JPH07123213B2 - Track equalizer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line equalizer used for satellite communication and the like.

[0002]

2. Description of the Related Art Generally, an earth station apparatus in satellite communication is provided with a radio station building and a terminal station building, and these radio station building and the terminal station building are often located apart from each other. That is, the high frequency device installed in the wireless station building and the terminal device installed in the terminal station building are connected by a long-distance coaxial cable. In such an earth station device, a line equalizer is used in order to compensate the frequency characteristic of the coaxial cable.

The above frequency characteristic is f ^1/2 (f is frequency)
This is known as loss, and in this frequency characteristic, the attenuation amount (dB) in the coaxial cable increases in proportion to f ^1/2 .

Conventionally, as a line equalizer for compensating for f ^1/2 loss, an equalizer including an amplifier and a plurality of filters each including a resistor, a capacitor, and a coil is known (for example, a special equalizer). Kaisho 63-283220
Issue).

[0005]

As described above, since the conventional line equalizer uses a plurality of sets of filters each including a resistor, a capacitor, and a coil, the number of parts is increased, and as a result, There is a problem that not only the assembly time becomes long, but also the number of adjustment points increases.

In addition, there is a problem that not only ripples are present due to the connection pattern between the respective parts, but also the equalized waveform is disturbed due to the ripple of the frequency characteristic curve due to the synthetic characteristics of the plural sets of filters.

An object of the present invention is to provide a line equalizer that is easy to assemble and adjust.

Another object of the present invention is to provide a line equalizer in which the equalized waveform is not disturbed.

[0009]

According to the present invention, there is provided a first hybrid having first to third terminals and a second hybrid having fourth to sixth terminals. And a center frequency of at least one of the second hybrids is distant from a signal frequency for line equalization, and the first hybrid outputs a first output signal according to an input signal applied to the first terminal. Is applied to the second terminal and a second output signal whose phase is delayed by 90 degrees with respect to the first output signal is applied to the third terminal, and the second hybrid is A third output signal is applied to the fifth terminal in response to the input signal applied to the fourth terminal, and its phase is relative to the third output signal in response to the input signal applied to the sixth terminal. Was delayed by 90 degrees 4 of the output signal has the function of giving to the fifth terminal, the second terminal being connected to the sixth terminal, the third terminal is the fourth through the variable attenuator
A line equalizer characterized in that it is connected to the terminals of.

[0010]

EXAMPLES The present invention will be described below with reference to examples.

Referring to FIG. 1, the line equalizer according to the present invention comprises first and second hybrids 11 and 12 and a variable attenuator 13. First and second hybrid 1
Reference numerals 1 and 12 are so-called 90-degree hybrids, and the 90-degree hybrid has four terminals, and one of the four terminals is terminated. In other words, it is essentially provided with three terminals. In this 90-degree hybrid, when a signal (input signal) is given to one of the three terminals, a signal (output signal) having a small phase delay with respect to the input signal appears at one of the remaining two terminals. A signal (output signal) whose phase is delayed by 90 degrees from the output signal appears at the other of the remaining two terminals. Here, the one terminal is referred to as a 0 degree terminal, and the other terminal is referred to as a -90 degree terminal.

The 0 degree terminal of the first hybrid 11 is the second
Is connected to the -90 degree terminal of the hybrid 12, and the -90 degree terminal of the first hybrid 11 is connected to the 0 degree terminal of the second hybrid via the variable attenuator 13.

In this embodiment, the first hybrid 11
The center frequency at is selected to be extremely higher than the frequency band for line equalization. Thus, the output from the 0 degree terminal of the first hybrid 11 is, as shown in FIG.
It shows a characteristic that its amplitude increases in proportion to the frequency (about 6
dB / oct). On the other hand, -9 of the first hybrid 11
The output from the 0 degree terminal has a substantially flat characteristic. further,
The center frequency of the second hybrid 12 is selected to be equal to the line equalization band.

Here, the length of the coaxial cable is 100 m.
The f ^1/2 loss when the RG-9AU cable of No. 1 is used will be described.

The line equalizer shown in FIG.
FIG. 3 shows the amplitude characteristic of the line equalizer necessary for compensating the loss when used in the frequency band of 00 MHz. In addition,
FIG. 3 also shows a change of 6 dB / oct corresponding to the 0 degree terminal output of the first hybrid 11 (hereinafter referred to as 6d.
The change in B / oct is simply called the output characteristic).

In FIG. 3, comparing the amplitude characteristic and the output characteristic, the amplitude characteristic and the output characteristic are almost the same curve on the high frequency side of the frequency band, and the output characteristic sharply decreases on the low frequency side. You can see that Therefore, in the line equalizer shown in FIG.
After the -90 degree terminal output is attenuated to a predetermined amplitude value by the variable attenuator 13, the second hybrid 12
It is given to the 0 degree terminal of. As a result, the output characteristic in the low frequency range can be brought close to the f ^1/2 characteristic. As described above, the −90 degree terminal output of the first hybrid 11 is flat in the line equalization band, but the −90 degree terminal output and the 0 degree terminal output of the first hybrid 11 are added in the second hybrid 12. In this case, the increase rate of the amplitude due to the addition is larger on the low frequency side where the amplitude is smaller, and as a result, the desired characteristics can be obtained.

The operation of the line equalizer shown in FIG. 1 will be described using mathematical expressions. Now, the electrical lengths of the two paths from the output side of the first hybrid 11 to the input side of the second hybrid 12 will be described. If combined, the phase delays in the first and second hybrids 11 and 12 are both 9
Since it is 0 degrees, the signals in the above two paths are
Will be added in-phase in the hybrid 12 of.

Since the second hybrid 12 has a flat frequency characteristic in the line equalization band, the composite signal in the second hybrid 12 can be expressed as A ₀ (f / f ₀ + a). Here, f / f ₀ is 6 dB / oct
Is a component on the 0 degree side, which shows the characteristic of f, f is a frequency, and f ₀ is a reference frequency (here, 100 MHz). Further, a indicates a component after passing through the variable attenuator 13, and A ₀ is a multiplication factor for correcting the entire level. This multiplication factor can be realized by connecting an amplifier or attenuator to the outside.

In order to compare the above synthetic signal with f ^1/2 loss, when expressed in dB, A = 20log (f / f ₀ + a) + A ₁ (where A is the amplitude (dB) of the synthetic signal). Yes, A ₁ is 20 liters
ogA ₀ ).

Using the above equation, a = 0.8, A ₁ = 1.
When the amplitude of the combined signal is calculated as 8, the result (loss when used in the frequency band of 100 MHz to 800 MHz) as shown in FIG. 4 is obtained. It can be seen from FIG. 4 that A can compensate the f ^1/2 loss within an accuracy of ± 0.6 dB over a frequency of 3 octaves.

In the embodiment described above, the second hybrid 1
Although the center frequency in 2 is equal to the line equalization band, the center frequency of the second hybrid 12 is shifted up and down to use a region where the frequency characteristics are not flat, or the attenuation amount in the variable attenuator 13 is set to The line equalization characteristics can be changed by changing the line equalization characteristics. In addition, in the present embodiment, the center frequency of the first hybrid 11 is higher than the frequency band for line equalization,
The center frequencies of the second hybrid 12 are selected to be equal, but they are interchanged, and the 0 degree terminal of the first hybrid 11 and the second hybrid 12 are also replaced.
It is clear that even if the variable attenuator 13 is inserted between the -90 degree terminal and the -90 degree terminal, exactly the same effect can be obtained.

Further, although the center frequency in the first hybrid 11 is selected to be extremely higher than the line equalization band in the above embodiment, when the center frequency is lowered, the 0 degree terminal output in the first hybrid 11 is 6 dB / oc
The curve becomes gentler than t, and it is possible to deal with the case where the f ^1/2 loss curve is gentler. When the f ^1/2 loss curve changes abruptly, abrupt characteristics can be realized by connecting the line equalizers shown in FIG. 1 in multiple stages to form an equalizer.

[0023]

As described above, in the line equalizer according to the present invention, not only the number of parts is reduced and the structure is simplified, but also the disturbance of the equalized waveform can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a line equalizer according to the present invention.

FIG. 2 is a diagram showing frequency characteristics of the first hybrid shown in FIG.

FIG. 3 is a diagram showing an f ^1/2 loss compensation characteristic and a 6 dB / oct characteristic.

FIG. 4 is a circuit diagram showing the line equalizer shown in FIG.
It is a figure showing f1 ^{/ 2} loss and the synthetic | combination signal amplitude when using it at z-800 MHz.

[Explanation of symbols]

 11,12 90 degree hybrid 13 Variable attenuator

Claims (2)

[Claims] 1. A first hybrid having first to third terminals, and a second hybrid having fourth to sixth terminals, wherein at least one of the first and second hybrids is provided. The two center frequencies are distant from the signal frequency for line equalization, and the first hybrid applies a first output signal to the second terminal in response to an input signal applied to the first terminal and It has a function of giving a second output signal whose phase is delayed by 90 degrees to the first output signal to the third terminal, and the second hybrid is an input signal given to the fourth terminal. A fourth output signal whose phase is delayed by 90 degrees with respect to the third output signal according to the input signal supplied to the fifth terminal and the third output signal accordingly. To the fifth terminal A line or the like having a function of giving, the second terminal is connected to the sixth terminal, and the third terminal is connected to the fourth terminal via a variable attenuator. Chemist. 2. A line equalizer in which a plurality of line equalizers according to claim 1 are used and the equalizers are connected in multiple stages.