JPH0453301A - Delay line and microwave phase shifter - Google Patents

Abstract

PURPOSE:To obtain a large delay with a small sized line by arranging striplike conductor on a strip conductor via a dielectric body. CONSTITUTION:A microstrip line is made up of a semiconductor GaAs substrate 11, a strip conductor 12 and a ground conductor 13 to form a delay line, a striplike conductor 15 is arranged opposite to the microstrip line with a dielectric body 14 inbetween periodically in a direction intersecting the microstrip line. Then a FET 18 having a gate width periodically along the strip conductor 12 is formed on an operating layer 31 on the GaAs substrate 11. The FET 18 uses the strip conductor 12 as one of a source and a drain electrode 19 and the other of a drain and a source electrode 20 is connected to the ground conductor 13 through a throughhole 22. Thus, a large delay is obtained regardless of a small sized line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a delay line and a microwave phase shifter used in an electronic scanning antenna or the like to control the phase of a signal.

(Prior art) As a circuit for controlling the phase of a microwave signal, two transmission lines with different electrical lengths are switched using a switch made of semiconductor elements, and a desired phase amount is determined from the phase difference of the signals transmitted through the transmission lines. Line-switching phase shifters are widely used.

An embodiment of this line switching type phase shifter is shown in FIG. Here, a switch constituted by a switching semiconductor element is connected to the input/output terminals 1a and lb. The operation of this switch switches between the reference side transmission line 4 and the delay side transmission line 5 whose passing phase amount is larger by a desired phase shift amount. Here -
As an example, FETs 2a to 2d connected in series and in parallel,
3a to 3d constitute a switch. FE here
Apply OV to the gate electrodes of T2a, 2d, 3a, and 3d, and apply -5V to the gate electrodes of FET2b, 2c, 3b, and 3c.
When this is applied, the two switches enter a state in which signals are transmitted to the reference side transmission line 4 side, and a state in which the path connected to the delay side transmission line 5 is cut off. Therefore, the microwave signal inputted through the input/output terminal 1a is outputted to 1b with a phase delay corresponding to the amount of phase shift of the reference side transmission line 4. If the input is from 1b, it is output from 1a in the same way.

Further, when a bias voltage is applied to the gate electrode of each FET so as to have a relationship opposite to the above, the input microwave signal is output with a phase delay corresponding to the phase shift amount of the delay side transmission line 5. Therefore, by switching the gate bias voltages of FETs 2a to 2d and 3a to 3d as described above,
A phase shift amount corresponding to the phase difference between the reference side transmission line 4 and the delay side transmission line 5 is obtained. As shown in FIG. 5, this amount of phase shift varies linearly with frequency. Therefore, this phase shifter becomes an equal delay type shifter in which the delay time is constant over a wide frequency band.

However, when obtaining a large phase shift amount of 180° or more with this line switching type phase shifter, there are the following drawbacks.

■The delay side transmission line becomes longer and the shape of the phase shifter becomes larger.

■When a signal passes through the reference transmission line 4, resonance occurs at a frequency where the length of the delay transmission line 5 becomes 1/2 wavelength, resulting in deterioration of the transmission loss and deterioration of the linearity of the transmission phase. .

(Problems to be Solved by the Invention) As described above, in conventional line-switching microwave phase shifters, when trying to obtain a large amount of phase shift, the shape of the delay-side transmission line becomes large, and the frequency characteristics It has disadvantages such as resonance.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the above-mentioned drawbacks, and provides a delay line capable of obtaining a large amount of delay with a small size, and a line switching type microwave phase shifter using this delay line. The purpose is to

[Structure of the invention] (Means for solving the problem) In order to achieve the above object, the present invention uses a semi-insulating Ga
A microstrip line is formed on an As substrate to constitute a delay line. Strip-shaped conductors are arranged opposite to this microstrip line conductor with a dielectric layer interposed therebetween and periodically in a direction crossing the microstrip line conductor.

The strip-shaped conductors are connected by a connecting conductor and connected to a ground conductor by a through hole. Then, FETs having a gate width of a certain length are periodically formed along the strip conductor in the active layer on the semi-insulating GaAs substrate.

In this FET, the strip conductor is used as either a source or a train electrode, and the other drain or source electrode is connected to a ground conductor through a through hole.

A microwave phase shifter is formed by switching the delay-side transmission line configured with this structure with a switch provided on the input/output side.

(Function) In the line switching type microwave phase shifter of the present invention, when the delay side transmission line is put into the passing state by the switch, about -5V is applied to the gate I electrode of the FET connected to the strip conductor of the delay side transmission line. Apply a negative voltage of In this state, the section where the strip conductor is above the strip conductor becomes a section of low impedance due to the capacitance between the strip conductor and the strip conductor. In addition, a section where there is no strip-shaped conductor above the strip conductor becomes a high-impedance section of only the microstrip line because the strip-shaped conductor has no capacity.

At the boundary between the low impedance section and the high impedance section, the strip conductor is connected to the ground conductor by an OFF-state FET.

Therefore, the delay-side transmission line becomes a transmission line with a periodic structure of low impedance and high impedance, and a large amount of delay (passing phase amount) can be obtained.

Further, in the line switching type phase shifter constructed using this delay line, when the delay side transmission line is cut off by the switch, the gate electrode of the FET is set to O■. In this state, the FET can be regarded as a minute resistance, and the delay-side transmission line is grounded through a small resistance at short intervals, so resonance does not occur.

(Embodiment) An embodiment of the microwave phase shifter of the present invention is shown in FIG. 1 below. Here, the same components as in the conventional example shown in FIG. 4 are given common numbers. A detailed diagram of the delay-side transmission line 10 according to the present invention is shown in FIG.

In Figure 2, semi-insulating GaAs substrate 11. Strip conductor 12. The ground conductor 13 constitutes a microslip line. The active layer 21 is formed along both sides of the strip conductor 12, and slightly enters the lower part of the strip conductor 12 from both ends.

This strip conductor 12 is covered with a dielectric 14 made of SiO2 or the like. Further, on the dielectric material 14, strip-shaped conductors 1 are arranged periodically in the propagation direction of electromagnetic waves.
5 are arranged, and the strip-shaped conductors are connected to each other by a connecting conductor 16, and are connected to a ground conductor 13 at the bottom of the insulating GaAs substrate 1' by a through hole 17. FET
1.8, as shown in the enlarged view of part B in FIG. 2(b), one of the source electrode or the drain electrode, for example, the source electrode 19, is connected to the strip conductor 12, and the other source electrode or the other drain electrode, for example, the drain electrode 20, is connected to the strip conductor 12. is through hole 22
It is connected to the strip-shaped conductor 15 by. The delay-side transmission line has a large number of consecutive structures.

An equivalent circuit of this structure is shown in FIG. 3(a). Here, the section 1a where there is no strip conductor 15 above the strip conductor can be represented by a transmission line having a high characteristic impedance Za and a phase constant βa. On the other hand, in the section 1b where the strip conductor 15 is located above the strip conductor 12, there is a capacitance between the strip conductor and the strip conductor, so the characteristic impedance Z is low.
b1 It can be represented by a transmission line with a phase constant βb. Further, the boundary between the high characteristic impedance section and the low characteristic impedance section is grounded by the FET 18.

Therefore, when a negative voltage of about -5 V is applied to the gate electrode 21 of FET 1g and FET 18 is turned off, the third
This can be shown by the equivalent circuit shown in Figure (b). Here FET
Since the capacitance C81 when OFF is small and can be ignored, there is a high characteristic impedance section where there is no strip conductor 15 above the strip conductor, and a low characteristic impedance section where the strip conductor 15 is above the strip conductor. It has an interval or periodic structure.

As is generally well known, such a periodic structure becomes a slow wave circuit, and the slow wave factor σ of a line having this periodic structure is given by the following equation using Floquet's theorem.

σ2- (β/β0)2-[(βala-βbib)/
/3 o 1] 2+ (f ball +1/-rK) 2β
ala βblb/(βOl)2 Here, β〇 - phase constant of free space β - phase constant of periodic structure transmission line -Za/Zb, 1-1a+1b In the above equation, βala-βblb, Za-200Ω, Zb-20Ω
Then, a2-10X (βa/βo)X (Ia Φ
lb)2/(la+Ib)2, and a slow wave factor nearly three times that of a normal microstrip line can be obtained.

Therefore, FETs 2a to 2d constituting the switch in FIG.
, 3a to 3d are set so that the delay-side transmission line 10 is in a passing state, and the gate bias of the FET 18 connected to the delay-side transmission line 10 is biased to a negative voltage. Obtainable.

In addition, FET2a to 2 constituting the changeover switch in FIG.
d, the gate bias voltages of 3a to 3d are set so that the delay side transmission line 10 is cut off, and the delay side transmission line 1
When the gate bias voltage of the FET 18 connected to 0 is set to Ov, F ET ], 8 can be regarded as a minute resistance R8N. This can be expressed by the equivalent circuit shown in FIG. 3(C). In this state, the delay-side transmission line 10 is grounded by the minute resistance RON at short intervals, and therefore does not resonate.

The feature of the present invention is that the strip-shaped conductor is placed on the slip I/slip conductor via the dielectric, so the capacitance between the strip conductor and the strip-shaped conductor is high, and therefore the impedance zb of this part is low. Therefore, K=Za/Zb can be increased.

This makes it possible to obtain a high slow wave rate σ with a small area. Another advantage is that the FET is easy to manufacture.

The FET used in the present invention has a relatively small gate width and requires only a simple straight gate, so it is easy to manufacture.

In this embodiment, the active layer was not provided directly under the center of the strip conductor, but the active layer was provided in the range below the source or train electrode facing the strip conductor. However, the range of the active layer is not limited to this, and it may be provided on one metal surface area of the semi-insulating semiconductor substrate.

Further, in this embodiment, the FETs 18 are formed along both sides of the strip conductor, but the FETs may be formed only on one side instead of on both sides. Furthermore, they may be provided alternately on each side. In this embodiment, an example has been described in which the distance between adjacent strip-shaped conductors 15 is la and the width of the strip-shaped conductors 15 is Ib, but these dimensions are not limited to fixed values. In addition, the connecting conductor that connects the strip-shaped conductors 15 is
In this embodiment, both sides are used, but one side may be used.

[Effects of the Invention] According to the present invention, it is possible to realize a delay line that can obtain a large amount of phase shift with small dimensions, and a line switching type microwave phase shifter that can obtain a large amount of phase shift and does not generate resonance.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. FIG. 2 is a plan view and cross-sectional view showing the structure of a delay-side transmission line according to an embodiment of the present invention. FIG. 3 is a delay-side transmission line according to an embodiment of the present invention. An equivalent circuit diagram of the circuit, FIG. 4 is an example of a circuit configuration diagram of a conventional line switching type phase shifter, and FIG. 5 is a frequency characteristic diagram of the amount of phase shift of the conventional line switching type phase shifter. 1: semi-insulating GaAs substrate 12 strip conductor 13: ground conductor 14: dielectric 15: strip-shaped conductor 16: connection conductor 17: through hole 18: FET
1.9: Source or drain 20 Drain or source 21: Gate 22 Ni through hole 31: Operating layer

Claims (2)

[Claims] (1) A semi-insulating device including a microstrip line conductor formed on one surface of a semi-insulating semiconductor substrate, a ground conductor formed on the other surface of the semi-insulating semiconductor substrate, and the microstrip line conductor. a dielectric layer covering a surface of the semiconductor substrate; a strip-shaped conductor facing the microstrip line conductor with the dielectric layer sandwiched therebetween and periodically arranged in a direction transverse to the microstrip line conductor; a connecting conductor for connecting the conductors; a means for grounding the connecting conductor; an active layer formed in a predetermined area of the semi-insulating semiconductor substrate along the microstrip line conductor; a plurality of gates formed at predetermined intervals along the line conductor; and a plurality of gates formed in the active layer on the opposite side of the microstrip line conductor with the gates sandwiched therebetween, and connected to the ground conductor. A delay line characterized in that the plurality of electrodes serve as either a source or a drain, the microstrip line conductor serves as the other of the source or drain, and the gate functions as a field effect transistor. . (2) The delay line according to claim (1), and a reference side transmission line connected in parallel to the delay line via a changeover switch constituted by a microwave semiconductor element; A microwave phase shifter characterized by switching between a reference side transmission line and a reference side transmission line.