JPS6229203A - Microwave receiver - Google Patents

Abstract

PURPOSE:To obtain a low noise device by making the cut-off frequency of an input waveguide from that of an output waveguide so as to suppress spurious radiation of a local signal without giving effect on the input waveguide system. CONSTITUTION:The cut-off frequency of the input waveguide 2 differs from that of the output waveguide 3. For example, an RF signal is fed to the input side waveguide 2. The output is coupled with an RF amplifier 4 by a coupling post 9, amplified by GaAs FET amplifier stages 6, 6' of a MIC circuit 5, coupled with the output side waveguide 3 again by the coupling post 10 and mixed with the local signal from a local oscillation circuit 17 fed to a mixer circuit 6 of a frequency converter 15 provided on the outer wall of the waveguide by a coupling post at the end of the output side waveguide 3 again to obtain an IF output 18. Then the output side waveguide 3 is cut off to the local frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a microwave receiving device including a frequency converter, etc. by coupling a waveguide circuit and a microwave integrated circuit (MIC) in a microwave receiver, etc. It is.

Conventional technology An example of a conventional microwave receiving device is shown in FIG.

In the figure, the input waveguide 61 is configured as a cut-off waveguide that has a cutoff range for the oscillation frequency fL of the local oscillator θe oscillated by a dielectric resonator 67, and a passband for the input RF frequency fH, Local oscillator 66, mixer circuit e5. A microwave integrated circuit 62 constituting a frequency converter with RF amplifiers 63, 64, etc. is shielded with a ground conductor 7o and a shield case 68, and the RF signal from the waveguide is coupled to the microstrip line 74 with a coupling boss 71.
It is supplied to the F amplifier 63. In the figure, 69 is a frequency adjustment screw, 73 is a coupling post insertion hole provided in the waveguide 61, and 7
2 is an insulating ring made of Teflon or the like. In the conventional example shown in FIG. 3, in order to prevent local oscillation signals from leaking to the input end of the waveguide and to prevent image disturbance,
The cutoff of the waveguide 61 is set so as to be in the cutoff range with respect to the local frequency and the image frequency, and the length of the waveguide 61 is set to be quite long in order to increase the cutoff effect.

Problems to be Solved by the Invention In such a conventional circuit configuration, in order to increase the effect of preventing local signal leakage, it is necessary to bring the cutoff frequency of the waveguide as close to the RF frequency as possible and to shorten the waveguide length. (Here we assume that the local frequency is lower than the RF frequency). Therefore, even if the input RF frequencies were slightly different, it was necessary to change the dimensions of the inner diameter of the waveguide in order to change the cutoff frequency of the input waveguide. Furthermore, since the waveguide length is increased, the transmission loss of the waveguide increases, which deteriorates the noise figure of the receiver. Also, if the input waveguide is configured as a cutoff waveguide, the diameter of the input waveguide will be smaller than that of the standard waveguide (
For example, in the 12 GHz band, it is different from WR-100, etc.), so a special waveguide conversion circuit or adapter is required for connection to the antenna.

Means for Solving the Problems In order to solve the above problems, the present invention first separates the frequency converter circuit 62 into an RF amplification section, a mixer, and a local section, shortens the input waveguide, and separates the RF amplification section from the circuit 62 of the frequency converter. Combine this R
Cutoff R of the output of the F amplifier section with respect to the local frequency
It is coupled to an output waveguide that passes the F frequency, and the RF multiplied signal is taken out again from the other end of this output waveguide, and this is added to the mixer circuit of the microwave integrated circuit to take out the IF multiplied signal.

Function: Since the cutoff waveguide is placed after the RF amplification section, the RF amplifier can be used in a wide band, for example, in the case of satellite broadcasting.
If it is 1.7~12.7GH2, Japanese satellite broadcasting (1
1,7-12,0GHz), European satellite broadcasting (11,7-12-5GHz), American satellite broadcasting (
Since all frequencies (12.2 to 12.7 GHz) can be covered by a common RF amplifier, the same cutoff frequency can be used for the input waveguide, and there is no need to increase the length of the input waveguide. Therefore, waveguide transmission losses are also reduced. Also,
Connection to the antenna also requires no special adapter or waveguide conversion circuit, making it a compact microwave converter. Moreover, when the local frequency is changed, only the cutoff frequency of the output side waveguide needs to be changed. In addition, since the RF amplification section and the local section are separated, local signals will not directly jump from the local section to the RF amplification section, so leakage of local signals attenuated by the output waveguide will be prevented from occurring at the RF amplification section. Since it is further suppressed, local leakage to the input waveguide side can be sufficiently suppressed. Further, since the image signal of the output waveguide 1 is sufficiently suppressed, an image suppression filter is not required in a mixer circuit such as a MIC circuit (microwave integrated circuit), and the mixer circuit becomes simple.

Embodiment FIG. 1 shows an embodiment of the microwave receiving apparatus of the present invention. In the figure, a is a sectional view of the waveguide housing 1 viewed from the side. In the figure, the RF multiplier signal is applied to the input waveguide 2, and its output is coupled to the RF amplifier 4 at the coupling post 9, amplified by the GaAs FET amplification stage 6.6' of the MIC circuit 5, and sent to the coupling post. 10, it is again coupled to the output waveguide 3, and again added to the mixer circuit 16 of the frequency converter 16 provided on the outer wall of the waveguide by the coupling post 27 at the end of the output waveguide 3. j) IF output 18 is obtained by mixing with the local signal from the local oscillation circuit 17. In the same figure, 13, 14, and 29 are coupling holes provided in waveguides 2 and 3, and insulating Teflon support pillars 11°, 12.28, and coupling posts 9 and 10.27 form an isometric coaxial 5oΩ line. are doing. 19 is a dielectric resonator for a local oscillator, 21 is a screw for adjusting the oscillation frequency, 7 and 22 are ground conductors,
23, 24 and 25, 26 are screws for attaching the RF amplifier 4 and frequency converter 15 to the waveguide housing 1, 30 is a seat plate for shorting the waveguide 3, and 31, 32 are the screws for attaching the RF amplifier 4 and frequency converter 15 to the waveguide housing 1. Attachment is screw, 8.20 is RF amplifier 4 and frequency converter 1
5 metal case. FIG. 1 is a sectional view of the input waveguide 2 seen from the input side, and the same numbers as in FIG. 1a indicate the same parts. Although the input side and output side waveguides 2 and 3 are already treated as circular waveguides in FIG. 1, the waveguides 2 and 3 may be circular or rectangular, or may be different from each other.

In Fig. 1, the output waveguide 3 is cut-off with respect to the local frequency, so the local oscillation circuit 1
The local signal leaking from 7 to the waveguide 3 via the mixer circuit 16 can be sufficiently attenuated by increasing the length of the output waveguide 3 to a certain extent, so that the local signal can be sufficiently attenuated by increasing the length of the output waveguide 3 to a certain extent. is also small enough. Furthermore, since the RF amplifier 4 also has the effect of suppressing relapse between the output and the input, leakage of local signals to the input waveguide 2 can be sufficiently suppressed.

In addition, since the image signal (RF frequency is assumed to be higher than the local frequency) is sufficiently attenuated in the output waveguide 3 more than the local signal, an image filter is not required in the mixer circuit 16, so the mixer circuit is simplified. At the same time, in the image recovery type mixer circuit, the conversion characteristics of the mixer are better than those using the image filter of the MIC circuit due to the smaller filter loss.

FIG. 2 shows another embodiment. In the figure a, the circular waveguide 34
RF amplifiers 37 and 38 are connected to two coupling posts 43 and 45 near the end of the circular waveguide 34.
and is amplified by RF amplification circuits 39 and 41 and coupled from its output ends 40 and 42 to first cutoff waveguide 35 and second cutoff waveguide 36 via coupling posts 44 and 46. , each RF multiplied signal is taken out from the other end of each waveguide 35, 36 again at the coupling post 48, 60, and each is added to a frequency converter 47, 49 consisting of a local oscillator circuit and a mixer circuit, and each IF ratio is output. 51.52 is taken out. 63 is a short circuit plate of the waveguides 35 and 36. Figure 2 shows the configuration as seen from the input circular waveguide side.

As can be seen, since the coupling posts are positioned at an angle of approximately 90°, two electromagnetically orthogonal input RF signals can be separated if they are incident. For example, circularly polarized R
When the F-multiplied signal right-handed circularly polarized wave and the left-handed circularly polarized wave enter at the same time, the RF-multiplied signal corresponding to each polarization can be taken out at the same time at each coupling post. Therefore, when countries are adjacent to each other and radio waves with different polarization planes are used, such as satellite broadcasting in Europe, it is possible to receive broadcasts from other countries at the same time, increasing the number of broadcast receiving channels. Very effective. In this case, the first and second cutoff waveguides 35, 36 are cut so as to provide a cutoff region for each local signal of the frequency converter 47, 49 and a pass region for the RF signal. Off frequency is set. therefore,
As in the first embodiment shown in FIG. 1, leakage of local signals to the input waveguide side can be sufficiently suppressed. In addition, the waveguides 34, 3
Since the 6.36 has an integrated structure, it can be made very compact as a frequency converter. The waveguides 35 and 36 may be rectangular or circular, and the RF amplifiers 48 and 49 can be used in common if they have a wide band (11.7 to 12.7 GHz).

Effects of the Invention As described above, the present invention provides a microwave receiving device that does not affect the input waveguide system, suppresses unnecessary radiation of local signals, has good image suppression characteristics, and as a result has low noise. can be obtained. Further, with a simple configuration, it is possible to obtain a high-performance satellite broadcasting receiver that can simultaneously receive left and right circularly polarized signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a microwave receiving apparatus according to an embodiment of the present invention, in which FIG. 1a is a side view and FIG. 1b is a front view. FIG. 2 is a configuration diagram of a microwave receiving device according to another embodiment of the present invention, and FIG. 2 is a side view, and b is a front view. FIG. 3 is a block diagram of a conventional microwave receiving device. 2.3,34,35.36... Waveguide, 4,3
7゜38...RF amplifier, 15,47.49.
...Frequency converter, 16...Mixer circuit, 17...Local oscillation circuit. Name of agent Patent attorney Toshio Nakao and one other person (b
Figure 2 +7. +? ---U image of cloudy liquid 51.5Z---IF notation (a) (b) Figure 3

Claims (6)

[Claims] (1) A microwave receiving device comprising a microwave circuit having a waveguide input and a waveguide output, and having different cutoff frequencies for the input waveguide and the output waveguide. (2) After dividing n RF signals from the input waveguide and passing each RF signal through separate microwave active circuits, at least one of the n output waveguides has a cut-off frequency different from that of the input waveguide. The microwave receiving device according to claim 1, which is supplied to a tube. (3) By using a circular waveguide as the input waveguide, and inserting coupling posts having a fixed angle to each other within the cross section of the circular waveguide from outside the circular waveguide, different An RF signal having a polarization plane is extracted to the outside of the circular waveguide, and each microwave output signal is coupled to each output waveguide, at least one of which has a different cut-off frequency from the input circular waveguide. The microwave receiving device according to item 2. (4) The microwave receiving device according to claim 3, wherein the angle of the coupling post inserted into the input circular waveguide is 90 degrees. (5) Apply an RF signal from a part of the input circular waveguide, short-circuit the other end, and take out each RF signal from the coupling post.
Each signal is RF amplified by a microwave amplifier, the output is applied to one end of the output waveguide, and the other end is RF amplified.
5. The microwave receiving device according to claim 2, wherein each intermediate frequency signal is obtained by extracting the signal again and applying it to each frequency converter. (6) Coupling each frequency converter to the output of each output waveguide,
Each oscillation frequency of each local oscillator of each frequency converter is set lower than the input RF signal frequency, and the cutoff frequency of each output waveguide is set as a cutoff with respect to each corresponding local oscillation frequency, and with respect to the RF signal frequency. The microwave receiving device according to claim 1, 2, 3, 4, or 5, which is configured to form a pass band.