JP3385701B2 - Non-reciprocal circuit device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-reciprocal circuit device, for example, an isolator in which a non-reflection terminator is connected to any one port of a three-port circulator. I. L. An improved circuit configuration that can broaden the isolation characteristics while avoiding deterioration of characteristics, and can also respond to downsizing of components, and eliminates the need to adjust electrical characteristics to reduce costs. About. 2. Description of the Related Art In general, isolators employed in VHF, UHF, and SHF bands have a function of passing a signal only in a transmission direction and preventing transmission in a reverse direction. It is used in a transmission circuit of a mobile communication device such as a car phone. FIG. 3 shows a basic equivalent circuit of a general lumped constant type isolator. In this isolator 1, three center conductors 2 to 4 are arranged on one main surface of a ferrite 5 so as to cross each other at an angle of 120 degrees while being electrically insulated from each other. Connect to earth,
The matching capacitors C1 to C3 are connected to the other ends. A non-reflective terminating resistor (termination) R is connected to any one of the ports P3 of the center conductors 2 to 4, and the cold end of the resistor R is connected to the ground. It is configured to apply a DC magnetic field Hex for bias. The isolator 1 has a function of transmitting a signal from the port P1 to the port P2, absorbing a reflected wave entering from the port 2 by the terminating resistor R, and preventing transmission to the port P1. This prevents unnecessary waves from entering the power amplifier and the like. By the way, in the conventional isolator 1 described above,
Since the number of component elements constituting the circuit is small, the loss in the element is small, which is advantageous for reducing the loss.
I. L. The characteristics (pass characteristics) and the isolation characteristics (reverse attenuation characteristics) are relatively narrow band characteristics.
For this reason, depending on the frequency of the reflected wave, it may not be possible to absorb the reflected wave or block transmission to the port P1. As a result, there is a problem that intermodulation distortion is generated and noise is likely to be caused. [0006] Such I. L. In order to improve the characteristics and the isolation characteristics, it is conceivable to increase the bandwidth by adding a band-widening element to the ports P1 to P3 of the center conductors 2 to 4 and the ground plane of the ferrite. [0007] However, when a broadband element is connected to each of the ports and the ground plane, as shown in FIG. 4, the isolation characteristics (see FIG. 4 (b)) are not problematic. I. L. In the characteristics (see FIG. 4A), there is a problem that the peak value a of the operating center frequency f1 decreases and the characteristics deteriorate. This is due to the fact that the above element is connected to each port line through which a signal passes or to the ground plane of the ferrite, and the insertion loss increases accordingly. Here, in order to solve the above problem, FIG.
As shown in the figure, L (inductance), C '
(Capacitor) is connected to the port P
It is conceivable to connect in series between 3 and the terminating resistor R. Thereby, I.I. L. Deterioration of characteristics can be avoided, and the absorption band of the reflected wave can be expanded. However, since the matching circuit 6 is composed of a three-dimensional coil and a capacitor, it cannot cope with downsizing of components, and the constants are liable to be unstable.
There is a problem that the cost is increased due to the necessity of fine adjustment by trimming or the like, and improvement in this respect is demanded. The present invention has been made in view of the above-mentioned conventional circumstances. L. Provided is a non-reciprocal circuit device that can achieve a wide band of isolation characteristics while avoiding deterioration of characteristics, can also cope with downsizing of components, and can reduce costs by eliminating the need to adjust electrical characteristics. It is intended to be. According to the present invention, there is provided a non-reciprocal circuit device in which a terminator is connected to any one port of a three-port circulator. When trying to widen the bandwidth of the
The line length is (2n + 1) / 4 · λg (n
Is an integer, and λg is a transmission line having a wavelength within the transmission line. One end of the transmission line is connected to the terminator, and the other end is open or has high impedance. Here, a coaxial line, a microstrip line, a triplate strip line, a coplanar line, a suspended strip line, a waveguide, an NRD guide, or the like can be adopted as the transmission line. Here, in the present invention, the case where the impedance is high includes that the fringing capacitance actually occurs at the open end of the transmission line, and strictly speaking, it can be said that "perfect open". This is because such cases are included because they are not available. According to the non-reciprocal circuit device of the present invention, a transmission line having a line length of (2n + 1) /4.lambda.g is used for a broadband circuit, and the other end of the transmission line is open or high impedance. I. L. Broadening of the isolation characteristic can be achieved while avoiding influence on the characteristic.
In addition, for example, by employing a substrate on which a stripline line is formed, the entire components can be reduced in size as compared with the case where a circuit is formed using the above-mentioned three-dimensionally shaped coil and capacitor. Further, in the present invention, since it is only necessary to manage the line length of the transmission line, it is possible to configure a high-precision wide-band circuit having less variation than the conventional case where L and C 'are formed with lumped constants. it can. Along with this, it is possible to simplify the electrical adjustment or eliminate the need for adjustment, thereby reducing the cost and responding to the cost reduction of parts. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a non-reciprocal circuit device according to an embodiment of the present invention. In this embodiment, a case where the present invention is applied to an isolator will be described as an example. In the isolator 10 of this embodiment, three center conductors 2 to 4 are arranged so as to be electrically insulated from each other and to intersect at an angle of 120 degrees.
One main surface of the ferrite 5 is brought into contact with the intersection of the ferrite 5 and a DC magnetic field Hex for bias is provided by a permanent magnet not shown.
Is applied, and the basic configuration is the same as the conventional one. The ferrite 5, the center conductors 2 to 4, and the like are accommodated in a magnetic yoke constituting a magnetic closed circuit (not shown). One end 2a-4a of each of the center conductors 2-4 is connected to ground, and the other end 2b-4b is connected to input / output ports P1-P3.
Matching capacitors C1 to C3 are connected in parallel to P3.
The one port P3 is connected to a non-reflection terminating resistor R, which transmits a signal from the input / output port P1 to the port P2, and transmits a reflected wave entering from the port 2 to the terminating resistor R. It is designed to absorb. The terminating resistor R is connected in series with a broadband circuit 11 which is a feature of the present embodiment. The broadband circuit 11 is configured by using a transmission line (transmission line TL) having a line length of (2n + 1) / 4 · λg. Note that n is an integer,
λg is the wavelength in the transmission line. One end of the transmission line is connected to the terminating resistor R, and the other end is open or has high impedance. As the transmission line, specifically, a coaxial line, a microstrip line, a triplate strip line, a coplanar line, a suspended strip line, a waveguide, an NRD guide, or the like is employed. Next, the operation and effect of this embodiment will be described. According to the isolator 10 of the present embodiment, since the transmission line having the line length of (2n + 1) / 4 · λg is used for the broadband circuit 11, I.I. L. It is possible to widen the isolation characteristic while avoiding the influence on the characteristic, thereby solving the problem that the reflected wave from the port P2 passes through the port P1, and further prevent the generation of noise due to intermodulation distortion. . The transmission line can be realized by employing a substrate on which a strip line line or the like is formed.
Compared with the conventional coil and disk type capacitors, the whole components can be reduced in size and weight. Further, in this embodiment, since it is only necessary to set the line length of the transmission line to the above-mentioned length, a high-precision wide-band circuit having less variation compared to the conventional case where L and C 'are formed with lumped constants. Can be configured. As a result, the electrical adjustment can be simplified or no adjustment can be made, so that the cost can be reduced and the cost of parts can be reduced. In the above embodiment, an isolator in which a terminating resistor is connected to a lumped-constant 3-port circulator has been described as an example. However, the present invention is not limited to this. Of course, the present invention can also be applied to a non-reciprocal circuit device of the type. For example, FIG. 5 shows an example of application to a distributed constant type isolator using a microstrip line. In the figure, 21 is a magnet, 22 is a ferrite substrate, 26 is a ground plate and fixed flange, 23 is a strip center conductor,
23a to 23c are input / output terminals, and one terminal 23c
Is connected to a resistor terminator 24. A transmission line 25 as a broadband circuit is connected to the resistance terminator 24. This is constituted by a microstrip line having a line length of (2n + 1) / 4 · λg. The shape of the bent portion of the microstrip line is shown in FIG.
The corners are removed as shown by a in FIG.
It can be bent into a shape or bent as shown by c. When the line is open, the side electrode 25a is removed. In addition, the above terminator 2
4 may be provided at the cold end (ground side) as shown in FIG. FIG. 6 shows a case where the present invention is applied to a waveguide isolator. In the figure, 31 is a waveguide isolator, 32 is a magnetic circuit, 33 is a magnet, and 34 is ferrite. A waveguide line 35 functioning as a broadband circuit is connected to a port on the front side of the figure, and a terminator 36 having a resistive film 36a is connected to the end of the waveguide line 35. The line length of the waveguide is set to (2n + 1) / 4 · λg. As described above, according to the nonreciprocal circuit device according to the present invention, the line length is (2n + 1) / 4 · λ in the terminal resistance.
g, one end of the transmission line was connected to a terminator, and the other end was open or high impedance. L. There is an effect that the isolation can be broadened without deteriorating the characteristics, the size can be reduced, and the cost can be reduced by eliminating the need for adjusting the electrical characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an equivalent circuit diagram for explaining an isolator according to one embodiment of the present invention. FIG. 2 is a value circuit diagram for explaining a process of establishing the present invention. FIG. 3 is an equivalent circuit diagram of a conventional isolator. FIG. L. FIG. 3 is a diagram illustrating characteristics and isolation characteristics. FIG. 5 is a schematic diagram showing an embodiment of a distributed constant type isolator using a microstrip line. FIG. 6 is a schematic view showing an example of a waveguide type isolator. [Description of Signs] 2-4 Central conductor 5 Ferrite 10 Isolator (non-reciprocal circuit element) 11 Broadband circuit (transmission line) R Terminating resistor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Jikken Sho 49-17160 (JP, Y1) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01P 1/36 H01P 1/26

Claims (1)

(57) [Claim 1] In a non-reciprocal circuit device having a terminator connected to any one port of a three-port circulator, the terminator has a line length of (2n + 1) /4.multidot. λg (n is an integer, λg is a wavelength in the transmission line) is provided,
A nonreciprocal circuit device, wherein one end of the transmission line is connected to the terminator, and the other end is open or has high impedance.