JPH0411381Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a high frequency limiter circuit that greatly changes impedance to increase reflection during high power.

FIG. 1 shows a conventional waveguide coaxial conversion type high frequency limiter circuit. In this circuit, a coaxial cavity 2 is formed parallel to the E (electric field) plane of the TE ₁₀ mode of the rectangular waveguide 1, a center conductor 3 is placed inside the coaxial cavity 2, and a pill-shaped package is formed. The pin diode 4 is used as a limiter, and its center conductor 3
The coaxial length is adjusted by the double screw 5, and the diode 4 is loaded by the screws 5 and 6.
The impedance between the coaxial section and the waveguide system was adjusted by adjusting the position of the waveguide.

However, in this structure, since it is necessary to move the diode 4 during adjustment, the electrical contact between the diode 4 and the center conductor 3 or the screw 6 becomes unstable, which makes adjustment particularly difficult during high power operation. Sometimes, when impedance matching occurs, the power is dissipated in the diode 4, and there is a risk that the diode 4 will be destroyed.

Therefore, the insertion loss associated with the insertion of a coaxial circuit during low power operation is adjusted, and the isolation (the difference between the insertion loss during low power operation and the insertion loss during high power operation) is adjusted during high power operation.
If the isolation did not reach the specified value, the process was repeated, starting with the insertion loss adjustment during low power operation.

For this reason, there is a drawback that not only is it time consuming to make adjustments, but it is also difficult to make fine adjustments to obtain the best characteristics.

Figure 2 shows another conventional example of a waveguide coaxial conversion type high frequency limiter circuit, in which a screw 7 is attached, which corrects the reflected wave from the coaxial section. , which was intended to reduce insertion loss, and did not have the effect of increasing the isolation value.

The present invention was developed in view of the above, and its purpose is to make it possible to adjust the distribution of the high-frequency electric field near the diode, and to adjust the impedance to optimize the operating condition without the risk of destroying the diode. An object of the present invention is to provide a high frequency limiter circuit that can be easily realized.

Examples of the present invention will be described below. Third
The figure shows one embodiment, and the same components as in FIG. 1 are given the same reference numerals.
In addition, this waveguide 1 has a height H = 10.5 mm and a width W = 23 mm.
mm, and is a waveguide for the X band (8.4 to 12.4 GHz). In this example, a screw 8 made of a metal conductor is inserted from a direction perpendicular to the axial direction of the center conductor 3, and a tip 8a of the screw 8 protrudes near the diode 4. Therefore, the high frequency electric field distribution near the diode 4 can be changed by the screw 8. 9 is a screw.

Impedance adjustment is done by connecting the center conductor 3 and screw 9 to minimize insertion loss during low power operation.
to determine the coaxial length, then adjust screw 8 to obtain the specified isolation value under high power operation.

Figure 4 shows changes in insertion loss and isolation value with respect to the number of rotations of the screw 8 (changes in insertion length of the screw 8).As the screw 8 rotates from 0 to 2.5 rotations, the isolation decreases by -15 The insertion loss changes by -19dB, but the insertion loss remains at -0.45 to -0.65dB.

Next, the function and effect of the screw 8 will be explained with reference to FIGS. 5 and 6. Figure 5 shows low power (10mW
Fig. 3 shows an equivalent circuit of the high frequency limiter circuit during operation, and Fig. 6 shows an equivalent circuit when diode 4 is conducting during high power (1KW or more) operation. In these figures, Lx is the equivalent inductance of the center conductor 3, Lp and Cp are the inductance and capacitance of the diode 4 package, Rj and Cj are the junction resistance and junction capacitance of the diode 4, and Cx is the parasitic capacitance added by the screw 8. be. The equivalent circuit of only diode 4 is shown surrounded by a broken line.

The equivalent impedance Za of these equivalent circuits is
When Zb is calculated, the following equations (1) and (2) are obtained. Note that the spreading resistance and junction resistance Rj of diode 4 (≪
1/ωCj) is omitted for simplicity. First, from Figure 5, Za={1−ω ² LpCj−ω ² Lx [Cj+(Cp+Cx)
(1−ω ² LpCj)]}/{jω[Cj+(Cp+Cx)(1
−ω ² LpCj)]} …(1) From Figure 6, Zb=jω{Lp+Lx[1−ω ² Lp(Cp+Cx)]}/
[1−ω ² Lp (Cp + Cx)] …(2) Calculating the parallel resonance angular frequency ωa from equation (1) and the series resonance angular frequency ωb from equation (2), ωa ² = 1/[Lp (Cp + Cx)] +1/(LpCj)
…(3) ωb ² = 1/[Lp(Cp+Cx)]+1/[Lx(Cp+
Cx)] …(4) The parallel resonant angular frequency ωa during low power operation obtained from equation (3) is equal to the series resonant angular frequency ωb during high power operation obtained from equation (4). By changing the insertion length of screw 8, the parasitic capacitance Cx
can change.

From equations (3) and (4), the change in the resonant angular frequency due to a change in the parasitic capacitance Cx has the following relationship: (Δωa/ωa) < (Δωb/ωb) (5), and the change in the parallel resonant angular frequency ωa In contrast, the series resonance angular frequency ωb can be greatly changed.

Therefore, the isolation can be greatly changed as shown in FIG.

FIG. 7 shows another embodiment of a waveguide coaxial conversion type high frequency limiter circuit in which a screw 8 is inserted from a direction parallel to the axial direction of the center conductor 3. In addition, FIG. 8 shows the screw 8 from the direction perpendicular to the axial direction of the center conductor 3
10 is a coaxial line, and 1 is a coaxial line.
1 is a double screw, and 12 is a screw forming a part of the center conductor.

In the above embodiment, the impedance was adjusted by inserting a metal conductor screw 8 to change the electric field component near the diode 4, but instead of this screw 8, a dielectric piece with a high relative permittivity Similar effects can be obtained by using .

As described above, the present invention provides a high frequency limiter circuit in which a part of the center conductor in a coaxial cavity provided in a direction perpendicular to the propagation direction of a high frequency propagation line is replaced with a diode. It consists of a conductor or a dielectric material with a high relative permittivity located near the diode.

This allows high frequency power propagating through waveguides and coaxial lines to be effectively coupled to the diode, making it easy to adjust the impedance to obtain the best operating conditions, and for low power operation. Isolation can be adjusted under high power operation without increasing insertion loss.
This method is characterized in that variations in characteristics of diodes in the same production lot can be smoothed and utilized in circuits, and the yield of diodes can be improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional waveguide coaxial conversion type high frequency limiter circuit, Fig. 2 is a sectional view of another conventional waveguide coaxial conversion type high frequency limiter circuit, and Fig. 3 is a cross sectional view of a conventional waveguide coaxial conversion type high frequency limiter circuit. A cross-sectional view of the waveguide coaxial conversion type high-frequency limiter circuit of the example, FIG. 4 is a characteristic diagram of insertion loss and isolation of the circuit shown in FIG. 3, and FIG.・Equivalent circuit diagram of the diode mount part during power operation, Figure 6 shows the diode mount part during high power operation of the circuit in Figure 3.
An equivalent circuit diagram of the mount part, FIG. 7 is a sectional view of a waveguide coaxial conversion type high frequency limiter circuit of another embodiment, and FIG. 8 is a coaxial to coaxial conversion type high frequency limiter circuit of yet another embodiment. FIG. 1...Waveguide, 2...Coaxial cavity, 3...Center conductor, 4...Pill-shaped package pin diode, 5...Double screw, 6-9...Screw, 10...
Coaxial line, 11...double screw, 12...screw.

Claims (1)

[Scope of Claim for Utility Model Registration] In a high frequency limiter circuit in which a part of the center conductor in a coaxial cavity provided in a direction perpendicular to the propagation direction of a high frequency propagation line is replaced with a diode, substantially the above diode in the coaxial cavity is replaced with a diode. A high frequency limiter circuit characterized in that a conductor or a dielectric material having a high relative permittivity protrudes from a hollow portion.