High speed circuit and low frequency reducing passive equalizer
阅读说明:本技术 高速电路及低频减少被动等化器 (High speed circuit and low frequency reducing passive equalizer ) 是由 李政宪 于 2018-09-21 设计创作,主要内容包括:本发明公开一种高速电路及低频减少被动等化器,其中该高速电路中的差分传输线结构以减少低频衰减的大小。前述传输线结构形成于一印刷电路板上。一对差分传输线连接一信号接收器和一信号发信器。被动等化器具有一第一分流器和一第二分流器,其中第一分流器耦合至一对差分传输线之一者,且第二分流器耦合至一对差分传输线之另一者。被动等化器具有一电感和一电阻,串联耦合至前述分流器。对于低频信号,被动等化器作为一对差分传输线的分流电阻。(The invention discloses a high-speed circuit and a low-frequency reduction passive equalizer, wherein a differential transmission line structure in the high-speed circuit is used for reducing the low-frequency attenuation. The transmission line structure is formed on a printed circuit board. A pair of differential transmission lines connects a signal receiver and a signal transmitter. The passive equalizer has a first splitter coupled to one of the pair of differential transmission lines and a second splitter coupled to the other of the pair of differential transmission lines. The passive equalizer has an inductor and a resistor coupled in series to the shunt. For low frequency signals, the passive equalizer acts as a shunt resistor for a pair of differential transmission lines.)
1. A high speed circuit, comprising:
a printed circuit board;
a signal transmitter on the printed circuit board;
a signal receiver on the printed circuit board;
a pair of differential transmission lines connecting the signal receiver and the signal transmitter; and
and a passive equalizer coupled to the pair of differential transmission lines, the passive equalizer serving as a shunt resistor of the pair of differential transmission lines for low frequency signals.
2. The high speed circuit of claim 1 wherein the passive equalizer comprises a first shunt coupled to one of the pair of differential transmission lines, a second shunt coupled to the other of the pair of differential transmission lines, an inductor, and a resistor, the inductor and the resistor coupled in series to the first shunt and the second shunt.
3. A high speed circuit as recited in claim 2, wherein the inductor selects as a short circuit at high frequency signals and as a filter at low frequency signals.
4. The high speed circuit of claim 1, wherein the differential transmission lines are formed on the printed circuit board.
5. The high speed circuit of claim 4, wherein the passive equalizer is mounted on a surface on which the signal receiver and the signal transmitter are mounted.
6. The high speed circuit of claim 4, wherein the passive equalizer is mounted on an opposite surface of the printed circuit board from a surface on which the signal receiver and the signal transmitter are mounted.
7. The high-speed circuit of claim 1, wherein the differential transmission lines bring-in signals according to the peripheral component interconnect express standard.
8. A passive equalizer for reducing attenuation of low frequency signals on a differential transmission line pair, the passive equalizer comprising:
a first shunt coupled to one of the pair of differential transmission lines;
a second shunt coupled to the other of the pair of differential transmission lines;
an inductor having one end coupled to the first shunt; and
a resistor having one end coupled to the inductor and an opposite end coupled to the second shunt; wherein for low frequency signals, the inductor and the resistor act as a shunt resistor for the pair of differential transmission lines.
Technical Field
The present invention is directed to allowing longer transmission lines without reducing signal quality. More particularly, the present invention relates to a low frequency reduction passive equalizer for reducing a deviation between low frequency attenuation and high frequency attenuation in a long differential signal transmission line.
Background
High-speed differential signal transmission lines (high speed differential signal channels) have been widely used in various products, such as servers or storage products. Many server or storage products include a rack that supports and connects different printed circuit boards having various electronic devices mounted thereon. For example, a printed circuit board may have one or more integrated circuit chips mounted thereon, either alone or in combination with similar or other devices. The printed circuit board includes various signal transmission lines to provide signals to devices on the board. The signal transmission lines are generally configured as differential signal transmission line pairs (differential trace pairs) of a specific signal.
As printed circuit boards become more complex, containing more components, the wiring that connects between the components requires longer signal path lengths. Fig. 1 shows a
This effect can be seen by the waveform of the signal received from the
For such longer path applications, active (active) elements such as boosters (re-drivers) are introduced and used in recent designs in order to allow for adequate signal transmission. For example, in a typical server, a twenty inch (20 ") data path is used. The current Peripheral Component interconnect express (PCIe) 4 standard requires an enhancer to ensure signal integrity for the data path length in the server. The booster is a signal amplifier that receives a signal at a point in the channel and amplifies the signal to reduce attenuation. Therefore, a stiffener is currently necessary to configure
Therefore, passive components are needed to reduce the deviation between high and low frequency attenuation to allow longer signal path applications. Furthermore, there is a need for components that allow the return path (return path) length in the differential signal transmission line pair to maintain the same system power. In addition, passive components that do not require additional energy during operation are desirable.
Disclosure of Invention
An example of the present invention is a high speed circuit. The high speed circuit includes a printed circuit board. The high speed circuit includes a signal transmitter and a signal receiver on the printed circuit board. A pair of differential transmission lines connects the signal receiver and the signal transmitter. A passive equalizer is coupled to a pair of differential transmission lines. For low frequency signals, the passive equalizer acts as a shunt resistor for a pair of differential transmission lines.
Another example is a passive equalizer to reduce the attenuation of a signal on a differential transmission line pair. A first shunt is coupled to one of the pair of differential transmission lines. A second shunt is coupled to the other of the pair of differential transmission lines. An inductor has one end coupled to the first shunt. A resistor has one end coupled to the opposite end of the inductor and an opposite end coupled to the second shunt. For low frequency signals, the aforementioned inductor and resistor act as a shunt resistor for a pair of differential transmission lines.
The foregoing is not intended to represent every embodiment or every aspect of the present invention, but is merely illustrative of some of the novel aspects and features described herein. The foregoing and other features and advantages of the invention are apparent from the following detailed description of representative embodiments and modes for carrying out the invention, taken in conjunction with the accompanying drawings and claims.
Drawings
FIG. 1 is a schematic diagram of a conventional printed circuit board having a differential transmission line channel connecting a receiver and a transmitter;
FIG. 2A is a graph of an input signal applied to the transmission line of FIG. 1;
FIG. 2B is a graph of different output signals from the input signal of FIG. 2A, depending on the length of the transmission line of FIG. 1;
FIG. 2C is a graph of signal attenuation as a function of length of the transmission line of FIG. 1;
FIG. 3 is a schematic diagram of a circuit board having a differential signal pair transmission line with passive equalizers to reduce attenuation;
fig. 4 is a circuit diagram of the differential signal pair transmission line of fig. 3 and a schematic diagram of a passive equalizer according to the present invention;
FIG. 5 is a log-linear plot of signal gain as a function of frequency;
FIG. 6A is a schematic illustration of simulation results of signals transmitted over differential signal pair transmission lines;
fig. 6B is a diagram illustrating simulation results of signals transmitted through a differential signal pair transmission line having a passive equalizer.
Description of the symbols
10 circuit board
12 signal transmission line
14 transmitter
16 receiver
20. 22, 24, 32, 34 lines
100 circuit board/printed circuit board
110 signal transmitter element/signal transmitter/transmitter
120 signal receiver element/signal receiver/receiver
130 transmission line
132. 134 input section
136. 138 output section
142. 144 body element/body segment
150 passive equalizer element/passive equalizer
146 communication column
400 first shunt
402 second shunt
410 resistance
412 inductance
500 trace
502 low frequency
504 high frequency
Detailed Description
The invention may be embodied in many different forms. Representative embodiments are shown in the drawings and will be described herein in detail. The present invention is an example or illustration of the principles and is not intended to limit the broad aspects of the invention to the embodiments disclosed. In such cases, elements and limitations that are disclosed, for example, in the abstract, summary, and descriptive section of the embodiments but not explicitly recited in the claims, are not to be incorporated into the claims, either individually or collectively, by implication, inference, or otherwise. For the purposes of this method of implementation, a single form may contain multiple forms and vice versa, unless specifically stated otherwise; the term "including" means "including but not limited to". Also, approximate terms such as "approximately", "left-right", and the like, as used herein, are intended to mean, for example, "in the range of" 3 to 5% "," within acceptable manufacturing tolerances ", or any logical combination thereof.
Fig. 3 illustrates a
In this example, the main length of the
A
In fact, most equalizers act as high pass filters (high pass filters). For a passive high pass filter, while the low frequency part will experience a larger attenuation to equalize the energy, the high frequency part will also be attenuated. The
For an active high pass filter, additional power is required to achieve gain in the high frequency portion of the signal. In order to equalize the high and low frequency portions, the
Fig. 4 is a circuit diagram showing an exemplary configuration in which the
Although a single inductor and resistor are shown in this example, additional poles or resistors may be connected in parallel to the
In operation, the
Fig. 5 is a log-linear plot of signal gain as a function of frequency as defined in the PCIe 3.0 base specification. Fig. 5 shows a
An example of an application of the high-speed differential signal transmission line may be on a circuit board of a server. In one example, the server has a twenty-inch data path, and thus in prior known designs, the
Fig. 6A and 6B are simulation results of signals from a twenty-
As used herein, terms such as "element," "module," "system," and the like are generally intended to refer to a computer-related entity, either hardware (e.g., circuitry), a combination of hardware and software, or an entity associated with a operating machine that performs a specified function or functions. For example, a component may be, but is not limited to being, a program executing on a processor (e.g., a digital signal processor), a processor, an object, an execution document, a thread of execution, a program, and/or a computer. By way of illustration, both an application executing on a controller and the controller can be an element. One or more elements may reside within a program and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. In addition, a "device" may take the form of specially designed hardware; enabling hardware to perform specific functions by executing software on the hardware to specialize the general-purpose hardware; software stored on a computer-readable medium; or a combination thereof.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" may include plural referents unless the context clearly dictates otherwise. Furthermore, the terms "comprising," having, "" appended to, "or variants thereof, as used in the detailed description and/or the claims, are intended to be inclusive in a manner similar to the term" comprising.
Unless defined otherwise, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present invention and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Many modifications to the disclosed embodiments may be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Thus, the scope of the present invention should not be limited by any of the above-described embodiments. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.
Although the invention has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application.
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