JPH01200701A - Filter device - Google Patents

Abstract

PURPOSE:To obtain a large attenuation at the outside of the pass band while keeping the delay characteristic and the insertion loss in the pass hand excellent by combining 1st, 2nd and 3rd filters and 1st and 2nd hybrids with nearly equal characteristics. CONSTITUTION:The 1st, 2nd and 3rd filters 4-1, 4-2 and 4-3 have nearly equal characteristics. A microwave power is given to an input terminal 2-1 of the 1st hybrid and its output is filtered by the filters 4-1, 4-2, then the result is outputted from an output terminal 6-1 while being synthesized in-phase. Moreover, the power reflected partly in the filters 4-1, 4-2 is combined in the 1st hybrid, filtered by the filter 4-3 and given to the 2nd hybrid. Thus, a large attenuation at the outside of the pass band is obtained while keeping the insertion loss in the pass band excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveguide filter device mainly used in the microwave band.

[Prior Art] Conventionally, this type of filter device has a configuration as shown in FIG. 6.

In FIG. 6, a first filter 4-1 and a second filter 4
-2 is a band-stop filter with equal characteristics, and the first filter 4-3 is a band-pass filter. The power input from the input terminal l is divided into two equal parts by the machine mask T2, and then transmitted through the transmission line 3-
1 and transmission line 3-2, and is transmitted to filter 4-1 and filter 4-2.

In the filter 4-1 and the filter 4-2, power in the required frequency band is reflected, passes through the transmission line 3-1 and the transmission line 3-2, respectively, and is synthesized at the magic T2. 4
-3.

In the filter 4-3, the signal is further subjected to attenuation outside the passband and is output to the output terminal 7.

[Problems to be solved] - In the conventional wave device described above, in order to obtain a large amount of attenuation outside the passband, the filter 4-1 and the filter 4-2 are required.
Alternatively, it is necessary to increase the number of stages of the filter 4-3, which results in an increase in insertion loss within the passband and a deterioration in delay characteristics.

The present invention has been made to solve these problems, and aims to provide a filtering device that can obtain a large amount of attenuation outside the passband while maintaining good insertion loss in the delay characteristic 1 passband. purpose.

[Means for Solving Problems] In order to achieve the above object, the present invention provides first, second and third filters having substantially equal characteristics, and first and second filters having at least four input and output terminals. A filtering device comprising a hybrid, which inputs power from a first input/output terminal of the first hybrid, divides it into two and outputs it to a second input/output terminal, and outputs the power to the first and third input/output terminals, respectively. After being filtered by the second filter, the output power is input to the second and third input/output terminals of the second hybrid and synthesized in phase from the first input/output terminal and output. (referred to as main transmission power), and
After the power partially reflected by the first and second filters is inputted from the second and third input/output terminals of the first hybrid, combined and outputted to the fourth input/output terminal. '' It is filtered by the second and third filter, further inputted to the fourth input/output terminal of the E-th hybrid, divided into two from the second and third input/output terminals, and outputted from the second and third input/output terminals. The electric power is reflected by the first and second filters and inputted to the second and third input/output terminals of the second hybrid, and from the first input/output terminal, power that is almost in phase with the main transmission power is transmitted. This is a configuration that outputs .

It is preferable that the third filter is configured as a constant resistance filter using two filters having substantially the same characteristics and two hybrids having at least four input/output terminals. It is not limited to this.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a system diagram of a filtering device according to an embodiment, and FIG. 2 is a diagram schematically showing the filtering device.

In Fig. 2, transmission lines 3-1 and 3-2 and transmission lines 5-1 and 5-2 are each 90° in electrical length.
It is set so that the sum of the electrical lengths of the transmission lines 3-1 and 5-1 and the sum of the electrical lengths of the transmission lines 3-2 and 5-2 are equal. Moreover, the first filter 4-1. Second filter 4-2. The third filter 4-3 is a filter having the same attenuation characteristics.

The power input from the input terminal 1 is transmitted to the second and third input/output terminals 2-2. of the Magic T2, which is the first hybrid.
2-3, and each reaches a first filter 4-1 and a second filter 4-2 via a transmission line 3-1 and a transmission line 3-2. In the filter 4-1 and the filter 4-2,
A portion of the input power passes through and another portion is reflected.

The power that has passed through the filter 4-1 and the filter 4-2 passes through the transmission lines 5-1 and 5-2, respectively, and is then delivered to the first and second input/output terminals of the Magic T6, which is the second hybrid. 6-2 and 6-3 in the same phase, are combined in the magic T6, and are sent to the first input/output terminal 6-1, and then output to the output terminal 7.
is output to. This is the main power.

, On the other hand, the power reflected by the filter 4-1 and the filter 4-2 passes through the transmission line 3-1 and the transmission line 3-2, respectively, and reaches the second and third input/output ends 2 of the magic T2. -2.2-3
The two signals are inputted in a phase-transmitting manner to the magic T2, synthesized within the magic T2, outputted to the fourth input/output terminal 2-4, and transmitted to the third transducer 4-3 via the transmission line 3-3.

In the filter 4-3, a part of the input power passes through the transmission line 5.
-3 to the fourth input/output terminal 6-4 of the magic T6, and the second and third input/output terminals 6-2.6 of the magic T6.
-3 and is output after being divided into two by the phase transmission. Each output power is transmitted to the filter 4-1 and the filter 4-2 via the transmission line 5-1 and the transmission line 5-2.

Then, the power reflected by the filter 4-1 and the filter 4-2 passes through the transmission line 5-1 and the transmission line 5-2 again to the second and third input/output terminals 6-2 of the magic T6. , '6-3
The signals arrive at the same phase, are synthesized within the magic T6, and are output to the first input/output terminal 6-1. This is taken as the sub-transmission power.

If the lengths of the transmission lines 3-3 and 5-3 are selected so that the main transmission power and the sub-transmission power are in phase, the main transmission power and the sub-transmission power will cancel each other out. Filter 4-
1. Outside the passband of filter 4-2, filters 4-1. A larger amount of attenuation can be obtained than when the filter 4-2 is used alone.

Within the passband, the waveform filter 4-1. Since the reflected power of the filter 4-2 is extremely small, almost no sub-transmission power appears, and the increase in insertion loss can be ignored.

In the following explanation, for convenience, the third filter 4-3 was treated as a single filter, but in reality, it is treated as three filters with the same characteristics, as shown in Figure 3. The third filter is composed of the royal hybrid.

Next, the third filter will be explained in more detail based on FIG. 3.

In FIG. 3, the power input from the input terminal 4-3-3 is divided into two by the hybrid 4-3-3, and the transmission line 4
-3-5 or transmission line 4-3-6, filter 4-3
-1 and the holowave device 4-3=2. Filter 4-3-1
Alternatively, the power that has passed through the filter 4-3-2 reaches the hybrid node 4-3-3 via the respective transmission lines 4-3-7 or 4-3-8.

Transmission lines 1-3-5 and 4-3-7, filter 4-3-
1 and the transmission lines 4-3-2 and 4-3-
8. By making the length of the path consisting of the filter 4-3-2 equal, the power divided into two by the hybrid 4-3-3 is divided into two by the filter 4-3-1 and the filter 4-3. The electric power that has passed through -2 is input to the hybrid 4-3-2 in the same phase, so it is output to the output end 4-3-5. (This is the sub-transmission power mentioned above.) On the other hand, the power reflected by the filter 4-3-1 and the filter 4-3-2 is transmitted to the transmission line 4-3-5 and the transmission line 4-3-5. Since the electrical lengths of 6 are different by 90 degrees, high print 4-3-
Input 3 using phase sending. Therefore, it is absorbed by the terminator 8 and is not output to the input terminal 4-3-4.

In this way, the wave filter shown in Figure 3 operates as a constant resistance wave filter without reflected waves to the input side, so if it is used as the third wave filter shown in Figure 2, , filter 4-1.47
The unbalance due to the difference in characteristics such as T2 and Magic T2.6 can be absorbed by the terminator 8, and extremely stable operation can be obtained as a whole.

FIG. 4 is a diagram showing the characteristics of the filter device according to the embodiment described above, in which the broken line a shows the characteristics of the filter 4-1, 4-2 or 4-3 alone, and the solid line shows the characteristics of the filtering device according to this embodiment. As is clear from the figure, in this example, at the same out-of-band frequency, an attenuation amount that is approximately twice the value expressed in dB value of the attenuation amount of a single element is obtained.

In this way, the filtering device of the present invention can handle large out-of-band signals without increasing the number of stages of a single filter, that is, without increasing insertion loss within the passband, and without deteriorating delay characteristics. The amount of attenuation can be obtained.

Further, the filtering device of the present invention may slightly change the characteristics of the third filter 4-3 from those of the first filter 4-1 or the second filter 4-2, or line 3-3 and transmission line 5
By changing the length of -3 and adjusting the phase difference between the main transmission power and the sub transmission power, desired characteristics can be obtained.

In the above-mentioned embodiment, a case was explained in which Magic-T is used as a hybrid, but it is clear that the filtering device can be constructed using other hybrids, such as a short slot 3 dB coupler.

Further, as the third filter, if a filter constructed of Magic E and a thin waveguide as shown in FIG. 5 is used, it can be made compact.

[Effects of the Invention] As explained above, according to the wave device of the present invention, by combining filters having substantially the same characteristics, the delay characteristic 9 can be improved.
This has the effect that a large amount of attenuation outside the passband can be obtained while maintaining good insertion loss within the passband.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a filtering device according to an embodiment of the present invention, and FIG.
The figure is a diagram schematically showing the same filtering device, FIG. 3 is a diagram schematically showing a configuration example of the third filter, FIG. 4 is a characteristic diagram of the filtering device, and FIG. FIG. 6 is a perspective view showing a specific example of the configuration of the third filter, and FIG. 6 is a system diagram showing a conventional example. l2 input terminal 2: first hybrid 3-1: transmission line 3-2: transmission line 3-3: transmission line 4-1: first wave filter 4-2 = second filter 4 -3=Third filter 5-1: Transmission line 5-2: Transmission line 5-3: Transmission line 6: Second hybrid 7: Output terminal 8-1: Terminal 8-2 Two terminators

Claims (1)

[Claims] first, second and third filters having substantially equal characteristics;
A filtering device comprising a first and a second hybrid having at least four input/output ends, wherein input is input from the first input/output end of the first hybrid, and second and third input/output ends of the first hybrid are input. The output power is divided into two and filtered by the first and second filters, respectively, and then input to the second and third input/output terminals of the second hybrid, and then input to the first input/output terminal. (This output power is referred to as the main transmission power) and the power that is partially reflected by the first and second filters is combined and outputted in the same phase from the first and second filters. The signal is inputted from the third input/output terminal, combined and outputted to the fourth input/output terminal, filtered by the third filter, and further inputted to the fourth input/output terminal of the second hybrid. The output power is divided into two parts from the second and third input/output terminals, and this output power is reflected by the first and second filters and input to the second and third input/output terminals of the second hybrid. A filtering device characterized in that the first input/output terminal outputs power approximately in phase with the main transmission power.