S-band reflection-type phase shifter based on cross-direction coupling line coupler

Abstract

The invention discloses an S-band reflection type phase shifter based on a cross-direction coupling line coupler, and belongs to the field of wireless communication and digital signal processing, the reflection type phase shifter is designed based on the cross-direction coupling line coupler, and compared with an existing branch line coupler and an existing Lange coupler, the S-band reflection type phase shifter has the advantages of being small in size, low in insertion loss, wide in broadband and the like. A digital phase shifter used by a traditional phased-array antenna can be replaced, and the pain point problems of high cost, high power consumption and the like of the traditional phased-array antenna are solved; besides, the reflective phase shifter provided by the invention can be integrated on a PCB, has the advantages of being easy to process, low in cost, small in size and the like, is easy to integrate with a planar printing phased array antenna, and realizes miniaturization and low cost of the phased array antenna.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication and digital signal processing, and more particularly, relates to an S-band reflective phase shifter based on a transverse coupled line coupler. Background Art

[0002] With the development of fifth-generation (5G) mobile communications and broadband satellite networks, phased array antennas have become 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 a wide scanning angle. However, they typically use a large number of high-precision digital phase shifters to achieve beamforming. Digital phase shifters are expensive and consume a lot of power. Their extensive use in phased array antennas results in high manufacturing and maintenance costs. Disadvantages such as high complexity, high production costs, difficulty in miniaturization, and difficult maintenance make traditional phased array antennas difficult to promote and apply in commercial applications. Summary of the Invention

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

[0004] To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided 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;

[0005] The cross-coupling line coupler comprises two parallel coupling lines and a plurality of first capacitors periodically connected in parallel between the two parallel coupling lines;

[0006] The first and second π-type reflective loads each include two varactor diodes and a microstrip line connected therebetween; the first and second π-type reflective loads are respectively connected to the coupled port and the through port of the cross-coupled line coupler in a one-to-one correspondence; the coupled port of the cross-coupled 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 adjust the phase difference between the input port and the output port.

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

[0009] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0010] The reflective phase shifter proposed in this invention is based on a cross-coupled line coupler design. Compared to branch-line couplers, the cross-coupled line coupler offers a more compact design and wider bandwidth; compared to Lange couplers, the cross-coupled line coupler offers a more compact design and lower manufacturing complexity. Field measurements have demonstrated an insertion loss of 1.5±0.6dB within a bandwidth of 2.3GHz to 2.8GHz. By varying the DC bias voltage applied to the varactor diode, the phase shifter can achieve a continuous 360° phase shift within the bandwidth.

[0011] In summary, the reflective phase shifter proposed in the present invention has the advantages of 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 traditional phased array antennas such as high cost and high power consumption. In addition, the reflective phase shifter proposed in the present invention can be integrated on a PCB, and has the advantages of easy processing, low cost, and small size. It is easy to integrate with a planar printed phased array antenna, thereby realizing the miniaturization and low cost of the phased array antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A circuit schematic diagram of a reflective phase shifter provided in an embodiment of the present invention;

[0013] Figure 2 A schematic diagram of the stacking of a reflective phase shifter provided in an embodiment of the present invention;

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

[0015] Figure 4 An isometric view of a reflective phase shifter provided by an embodiment of the present invention;

[0016] Figure 5 A diagram marking key dimensions of a reflective phase shifter provided in an embodiment 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 A simulated S-parameter graph of a reflective phase shifter provided in an embodiment of the present invention;

[0019] Figure 8 A graph showing the measured S-parameters of the reflective phase shifter provided in an embodiment of the present invention;

[0020] Figure 9 This is a graph showing how the phase shift degree of the reflective phase shifter provided by an embodiment of the present invention changes with the DC bias voltage. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is 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 for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may 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. Reflective phase shifters typically consist of a 3dB coupler and two reflective loads. The reflective loads, connected between the coupler's through port and coupled port, typically consist of controlled varactor diodes. By adjusting the varactor diode's bias voltage, analog phase shifting of the RF signal can be achieved. Reflective phase shifters offer advantages such as simple manufacturing processes and low cost, and are expected to address the cost and power consumption issues faced by phased array antennas.

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

[0024] Based on this, an embodiment of the present invention provides 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 cross-coupling line coupler includes two parallel coupling lines and a plurality of first capacitors C1 periodically connected in parallel between the two parallel coupling lines;

[0026] The first and second π-type reflective loads each include two varactor diodes and a microstrip transmission line connected therebetween; the first and second π-type reflective loads are connected to the coupled port and the through port of the cross-coupled line coupler in a one-to-one correspondence; the coupled port and the input port of the cross-coupled line coupler are on the same side, and the through port and the output port are on the same side; the input port and the output port are on one coupled line, and the through port and the output port are on another coupled 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 adjust the phase difference between the input port and the output port.

[0028] Specifically, the trans-coupling line coupler provided by the embodiment of the present invention can be obtained by periodically loading a plurality of parallel capacitors C1 between two parallel coupling lines.

[0029] A first π-type reflective load and a second π-type reflective load are connected to the coupled port and through port of the coupler, respectively, to form a reflective phase shifter. The first and second π-type reflective loads are each 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 varactor diode equivalent series resistance is 0Ω), the input impedance of the load port is Z IN The reflection coefficients of the and ports are:

[0031]

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

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

[0034]

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

[0036] |S 21 |=-20log|Γ|

[0037] Phase shift degree 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 changing the input impedance Z of the load port. IN , to achieve the phase difference between the control ports (i.e. ) purpose. The relationship between the DC bias voltage and the equivalent capacitance C of the four varactor diodes varies depending on the type of varactor and can be found in the varactor data sheet. Using a π-type reflective load increases the range of the reflection coefficient, thereby increasing the maximum phase shift range of the phase shifter.

[0040] Preferably, the cross-coupling line coupler further comprises at least one second capacitor C2 connected in series between the midpoints of the two parallel coupling lines, for adjusting the coupling coefficient of the coupling lines.

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

[0042] In order to minimize the size of the phase shifter and take into account the performance of the coupler and the specific processing and manufacturing, the minimum length of the cross-coupling line coupler is preferably set to 0.25λ g ,λ g is the medium wavelength at the working center frequency of the phase shifter.

[0043] In order 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 being bent at least once;

[0044] The bent transmission line is located in a 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 width of the input transmission line, the output transmission line and the length of the parallel coupling line.

[0045] Those skilled in the art will appreciate that the characteristic impedance of the input and output transmission lines is typically set to 50Ω, so the widths of the input and output transmission lines are fixed. The bent transmission lines are located within the space formed by the input and output transmission lines in the perpendicular direction. In other words, 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 coupled lines. Therefore, the length of the phase shifter is primarily determined by the length of the coupler across the coupled lines.

[0046] In order to facilitate integration with the power division network of the array antenna, minimize the size of the phase shifter and obtain good performance, preferably, the circuit formed by connecting the cross-coupled line coupler and the first and second π-type reflective loads is an axisymmetric structure.

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

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

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

[0050] Figure 1 Where 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 in the dashed area, four capacitors C1 are connected in parallel between two parallel coupled lines to form a transverse coupled line coupler. Furthermore, two capacitors C2 and a transmission line are loaded between the parallel coupled lines to adjust the coupling coefficient of the coupled lines. A π-type reflective load is 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 varactors. In this example, the transmission line is bent three times to reduce the space occupied by the phase shifter. A second inductor L2 is connected in series with each varactor diode to increase the maximum phase shift range.

[0052] A DC bias voltage is applied to the reflective phase shifter via a first inductor L1, where a DC bias voltage is input to one end of L1 and the other end is connected to a π-type reflective load transmission line. By adjusting the DC bias voltage, the capacitance of all varactor diodes is dynamically adjusted, thereby changing the reflection coefficients of the Coupled port and the Through port to achieve the purpose of regulating the phase difference between Port1 and Port2 (i.e., the input port and the output port). Due to the layout characteristics of the cross-coupling line coupler, only one DC bias voltage input is required to dynamically regulate the capacitance of the four varactor diodes. In addition, the input bias voltage can be isolated from the RF signal through the periodically loaded capacitors in the cross-coupling line coupler, eliminating the need to add DC blocking capacitors at the two ports of the phase shifter, thereby simplifying the circuit design of the bias voltage input.

[0053] The key dimensions of the phase shifter are as follows: Figure 5 As shown, the overall design layout is axially symmetrical. Figure 5In the equation ( 4L4 ), L3 is the coupler length, L4 is the length of the transmission line between the parallel capacitors; L3 = 4L4, L5 is the length of the transmission line loaded between the parallel line couplers, L6 + L7 + 2L8 is the length of the loaded transmission line, W1 is the width of the parallel coupled lines, W2 is the distance between the parallel coupled lines, W3 is the width of the transmission line loaded between the parallel line couplers, W4 is the width of the loaded transmission line, Slot is the slot opened in 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 considerations, W4 is usually set to less than W50). The length of the phase shifter is equal to the length of the coupler plus the width of the microstrip transmission lines of the first and second π-type reflective loads, that is, L3 + 2*W50.

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

[0055] The actual picture of the phase shifter is as follows Figure 6 According to actual measurements, the core design of the reflective phase shifter occupies a size of 19.3mm*8.5mm. The air wavelength λ at 2.6GHz is 115.4mm. Therefore, the size expressed in λ is: (19.3 / 115.4)*(8.5 / 115.4)λ 2 , that is 0.17*0.07λ 2 , it can be seen that the reflective phase shifter occupies a total of 0.17×0.07λ 2 PCB size.

[0056] Figure 7 The simulation S parameter curve of the phase shifter shows that the S 11 The parameters are all below -10dB, with 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 curve of the phase shifter shows that the S 11All parameters are below -10dB, demonstrating excellent 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 simulated one, primarily due to the non-ideal capacitors and inductors used in the phase shifter design. In this frequency band, the parasitic effects of capacitors and inductors affect the impedance matching of the circuit and increase transmission loss.

[0058] Figure 9 The curve of the phase shift degree of the phase shifter changing with the DC bias voltage is shown in Figure 2. The measured maximum phase shift degree is 365°, which is consistent with the simulated maximum phase shift degree of 367°.

[0059] An embodiment of the present invention provides a phased array antenna, comprising the phase shifter as described in any of the above embodiments.

[0060] It will be easily understood by those skilled in the art 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 in the scope of protection of the present invention.

Claims

1. An S-band reflective phase shifter based on a cross-coupled line coupler, characterized in that: include: A transverse coupled line coupler, a first and a second π-type reflective load, and a first inductor; The cross-coupling line coupler comprises two parallel coupling lines and a plurality of first capacitors periodically connected in parallel between the two parallel coupling lines; The first and second π-type reflective loads each include two varactor diodes and a microstrip line connected therebetween; the first and second π-type reflective loads are respectively connected to the coupled port and the through port of the cross-coupled line coupler in a one-to-one correspondence; the coupled port of the cross-coupled 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 microstrip line of the first or second π-type reflective load, and the other end is used to input a DC bias voltage to adjust the phase difference between the input port and the output port.

2. The phase shifter according to claim 1 or 2, characterized in that The length of the cross-coupled line coupler is 0.25λ g ,λ g is the medium wavelength at the working center frequency of the phase shifter.

3. The phase shifter according to claim 1 or 2, wherein: 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 being bent at least once; The bent transmission line is located in a 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 width of the input transmission line, the output transmission line and the length of the parallel coupling line.

4. The phase shifter according to claim 1, wherein The cross-coupled line coupler further includes at least one second capacitor connected in series between the midpoints of the two parallel coupled lines.

5. The phase shifter according to claim 1, wherein Each varactor diode of the first and second π-type reflective loads is connected in series with a second inductor.

6. The phase shifter according to claim 1, wherein The circuit formed by connecting the cross-coupled line coupler and the first and second π-type reflective loads is an axisymmetric structure.

7. The phase shifter according to claim 1, wherein The phase shifter is integrated on a single-layer dielectric PCB.

8. The phase shifter according to claim 7, wherein: The single-layer dielectric PCB is PTFE, RO4350B or RO5880.

9. The phase shifter according to claim 1, wherein The phase shift degree of the phase shifter The input impedance Z of the first or second π-type reflective load port IN The maximum value Z INmax , minimum value Z INmin The following relationship is satisfied: Where Z0 is the characteristic impedance of the coupled line coupler port, Z1 and θ1 are the characteristic impedance and electrical length of the microstrip transmission line in the first or second π-type reflective load, respectively, j is the imaginary unit, ω is the angular frequency, and C is the equivalent series capacitance of the four varactor diodes, which changes with the change of the DC bias voltage.

10. A phased array antenna, characterized in that: The method comprises the phase shifter according to any one of claims 1 to 9.

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