JPH0453441B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is a switched line type transfer method in which two lines with different line lengths are switched using a switch or the like to achieve a desired phase difference in the microwave band. This is related to improving the performance of phase equipment.

[Conventional technology]

FIG. 4 is a perspective view showing a conventional switched line type phase shifter, as shown in SSD84-119 of the Semiconductor/Transistor Study Group of the Institute of Electronics and Communication Engineers, for example. In the above-mentioned literature, it is a monolithic MIC using a gallium arsenide substrate, and the switching element is
FET is used, but in Figure 4 a hybrid
It is explained as a diode phase shifter for MIC.
Figure 4 shows the configuration of a microstrip. 1 is a dielectric substrate, 2 is the ground conductor of the microstrip, 3 is a microwave input/output line, and 4 is one of the two microwave paths. Reference side line, 5 is a delay side line of another route, and 6a is a switching element for switching on/off of the reference side line.
PIN diode 6b is a PIN diode that is a switching element that switches the delay side line on and off, and 7 is a gold ribbon that connects the PIN diode and the line.

Note that a bias circuit is actually included to apply a DC bias to the PIN diode, but it will be omitted here.

Next, the operation will be explained. A switched line phase shifter works as a phase shifter by switching between two phase states: a reference phase state and a delayed phase state. First, in the standard phase state, two
A DC bias is applied to the PIN diode 6a so that a current flows in the forward direction, and the diode 6a is turned on. Further, voltages are applied in opposite directions to the two PIN diodes 6b, and the PIN diodes 6b are turned off. Therefore, the microwave that has entered one input/output line 3 does not flow to the PIN diode 6b that is in the off state, but flows toward the PIN diode 6a that is in the on state, passes through the reference side line 4, and is transferred to the other input/output line. Exit to track 3. Next, in the delayed phase state, the order of the PIN diode 6a and the PIN diode 6b is reversed, and the microwave passes through the delayed line 5.

[Problem that the invention seeks to solve]

As described above, the conventional switched line phase shifter uses the difference in the physical length of the line to create a phase shifter, so it can obtain a phase shift with high precision at the center frequency f ₀ , but when the band is wide However, there was a problem in that the error in the amount of phase shift becomes large in areas far from the center frequency f ₀ . FIG. 5 shows the phase shift amount characteristics of a 180 degree bit phase shifter with a conventional configuration. Center frequency f ₀ ±
This shows that an error of ±18 degrees occurs at 10%.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a switched line type phase shifter that can reduce phase shift amount errors in a wide band.

[Means for solving problems]

The switched line phase shifter according to the present invention includes:
An open-ended stub with an electrical length of approximately 1/2 wavelength of the center frequency is added in parallel to a part of the reference side line.

[Effect]

The open-ended stub of about 1/2 wavelength at the center frequency in this invention has a parallel admittance of 0 at the center frequency when viewed from the point where it is added in parallel, and is equivalent to the case where there is no stub in terms of microwaves. However, at frequencies higher than the center frequency, the electrical length of the stub becomes longer than one-half wavelength, and the parallel admittance becomes capacitive. Therefore, the transmission phase is delayed compared to the case without the stub. Further, at a frequency lower than the center frequency, the electrical length of the stub becomes shorter than a half wavelength, and the parallel admittance becomes inductive. Therefore, conversely, the transmission phase advances compared to the case without the stub. By adding a stub having such characteristics to the reference side line, the frequency characteristics of the reference side line become steep and approach the frequency characteristics of the lagging side line. This improves the frequency characteristics of the phase shift amount, which is the phase difference between the reference side line and the delayed side line.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 8 is an open stub added in parallel to the reference side line. In this example, two open stubs are added in parallel to a part of the reference side line, and the electrical length of the stub is approximately half the center frequency.
It has become a wavelength.

Further, the interval between the two open stubs is about 1/4 wavelength of the center frequency. The other configurations are the same as the prior art example shown in FIG.

Next, the operation will be explained. Microwaves input from the input/output line 3 are activated by switching the order and reverse bias of the PIN diode 6a that controls the connection with the reference side line 4 and the PIN diode 6b that controls the connection with the lagging side line 5. Passing through one of the routes is the same as the case described in FIG. 4. First, PIN diode 6b is in the on state, PIN
When the diode 6a is in the off state, the microwave entering from one input/output line 3 passes through the delay side line 5 and goes out to the other input/output line 3. The transmission phase in this case has a frequency characteristic corresponding to the physical length of the delay side line 5. Next, when the PIN diode 6a is on and the PIN diode 6b is off, the microwave entering from one input/output line 3 passes through the reference side line 4 and exits to the other input/output line 3. Since the open stub 8 of approximately 1/2 wavelength at the center frequency is added to the reference side line 4, the transmission phase is the same as when there is no stub at the center frequency, but the open stubs 8 are parallel at frequencies other than the center frequency. It acts as an admittance and influences the transmission phase of the reference side line 4. For example, when the frequency is high, the parallel admittance of the open stub 8 becomes capacitive, and the transmission phase of the reference line 4 is delayed compared to when there is no stub. Further, when the frequency is low, the parallel admittance of the open stub 8 becomes inductive, and the transmission phase of the reference side line 4 advances compared to the case without the stub. Therefore, the frequency characteristic of the transmission phase of the reference side line 4 becomes steep, approaching the frequency characteristic of the transmission phase of the delayed side line 5, and the frequency characteristic of the phase shift amount becomes good. Since the degree to which the frequency characteristic becomes steep depends on the line impedance of the open stub 8, by selecting an appropriate line impedance, it is possible to make the error due to the frequency characteristic of the amount of phase shift close to zero. Figure 2 shows how the frequency characteristics of the phase shift amount of the 180 degree bit phase shifter change depending on the line impedance Z of the open stub 8 when the characteristic impedance z ₀ of the phase shifter is 50Ω. It is a graph. This shows that the characteristics are significantly improved compared to FIG. 5, which shows the characteristics of the conventional configuration. In this embodiment, two open stubs 8 are added, which not only increases the effect of steepening the frequency characteristics of the transmission phase, but also cancels out the parallel admittance and improves the reflection characteristics of the phase shifter. There is.

In the above embodiment, two open stubs 8 are used, but even one open stub 8 only halves the effect of steepening the frequency characteristic of the transmission phase, and has the effect of reducing the phase shift amount error of the phase shifter. There is no difference. In addition, since an open-ended stub with approximately 1/2 wavelength at the center frequency is added, the reflection of this open stub 8 does not appear at the center frequency, and even in the 20% band range shown in Figure 2, the phase shifter is The effect of the present invention can be obtained without causing a large reflection that affects the characteristics. Furthermore, it goes without saying that the effects of the present invention can be obtained even when there are three or more open stubs. Further, the electrical length of the stub is not limited to a half wavelength, but may be an integral multiple of that wavelength. Furthermore, the PIN diodes 6a and 6b are installed in series at the branch, but as in the embodiment shown in FIG. 6a and 6b may be attached to switch the microwave path. In the figure, numeral 9 is a pad for grounding one side electrode of the PIN diodes 6a and 6b installed in parallel to the line. moreover,
The method of mounting the PIN diodes 6a and 6b in series and the method of mounting them in parallel may be used together.
The switching element is not limited to a PIN diode, and for example, an FET may be used. Further, although the line type has been explained using a microstrip line, other types such as a triplate line or a coaxial line can also be used. Furthermore, it is also applicable to a monolithic MIC configuration using a semiconductor substrate such as gallium arsenide.

〔Effect of the invention〕

As described above, according to the present invention, since the open stub of approximately 1/2 wavelength at the center frequency is added in parallel to the reference side line of the switched line phase shifter, the phase shift amount of the phase shifter is This has the effect of significantly improving the frequency characteristics and reducing phase shift errors over a wide band.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a switched line phase shifter according to an embodiment of the present invention, FIG. 2 is a graph showing frequency characteristics of phase shift amount according to the embodiment of FIG.
FIG. 3 is a perspective view showing a switched line phase shifter according to another embodiment of the present invention, FIG. 4 is a perspective view showing a conventional switched line phase shifter, and FIG. 5 is a perspective view showing a conventional switched line phase shifter shown in FIG. FIG. 6 is a diagram showing frequency characteristics of phase shift amount depending on the configuration. In the figure, 1 is a dielectric substrate, 2 is a ground conductor, 3 is an input/output line, 4 is a reference side line, 5 is a delay side line, 6a, 6b are PIN diodes, 7 is a gold ribbon, 8 is an open stub, 9 is the ground pad.
It should be noted that the same or corresponding parts in the figures are indicated by the same reference numerals.

Claims (1)

[Claims] 1 A switched line type shifter that works as a phase shifter by alternately switching the path through which microwaves pass between the first path and the second path and utilizing the difference in transmission phase between the first path and the second path. In a phase converter, a line with an electrical length of about half the wavelength of the center frequency or an integral multiple thereof is added in parallel to the first path or a part of the second path, with the tip open for microwave radiation. A switched line phase shifter characterized by: