An S-band reflective phase shifter based on transversely coupled line couplers

Abstract

The application discloses an S-band reflective phase shifter based on a cross-coupling line coupler, and belongs to the fields of wireless communication and digital signal processing. The reflective phase shifter is designed based on the cross-coupling line coupler, has the advantages of small size, low insertion loss and wide bandwidth compared with existing branch line couplers and Langer couplers, can replace the digital phase shifter used by a traditional phased array antenna, and solves the problems of high cost and high power consumption of the traditional phased array antenna. In addition, the reflective phase shifter can be integrated on a PCB, has the advantages of easy processing, low cost and small size, is easy to be integrated with a planar printed phased array antenna, and realizes the miniaturization and low cost of the phased array antenna.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication and digital signal processing, and more specifically, relates to an S-band reflective phase shifter based on a transverse coupling line coupler. Background Technology

[0002] With the development of fifth-generation (5G) mobile communication and broadband satellite networks, phased array antennas have been recognized as a key technology. They are widely used in military radar, measurement, and civilian satellite communications. Traditional phased array antennas offer advantages such as fast beamforming, continuous scanning, low sidelobe levels, and wide scanning angles. However, they typically employ a large number of high-precision digital phase shifters to achieve beamforming. Digital phase shifters are costly and consume a lot of power, leading to high manufacturing and maintenance costs in phased array antennas. The high complexity, high production costs, difficulty in miniaturization, and maintenance challenges make it difficult to widely adopt traditional phased array antennas in the commercial field. Summary of the Invention

[0003] In view of the above-mentioned defects or improvement needs of the existing technology, the present invention provides an S-band reflective phase shifter based on a transverse coupled line coupler, which has the advantages of easy processing, low cost, small size and wide bandwidth.

[0004] To achieve the above objectives, according to a first aspect of the present invention, an S-band reflective phase shifter based on a transverse coupled-line coupler is provided, comprising: a transverse coupled-line coupler, first and second π-type reflective loads, and a first inductor;

[0005] The transverse coupling line coupler includes two parallel coupling lines and a plurality of first capacitors periodically connected in parallel between the two parallel coupling lines.

[0006] Both the first and second π-type reflective loads include two varactor diodes and a microstrip line connecting them; the first and second π-type reflective loads are respectively connected to the coupling port and the through port of the transverse coupling line coupler; the coupling port of the transverse coupling line coupler is on the same side as the input port, and the through port is on the same side as the output port;

[0007] One end of the first inductor is connected to the microstrip line of the first or second π-type reflective load, and the other end is used to input a DC bias voltage to regulate the phase difference between the input port and the output port.

[0008] According to a second aspect of the invention, a phased array antenna is provided, including a phase shifter as described in the first aspect.

[0009] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0010] The reflective phase shifter proposed in this invention is designed based on a transverse coupled-line coupler. Compared with a branch-line coupler, the transverse coupled-line coupler has a more compact size and a wider bandwidth; compared with a Lange coupler, the transverse coupled-line coupler has a more compact size and lower manufacturing difficulty. Practical measurements have verified that the phase shifter provided by this invention has an insertion loss of 1.5 ± 0.6 dB within a bandwidth of 2.3 GHz to 2.8 GHz. By changing the DC bias voltage applied to the varactor diode, this phase shifter can achieve a continuous 360° phase shift within the bandwidth.

[0011] In summary, the reflective phase shifter proposed in this invention has advantages such as small size, low insertion loss, and wide bandwidth. It can replace the digital phase shifter used in traditional phased array antennas, solving the pain points of high cost and high power consumption of traditional phased array antennas. In addition, the reflective phase shifter proposed in this invention can be integrated on a PCB, which has advantages such as easy processing, low cost, and small size. It is easy to integrate with planar printed phased array antennas, realizing the miniaturization and low cost of phased array antennas. Attached Figure Description

[0012] Figure 1 The circuit diagram of the reflective phase shifter provided in the embodiment of the present invention;

[0013] Figure 2 This is a schematic diagram of the stacked structure of a reflective phase shifter provided in an embodiment of the present invention;

[0014] Figure 3 This is a layout diagram of a reflective phase shifter provided in an embodiment of the present invention;

[0015] Figure 4 An equidistant viewing angle diagram of a reflective phase shifter provided in an embodiment of the present invention;

[0016] Figure 5 Key dimension annotation diagram of the reflective phase shifter provided in the embodiments of the present invention;

[0017] Figure 6 A physical diagram of a reflective phase shifter provided in an embodiment of the present invention;

[0018] Figure 7 The simulation S-parameter curves of the reflective phase shifter provided in the embodiments of the present invention;

[0019] Figure 8 The measured S-parameter curves of the reflective phase shifter provided in the embodiments of the present invention are shown.

[0020] Figure 9 The curve showing the phase shift degree of the reflective phase shifter provided in the embodiment of the present invention as a function of DC bias voltage. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0022] To address the cost and power consumption issues of traditional phased arrays, one approach is to research and design low-cost, low-power, and low-insertion-loss phase shifters. Reflective analog phase shifters can meet these requirements. A typical reflective phase shifter consists of a 3dB coupler and two reflective loads. The reflective loads are connected to the through port and coupling port of the coupler and are usually composed of controlled varactor diodes. By adjusting the bias voltage of the varactor diodes, analog phase shifting of the radio frequency signal can be achieved. Reflective phase shifters offer advantages such as simple manufacturing processes and low cost, and hold promise for solving the cost and power consumption problems faced by phased array antennas.

[0023] However, the vast majority of reflective phase shifters currently use branch-line couplers. Branch-line couplers consist of four 90° microstrip transmission lines orthogonally connected, and typically have a large size and small bandwidth, making them unsuitable for applications requiring compact design and wide bandwidth.

[0024] Based on this, embodiments of the present invention provide an S-band reflective phase shifter based on a transverse coupled-line coupler, comprising: a transverse coupled-line coupler, first and second π-type reflective loads, and a first inductor L1;

[0025] The transverse coupling line coupler includes two parallel coupling lines and a plurality of first capacitors C1 connected in parallel periodically between the two parallel coupling lines.

[0026] Both the first and second π-type reflective loads include two varactor diodes and a microstrip transmission line connecting them; the first and second π-type reflective loads are respectively connected to the coupling port and the through port of the transverse coupling line coupler; the coupling port of the transverse coupling line coupler is on the same side as the input port, and the through port is on the same side as the output port; the input port and the output port are on one of the coupling lines, and the through port and the output port are on the other coupling line;

[0027] One end of the first inductor L1 is connected to the microstrip transmission line of the first or second π-type reflective load, and the other end is used to input a DC bias voltage to regulate the phase difference between the input port and the output port.

[0028] Specifically, the transverse coupling line coupler provided in this embodiment of the invention can be obtained by periodically loading multiple parallel capacitors C1 between two parallel coupling lines.

[0029] The first π-type reflective load and the second π-type reflective load are connected one-to-one to the Coupled port and Through port (i.e., the coupling port and the through port) of the coupler to form a reflective phase shifter. The first and second π-type reflective loads are both composed of two varactor diodes and a microstrip transmission line connected between the varactor diodes.

[0030] Considering an ideal transmission line and an ideal varactor diode (the equivalent series resistance of the varactor diode is 0Ω), the input impedance Z at the load port is... IN The reflection coefficients of the port and the port are respectively:

[0031]

[0032] Where C is the equivalent series capacitance of the four varactor diodes, Z1 and θ1 are the characteristic impedance and electrical length of the microstrip transmission line in the π-type reflective load, respectively (the characteristic impedance and electrical length of the microstrip transmission line in the first and second π-type reflective loads are Z1 and θ1, respectively). Z0 is the characteristic impedance of the coupler port.

[0033] This reflective phase shifter can be equivalent to a two-port network, and its scattering matrix is ​​as follows:

[0034]

[0035] Therefore, the S of this reflective phase shifter 21 The parameter is jΓ, and its insertion loss is:

[0036] |S 21 |=-20log|Γ|

[0037] Phase shift degrees for:

[0038]

[0039] By adjusting the DC bias voltage of the phase shifter, the equivalent capacitance C of the four varactor diodes can be changed simultaneously, thereby altering the input impedance Z at the load port. IN To achieve the phase difference between the control ports (i.e. The purpose is to... The relationship between the DC bias voltage and the equivalent capacitance C of the four varactor diodes varies depending on the type of varactor diode and can be obtained by referring to the varactor diode's datasheet. Using a π-type reflective load can increase the range of reflection coefficient variation, thereby increasing the maximum phase shift range of the phase shifter.

[0040] Preferably, the transverse coupling line coupler further includes at least one second capacitor C2 connected in series between the midpoints of the two parallel coupling lines, used to adjust the coupling coefficient of the coupling lines.

[0041] Preferably, each varactor diode in the first and second π-type reflective loads is connected in series with a second inductor L2. The series inductor resonates with the capacitance of the varactor diode, thereby increasing the maximum phase shift range of the phase shifter.

[0042] To minimize the size of the phase shifter, while also considering the coupler's performance and manufacturing process, the minimum length of the transverse coupling line coupler is preferably set to 0.25λ. g , λ g The wavelength of the medium at the operating center frequency of the phase shifter.

[0043] To minimize the size of the phase shifter, preferably, the input port and the output port are both located on one side of the two parallel coupling lines and are both perpendicular to the two parallel coupling lines; the transmission lines of the first and second π-type reflective loads are placed on the other side of the two parallel coupling lines after at least one bend;

[0044] The bent transmission line is located within the space formed by the input transmission line and the output transmission line in the vertical direction; the width of the space is the sum of the widths of the input transmission line, the output transmission line, and the length of the parallel coupling line.

[0045] Those skilled in the art will know that the characteristic impedance of the input and output transmission lines is typically set to 50Ω; therefore, the widths of the input and output transmission lines are fixed. The bent transmission line lies within the space formed by the input and output transmission lines in the perpendicular direction. That is, the length of the phase shifter is equal to the sum of the length of the coupler and the widths of the input and output transmission lines. The length of the coupler is the length of the parallel coupling line. Therefore, the length of the phase shifter primarily depends on the length of the coupler across the coupling line.

[0046] To facilitate integration with the power divider network of the array antenna, minimize the size of the phase shifter, and achieve good performance, the circuit formed by the transverse coupling line coupler and the first and second π-type reflective loads is preferably an axisymmetric structure.

[0047] Preferably, the phase shifter is integrated on a single-layer dielectric PCB.

[0048] As an example, such as Figure 1-3 As shown, four parallel capacitors C1 are periodically loaded between the two parallel coupling lines of the transverse coupling line coupler, and two second capacitors C2 are also connected in series between the midpoints of the two parallel coupling lines.

[0049] This phase shifter operates in the 2.3GHz-2.8GHz frequency band and is integrated on a single-layer dielectric PCB, such as... Figure 2As shown. To reduce insertion loss, the dielectric substrate used can be high-frequency, low-loss materials such as PTFE, RO4350B, or RO5880 to improve the gain and radiation efficiency of the array antenna. Taking PTFE as an example, its dielectric constant is 2.94, its loss tangent is 0.0016, and its thickness is 0.76 mm.

[0050] Figure 1 In the diagram, Z0' is the characteristic impedance of the transmission line between the parallel capacitors; 2*θ` is the electrical length of the transmission line between the parallel capacitors; and Z2 and θ2 are the characteristic impedance and electrical length of the transmission line loaded between the parallel line couplers, respectively.

[0051] like Figure 3 As shown by the dashed area, four capacitors C1 are connected in parallel between the two parallel coupling lines to form a cross-coupled-line coupler. Additionally, two capacitors C2 and a transmission line are loaded between the parallel coupling lines to adjust the coupling coefficient. π-type reflective loads are connected to the coupled and through ports of the coupler to form a reflective phase shifter. Each π-type reflective load consists of two varactor diodes and a microstrip transmission line connected between the varactor diodes. In this example, the transmission line is bent three times to reduce the space occupied by the phase shifter. Each varactor diode is connected in series with a second inductor L2 to increase the maximum phase shift range.

[0052] A DC bias voltage is applied to the reflective phase shifter through a first inductor L1. One end of L1 receives the DC bias voltage, and the other end is connected to a π-type reflective load transmission line. By adjusting the DC bias voltage, the capacitance values ​​of all varactor diodes are dynamically adjusted, thereby changing the reflection coefficients of the Coupled and Through ports to control the phase difference between Port1 and Port2 (i.e., the input and output ports). Due to the layout characteristics of the cross-coupled line coupler, only one DC bias voltage input is needed to dynamically control the capacitance values ​​of the four varactor diodes. Furthermore, the input bias voltage can be isolated from the RF signal by periodically loaded capacitors in the cross-coupled line coupler, eliminating the need to add DC blocking capacitors at the two ports of the phase shifter, thus simplifying the circuit design for the bias voltage input.

[0053] Key dimensions of the phase shifter are as follows: Figure 5 As shown, the overall design layout presents an axially symmetrical state. Figure 5In this diagram, L3 is the coupler length, L4 is the transmission line length between parallel capacitors; L3 = 4L4, L5 is the transmission line length loaded between parallel line couplers, L6 + L7 + 2L8 is the transmission line length of the load, W1 is the width of the parallel coupler, W2 is the distance between parallel couplers, W3 is the width of the transmission line loaded between parallel line couplers, W4 is the width of the load's transmission line, Slot is a slot opened on the reference ground, Ws and Ls are the width and length of the Slot, and W50 is the width of the input and output transmission lines (for performance reasons, W4 is usually set to be less than W50). The length of the phase shifter is equal to the length of the coupler plus the microstrip transmission line width of the first and second π-type reflective loads, i.e., L3 + 2 * W50.

[0054] The above dimensions were calculated based on transmission line theory and then adjusted and optimized using full-wave electromagnetic simulation software. First, the basic dimensions W1, W2, L3, L4 of the transverse coupling line coupler and the approximate range of the parallel capacitor were determined based on the operating band and transmission line theory. Then, the above parameters were simulated and optimized using full-wave electromagnetic simulation software. Finally, the characteristic impedance Z1, electrical length, and θ1 of the microstrip transmission line within the π-type reflective load were adjusted and optimized using full-wave electromagnetic simulation software (corresponding to W4, L6, L7, L8) to minimize the insertion loss and size of the phase shifter while ensuring that the maximum phase shift is greater than 360°.

[0055] A physical image of the phase shifter is shown below. Figure 6 As shown. Actual measurements show that the core design of this reflective phase shifter occupies 19.3mm * 8.5mm. The air wavelength λ at 2.6GHz is 115.4mm. Therefore, the size represented by λ is: (19.3 / 115.4) * (8.5 / 115.4)λ 2 That is, 0.17 * 0.07λ 2 Therefore, it can be seen that this reflective phase shifter occupies a total of 0.17 × 0.07λ. 2 PCB size.

[0056] Figure 7 The simulated S-parameter curves of the phase shifter are shown. The simulation results indicate that the phase shifter's S-parameters in the 2.3GHz-2.8GHz frequency band... 11 All parameters are below -10dB, exhibiting good return loss. The insertion loss of the phase shifter in the 2.3GHz-2.8GHz band is -1.2±0.5dB.

[0057] Figure 8 The measured S-parameter curves of the phase shifter are shown below. The measured results indicate that the phase shifter's S-parameters in the 2.3GHz-2.8GHz frequency band are... 11All parameters are below -10dB, exhibiting good return loss. The insertion loss of the phase shifter in the 2.3GHz-2.8GHz band is -1.5±0.6dB. The measured insertion loss is 0.4dB higher than the simulation, mainly because the capacitors and inductors used in the phase shifter design are non-ideal components. At this frequency band, capacitors and inductors have parasitic parameter effects, which affect the impedance matching of the circuit and increase transmission loss.

[0058] Figure 9 The curve showing the phase shift degree of the phase shifter as a function of the DC bias voltage is shown. The measured maximum phase shift degree is 365°, which matches the simulated maximum phase shift degree of 367°.

[0059] This invention provides a phased array antenna, including a phase shifter as described in any of the above embodiments.

[0060] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An S-band reflective phase shifter based on a transverse coupled-line coupler, characterized in that, include: Transverse coupling line coupler, first, second Type-reflective load and first inductor; The transverse coupling line coupler includes two parallel coupling lines and a plurality of first capacitors periodically connected in parallel between the two parallel coupling lines. The first and the second Each type of reflective load includes two varactor diodes and a microstrip line connecting them; the first and second... The type of reflective load is connected to the coupling port and the through port of the transverse coupling line coupler respectively; the coupling port of the transverse coupling line coupler is on the same side as the input port, and the through port is on the same side as the output port; One end of the first inductor is connected to the first or second The microstrip line connection of the type reflective load is used at one end, and the other end is used to input a DC bias voltage to regulate the phase difference between the input port and the output port; The input port and the output port are both located on one side of the two parallel coupling lines and are both perpendicular to the two parallel coupling lines. The first and the second The transmission line of the type reflective load is placed on the other side of the two parallel coupling lines by at least one bend; The bent transmission line is located within the space formed by the input transmission line and the output transmission line in the vertical direction; the width of the space is the sum of the widths of the input transmission line, the output transmission line, and the length of the parallel coupling line.

2. The phase shifter as described in claim 1, characterized in that, The length of the transverse coupling line coupler is 0.

25. λ g , λ g The wavelength of the medium at the operating center frequency of the phase shifter.

3. The phase shifter as described in claim 1, characterized in that, The transverse coupling line coupler also includes at least one second capacitor connected in series between the midpoints of the two parallel coupling lines.

4. The phase shifter as described in claim 1, characterized in that, The first and the second Each varactor diode in the type of reflective load is connected in series with a second inductor.

5. The phase shifter as described in claim 1, characterized in that, The transverse coupling line coupler is connected to the first and second... The circuit formed by connecting the type of reflective load has an axisymmetric structure.

6. The phase shifter as described in claim 1, characterized in that, The phase shifter is integrated on a single-layer dielectric PCB.

7. The phase shifter as described in claim 6, characterized in that, The single-layer dielectric PCB is made of PTFE, RO4350B, or RO5880.

8. The phase shifter as claimed in claim 1, characterized in that, The phase shift degree of the phase shifter With the first or second Input impedance of the type reflective load port maximum value Minimum value The following relationship must be satisfied: in, The characteristic impedance of the transverse coupled-line coupler port. , and First or second respectively Characteristic impedance and electrical length of microstrip transmission lines within a type of reflective load. j For imaginary units, Where is the angular frequency, and C is the equivalent series capacitance of the four varactor diodes, which varies with the DC bias voltage.

9. A phased array antenna, characterized in that, Includes the phase shifter as described in any one of claims 1-8.

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