JP2005217867A - Directional coupler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a directional coupler that carries excellent design properties and suits to a high integration, and to provide an apparatus using the same. <P>SOLUTION: In the appended drawing, 1a to 1d are resonators, wherein input/output terminals 2a to 2d and quarter-wave lines 3 to 6 are connected to each resonator by electric field connection. The amount of the electric field connection is set to Qeo, QeA, and QeB by using an external Q which are employed in filter design. Resonators are connected to the four input/output terminals in this way, and a circuit, in which these four pass-band filters are linked by a quarter-wave line, is formed on a wiring board or formed of a waveguide, a dielectric block or the like, thus a circuit or an apparatus providing intended characteristics of the directional coupler being obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a directional coupler used in a high frequency region such as a microwave and a millimeter wave, a high frequency module including the directional coupler, and a communication device.

  In recent years, research in a high frequency region, particularly in a field such as a quasi-millimeter wave and a millimeter wave, has attracted attention, and its practical application has been studied. One of the problems in increasing the frequency is that the electromagnetic field is disturbed in the line discontinuity. For example, in the case of a directional coupler using the H plane in a waveguide circuit, for example, the design of the branching part has a great influence on the overall characteristics, and the design is very difficult. A directional coupler called a two-branch line type using a quarter-wave line that is common in microstrip circuits has not been reported.

For this reason, a waveguide, particularly a directional coupler using the H-plane, has a coupling partition wall that shares the conductor walls that are the H-planes of the two rectangular waveguides. A directional coupler by providing a hole or the like and electromagnetically coupling two waveguides is often used. However, since all the terminal positions are in the same direction, there are few degrees of freedom in the arrangement of the entire circuit, which may be a problem for high integration.
JP-A-4-286202 JP-A-5-90810 Japanese Patent Laid-Open No. 11-308025

  The present invention provides a directional coupler excellent in design and suitable for high integration and a device using the same.

  The present invention solves the above-mentioned problem by inserting a band-pass filter (BPF) into a connection portion, that is, a branching portion between two quarter-wave lines and three lines of input / output terminals. That is, in a two-branch line type directional coupler that functions by combining four quarter-wave lines, it is configured by connecting a resonator or a plurality of resonators at least at one point of the branching portion. It is characterized in that a band pass filter is arranged.

  According to the present invention, it is possible to remove a high-level design property and unnecessary waves by being able to realize a directional coupler by using a filter design method that has accumulated a lot of technologies, and to freely select terminal positions. A directional coupler having the characteristics of a filter and a high-frequency circuit device to which the directional coupler is applied are obtained.

  The structure of the directional coupler by the waveguide H surface circuit which concerns on 1st embodiment is demonstrated with reference to FIG. In the figure, reference numerals 1a to d denote resonators, and input / output terminals 2a to 2d and quarter-wave lines 3 to 6 are connected to the respective resonators by electromagnetic coupling. The amount of electromagnetic coupling is Qeo, QeA, and QeB using the external Q used for filter design. In this way, a resonator is connected to four input / output terminals, and a circuit in which these four band-pass filters are connected by a quarter-wave line is configured on a wiring board or a waveguide, a dielectric block, etc. A circuit or device exhibiting the desired directional coupler characteristics is obtained.

  Next, it will be described below that the four-terminal circuit having the above configuration serves as a directional coupler. First, in order to simplify the analysis, it is assumed that the plane has symmetry with respect to the planes AA ′ and BB ′. By utilizing this fact, it is possible to analyze the entire circuit by analyzing a one-terminal quarter circuit cut off at two symmetry planes.

ここに、

とした。 First, FIG. 2 shows an equivalent circuit of a one-terminal circuit cut along two symmetry planes. The resonator is an LC series circuit. The coupling between the input / output line and the λ / 4 line and the resonator is Mo, MA, and MB, respectively, using mutual inductance. In this circuit, jA and jB are amounts that change in accordance with opening and shorting of the symmetry plane, and are expressed as follows.
(1) AA 'side; open, BB'side;
jA = −jZ _A cot (θ / 2), jB = −jZ _B cot (θ / 2)
(2) AA 'surface: Short circuit, BB' surface: Open
jA = jZ _A cot (θ / 2), jB = −jZ _B tan (θ / 2)
(3) AA 'surface: Open, BB' surface: Short circuit
jA = −jZ _A tan (θ / 2), jB = jZ _B cot (θ / 2)
(4) AA 'surface: Short circuit, BB' surface: Short circuit
jA = jZ _A tan (θ / 2), jB = jZ _B tan (θ / 2)
(Θ represents the electrical angle of the λ / 4 line section with respect to the frequency)
If only the center frequency is considered and the equivalent circuit of FIG. 2 is used, the normalized inherent admittance corresponding to the open and short of each symmetry plane is expressed by equation (1).

here,

It was.

の関係がある。回路全体の散乱行列は式（３）の散乱行列を用いて式(４)で表される。

Note that the admittance in the formula (1) is standardized by the characteristic admittance of the input / output line. The first superscript corresponds to the surface AA ′, the second corresponds to the surface BB ′, and is opened by e and shorted by o. To represent. This normalized intrinsic admittance and scattering matrix

There is a relationship. The scattering matrix of the entire circuit is expressed by Expression (4) using the scattering matrix of Expression (3).

また結合度を表すβは、

が得られ、

が得られる。このようにしてブランチラインカプラにおける結合度｜β｜が与えられれば、共振器の外部Ｑは一義的に決まり、方向性結合器が実現できる。 As a result of obtaining the scattering matrix by the above procedure, the condition that this circuit functions as a directional coupler, that is, the matching condition (| S11 | = 0) of the terminal (1) and the separation between the terminals (1)-(2) The condition (| S21 | = 0) is expressed by Equation (5).

Β representing the degree of binding is

Is obtained,

Is obtained. If the degree of coupling | β | in the branch line coupler is given in this way, the external Q of the resonator is uniquely determined, and a directional coupler can be realized.

が得られる。 In the case of 3 dB coupling, that is, β = 1 / √2, immediately from equations (7) and (8)

Is obtained.

  FIG. 3 shows the frequency characteristic calculation result when the center frequency is 24 GHz and Qe0 = 20 using the parameter of the equation (9). The horizontal axis represents the frequency range from 23 GHz to 25 GHz, and the vertical axis represents the absolute value of the scattering parameter in decibels. It can be seen that the inputs from terminal (1) are matched, not output from terminal (2), and equal power is distributed from terminals (3) and (4). Thus, it can be seen that a directional coupler can be obtained by this circuit configuration.

  Next, the structure of the directional coupler which concerns on 2nd embodiment is demonstrated with reference to FIG. FIG. 4 shows a configuration using a three-stage bandpass filter instead of the resonator used in the directional coupler of FIG. In FIG. 4, D1, D2, and D3 represent resonators, and the resonators are electromagnetically coupled. The amount of binding is expressed using k12 and k23. Thus, using a bandpass filter instead of the resonator at the branching portion is effective for widening the band. For example, assuming a three-stage filter as shown in FIG. 5 as the basic filter characteristics, a filter having a center frequency of 24 GHz and a bandwidth of 1 GHz is designed. According to the classic filter design method, the coupling coefficients obtained at this time are k12 = k23 = 0.038 and Qe = 24.8. FIG. 5 shows the result of calculating the frequency characteristics of the filter using these parameters.

Based on this parameter, so that the external Q satisfies the relationship of equation (9),
Qe0 = QeA = 24.8 (10)
QeB = 17.5 (11)
k12 = k23 = 0.038 (12)
FIG. 6 shows the frequency characteristic calculation result of the branch line coupler of FIG. The characteristics of the directional coupler are realized over the 1 GHz band such that the input and output are matched, separated from the terminal (1), and equally distributed to the terminals (3) and (4). Further, the reflection characteristics well reflect the reflection characteristics of the basic filter characteristics. From this, it is understood that the reflection and separation characteristics of the directional coupler can be designed by designing the filter.

  The basic configuration of the present invention is as described above, and an example in which this is configured by an H-plane cavity waveguide type circuit will be described in detail. Waveguides are used for the resonator and the input / output terminals, and the size of the waveguide is 8.636 × 4.318. Each coupling coefficient and the external Q are adjusted so as to satisfy the expressions (10) to (12) according to the iris length. FIG. 8 shows the calculation result by the finite element method.

  A directional coupler according to the fourth embodiment will be described with reference to FIG. FIG. 9 is designed so that all the terminals are directed in different directions by changing the directions of the input / output terminals of the waveguide type directional coupler of FIG. 7 by 90 degrees. FIG. 10 shows the results of actual trial manufacture and measurement. By providing a degree of freedom in the terminal direction, it is possible to optimize the arrangement of the circuit that follows, and to achieve high integration of the circuit.

A directional coupler according to the fifth embodiment will be described with reference to FIG. In FIG. 11, the resonator has four stages, the center frequency is 24 GHz, the frequency band is 1.1 GHz, and the coupling degree is selected to be −10 dB. At this time, the coupling coefficient is k12 = k34 = 3.81% from equation (8).
k23 = 3.01%
Qe0 = 24.2, QeA = 72.6, QeB = 23.0. The result of designing this configuration using an H-plane waveguide circuit is shown in FIG. In this way, the design is possible even if it is not equally distributed.

  A directional coupler according to the sixth embodiment will be described with reference to FIG. FIG. 13 shows an example in which the transmission line and the λ / 4 line are configured by microstrip lines, and a dielectric resonator is used as a resonator at the branching portion. Since the circuit configuration shown in the present application is designed using a parameter called external Q, it is possible to design even these two different combinations. This combination is possible even in the case of a slot line and a coaxial line, a waveguide and a coplanar line, and the like. FIG. 14 shows an embodiment of a circuit in which some of the terminals of the directional coupler of FIG. 13 are constituted by slot lines.

  The structure of the directional coupler according to the present invention is not limited to that described above, and can be used for an NRD guide or a slot line as shown in FIG. FIG. 16 shows an embodiment in which directional couplers according to the present invention are cascade-connected to form a ladder type two-branch line type directional coupler. FIG. 17 shows an example in which the directional coupler according to the present invention is used as a receiver of a communication module. When this directional coupler is applied to a system, the terminal position can be arbitrarily selected, which is effective for high circuit integration.

Circuit diagram showing an embodiment of the present invention Partial equivalent circuit diagram Illustration of its characteristics Circuit diagram showing another embodiment of the present invention Illustration of its characteristics Illustration of its characteristics The top view which shows the other Example of this invention Illustration of its characteristics The top view which shows the other Example of this invention Illustration of its characteristics The perspective view which shows the other Example of this invention. Illustration of its characteristics The perspective view which shows the other Example of this invention. The perspective view which shows the other Example of this invention. The perspective view which shows the other Example of this invention. Block diagram showing another embodiment of the present invention The top view which shows the other Example of this invention

Explanation of symbols

1: Resonator 2: Output terminals 3-6: 1/4 wavelength line

Claims (3)

  A two-branch line type directional coupler that functions by combining four quarter-wave lines, and a band pass configured by connecting a plurality of resonators or resonators at at least one location of the branching section A directional coupler in which a filter is arranged. The two-branch line type directional coupler according to claim 1, which functions by combining four quarter-wave lines, and a resonator or a filter in which a plurality of resonators are connected, an input / output line, and two λ A directional coupler having the following relationship between these parameters when the / 4 line is electromagnetically coupled and the coupling amounts are Qe0, QeA, and QeB, respectively.

  A directional coupler arranged such that the orientation of any two output terminals differs by 90 degrees without adding a bend or a circuit equivalent thereto.

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