Improved switch line type low-insertion-loss phase shifter

Abstract

The invention discloses an improved switch line type low-insertion-loss phase shifter which comprises a phase shifting main circuit, a first phase shifting auxiliary circuit, a second phase shifting auxiliary circuit, a first T-junction micro-strip power divider, a second T-junction micro-strip power divider, a first single-pole double-throw switch, a second single-pole double-throw switch, a first short-circuit resonance micro-strip line and a second short-circuit resonance micro-strip line. Phase shifting can be achieved on signals under the condition of low insertion loss, the two T-junction microstrip line power dividers are adopted to carry out power division, phase shifting and combination on the two paths of signals respectively to achieve reduction of overall insertion loss, the two single-pole double-throw switch chips are adopted to select the two phase shifting auxiliary paths, and therefore the function of the differential phase shifter is achieved, and the differential phase shifter is suitable for large-scale popularization and application. Different electrical lengths and power dividing ratios of power dividers are adopted for the phase-shifting main circuit and the phase-shifting auxiliary circuit, so that various phase-shifting quantities can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of phase shifters, and in particular relates to a design of an improved switch line type low insertion loss phase shifter. Background Art

[0002] Phase shifters, as a microwave device for guiding the phase of signals, are widely used in electronics, radar, and communication systems, covering beamforming networks, circularly polarized antennas, phase modulation systems, smart antennas, phased arrays, and other fields. With the rapid development of communication technology in my country, the fifth generation of mobile communication technology (5G) has officially entered the commercial era. In 5G, hybrid beamforming (HBF) is a very critical technology. It introduces the advantages of ABF (Adaptive Beam Forming) technology to share a single RF (Radio Frequency) chain for multiple analog signals, achieving a significant reduction in the power consumption and cost of the entire system, and has received widespread attention from academia and industry. A key point in the implementation of hybrid beamforming technology is the implementation of the RF front-end phase shifter. The use of digital phase shifters for fast phase switching can realize the antenna vertical plane beam scanning function. Therefore, the application of 5G Massive MIMO hybrid beamforming brings new challenges to the design of RF digital phase shifters, requiring RF phase shifters to have lower insertion loss.

[0003] Traditional digital phase shifter design structures include load-line type, anti-reflection type and switch type. Switch-type phase shifters include switch-line phase shifters and switch-network phase shifters. Switch-line phase shifters have a simple circuit structure, and the increase in their phase shift depends on the difference in the electrical length of the two transmission lines. Traditional switch-line phase shifters are usually simple in structure, but have a narrow phase shift bandwidth and large insertion loss, making it difficult to meet the current beamforming requirements for phase shifters. Summary of the invention

[0004] The purpose of the present invention is to propose an improved switch linear low insertion loss phase shifter to reduce the hybrid beamforming insertion loss and meet the higher requirements of the 5G system working conditions.

[0005] The technical solution of the present invention is: an improved switch line type low insertion loss phase shifter, comprising a phase shift main circuit, a first phase shift auxiliary circuit, a second phase shift auxiliary circuit, a first T-junction microstrip power divider, a second T-junction microstrip power divider, a first single-pole double-throw switch, a second single-pole double-throw switch, a first short-circuit resonant microstrip line and a second short-circuit resonant microstrip line, the input end of the first T-junction microstrip power divider is used as the input port of the phase shifter, the first output end thereof is connected to the input end of the phase shift main circuit, the second output end thereof is connected to the moving end of the first single-pole double-throw switch, the first fixed end of the first single-pole double-throw switch is connected to the input end of the first phase shift auxiliary circuit The first phase-shift auxiliary circuit is connected to the first fixed end of the second single-pole double-throw switch, the output end of the second phase-shift auxiliary circuit is connected to the second fixed end of the second single-pole double-throw switch, the output end of the second phase-shift main circuit is connected to the first input end of the second T-junction microstrip power divider, the moving end of the second single-pole double-throw switch is connected to the second input end of the second T-junction microstrip power divider, the output end of the second T-junction microstrip power divider serves as the output port of the phase shifter, and the first short-circuit resonant microstrip line and the second short-circuit resonant microstrip line are respectively connected in parallel with the first phase-shift auxiliary circuit.

[0006] Furthermore, the first short-circuited resonant microstrip line and the second short-circuited resonant microstrip line are both quarter-wavelength short-circuited resonant microstrip lines.

[0007] Furthermore, the input port and the output port of the phase shifter both use 50-ohm microstrip lines.

[0008] Furthermore, the phase shift main circuit uses a 50 ohm microstrip line with an electrical length of 92 degrees.

[0009] Furthermore, the first phase-shift auxiliary path uses a 56-ohm microstrip line with an electrical length of 35 degrees.

[0010] Furthermore, when the phase shift amount of the phase shifter is 90 degrees, the second phase shift auxiliary path uses a 38-ohm microstrip line with an electrical length of 44 degrees.

[0011] Furthermore, when the phase shift amount of the phase shifter is 45 degrees, the second phase shift auxiliary path uses a 38-ohm microstrip line with an electrical length of 32 degrees.

[0012] Furthermore, the phase shift amount Δφ of the phase shifter is:

[0013]

[0014] where Δφ A Indicates the phase shift when the first single-pole double-throw switch and the second single-pole double-throw switch are connected to the first phase-shift auxiliary circuit, Δφ B It represents the phase shift when the first single-pole double-throw switch and the second single-pole double-throw switch are connected to the second phase-shift auxiliary circuit, θ A represents the electrical length of the first phase-shift auxiliary circuit, θ Brepresents the electrical length of the second phase-shift auxiliary circuit, θ SPDT The first SPDT switch and the second SPDT switch bring about a phase shift, θ m represents the electrical length of the phase-shifting main path, and K represents the power division ratio between the first T-junction microstrip power divider and the second T-junction microstrip power divider.

[0015] The beneficial effects of the present invention are:

[0016] (1) The present invention realizes the function of differential phase shifting by utilizing two T-junction microstrip line power dividers, a phase shift main path, two short-circuit resonant microstrip lines and two single-pole double-throw switches to select a phase shift auxiliary path. The invention has low insertion loss and a simple structure. Different phase shift amounts can be achieved by changing the power division ratio of the two T-junction microstrip line power dividers and the electrical length of the phase shift main path and the electrical length of the phase shift auxiliary path.

[0017] (2) The present invention realizes a low insertion loss phase shifter by coupling different phase shift signals caused by passing through microstrip lines of different electrical lengths. The insertion loss of the designed phase shifter is less than 0.57dB and the return loss is less than -20dB within the working frequency band. The circuit size is 0.25*0.4(λg).

[0018] (3) The circuit structure of the present invention is simple and can be manufactured by ordinary printed circuit board technology on the market. It has the advantages of low cost and easy processing. It is suitable for hybrid beamforming and has certain application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure shows a circuit structure diagram of an improved switch linear low insertion loss phase shifter provided by an embodiment of the present invention.

[0020] Figure 2 The figure shows a plan view of a 90-degree phase shift layout of an improved switch linear low insertion loss phase shifter provided in an embodiment of the present invention.

[0021] Figure 3 The figure shows a plan view of a 45-degree phase shift layout of an improved switch linear low insertion loss phase shifter provided by an embodiment of the present invention.

[0022] Figure 4 It is a schematic diagram showing the simulation and measured parameters of the insertion loss and return loss of the 90-degree phase shifter provided by the embodiment of the present invention in the frequency band from 3.3 GHz to 3.8 GHz.

[0023] Figure 5 It is a schematic diagram of the simulation and measured parameters of the insertion loss and return loss of the 45-degree phase shifter provided by the embodiment of the present invention in the frequency band from 3.3 GHz to 3.8 GHz.

[0024] Figure 6FIG. 1 is a schematic diagram showing the phase response of a 45-degree phase shifter and a 90-degree phase shifter provided by an embodiment of the present invention within a working frequency band of 3.3 GHz to 3.8 GHz. DETAILED DESCRIPTION

[0025] Now, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the accompanying drawings are only exemplary and are intended to explain the principles and spirit of the present invention, rather than to limit the scope of the present invention.

[0026] The embodiment of the present invention provides an improved switch linear low insertion loss phase shifter, such as Figure 1 As shown, it includes a phase-shifting main circuit, a first phase-shifting auxiliary circuit, a second phase-shifting auxiliary circuit, a first T-junction microstrip power divider, a second T-junction microstrip power divider, a first single-pole double-throw switch, a second single-pole double-throw switch, a first short-circuited resonant microstrip line, and a second short-circuited resonant microstrip line. The input end of the first T-junction microstrip power divider serves as the input port of the phase shifter, the first output end of the first T-junction microstrip power divider is connected to the input end of the phase-shifting main circuit, the second output end of the first T-junction microstrip power divider is connected to the moving end of the first single-pole double-throw switch, the first fixed end of the first single-pole double-throw switch is connected to the input end of the first phase-shifting auxiliary circuit, and the second fixed end of the first single-pole double-throw switch is connected to the moving end of the first phase-shifting auxiliary circuit. The input end of the second phase-shift auxiliary circuit is connected, the output end of the first phase-shift auxiliary circuit is connected to the first fixed end of the second single-pole double-throw switch, the output end of the second phase-shift auxiliary circuit is connected to the second fixed end of the second single-pole double-throw switch, the output end of the phase-shift main circuit is connected to the first input end of the second T-junction microstrip power divider, the moving end of the second single-pole double-throw switch is connected to the second input end of the second T-junction microstrip power divider, the output end of the second T-junction microstrip power divider serves as the output port of the phase shifter, and the first short-circuit resonant microstrip line and the second short-circuit resonant microstrip line are respectively connected in parallel with the first phase-shift auxiliary circuit.

[0027] In an embodiment of the present invention, the improved switch linear low insertion loss phase shifter is a differential phase shifter, and the first phase shift auxiliary path and the second phase shift auxiliary path are selected by the first single-pole double-throw switch and the second single-pole double-throw switch, and the first single-pole double-throw switch and the second single-pole double-throw switch must be connected to one phase shift auxiliary path at the same time. When the first single-pole double-throw switch and the second single-pole double-throw switch are connected to the first phase shift auxiliary path, the second phase shift auxiliary path does not participate in the coupling of the output port, and the voltage wave output by the output port is the vector sum of the voltage wave phase-shifted by the phase shift main path and the voltage wave phase-shifted by the first phase shift auxiliary path. When the first single-pole double-throw switch and the second single-pole double-throw switch are connected to the second phase shift auxiliary path, the first phase shift auxiliary path does not participate in the coupling of the output port, and the voltage wave output by the output port is the vector sum of the voltage wave phase-shifted by the phase shift main path and the voltage wave phase-shifted by the second phase shift auxiliary path. According to the principle of vector synthesis, output signals of different phases can be synthesized at the output port, and a differential phase shifter can be obtained by selecting a single-pole double-throw switch.

[0028] In the embodiment of the present invention, the first single-pole double-throw switch and the second single-pole double-throw switch adopt single-pole double-throw switch chips produced by pSemi, a subsidiary of Murata, and the chip model is PE42426.

[0029] In an embodiment of the present invention, when the phase of the signal through the phase-shifting main path of the improved switch linear low insertion loss phase shifter is the same as the phase of the signal through the phase-shifting auxiliary path, the insertion loss of the phase shifter is extremely small. The improved switch linear low insertion loss phase shifter network is a lossless reciprocal network, and the circuit input and output are symmetrical structures. The functions of the first T-junction microstrip power divider and the second T-junction microstrip power divider are as follows: the first T-junction microstrip power divider transmits the RF input signal to the phase-shifting main path and the selected phase-shifting auxiliary path respectively according to the set power division ratio, and the second T-junction microstrip power divider and the first T-junction microstrip power divider adopt the same and symmetrical topological structure, and combine the signal through the phase-shifting main path and the signal through the phase-shifting auxiliary path, and finally output to the output port through vector addition.

[0030] In the embodiment of the present invention, the first short-circuited resonant microstrip line and the second short-circuited resonant microstrip line are both quarter-wavelength short-circuited resonant microstrip lines, which serve to increase the working bandwidth of the phase shifter.

[0031] In an embodiment of the present invention, the improved switch linear low insertion loss phase shifter also includes a dielectric substrate, the bottom of the dielectric substrate is grounded, and a Rogers RO4350B dielectric substrate is used, whose dielectric constant is 3.66, the dielectric substrate thickness is 20 mil, the loss tangent value is 0.0037, and the surface copper thickness is 1 oz.

[0032] In the embodiment of the present invention, the impedance of the first T-junction microstrip power divider and the second T-junction microstrip power divider are preliminarily designed by the following formula:

[0033]

[0034] Where K represents the power division ratio of the first T-junction microstrip power divider and the second T-junction microstrip power divider, P Main Indicates the power passing through the phase-shifted main circuit, P A Represents the power passing through the phase-shift auxiliary circuit, Z in1 Represents the input impedance of the phase-shift main circuit, Z in2 Represents the input impedance of the phase-shift auxiliary circuit, Z P Indicates the impedance of the input port and the output port, when the branches after the first T-section microstrip line power divider are all quarter-wavelength microstrip lines:

[0035]

[0036] Where Z mrepresents the characteristic impedance of the phase-shifting main path connected to the first T-section microstrip line power divider after branching, Z0 represents the characteristic impedance of the microstrip line connected to the first T-section microstrip line power divider and the phase-shifting main path, Z1 represents the characteristic impedance of the microstrip line connected to the first T-section microstrip line power divider and the phase-shifting auxiliary path, which is set to 85 ohms in the embodiment of the present invention, and Z A It represents the characteristic impedance of the phase-shift auxiliary path connected via the first single-pole double-throw switch after branching from the first T-section microstrip line power divider, which is set to 77 ohms in the embodiment of the present invention.

[0037] When the first single-pole double-throw switch and the second single-pole double-throw switch are connected to the first phase-shift auxiliary circuit, the phase shift amount Δφ A for:

[0038]

[0039] When the first single-pole double-throw switch and the second single-pole double-throw switch are connected to the second phase-shift auxiliary circuit, the phase shift amount Δφ B for:

[0040]

[0041] Then the phase shift amount Δφ of the phase shifter is:

[0042]

[0043] where θ A represents the electrical length of the first phase-shift auxiliary circuit, θ B represents the electrical length of the second phase-shift auxiliary circuit, θ SPDT The first SPDT switch and the second SPDT switch bring about a phase shift, θ m Indicates the electrical length of the phase-shift main circuit.

[0044] Through the above phase shift analysis, if a large phase shift is to be achieved, the phase difference of the output signal under the coupling of the two states of the switch needs to be large. When the electrical length difference between the phase-shift auxiliary circuit and the phase-shift main circuit exceeds 60 degrees, an insertion loss of 0.1dB may be introduced, and the return loss will also increase. Therefore, the phase shift and insertion loss need to be comprehensively considered during design.

[0045] In the embodiment of the present invention, the input port and output port of the phase shifter both use 50 ohm microstrip lines, and the 50 ohm input and output microstrip lines are used to match the impedance of the RF signal input and output ends with the standard SMA connector. The main phase shift path uses a 50 ohm microstrip line with an electrical length of 92 degrees. The first phase shift auxiliary path uses a 56 ohm microstrip line with an electrical length of 35 degrees.

[0046] In the embodiment of the present invention, Figure 2 As shown, when the phase shift amount of the phase shifter is 90 degrees, the second phase shift auxiliary path uses a 38-ohm microstrip line with an electrical length of 44 degrees.

[0047] In the embodiment of the present invention, Figure 3 As shown, when the phase shift amount of the phase shifter is 45 degrees, the second phase shift auxiliary path uses a 38-ohm microstrip line with an electrical length of 32 degrees.

[0048] like Figure 2 and Figure 3 As shown, the two quarter-wavelength short-circuited resonant microstrip lines are both grounded through via hole 5.

[0049] In the embodiment of the present invention, in order to reduce the circuit size and achieve miniaturization, it is necessary to bend the longer microstrip line to form a hairpin-like structure.

[0050] The working principle and process of the improved switch linear low insertion loss phase shifter provided by the embodiment of the present invention are as follows: when two single-pole double-throw switches are connected to the first phase-shift auxiliary path, the signal is divided into two parts after passing through the first T-junction microstrip power divider, one part passes through the phase-shift main path to generate a phase shift, and the other part passes through the first phase-shift auxiliary path to generate another phase shift, and the signal at the output end is obtained by vector synthesis of the two parts of the signal; when two single-pole double-throw switches are connected to the second phase-shift auxiliary path, the signal is divided into two parts after passing through the first T-junction microstrip power divider, one part passes through the phase-shift main path to generate a phase shift, and the other part passes through the second phase-shift auxiliary path to generate another phase shift, and the signal at the output end is obtained by vector synthesis of the two parts of the signal; the final digital phase shifter phase shift amount is obtained by the phase shift difference of the above two steps, and the short-circuited resonant microstrip line connected to the first phase-shift auxiliary path can effectively increase the working frequency band.

[0051] The effects of the present invention are further described below through simulation analysis.

[0052] Figure 4 The insertion loss and return loss simulation and measured parameters of the 90-degree phase shifter in the 3.3GHz to 3.8GHz frequency band show that the return loss is better than 20dB in the 2.49GHz to 4.25GHz range, the insertion loss is less than 0.75dB at the center frequency of 3.5GHz, the insertion loss of the phase shifter is less than 0.85dB within the phase shift bandwidth of 400MHz, and the amplitude imbalance within the band is 0.2dB.

[0053] Figure 5 The insertion loss and return loss simulation and measured parameters of the 45-degree phase shifter in the 3.3GHz to 3.8GHz frequency band show that the return loss is better than 20dB in the 2.93GHz to 4.50GHz range, and the insertion loss is less than 0.65dB at the center frequency of 3.5GHz. The insertion loss of the phase shifter is less than 0.7dB within the bandwidth, and the amplitude imbalance within the band is less than 0.1dB.

[0054] Figure 6The phase response of the phase shifter for the 45-degree phase shifter and the 90-degree phase shifter in the operating frequency band of 3.3GHz to 3.8GHz is 45±5 degrees in the frequency range of 3.18GHz to 4.13GHz, and 90±5 degrees in the frequency range of 2.94GHz to 3.81GHz.

[0055] Based on the above analysis and simulation, the improved switch linear low insertion loss phase shifter provided by the present invention can achieve extremely low insertion loss within the working frequency band. When it is a 90-degree phase shifter, it has an insertion loss of less than 0.57dB, an in-band amplitude imbalance of less than 0.2dB, and a return loss of less than 20dB. When it is a 45-degree phase shifter, it has an insertion loss of less than 0.7dB, an in-band amplitude imbalance of less than 0.1dB, and a return loss of less than 20dB. It has good performance and can be applied to radio frequency systems.

[0056] In the description of this embodiment, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features, and in the description of the present invention, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0057] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. An improved switch-line low insertion loss phase shifter, characterized in that: The invention comprises a phase shift main circuit, a first phase shift auxiliary circuit, a second phase shift auxiliary circuit, a first T-junction microstrip power divider, a second T-junction microstrip power divider, a first single-pole double-throw switch, a second single-pole double-throw switch, a first short-circuit resonant microstrip line, and a second short-circuit resonant microstrip line, wherein the input end of the first T-junction microstrip power divider is used as the input port of the phase shifter, the first output end thereof is connected to the input end of the phase shift main circuit, the second output end thereof is connected to the moving end of the first single-pole double-throw switch, the first fixed end of the first single-pole double-throw switch is connected to the input end of the first phase shift auxiliary circuit, and the second fixed end thereof is connected to the moving end of the second phase shift auxiliary circuit. The input end of the first phase-shift auxiliary circuit is connected to the first fixed end of the second single-pole double-throw switch, the output end of the second phase-shift auxiliary circuit is connected to the second fixed end of the second single-pole double-throw switch, the output end of the phase-shift main circuit is connected to the first input end of the second T-junction microstrip power divider, the moving end of the second single-pole double-throw switch is connected to the second input end of the second T-junction microstrip power divider, the output end of the second T-junction microstrip power divider serves as the output port of the phase shifter, and the first short-circuited resonant microstrip line and the second short-circuited resonant microstrip line are respectively connected in parallel with the first phase-shift auxiliary circuit.

2. The improved switch-line low insertion loss phase shifter according to claim 1, characterized in that: The first short-circuited resonant microstrip line and the second short-circuited resonant microstrip line are both quarter-wavelength short-circuited resonant microstrip lines.

3. The improved switch-line low insertion loss phase shifter according to claim 1, characterized in that: The input port and the output port of the phase shifter both adopt 50 ohm microstrip lines.

4. The improved switch-line low insertion loss phase shifter according to claim 1, characterized in that: The phase shift main circuit adopts a 50 ohm microstrip line with an electrical length of 92 degrees.

5. The improved switch-line low insertion loss phase shifter according to claim 1, characterized in that: The first phase-shift auxiliary path uses a 56-ohm microstrip line with an electrical length of 35 degrees.

6. The improved switch-line low insertion loss phase shifter according to claim 1, characterized in that: When the phase shift amount of the phase shifter is 90 degrees, the second phase shift auxiliary path uses a 38-ohm microstrip line with an electrical length of 44 degrees.

7. The improved switch-line low insertion loss phase shifter according to claim 1, characterized in that: When the phase shift amount of the phase shifter is 45 degrees, the second phase shift auxiliary path uses a 38-ohm microstrip line with an electrical length of 32 degrees.

8. The improved switch-line low insertion loss phase shifter according to claim 1, characterized in that: The phase shift amount Δφ of the phase shifter is: where Δφ A Indicates the phase shift when the first single-pole double-throw switch and the second single-pole double-throw switch are connected to the first phase-shift auxiliary circuit, Δφ B It represents the phase shift when the first single-pole double-throw switch and the second single-pole double-throw switch are connected to the second phase-shift auxiliary circuit, θ A represents the electrical length of the first phase-shift auxiliary circuit, θ B represents the electrical length of the second phase-shift auxiliary circuit, θ SPDT The first SPDT switch and the second SPDT switch bring about a phase shift, θ m represents the electrical length of the phase-shifting main path, and K represents the power division ratio between the first T-junction microstrip power divider and the second T-junction microstrip power divider.

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