CA2228906A1 - Impedance converting device - Google Patents
Impedance converting device Download PDFInfo
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- CA2228906A1 CA2228906A1 CA 2228906 CA2228906A CA2228906A1 CA 2228906 A1 CA2228906 A1 CA 2228906A1 CA 2228906 CA2228906 CA 2228906 CA 2228906 A CA2228906 A CA 2228906A CA 2228906 A1 CA2228906 A1 CA 2228906A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P5/00—Coupling devices of the waveguide type
- H01P5/02—Coupling devices of the waveguide type with invariable factor of coupling
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Abstract
A impedance converting device has an impedance-adjustable conductor electromagnetically connected between a signal conductor and a reference conductor. The impedance-adjustable conductor includes a plurality of connection regions each providing a different impedance. An impedance difference between adjacent ones of the connection regions is determined depending on a pattern of the impedance-adjustable conductor. The impedance difference may be substantially uniform between any adjacent ones of the connection regions.
Description
CA 02228906 1998-0~-12 IMPEDANCE COhv~hllNG DEVICE
BACKGROUND OF THE INVENTION
1. Field of the invention The present invention generally relates to high frequency circuits such as microwave circuits and in particular to an impedance converting device for use in distributed constant lines such as microstrip or coaxial lines.
BACKGROUND OF THE INVENTION
1. Field of the invention The present invention generally relates to high frequency circuits such as microwave circuits and in particular to an impedance converting device for use in distributed constant lines such as microstrip or coaxial lines.
2. Description of the Related Art In high frequency circuits operating at high frequency bands including a microwave band, an impedance mismatch problem produces energy loss and undesired frequency characteristics, making it difficult to efficiently couple energy into and out of a component. Especially, in the case of an amplifier, since the characteristic impedance of the amplifier is different from that of anotherpassive device,ithasbecomecommontouse animpedance matching circuit at each of input and output sides of the amplifier.
A conventionalimpedance adjustingcircuit is shown in Fig.
1, which is comprised of a microstrip line 1 and an impedance adjuster 2 which is further comprised of a plurality of conductor pieces 3a-3c each having the same physical length. The conductor pieces 3a-3c are placed in a line and they can be connected by CA 02228906 1998-0~-12 wire bonds 4 such that the physical (or electrical) length can be set to a desired value. In Fig. 1, for example, the first and second conductor pieces 3a and 3b are connected by wire bonds 4 to produce a physical length of 2Lo. Such a circuit has been described in Japanese Utility-model Unex~m;ned Publication No.
59-39501 and Japanese Patent Unex~mined Publication No. 61-133702.
These publications have further disclosed an improved impedance converting circuit capable of adjusting the impedance of a microstrip line. In the former Publication (No. 59-39501), the impedance converting circuit is provided with a microstrip line connected to an adjusting strip line which has an upwardly bent portion at an end thereof. The characteristic impedance is varied depending on capacitance determined by the amount of the bend. In the latter Publication (No. 61-133702), the characteristic impedance is adjusted by cutting a part of an open stub connected to the microstrip line.
Further,anothermicrowavecircuitcapableofadjustingthe impedance of a microstrip line has been disclosed in Japanese PatentUnex~minedPublicationNo.2-94902. Themicrowavecircuit is provided with an open stub and an adjusting strip line for adjusting the length of the open stub. The characteristic impedance is varied depending on the position at which the open stub is electrically connected to the adjusting strip line.
As described above, conventional impedance converting or adjusting circuits achieve the impedance matching by varying the CA 02228906 1998-0~-12 length of an open stub to produce a desired reactance.
However, the conventionalcircuitsprovide no quantitative analysisofthelengthoftheopenstub. Further,fromapractical point of view, there may be cases where it is difficult or impossible to set the impedance adjusting circuit to the optimal impedance.
SUMMARY OF THE INVENTION
The inventor found that an easy and fine adjustment of characteristic impedance can be achievedby changingthe physical length depending on the sensitivity of impedance of a stub. More specifically, asshowninFig.2,theamountofchangeinimpedance is not linear with respect to the length of a stub. Especially, it is dramatically changed in the vicinity of L = A /4, where ~ is an effective wave length of a signal passing through a microstrip. Therefore, in the case where the characteristic impedance is adjusted depending on the length of a stub, there are variations in sensitivity.
According to the present invention, a length changing step varies according to the sensitivity. More specifically, the higher the sensitivity, the shorter the length changing step. In this manner, the linear impedance characteristic with respect to the number of length changing steps is achieved, resulting in an easy and fine adjustment of characteristic impedance.
CA 02228906 1998-0~-12 In general, the impedance Z is expressed by the following equation: Z = g(L) ~ ~L + ~, Where L is a physical length of the impedance converter and~ and ~ are constant. Therefore, if the physical length L of a distributed constant impedance converter is not linear as expressed by L = f(x) ~ ax + b, where x is the number of length changing steps and a and b are constant, then it is possible to produce a linear relationship between the impedance Z and the number x of length changing steps. More specifically, the function f() such that Z = g(L) = g(f(x)) = px + q can be obtained.
According to the present invention, an impedance-adjustable conductor is electromagnetically connected between a signal conductor and a grounded or reference conductor and is comprised of a plurality of connection regions each providing a different impedance, wherein an impedance difference between adjacent ones of the connection regions is determined depending on a pattern of the impedance-adjustable conductor. The impedance difference may be substantially uniform between any adjacent ones of the connection regions.
According to another aspect of the present invention, the impedance-adjustable conductor is comprised of a plurality of connection regions each providing a different conductor length, wherein the impedance-adjustable conductor linearly changes in impedancedependingonnumberofconnectionregionseachconnected by a conductor. The impedance-adjustable conductor may have a linear characteristic of sensitivity of impedance with respect CA 02228906 1998-0~-12 to the amount of change in length determined by the number of connection regions each connected by a conductor.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view showing a conventional impedance converting device;
Fig. 2 is a graph showing changes in impedance with respect to a physical length of a stub;
Fig. 3 is a block diagram showing an impedance adjusting system employing an impedance converting device according to the present invention;
Fig. 4A is a diagram showing a capacitance changing characteristic of an open stub and the respective lengths of conductor pieces in an impedance converting device according to the present invention;
Fig. 4B is a graph showing the linear relation ship between the impedance and the number of adjustment steps in the impedance converting device of Fig. 4A;
Fig. 5 is aplanview showing an impedance convertingdevice CA 02228906 1998-0~-12 according to a first embodiment of the present invention;
Fig. 6 is aplanview showingan impedance converting device according to a second embodiment of the present invention;
Fig. 7 is aplanview showingan impedanceconverting device according to a third embodiment of the present invention;
Fig. 8 is aplan view showingan impedance converting device according to a fourth embodiment of the present invention;
Fig. 9 is aplanview showingan impedance converting device according to a fifth embodiment of the present invention;
Fig.10isaplanviewshowinganimpedanceconvertingdevice according to a sixth embodiment of the present invention; and Fig. 11 is a plan view showing a concrete example of the first embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 3, a microstrip/coaxial line 10 is comprised of a line conductor 10a which a signal passes through and a grounded (or reference) conductor 10b which is opposed to CA 02228906 1998-0~-12 the line conductor lOa through a dielectric. Further, a distributed constant impedance converter 11 according to the present invention electromagnetically connects the line conductor lOa and the grounded conductor lOb to achieve impedance conversion.
The impedance converter 11 has a plurality of connection regions which are selectively connected by conductors such as wirebonds, leads or other electrical connections. Such a connection step is controlled by an adjustment controller 12.
More specifically, when the adjustment controller 12 produces an adjustment step x which determines the number of connection regions, the corresponding connection regions are connected by connection conductors such as wirebonds or leads to produce a desired electrical length of the impedance converter. As described before, the impedance is not linear with respect to the electrical length but the adjustment step x.
Taking an open stub of a microstrip line as an example hereinafter, the impedance converter 11 is comprised of a plurality of conductor pieces discretely placedon the dielectric such that they are arranged in line in the vicinity of the line conductor lOa. The respective conductor pieces are shaped with varying in physical length according to a distance from the line conductor lOa.
When the adjustment controller 12 produces the adjustment step x=2, the first conductor piece is electrically connected to the line conductor lOa, and then the second conductor piece CA 02228906 1998-0~-12 adjacent to the first conductor piece is electrically connected to the first conductor piece. Therefore, the adjustment step x=2 produces the electrical length corresponding to the first and second pieces connected in series.
Referring to Fig. 4A, there is shown an impedance converter using an open stub as an impedance adjusting device in the microstrip line. The capacitance C of the open stub is represented by the following equation:
C = tan(2~L/Ag)/(27~fzo) (1), where L is a physical length, A g is an effective wave length, Z0 is a characteristic impedance, and f is a frequency. Such a capacitance C increases according to the length L such that the rate of increase in capacitance C becomes greater with increase in length L as shown by a curve of Fig. 4A. The capacitance C
is theoretically infinity at L = A g/4.
In the case of an open stub, assuming that the respective conductor pieces have physical lengths kl-kn and the first m conductor pieces are electrically connected in series, the length L of the open stub is: L = kl + k2 + ~-- + km~ m < n. Therefore, the respective physical lengths are determined so as to obtain adesiredcapacitancestep ~C,thatis,kl > k2-> ~-- -> kn,provided kl ~ kn. More specifically, the respective conductor pieces lla, llb, llc, and lld have physical lengths kl, k2, k3, and k4 each of which corresponds to the desired capacitance step ~C. The desired capacitance step ~C is not limited to a constant. The desired capacitance step ~C may vary according to the length L
CA 02228906 1998-0~-12 so that an enhanced fine adjustment can be achieved.
In this manner, as shown in Fig. 4B, the amount of change in impedance when the first conductor piece lla is electrically connected to the line conductor 10a (adjustment step x=l) is substantially the same as that when the second conductor piece llb is electrically connected to the first conductor piece lla (adjustment step x=2). In other words, in the case where the respective physical lengths kl-kn are determined so as to obtain a constant capacitance step ~C, the impedance Z is proportional to the adjustment step x. In the case of a short-stub impedance converter, the details will be described later.
OPEN-STUB IMPEDANCE CONVERTER
Hereinafter,Figs.5-8showthefirsttofourthembodiments, respectively, in the case of an open-stub impedance converter in the microstrip line.
ReferringtoFig.5,theimpedanceconverterlliscomprised of a plurality of conductor pieces lla-lld. As described before, the respective conductor pieces lla, llb, llc, and lld have physical lengths kl, k2, k3, and k4 each of which corresponds to the capacitance step ~C as shown in Fig. 4A. Here, the first conductor piece lla is connected to the line conductor 10a and the second conductorpiece llb is connectedto the first conductor piece llb by connection conductors 13. Therefore, the impedance converterllissettothephysicallengthL=k1+k2. Thefollowing equation is derived from the equation (1):
L = (Ag/2~)tan-l(2~fzoc) (2)-CA 02228906 1998-0~-12 ReferringtoFig.6,theimpedanceconverterlliscomprised of a line conductor member 14 directly connected to the line conductor lOa and a plurality of conductor pieces llb, llc and lld. As described before, the line conductor member 14 has a physical length of kl and the respective conductor pieces llb, llc, and lld have physical lengths k2, k3, and k4. Each of the lengths corresponds to the capacitance step ~C as shown in Fig.
4A. However, the impedance converter 11 as shown in Fig. 6 exhibits an impedance characteristic line upwardly shifted from the line of Fig. 4B by the amount of impedance corresponding to the physical length of kl in the graph of Fig. 4B. Here, since the conductor piece llb is connected to the line conductor member 14 by connection conductors 13, the impedance converter 11 is set to the physical length L = k1 + k2.
ReferringtoFig.7,theimpedanceconverterlliscomprised of a first section 11(1) and a second section 11(2) which are arranged in parallel. The first section 11(1) is comprised of four conductor pieces lla-lld which are the same as those in Fig.
5. The second section 11(2) is comprised of a plurality of conductor members 15 having the same physical length kc. As described before, the first section 11(1) linearly changes in impedance and the second section 11(2) non-linearly changes in impedance. Therefore, this embodiment may provide a rough impedance adjustment and a fine impedance adjustment.
ReferringtoFig.8,theimpedanceconverterlliscomprised of a first section 11(1) and a second section 11(2) which are CA 02228906 1998-0~-12 symmetric with respect to the line conductor 10a. The first section 11(1) is comprised of a plurality of conductor pieces lla-lld which are the same as those in Fig. 5. The second section 11(2) is also comprised of a plurality of conductor pieces lla'-lld' which are the same as those in Fig. 5. Here, the conductor pieces lla-llc are connected in series to the line conductor 10a by connection conductors 13. Therefore, the first section 11(1) is set to the physical length La = kl + k2 + k3.
Similarly, the conductor piece lla' is connected to the line conductor 10aby connection conductors 13. Therefore, the second section 11(2) is set to the physical length La' = kl'.
SHORT-STUB IMPEDANCE CONVERTER
Figs. 9 and 10 show the fifth and sixth embodiments, respectively, in the case of a short-stub impedance converter.
In this case, assuming that a short stub line includes a plurality of conductor pieces having physical lengths kl-kn, respectively, and the last (n-m) conductor pieces are connected in parallel to the grounded conductor by connection conductors, the length L of the short stub is: L = kl + k2 +-- + km~ m ~ n. In other words, the physical length L is determined depending on which conductor piece is connected to the grounded conductor. Therefore, the respective physical lengths are determined so as to obtain a desired impedance step ~C, that is, kl < k2 <~ <- kn~ provided kl ~ kn-Referring to Fig. 9, the impedance converter 11 is placed between the line conductor 10a andthe groundedconductor 10b with CA 02228906 1998-0~-12 directly connected to the line conductor lOa. The impedance converter 11 is comprised of a first section 16 having a physical length kc and a second section 17 which is connected to the first section 16 and extends parallel to the grounded conductor lOb.
A plurality of conductor pieces lla-lld are shaped on the second section 17 and the respective conductor pieces lla-lld have physical lengths kl, k2, k3, and k4 each corresponding to the capacitance step ~C as described above, that is, k1 ~ k2 <- k3 ~
k4, provided kl ~ k4. It should be noted that the first section 16 having a physical length kc is provided to avoid causing the distance between the second section 17 and the grounded conductor lOb to be long.
Here, the conductor pieces lla-llc and lla'-llc' are connected in series to the line conductor lOa and the grounded conductor lOb by connection conductors 13. Therefore, the impedance converter 11 is set to the physical length L = kc + k + k2. The fixed length kc of the first section 16 reduces the distance between the second section 17 and the grounded conductor lOb, resulting in a reduced length of connection wire.
Referring to Fig. 10, the impedance converter 11 is placed between the line conductor lOa andthe groundedconductor lOb with directly connected to the line conductor lOa. The impedance converterlliscomprisedofafirstsection18andasecondsection 19, and further a plurality of conductor pieces lla-llc, lld, and lla'-llc'whicharediscretelyplacedbetweenthefirstandsecond sections 18 and 19.
CA 02228906 1998-0~-12 The respective conductor pieces lla-llc provide physical lengths of kl, k2and k3,and other conductor pieces lla'-llc' also provide the same physical lengths k1, k2 and k3. Further, the conductor piece lld provides a physical length k4 as well as a part of the fixed length kc which is the distance between the line conductor lOa and the grounded conductor lOb. Each of the physical lengths kl, k2, k3, and k4corresponds to the capacitance step ~C as described above, that is, kl < k2 <- k3 ~ k4, provided k1 ~ k4-Here,theconductorpieceslla-llcareconnectedtothe line conductor lOa through the first section 18 by connection conductors 13, the conductor pieces llc and llc' are electrically connected to each other by conductor connection 13, and further the conductor pieces lla'-llc' are connected to the grounded conductor lOb through the second section 19 by connection conductors 13. Therefore, the impedance converter 11 is set to the physical length L = kc + 2(kl + k2 + k3).
EXAMPLE
Referring to Fig. 11, the impedance converter is comprised of a 0.8 mm-thick dielectric substrate which is made of polytetrafluoroethylene with a relative dielectric constant: ~
r = 2. An open stub is placed on the dielectric substrate. Here, the frequency of a signal is 6GHz.
To produce a capacitance step ~C of 0.2pF over a desired capacitance range from O to l.OpF, five conductor pieces lla-lle are needed. Substituting f = 6GHz,Ag = 35mm and ZO = 50Q
CA 02228906 1998-0~-12 intotheequation(2)yieldsL=5.77tan~l(1.88C)(mm). Therefore, when C=0.2, 0.4, 0.6, 0.8, and 1.0 (pF), L = 2.0, 3.5, 4.7, 5.4, and 6.0 (mm), respectively. The respective lengths k1-k5 of the conductorpieceslla-lleare2.Omm,1.6mm,1.lmm,0.8mm,andO.5mm.
In Fig. 11, dimensions are described when the line conductor lOa has a width of 2mm.
Since this example provides the constant capacitance step ~Cof 0.2pF, an easy andfine impedance adjustment canbe achieved by connecting a desired number of conductor pieces in series. It is the same with a short-stub impedance converter as described before.
Further, the capacitance step ~C may vary depending on which conductor piece is connected so that the impedance adjustment can be performed more easily and accurately.
Furthermore, the present invention may be applied to not only a microstrip line but also a coaxial line.
As described above, according to the present invention, a conductor pattern of the impedance converter is determined such that the amount of change in length is varied depending on the length sensitivity of impedance. Therefore, the optlmal adjustment of impedance can be easily achieved, resulting in dramatically reduced energy loss. Further, since the impedance matchingcanberapidlyachievedwithreducednumberofadjustment steps, the productivity is improved.
A conventionalimpedance adjustingcircuit is shown in Fig.
1, which is comprised of a microstrip line 1 and an impedance adjuster 2 which is further comprised of a plurality of conductor pieces 3a-3c each having the same physical length. The conductor pieces 3a-3c are placed in a line and they can be connected by CA 02228906 1998-0~-12 wire bonds 4 such that the physical (or electrical) length can be set to a desired value. In Fig. 1, for example, the first and second conductor pieces 3a and 3b are connected by wire bonds 4 to produce a physical length of 2Lo. Such a circuit has been described in Japanese Utility-model Unex~m;ned Publication No.
59-39501 and Japanese Patent Unex~mined Publication No. 61-133702.
These publications have further disclosed an improved impedance converting circuit capable of adjusting the impedance of a microstrip line. In the former Publication (No. 59-39501), the impedance converting circuit is provided with a microstrip line connected to an adjusting strip line which has an upwardly bent portion at an end thereof. The characteristic impedance is varied depending on capacitance determined by the amount of the bend. In the latter Publication (No. 61-133702), the characteristic impedance is adjusted by cutting a part of an open stub connected to the microstrip line.
Further,anothermicrowavecircuitcapableofadjustingthe impedance of a microstrip line has been disclosed in Japanese PatentUnex~minedPublicationNo.2-94902. Themicrowavecircuit is provided with an open stub and an adjusting strip line for adjusting the length of the open stub. The characteristic impedance is varied depending on the position at which the open stub is electrically connected to the adjusting strip line.
As described above, conventional impedance converting or adjusting circuits achieve the impedance matching by varying the CA 02228906 1998-0~-12 length of an open stub to produce a desired reactance.
However, the conventionalcircuitsprovide no quantitative analysisofthelengthoftheopenstub. Further,fromapractical point of view, there may be cases where it is difficult or impossible to set the impedance adjusting circuit to the optimal impedance.
SUMMARY OF THE INVENTION
The inventor found that an easy and fine adjustment of characteristic impedance can be achievedby changingthe physical length depending on the sensitivity of impedance of a stub. More specifically, asshowninFig.2,theamountofchangeinimpedance is not linear with respect to the length of a stub. Especially, it is dramatically changed in the vicinity of L = A /4, where ~ is an effective wave length of a signal passing through a microstrip. Therefore, in the case where the characteristic impedance is adjusted depending on the length of a stub, there are variations in sensitivity.
According to the present invention, a length changing step varies according to the sensitivity. More specifically, the higher the sensitivity, the shorter the length changing step. In this manner, the linear impedance characteristic with respect to the number of length changing steps is achieved, resulting in an easy and fine adjustment of characteristic impedance.
CA 02228906 1998-0~-12 In general, the impedance Z is expressed by the following equation: Z = g(L) ~ ~L + ~, Where L is a physical length of the impedance converter and~ and ~ are constant. Therefore, if the physical length L of a distributed constant impedance converter is not linear as expressed by L = f(x) ~ ax + b, where x is the number of length changing steps and a and b are constant, then it is possible to produce a linear relationship between the impedance Z and the number x of length changing steps. More specifically, the function f() such that Z = g(L) = g(f(x)) = px + q can be obtained.
According to the present invention, an impedance-adjustable conductor is electromagnetically connected between a signal conductor and a grounded or reference conductor and is comprised of a plurality of connection regions each providing a different impedance, wherein an impedance difference between adjacent ones of the connection regions is determined depending on a pattern of the impedance-adjustable conductor. The impedance difference may be substantially uniform between any adjacent ones of the connection regions.
According to another aspect of the present invention, the impedance-adjustable conductor is comprised of a plurality of connection regions each providing a different conductor length, wherein the impedance-adjustable conductor linearly changes in impedancedependingonnumberofconnectionregionseachconnected by a conductor. The impedance-adjustable conductor may have a linear characteristic of sensitivity of impedance with respect CA 02228906 1998-0~-12 to the amount of change in length determined by the number of connection regions each connected by a conductor.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view showing a conventional impedance converting device;
Fig. 2 is a graph showing changes in impedance with respect to a physical length of a stub;
Fig. 3 is a block diagram showing an impedance adjusting system employing an impedance converting device according to the present invention;
Fig. 4A is a diagram showing a capacitance changing characteristic of an open stub and the respective lengths of conductor pieces in an impedance converting device according to the present invention;
Fig. 4B is a graph showing the linear relation ship between the impedance and the number of adjustment steps in the impedance converting device of Fig. 4A;
Fig. 5 is aplanview showing an impedance convertingdevice CA 02228906 1998-0~-12 according to a first embodiment of the present invention;
Fig. 6 is aplanview showingan impedance converting device according to a second embodiment of the present invention;
Fig. 7 is aplanview showingan impedanceconverting device according to a third embodiment of the present invention;
Fig. 8 is aplan view showingan impedance converting device according to a fourth embodiment of the present invention;
Fig. 9 is aplanview showingan impedance converting device according to a fifth embodiment of the present invention;
Fig.10isaplanviewshowinganimpedanceconvertingdevice according to a sixth embodiment of the present invention; and Fig. 11 is a plan view showing a concrete example of the first embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 3, a microstrip/coaxial line 10 is comprised of a line conductor 10a which a signal passes through and a grounded (or reference) conductor 10b which is opposed to CA 02228906 1998-0~-12 the line conductor lOa through a dielectric. Further, a distributed constant impedance converter 11 according to the present invention electromagnetically connects the line conductor lOa and the grounded conductor lOb to achieve impedance conversion.
The impedance converter 11 has a plurality of connection regions which are selectively connected by conductors such as wirebonds, leads or other electrical connections. Such a connection step is controlled by an adjustment controller 12.
More specifically, when the adjustment controller 12 produces an adjustment step x which determines the number of connection regions, the corresponding connection regions are connected by connection conductors such as wirebonds or leads to produce a desired electrical length of the impedance converter. As described before, the impedance is not linear with respect to the electrical length but the adjustment step x.
Taking an open stub of a microstrip line as an example hereinafter, the impedance converter 11 is comprised of a plurality of conductor pieces discretely placedon the dielectric such that they are arranged in line in the vicinity of the line conductor lOa. The respective conductor pieces are shaped with varying in physical length according to a distance from the line conductor lOa.
When the adjustment controller 12 produces the adjustment step x=2, the first conductor piece is electrically connected to the line conductor lOa, and then the second conductor piece CA 02228906 1998-0~-12 adjacent to the first conductor piece is electrically connected to the first conductor piece. Therefore, the adjustment step x=2 produces the electrical length corresponding to the first and second pieces connected in series.
Referring to Fig. 4A, there is shown an impedance converter using an open stub as an impedance adjusting device in the microstrip line. The capacitance C of the open stub is represented by the following equation:
C = tan(2~L/Ag)/(27~fzo) (1), where L is a physical length, A g is an effective wave length, Z0 is a characteristic impedance, and f is a frequency. Such a capacitance C increases according to the length L such that the rate of increase in capacitance C becomes greater with increase in length L as shown by a curve of Fig. 4A. The capacitance C
is theoretically infinity at L = A g/4.
In the case of an open stub, assuming that the respective conductor pieces have physical lengths kl-kn and the first m conductor pieces are electrically connected in series, the length L of the open stub is: L = kl + k2 + ~-- + km~ m < n. Therefore, the respective physical lengths are determined so as to obtain adesiredcapacitancestep ~C,thatis,kl > k2-> ~-- -> kn,provided kl ~ kn. More specifically, the respective conductor pieces lla, llb, llc, and lld have physical lengths kl, k2, k3, and k4 each of which corresponds to the desired capacitance step ~C. The desired capacitance step ~C is not limited to a constant. The desired capacitance step ~C may vary according to the length L
CA 02228906 1998-0~-12 so that an enhanced fine adjustment can be achieved.
In this manner, as shown in Fig. 4B, the amount of change in impedance when the first conductor piece lla is electrically connected to the line conductor 10a (adjustment step x=l) is substantially the same as that when the second conductor piece llb is electrically connected to the first conductor piece lla (adjustment step x=2). In other words, in the case where the respective physical lengths kl-kn are determined so as to obtain a constant capacitance step ~C, the impedance Z is proportional to the adjustment step x. In the case of a short-stub impedance converter, the details will be described later.
OPEN-STUB IMPEDANCE CONVERTER
Hereinafter,Figs.5-8showthefirsttofourthembodiments, respectively, in the case of an open-stub impedance converter in the microstrip line.
ReferringtoFig.5,theimpedanceconverterlliscomprised of a plurality of conductor pieces lla-lld. As described before, the respective conductor pieces lla, llb, llc, and lld have physical lengths kl, k2, k3, and k4 each of which corresponds to the capacitance step ~C as shown in Fig. 4A. Here, the first conductor piece lla is connected to the line conductor 10a and the second conductorpiece llb is connectedto the first conductor piece llb by connection conductors 13. Therefore, the impedance converterllissettothephysicallengthL=k1+k2. Thefollowing equation is derived from the equation (1):
L = (Ag/2~)tan-l(2~fzoc) (2)-CA 02228906 1998-0~-12 ReferringtoFig.6,theimpedanceconverterlliscomprised of a line conductor member 14 directly connected to the line conductor lOa and a plurality of conductor pieces llb, llc and lld. As described before, the line conductor member 14 has a physical length of kl and the respective conductor pieces llb, llc, and lld have physical lengths k2, k3, and k4. Each of the lengths corresponds to the capacitance step ~C as shown in Fig.
4A. However, the impedance converter 11 as shown in Fig. 6 exhibits an impedance characteristic line upwardly shifted from the line of Fig. 4B by the amount of impedance corresponding to the physical length of kl in the graph of Fig. 4B. Here, since the conductor piece llb is connected to the line conductor member 14 by connection conductors 13, the impedance converter 11 is set to the physical length L = k1 + k2.
ReferringtoFig.7,theimpedanceconverterlliscomprised of a first section 11(1) and a second section 11(2) which are arranged in parallel. The first section 11(1) is comprised of four conductor pieces lla-lld which are the same as those in Fig.
5. The second section 11(2) is comprised of a plurality of conductor members 15 having the same physical length kc. As described before, the first section 11(1) linearly changes in impedance and the second section 11(2) non-linearly changes in impedance. Therefore, this embodiment may provide a rough impedance adjustment and a fine impedance adjustment.
ReferringtoFig.8,theimpedanceconverterlliscomprised of a first section 11(1) and a second section 11(2) which are CA 02228906 1998-0~-12 symmetric with respect to the line conductor 10a. The first section 11(1) is comprised of a plurality of conductor pieces lla-lld which are the same as those in Fig. 5. The second section 11(2) is also comprised of a plurality of conductor pieces lla'-lld' which are the same as those in Fig. 5. Here, the conductor pieces lla-llc are connected in series to the line conductor 10a by connection conductors 13. Therefore, the first section 11(1) is set to the physical length La = kl + k2 + k3.
Similarly, the conductor piece lla' is connected to the line conductor 10aby connection conductors 13. Therefore, the second section 11(2) is set to the physical length La' = kl'.
SHORT-STUB IMPEDANCE CONVERTER
Figs. 9 and 10 show the fifth and sixth embodiments, respectively, in the case of a short-stub impedance converter.
In this case, assuming that a short stub line includes a plurality of conductor pieces having physical lengths kl-kn, respectively, and the last (n-m) conductor pieces are connected in parallel to the grounded conductor by connection conductors, the length L of the short stub is: L = kl + k2 +-- + km~ m ~ n. In other words, the physical length L is determined depending on which conductor piece is connected to the grounded conductor. Therefore, the respective physical lengths are determined so as to obtain a desired impedance step ~C, that is, kl < k2 <~ <- kn~ provided kl ~ kn-Referring to Fig. 9, the impedance converter 11 is placed between the line conductor 10a andthe groundedconductor 10b with CA 02228906 1998-0~-12 directly connected to the line conductor lOa. The impedance converter 11 is comprised of a first section 16 having a physical length kc and a second section 17 which is connected to the first section 16 and extends parallel to the grounded conductor lOb.
A plurality of conductor pieces lla-lld are shaped on the second section 17 and the respective conductor pieces lla-lld have physical lengths kl, k2, k3, and k4 each corresponding to the capacitance step ~C as described above, that is, k1 ~ k2 <- k3 ~
k4, provided kl ~ k4. It should be noted that the first section 16 having a physical length kc is provided to avoid causing the distance between the second section 17 and the grounded conductor lOb to be long.
Here, the conductor pieces lla-llc and lla'-llc' are connected in series to the line conductor lOa and the grounded conductor lOb by connection conductors 13. Therefore, the impedance converter 11 is set to the physical length L = kc + k + k2. The fixed length kc of the first section 16 reduces the distance between the second section 17 and the grounded conductor lOb, resulting in a reduced length of connection wire.
Referring to Fig. 10, the impedance converter 11 is placed between the line conductor lOa andthe groundedconductor lOb with directly connected to the line conductor lOa. The impedance converterlliscomprisedofafirstsection18andasecondsection 19, and further a plurality of conductor pieces lla-llc, lld, and lla'-llc'whicharediscretelyplacedbetweenthefirstandsecond sections 18 and 19.
CA 02228906 1998-0~-12 The respective conductor pieces lla-llc provide physical lengths of kl, k2and k3,and other conductor pieces lla'-llc' also provide the same physical lengths k1, k2 and k3. Further, the conductor piece lld provides a physical length k4 as well as a part of the fixed length kc which is the distance between the line conductor lOa and the grounded conductor lOb. Each of the physical lengths kl, k2, k3, and k4corresponds to the capacitance step ~C as described above, that is, kl < k2 <- k3 ~ k4, provided k1 ~ k4-Here,theconductorpieceslla-llcareconnectedtothe line conductor lOa through the first section 18 by connection conductors 13, the conductor pieces llc and llc' are electrically connected to each other by conductor connection 13, and further the conductor pieces lla'-llc' are connected to the grounded conductor lOb through the second section 19 by connection conductors 13. Therefore, the impedance converter 11 is set to the physical length L = kc + 2(kl + k2 + k3).
EXAMPLE
Referring to Fig. 11, the impedance converter is comprised of a 0.8 mm-thick dielectric substrate which is made of polytetrafluoroethylene with a relative dielectric constant: ~
r = 2. An open stub is placed on the dielectric substrate. Here, the frequency of a signal is 6GHz.
To produce a capacitance step ~C of 0.2pF over a desired capacitance range from O to l.OpF, five conductor pieces lla-lle are needed. Substituting f = 6GHz,Ag = 35mm and ZO = 50Q
CA 02228906 1998-0~-12 intotheequation(2)yieldsL=5.77tan~l(1.88C)(mm). Therefore, when C=0.2, 0.4, 0.6, 0.8, and 1.0 (pF), L = 2.0, 3.5, 4.7, 5.4, and 6.0 (mm), respectively. The respective lengths k1-k5 of the conductorpieceslla-lleare2.Omm,1.6mm,1.lmm,0.8mm,andO.5mm.
In Fig. 11, dimensions are described when the line conductor lOa has a width of 2mm.
Since this example provides the constant capacitance step ~Cof 0.2pF, an easy andfine impedance adjustment canbe achieved by connecting a desired number of conductor pieces in series. It is the same with a short-stub impedance converter as described before.
Further, the capacitance step ~C may vary depending on which conductor piece is connected so that the impedance adjustment can be performed more easily and accurately.
Furthermore, the present invention may be applied to not only a microstrip line but also a coaxial line.
As described above, according to the present invention, a conductor pattern of the impedance converter is determined such that the amount of change in length is varied depending on the length sensitivity of impedance. Therefore, the optlmal adjustment of impedance can be easily achieved, resulting in dramatically reduced energy loss. Further, since the impedance matchingcanberapidlyachievedwithreducednumberofadjustment steps, the productivity is improved.
Claims (19)
1 5 What is claimed is:
1. A device comprising:
a signal conductor which a signal passes through;
a reference conductor placed at a distance from the signal conductor; and an impedance-adjustable conductor electromagnetically connected between the signal conductor and the reference conductor, the impedance-adjustable conductor comprising a plurality of connection regions each providing a different impedance, wherein an impedance difference between adjacent ones of the connection regions is determined depending on a pattern of the impedance-adjustable conductor.
1. A device comprising:
a signal conductor which a signal passes through;
a reference conductor placed at a distance from the signal conductor; and an impedance-adjustable conductor electromagnetically connected between the signal conductor and the reference conductor, the impedance-adjustable conductor comprising a plurality of connection regions each providing a different impedance, wherein an impedance difference between adjacent ones of the connection regions is determined depending on a pattern of the impedance-adjustable conductor.
2. The device according to claim 1, wherein the impedance difference is substantially uniform between any adjacent ones of the connection regions.
3. The device according to claim 1, wherein a distance between adjacent ones of the connection regions decreases with distance from the signal conductor along the pattern of the impedance-adjustable conductor.
4. The device according to claim 3, wherein the impedance-adjustable conductor comprises a plurality of discrete conductor pieces which decrease in length with distance from the signal conductor, wherein adjacent ones of the discrete conductor pieces are electrically connected through a connection region.
5. The device according to claim 1, wherein a distance between adjacent ones of the connection regions increases with distance from the signal conductor along the pattern of the impedance-adjustable conductor.
6. The device according to claim 5, wherein the impedance-adjustable conductor comprises a conductor line having the connection regions which increase in intervals with distance from the signal conductor along the conductor line.
7. The device according to claim 1, wherein a distance between adjacent ones of the connection regions increases with distance from both the signal conductor and the reference conductor along the pattern of the impedance-adjustable conductor.
8. The device according to claim 7, wherein the impedance-adjustable conductor comprises a plurality of discrete conductor pieces which increase in length with distance from both the signal conductor and the reference conductor, wherein adjacent ones of the discrete conductor pieces are electrically connected through a connection region.
9. A device comprising:
a signal conductor which a signal passes through;
a reference conductor placed at a distance from the signal conductor; and an impedance-adjustable conductor electromagnetically connected between the signal conductor and the reference conductor, the impedance-adjustable conductor comprising a plurality of connection regions each providing a different conductor length, wherein the impedance-adjustable conductor linearly changes in impedance depending on number of connection regions each connected by a conductor.
a signal conductor which a signal passes through;
a reference conductor placed at a distance from the signal conductor; and an impedance-adjustable conductor electromagnetically connected between the signal conductor and the reference conductor, the impedance-adjustable conductor comprising a plurality of connection regions each providing a different conductor length, wherein the impedance-adjustable conductor linearly changes in impedance depending on number of connection regions each connected by a conductor.
10. The device according to claim 9, wherein the impedance-adjustable conductor has a linear characteristic of sensitivity of impedance with respect to the amount of change in length determined by the number of connection regions each connected by a conductor.
11. The device according to claim 10, wherein a conductor length increases with increasing in sensitivity and decreases with decreasing in sensitivity.
12. The device according to claim 9, wherein the impedance-adjustable conductor is an open stub, wherein a conductor length decreases with distance from the signal conductor along the connection regions.
13. The device according to claim 9, wherein the impedance-adjustable conductor is a short stub, wherein a conductor length increases with distance from the signal conductor along the connection regions.
14. A high-frequency impedance converting device comprising:
a signal conductor which a signal passes through;
a reference conductor placed at a distance from the signal conductor; and a plurality of distributed constant members electromagnetically connected between the signal conductor and the reference conductor, at least one distributed constant member comprising a plurality of connection regions each providing a different physical length, wherein a difference between physical lengths of adjacent ones of the connection regions varies depending on number of connection regions each connected by a conductor.
a signal conductor which a signal passes through;
a reference conductor placed at a distance from the signal conductor; and a plurality of distributed constant members electromagnetically connected between the signal conductor and the reference conductor, at least one distributed constant member comprising a plurality of connection regions each providing a different physical length, wherein a difference between physical lengths of adjacent ones of the connection regions varies depending on number of connection regions each connected by a conductor.
15. The high-frequency impedance converting device according to claim 14, wherein at least one of the distributed constant members comprises a plurality of connection regions each providing a predetermined physical length.
16. The high-frequency impedance converting device according to claim 14, wherein two of the distributed constant members each comprises a plurality of connection regions each providing a different physical length, wherein the two distributed constant members are symmetric with the signal conductor.
17. A method for adjusting impedance of a device comprising a signal conductor which a signal passes through and a reference conductor placed at a distance from the signal conductor, the method comprising the steps of:
providing an impedance-adjustable conductor electromagnetically connected between the signal conductor and the reference conductor, the impedance-adjustable conductor comprising a plurality of connection regions each providing a different impedance, wherein an impedance difference between adjacent ones of the connection regions is determined depending on a pattern of the impedance-adjustable conductor; and adjusting the impedance by connecting a desired number of connection regions.
providing an impedance-adjustable conductor electromagnetically connected between the signal conductor and the reference conductor, the impedance-adjustable conductor comprising a plurality of connection regions each providing a different impedance, wherein an impedance difference between adjacent ones of the connection regions is determined depending on a pattern of the impedance-adjustable conductor; and adjusting the impedance by connecting a desired number of connection regions.
18. The method according to claim 17, wherein the impedance difference is substantially uniform between any adjacent ones of the connection regions.
19. A method for adjusting impedance of a device comprising a signal conductor which a signal passes through and a reference conductor placed at a distance from the signal conductor, the method comprising the steps of:
providing an impedance-adjustable conductor electromagnetically connected between the signal conductor and the reference conductor, the impedance-adjustable conductor comprising a plurality of connection regions each providing a different conductor length, wherein the impedance-adjustable conductor linearly changes in impedance depending on number of connection regions each connected by a conductor; and adjusting the impedance by connecting a desired number of connection regions.
providing an impedance-adjustable conductor electromagnetically connected between the signal conductor and the reference conductor, the impedance-adjustable conductor comprising a plurality of connection regions each providing a different conductor length, wherein the impedance-adjustable conductor linearly changes in impedance depending on number of connection regions each connected by a conductor; and adjusting the impedance by connecting a desired number of connection regions.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP023588/1997 | 1997-02-06 | ||
| JP9023588A JPH10224123A (en) | 1997-02-06 | 1997-02-06 | Impedance converter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2228906A1 true CA2228906A1 (en) | 1998-08-06 |
Family
ID=12114753
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2228906 Abandoned CA2228906A1 (en) | 1997-02-06 | 1998-02-05 | Impedance converting device |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0858124A1 (en) |
| JP (1) | JPH10224123A (en) |
| AU (1) | AU5299398A (en) |
| CA (1) | CA2228906A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102006003474B3 (en) * | 2006-01-25 | 2007-07-05 | Atmel Germany Gmbh | Device for transmitting electromagnetic signals between two functional units, has fields which are completely accessible from outside for producing electrically-conducting connections |
| JP4073456B2 (en) | 2006-01-30 | 2008-04-09 | 寛治 大塚 | Impedance converter |
| US7970037B2 (en) | 2009-06-10 | 2011-06-28 | Coherent, Inc. | Arrangement for RF power delivery to a gas discharge laser with cascaded transmission line sections |
| US20110285473A1 (en) * | 2010-05-24 | 2011-11-24 | Coherent, Inc. | Impedance-matching transformers for rf driven co2 gas discharge lasers |
| US8648665B2 (en) | 2010-10-06 | 2014-02-11 | Coherent, Inc. | Impedance-matching circuits for multi-output power supplies driving CO2 gas-discharge lasers |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4479100A (en) * | 1982-05-27 | 1984-10-23 | Raytheon Company | Impedance matching network comprising selectable capacitance pads and selectable inductance strips or pads |
| JPH0770887B2 (en) * | 1986-05-19 | 1995-07-31 | 日本電気株式会社 | Matching circuit for semiconductor devices |
| JPS6420701A (en) * | 1987-07-16 | 1989-01-24 | Fujitsu Ltd | High frequency amplifier |
| JPH0795646B2 (en) * | 1989-06-15 | 1995-10-11 | 松下電器産業株式会社 | High frequency semiconductor circuit adjustment method |
| JPH0653715A (en) * | 1992-07-30 | 1994-02-25 | Mitsubishi Electric Corp | Microwave amplifier |
-
1997
- 1997-02-06 JP JP9023588A patent/JPH10224123A/en active Pending
-
1998
- 1998-02-05 CA CA 2228906 patent/CA2228906A1/en not_active Abandoned
- 1998-02-06 EP EP98102133A patent/EP0858124A1/en not_active Withdrawn
- 1998-02-06 AU AU52993/98A patent/AU5299398A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| AU5299398A (en) | 1998-08-13 |
| JPH10224123A (en) | 1998-08-21 |
| EP0858124A1 (en) | 1998-08-12 |
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