JPS6069905A - Strip line attenuating circuit - Google Patents

Abstract

PURPOSE:To obtain an attenuation circuit having a frequency of a transmitted phase opposite to that of a conventional pi attenuation circuit by making the impedance resistive at the center frequency, making it capacitive at a lower frequency and making it inductive at higher frequencies. CONSTITUTION:A strip line 5 having a length being integral number of times of 1/2 wavelength whose tip is short-circuited is connected in series with the tip of a resistor 2 having a normalized resistance value RB(RB>1) so as to constitute the circuit. In checking the input impedance of the line 5 viewed from between contacts 3 and 4 next, the impedance ZB of the branch is expressed as ZB=RB(RB>1) and the same characteristic as that of a conventional pi attenuation circuit is obtained. The input impedance of the line 5 is a capacitive impedance and the branch impedance ZB is expressed in equation I . The input impedance at a frequency higher than the center frequency is the inductive reactance and the branch impedance ZB is expressed in equation II.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a π-type attenuation circuit composed of a stripline, and particularly to a stripline attenuation circuit having a function of compensating for phase changes with frequency.

A conventional π-type attenuation circuit of this type has a configuration as shown in Fig. 1. In the figure, ■ is a strip line.

2 is a resistor having a normalized resistance value I (Rn)l).

Line 1 is Rx = Rn / ItB2 due to matching conditions.
17 with a resistance value of ...
The line is four wavelengths long.

The transmission loss characteristics with respect to frequency between the connection points 3 and 4 of this circuit are shown in FIG. 2, and the transmission phase characteristics are shown in FIG. 3. As can be seen from FIG. 3, the amount of transmission phase increases as the frequency increases. It is known that even in a passive strip line including a two-attenuator splitting coupler, the amount of transmission phase generally increases with frequency.

Therefore, 1 the present invention is a circuit having a frequency characteristic of the amount of transmission phase opposite to that of the conventional π-type attenuation circuit etc. described above, that is, 9 the phase characteristic of the entire circuit is set so that the amount of transmission phase decreases as the frequency increases. It is an object of the present invention to provide an attenuation circuit that can compensate for phase changes with frequency so that the phase change remains constant regardless of the frequency.

The present invention will be explained below based on the drawings.

FIG. 4 shows an attenuation circuit showing one embodiment of the present invention.

Components that are the same as those in FIG. 1 are designated by the same reference numerals. Fourth
In the figure, a strip line 5 with a length that is an integer multiple of 172 wavelengths with the tip short-circuited (an odd number multiple of 1/4 wavelength with the tip open) is connected to the tip of a resistor 2 having a normalized resistance value RB (RB>1). The present invention is characterized in that the circuit is constructed by connecting the lengths of the wires in series. Note that the characteristic impedance of the line 5 is arbitrary. For example, the resistance value R of resistor 2
If B is 20, the characteristic impedance of the line 1 is Rx = 1.15 (Ql) from the above equation (1), and the line 5 has a characteristic resistance 1 (length that is an integer multiple of 72 wavelengths of Ql) with its tip short-circuited. It is fine to use.

Next, it was viewed from between connection points 3 and 4. 1/ with the tip shorted
Considering the line 50 input impedance that is an integer multiple of two wavelengths, at the center frequency.

The impedance zB of the branch is z, = RB (RB>1)...
・・・・・・・・・・・・・・・・・・・・・・・・(2
), and has the same characteristics as the conventional π-type attenuation circuit.

At frequencies lower than the center frequency, the input impedance of the line 50 is a capacitive reactance, and the branch impedance zB is Zn=RBjX+ (X+>O)
・・・・・・・・・・・・・・・・・・(3) Also at frequencies higher than the center frequency.

The input impedance is an inductive reactance, and the branch impedance zB is ZB =Rs +j
Xz (X2 > 0)・・・・・・・・・・・・・・・
......(4).

Next, Figure 5 shows the transmission loss characteristics of this circuit.

The transmission phase characteristics are shown in Figure 6. In both figures, n indicates that the line 5 is n times the 1/2 wavelength. Fifth
As is clear from the figure and FIG.

When n=o, the transmission characteristics become equal to those of a conventional π-type attenuation circuit (see FIGS. 2 and 3). Also, resistance value RB = 2
(In the case of Ql, it can be seen from Fig. 6 that it has a phase characteristic opposite to that of the conventional π-type attenuation circuit when n>2.The slope of the phase characteristic shown in Fig. 6 changes the characteristic impedance of the line 5. It is also possible to control the

The attenuation circuit of the present invention having the configuration described above has a frequency characteristic with a transmission phase amount opposite to that of a conventional π-type attenuation circuit, so it is possible to avoid two frequency changes in an antenna feeding circuit using the attenuation circuit. In addition to being useful for phase compensation of the aperture distribution, it can also be used as a phase compensation circuit based on the frequency of a circuit that takes one phase into consideration.

[Brief explanation of drawings]

Figure 1 is a diagram of a conventional π-type attenuation circuit, Figure 2 is a transmission loss characteristic diagram of the circuit shown in Figure 1, Figure 3 is a transmission phase characteristic diagram of the circuit shown in Figure 1, and Figure 4. 5 is a circuit diagram showing one embodiment of the strip line attenuation circuit according to the present invention, and FIG.
FIG. 6 is a transmission loss characteristic diagram of the circuit shown in the figure, and FIG. 6 is a transmission phase characteristic diagram of the circuit shown in FIG. ■...Line with a length of 1 wavelength, 2...Resistance, 3, 4...
・Connection point, 5... A line with a length that is an integral multiple of 1/2 wavelength. Patent applicant: Japan Radio Co., Ltd. Ryo 1 Figure 2 Figure Vf.

Claims (1)

[Claims] In a π-type strip line attenuation circuit in which resistors are added in parallel to both ends of a 1/4 wavelength line length, a strip line is connected in series to each of the two resistors, and the The input impedance of the line is the resistance at the center frequency. A strip line attenuation circuit that is capacitive at frequencies lower than the center frequency and inductive at frequencies higher than the center frequency, so that the amount of transmission phase decreases as the frequency increases.