RU2639992C1 - Discrete microwave phase shifter - Google Patents

Abstract

FIELD: radio engineering, communication.SUBSTANCE: discrete microwave phase shifter of a pass-through type matched to the main-line impedance ρis made on the basis of connecting the segments of transmission lines and control elements, preferably diodes. The input and output of the phase shifting circuit of the phase shifter are connected via a control element. The phase shifting circuit of the phase shifter contains a low-pass filter in the form of a serial connection of three (in the case of a discrete sample larger than 90°) or two (in the case of a disc that is less than or equal to 90°) segments of the transmission line, to the places (points) their free ends (the ends of the central conductors) are connected along the microwave with the body (screen) through the control elements, the geometrical parameters of these segments and loops are chosen from the condition of providing a quarter-wave electrical length of each l apart from the transmission input (output) shifting circuit to the nearest point of connection to the housing (TV), and the wave resistance of these segments exceeds ρ.EFFECT: reduction of parasitic transmission loss.4 cl, 3 dwg

Description

The invention relates to electronic microwave technology, in particular to pass-through discrete semiconductor phase shifters, and can be used in phase modulators, phase compensators, phased array antennas and other electronic devices for controlling the phase of electromagnetic waves.

One of the main characteristics of loop-through phase shifters that determine the scope of their application is spurious transmission loss.

There are known schemes of two-channel phase shifters, the operation of which is based on switching on by means of switching elements (pin diodes, field effect transistors, microelectromechanical switches) by a command of a signal to the signal transmission line of two phase-shifting circuits (FSC), the difference in electric lengths of which provides the necessary phase discretion due to the finite speed propagation of an electromagnetic wave in a line (see G. Khizh and others. Microwave phase shifters and switches: features of creating pin integral diodes in an integral new performance.M.: Radio and Communications, 1984, p. 168). However, traditional circuits include channel switches containing at least two switching elements, which leads to an inevitable increase in losses, since spurious transmission losses are mainly caused by losses in these elements.

с волновым сопротивлением ρ₀, совпадающим с волновым сопротивлением линии 1, в которую включен фазовращатель, а к середине этого участка через диод D₂ подключен короткозамкнутый отрезок линии 3. Вход и выход ФЦС соединены через последовательно включенный диод D₁. Вход (выход) ФЦС фактически совпадает с местом (точкой) «Т» присоединения к ней управляющего элемента (диода).Closest to the claimed phase shifter is a loop type phase shifter (see A. Chizhov, Multiple Impedance Method in the Study of Microwave Circuits. M: Radio Engineering, 2014, p. 147-147). The topology of such a device is shown in FIG. 1. FSC known phase shifter is a section of transmission line 2 length

with impedance ρ _0, which coincides with the characteristic impedance of line 1, which includes a phase shifter, and the middle portion of the diode D ₂ is connected shorted line segment 3. The input and output of DSF are connected via series-connected diode D _1. The input (output) of the FCS actually coincides with the place (point) “T” of the connection of the control element (diode) to it.

и волновым сопротивлением 0,5ρ₀. Данный шлейф с отрезком линии передачи 3 имеет электрическую длину ~λ/4 (представляет собой четвертьволновый резонатор) и практически не оказывает влияния на фазу СВЧ сигнала (λ - длина волны в линии передачи).When the diodes are closed, the microwave signal passes without reflection along section 2 of line 1. Moreover, the diodes D ₁ and D ₂ have a large resistance compared to ρ ₀ and do not affect the signal transmission. In the open diode mode, the microwave signal passes through the diode D ₁ , and the section (segment) 2 can be represented as a loop 0.5 connected to line 1

and wave impedance 0.5ρ ₀ . This loop with a segment of transmission line 3 has an electric length of ~ λ / 4 (represents a quarter-wave resonator) and practically does not affect the phase of the microwave signal (λ is the wavelength in the transmission line).

Compared with a two-channel phase shifter, the number of switching (control) elements in the loop type phase shifter can be reduced to two, however, its transmission loss remains significant, which can be confirmed by a numerical estimate of their value.

When evaluating the parasitic transmission loss of a known phase shifter in open diode mode, it can be assumed that the losses in the transmission lines are negligible, the diodes in the open state are the active resistance R _S = 2 Ohms and ρ ₀ = 50 Ohms. Losses in the diode D ₁ depend only on the ratio of R _S and ρ ₀ and are ~ 0.17 dB. Losses in the diode D ₂ also depend on the ratio of the lengths and wave impedances of segments 2 and 3.

For a 180 ° discrete, the electrical length of line 2 is ~ λ / 2, and the length of line 3 is zero. The equivalent resistance, connected in parallel to line 1, of a λ / 4 loop with a wave impedance of 0.5ρ ₀ loaded on R _S will be ρ ₀ ² / 4R _S. Accordingly, the signal loss in this resistance (i.e., in the diode D ₂ ) will be ~ 0.64 dB. The total loss in the diodes D ₁ and D ₂ will be ~ 0.81 dB.

For a 90 ° discrete (in open diode mode), the electric length of the section (segment) 2 will be λ / 4. If we assume that the wave impedance of segment 3 is 0.5 ρ ₀ , then the electric lengths of half-folded segment 2 and segment 3 are the same. Using the well-known expression for the input impedance of a long line loaded with resistance, the line segments 2,3 and the diode D ₂ can be replaced by an equivalent resistance connected in parallel to line 1, the value ρ ₀ ² / 2R _S. Accordingly, the loss in the diode D ₂ will be ~ 0.33 dB, and in general, the loss of the phase shifter in the diodes D ₁ and D ₂ for a 90 ° discrete will be ~ 0.5 dB.

The technical effect to which the proposed solution is aimed is to reduce spurious transmission losses.

This effect is achieved by the fact that in a discrete microwave phase shifter of the loop type, matched to the wave impedance ρ _{0 of the} main transmission line, made on the basis of the connection of segments of the transmission line and control elements, mainly diodes, the input and output of the phase-shifting circuit of which are connected through a control element, phase-shifting circuit the phase shifter contains a low-pass filter in the form of a series connection of three (in the case of a discrete of more than 90 °) or two (in the case of a discrete of less than or equal to 90 °) feeders, to the connection points (points) of which loops (loop) are connected, and their free ends (ends of the central conductors) are connected via microwave to the case (screen) via control elements, the geometric parameters of the mentioned segments and loops (loop) are selected from the condition for providing a quarter-wave the electrical length of each transmission line from the input (output) of the phase-shifting circuit to the nearest point of connection with the housing (screen), and the wave impedances of these segments exceed ρ ₀ .

Between both the input and the output of the phase-shifting circuit and adjacent high-resistance segments, segments of the transmission line with a wave resistance of ρ ₀ can be sequentially connected.

In the case of a discrete of less than or equal to 90 °, a segment of the transmission line can be connected sequentially via microwave between the control element and the housing (screen).

An open segment of the transmission line can be connected to the place (point) of the connection of each of the above loops with the corresponding control element.

An important feature of the proposed phase shifter is the use in its phase-shifting circuit of the low-pass filter, which is a series-parallel connection of segments of the transmission line. Such filters, when changing over a sufficiently wide range of lengths and corresponding wave impedances of these segments, can retain their characteristics, including electrical length determining phase shift. This property provides the ability to reduce the loss of the phase shifter due to the implementation of the necessary values of the lengths and wave impedances of the components of the low-pass filter.

The invention is illustrated by drawings.

In FIG. 2a is a schematic representation of the proposed phase shifter with a discrete of less than or equal to 90 °, where:

1 - main transmission line;

2, 2 '- segments of the transmission line;

3 - loop;

D ₁ and D ₂ - control elements (diodes).

The phase shifter shown in FIG. 2a, is included in the main transmission line 1 with a wave resistance of ρ ₀ , the input and output of its PSC are connected through a diode D ₁ . The FSC includes a low-pass filter, made in the form of two approximately identical series-connected segments of the transmission line 2 and 2 'with a wave impedance ρ ₁ greater than ρ ₀ , to the place (point) of connection of which a loop 3 with a wave impedance ρ ₂ is connected, and its free end (end central conductor) is connected to the housing through a diode D ₂ . The electric length of the transmission line from the FSC input (output) to the connection to the housing through segments 2 (2 '), 3 and the diode D _{2 is} approximately equal to λ / 4 (λ is the wavelength in the segment of the transmission line).

Such a phase shifter operates as follows.

When the diodes are off, the microwave signal passes through the FSC, in which the segments of line 2 (2 ') are inductive in nature, and segment 3 is capacitive in nature. The method of calculating the parameters formed by these segments and the low-pass filter loop is known. Diodes D ₁ and D ₂ represent a large resistance and do not affect the transmission coefficient. When the control signal is turned on, the diodes will have a resistance R _S. In this case, the microwave signal passes through the diode D ₁ . The FSC can be represented as a short-circuited through R _s segment of the transmission line with an electrical length of approximately λ / 4, connected to transmission line 1, which represents a large resistance compared to ρ ₀ and does not affect the passage of the microwave signal.

The considered circuit is effective if the low-pass filter in the FSC has a phase shift close to or greater than the specified discrete phase shifter discrete. By changing ρ ₁ and ρ ₂ segments, as well as the ratio of their lengths, it is possible to implement a phase shifter with a phase shift of up to 90 °.

To increase the passband of the phase shifter, it is advisable to include segments of transmission lines 4 with wave impedance ρ ₀ in the FSC at the input and output, while the total electric length of the segments 2 (2 '), 3, 4 should be approximately equal to λ / 4. Such a phase shifter is shown in FIG. 2b.

In some cases, for discharges with small discrepancies, it is advisable to install a piece of conductor (or transmission line) 5 between the diodes D ₂ and the housing (screen) due to the limited technological capabilities for implementing resistances of more than 100 Ohms, as indicated in FIG. 2c. The length of this segment depends on the discrete value of the phase shifter, but in this case, the total electric length of the segments 2 (2 '), 3, 4, 5 should be approximately equal to λ / 4.

When implementing a phase shifter, it may turn out that the calculated total electric length of segments 2 (2 ') and 3 at maximum wave impedances can exceed λ / 4. In this case, to the place (point) of connection of the segment 3 and the diode D _2, you can attach an additional capacitance in the form of a segment of the transmission line at which the necessary low-pass characteristic is realized (see Fig. 2d).

In FIG. 3a shows a phase shifter circuit for discrete over 90 °, where:

1 - main transmission line;

2, 5, 2 '- segments of the transmission line in the low-pass filter;

3, 3 '- loops;

D ₁ , D ₂ , D ₃ - control elements (diodes).

The low-pass filter in the composition of such a phase shifter is made in the form of three series-connected segments of the transmission line 2, 5, 2 'with a wave impedance of more than ρ ₀ , to the connection points (points) of which are connected 3 and 3' loops connected by free ends to the body (screen) through control elements D ₂ and D ₃ . The electrical length of the transmission line, including segments 2 and 3 (2 'and 3') in FIG. 3a and 2, 3, 4 (2 ', 3', 4 ') in FIG. 3b, 3c is approximately equal to a quarter of the wavelength in this transmission line. Segments 4, 4 'and 6, 6' are structurally and structurally similar to segments 4 and 6 in FIG. 2b and 2d, respectively. Obviously, the circuit of FIG. 3a should be approximately symmetrical, and segments 2 and 2 'and loops 3 and 3' in size are approximately equal to each other in pairs.

To estimate the transmission loss of the proposed phase shifter for a 90 ° discrete in the case of open diodes D ₁ and D ₂ according to the scheme in FIG. 2a, it is convenient to choose ρ ₁ = 2ρ ₂ . In this case, segments 2 (2 ') and 3 can be represented in the form of a loop with an electric length of ~ λ / 4 and wave impedance ρ ₂ . It should be noted that in a real design the length of the segment 2 (2 ') is significantly less than the length of the segment 3. The equivalent resistance of this loop connected to line 1 and loaded on the resistance R _S is ρ ₂ ² / R _S. For the value ρ ₀ = 50 Ohm, R _S = 2 Ohm, ρ ₂ = 80 Ohm, the loss in the diode D ₁ is ~ 0.17 dB, the loss in the diode D ₂ ~ 0.06 dB, the total loss of the phase shifter in the diodes D ₁ and D ₂ are ~ 0.23 dB, which is significantly less than that of the prototype phase shifter for a 90 ° discrete.

You can also estimate the transmission loss of the phase shifter for 180 ° discrete in the case of open diodes D ₁ , D ₂ and D ₃ (Fig. 3a) under the same conditions as for the 90 ° discrete indicated above. Losses in the diodes D ₂ and D ₃ are ~ 0.06 dB each, in the diode D ₁ ~ 0.17 dB. Thus, the total loss of the phase shifter in the diodes D ₁ , D ₂ and D ₃ is 0.29 dB, which is significantly lower than that of the prototype phase shifter for 180 ° discrete.

As follows from the above calculations, the execution of the segments of the transmission line and the loops forming the low-pass filter with the maximum possible, obviously exceeding ρ ₀ , wave impedance and geometric parameters, providing a quarter-wave electric length of each transmission line from the FSC input (output) to the nearest connection point with case (screen) are a prerequisite for the maximum reduction in transmission loss of the proposed phase shifter.

Implementation example.

A phase shifter with a 90 ° discrete is designed and manufactured for operation in the S-frequency range. The device is made on a polycrust substrate with a thickness of 0.5 mm, mounted on a metal base. The width of the transmission line segments is ~ 0.5 mm, the high-resistance segments and the loop are ~ 0.12 mm. As the switching elements used diodes MA4L001-134 company M / A-COM. Spurious losses in the center of the passband are ~ 0.3 dB at a control current of 10 mA, losses with closed diodes are ~ 0.15 dB.

Claims (4)

1. Discrete microwave pass-through phase shifter, consistent with the impedance ρ _{0 of the} main transmission line, made on the basis of a connection of segments of transmission lines and control elements, mainly diodes, the input and output of the phase-shifting circuit of which are connected through a control element, characterized in that the phase-shifting circuit of the phase shifter contains a low-pass filter in the form of a series connection of three (in the case of a discrete greater than 90 °) or two (in the case of a discrete less than or equal to 90 °) segments of the transmission line, places (points) of the connection of which the loops (loop) are connected, and their free ends (the ends of the central conductors) are connected via microwave to the case (screen) via control elements, the geometric parameters of the mentioned segments and loops (loop) are selected from the condition of ensuring a quarter-wave electric length of each transmission lines from the input (output) of the phase-shifting circuit to the nearest point of connection with the housing (screen), and the wave impedances of these segments exceed ρ ₀ . 2. The phase shifter according to claim 1, characterized in that between the input and output of the phase-shifting circuit and adjacent high-resistance segments, segments of the transmission line with wave impedance ρ ₀ are connected in series. 3. The phase shifter according to claim 1, characterized in that, in the case of a discrete of less than or equal to 90 °, a segment of the transmission line is connected sequentially along the microwave between the control element and the housing (screen). 4. The phase shifter according to claim 1, characterized in that an open segment of the transmission line is connected to the place (point) of the connection of each of the above loops with the corresponding control element.

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