CN108666722B - High-frequency differential signal transmission line and signal transmission system - Google Patents
High-frequency differential signal transmission line and signal transmission system Download PDFInfo
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- CN108666722B CN108666722B CN201810178760.XA CN201810178760A CN108666722B CN 108666722 B CN108666722 B CN 108666722B CN 201810178760 A CN201810178760 A CN 201810178760A CN 108666722 B CN108666722 B CN 108666722B
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- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P3/00—Waveguides; Transmission lines of the waveguide type
- H01P3/003—Coplanar lines
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- H—ELECTRICITY
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- H01P3/02—Waveguides; Transmission lines of the waveguide type with two longitudinal conductors
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- H—ELECTRICITY
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- H03F—AMPLIFIERS
- H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
- H03F3/45—Differential amplifiers
- H03F3/45071—Differential amplifiers with semiconductor devices only
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
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- H03K19/00—Logic circuits, i.e. having at least two inputs acting on one output; Inverting circuits
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Abstract
The high-frequency differential signal transmission line of the present invention includes: signal conductors (11, 12) for propagating differential signals; and ground conductors (13, 14) respectively formed on both sides of the signal conductors (11, 12), to which a differential signal is inputted from one ends (11a, 12a) of the signal conductors (11, 12), the other ends (11b, 12b) of the signal conductors (11, 12) being terminated by termination circuits (15, 16), and which give and receive the differential signal to and from differential input terminals (21a, 21b) of the differential circuit (21), the width (S) of the signal conductor (11) and the width (S) of the signal conductor (12) being equal, the interval between the signal conductor (11) and the ground conductor (13) being equal to the interval W between the signal conductor (12) and the ground conductor (14), and the interval d and the interval W between the signal conductors (11, 12) being 0.1 < (d/2-W)/(d/2+ W) < 1.
Description
Technical Field
The present invention relates to a technique for improving a problem of deterioration in reflection characteristics or generation of electromagnetic interference due to phase deviation of a differential signal in a differential signal transmission line which has a differential circuit having a pair of differential terminals for inputting and outputting the differential signal and is formed on a substrate and which transmits and receives the differential signal to and from the differential circuit.
Background
In a circuit that performs amplification processing, latch processing, or the like of a high-frequency signal of several GHz or more, differential signals having mutually opposite phases are generally used, and a differential circuit that amplifies or latches the differential signals includes a differential input terminal and a differential output terminal as a pair of differential terminals.
When a differential circuit that processes a differential signal in this manner is formed on a semiconductor substrate by an Integrated Circuit (IC) technique, a differential signal transmission line is used as a transmission path for the differential circuit to transmit and receive a differential signal to and from another circuit or a terminal formed on the semiconductor substrate. The differential signal transmission line is formed on the semiconductor substrate together with the differential circuit, and is electrically connected to a differential input terminal or a differential output terminal of the differential circuit. The differential signal transmission line is required to have a characteristic of being able to transmit the differential signal input/output from the differential circuit to a wide band with low reflection and low loss.
For example, as a circuit for performing amplification processing or latch processing on a wide frequency band using a differential signal transmission line, there is a differential distributed amplifier or a distributed logic circuit (see, for example, patent documents 1 and 2). These are structures in which the differential input/output terminals of a plurality of differential circuits formed at predetermined intervals on a substrate are connected in parallel to a differential signal transmission line, and the inductance component of the differential signal transmission line and the input/output capacitance of the differential circuit are designed to be equivalent to form a high-cutoff analog distributed constant line, so that the transmission of a differential signal to the plurality of differential circuits can be performed over a wide frequency band, and high-speed operation can be achieved.
As a differential signal transmission line formed on a semiconductor substrate, a balanced line having a structure in which a pair of symmetrical signal conductors 61 and 62 are arranged in parallel at a constant interval d on a semiconductor substrate as shown in fig. 18(a) is generally used. Fig. 18(b) shows a schematic diagram of a cross section of a pair of signal conductors 61 and 62 of a balanced line formed on a semiconductor substrate sufficiently thicker than the interval d, and a case of an electric power line at the time of differential signal transmission (odd mode). In the balanced line, since the pair of signal conductors are electromagnetically strongly coupled to each other, when differential signals (V (+), V (-) with opposite polarities are transmitted to the pair of signal conductors 61, 62 as shown in the figure, an electric field is strongly distributed between the signal conductors. In an ideal balanced line, a symmetric differential mode transmission is maintained between a pair of signal conductors, and a differential signal can be transmitted to a wide band with low reflection and low loss.
When a plurality of differential circuits are formed on a semiconductor substrate together with the balanced line, a power supply conductor or a ground conductor for applying a bias voltage to the plurality of circuits must be formed on the same substrate. When the ground conductors are irregularly present around the pair of signal conductors constituting the balanced line, the electrical symmetry of the pair of signal conductors is disturbed, and the transmission quality is deteriorated, but as shown in fig. 19(a), the ground conductors 63 and 64 are symmetrically arranged on the sides of the pair of signal conductors 61 and 62 along the pair of signal conductors, so that the electrical symmetry can be maintained and the good transmission quality can be maintained. The transmission line of such a structure is also referred to as Edge-Coupled CPW (hereinafter, also referred to as "ECCPW"). (for example, refer to non-patent document 1). Fig. 19(b) shows a schematic diagram of a cross section of an ECCPW formed on a sufficiently thick semiconductor substrate, and a case of an electric line during differential signal transmission. As shown in the drawing, the electric field is strongly distributed between the signal conductors 61 and 62, but also between the signal conductors 61 and 62 and the side ground conductors 63 and 64, as in the case of a normal balanced line.
However, in a balanced line formed on a semiconductor substrate together with a differential circuit in an actual IC, a signal conductor is arranged between a plurality of circuits or terminals in a complicated manner and is electrically connected to a plurality of differential circuits, and therefore, a bent portion is provided or branch wirings having different lengths are connected to the differential circuits. These bent portions or branch wirings of different lengths deteriorate the transmission quality of the differential signal in the balanced line.
The mechanism of deterioration of transmission quality is as follows. For example, as shown in fig. 20, when there are 1 90 ° bent portions in the balanced line, a difference of 2 × d physical length occurs between the pair of signal conductors 61 and 62.
As shown in fig. 21, in the configuration in which the differential input terminals 65a and 65b of the differential circuit 65 disposed on the side of the balanced line and the balanced line are connected by the branch lines 66a and 66b, a difference corresponding to d occurs in the length of the branch lines 66a and 66 b. In a real wiring layout of an IC, when the length of the branch wirings 66a and 66b is in the range of 1/10 or less (several hundred μm or less) of the wavelength λ of the frequency to be processed (for example, several tens of GHz), and further, when the input impedance of the differential circuit 65 is assumed to be sufficiently high, it is considered that the branch wirings 66a and 66b function as capacitors due to the characteristics of open stubs.
In an open stub having a length of wavelength λ/10 or less, which functions as a capacitor, the capacitance increases as the stub length increases, and therefore the magnitude of the capacitance added to the pair of signal conductors 61 and 62 varies depending on the conductor length difference d between the branch wirings 66a and 66 b. A phase deviation (skew) is generated between the differential signals (between the positive phase signal V (+) and the negative phase signal V (-)) according to the difference between the above-described physical lengths or the magnitude of the attached capacitances to generate a common mode component. In the case of a line in which electromagnetic coupling between a pair of signal conductors is strong, such as a balanced line, the characteristic impedance of the common mode (even mode) becomes large, and therefore the characteristic impedance becomes mismatched with respect to the common mode component due to phase deviation, and the reflection characteristic deteriorates. And, thereby, also causes a problem of generating unnecessary electromagnetic radiation interference.
The phase shift is caused by an asymmetric structure inside the IC, but may be caused by factors outside the IC. That is, in a signal transmission system having a structure in which a differential signal input to an input portion of an IC passes through a transmission medium such as an external coaxial cable, a connector, or a bonding wire, a phase shift may occur between the differential signals due to a difference in length between the coaxial cable and the connector. At this time, there is already a phase deviation at the time point when the differential signal is input to the IC.
[ patent document 1] Japanese patent application laid-open No. 2006-
[ patent document 2] Japanese patent No. 3293091 publication
[ non-patent document 1] P.Thiiruvar Selvan and S.Raghavan, "Multilayer Perceptron Neural analysis of EdgecolledleedConductor-Backed Edge Coupled copalar Waveguides", Progress In electromagnetic Research B, Vol.17,169-185,2009.
In general, in order to eliminate the influence of phase deviation of differential signals, it is effective to use an unbalanced line such as a CPW (coplanar line) or a microstrip line as a transmission line formed on a semiconductor substrate. Since the unbalanced line has a large electromagnetic coupling with the ground and there is almost no electromagnetic coupling between the 2 signal conductors transmitting the differential signal, the characteristic impedance to the common mode does not become large and deterioration of the reflection characteristic due to phase deviation does not occur. However, the CPW requires a ground conductor to be provided between a pair of signal conductors, and has a problem that the area of the entire transmission line increases. On the other hand, in the microstrip line, a signal conductor and a ground conductor (GND plane) facing the signal conductor can be formed by 2 layers of conductors sandwiched by insulating layers on the IC surface, but in order to obtain high characteristic impedance of 50 Ω or more, for example, it is necessary to form the insulating layers sandwiching the 2 layers of conductors to have a thickness of several μm or more in order to reduce a capacitance component between the signal conductor and the GND plane, which causes a problem that the IC manufacturing process becomes complicated.
Disclosure of Invention
The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a high-frequency differential signal transmission line and a signal transmission system including the high-frequency differential signal transmission line, which are capable of preventing deterioration in reflection characteristics and occurrence of unnecessary electromagnetic interference due to phase deviation between differential signals caused by complicated arrangement of signal conductors formed on a substrate and which are small in area and excellent in manufacturability.
In order to solve the above problem, a high-frequency differential signal transmission line according to the present invention includes:
a substrate; a pair of signal conductors formed on the substrate and used for transmitting differential signals; and a 1 st ground conductor and a 2 nd ground conductor formed on both sides of the pair of signal conductors on the substrate, respectively, one ends of the pair of signal conductors being inputted with and outputted from a differential signal, the other ends of the pair of signal conductors being terminated by a termination circuit and transmitting and receiving the differential signal to and from a pair of differential terminals of a differential circuit formed on the substrate, wherein the pair of signal conductors are composed of a 1 st signal conductor and a 2 nd signal conductor, a width of the 1 st signal conductor is equal to a width of the 2 nd signal conductor, an interval between the 1 st signal conductor and the 1 st ground conductor arranged on a side thereof is equal to an interval between the 2 nd signal conductor and the 2 nd ground conductor arranged on a side thereof, and the high-frequency differential signal transmission line is characterized in that, has the following structure: when the distance is W and the distance between the 1 st signal conductor and the 2 nd signal conductor is d, 0.1 < (d/2-W)/(d/2+ W) < 1 is obtained.
With this configuration, the high-frequency differential signal transmission line according to the present invention is configured such that the pair of signal conductors constituting the balanced line are arranged close to the ground conductors formed on the respective sides, and therefore, although the balanced line is used, the unbalanced line has strong properties and is less susceptible to phase deviation between differential signals.
Further, the high-frequency differential signal transmission line according to the present invention can prevent the deterioration of reflection characteristics and the occurrence of unnecessary electromagnetic interference due to phase deviation between differential signals caused by complicated arrangement of signal conductors formed on a substrate, and can realize a small-area differential signal transmission line with good manufacturability.
Further, the high-frequency differential signal transmission line according to the present invention can easily realize a high characteristic impedance of 50 Ω or more, and thus can constitute a differential distributed amplifier or a distributed logic circuit with a high degree of freedom in design.
In the differential signal transmission line configured as described above, when the differential circuit is formed on the side of the 1 st signal conductor, the differential signal transmission line may further include: a branch wiring connected to the 2 nd signal conductor at one of the pair of differential terminals; and a cross section where the branch wiring and the 1 st signal conductor cross each other with an insulating layer interposed therebetween. Alternatively, the differential circuit may be formed on a side of the 2 nd signal conductor, and further include: a branch wiring connecting the 1 st signal conductor to one of the pair of differential terminals; and a cross section where the branch wiring and the 2 nd signal conductor cross each other with an insulating layer interposed therebetween.
With this configuration, in the high-frequency differential signal transmission line according to the present invention, the differential circuit can be disposed laterally to the pair of signal conductors via the branch wiring.
In the high-frequency differential signal transmission line configured as described above, the pair of signal conductors may have a bent portion.
With this configuration, in the high-frequency differential signal transmission line according to the present invention, the signal conductor length can be secured long within the limited size of the substrate, and therefore, more differential circuits can be arranged on the sides of the pair of signal conductors.
In the differential signal transmission line having the above configuration, the distance between the pair of signal conductors in the bent portion may be narrower than the distance between the pair of signal conductors before and after the bent portion.
In the high-frequency differential signal transmission line configured as described above, the distance between the pair of signal conductors in the connection portion to which the branch wiring is connected may be narrower than the distance between the pair of signal conductors before and after the connection portion.
With these configurations, in the high-frequency differential signal transmission line according to the present invention, it is possible to suppress the amount of phase deviation occurring between the transmitted differential signals, and to suppress the characteristic degradation of the differential circuit or other transmission lines to which the differential signals are input.
In the high-frequency differential signal transmission line having the above-described structure, the substrate may be a semiconductor substrate made of InP, GaAs, or Si.
In the high-frequency differential signal transmission line configured as described above, a plurality of the differential circuits may be formed on the substrate, and the differential signal may be transmitted and received to and from a pair of differential terminals of the plurality of the differential circuits.
With this configuration, a differential distributed amplifier or a distributed logic circuit including a plurality of differential circuits can be configured by using the high-frequency differential signal transmission line according to the present invention.
In the high-frequency differential signal transmission line configured as described above, which transmits and receives differential signals to and from the plurality of differential circuits, the following may be implemented: the pair of differential terminals of at least 1 of the differential circuits is a pair of differential input terminals for signal input, and the pair of differential terminals of at least another one of the differential circuits is a pair of differential output terminals for signal output.
With this configuration, the differential signals processed and output by the plurality of differential circuits can be input to the plurality of differential circuits by using the high-frequency differential signal transmission line according to the present invention, and thus complicated processing of the differential signals can be performed.
In order to solve the above problem, a signal transmission system according to the present invention includes the differential signal transmission line for high frequency having the above-described configuration, the substrate, a signal generating device that generates the differential signal, and a transmission medium that transmits the differential signal, wherein the signal generating device and the transmission medium are provided outside the substrate, and the differential signal is input to the one end of the pair of signal conductors.
That is, a signal transmission system that transmits a differential signal and performs amplification processing or latch processing can be configured by an IC including the high-frequency differential signal transmission line having the above-described configuration, a signal generation device provided outside the IC, and a transmission medium that transmits the differential signal generated by the signal generation device to the IC.
With this configuration, even if a phase shift occurs between differential signals due to a difference in length between coaxial cables, connectors, bonding wires, and the like outside the IC, it is possible to suppress deterioration in reflection characteristics of the differential signals transmitted inside the IC, and realize a signal transmission system that operates with high quality and high stability.
Effects of the invention
The present invention provides a high-frequency differential signal transmission line and a signal transmission system including the same, which are small in area and excellent in manufacturability, and which can prevent deterioration in reflection characteristics and generation of unnecessary electromagnetic interference due to phase deviation between differential signals caused by complicated arrangement of signal conductors formed on a substrate.
Drawings
Fig. 1 is a plan view showing a structure of a differential signal transmission line according to embodiment 1 on a differential input terminal side.
Fig. 2 is a sectional view taken along line a-a of fig. 1.
Fig. 3 is a cross-sectional view showing a structural example of the intersection.
In fig. 4, fig. 4(a) is a plan view showing a configuration in which a plurality of differential circuits are arranged only on the side of either one of a pair of signal conductors, and fig. 4(b) is a plan view showing a configuration in which a plurality of differential circuits are arranged on the side of both of a pair of signal conductors.
In fig. 5, fig. 5(a) is a plan view showing a structure in which the differential circuit and the branch line are disposed below the ground conductor, fig. 5(b) is a cross-sectional view showing a cross-sectional structure including the 1 st branch line, and fig. 5(c) is a cross-sectional view showing a cross-sectional structure including the 2 nd branch line.
In fig. 6, fig. 6(a) is a plan view showing another structure in which the differential circuit and the branch line are disposed below the ground conductor, fig. 6(b) is a cross-sectional view showing a cross-sectional structure including the 1 st branch line, and fig. 6(c) is a cross-sectional view showing a cross-sectional structure including the 2 nd branch line.
In fig. 7, fig. 7(a) is a plan view showing a structure in which the differential circuit is arranged at the same height as the ground conductor, fig. 7(b) is a cross-sectional view showing a cross-sectional structure including the 1 st branch wiring, and fig. 7(c) is a cross-sectional view showing a cross-sectional structure including the 2 nd branch wiring.
Fig. 8 is a plan view showing another configuration of the differential signal transmission line according to embodiment 1.
In fig. 9, fig. 9(a) is a plan view showing a structure in which a signal conductor has a protruding portion, fig. 9(b) is a cross-sectional view showing a cross-sectional structure including the protruding portion, and fig. 9(c) is a cross-sectional view showing a cross-sectional structure including the 2 nd branch wiring.
Fig. 10 is a plan view showing the structure of the differential signal transmission line according to embodiment 1 on the differential output terminal side.
Fig. 11 is an equivalent circuit diagram showing a differential circuit connected to the differential signal transmission line according to embodiment 1.
Fig. 12(a) is a graph showing the result of calculating the characteristic impedance of the differential signal transmission line according to embodiment 1.
Fig. 12(b) is a graph showing the result of calculating the characteristic impedance of the differential signal transmission line according to embodiment 1.
Fig. 12(c) is a graph showing the result of calculating the characteristic impedance of the differential signal transmission line according to embodiment 1.
In fig. 13, fig. 13(a) is a graph showing the result of the reflection characteristic when R ═ R1 is calculated, and fig. 13(b) is a graph showing the result of the reflection characteristic when R ═ R2 is calculated.
In fig. 14, (a) in fig. 14 is a cross-sectional view showing a structure in which a pair of signal conductors are formed above a substrate, and (b) in fig. 14 is a cross-sectional view showing a structure in which a ground conductor is formed above a substrate.
Fig. 15(a) is a plan view showing the structure of the differential signal transmission line according to embodiment 2.
Fig. 15(b) is a plan view showing another configuration of the differential signal transmission line according to embodiment 2.
Fig. 16 is a plan view showing the structure of the differential signal transmission line according to embodiment 3.
Fig. 17 is a plan view showing the structure of the differential signal transmission line according to embodiment 4.
In fig. 18, fig. 18(a) is a plan view showing a structure of a conventional balanced line, and fig. 18(b) is a cross-sectional view showing a structure of a conventional balanced line.
In fig. 19, fig. 19(a) is a plan view showing the structure of a conventional ECCPW, and fig. 19(b) is a cross-sectional view showing the structure of the conventional ECCPW.
Fig. 20 is a plan view showing a structure in a case where a bent portion is formed in a conventional balanced line.
Fig. 21 is a plan view showing a configuration in a case where a differential circuit is connected to a conventional balanced line.
Detailed Description
Hereinafter, an embodiment of a high-frequency differential signal transmission line according to the present invention will be described with reference to the drawings. The high-frequency differential signal transmission line according to the present embodiment is used for transmitting and receiving a differential signal to and from a pair of differential terminals constituting a differential circuit such as a differential distributed amplifier or a distributed logic circuit. In addition, the dimensional ratio of each structure in each drawing does not necessarily correspond to the actual size.
(embodiment 1)
As shown in fig. 1 and 2, a differential signal transmission line 1 as a high-frequency differential signal transmission line according to embodiment 1 of the present invention is an ECCPW including: a 1 st signal conductor 11 and a 2 nd signal conductor 12 which are formed on the substrate 100 and serve as a pair of signal conductors for propagating a differential signal; a 1 st ground conductor 13 formed on the substrate 100 on a side of the 1 st signal conductor 11; and a 2 nd ground conductor 14 formed on the substrate 100 on a side of the 2 nd signal conductor 12.
The substrate 100 is a semiconductor substrate made of InP (indium-phosphorus), GaAs (gallium-arsenic), or Si (silicon), for example. The signal conductors 11 and 12 and the ground conductors 13 and 14 are formed of a conductor layer suitable for use as a metal for high-frequency signal transmission, and are formed of, for example, Cu (copper) or Au (gold). The ground conductors 13 and 14 may be at least a high-frequency ground (RF ground), and may be biased.
In the differential signal transmission line 1, a differential signal is input from one end 11a of the 1 st signal conductor 11 and one end 12a of the 2 nd signal conductor 12. On the other hand, the other end 11b of the 1 st signal conductor 11 and the other end 12b of the 2 nd signal conductor 12 are terminated by termination circuits each including termination resistors 15 and 16.
In fig. 1 and 2, W1 is the distance between the 1 st signal conductor 11 and the ground conductor 13 disposed laterally thereof. W2 is the distance between the 2 nd signal conductor 12 and the ground conductor 14 disposed laterally thereof. S1 is the width of the 1 st signal conductor 11. S2 is the width of the 2 nd signal conductor 12. d is the spacing between the 1 st signal conductor 11 and the 2 nd signal conductor 12. H is the thickness of the substrate 100. W1-W2-S2-S, W > 0, S > 0, and d > 0.
As will be described later, the differential signal transmission line 1 has a structure in which the interval d and the interval W satisfy the following expression (1) in at least a part thereof.
0.1＜(d/2-W)/(d/2+W)＜1……(1)
As shown in the cross-sectional view of fig. 2, the differential signal transmission line 1 has a configuration in which a 1 st signal conductor 11 and a 1 st ground conductor 13, and a 2 nd signal conductor 12 and a 2 nd ground conductor 14 are symmetrically arranged with respect to a center line. The characteristic impedance Z of the differential signal transmission line 1 thus configured0In the odd mode of transmitting the differential signal with the opposite phase, it is expressed as equation (2).
[ numerical formula 1]
Wherein ε r represents the relative dielectric constant, K (K), of the substrate 1003) K (delta) is K3δ, the first type of complete elliptic integral, k3And δ are constants determined by W, S, d, and H shown in fig. 2.
On the substrate 100, a differential circuit 21 having differential input terminals 21a and 21b for signal input as a pair of differential terminals is formed on the sides of the pair of signal conductors 11 and 12. In the example of fig. 1, the differential signal transmission line 1 includes a 1 st branch line 22a connecting the 1 st signal conductor 11 to the differential input terminal 21a and a 2 nd branch line 22b connecting the 2 nd signal conductor 12 to the differential input terminal 21b, and inputs a differential signal to a pair of differential input terminals 21a and 21b of the differential circuit 21. The white circles "" in fig. 1 indicate terminals, and lines extending from the ends of the signal conductors or the branch wirings indicate connections to the respective terminals. The same applies to the following figures.
The differential signal transmission line 1 further includes an intersection where the branch line 22b and the signal conductor 11 intersect with each other with the insulating layer interposed therebetween. Fig. 3 shows an example of a cross-sectional structure of the intersection 23 between the 1 st signal conductor 11 and the branch line 22b in the configuration of fig. 1. The intersection 23 is configured such that the intermediate portion 22b' of the branch line 22b passes through the insulating layer 100a in the lower portion of the 1 st signal conductor 11 provided on the substrate 100. In fig. 3, reference numeral 111 denotes a through hole. The insulating layer 100a is preferably low in dielectric constant and low in dielectric loss, and for example, polyimide or BCB (benzocyclobutene) is used. The intersection of fig. 3 shows a structure in which the branch line 22b passes below the signal conductor 11, but the signal conductor 11 may pass below the branch line 22 b.
Although only 1 differential circuit 21 is shown in fig. 1, differential circuit 21 may be disposed only on the side of one of the pair of signal conductors 11 and 12, as shown in fig. 4(a), for example. Alternatively, as shown in fig. 4(b), a plurality of differential circuits 21 may be disposed on both sides of the pair of signal conductors 11 and 12. In particular, if the longer branch lines 22b are alternately connected to the signal conductors 11 and 12 along the extending direction of the differential signal transmission line 1, the difference in capacitance due to the open stub characteristics of the branch lines added to the signal conductors 11 and 12 can be substantially eliminated. Note that, the plurality of differential circuits are all denoted by the same reference numeral 21, but the functions and characteristics of the respective differential circuits may be different.
Fig. 5 to 9 show another example of the arrangement of the differential circuit 21. Fig. 5(a) shows a structure in which differential circuit 21 and branch lines 22a and 22b are disposed below ground conductor 13. Fig. 5(b) shows a cross-sectional structure including the branch line 22a in the structure of fig. 5 (a). The branch wiring 22a is electrically connected to the signal conductor 11 via the through hole 111. Fig. 5(c) shows a cross-sectional structure including the branch line 22b in the structure of fig. 5 (a).
Fig. 6(a) shows another structure in which differential circuit 21 and branch lines 22a and 22b are disposed below ground conductor 13. Fig. 6(b) shows a cross-sectional structure including the branch line 22a in the structure of fig. 6 (a). The branch wiring 22a can be formed as a through hole. Fig. 6(c) shows a cross-sectional structure including the branch line 22b in the structure of fig. 6 (a).
Fig. 7(a) shows a structure in which differential circuit 21 is disposed at the same height as ground conductor 13. The ground conductor 13 has an opening 20, and a differential circuit 21 is disposed in the opening 20. Fig. 7(b) shows a cross-sectional structure including the branch line 22a in the structure of fig. 7 (a). The branch wiring 22a is electrically connected to the differential input terminal 21a and the signal conductor 11 via 2 through holes 111. Fig. 7(c) shows a cross-sectional structure including the branch line 22b in the structure of fig. 7 (a). The branch wiring 22b is electrically connected to the differential input terminal 21b via the through hole 111.
In the configuration of fig. 1, the ground conductor 13 is hollowed in the arrangement region of the differential circuit 21, and the cut-out portion 30 separates the interval between the signal conductor 11 and the ground conductor 13, so that the characteristic impedances of the signal conductor 11 and the signal conductor 12 become asymmetrical, which causes phase deviation between differential signals. Fig. 8 shows an example of another method for improving the asymmetry of the characteristic impedance generated by the cut-through portion in the structure of fig. 1. In the ground conductor 14, the same cutout portion 37 is provided at a position facing the cutout portion 30, and the interval between the signal conductor 11 and the ground conductor 13 and the interval between the signal conductor 12 and the ground conductor 14 in the cutout portion are made equal, so that asymmetry in characteristic impedance can be prevented. The through-cut portions in fig. 1 and 8 are rectangular, but may have other shapes such as a trapezoid or a polygon.
Fig. 9(a) shows a configuration in which the signal conductor 11 has a protruding portion 27, and the short branch wiring 22a is omitted by directly connecting the protruding portion 27 to the differential input terminal 21 a. Fig. 9(b) shows a cross-sectional structure including the projection 27 in the structure of fig. 9 (a). Fig. 9(c) shows a cross-sectional structure including the branch line 22b and the intermediate portion 22b' thereof in the structure of fig. 9 (a).
The differential signal transmission line according to the present embodiment is not limited to the configuration shown in fig. 1 connected to the differential input terminals 21a and 21b of the differential circuit 21, and may be configured to be connected to the differential output terminals 41a and 41b for signal output of the differential circuit 41, as shown in fig. 10, for example. In fig. 10, the differential signal transmission line 1' is an ECCPW including: a 1 st signal conductor 31 and a 2 nd signal conductor 32 formed on the substrate 100 as a pair of signal conductors for propagating a differential signal; a 1 st ground conductor 33 formed on the substrate 100 on a side of the 1 st signal conductor 31; and a 2 nd ground conductor 34 formed on the substrate 100 on a side of the 2 nd signal conductor 32.
In the differential signal transmission line 1', a differential signal is output from one end 31a of the 1 st signal conductor 31 and one end 32a of the 2 nd signal conductor 32. On the other hand, the other end 31b of the 1 st signal conductor 31 and the other end 32b of the 2 nd signal conductor 32 are terminated by termination circuits each including termination resistors 35 and 36.
In fig. 10, W1 is the distance between the 1 st signal conductor 31 and the ground conductor 33 disposed laterally thereof. W2 is the distance between the 2 nd signal conductor 32 and the ground conductor 34 disposed laterally thereof. S1 is the width of the 1 st signal conductor 31. S2 is the width of the 2 nd signal conductor 32. d is the spacing between the 1 st signal conductor 31 and the 2 nd signal conductor 32.
In the differential signal transmission line 1', W1 ═ W2 ═ W, S1 ═ S2 ═ S also satisfies the relationship of expression (1). The differential signal transmission line 1' has the same cross-sectional structure as the differential signal transmission line 1 shown in fig. 2 and 3.
The differential circuit 41 having the differential output terminals 41a and 41b as a pair of differential terminals is formed on the substrate 100 on the sides of the pair of signal conductors 31 and 32. In the example of fig. 10, the differential signal transmission line 1' includes a 1 st branch line 42a connecting the 2 nd signal conductor 32 to the differential output terminal 41a and a 2 nd branch line 42b connecting the 1 st signal conductor 31 to the differential output terminal 41b, and outputs a differential signal from the pair of differential output terminals 41a and 41b of the differential circuit 41. The differential signal transmission line 1' has an intersection where the 2 nd branch line 42b and the 2 nd signal conductor 32 intersect with each other with an insulating layer interposed therebetween, in the same manner as the configuration of the differential signal transmission line 1 shown in fig. 3.
In the differential signal transmission line 1', a plurality of differential circuits 41 may be arranged as shown in fig. 4, and other arrangement examples may be adopted as shown in fig. 5 to 9. At this time, the differential input terminals 21a and 21b of the differential circuit 21 in fig. 4 to 9 are replaced with the differential output terminals 41a and 41b of the differential circuit 41.
The differential signal transmission line according to the present embodiment may have the following configuration: as a pair of differential terminals of the differential circuit to be connected, the differential input terminals 21a and 21b of the differential circuit 21 and the differential output terminals 41a and 41b of the differential circuit 41 are mixed. The above-described structure is obtained by connecting one ends 31a, 32a of the pair of signal conductors of the differential signal transmission line 1' of fig. 10 and one ends 11a, 12a of the pair of signal conductors of the differential signal transmission line 1 of fig. 1, for example. In the above example, the following structure is adopted: the differential signal output from the pair of differential output terminals 41a and 41b of the differential circuit 41 propagates through the signal conductor and is input to the pair of differential input terminals 21a and 21b of the differential circuit 21.
In the above example, a plurality of differential circuits 41 and 21 may be arranged as shown in fig. 4, or another arrangement example may be adopted as shown in fig. 5 to 9.
Fig. 11 shows an example of a differential circuit that amplifies a differential signal. The differential circuit 50 has the following structure: load resistors 53 and 54 having the same resistance value are connected between the collectors (or drains) of the differential pair transistors 51 and 52 and the high-potential-side power supply VH, the emitters (or sources) are connected to each other, and the connection point is connected to the low-potential-side power supply via a common current source 55.
In the differential circuit 50, the bases (or gates) of the transistors 51 and 52 are a pair of differential input terminals, and the connection points 56a and 57a between the collectors (or drains) and the load resistors 53 and 54 are a pair of differential output terminals. The differential circuit 50 reversely amplifies differential signals Vin (+), Vin (-) input to the base (or gate), and outputs differential signals Vout (+), Vout (-) from the connection points 56a, 57 a. In the case where differential circuit 41 of fig. 10 is configured as differential circuit 50, termination resistors 35 and 36 may be configured to double as load resistors 53 and 54 of differential circuit 50.
The configuration of the differential circuit for amplifying the differential signal is not limited to the configuration of fig. 11, and may be a cascade type, a negative feedback type circuit configuration, or a configuration in which another circuit is connected to the differential circuit 50 in multiple stages. Further, a circuit may be formed using a bipolar transistor or a field effect transistor.
Fig. 12(a) shows the calculation of the characteristic impedance Z of the differential signal transmission line 1 when an InP substrate is used as the substrate 100 in the configuration of fig. 20Graph of the results of (a). In the region where the differential circuit 21 is not formed on the side, the distance (d/2+ W + S) from the center line of the 1 st signal conductor 11 and the 2 nd signal conductor 12 to the ground conductors 13 and 14 is set to 50 μm, and the thickness H of the substrate 100 is set to 500 μm, so that the ratio of the distance d/2 to the distance W is changed. The above value is a size in a range generally used for a wiring layout of a real IC.
The vertical axis of the graph of FIG. 12(a) is the characteristic impedance Z0The abscissa is a value normalized by dividing the difference between d/2 and W (d/2-W) by the sum of d/2 and W (d/2+ W), i.e., (d/2-W)/(d/2+ W). When R is in the range of-1 < R < 1 and the ratio of d/2 to W is 1:1, R is 0, the smaller d/2, the closer R is to-1, and the smaller W, the closer R is to 1. According to the graph of FIG. 12(a), R and Z are independent of the value of the width S0The relationship (c) is the shape of the upward-projecting function, and Z is 0.1 when R is equal to0Becomes the largest. In addition, this relationship is almost established regardless of the values of W, S, d, and H.
FIG. 12(b) is a graph in which the characteristic impedance Z is calculated in the same manner as in FIG. 12(a) with the above (d/2+ W + S) set to 15 μm and H set to 100 μm0The result of (1). FIG. 12(c) shows the characteristic impedance Z calculated in the same manner as in FIG. 12(a) with the above (d/2+ W + S) set to 10 μm and H set to 50 μm0The result of (1). The above value is also a size in a range generally used in an actual wiring layout of an IC.
In fig. 12(b) and 12(c), R and Z are the same as in fig. 12(a), regardless of the value of the width S0The relationship (c) is the shape of the upward-projecting function, and Z is 0.1 when R is equal to0Becomes the largest.
The characteristics of fig. 12(a) will be described with reference to the cross-sectional view of fig. 2. Since the cross-sectional view of fig. 2 is symmetrical about the center line, the graph of fig. 12(a) shows the arrangement of the 2 nd signal conductor 12 in the middle of the arrangement, only by the right side of the center line of fig. 2A characteristic impedance Z at a position substantially midway between the core line and the ground conductor 14(R is 0.1)0Becomes the largest. The 2 nd signal conductor 12 is bounded by R0.1 and the electromagnetic coupling with respect to the 1 st signal conductor 11 increases as the distance from the center line (R-1 side), the capacitance component of the line increases and the characteristic impedance Z increases0And (4) descending. On the other hand, the 2 nd signal conductor 12 is bounded by R0.1, and the electromagnetic coupling with respect to the ground conductor 14 becomes larger than the electromagnetic coupling with respect to the 1 st signal conductor 11 as the distance from the ground conductor 14 (R1 side), so that the capacitance component of the line increases and the characteristic impedance decreases.
The balanced line is originally characterized by strong electromagnetic coupling between a pair of signal conductors, and in the configuration under the condition of 0.1 < R < 1, the electromagnetic coupling between each of the signal conductors 11 and 12 and the lateral ground conductors 13 and 14 becomes larger, and it is considered that this is a line having strong characteristics of the unbalanced line.
For example, in the graph of fig. 12(a), when S is 3 μm, R is-0.53 when R1 is R2 is 0.70, the characteristic impedance Z is0All become about 80 omega. Since the relationship between the magnitudes of R1 and R2 is-1 < R1 < 0.1 < R2 < 1, it can be said that when R is R1, the electromagnetic coupling between each signal conductor 11, 12 and the other signal conductor is strong, and when R is R2, the electromagnetic coupling between each signal conductor 11, 12 and the lateral ground conductors 13, 14 is strong.
Fig. 13 shows the result of calculating the reflection characteristics of the differential signal transmission line 1 having the configuration of fig. 2, where R is R1 and R is R2, when there is a phase difference between the input differential signals, by an electromagnetic field simulator. In the calculation, the length of the line was set to 400 μm, and the terminal portions (the other ends) 11b and 12b were terminated by 80 Ω terminating resistors.
Fig. 13(a) shows the characteristics of the reflection loss Sdd11 in the differential mode of the differential signal transmission line having the configuration of R ═ R1(-1 < R1 < 0.1), and shows the cases where the phase shift amounts Δ θ of the input differential signals at 10GHz are 0 °, 15 °, and 30 °, respectively. According to the figure, the reflection loss Sdd11 in the state where Δ θ is 0 ° without phase deviation is-20 dB or less in the frequency range DC to 65GHz, but the reflection loss Sdd11 increases with an increase in phase deviation, and when Δ θ is 30 °, the reflection loss Sdd11 deteriorates to-10 dB or more in 50GHz or more. This is because, in the configuration of R — R1, since electromagnetic coupling between the pair of signal conductors is large, the characteristic impedance becomes large with respect to the common mode component generated by the phase deviation, and the characteristic impedance becomes mismatched.
On the other hand, as shown in fig. 13(b), in the configuration of R ═ R2 (0.1 < R2 < 1), since electromagnetic coupling between the signal conductors 11 and 12 and the ground conductors 13 and 14 is large and the characteristics of the unbalanced line are strong, deterioration of reflection characteristics due to phase deviation does not occur, and even in a state where there is a phase deviation of Δ θ ═ 0 °, 15 °, and 30 ° in the differential signal, the reflection loss Sdd11 is suppressed to-20 dB or less in the frequency range DC to 65 GHz.
From the results of fig. 13, it was confirmed that even if a phase shift occurs between differential signals due to a difference in conductor length of branch wiring, a difference in length of an external coaxial cable, or the like, by adopting the line structure of 0.1 < R < 1 in the present embodiment, it is possible to suppress an increase in reflection loss of the differential signal transmission line and prevent the occurrence of reflection interference or electromagnetic radiation interference.
The arrangement relationship between the signal conductors and the ground conductors constituting the differential signal transmission lines 1 and 1' may be, for example, as shown in fig. 14(a), such that the pair of signal conductors 11 and 12 are formed above the upper surfaces of the ground conductors 13 and 14 formed on the substrate 100 by a height Δ H with an insulating layer 100a interposed therebetween. Δ H is sufficiently smaller than the thickness H of the substrate 100. Alternatively, as shown in fig. 14(b), the ground conductors 13 and 14 may be formed above the upper surfaces of the pair of signal conductors 11 and 12 formed on the substrate 100 by Δ H with the insulating layer 100a interposed therebetween.
As shown in fig. 4, for example, the differential distributed amplifier or the distributed logic circuit is configured such that the differential input/output terminals (the differential input terminals 21a and 21b in fig. 4) of a plurality of differential circuits 21 (or 41) formed on the substrate 100 at predetermined intervals are connected in parallel to the differential signal transmission lines 1 and 1', and the inductance components of the differential signal transmission lines 1 and 1' and the input/output capacitances (the input capacitances in fig. 4) of the differential circuits are designed to be equivalent to each other to form a high-cutoff analog distributed constant line. When the characteristic impedance of the analog distributed constant line is 50 Ω which is generally used in microwave transmission, the characteristic impedance of the differential signal transmission lines 1 and 1 'needs to be higher than 50 Ω (for example, 70 Ω) in order to generate impedance in the differential signal transmission lines 1 and 1' and cancel out the input/output capacitance. In order to reduce power consumption, it is necessary to increase the load resistance of a circuit that transmits a differential signal to a differential circuit, and to set a higher characteristic impedance (e.g., 90 Ω) when transmitting at 70 Ω, for example. From the graph of fig. 12(a), in the differential signal transmission lines 1 and 1' according to the present embodiment, by adjusting S or R in the range of 0.1 < R < 1, high characteristic impedance of 50 Ω or more can be realized, and a differential distributed amplifier or a distributed logic circuit can be designed with a high degree of freedom. In fig. 4, a case where the differential input/output terminal is a differential input terminal and the input/output capacitance of the differential circuit is an input capacitance is illustrated, but the same effect can be obtained by a configuration where the differential input/output terminal is a differential output terminal and the input/output capacitance of the differential circuit is an output capacitance.
As described above, the differential signal transmission lines 1 and 1' according to the present embodiment are configured such that the pair of signal conductors 11, 12, 31, and 32 constituting the balanced line are arranged close to the ground conductors 13, 14, 33, and 34 formed on the respective sides, and therefore, although they are balanced lines, they have a strong unbalanced line property and are less susceptible to phase deviation of the differential signals.
Thus, the differential signal transmission lines 1 and 1' according to the present embodiment can prevent the deterioration of reflection characteristics and the occurrence of unnecessary electromagnetic interference due to phase deviation between differential signals caused by complicated arrangement of the signal conductors 11, 12, 31, and 32 formed on the substrate 100, and can realize a small-area differential signal transmission line with good manufacturability.
In the differential signal transmission lines 1 and 1' according to the present embodiment, a plurality of differential circuits 21 and 41 can be arranged on the sides of the pair of signal conductors 11, 12, 31 and 32 via a plurality of branch lines 22a, 22b, 42a and 42 b.
Further, the differential signal transmission lines 1 and 1' according to the present embodiment can easily realize a high characteristic impedance of 50 Ω or more, and thus can constitute a differential distributed amplifier or a distributed logic circuit with a high degree of freedom in design.
Further, it is also possible to form a signal transmission system that transmits and processes differential signals by: an IC including the differential signal transmission lines 1 and 1' and the substrate 100; a signal generating device disposed outside the IC; and a transmission medium for transmitting the differential signal generated by the signal generating device from the outside to the IC. The differential signal inputted to the IC from the outside via the transmission medium is inputted to, for example, one ends 11a and 12a of the pair of signal conductors 11 and 12. With this configuration, even if a phase shift occurs between the differential signals due to the difference in length of the transmission medium, it is possible to suppress deterioration of the reflection characteristics of the differential signals transmitted inside the IC, and realize a signal transmission system that operates with high quality and high stability. The transmission medium refers to a coaxial cable, a connector, a bonding wire, and the like externally connected to the IC including the differential signal transmission lines 1 and 1'.
(embodiment 2)
Next, a differential signal transmission line 2 as a high-frequency differential signal transmission line according to embodiment 2 of the present invention will be described with reference to the drawings. The same configurations as those of the differential signal transmission lines 1 and 1' according to embodiment 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
As shown in fig. 15(a), in the differential signal transmission line 2 according to the present embodiment, the pair of signal conductors 11 and 12 have 90 ° bends 24. If there are 1 such bent portion 24, a physical length difference of 2 × d occurs in the pair of signal conductors 11 and 12, and a phase shift occurs in the differential signal after passing through the bent portion 24, which becomes a factor of deterioration of reflection characteristics.
Even with this configuration, by adjusting the values of the interval d and the interval W so as to satisfy the formula (1) for the pair of signal conductors 11 and 12 and the ground conductors 13 and 14 before and after the bent portion 24, it is possible to realize a differential signal transmission line without deterioration of reflection characteristics even though the bent portion is provided. In addition, although fig. 15(a) shows only the configuration of the transmission lines connected to the differential input terminals 21a and 21b of the differential circuit 21, the same bending portions can be provided for the transmission lines connected to the differential output terminals 42a and 42b of the differential circuit 41 as shown in fig. 10 of embodiment 1.
In the differential signal transmission line 2 of fig. 15(a), since a phase shift occurs between the differential signals after the differential signals pass through the bent portion 24, an effect of suppressing deterioration of the reflection characteristics can be obtained even when only the interval d and the interval W of the differential signal transmission line between the bent portion 24 and the terminating resistors 15 and 16 satisfy the formula (1).
In the above embodiment, the embodiment in which the angle of the bent portion 24 is 90 ° is illustrated, but the angle of the bent portion of the differential signal transmission line according to the present invention may be other than 90 °, and a portion in which the angle changes may be formed smoothly in a curved line. Further, a plurality of bending portions 24 or differential circuits 21 (or differential circuits 41) may be provided, or differential circuits 21 may be disposed at a later stage of terminating resistors 15 and 16 as shown in fig. 15 (b). In the configuration of fig. 15(b), the termination resistor 15 connects the signal conductor 11 and the ground conductor 13, and the termination resistor 16 connects the signal conductor 12 and the ground conductor 14. As shown, the ground conductor 13 and the ground conductor 14 are electrically connected. The configuration in which the differential circuit is disposed in the subsequent stage of the termination resistor as shown in fig. 15(b) can be similarly applied to fig. 1, 4(a), 4(b), 5(a), 5(b), 6(a), 7(a), 8, 9(a), and fig. 16 or 17 described later. As a modification, a configuration in which a differential circuit is arranged in the front stage of the termination resistors 35 and 36 in fig. 10 can also be applied.
As described above, in the differential signal transmission line 2 according to the present embodiment, since the pair of signal conductors 11 and 12 have the bent portion 24, the signal conductor length can be secured long within the limited size of the substrate 100, and therefore, a larger number of differential circuits 21 can be arranged on the side of the pair of signal conductors 11 and 12.
(embodiment 3)
Next, a differential signal transmission line 3 as a high-frequency differential signal transmission line according to embodiment 3 of the present invention will be described with reference to the drawings. The same configurations as those of the differential signal transmission lines 1, 1', and 2 according to embodiments 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.
As shown in fig. 16, in the differential signal transmission line 3 according to the present embodiment, the pair of signal conductors 11 and 12 have 90 ° bends 25. In the bent portion 25, the distance d1 between the pair of signal conductors 11 and 12 is narrower than the distance d between the pair of signal conductors 11 and 12 before and after the bent portion 25 (d1 < d).
With this configuration, the conductor length difference between the 1 st signal conductor 11 and the 2 nd signal conductor 12 due to the bent portion 25 can be shortened from 2 × d, which is shown in fig. 15 of the normal embodiment 2, to 2 × d1, and the amount of phase deviation between differential signals generated at the bent portion can be reduced.
In the pair of signal conductors 11 and 12 and ground conductors 13 and 14 before and after the bent portion 25, the interval d and the interval W have values satisfying the formula (1).
However, if the distance between the pair of signal conductors 11 and 12 in the bent portion 25 is d1 narrower than d, the characteristic impedance of the line is different between the portion of the distance d and the portion of the distance d1, but as shown in the graph in fig. 12(a), 12(b), or 12(c), even if the distance between the signal conductors is different, the characteristic impedance can be made to be the same as that of the distances W1, W2 (or the widths S1, S2) by adjusting the distance d 1.
In addition, although fig. 16 shows only the configuration of the transmission lines connected to the differential input terminals 21a and 21b of the differential circuit 21, the same bending portions can be provided for the transmission lines connected to the differential output terminals 42a and 42b of the differential circuit 41 as shown in fig. 10 of embodiment 1.
In the above embodiment, the angle of the bent portion 25 is 90 °, but the angle of the bent portion of the differential signal transmission line according to the present invention may be other than 90 °, or a portion where the angle changes may be formed smoothly in a curved line. Further, a plurality of bending portions 25 or differential circuits 21 (or differential circuits 41) may be provided.
As described above, in the differential signal transmission line 3 according to the present embodiment, the amount of phase shift between the differential signals generated in the bending portion 25 can be reduced, and the strain or the deterioration of the frequency band of the differential circuit 21 or 41 operated by inputting the differential signals, or the deterioration of the transmission characteristics of the other transmission line to which the differential signals are inputted can be suppressed.
(embodiment 4)
Next, a differential signal transmission line 4 as a high-frequency differential signal transmission line according to embodiment 4 of the present invention will be described with reference to the drawings. The same configurations as those of the differential signal transmission lines 1 and 1' according to embodiment 1 are denoted by the same reference numerals, and detailed description thereof is omitted.
In the differential signal transmission line 1 according to embodiment 1 shown in fig. 1, the branch wiring 22b is formed to be longer than the branch wiring 22a by the distance d. As shown in fig. 17, in the differential signal transmission line 4 of the present embodiment, the distance d2 between the pair of signal conductors 11 and 12 in the connection portion 26 to which the branch wirings 22a and 22b are connected is narrower than the distance d between the pair of signal conductors 11 and 12 before and after the connection portion 26.
Thus, normally, as shown in fig. 1 of embodiment 1, the conductor length difference d between the branch wirings 22a and 22b can be shortened to d2, so that the difference in the capacitance due to the open stub characteristic of the branch wirings added to the 1 st signal conductor 11 and the 2 nd signal conductor 12 can be reduced, and the phase shift generated between the differential signals can be suppressed.
In the pair of signal conductors 11 and 12 and ground conductors 13 and 14 before and after the connection portion 26, the interval d and the interval W have values satisfying the formula (1).
If the distance between the pair of signal conductors 11 and 12 in the connection portion 26 is d2 narrower than d, the characteristic impedance of the line will be different between the portion at the distance d and the portion at the distance d 2. However, as shown in the graphs of fig. 12(a), 12(b), or 12(c), even if the distances between the signal conductors are different, the characteristic impedance can be made to be the same by adjusting the interval d2 and the intervals W1, W2 (or the widths S1, S2). In addition, when it is difficult to adjust the distance d2 and the distances W1 and W2 by providing the cut-out portions of the ground conductors in the arrangement region of the differential circuit 21, the arrangement example shown in fig. 5 to 8 may be adopted.
In addition, although fig. 17 shows only the configuration of the transmission lines connected to the differential input terminals 21a and 21b of the differential circuit 21, the same connection portions can be provided for the transmission lines connected to the differential output terminals 42a and 42b of the differential circuit 41 as shown in fig. 10 of embodiment 1.
The bent portions of the connecting portion 26 where the signal conductors 11 and 12 narrow to the front and rear of the interval d2 may be formed in a curved line smoothly, or may have a shape that is not symmetrical with respect to the center line between the signal conductors as shown in the figure. Further, a plurality of connection portions 26 or differential circuits 21 (or differential circuits 41) may be provided.
As described above, in the differential signal transmission line 4 according to the present embodiment, the amount of phase deviation between the differential signals caused by the connection of the branch lines 22a and 22b (or 42a and 42b) can be reduced, and the strain or the frequency band of the differential circuit 21 or 41 operated by inputting the differential signals can be suppressed from deteriorating, or the transmission characteristics of another transmission line to which the differential signals are inputted can be suppressed from deteriorating.
Description of the symbols
1-4, 1' -differential signal transmission lines, 11, 12, 31, 32-signal conductors, 11a, 12a, 31a, 32 a-one ends, 11b, 12b, 31b, 32 b-the other ends, 13, 14, 33, 34-ground conductors, 15, 16, 35, 36-terminating resistors (terminating circuits), 21, 41-differential circuits, 21a, 21 b-differential input terminals, 22a, 22b, 42a, 42 b-branch wirings, 23-intersections, 24, 25-bends, 26-connections, 41a, 41 b-differential output terminals, 50-differential circuits, 51, 52-transistors, 53, 54-load resistors, 55-constant current sources, 100-substrates, 100 a-insulating layers.
Claims (10)
1. A high-frequency differential signal transmission line (1-4, 1') includes:
a substrate (100);
a pair of signal conductors (11, 12, 31, 32) formed on the substrate (100) and used for transmitting differential signals; and
a 1 st ground conductor (13, 33) and a 2 nd ground conductor (14, 34) formed on both sides of the pair of signal conductors on the substrate,
one end (11a, 12a, 31a, 32a) of the pair of signal conductors is inputted with and outputted from a differential signal, the other end (11b, 12b, 31b, 32b) of the pair of signal conductors is terminated by a termination circuit (15, 16, 35, 36) and transmits and receives the differential signal to and from a pair of differential terminals (21a, 21b, 41a, 41b) of a differential circuit (21, 41) formed on the substrate,
the pair of signal conductors is composed of a 1 st signal conductor (11, 31) and a 2 nd signal conductor (12, 32),
the width of the 1 st signal conductor is equal to the width of the 2 nd signal conductor,
the interval between the 1 st signal conductor and the 1 st ground conductor disposed on the side thereof is equal to the interval between the 2 nd signal conductor and the 2 nd ground conductor disposed on the side thereof, and the high-frequency differential signal transmission line (1 to 4, 1') has the following structure:
when the distance is W and the distance between the 1 st signal conductor and the 2 nd signal conductor is d, 0.1 < (d/2-W)/(d/2+ W) < 1 is obtained.
2. A high-frequency differential signal transmission line according to claim 1,
the differential circuit has a pair of differential terminals (21a, 21b, 41a, 41b),
the differential circuit is formed on the side of the 1 st signal conductor,
the high-frequency differential signal transmission line further includes: branch wirings (22b, 42b) connecting the 2 nd signal conductor to one of the pair of differential terminals; and an intersection (23) where the branch line and the 1 st signal conductor intersect with an insulating layer (100a) interposed therebetween.
3. A high-frequency differential signal transmission line according to claim 1,
the differential circuit is formed on a side of the 2 nd signal conductor,
the high-frequency differential signal transmission line further includes: a branch wiring (42b) connecting the 1 st signal conductor to one of the pair of differential terminals; and an intersection (23) where the branch line and the 2 nd signal conductor intersect with an insulating layer (100a) interposed therebetween.
4. A high-frequency differential signal transmission line according to any one of claims 1 to 3,
the pair of signal conductors have bent portions (24, 25).
5. A high-frequency differential signal transmission line according to claim 4,
the interval between the pair of signal conductors in the bent portion is narrower than the interval between the pair of signal conductors before and after the bent portion.
6. A high-frequency differential signal transmission line according to claim 2 or 3,
the distance between the pair of signal conductors in a connection portion (26) to which the branch wiring is connected is narrower than the distance between the pair of signal conductors before and after the connection portion.
7. A high-frequency differential signal transmission line according to any one of claims 1 to 3,
the substrate is a semiconductor substrate made of InP, GaAs or Si.
8. A high-frequency differential signal transmission line according to any one of claims 1 to 3,
the differential circuit is formed in plurality on the substrate,
and a pair of differential terminals of the plurality of differential circuits, wherein the differential signals are transmitted and received.
9. A high-frequency differential signal transmission line according to claim 8,
the pair of differential terminals of at least 1 of the differential circuits is a pair of differential input terminals (21a, 21b) for signal input, and the pair of differential terminals of at least another one of the differential circuits is a pair of differential output terminals (41a, 41b) for signal output.
10. A signal transmission system, characterized in that,
the high-frequency differential signal transmission line according to any one of claims 1 to 9, the substrate, a signal generating device for generating the differential signal, and a transmission medium for transmitting the differential signal are provided,
the signal generating device and the transmission medium are arranged outside the substrate,
the differential signal is input into the one end of the pair of signal conductors.
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| JP2017-041893 | 2017-03-06 | ||
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| JP2018024705A JP6687045B2 (en) | 2017-03-06 | 2018-02-15 | High frequency differential signal transmission line and signal transmission system including the same |
| JP2018-024705 | 2018-02-15 |
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| CN201657492U (en) * | 2010-04-20 | 2010-11-24 | 英业达股份有限公司 | Printed circuit board |
| CN103098560A (en) * | 2010-08-30 | 2013-05-08 | 株式会社藤仓 | Differential signal transmission circuit and method for manufacturing same |
| CN204929375U (en) * | 2015-06-26 | 2015-12-30 | 深圳市兴森快捷电路科技股份有限公司 | Be applied to line structure of walking of packet ground differential signal impedance optimization |
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|---|---|---|---|---|
| CN201657492U (en) * | 2010-04-20 | 2010-11-24 | 英业达股份有限公司 | Printed circuit board |
| CN103098560A (en) * | 2010-08-30 | 2013-05-08 | 株式会社藤仓 | Differential signal transmission circuit and method for manufacturing same |
| CN204929375U (en) * | 2015-06-26 | 2015-12-30 | 深圳市兴森快捷电路科技股份有限公司 | Be applied to line structure of walking of packet ground differential signal impedance optimization |
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