JPS6058605B2 - π type resistor attenuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of the Invention The present invention relates to a π-type resistive attenuator that reduces mismatch attenuation even in the UHF band.

(b) Prior Art An example of a conventional circuit is shown in FIG.

In FIG. 1, 1 is an input terminal, 2 is an output terminal, and 3 and 4 are ground terminals. R, ~R. is a resistance constituting a π type, and R
, and R. is the input side parallel resistance, R. is the series resistance, and R is the output side parallel resistance. The resistors R, , R2 are connected in parallel to share the power when the input power is large. For use in the UHF band, for example, a series resistor R3 is arranged coaxially with the center conductor 5 to match impedance.

When the impedance is 50Ω and the attenuation is 20dB,
R,■200Ω,R0=82Ω,Ra■360Ω,R
. ■ Set it to 56Ω. In the conventional circuit shown in FIG. 1, as the input frequency increases, the amount of mismatch attenuation increases due to the inductance and stray capacitance of the lead wires. Before adjustment, when it reaches around 100MH2, VSWR becomes 1.
It is often 6 or more. (c) Problems with the conventional technology In order to lower the VSWR of the conventional circuit shown in Figure 1 to 1.41■), connect a small capacitor in parallel with the resistor to compensate for lead wire inductance and stray capacitance. or adjust the resistance by moving the resistor closer to ground.

Since each element has variations, these adjustments must be made individually. For this reason, there are problems in that test and adjustment work takes time and it is difficult to obtain an attenuator with uniform performance. (d) Purpose of the Invention This invention divides the input side parallel resistance into a plurality of resistances, and inserts a ferrite toroidal core in the center conductor connecting the parallel resistances, thereby reducing mismatch attenuation and achieving uniform performance. The present invention provides a π-type resistance attenuator.

(e) Examples of the invention First, a circuit diagram of an embodiment according to the present invention is shown in FIG.

1-5 and R3, R.

is the same as in Figure 1. Resistance R,, ~R,. is the first
The resistances R, , R in the figure. is further divided, and if the attenuation is 2.0 dB in a 50 Ω system, R1l■220 Ω, R,
2■220Ω, R, 3■220Ω, R, O■270Ω, etc. Compared to the case of Fig. 1, this means that the resistance R,...
~R, , can be used for low power, and the center conductor 5
The resistance to R, , ~R,. This is to increase the number of connection points.
For example, in FIG. 1, the resistors R, , R.

When is for 2W, the resistors A, ~R, in Figure 2. is for IW and can apply the same power as in Figure 1. Second
L1 to L5 in the figure are ferrite toroidal cores, and a series resistor R is connected to input terminal 1.

Insert into the center conductor 5 up to. As shown in Figure 2, the insertion position is between input terminal 1 and the input terminal. between each connection point between. VSWR is improved as the number of cores L1 to L5 is increased from the input terminal 1 side. Next, FIG. 5 shows an example of data measured by the embodiment circuit of FIG. 2. The horizontal axis in FIG. 3 is the frequency, and the vertical axis is the standing wave ratio ■SWR. Curve A in Figure 3 is the core L1~! in Figure 2! This is the data when the SWR is 1.6J:). It's on top.

On the other hand, curve B in FIG. 3 corresponds to cores L1 to L5 in FIG.
This is the data when inserting the VSWR, and the VSWR has been improved to approximately 1.1. In this case, FIG. 1 does not make the necessary adjustments. This is the second frequency band in Figure 3.
The core of the figure! This is thought to be because the loss increases, radiation from the center conductor 5 is suppressed, and interference between the center conductor 5 and other parts is reduced. Incidentally, the measured example of the amount of attenuation shown in FIG. 2 is 21 dB to 21.5 dB in the range of 900 to 1200 MHz, and the amount of attenuation increases slightly as the frequency increases.

Also, the number of 5 on core L may be increased or decreased depending on the required VSWR value. Reduce from the side. (f) Effects of the Invention According to the present invention, a resistance attenuator with substantially uniform natural performance can be obtained without any adjustment, and the time for testing and adjustment can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conventional circuit, FIG. 2 is a circuit diagram of an embodiment according to the present invention, and FIG. 3 is a diagram showing an example of measurement data by the embodiment circuit of FIG. 1...Input terminal, 2...Output terminal, 3
...Grounding terminal, 4...Grounding terminal, 5.
...Center conductor, R1 to R4...Pi type resistance, Rll to Rl4...Input side parallel resistance! ~L
5... Ferrite toroidal core.

Claims (1)

[Claims] 1. A π-type resistance attenuator characterized by dividing the input side parallel resistance into a plurality of resistances and inserting a ferrite toroidal core in the center conductor connecting the parallel resistances.