JP4224909B2 - Line conversion structure, high-frequency circuit, and wireless device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a line conversion structure that performs line conversion between a dielectric line and a substrate line, a high-frequency circuit including the line conversion structure, and a radio apparatus.
[0002]
[Prior art]
Conventionally, a dielectric line with a small transmission loss is used as a transmission line in a millimeter wave band or the like. In particular, a non-radiative dielectric line (hereinafter referred to as “NRD guide”) having a dielectric strip portion disposed between parallel plates as a propagation region and a blocking region between outer parallel plates as a non-radiation property and low loss. Utilizing this property, it is applied to various small millimeter-wave circuit devices.
[0003]
However, not all transmission lines can be configured as dielectric lines such as NRD guides. For example, when an oscillator or a mixer using a dielectric line as a signal transmission path is configured, a Gunn diode or a Schottky barrier diode is used. It is necessary to mount electronic components such as the above on the substrate, and to configure a line for supplying a bias voltage or propagating a signal to the substrate on the substrate. Therefore, for example, as shown in Japanese Patent Laid-Open No. 10-75109, a suspended line is formed by inserting a substrate on which a conductor pattern is formed between parallel plates of a dielectric line. Are to be combined.
[0004]
[Problems to be solved by the invention]
In the NRD guide, as shown in FIG. 9A, the LSM mode in which the magnetic field is parallel to the boundary between the dielectric strip and air, and as shown in FIG. 9B, the magnetic field is a cross section of the dielectric strip. Are roughly divided into LSE modes that are substantially parallel to each other. Both of these modes are non-radioactive and can coexist with one NRD guide, but the LSM mode is usually used because of its low loss.
[0005]
However, when line conversion is performed by combining the above-described suspended line and the NRD guide, an unnecessary mode is generated in addition to the LSM mode, which is the main propagation mode of the NRD guide, due to the asymmetry of the suspended line part. In some cases, the output of the LSM mode was lowered. One of the unnecessary modes is the LSE mode, and the other one is as shown in FIG. 9C, in which the magnetic field is parallel to the conductor plate and the electric field is from one conductor plate to the other conductor plate. It is a parallel flat plate mode.
[0006]
Japanese Patent Laid-Open No. 63-185101 and Japanese Patent Laid-Open No. 9-219608 have been proposed to prevent loss caused by mode conversion from the LSM mode to another unnecessary mode in the discontinuous portion of the NRD guide line. There are mode suppressors for NRD guides. However, all of these mode suppressors are LSE mode suppressors and have no effect on the parallel plate mode.
[0007]
Here, for comparison with the embodiments of the present invention described later, FIG. 10 and FIG. 11 show a line conversion structure between a substrate line and a dielectric line according to the prior art and its characteristics.
[0008]
FIG. 10B is a perspective view with the upper conductor plate removed, and FIG. 10A is a top view in the state shown in FIG. In FIG. 10, reference numeral 1 denotes a lower conductor plate, and 3 denotes a dielectric strip fitted in a groove formed in the lower conductor plate 1. A groove is also formed in the upper conductor plate (not shown), and the upper conductor plate is overlaid on the lower conductor plate 1 so that the dielectric strip 3 is fitted into the groove. The upper and lower conductor plates and the dielectric strip 3 constitute an NRD guide. Reference numeral 4 denotes a substrate having a conductor pattern 5 formed on the upper surface thereof. A portion where the bottom surface of the substrate 4 is in contact with the lower conductor plate 1 functions as a microstrip line, and a portion where the bottom surface is not in contact functions as a suspended line. A part of the dielectric strip 3 is divided into upper and lower parts, and a part of the substrate 4 is inserted into the part.
[0009]
FIG. 11 shows transmission characteristics and reflection characteristics of the line conversion structure shown in FIG. Here, S11 is the reflection coefficient of the TEM mode at the (1) end of the substrate line, S21 (LSM) is the transmission coefficient of the LSM01 mode from the (1) end of the substrate line to the (2) end of the NRD guide, and S21 (parallel). The flat plate primary) is the transmission coefficient of the primary mode of the parallel plate from the end (1) of the substrate line to the end (2) of the NRD guide, and S21 (parallel plate secondary) is from the end of the substrate line (1). This is the transmission coefficient of the second-order mode of the parallel plate to the end (2) of the NRD guide.
[0010]
When the line conversion between the microstrip line and the NRD guide is performed via the suspended line in this way, the conversion to the parallel plate mode is increased and the conversion loss is increased.
[0011]
An object of the present invention is to prevent a conversion to an unnecessary parallel plate mode in a line conversion section between a substrate line and a dielectric line, thereby improving a line conversion efficiency, and a high-frequency circuit and a radio using the line conversion structure To provide an apparatus.
[0012]
[Means for Solving the Problems]
In the line conversion structure according to the present invention, a dielectric line in which a dielectric strip is disposed between two substantially parallel conductor surfaces and a substrate on which a conductor pattern is formed are disposed between two substantially parallel conductor surfaces. A substrate coupling line, and a conductor pattern formed on the substrate is disposed near or overlapping a part of the dielectric strip to provide a line coupling portion between the dielectric line and the substrate line. At the same time, a side wall is provided on the side of the dielectric strip in the line coupling portion at an interval equal to or less than a half wavelength of the first parallel plate mode in the used frequency band generated between the two conductor surfaces.
[0013]
As described above, since the interval between the side walls in the line coupling portion is equal to or less than the half wavelength of the first-order parallel plate mode in the used frequency band, the parallel plate mode in the used frequency band is the side wall on the side of the dielectric strip in the line coupling portion. It can no longer exist in between. Therefore, conversion to the parallel plate mode does not occur at the time of line conversion from the substrate line to the dielectric line or from the dielectric line to the substrate line, and conversion loss due to this does not occur.
[0014]
In the line conversion structure according to the present invention, an impedance matching portion having a substantially larger interval between the side walls than the line coupling portion is provided between the line coupling portion and the dielectric line. Thereby, reflection at the boundary between the line coupling part and the dielectric line having different line impedances is suppressed to increase line conversion efficiency, and adverse effects due to reflection are prevented.
[0015]
The high-frequency circuit according to the present invention includes the above-described line conversion structure, and includes a dielectric line and a substrate line connected to the line conversion structure. For example, by mounting a Gunn diode or Schottky barrier diode on a substrate and performing line conversion between the substrate line and the dielectric line, an oscillator using the dielectric line as an output line or a mixer using the dielectric line as an input line And so on.
[0016]
Furthermore, a radio apparatus according to the present invention includes the above-described high frequency circuit, and constitutes a radio apparatus using a dielectric line as a transmission path for a transmission signal or a reception signal. For example, a millimeter wave radar module using a dielectric line as a transmission / reception signal transmission path and an oscillator or a mixer on the substrate is formed.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
First, the structure of the line converter according to the first embodiment will be described with reference to FIG. 1 and FIG.
FIG. 1 is a perspective view of the main part of the line converter, (A) is a perspective view of the line converter part, and (B) is a perspective view in a state where the upper conductor plate 2 is removed from the state shown in (A). FIG. In FIG. 1, 3 and 3 'are dielectric strips. Reference numeral 1 denotes a lower conductor plate, which is provided with a groove indicated by g, and a dielectric strip 3 'is fitted into the groove g. Grooves indicated by g are also formed in the upper conductor plate 2 so that the dielectric strips 3 are fitted into the grooves, and the dielectric strips 3 and 3 'are vertically aligned so as to overlap each other. The conductor plates 1 and 2 are laminated.
[0018]
2A is a top view in the state shown in FIG. 1B, and FIG. 2B is the axis of the dielectric strips 3 and 3 ′ in the state shown in FIG. FIG. 5 is a cross-sectional view taken along a plane that passes through and perpendicular to the upper and lower conductor plates. FIG. 2C is a perspective view showing the structure of the substrate used in this line converter. In FIG. 2, 4 is a dielectric substrate, and a conductor pattern 5 is formed on the upper surface thereof. As shown in FIG. 1B, the lower conductor plate 1 is provided with a recess for supporting the substrate 4 between the dielectric strips 3 and 3 ', and the substrate 4 is disposed in the recess. is doing. The vicinity of the portion where the substrate 4 and the dielectric strips 3 and 3 'overlap is a line coupling portion.
[0019]
As shown in FIG. 2A, the lower conductor plate 1 is formed with side walls w on both sides of the dielectric strips 3 and 3 ′ at positions spaced apart from the dielectric strip 3 by a predetermined distance. A portion where the distance between the dielectric strips 3, 3 'and the side wall w is d1 is a normal NRD guide portion. In the line coupling portion, the distance between the dielectric strips 3 and 3 ′ and the side wall w is substantially zero. Therefore, this portion is surrounded by the lower conductor plate 1 and the upper conductor plate 2 at the top, bottom, left and right of the dielectric strips 3 and 3 ′, and acts as a dielectric loaded waveguide (hereinafter referred to as “DWG”). . Between the NRD guide portion and the line coupling portion, there is provided an impedance conversion portion in which the distance between the dielectric strips 3 and 3 ′ and the side wall w is set to be smaller than d1.
[0020]
Here, assuming that the impedance of the DWG part is Z1 and the impedance of the NRD guide part is Z2, the impedance Zo of the impedance converter is Zo = √ (Z1 * Z2)
If the interval do is determined so as to satisfy the relationship, the impedance matching between the DWG and the NRD guide is optimal.
[0021]
The dimensions of each part of the mode converter are as follows when represented by the symbols shown in FIGS.
a = 1.8 mm, b = 1.2 mm, c = 0.8 mm, d1 = 0.8 mm, do = 0.1 mm, g = 0.5 mm, Lm = 1.22 mm, Lc = 1.0 mm
The dielectric strip 3 has a relative dielectric constant of 2.04, and the dielectric substrate 4 has a relative dielectric constant of 2.3.
[0022]
Here, the half wavelength in the 73 GHz band which is the frequency band to be used in the primary parallel plate mode determined by the interval c between the upper and lower conductor plates is 2.06 [mm]. On the other hand, in the line coupling part, the interval b between the side walls is narrower than the above half-wavelength, and therefore there is no primary parallel plate mode in this line coupling part in the frequency band to be used. Therefore, when line conversion is performed from the microstrip line to the NRD guide via the DWG, or when line conversion is performed from the NRD guide to the mode of the microstrip line via the DWG, accompanying the conversion to the parallel plate mode There is no loss.
[0023]
The impedance converter shown in FIG. 2A performs impedance matching between the DWG portion and the normal NRD guide portion. That is, if the NRD guide having the distance d1 between the dielectric strip 3 and the side wall w is connected to the DWG suddenly, the impedance mismatch occurs due to the difference in the line impedance between the two lines, and the electromagnetic wave is generated at the boundary. Although reflection occurs, the reflected wave from the impedance converter in the DWG direction is provided by providing a discontinuous part of the line impedance in two steps at the input part and the output part of the impedance converter and determining the interval appropriately. , And the reflected wave from the impedance converter in the direction of the NRD guide is canceled, and the influence of the reflected wave is almost eliminated. As a result, impedance matching is achieved.
[0024]
Here, the length Lm of the impedance converter is set to 1.22 mm, and the wavelength in the frequency band used by the electromagnetic wave propagating through this portion is set to ¼ wavelength, that is, half-wave in a round trip.
[0025]
FIG. 3 shows the transmission characteristics and reflection characteristics of the line converter according to the first embodiment. Here, S11 is the reflection coefficient of the TEM mode at the (1) end of the substrate line, S21 (LSM) is the transmission coefficient of the LSM01 mode from the (1) end of the substrate line to the (2) end of the NRD guide, and S21 (parallel plate) “Primary” is the transmission coefficient of the first-order mode of the parallel plate from the end (1) of the substrate line to the end (2) of the NRD guide.
[0026]
In this way, a very small transmission coefficient can be obtained in the 73 GHz band that is the used frequency band. Further, the transmission coefficient to the first parallel plate mode only appears in a high frequency band of 78 to 80 GHz, and conversion to the parallel plate mode in the used frequency band does not occur. Compared with the conventional example shown in FIG. 11, it can be seen that the transmission coefficient S21 (LSM) at the same frequency as the reflection coefficient S11 is small, and the conversion loss is small. The peak of the reflection coefficient S11 occurs at 78 GHz, and S11 tends to increase in a frequency region lower than 72 GHz. This is due to the deviation from the adaptive frequency of the impedance converter. It does not affect the frequency band used.
[0027]
Next, the configuration of three line converters having different configurations of the impedance converter will be described with reference to FIGS.
In these drawings, (B) is a perspective view with the upper conductor plate removed, and (A) is a top view in that state. In the example shown in FIG. 4, the impedance converter has a structure in which the distance between the upper and lower conductor plates (height of the NRD guide blocking region) is narrower than the NRD guide portion as the transmission path. With this structure, reflection is generated at both ends of the impedance conversion unit in the same manner as in the first embodiment, and the reflected wave is canceled out by combining the two reflected waves, and impedance matching is achieved.
[0028]
In the example shown in FIG. 5, in the impedance conversion section, the distance between the side portions and the side walls of the dielectric strips 3 and 3 ′ is changed from 0 to d1 in a tapered shape.
[0029]
In the example shown in FIG. 6, in the impedance conversion unit, the interval between the upper and lower conductor plates in the blocking region of the NRD guide is changed from 0 to c in a tapered shape.
[0030]
In any case, a discontinuous part of the line impedance is generated in two stages at the input part and the output part of the impedance conversion part, and the reflected wave from the impedance conversion part in the DWG direction by appropriately determining the interval, and The reflected waves from the impedance converter in the NRD guide direction are canceled out, and the influence of the reflected waves is almost eliminated. Thereby, impedance matching is taken.
[0031]
Next, the configuration of an oscillator using the NRD guide as an output transmission path will be described with reference to FIG.
FIG. 7 is a top view with the upper conductor plate 2 removed. In FIG. 7, a conductor pattern 5 as a line connecting the Gunn diode 6 and a bias line 7 for supplying a bias voltage to the Gunn diode 6 are formed on the upper surface of the substrate 4. By applying a DC bias voltage to the Gunn diode 6 through the bias line 7, the Gunn diode 6 oscillates a predetermined millimeter wave signal, propagates through the microstrip line by the conductor pattern 5, and passes through the DWG to the NRD guide. Are propagated in LSM mode.
[0032]
Next, an example of the millimeter wave radar module will be described with reference to FIG.
In FIG. 8, the “oscillator” has the conductor pattern 5 shown in FIG. 7 as a main line, a dielectric resonator coupled to the conductor line, and a variable reactance element loaded on the sub-line coupled to the dielectric resonator. Thus, the oscillation frequency can be modulated by the control voltage for the variable reactance element. The “isolator” is a third terminal of the circulator by the NRD guide that is resistance-terminated. The “coupler” is obtained by bringing two NRD guide dielectric strips close to each other, and extracts the transmission signal Tx and the local signal Lo. The “circulator” is a 3-port circulator with an NRD guide. The “mixer” inputs the local signal Lo branched from the coupler and the received signal Rx from the circulator through the NRD guide, converts it into a substrate line, and converts it to a substrate line by a Schottky barrier diode provided on the substrate. Convert to intermediate frequency signal. The “antenna” includes a dielectric resonator coupled to the NRD guide as a primary radiator, and is constituted by the primary radiator and a dielectric lens.
[0033]
In such a millimeter wave radar module, a substrate on which circuit patterns for an oscillator and a mixer are formed, a dielectric strip, and a dielectric resonator as a primary radiator are arranged between upper and lower conductor plates, and further, primary radiation is provided. The dielectric lens is arranged at a position away from the container by a predetermined distance.
[0034]
In FIG. 8, the oscillation signal of the oscillator propagates along the path of the isolator → coupler → circulator → antenna and is radiated as the transmission signal Tx, and the reflected wave from the object is propagated along the path of the antenna → circulator → mixer and becomes the reception signal Rx. Input to the mixer. At the same time, the local signal Lo from the coupler is supplied to the mixer. As a result, the intermediate frequency signal IF is extracted from the mixer. The signal processing circuit using the millimeter wave radar module shown in FIG. 8 detects the distance to the object and the relative velocity of the object from the modulation signal applied to the oscillator and the obtained IF signal.
[0035]
As a high-frequency circuit using a dielectric line and a substrate line, it can be similarly applied to a diode switch, an amplifier, and the like in addition to the oscillator and mixer described above. In other words, if a substrate line to which a switching diode is connected is provided on the substrate and the substrate line is coupled at a predetermined position of the dielectric strip of the NRD guide, signal transmission in the NRD guide is switched by switching of the diode. An NRD guide switch circuit can be configured.
[0036]
Further, if a substrate line to which an amplifying transistor is connected is provided on the substrate and the substrate line is coupled in the vicinity of the end of the dielectric strip of the NRD guide, the signal amplified by the transistor is transmitted to the NRD guide. Can be configured as a transmission line.
[0037]
Even in such a high-frequency circuit, the line converter between the dielectric line and the substrate line may be configured as shown in FIGS.
[0038]
【The invention's effect】
According to the first aspect of the present invention, when the line is converted from the substrate line to the dielectric line, or from the dielectric line to the substrate line, the conversion to the parallel plate mode is prevented, and the line conversion is performed with low loss. It can be carried out.
[0039]
According to the second aspect of the present invention, reflection at the boundary between the line coupling portion and the dielectric line having different line impedances is suppressed, and the line conversion efficiency is further increased. Moreover, the bad influence by reflection can be prevented.
[0040]
According to the third aspect of the present invention, for example, a Gunn diode or a Schottky barrier diode is mounted on a substrate, and line conversion between the substrate line and the dielectric line is performed, whereby the dielectric line is used as the output line. An oscillator, a mixer using a dielectric line as an input line, and the like can be easily configured together with a line converter of a substrate line and a dielectric line, and the overall size can be reduced.
[0041]
According to the fourth aspect of the present invention, for example, a millimeter wave radar module in which a dielectric line is used as a transmission / reception signal transmission path and an oscillator or a mixer is formed on a substrate portion, the transmission of the transmission signal or the reception signal is performed on the dielectric line. A wireless device used as a road can be easily configured.
[Brief description of the drawings]
FIG. 1 is a perspective view of a line converter according to a first embodiment. FIG. 2 is a diagram showing a configuration of each part of the line converter. FIG. 3 is a diagram showing characteristics of the line converter. FIG. 5 is a diagram showing a structure of a line converter according to the second embodiment. FIG. 5 is a diagram showing a structure of the line converter according to the third embodiment. FIG. 6 is a diagram showing a structure of the line converter according to the fourth embodiment. FIG. 7 is a diagram showing a configuration of an oscillator according to a fifth embodiment. FIG. 8 is a diagram showing a configuration of a millimeter wave radar module according to the sixth embodiment. FIG. 9 is a diagram showing states of various transmission modes. FIG. 10 is a diagram showing the structure of a line converter according to the prior art. FIG. 11 is a diagram showing the characteristics of the line converter according to the prior art.
1-lower conductor plate 2-upper conductor plate 3, 3'-dielectric strip 4-substrate 5-conductor pattern 6-Gun diode 7-bias line w-side wall

Claims (4)

A dielectric line having a dielectric strip disposed between two substantially parallel conductor surfaces; and a substrate line having a substrate having a conductor pattern formed between two substantially parallel conductor surfaces;
The substrate is arranged at a position where a conductor pattern formed on the substrate is close to or overlaps a part of the dielectric strip, a line coupling portion between the dielectric line and the substrate line is provided, and the two conductors occur between the surfaces, the half-wavelength spacing of the primary of the parallel plate mode in the used frequency band, Ri formed by providing a side wall on the side of the dielectric strip in the line coupling section, the line coupling section A line conversion structure for converting the dielectric line and the substrate line via a line.   2. The line conversion structure according to claim 1, wherein an impedance matching portion is provided between the line coupling portion and the dielectric line so that an interval between the side walls is substantially wider than that of the line coupling portion.   A high-frequency circuit comprising the line conversion structure according to claim 1, comprising a dielectric line and a substrate line connected to the line conversion structure.   A radio apparatus comprising the high-frequency circuit according to claim 3, wherein the dielectric line is a transmission path for a transmission signal or a reception signal.

Images