Common-mode suppressor based on differential transmission line

Abstract

A differential data transmission system (200; 700), comprising: a source (201) configured to transmit a differential signal containing data; a load (204) configured to receive the differential signal; and a common-mode suppressor (300; 400; 500; 702) comprising a long, wound differential transmission line configured to carry the differential signal from the source to the load; wherein a length of the differential transmission line is at least greater than one tenth of the wavelength of the differential signal, which is transmitted through the differential transmission lines in a predetermined operating frequency range of the differential signal, further comprising a protection circuit (202; 701) against electrostatic discharges, which is connected to the first (303; 703) and second (304; 704) input pins of the common-mode suppressor (300; 400; 500; 702) and which is configured to provide protection against shocks from electrostatic discharge.

Description

[0001] The present disclosure relates to differential data transmission systems and in particular to a common-mode suppressor associated with them and a method for suppressing common-mode noise.

[0002] In recent years, the diversification of electronic devices has led to an increased demand for high-frequency signal transmission. Differential signaling is the preferred method for many high-frequency devices. Differential signaling is a method for electrically transmitting information using two complementary signals, for example, on two paired wires called a differential pair. Differential signaling is also the first choice for low-power radio frequency links because it provides superior immunity to noise by offering two signal oscillations for a given supply voltage. When differential signaling is used for transmitting high-frequency signals, electromagnetic interference affecting external electronic devices can be reduced.Furthermore, differential transmission can reduce the effects of electromagnetic interference from external electronic devices. However, the signal integrity of differential data transmission lines / buses can be degraded by common-mode noise. Common-mode noise can be generated by the system itself or by coupled radiation.

[0003] US patent 2004 / 0155720A1 discloses a differential data transmission system. US patent 7956704B1 discloses a design for common-mode rejection. Further systems are known from US patents 5184045A and 2011 / 0007439A1.

[0004] The independent claims define the invention from various perspectives. The dependent claims name embodiments of the invention from these different perspectives. The disclosure is further explained and described below with reference to specific exemplary embodiments and the accompanying drawings. Fig. Figure 1 shows a schematic diagram of an example of a differential data transmission system with a common-mode suppressor, which is not a claimed embodiment and serves for explanation purposes; Fig. Figure 2 shows a schematic diagram of a differential data transmission system with a common-mode suppressor and protection against electrostatic discharge (ESD); Fig. Figure 3 shows the schematic diagram of a common-mode suppressor comprising a long wound differential transmission line, according to an embodiment of the disclosure. Fig. Figure 4A shows the layout of a common-mode suppressor having a long wound differential transmission line, according to an embodiment of the disclosure. Fig. Figure 4B shows the exploded view of the differential transmission line of Fig. 4A. Fig. Figures 5A and 5B show a schematic representation of a common-mode suppressor on a semiconductor substrate. Fig. Figures 6A-6D show the simulation results for differential mode and common-mode operation of a common-mode suppressor, according to an embodiment of the disclosure. Fig. Figure 7A shows the schematic diagram of a common-mode suppressor with an ESD protection circuit according to an embodiment of the disclosure. Fig. Figure 7B shows the layout of a common-mode suppressor with an ESD protection circuit according to an embodiment of the disclosure. Fig. Figures 8A-8C show the simulation results for differential mode of a common-mode suppressor with ESD protection according to an embodiment of the disclosure. Fig. Figures 8D - 8F show the simulation results for common-mode operation of a common-mode suppressor with ESD protection according to an embodiment of the disclosure. Fig. 9A and Fig. Figure 9B shows the time domain analysis for a 5 GB / s signal and a 10 GB / s signal according to one embodiment of the disclosure. Fig. Figure 10 shows a flowchart illustrating a method for suppressing common-mode noise in a differential data transmission system according to an embodiment of the disclosure. Fig. Figure 11 shows a flowchart illustrating a method for tuning a common-mode suppressor according to an embodiment of the disclosure, which includes a differential transmission line to achieve common-mode noise suppression.

[0005] The present disclosure will now be described with reference to the accompanying drawing figures, using the same reference symbols to denote identical elements throughout, and the structures and devices shown are not necessarily drawn to scale.

[0006] This disclosure relates to a device and a method for suppressing common-mode noise in differential data transmission systems. Differential data transmission systems use differential signaling, in which information is transmitted electrically using two complementary signals sent on two paired wires called a differential pair. Apart from the differential signal, which carries useful information, the differential pair is subject to common-mode noise. Common-mode noise is directed in the same direction on both wires and is the undesirable signal because it does not carry any information. Common-mode noise plays a significant role in generating radio-frequency interference (RFI) in communication systems that use differential transmission, so eliminating common-mode noise is important.Furthermore, the differential data transmission system is also exposed to ESD (electrostatic discharge) shocks, which must be avoided.

[0007] In one embodiment of the disclosure, a differential data transmission system comprises a source configured to transmit a differential signal containing data and a load configured to receive the differential signal. The system further comprises a common-mode suppressor comprising a long wound differential transmission line configured to transmit the differential signal from the source to the load.

[0008] In another embodiment of the disclosure, a common-mode suppressor for eliminating common-mode noise in high-frequency differential data transmission systems comprises a long differential data transmission line configured to transmit data between a source and a load. The differential transmission line is matched for differential signals and mismatched for common-mode noise. Furthermore, the differential transmission line is wound. A differential transmission line is matched if it exhibits low signal reflections, i.e., low loss at its input and output. Good matching typically means a return loss of at least -20 dB to -30 dB. In another embodiment of the disclosure, a method for suppressing common-mode noise in a differential data transmission system is disclosed.The method is operated in conjunction with a common-mode suppressor within the differential data transmission system. The common-mode suppressor comprises a long, wound differential transmission line configured to carry a signal from a source to a load. The differential transmission line further comprises a first conducting wire and a second conducting wire, which are coupled and aligned laterally or vertically to each other. The method involves matching the differential transmission line of the common-mode suppressor for differential signals, specifically tuning the differential impedance of the differential transmission line to match the load and source impedances.The method further includes mismatching the differential transmission line of the common-mode noise suppressor, wherein mismatching the differential transmission line for common-mode noise includes increasing the inductances of the differential transmission line for common-mode signals.

[0009] Common-mode noise elimination in differential-mode data transmission systems is achieved using a common-mode suppressor. A common-mode suppressor is a device configured to provide low impedance for differential-mode signals and high impedance for common-mode noise. In conventional systems, the common-mode suppressor is implemented using a common-mode choke concept. The common-mode choke consists of a pair of coupled inductors, providing low inductance for differential-mode signals and high impedance for common-mode signals. The key factor for a common-mode choke is the magnetic coupling between the two inductors. The higher the magnetic coupling, the better the common-mode rejection and the better the impedance matching for differential mode.

[0010] In one implementation, the common-mode choke comprises a magnetic core with two conducting wires wound with the same number of turns. In the case of a common-mode signal, the current flowing through the two conducting wires cancels each other out with opposite phases, thus generating no magnetic flux and keeping the impedance of the two conducting wires low. Therefore, differential signals can pass through easily. In the case of a common-mode signal, the current flows through the two conducting wires with the same phase, generating magnetic flux in the magnetic core and increasing the impedance of the two conducting wires, making it difficult for common-mode signals to pass through. Therefore, the common-mode signal is attenuated.However, common-mode chokes require the use of materials with ferromagnetic characteristics (e.g., magnetic bodies, ferrite cores), which makes them bulky and unsuitable for high-frequency applications. Furthermore, certain common-mode choke topologies exhibit high dispersion (non-constant group delay), which degrades their time-domain performance, rendering them unsuitable for high-speed interface applications such as USB, HDMI, etc. Additionally, conventional systems have relied on non-silicon solutions like varistors or spark gaps, which have clamping voltages that are too high for sensitive systems.

[0011] To create a common-mode suppressor suitable for high-frequency applications, a common-mode suppressor comprising a long wound transmission line is introduced in the present disclosure. In some implementations, this long wound transmission line replaces the common-mode choke used in conventional differential data transmission systems. In the present disclosure, a lumped system comprising the common-mode choke with coupled inductors is replaced by a distributed system comprising the long wound transmission line. The lumped-element model is only applicable if L C << λ, where L CLet denote the physical length of the circuit and λ the operating wavelength of the circuit. At high frequencies, the wavelengths of the signals in the circuit become comparable to the physical dimensions of the circuit elements, rendering the lumped model inaccurate. Therefore, instead of the coupled inductors in the present disclosure, the transmission line is used to make the common-mode suppressor suitable for high-frequency applications. For the distributed model to be applicable, the length of the transmission line should be at least one-tenth of the wavelength λ of the signals transmitted by the circuit within a predetermined frequency range of the differential signal. The predetermined frequency range includes frequencies at which the wavelengths of the signals transmitted by the circuit become comparable to the physical dimensions of the circuit elements.In an example, assuming an effective relative dielectric constant of at least 3 for the material between the coupled inductors, such that the wavelength of the electromagnetic waves, when compared to a vacuum, would be shortened by a factor of 1 divided by approximately the square root of 3, the length of the differential transmission line is 7 mm, which corresponds to about λ / 10 at approximately 2.5 GHz. Below, this frequency-concentrated element description suffices, and we can treat our differential transmission line as a pair of simple coupled inductors. Our suppressor will operate at frequencies up to 10 GHz, where the physical length of 7 mm corresponds to 0.4 λ (> λ / 10). Thus, we use a distributed element description, and we employ the doctrine of transmission lines to accurately model our suppressor for the frequency range above 2.5 GHz.Therefore, in this example, for the predetermined frequency range of 2.5 GHz to 10 GHz, the differential transmission line with a length of 7 mm can accurately model our common-mode suppressor. Furthermore, in this embodiment, replacing the common-mode choke with a long wound transmission line eliminates the need for ferromagnetic materials.

[0012] Fig. Figure 1 depicts a differential data transmission system 100 comprising a source circuit 101, a load circuit 103, and a common-mode suppressor 102 connected between the source circuit 101 and the load circuit 103. The differential data transmission system 100 is not a claimed embodiment in itself but is included for illustrative purposes. The source circuit 101 is configured to transmit information differentially using two coupled wires, and the load circuit 103 is configured to receive the differential signal transmitted by the source circuit 101. In one embodiment, the common-mode suppressor 102 comprises a long wound differential transmission line. The common-mode suppressor 102 is configured to suppress common-mode noise on the differential transmission line.The Differential Data Transmission System 100 can be part of any high-speed data communication system such as HDMI, USB, etc.

[0013] Apart from common-mode noise, differential data transmission systems are susceptible to ESD shocks. Fig. Figure 2 depicts a differential data transmission system 200 with an ESD protection circuit.

[0014] System 200 comprises a source circuit 201, a load circuit 204, and a common-mode suppressor 203. System 200 also includes an ESD protection circuit 202, which is connected to the input pins of the common-mode suppressor 203 and is configured to protect the differential data transmission system 200 from ESD shocks.

[0015] Fig. Figure 3 shows a particular embodiment in which a common-mode suppressor 300 comprises a long wound differential transmission line. The differential transmission line comprises a first conducting wire 301 and a second conducting wire 302, both of which are inductively and capacitively coupled to each other and are oriented vertically. The lines are intentionally coupled, both inductively and capacitively, to achieve a desired differential impedance Z. 0diff = √L / C. Coupling is achieved by adjusting the layout of the transmission lines so that the capacitance C between them and their inductances L equal the desired impedance Z. 0diff= √L / C. In other embodiments, the first conductive wire 301 and the second conductive wire 302 can be arranged laterally aligned with respect to each other. Furthermore, the differential transmission line comprises a first input pin 303 and a second input pin 304 on the input side of the first conductive wire 301 and the second conductive wire 302, respectively. In some embodiments, the input pins 303 and 304 are connected to an ESD protection circuit, and in other embodiments, the input pins 303 and 304 are directly connected to a source circuit. Furthermore, the differential transmission line comprises a first output pin 305 and a second output pin 306 on an output side of the first conductive wire 301 and the second conductive wire 302, respectively. The output pins 305 and 306 are connected to a load circuit.

[0016] In one embodiment, it shows Fig. Figure 4 describes the layout of a common-mode suppressor 400, comprising a first conductive wire 401 and a second conductive wire 402, which are inductively coupled and arranged laterally aligned with each other. Furthermore, the first conductive wire 401 includes a first input pin 403 and a first output pin 405, and the second conductive wire 402 includes a second input pin 404 and a second output pin 406. The common-mode suppressor 400 is configured to provide a low impedance for common-mode signals and a high impedance for common-mode noise. In particular, in this embodiment, the common-mode suppressor 400 is configured such that the first conductive wire 401 and the second conductive wire 402 are matched for differential signals and mismatched for common-mode signals.To provide impedance matching in differential mode, the differential impedance of the differential transmission line is tuned to match the load and source impedances so that the differential signals do not experience any impedance discontinuity. The signal at the input / output of the device must experience the same impedance as the transmission line along which it travels, i.e., no impedance discontinuity. The load and source impedances are usually equal, so they can be referred to as the system impedance. In one embodiment, the differential impedance is tuned to be equal to 100 ohms; however, in other embodiments, it could be different and is a function of the load and source impedances (i.e., the system impedance).In one embodiment, the differential impedance is adjusted by varying the cross-section of the first conducting wire 401 and the second conducting wire 402 and / or by varying the distance between the first conducting wire 401 and the second conducting wire 402.

[0017] Once differential matching is achieved, the transmission lines must be mismatched for common-mode noise. Common-mode differential mismatch is achieved by increasing the differential transmission line's impedance for common-mode signals. Specifically, in this embodiment, the differential transmission line's inductance is increased to raise the impedance for common-mode signals. Increasing the inductance of the differential transmission line for common-mode signals involves increasing the length of the differential transmission line comprising the first conducting wire 401 and the second conducting wire 402. However, simply increasing the length of the differential transmission line also increases its resistance for differential signals, which is undesirable.To increase the inductance of the differential transmission line without significantly increasing its resistance, the differential transmission line is wound, forming a coil and thus having multiple windings. Winding the transmission line increases its overall inductance, and therefore, with respect to common-mode signals, the transmission line behaves like a large inductor. The inductance increases with the number of windings in the coil.

[0018] Fig. Figure 4B shows an exploded view of the common-mode suppressor of Fig. 4A, which has a long wound differential transmission line. The winding of the differential transmission line does not affect the differential signals as long as the coupling between the different sections of the differential transmission line is negligible. On the other hand, the coupling between adjacent windings in the coil must be very high to create a high impedance for common-mode noise. For example, the conducting wires 401 and 402 in Fig. 4A one winding. Fig. Figure 4B shows two adjacent windings, winding 1 and winding 2 of the common-mode suppressor 400. Fig. 4A. The distance 409 represents the distance between winding 1 and winding 2. Winding 1 comprises a first section 401a of the first conducting wire 401 and a first section 402a of the second conducting wire 402 of the common-mode suppressor 400. Similarly, winding 2 comprises a second section 401b of the first conducting wire 401 and a second section 402b of the second conducting wire 402 of the common-mode suppressor 400. In order to create a high impedance for common-mode signals without affecting the differential signals, in one embodiment the distance 409 between windings 1 and 2 is made relatively larger compared to the distance 407 and 408 between the two conducting wires of winding 1 and winding 2, respectively.By reducing the distance between the windings 409, we increase the common-mode impedance and make the structure smaller (positive effect), but we increase the coupling between the two wound differential conductors (negative effect). The common-mode electromagnetic (EM) field is confined to the area between two conductors of a winding. If 407 is small relative to 409, no EM interaction will occur between windings in differential mode, if desired. On the other hand, if we make 409 too large, we decrease the common-mode impedance and increase the size of the structure, which is also undesirable. There is a trade-off between 407 and 409 that can be found by optimizing the layout using, for example, an EM simulator.

[0019] Fig. 5A and Fig. Figure 5B shows a common-mode suppressor 500 comprising a long wound differential transmission line on a semiconductor substrate. Fig. Figure 5A shows an embodiment in which the common-mode suppressor 500 comprises a first conductive wire 502 and a second conductive wire 504 which are inductively and capacitively coupled and which are aligned vertically to each other, according to the Fig. 3. 502a and 502b are two different sections of the first conducting wire 502, and 504a and 504b are two different sections of the second conducting wire 504. Furthermore, it shows Fig. 5A two adjacent windings, winding 1 and winding 2, wherein winding 1 comprises a first section 502a of the first conducting wire 502 and a first section 504a of the second conducting wire 504, and winding 2 comprises a second section 502b of the first conducting wire 502 and a second section 504b of the second conducting wire 504. The first conducting wire 502 is formed in the non-conducting layer 3 and the second conducting wire 504 in the non-conducting layer 2. To achieve the desired common-mode rejection without affecting the differential signals, the distance between the adjacent windings 506 is relatively larger than the distance 508 between the first conducting wire 502 and the second conducting wire 504.

[0020] Fig. Figure 5B shows another embodiment in which the common-mode suppressor 500 comprises a first conductive wire 522 and a second conductive wire 524 which are inductively and capacitively coupled and which are laterally aligned with each other, according to Fig. 4A. 522a and 522b are two different sections of the first conducting wire 522, and 524a and 524b are two different sections of the second conducting wire 524. Furthermore, it shows Fig. 5B two adjacent windings, winding 1 and winding 2, wherein winding 1 comprises a first section 522a of the first conducting wire 522 and a first section 524a of the second conducting wire 524, and winding 2 comprises a second section 522b of the first conducting wire 522 and a second section 524b of the second conducting wire 524. The first conducting wire 522 and the second conducting wire 524 are formed in the same non-conducting layer 2. In order to achieve the desired common-mode rejection without affecting the differential signals, the distance between the adjacent bonds 526 is proportionally larger than the distance 528 between the first conducting wire 522 and the second conducting wire 524.

[0021] Fig. Figures 6A-6D show the simulation results for the differential mode and common-mode operation of a common-mode suppressor with the differential impedance of the differential transmission line, where the differential impedance of the differential transmission line is designed to match a system impedance of 100 ohms. Each graph shows the variation of the S-parameter coefficients in the frequency range of 0-25 GHz. Scattering parameters, or S-parameters, describe the electrical behavior of linear electrical networks when subjected to various constant-state stimuli from electrical signals. In particular, S-parameters specify the ratio between the incident power and the reflected power. For a two-terminal device, there are four S-parameters: S11, S21, S12, and S22.S11 and S22 are the coefficients for forward direction and backward reflection, and S12 and S21 represent the forward transfer coefficient and the backward transfer coefficient. Based on . Fig. 6A and Fig. Figure 6D shows that for frequencies between 0 GHz and 15 GHz, the forward reflection coefficient S11 for common-mode signals 601 and the backward reflection coefficient S22 for the common-mode signal 607 are 0 dB (i.e., full reflection), indicating very high reflection for common-mode signals. Furthermore, the forward reflection coefficient S11 for the differential-mode signal 602 and the backward reflection coefficient S22 for the common-mode signal 608 are approximately -20 dB, indicating very low reflection for differential signals. Additionally, one can see from the Fig. 6B and Fig. 6C sees that for the frequency range 0-15 GHz, the forward transfer coefficient S12 for the differential signal 603 and the reverse transfer coefficient S21 for the differential signal 605 are almost 0 dB (i.e., full transmission), indicating that there is very good transmission of differential signals; and the forward transfer coefficient S12 for the common-mode signal 604 and the reverse transfer coefficient S21 for the common-mode signal 606 are much less than 0 dB, in particular about -35 dB for the frequency range of 10-15 GHz, indicating that there is very weak transmission of common-mode signals through the system.

[0022] ESD protection circuit 202 in front of the common-mode suppressor 203 in Fig. 2 weakens the characteristics of the common-mode suppressor 203 due to parasitic capacitances of the ESD diodes within 202. Therefore, we must compensate for these capacitances. Fig. 7A represents a possible PI circuit used to provide ESD protection and compensate for the unwanted capacitance of the ESD diodes. ESD devices ESD1 - ESD4 in Fig. 7A are used to model ESD diodes. In one embodiment, they form Fig. 7A includes an ESD protection circuit 701, which is associated with a common-mode suppressor 702 and is connected to the input side of the common-mode suppressor 702 via input pins 703 and 704. The ESD protection circuit 701 is configured to protect a differential data transmission system from ESD shocks. Specifically, a first ESD device 707, connected between a first input pin 703 of the common-mode suppressor 702 and ground, and a second ESD device 708, connected between a second input pin 704 of the common-mode suppressor 702 and ground, are configured to provide ESD protection. In some embodiments, the ESD protection circuit 701 further comprises a third ESD device 709 which is connected between the first input pin 703 and earth, and a terminal end of the first ESD device 707 and the third ESD device 709 opposite earth have an inductor 711 connected between them.The third ESD device 709 and the inductor 711 compensate for the parasitic capacitance of the first ESD device 707. The ESD protection circuit 701 also includes a fourth ESD device 710, which is connected between the second input pin 704 and ground. One terminal of the second ESD device 708 and the fourth ESD device 710, opposite ground, have an inductor 712 connected between them. The fourth ESD device 710 and the inductor 712 compensate for the parasitic capacitance of the second ESD device 708. Fig. In embodiment 7A, ESD devices 707 and 708 provide ESD protection; however, in other embodiments, ESD devices 709 and 710 may be configured to provide ESD protection. In both embodiments, the ESD devices providing ESD protection must be ESD diodes. In some embodiments, the third ESD device 709, configured to compensate for the parasitic capacitance of the first ESD device 707, is modeled as a capacitor with a capacitance value equal to the parasitic capacitance of the first ESD device 707. Similarly, the fourth ESD device, configured to compensate for the parasitic capacitance of the second ESD device 708, is modeled as a capacitor with a capacitance value equal to the parasitic capacitance of the second ESD device 707. Fig. Figure 7B shows the layout of the common-mode suppressor with the ESD protection circuit 700 from Fig. 7A.

[0023] Fig. 8A, Fig. 8B and Fig. Figure 8C shows the simulation results for the differential mode of a common-mode suppressor with ESD protection, where the differential impedance of the differential transmission line is designed to match a system impedance of 100 ohms. Each graph shows the variation of S-parameter coefficients in the frequency range of 0–25 GHz. The analysis of the graphs can be performed in a similar manner to that of Fig. 6A - 6D. Based on Fig. 8A, Fig. 8B and Fig. 8C, in particular based on Fig. Figure 8B, which shows the variation of the forward transmission power S12 of differential signals over a frequency range, clearly shows that the differential signals are transmitted through the system with much lower reflection for the frequency range 1-15 GHz. However, this behavior is different compared to the simulation results of the common-mode suppressor without ESD protection in Fig. 6A to 6D deteriorate, and this is due to the parasites of the ESD diodes. Similarly, they show Fig. 8D, Fig. 8E and Fig. Figure 8F presents the simulation results for common-mode operation of a common-mode suppressor with ESD protection, where the differential impedance of the differential transmission line is designed to match a system impedance of 100 ohms. Each graph shows the variation of S-parameter coefficients in the frequency range of 0–25 GHz. Based on Fig. 8D, Fig. 8E and Fig. 8F, in particular based on Fig. Figure 8E, which shows the variation of the forward transmission parameter S12 of the common-mode signals over a frequency range, clearly shows that there is very good common-mode rejection over the frequency range of 0-15 GHz, and that very little common-mode noise enters the system.

[0024] Fig. Figure 9A shows the time-domain analysis for a 5 GB / s signal, according to one embodiment of the disclosure. The graph shows the time-domain representation of an input signal 950 and an output signal 952 in a USB. The output signal clearly exhibits little distortion compared to the input signal, and this shows that the system has very good time-domain performance. Similarly, Figure 9A shows that... Fig. 9B The time-domain analysis for a 10 GB / s signal, according to an embodiment of the disclosure. The graph shows the time-domain representation of an input signal 960 and an output signal 962 in a USB. The output signal clearly exhibits no significant distortion compared to the input signal, demonstrating that the system has very good time-domain performance.

[0025] Fig. Section 10 presents a method 1000 for suppressing common-mode noise in a differential data transmission system. In section 1002, a first transmission line is provided to transmit a first section of a differential signal from a source to a load, wherein the length of the first conducting wire is greater than one-tenth of the wavelength of the differential signal transmitted through the first conducting wire.

[0026] At block 1004, a second conducting wire is provided to transmit a second portion of the differential signal from the source to the load, the length of which is greater than one-tenth of the wavelength of the differential signal carried by the second transmission line. At block 1006, the first and second conducting wires are wound together to form a wound differential transmission line with multiple windings, such that the spacing between adjacent windings of the wound differential transmission line is greater than the spacing between the first and second conducting wires.

[0027] Fig. Figure 11 presents an exemplary implementation of a method for tuning a differential transmission line in order to suppress common-mode noise. The method 1100 is described here with reference to the common-mode suppressor 300. Fig. 3 described.

[0028] In block 1101, the differential impedance of a differential transmission line is adjusted to match the system impedance. This involves varying the cross-sectional area of ​​the first conductor 301 and the second conductor 302, and / or varying the distance between the first conductor 301 and the second conductor 302. In block 1102, the differential impedance of the differential transmission line is compared to the system impedance. If the differential impedance matches the system impedance (YES at 1102), the procedure proceeds to block 1103; otherwise (NO at 1102), the procedure returns to block 1101, where the differential impedance of the differential transmission line is adjusted again. In block 1103, the common-mode inductance of the differential transmission line is increased.The length of the differential transmission line, which includes the first conducting wire 301 and the second conducting wire 302, is increased, and then the differential transmission line is wound. At block 1104, the common-mode impedance of the differential transmission line is checked. If the impedance is high (YES at 1104), the procedure proceeds to 1105, where it ends. Otherwise (NO at 1104), the procedure returns to block 1103, further increasing the common-mode inductance of the differential transmission line.

[0029] While the procedures below are presented and described as a series of actions or events, it should be understood that the presented sequence of such actions or events should not be interpreted in a restrictive sense. For example, some actions may occur in other sequences and / or concurrently with other actions or events, independent of those presented and / or described herein. Furthermore, not all of the presented actions need be required to implement one or more aspects or embodiments of the disclosure herein. Also, one or more of the actions depicted herein may be carried out in one or more separate actions and / or phases.

[0030] As emphasized above, the common-mode suppressor based on differential transmission lines differs advantageously from conventional common-mode suppressors based on the common-mode choke concept. The differential-transmission line-based common-mode suppressor eliminates the need for magnetic materials because the new concept does not require significant magnetic coupling. Furthermore, this suppressor achieves excellent time-domain performance, suitable for high-speed interface applications (such as USB and HDMI), and also provides very wideband common-mode attenuation above 6 GHz. Additionally, the differential-transmission line-based common-mode suppressor can be implemented using readily available technologies.

[0031] In a first respect, the invention comprises a differential data transmission system. The differential data transmission system includes a source configured to transmit a differential signal containing data, a load configured to receive the differential signal, and a common-mode suppressor. The common-mode suppressor comprises a long, coiled differential transmission line configured to transmit the differential signal from the source to the load. In some embodiments, the length of the differential transmission line is at least one-tenth the wavelength of the differential signal, which is transmitted through the differential transmission lines within a predetermined operating frequency range of the differential signal.

[0032] In some embodiments, the differential transmission line comprises a first conducting wire and a second conducting wire that are inductively and capacitively coupled to each other. In some embodiments, the first conducting wire and the second conducting wire are arranged vertically aligned with each other. In some embodiments, the first conducting wire and the second conducting wire are arranged laterally aligned with each other. In some embodiments, the distance between adjacent windings of the wound differential transmission line is greater than the distance between the first conducting wire and the second conducting wire of the differential transmission line.

[0033] Some embodiments of the transmission system according to the invention in the first respect further comprise an electrostatic discharge (ESD) protection circuit connected to the first and second input pins of the common-mode suppressor and configured to provide protection against electrostatic discharge shocks. In some embodiments, the ESD protection circuit comprises a first ESD device connected between the first input pin of the common-mode suppressor and ground, and a second ESD device connected between the second input pin of the common-mode suppressor and ground, wherein the first ESD device and the second ESD device have the same value.

[0034] Some embodiments of the transmission system according to the invention in the first respect comprise a third ESD device connected between the first input pin and ground, wherein a terminal end of the first and the third ESD device has an interposed inductor connected to ground to compensate for a parasitic capacitance of the first ESD device. Some embodiments of the transmission system according to the invention in the first respect further comprise a fourth ESD device connected between the second input pin and ground, wherein a terminal end of the second and the fourth ESD device has an interposed inductor connected to ground to compensate for a parasitic capacitance of the second ESD device, and wherein the third and fourth ESD devices have the same inductance value.

[0035] In a second respect, the invention comprises a common-mode suppressor for eliminating common-mode noise in differential high-frequency data transmission systems. The common-mode suppressor comprises a long wound differential transmission line configured to transmit data between a source and a load. Some embodiments of the common-mode suppressor according to the invention in the second respect include one or more cross-sections of a first conductive wire and a second conductive wire of the differential transmission line, and a spacing between the first conductive wire and the second conductive wire of the differential transmission line, being configured to provide a differential impedance of the differential transmission line that matches a system impedance.

[0036] The differential transmission line is configured to be mismatched with respect to common-mode noise. The length of the differential transmission line is at least one-tenth the wavelength of a signal transmitted through the differential transmission line within a predetermined operating frequency range.

[0037] In some embodiments, the first and second wires are inductively and capacitively coupled. In some embodiments, the first and second conducting wires are arranged vertically aligned with each other. In some embodiments, the first and second conducting wires are arranged laterally aligned with each other. In some embodiments, the distance between adjacent windings of the wound differential transmission line is greater than the distance between the first and second conducting wires of the differential transmission line.

[0038] Some embodiments of the common-mode suppressor according to the invention in the second respect further comprise an electrostatic discharge (ESD) protection circuit connected to the first and second input pins of the common-mode suppressor and configured to provide protection against ESD shocks. Some embodiments of the common-mode suppressor according to the invention in the second respect further comprise a first ESD device connected between the first input pin of the common-mode suppressor and ground, and a second ESD device connected between the second input pin of the common-mode suppressor and ground, wherein the first ESD device and the second ESD device have the same value.

[0039] Some embodiments of the common-mode suppressor according to the invention in the second respect further comprise a third ESD device connected between the first input pin and ground, wherein a terminal end of the first and the third ESD device is connected to ground via an inductor to compensate for a parasitic capacitance of the first ESD device. Some embodiments of the common-mode suppressor according to the invention in the second respect further comprise a fourth ESD device connected between the second input pin and ground, wherein a terminal end of the second and the fourth ESD device has an intervening inductor connected to ground to compensate for a parasitic capacitance of the second ESD device, and wherein the third and fourth ESD devices have the same inductance value.

[0040] In a third respect, the invention comprises a method for suppressing common-mode noise in a differential transmission system. The method comprises providing a first conducting wire to transmit a first portion of a differential signal from a source to a load, and providing a second conducting wire to transmit a second portion of the differential signal from the source to the load. The method further comprises winding the first and second conducting wires. The first and second wound conducting wires together form a wound differential transmission line having multiple windings. In some implementations, the spacing between adjacent windings of the wound transmission line is greater than the spacing between the first and second conducting wires.In some implementations, the length of the wound differential transmission line is greater than one tenth of the wavelength of a differential signal that is transmitted through the wound differential transmission line in a predetermined operating frequency range of the differential signal.

[0041] In some embodiments, the first conducting wire and the second conducting wire are inductively and capacitively coupled to each other.

[0042] In some embodiments, the first conducting wire and the second conducting wire have a cross-sectional area assigned to them, and the distance from the first conducting wire to the second conducting wire and the cross-sectional area of ​​the first conducting wire and the second conducting wire are configured such that a differential impedance of the first conducting wire and the second conducting wire is matched to a system impedance.

[0043] In some embodiments, the number of windings of the wound differential transmission line and the length of the wound differential transmission line are configured such that the wound differential transmission line is mismatched for common-mode noise.

[0044] While the invention has been presented and described with respect to one or more implementations, changes and / or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In particular, with regard to the various functions performed by the components or structures (arrangements, devices, circuits, systems, etc.) described above, the terms (including any reference to a "means") used to describe such components shall correspond to any component or structure that performs the specified function of the described component (for example, that is functionally equivalent), even if it is not structurally equivalent to the disclosed structure that performs the function in the exemplary implementation of the invention presented herein.

Claims

[1] A differential data transmission system (200; 700), comprising: a source (201) configured to transmit a differential signal containing data; a load (204) configured to receive the differential signal; and a common-mode suppressor (300; 400; 500; 702) comprising a long, wound differential transmission line configured to carry the differential signal from the source to the load; wherein a length of the differential transmission line is at least greater than one tenth of the wavelength of the differential signal, which is transmitted through the differential transmission lines in a predetermined operating frequency range of the differential signal, further comprising a protection circuit (202; 701) against electrostatic discharges, which is connected to the first (303; 703) and second (304; 704) input pins of the common-mode suppressor (300; 400; 500; 702) and which is configured to provide protection against shocks from electrostatic discharge. [2] The differential data transmission system (200; 700) according to claim 1, wherein the differential transmission line has a first conductive wire (502) and a second conductive wire (504) which are inductively and capacitively coupled to each other and which are arranged in a vertical alignment with each other. [3] The differential data transmission system (200; 700) according to claim 1, wherein the differential transmission line has a first conductive wire (301; 401; 522) and a second conductive wire (302; 402; 524) which are inductively and capacitively coupled to each other and which are arranged laterally aligned to each other. [4] The differential data transmission system (200; 700) according to claim 2, wherein a distance (506) between adjacent windings of the wound differential transmission line is greater than a distance (508) between the first wound wire (502) and the second wound wire (504) of the differential transmission line. [5] The differential data transmission system (200; 700) according to any one of claims 1 to 4, wherein the protection circuit (202; 701) against electrostatic discharges comprises a first ESD device (707) connected between the first input pin (303; 703) of the common-mode suppressor (300; 400; 500; 702) and an earth, and a second ESD device (708) connected between the second input pin (704) of the common-mode suppressor (300; 400; 500; 702) and an earth, wherein the first ESD device (707) and the second ESD device (708) have the same value. [6] A common-mode suppressor (300; 400; 500; 702) for eliminating common-mode noise in differential radio frequency data transmission systems, comprising: a long wound differential transmission line configured to transmit data between a source (201) and a load (204); wherein one or more cross-sections of a first conducting wire (301; 401; 502; 522) and a second conducting wire (302; 402; 504; 524) of the differential transmission line and a distance (508, 526) between the first conducting wire (301; 401; 502; 522) and the second conducting wire (302; 402; 504; 524) of the differential transmission line are configured to give a differential impedance of the differential transmission line that matches a system impedance; and wherein a length and a wound arrangement of the differential transmission line is configured to result in the differential transmission line being mismatched with respect to common-mode noise; wherein the length of the differential transmission lines is at least greater than one tenth of the wavelength of a signal that is transmitted through the differential transmission lines in a predetermined operating frequency range of the signal, further comprising a protection circuit (202; 701) against electrostatic discharges, which is connected to the first (303; 703) and second (304; 704) input pins of the long wound differential transmission line and which is configured to provide protection against electrostatic discharge shocks. [7] A method (1000; 1100) for suppressing common-mode noise in a differential transmission line system, comprising: Providing a first conductive wire (301; 401; 502; 522) to transmit a first section of a differential signal from a source (201) to a load (204); Providing a second conductive wire (302; 402; 504; 524) to transmit a second section of the differential signal from the source (201) to the load (204); Winding the first conductive wire (301; 401; 502; 522) and the second conductive wire (302; 402; 504; 524); wherein the first (301; 401; 502; 522) and the second (302; 402; 504; 524) conducting wire together form a wound differential transmission line having multiple windings; wherein a distance (506; 526) between adjacent windings of the wound transmission line is greater than the distance (508; 528) between the first conducting wire (301; 401; 502; 522) and the second conducting wire (302; 402; 504; 524); and wherein a length of the wound differential transmission line is greater than one tenth of the wavelength of a differential signal that is transmitted through the wound differential transmission line at a predetermined operating frequency range of the differential signal, furthermore, comprehensively providing protection against electrostatic discharge shocks by means of a protective circuit (202; 701) against electrostatic discharges, which is connected to the first (303; 703) and second (304; 704) input pins of the wound differential transmission line. [8] The method (1000; 1100) according to claim 7, wherein the first conducting wire (301; 401; 502; 522) and the second conducting wire (302; 402; 504; 524) are inductively and capacitively coupled to each other. [9] The method (1000; 1100) according to claim 7 or 8, wherein the first conducting wire (301; 401; 502; 522) and the second conducting wire (302; 402; 504; 524) have a cross-sectional area assigned to them, and wherein the distance (508; 528) from the first conducting wire (301; 401; 502; 522) to the second conducting wire (302; 402; 504; 524) and the cross-sectional area of ​​the first conducting wire (301; 401; 502; 522) and the second conducting wire (302; 402; 504; 524) are configured such that a differential impedance of the first conducting wire (301; 401; 502; 522) and of the second conducting wire (302; 402; 504; 524) matches a system impedance. [10] The method (1000; 1100) according to one of claims 7 to 9, wherein the number of windings of the wound differential transmission line and the length of the wound differential transmission line are configured such that the wound differential transmission line is mismatched for common-mode noise.

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