JPS59188259A - Amplifier for bus receiver - Google Patents

Abstract

PURPOSE:To obtain a high-speed and long-distance communication line by providing an equalizing circuit which compensates a decrease in gain in the high frequency range of a transmission line between the emitters of transistors (TR) of a differential amplifier. CONSTITUTION:The differential amplifier consists of TRs Q1 and Q2. The equalizing circuit Z1 is connected between the emitters of the TRs Q1 and Q2 and consists of the series circuit of a resistance R1 and a capacitor C1. An output signal is applied between the bases of the TRs Q1 and Q2, and an output is led out from between the collectors. Thus, the equalizing circuit is provided to compensate a decrease in gain in the high frequency range.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data way path receiver, and more particularly to a path receiver amplifier that has an internal equalization function to enable faster and longer communication lines. Regarding.

A so-called data way, in which a single transmission line (often a coaxial cable) is shared by multiple devices, is widely used, and an example of its configuration is shown in FIG. The figure shows a linear dataway. In the figure, S□~5n (n is an integer, the same applies hereinafter) are stations, T1~Tn are transceivers, and A~5n are stations.
An is a coupler, and DB is a transmission line. The connections between each station ~Sn and the transmission line DB are performed by bus couplers A□~An, and converted to logic levels by transceivers T1~Tn. In dataways configured in this manner, limitations on transmission length and number of stations are determined by attenuation, bandwidth, and reflection. That is, as the number of loads (stations) increases, attenuation increases and reflections increase due to insertion. Additionally, increasing cable length increases attenuation and bandwidth limitations.

FIG. 2 is a diagram showing signal propagation characteristics. In the figure,
(a) is station S1, (b) is station S
2, (C) shows the respective received signal waveforms of station Sn. It can be seen that at station S, the received signal is attenuated and the waveform is blunted.
- Monkey Also, as the cable length increases, attenuation and bandwidth limiting increase. In the case of one-to-one transmission, attenuation and band limitation can be equalized by a circuit with opposite characteristics. However, in the case of data ways, equalization is not generally performed because the transmission path changes for each communication. Therefore, in the case of the linear data way shown in FIG. 1, the transmission length is significantly limited compared to the case of one-to-one transmission.

The present invention has been made in view of these points, and
A path receiver amplifier has been realized that can increase the speed and distance of communication lines by providing a suitable waveform equalization function to the path receiver of each station.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 is a diagram showing the configuration of the transceiver.

In the figure, 1 is a coupler attached to the transmission line DB)
2 is a transmitting driver, 3 is a receiving amplifier, and 4 is a discriminator that receives the output of the amplifier. The amplifier 3 and the discriminator 4 constitute a path receiver, and the amplifier 3 is provided with an equalization function. FIG. 4 is a diagram showing signal transfer characteristics. The horizontal axis is frequency and the vertical axis is gain. fsl is station S2
(See Figure 1), fs□ indicates the characteristics of station S, where 1 indicates no equalization, 2 indicates suitability for equalization, and 3 indicates unsuitability for equalization. . FIG. 5 is a diagram showing transmission waveforms, where L(,) shows the transmission waveform of station S, and (b) shows the transmission waveform of station S2. Numbers 1 to 5 in the figure are the same as those in FIG. 1 is the case where there is no equalization, which is suitable for nearby stations, but not suitable for distant stays/cons. 3 is a case where equalization is performed so that a complete waveform can be obtained at station S.
The equalization becomes too large. On the other hand, in case 2, the equalization is insufficient at station S, but the waveform does not deteriorate so much even at system station S2.

From this, if the amplifier 3 (Fig. 3) is equipped with an equalization function that sets the equalization amount so that the underequalization amount at station S is equal to the overequalization amount at station S2, the signal will not be attenuated. If a data way can be realized, it becomes K.

FIG. 6 is an electric circuit diagram showing one configuration of a receiving amplifier having an equalization function according to the present invention. The amplifier shown in the figure is
It is composed of a differential amplifier using a transistor RQ2. The second circuit is an equalization circuit connected between the emitters of the transistor Q□r Q2, which is composed of a series circuit of a resistor R□ and a capacitor C□. 10 is a constant current source. R is an emitter resistance, and R8 is a collector resistance.

The input signal is applied between the paces of transistors Qll and Q2, and the output is taken from between the collectors. The gain of the circuit configured in this way is determined by using the identification symbols as values for each resistor, capacitor, etc., and inputting the input signal to each base to v1□.

V□2, the output signal of each collector is VV, then 01
'02 It is given by the following equation.

Assuming that an RC series circuit as shown in the figure is used as the two equalizer circuits, equation (1) becomes K as follows.

The frequency characteristic of the gain expressed by equation (3) is illustrated in FIG. 7. The horizontal axis shows frequency and the vertical axis shows gain. The normal gain (normalized value of 1) is maintained up to the frequency f, but after f□ the gain increases and reaches a constant value at f2. The f-work, f2, and gain increase amount ΔG are each expressed by the following equations.

2R.

R□ (6) That is, in the circuit shown in Fig. 6, the effect occurs when f≧f1, and f
When ≧f2, the gain increases by ΔG. According to the invention,
Since the gain increases in the high frequency range, even when the number of connected stations increases, signal waveform attenuation and waveform shape changes can be suppressed, and cable band limitations can be improved. The features of the circuit of the present invention are listed below.

(1) Since it is a differential type, input common mode voltage can be removed.

(2) Since there is only one equalizer circuit, variations in elements that occur when a plurality of equalizers are required do not become a problem.

the law of nature! I) The configuration is extremely simple.

FIG. 8 is a diagram showing an example in which the circuit of the present invention is used in a transceiver. The figure shows an example in which the line and the transformer T are electrically insulated.

As described above in detail, the present invention provides a path receiver amplifier that can provide an appropriate waveform equalization function to the path receiver of each stage 11/11, thereby increasing the speed and distance of the communication line. It can be manifested.

[Brief explanation of the drawing]

Figure 1 shows the configuration of the dataway, Figure 2 shows the signal propagation characteristics, Figure 3 shows the transceiver configuration, Figure 4 shows the signal transfer characteristics, and Figure 5. 6 is a diagram showing a transmission waveform, FIG. 6 is an electric circuit diagram showing an embodiment of the present invention, FIG. 7 is a diagram showing gain characteristics, and FIG. 8 is a diagram showing the configuration of a transceiver to which the present invention is applied. . S-3...Ten line, T1~Tn...transit, n A□~An...coupler, DB...transmission line, 1...
・Coupler, 2...driver, 6...receiving amplifier,
4... Discriminator, 10... Constant current source, Ro, Re,
R□...Resistor, C...Capacitor, Q□, Q2...
・Transistor, 2nd piece ・Equalization circuit. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. Vee Fig. 7↑ Fig. 8 ee

Claims (2)

[Claims] (1) This is used in the path receiver of the data way system, and uses two transistors to perform equalization between the emitters of each transistor of the differential amplifier to compensate for the decrease in gain in the high frequency region of the transmission line. A path receiver amplifier characterized by comprising a circuit. (2) The path receiver amplifier according to claim 1, wherein a series circuit of a resistor and a capacitor is used as the equalization circuit.