JPH0215127B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a microwave down converter used in satellite broadcast receivers and the like. recent years
With the development of microwave semiconductor devices such as GaAsFET, microwave frequency converters have been constructed using microwave integrated circuits, and SHF converters that combine this with input waveguides are about to be put into practical use. In this case, the SHF converter has a local oscillation circuit for frequency conversion, but
In the SHF converter, this local signal radiation from the local oscillation circuit may cause interference to other microwave equipment, so it is desirable to reduce it as much as possible. At the same time, it is also required to be strong against image interference. The present invention aims to provide a microwave frequency conversion device with less local signal radiation and good image disturbance characteristics by using a waveguide that exhibits a cutoff region for local frequencies and a passband for RF frequencies. It is also.

Configuration of conventional example and its problems A conventional example is shown below in FIGS. 1a and 1b. Figure 1a
1 is a rectangular waveguide (WR75), 3 is a microwave integrated circuit (MIC circuit), 4 and 5 are its center rectangular conductor and ground conductor, and ground conductor 5 is the H of waveguide 1.
The waveguide and the MIC circuit 3 are connected to each other by the ridge waveguide 2 . The RF signal from the waveguide 1 is sent to the MIC circuit 3 shown in Figure 1b.
It is converted into an IF signal by a microwave frequency conversion circuit configured as follows. In the MIC circuit 3 in Figure 1b,
The RF signal from waveguide 1 is transferred to the center conductor 4 of the MIC circuit.
and passes through a DC blocking capacitor 6.
It is added to the GaAsFET amplifier 7, passed through the DC blocking capacitor 11, and then the double balanced mixer circuit 12.
added to. At the same time, the oscillation output of the GaAsFET oscillator 16 stabilized by the dielectric resonator 17 is added to the double-balanced mixer circuit, and extracted from the IF signal 15 as a mixed output. Here, 9 and 18 are drain resistances, 19 is a source resistance, 20 is a termination resistor, 8 and 21 are drain application voltage terminals, 10 is a gate voltage terminal, 13,
14 is a mixer diode. Currently, as a microwave frequency converter, the input RF signal is in the 12 GHz band.
Local oscillation frequency 10.7GHz, IF frequency 1GHz band
Considering the SHF down converter, one of the SHF converter's performances is the radiation to the input side of the local frequency and the image interference characteristics, which must be strictly controlled for the coming era of satellite broadcasting.

However, in the conventional configuration, a part of the input of the MIC circuit is inside the waveguide, so the local oscillation output leaks into the input side of the MIC circuit directly into the waveguide without going through the rigid waveguide. It is possible that it radiates. In addition, generally the rectangular waveguide 1 is
WR75 is often used, in which case the waveguide
Since WR75 is in the passband near the local oscillation frequency of 10.7GHz, once it leaks into the waveguide, it is radiated directly into free space through the SHF antenna, causing interference. As a countermeasure against this, a bandpass filter or a local trap filter may be configured in the waveguide 1, but this causes insertion loss due to the insertion of the filter, deteriorating the NF of the converter, and the waveguide due to the filter configuration. The pipe length becomes considerably large, and the SHF converter as a whole becomes large. Furthermore, when a rigid circuit is used to couple the waveguide and the MIC circuit, in order to achieve broadband waveguide-MIC circuit conversion, a large number of stages of the rigid waveguide are required, which increases the overall length. In addition, since the waveguide 1 and the MIC circuit 3 are directly connected in terms of DC, a DC blocking capacitor 6 is always required at the first stage of the MIC circuit, and the insertion loss due to insertion of this capacitor is also a factor that deteriorates the NF of the converter. Become.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
The purpose of the present invention is to provide a microwave frequency conversion device that is extremely compact and easily mass-produced, with low local signal radiation, good image disturbance characteristics, and easy-to-configure broadband waveguide-to-MIC circuit conversion. .

Structure of the Invention The present invention uses a waveguide with the local oscillation frequency of a microwave frequency conversion circuit as a cutoff range and an RF band as a passband as an RF input section, short-circuits the other end of the waveguide, and A wave integrated circuit is fixed on the waveguide outer wall from the short-circuit surface of the waveguide along the input side, and a metal bar post is inserted from one end of the microwave integrated circuit near the short-circuit surface of the waveguide to complete the waveguide. By combining a microwave integrated circuit with a microwave integrated circuit, it is possible to provide a microwave frequency conversion device with a very compact configuration such as an SHF converter, which has low local signal radiation, good image blocking characteristics, and the like.

DESCRIPTION OF EMBODIMENTS FIGS. 2a and 2b show a microwave frequency conversion device in a first embodiment of the present invention. In FIGS. 2a and 2b, 22 is a rectangular waveguide having a cutoff region for local signals and a passband for RF signals, and its cross-sectional dimensions are a≈14 and b≈7. A metal post 12 is inserted from the microwave integrated circuit 3 into the vicinity of the short-circuited surface of the waveguide 22, and connects the waveguide 22 and the microwave integrated circuit 3. 24 is a cylindrical Teflon rod, which is inserted into the insertion hole 25 of the metal post drilled in the waveguide 22, and is inserted into the insertion hole 25 of the metal post 23 and the waveguide 22.
In addition to galvanically insulating the cables, a coaxial line is partially formed, and its impedance is approximately 50Ω. Reference numeral 26 denotes a disc hole provided concentrically with the metal post 23 drilled in the ground conductor surface of the metal post insertion part of the input section of the microwave integrated circuit, and its diameter is set to the waveguide hole for inserting a Teflon rod in 25 above. , and slightly larger than the width of the center conductor 4 of the microstrip line of the microwave integrated circuit 3. 29 and 30 were installed in the microwave integrated circuit.
RF amplifier circuit, 31 is a mixer circuit, 32 is a local oscillation circuit, 33 is a dielectric resonator for stabilizing oscillation, and 28 is a local oscillation frequency adjustment screw provided on the shield case 27 for the microwave integrated circuit. be.

According to the first embodiment of FIG. Broadband (for example, 11.7GHz to 12.7GHz) is achieved by making the diameter smaller than the diameter of the waveguide hole 25.
The signal is then supplied to the input terminal 4 of the microwave integrated circuit 3 after reducing the loss due to line conversion. this input
The RF signal is amplified by a two-stage RF amplifier circuit 29 and 30, and frequency converted by a mixer circuit 31 and a local oscillation circuit 32 (oscillation frequency approximately 10.7 GHz) to extract an IF signal. In such a configuration, even if the local oscillation signal is on the input side of the microwave integrated circuit, the waveguide 22 is cut off for the local signal, so the radiation from the waveguide is attenuated within the waveguide. It can be held down sufficiently. In addition, since the microwave integrated circuit 3 is arranged on the input side of the waveguide 3 rather than on the short-circuited side, it is possible to make the microwave integrated circuit 3 longer by the length of the microwave integrated circuit 3 without increasing the overall size, thereby reducing local signal leakage. waveguide 2
It is possible to achieve sufficient attenuation within 2 with a simple and compact configuration.

FIG. 2c shows an example of the configuration of the microwave integrated circuit 3. In the same figure, the signal from metal post 23 is
It is amplified by RF amplification stages 29 and 30 made of microwave semiconductors such as GaAsFET, and is supplied to the mixer circuit 31 via the image rejection filter 34.
It is mixed with the local oscillation signal from the local oscillator 32 stabilized by the dielectric resonator 33 and taken out as an IF output 44 . Here, 35 and 37
36, 38, 39 are the gate bias resistors and high-frequency choke circuits of the first-stage and next-stage amplifiers, 36, 38, and 39 are the drain resistors and high-frequency choke circuits of the first-stage and next-stage amplifiers and the oscillation circuit 32, and 40, 41
are the source resistance, high frequency choke circuit and gate termination resistance of the GaAsFET oscillator 32, respectively, and 4
2 and 43 are DC blocking circuits. In this figure, the RF amplifier circuit, mixer circuit, and local circuit are arranged almost in series and compactly configured on a rectangular board, making it easy to integrate with the waveguide and also providing power supply for gates, drains, etc. By making the supply terminal unidirectional, production efficiency is also improved.

FIG. 3 is a sectional view from the side and a sectional view from the waveguide input side of a microwave frequency conversion device showing a second embodiment of the present invention.

In the same figure, the same numbers as in FIG. 2 indicate the same parts, and the difference from the configuration in FIG. 2 is that a circular waveguide 45 is used instead of the rectangular waveguide 22, and its diameter C is approximately 16
mmφ to show a cutoff range for the local oscillation frequency of 10.7 GHz, and to pass the RF signal in the 12 GHz band, thereby reducing the local signal radiation as in Example 1 in Figure 2. In addition to providing excellent performance in suppression and image disturbance characteristics,
Since the waveguide 45 is circular, it is easier to mass-produce than a rectangular waveguide, and many circular waveguide output types are used as the primary radiator of antennas that support circularly polarized satellite broadcasting. Good matching for circular output antennas such as In FIG. 3, 46 is a shorting plate of the circular waveguide 45, and the distance from the shorting plate surface to the metal post 23 is between 1/4 and 1/8 of the tube wavelength λg. 45 and the microwave integrated circuit 3, and 47 and 48 are partition plates provided in the shield case 27 to isolate and shield between the RF amplifier circuits and between the RF amplifier circuit 30 and the mixer circuit 31. The coupling is made as small as possible, and the return of the local oscillation signal from the local oscillation circuit 32 to the RF stage is suppressed. Further, 49 is a screw for fixing the shorting plate 46, and 50 is a matching screw provided near the center of the shorting plate 46 to adjust the input impedance, which is the input impedance seen from the waveguide 45 due to variations in GaAsFET etc. of the microwave integrated circuit. It absorbs the variation in Reference numeral 51 denotes an intermediate frequency amplification circuit (IF amplification circuit) installed on the external side of the waveguide 45 almost perpendicularly to the microwave integrated circuit 3, and connects the IF output terminal 44 of the microwave integrated circuit and a short coaxial line 52 to the waveguide. They are connected at the shortest distance through the through hole 53 of the chassis, which allows for a connection with less loss, and allows for a very compact and compact configuration as a microwave frequency converter.

FIG. 4 shows a sectional view from the side of the microwave frequency converter according to the embodiment of FIG. 3 of the present invention and an input sectional view from the waveguide input side. In the same figure, the same numbers as in FIG. 3 indicate the same parts, and the difference from FIG. This makes it possible even with a rectangular waveguide. The circular-rectangular waveguide conversion circuit 54 includes a square rectangular waveguide 55 (a ₁ ≒ 15 mm, b ₁ ≒ 18 mm, d ₁ ≒ 12 mm) and an elongated elliptical waveguide 56 (arc radius R ≒ 10 mm, b ₂ ≒13
mm, d ₂ ≒ 8 mm) and rectangular waveguide 57 (WR75, a ₃ ≒
19.05 mm, b ₃ ≒ 9.5 mm) are connected in cascade, and by connecting this to the input of the circular waveguide 45 in Figure 3 as shown in Figure 4, the circular waveguide ( CR62) and rectangular waveguide (WR75) 12GHz tube RF
Waveguide conversion with low insertion loss can be performed over a wide signal band (e.g. 11.7 to 12.7 GHz), and circular waveguide input microwave frequency conversion equipment can be converted to rectangular waveguide input without deteriorating performance such as noise figure. It can be easily converted. Therefore, if such a small circular-to-rectangular conversion circuit 54 is attached and integrated with the circular waveguide input microwave frequency conversion device of FIG. 3 as shown in FIG. 4, local signal radiation can be suppressed. It is possible to easily configure a rectangular waveguide input microwave frequency converter by taking advantage of the features of the circular waveguide 45 and without degrading the original performance such as the noise figure. In general, many microwave parabolic antennas and the like have a rectangular waveguide output, so the antenna can be used satisfactorily for such antennas.

Effects of the Invention The microwave frequency conversion device of the present invention uses a waveguide with local signals as a cutoff region and RF signals as a passband, and a microstrip line is fixed on the outer wall of the waveguide. By short-circuiting one end of the waveguide and performing waveguide-to-microstrip line conversion using a metal post near the short-circuit, and configuring the microstrip line from the short-circuited side of the waveguide to the input side, local It is possible to obtain a compact microwave frequency conversion device with a very simple configuration, with little signal radiation and good image suppression characteristics, and its practical effects including mass production are very large.

[Brief explanation of drawings]

Figures 1a and 1b are perspective views of a conventional microwave frequency converter and a circuit diagram of a microwave integrated circuit, and Figures 2a, b, and c are of a microwave frequency converter according to a first embodiment of the present invention. The cross-sectional side view, front view and circuit diagram, Fig. 3 a, b, Fig. 4 a, b are the second,
FIG. 7 is a cross-sectional side view and a front view of a microwave frequency converter in a third embodiment. 3... Microwave integrated circuit, 22... Rectangular waveguide circuit, 23... Metal post, 45... Circular waveguide, 46... Short circuit plate, 51... IF amplification section, 54
...Circular-rectangular waveguide conversion section.

Claims (1)

[Claims] 1 One end of a circular waveguide with an RF signal as a passband and a local signal with a lower frequency than the RF signal as a cutoff region is short-circuited, and a microstrip line is placed on the outer wall of the waveguide. A metal rod is inserted from one end of the center conductor of the microstrip line near the short-circuited surface of the waveguide, and the diameter of the insertion hole of the metal rod provided in the ground conductor of the microstrip line is adjusted. is smaller than the diameter of the insertion hole of the metal rod in the circular waveguide, the microstrip line and the waveguide are coupled, and the RF signal from the waveguide is transferred to the microstrip line. A microwave frequency conversion device characterized in that frequency conversion is performed using a local oscillation circuit and a mixer circuit of a lower frequency than this RF signal configured in a loop line. 2. The microwave frequency conversion device according to claim 1, characterized in that the input side of the circular waveguide is equipped with a circular-rectangular waveguide device including an elongated waveguide and a square waveguide. .