpensive transmission system.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram showing the configuration of a frequency converter according to the present invention, FIG. 2 is a plan view showing the mounting state of FIG. 1, FIG. 3 is a bottom view showing the back side of FIG. 2, and FIG. 5 is a cross-sectional view of the A-A section, and B in FIG. 4.
FIG. 6 is a plan view showing an example of a transmission system using this embodiment.

1 to 6, 1 is an intermediate frequency signal input terminal, 2 is an amplifier, 3 is an input low-pass filter, and 4 is an intermediate frequency signal input terminal.
is a mixer, 5 is a local signal input terminal, 6 is an output band pass filter, 7 is a high pass filter, 8 is an output terminal, 9 is an input band pass filter, 10 is a dielectric substrate, 11 is a microstrip line, 12 is a half A wavelength resonator, 13 is a metal case, 14 is a hollow part on the back side of the metal case 13, 1
5 is a metal cover, 16 is a metal screw, 17 is a rectangular waveguide,
18 is a microstrip waveguide converter, 19 is a waveguide coaxial converter, 20 is a metal probe, and 21 is a metal case 1.
3 is a hole drilled, 22 is a ground conductor, 23 is a microstrip line of the output part of the output bandpass filter 6,
24 is a protrusion provided on the upper part of the metal probe 20;
25 is solder, 26 is a microwave power amplifier, 27 is an input terminal, 28 is a coaxial cable, and 29 is an output waveguide. In this embodiment, intermediate frequency signal input terminal 1, local signal input Terminal 5 and output terminal 8 are constructed using SMA connectors.

The structure and operation of the frequency converter according to this embodiment will be explained below.

As shown in FIG. 1, the intermediate frequency signal (Fi=1070MHz
) is amplified by an amplifier 2, passes through an input low-pass filter 3, and is input to a mixer 4. The mixer 4 receives a local oscillator signal (Fl=12.93-13.
43 GHz), two microwave signals (Fl + Fi = 14 to 14.5 GHz, Fl - Fi
= 11.86 to 12.36 GHz) is generated. This 2
One microwave signal (Fl+Fi=14 to 14.5 GHz) is extracted from the two microwave signals (Fl±Fi) by an output bandpass filter 6 and a highpass filter 7, and outputted to an output terminal 8.

In addition, as shown in FIGS. 2 and 4, an input low-pass filter 3, a mixer 4, an input band-pass filter 9,
The output bandpass filter 6 is composed of a microstrip line 11 on a dielectric substrate 10 (in this embodiment, dielectric constant = 2.6, thickness = 0.8 mm) whose back surface is a ground conductor 22 on the entire surface, and the output band The pass filter 6 and the input bandpass filter 9 are constructed using a half-wavelength resonator 12, and a dielectric substrate 10 is housed in a metal case 13.

Furthermore, the high-pass filter 7 shown in FIG.
As shown in FIGS. 3 and 4, a rectangular waveguide 17 and a rectangular waveguide 17 are connected by fixing a metal cover 15 to the open surface of a cavity 14 provided on the back surface of a metal case 13 using a plurality of screws 16. A microstrip waveguide conversion section 18 that connects the wave tube 17 and the output bandpass filter 6, and a waveguide coaxial conversion section 1 that also connects the rectangular waveguide 17 and the output terminal 8.
9 is provided on the metal cover 15, and the rectangular waveguide 17 has a width of W=11.95 mm, H=5.4 mm,
Formed with L=150mm, cut-off frequency 13.6GHz
That is.

As shown in FIG. 5, the thickness (h1) of the bottom surface of the metal case 13 and the thickness (h2) of the metal cover 15 are
) is h1=h2=4mm. Further, the four corner portions indicated by the symbol a in FIG. 3 do not need to be at right angles, and in this embodiment, the radius is less than R-4 mm. Therefore, the rectangular waveguide 17
can be made integrally with the metal case 13 using a mold.

In addition, as shown in FIGS. 4 and 5, holes 21 into which metal probes 20 (diameter=1.3 mm) of the microstrip waveguide conversion section 18 and the waveguide coaxial conversion section 19 are inserted are provided.
The diameter of the metal probe 20 is 4.0 mm, and a spacer (for example, a Teflon spacer) for holding the metal probe 20 is not used. The microstrip waveguide converter 18 is connected to the dielectric substrate 1
A part of the ground conductor 22 is removed to have the same circular shape as the hole 21 provided in the metal case 13 of No. It has a circular shape.

The metal probe 20 has a dielectric substrate 10
It is inserted into the rectangular waveguide 17 from the side. This metal probe 20 has a structure in which a circular protrusion 24 is provided on the upper side to make the length (2 mm) of the metal probe 20 inserted into the rectangular waveguide 17 constant, so that variations do not occur during mass production. . Furthermore, in the waveguide coaxial converter 19 as well, the length of the metal probe 20 inserted into the rectangular waveguide 17 is set to 2 mm.

FIG. 6 shows an example of a transmission system using the frequency converter of this embodiment, in which the output terminal 8 of the frequency converter is connected to the Since it can be placed close to the input terminal 27 of the wave power amplifier 26 and the length of the coaxial cable 28 can be shortened, connection loss can be reduced.

Further, as shown in FIG. 3, in this embodiment, the rectangular waveguide 17 is used without being folded, but it goes without saying that it may be arranged folded using a vent.

[0026]

As described above, the frequency converter according to the present invention is a high-pass filter that utilizes the cutoff frequency of a rectangular waveguide, and has a greater attenuation of spurious signals than a band-pass filter using a microstrip line. A filter with low insertion loss can be constructed, and conversion loss can be reduced.

Furthermore, since the rectangular waveguide is provided on the back surface of the metal case, the output terminal of the rectangular waveguide can be placed near the input terminal of the microwave power amplifier.
Rectangular waveguides can shorten coaxial cables, and at the same time, compared to coaxial cables, rectangular waveguides have lower insertion loss, and can reduce connection losses between frequency converters and microwave power amplifiers, increasing the gain of microwave power amplifiers. There is no need to raise it.

Therefore, the conversion loss is small, spurious characteristics are low, and the rectangular waveguide can be molded integrally with the metal case, making it possible to create a frequency converter with less variation in characteristics during mass production, as well as being small and inexpensive. It is possible to construct a transmission system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a frequency converter according to an embodiment of the present invention.

[Figure 2] Plan view showing the same mounting state

[Figure 3] Bottom view showing the back side of Figure 2

[Figure 4] Cross-sectional view of section A-A in Figure 3

[Fig. 5] Cross-sectional view of section B in Fig. 4 enlarged

[Fig. 6] A plan view showing an example of a transmission system using this embodiment.

[Figure 7] Block diagram showing the configuration of a conventional frequency converter

[Figure 8] Plan view showing the same mounting state

[Fig. 9] A plan view showing an example of a transmission system using a conventional frequency converter.

[Explanation of symbols]

1 Intermediate frequency signal input terminal 2 Amplifier 3 Input low-pass filter 4 Mixer 5 Local oscillation signal input terminal 6 Output band-pass filter 7 High-pass filter 8 Output terminal 9 Input band-pass filter 10 Dielectric substrate 11 Microstrip line 12 Half-wave resonator 13 Metal case 14 Hollow section 15 on the back of the metal case Metal cover 16 Metal screw 17 Rectangular waveguide 18 Microstrip waveguide converter 19 Waveguide coaxial converter 20 Metal probe 21 Hole drilled in the metal case 22 Ground conductor 23 Microstrip line 24 at the output part of the output bandpass filter Projection part 25 provided on the top of the metal probe
Solder 26 Microwave power amplifier 27 Input terminal 28 Coaxial cable 29 Output waveguide

Claims (2)

[Claims] 1. A mixer, an input low-pass filter, an input band-pass filter, and an output band-pass filter are formed on a dielectric substrate using microstrip lines, and the output of the output band-pass filter is connected to a high-pass filter using a rectangular waveguide. Frequency converter with cascaded filters. 2. A rectangular waveguide formed by bonding a metal cover to the open surface of a cavity provided on the back side of a metal case in which a high-pass filter houses a dielectric substrate, and an output bandpass between the rectangular waveguide and the rectangular waveguide. 2. The frequency converter according to claim 1, comprising a microstrip waveguide converter connected to the filter, and a waveguide coaxial converter connected to the output terminal.