JPS6059766B2 - Bridging T-type delay equalizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bridging T-type delay equalizer that compensates for loss distortion and deterioration of mismatch attenuation due to coil loss.

Figure 1 is a circuit diagram of a bridged T-type delay equalizer, Figure 2 is a circuit diagram of a conventional bridged T-type delay equalizer that compensates for loss distortion, and Figure 3 is a circuit diagram of a conventional bridged T-type delay equalizer that compensates for loss distortion.
The figure shows attenuation characteristics, and FIG. 4 shows mismatch attenuation characteristics.

In the figure, L, L- are coils, Cl, C2 are capacitors,
R is a resistance, fo is a coil L, a capacitor Cl, and a coil L.

and the resonant frequency of the capacitor Co, f,,f. 1 and 2 are the characteristic curves of the circuit of FIG. 1, and 3 and 4 are the characteristic curves of the circuit of FIG. 2, respectively.
Where high-quality waveform transmission is required, it is necessary to compensate for not only attenuation characteristics but also delay characteristics. As a means of compensating for this delay characteristic, all the methods are shown in FIG. 1 according to the amount of delay. Several stages of bandpass bridging T-type delay equalizers (hereinafter referred to as bridging T-type delay equalizers) are used. However, due to losses in the calcoil L and the coil element, the attenuation characteristic increases approximately in proportion to the delay characteristic, resulting in amplitude distortion. Therefore, in order to maintain a flat damping characteristic while allowing the loss to increase, a shunt arm coil L as shown in FIG. 2 is used. Conventionally, a method has been used in which a resistor R is connected in parallel to the capacitor C2. In this case, a frequency band with poor mismatch attenuation at the input and output terminals is created, and when multiple stages of bridging T-type delay equalizers are connected, the delay characteristics become poor. For example, if we consider a case where the characteristic impedance is 300 ohms and the Q of coil L and coil L2 is about 1 mark, then in the case of the circuit shown in FIG. 1, the amount of attenuation is at the resonance frequency f as shown in FIG. 3. It will be about O, 3db. Frequencies f, , f close to 0 or infinity away from the resonant frequency. In this case, it approaches 0 and produces amplitude distortion. In this case, the amount of mismatch attenuation at the input and output ends is 50 db or more, as shown in FIG. 4.
In order to eliminate this amplitude distortion and level out the amount of attenuation, use the circuit shown in Figure 2 and set the resistor R to the most suitable value for this case, 4.6.
When it is set to kilohms, the attenuation characteristics become almost flat as shown in FIG. 3. However, the amount of mismatch attenuation at the input and output terminals is as shown in FIG. 4, and the resonance frequency is f. At frequencies f, , f2 that are further away or close to infinity, it deteriorates to about 30 db (the impedance seen from the input and output terminals is 287 ohms), resulting in bridging T.
When several stages of delay equalizers are connected to a string, there is a drawback that the delay characteristics deteriorate due to reflection between the stages. As a method of improving this, there is a method of using a resistive attenuator of several dB at the input and output of each stage, but this has the disadvantage that the amount of attenuation increases too much. In order to eliminate the above-mentioned drawbacks, the purpose of the present invention is to provide a bridge that can keep the attenuation constant without increasing too much, and also reduce the mismatch attenuation to a value that does not deteriorate the delay characteristics when used in several stages in series. The present invention provides a T-shaped delay equalizer.

In order to achieve the above object, the present invention comprises a series arm having a parallel resonant circuit of a coil with a center tap and a capacitor, and a shunt arm having a series resonant circuit of the capacitor and the coil between the center tap and the ground. A bridge T-type delay equalizer characterized in that a resistor is connected in parallel to the shunt arm, and a resistor is connected in series to the input side and the output side of the series arm, respectively. There is equipment.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is a circuit diagram of a bridging T-type delay equalizer according to an embodiment of the present invention, FIG. 6 is a diagram showing attenuation characteristics, and FIG. 7 is a diagram showing mismatch attenuation characteristics. Components having the same functions as those in FIGS. 1 to 4 are indicated by the same symbols. Rl and R2 are mismatch attenuation compensation resistors. Now, to explain the case where the characteristic impedance is 300Ω coil L1 and the coil Q is about 1 (4) as before, in the circuit of FIG. 2, the impedance seen from the input and output terminals is at the resonant frequency F. Then, at 300Ω, the frequency F is equal to the characteristic impedance but is far from the resonant frequency.
l and f2 are 287Ω. For this reason, the resistors Rl and R2 shown in FIG. 5 are set to 5Ω, and the impedance over the entire frequency range is set to a value close to the characteristic impedance of 300Ω. That is, the resonance frequency F. 305 ohms, resonance frequency F. For frequencies Fl and f2 that are farther apart, it is approximately 292 ohms.
As a result, the attenuation characteristic is 0.42 as shown in Figure 6.
db, the amount of mismatch attenuation increases only slightly compared to the case of the circuit shown in FIG.
This can be improved by about 7 dB compared to the circuit shown in the figure, and the deterioration of the delay characteristics can be improved when bridge T-type delay equalizers are connected in series. As explained in detail above, according to the present invention, the amount of attenuation is small and does not cause any deviation in the transmission characteristics, and the amount of mismatched attenuation can be set to a value that does not deteriorate the delay characteristics when used in several stages in series. .

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a bridged T-type delay equalizer, Figure 2 is a circuit diagram of a conventional bridged T-type delay equalizer that compensates for loss distortion, and Figures 3 and 6 show the attenuation characteristics. , FIG. 4, and FIG. 7 show mismatch attenuation characteristics, and FIG. 5 shows a circuit diagram of a bridge T-type delay equalizer according to an embodiment of the present invention.

Claims (1)

[Claims] 1 In a delay equalizer consisting of a series arm having a parallel resonant circuit of a coil with a center tap and a capacitor, and a shunt arm having a series resonant circuit of a capacitor and a coil between the center tap and the ground, the shunt A bridge T-type delay equalizer characterized in that a resistor is connected in parallel to the arm, and resistors are connected in series to the input side and the output side of the series arm, respectively.