TWI416804B - Equalizer - Google Patents

Abstract

An equalizer includes a resistor and a capacitor. The resistor and the capacitor are connected in parallel. The positive terminal of the capacitor is connected to a signal transmission line of a printed circuit board (PCB). The negative terminal of the capacitor is connected to ground through a terminal resistor. The equalizer can compensate the high frequency loss in the signal transmission line and improves the performance of the PCB. A connector including the equalizer is also provided, and it is used to connect two different electronic device.

Description

Equalizer

The invention relates to an equalizer.

In the printed circuit board transmission line, as the transmission speed of the signal becomes higher and higher, the high frequency loss of the signal is also continuously increased. At present, in order to compensate for the high frequency loss of the signal, when designing the chip, the signal transmission end is usually pre-enhanced and de-emphasized to process the signal. Pre-emphasis compensates for high frequency losses in the transmission line by increasing the high frequency components of the signal. The solution enhances the low frequency component of the signal to make the low frequency component and the high frequency component of the signal after the transmission line relatively balanced, thereby reducing the jitter caused by the excessive difference of the frequency components. However, both of these methods consume a certain amount of power, and their electromagnetic radiation is aggravated as the signal transmission speed increases. How to use a reasonable high-frequency signal compensation device on the signal receiving end of the printed circuit board to meet the transmission requirements of high-speed signals has become an urgent problem to be solved.

In view of the above, it is necessary to provide a high frequency signal compensation device at the signal receiving end.

An equalizer for compensating for a high frequency component of a signal loss in a signal transmission line, comprising a resistor and a capacitor, the resistor being connected in parallel with the capacitor, the anode of the capacitor being connected to the signal transmission line, and the anode being grounded through a terminal resistor The value of the resistor R1 in parallel with the capacitance and the value of the capacitor C1 respectively satisfy the following formula: Where R2 represents the resistance of the terminating resistor and A represents the required low frequency gain; Where F denotes the main frequency of the signal transmitted in the signal transmission line.

Compared with the prior art, the equalizer of the present invention can compensate the high frequency loss of the signal transmitted in the transmission line of the printed circuit board at the signal receiving end, and improve the transmission performance of the printed circuit board.

10‧‧‧ transmission line

20‧‧‧ Equalizer

R1‧‧‧ resistance

R2‧‧‧ terminating resistor

Vi‧‧‧ input voltage

Vo‧‧‧ output voltage

30‧‧‧Connector

1, 2‧‧‧ pin

C1‧‧‧ capacitor

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a circuit diagram of a preferred embodiment of the equalizer of the present invention.

2A and 2B are respectively simulated eye diagrams after the signal is transmitted through the printed circuit board without the equalizer and after being transmitted through the printed circuit board having the equalizer of the present invention.

3A and 3B are simulated histograms of signals transmitted by a printed circuit board that does not contain an equalizer and transmitted through a printed circuit board having an equalizer of the present invention, respectively.

4 is a schematic illustration of a preferred embodiment of the connector of the present invention.

Referring to FIG. 1, a preferred embodiment of the equalizer of the present invention includes a resistor R1 and a capacitor C1. The anode of the capacitor C1 is connected to the transmission line 10, and the anode is grounded through the terminal resistor R2. The anode and the cathode of the capacitor C1 are respectively taken as At the input end and the output end of the chemist 20, the voltages on the positive and negative terminals of the capacitor C1 are denoted as Vi and Vo, respectively, and the resistor R1 is connected in parallel with the capacitor C1.

From the connection relationship of the above components, it is derived that the frequency response in this embodiment is:

Where s represents the complex frequency jw, and C1, R1, and R2 represent the capacitance values of the capacitor C1 and the resistance values of the resistors R1 and R2, respectively. It can be seen from equation (1) that s is 1/(R1*C1) for the zero point of this frequency response, and s is the pole of this frequency response when (R2+R1)/(C1*R1*R2). Therefore, in the case where the resistor R2 is known, in combination with the required low frequency gain and pole position, it is necessary to design a uniformizer that meets the requirements. If the required low frequency gain is A decibel, then you can get:

For the capacitor C1, the capacitance is such that the pole (R2+R1) (C1*R2*R1) is smaller than the main frequency of the signal. If the main frequency of the signal is FHz, then:

It should be pointed out that according to the formula (3), although the capacitance C1 has only the lower limit value, the larger the value, the smaller the zero point 1/(R1*C1), and the frequency range of the low frequency gain effect of the equalizer 20 is higher. narrow. Therefore, the size of the capacitor C1 should be properly selected, taking into account the zero point 1/(R1*C1) and the pole point (R2+R1)/(C1*R2*R1) of the equalizer 20. The resistor R1 and the capacitor C1 can be respectively set as a variable resistor and a variable capacitor.

For a transmission speed of 5 Gbps, the main frequency is 2.5 GHz signal, the resistance R2 is 100 Ω, and it is necessary to design an equalizer with a low frequency gain of -9.5 dB. It can be seen from the above analysis that the pole (R2+R1)/(C1*R2*R1) is smaller than the main frequency of the signal of 2.5 GHz, and the resistor R1 and the capacitor C1 are respectively:

In the present embodiment, C1 is set to 5 pF. Please compare FIG. 2A and FIG. 2B, when the equalizer is not used at the signal receiving end, the signal jitter is large and the eye height is low; after the equalizer 20 is used at the signal receiving end, not only the signal jitter is reduced, but also Increased eye height. It can be seen that the equalizer 20 can compensate for the high frequency loss of the signal in the transmission line of the printed circuit board, reduce the jitter of the signal, and improve the transmission performance of the printed circuit board. Please compare FIG. 3A and FIG. 3B. After using the equalizer 20, the jitter of the signal is also significantly improved.

The invention also relates to a connector 30 having the above-described equalizer. Referring to FIG. 4, in order to save the winding space of the circuit board, the complex equalizer 20 is embedded in the connector 30. The connector 30 is used for connecting a motherboard and an external card. The connector 30 includes a plurality of pins 1 connected to the motherboard and pins 2 connected to the external card. The positive pole of the capacitor C1 of each equalizer 20 is transmitted through the connector. Pin 1 is connected to the motherboard, and the negative pole is connected to the external card through pin 2 of the connector. The resistor R1 of each equalizer 20 is connected in parallel with its capacitor C1. The resistor R1 and the capacitor C1 can be respectively set as variable resistors and variable capacitors, so that the resistance value of the resistor R1 and the capacitance value of the capacitor C1 can be flexibly adjusted according to different design requirements. The connector 30 can also be other connectors that connect two different electronic devices, and the number of equalizers can also be adjusted according to the number of pins and definitions of different connectors.

The equalizer of the present invention can transmit the compensation signal at the signal receiving end in the transmission line of the printed circuit board High frequency loss of transmission, improving the transmission performance of printed circuit boards.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

10‧‧‧ transmission line

20‧‧‧ Equalizer

R1‧‧‧ resistance

C1‧‧‧ capacitor

R2‧‧‧ terminating resistor

Vo‧‧‧ output voltage

Vi‧‧‧ input voltage

Claims (3)

An equalizer for compensating for a high-frequency component of a signal loss in a signal transmission line, comprising a resistor and a capacitor, the resistor being connected in parallel with the capacitor, the anode of the capacitor being connected to the signal transmission line, and the anode being grounded through a terminal resistor, wherein The value of the resistor R1 in parallel with the capacitor and the value of the capacitor C1 respectively satisfy the following formula: Where R2 represents the resistance of the terminating resistor and A represents the required low frequency gain; Where F denotes the main frequency of the signal transmitted in the signal transmission line. The equalizer of claim 1, wherein the resistor connected in parallel with the capacitor is a variable resistor. The equalizer of claim 1, wherein the capacitor is a variable capacitor.