Ultra-wideband passive phase shifter and control method based on switched-capacitor dual-mode network

Abstract

An ultra-wideband passive phase shifter and control method based on a switched-capacitor dual-mode network achieves high-precision phase control across the entire 2-20 GHz frequency band through a dynamic mode switching mechanism. Phase step errors of 5.625°, 11.25°, and 22.5° are all maintained within ±0.5°, significantly improving bandwidth and accuracy compared to traditional bridged-T phase shifters (which have a phase error of ±4° and only support the 8-16 GHz frequency band). The purely passive architecture completely eliminates static power consumption, resolving the bottleneck of active solutions that rely on external power supplies. The single-stage circuit structure achieves tiny phase steps, avoiding the loss accumulation and size expansion caused by multi-stage cascading. This provides a high-performance core component for ultra-wideband systems such as phased array radar and satellite communications.

Description

Technical Field

[0001] This invention relates to the field of microwave communication technology, and in particular to an ultra-wideband passive phase shifter and control method based on a switched-capacitor dual-mode network. Background Technology

[0002] Phase shifters (PS), as core control components of modern phased array systems, play a crucial role in radar systems, satellite communications, and high-data-rate wireless communication systems. With the rapid development of next-generation communication systems, stealth communication (SC) systems, and ultra-wideband surveillance radar, the relative bandwidth (FBW) of traditional phase shifters is no longer sufficient to meet the demands of ultra-wideband applications. Therefore, phase shifters with wide operating bandwidths are receiving increasing attention from academia and industry.

[0003] Wideband phase shifters can be divided into active and passive types. Active phase shifters use vector synthesis technology to achieve high-precision phase control, but their operation requires an external DC power supply. This not only increases the overall power consumption of the system but also limits its applicability in low-power scenarios. In contrast, passive phase shifters utilize a purely passive network to achieve phase modulation, requiring no external power supply and completely eliminating static power consumption, exhibiting unique advantages. Switch-type phase shifters (STPS) are one such passive solution. However, traditional STPS employs a cascaded phase shifter architecture, requiring an independent phase shifter unit for each phase bit. Furthermore, for minute phase adjustments, a bridging T-type network is typically used, but the phase response of this network varies significantly with frequency, making it difficult to meet the requirements of ultra-wideband applications.

[0004] Technical comparison with Chinese patent CN110190830A "A dual-band miniaturized digital phase shifter";

[0005] 1. Chinese patent CN110190830A focuses on miniaturization and cost control in discrete dual-band (e.g., 1.8GHz / 3.5GHz) scenarios. Its technical path depends on the reconfigurability of the inductor coupling coefficient: by switching the state of the third switch, the magnetic field coupling strength of the first, second and third inductors is changed, thereby generating the target phase at the preset frequency point, but it does not involve broadband continuity or modal theory support.

[0006] The core objective of this application is to resolve the technical contradiction between high-precision phase control and passive integration in ultra-wideband continuous spectrum (2-20GHz). The technical approach revolves around the dynamic mode switching mechanism of switched capacitor dual-mode network (SCDMN) and combines FPGA closed-loop calibration (gradient descent algorithm to optimize bias voltage) to ensure stability across the entire temperature range.

[0007] The two are fundamentally different in their core objectives and technological fields.

[0008] 2. Chinese patent CN110190830A requires an accuracy of <±0.37° and an insertion loss of <3dB, but it does not specify the frequency range or full-band consistency. The requirement for bias voltage in its switching transistors also limits its applicability to low-power scenarios. Its miniaturized design is primarily aimed at consumer-grade dual-band communication terminals (such as mobile phones / small base stations) and cannot support ultra-wideband continuous spectrum or array systems. The goal is to meet the lightweight requirements of civilian applications through dual-band flexibility and area reduction.

[0009] This application achieves phase error ≤ ±0.5°, insertion loss ≤ 0.5dB at 20GHz, and zero static power consumption across the entire 2-20GHz frequency band. Furthermore, it ensures return loss ≤ -15dB through a tapered microstrip line, meeting the ±0.5° beam scanning accuracy requirements of large-scale phased array radar / satellite communication systems with 256 or more elements. It addresses the core bottleneck of phased arrays with military-grade broadband accuracy and passive characteristics.

[0010] The two differ fundamentally in terms of performance metrics and application scenarios.

[0011] Comparison with patent CN119010823A "An ultra-wideband phase shifter covering VHF and UHF frequency bands"

[0012] 1. Chinese patent CN119010823A addresses the miniaturization and mass production needs of phase shifters in the VHF / UHF low-frequency band (30MHz-3GHz). Its technical path relies on a dual-network structure with switch switching: switching between the "reference state" (magnetically coupled full-pass network + series compensation) and the "phase-shifted state" (parallel grounding coupled inductor + parallel compensation) by a single-pole double-throw switch. The compensation network is used to broaden the bandwidth and reduce the area, which is a structural optimization of the traditional switch network.

[0013] The core objective of this application is to solve the problem of high-precision passive phase shifting in the 2-20GHz ultra-wideband continuous spectrum. The technical approach is to achieve the dynamic switching of odd / even modes through a switched capacitor dual-mode network (SCDMN), combined with FPGA closed-loop calibration to ensure full-band accuracy, which is a dynamic reconstruction of modal resonance parameters.

[0014] The two differ fundamentally in their core objectives and technological approaches.

[0015] 2. Chinese patent CN119010823A adopts a feedback-free open-loop switching mechanism: it relies solely on a single-pole double-throw switch to switch between the "reference state network" and the "phase-shifting state network". Its phase accuracy depends entirely on the preset compensation network parameters. It has no real-time monitoring, error feedback or dynamic compensation function and belongs to static design.

[0016] This application integrates real-time S21 The phase monitoring and dynamic closed-loop calibration system, by embedding a transmission coefficient phase monitoring module, acquires the actual phase difference Δφ of the signal path in real time. r and the target value Δφ t When an error > ±0.5° is detected, the gradient descent algorithm is automatically triggered to iteratively optimize the bias voltage (±0.2V adjustment step) and correct the PIN diode junction capacitance drift until the accuracy meets the standard.

[0017] The two methods differ fundamentally in their detection approaches.

[0018] This application proposes an ultra-wideband (UWB) passive phase-shifting structure based on a switched-capacitor dual-mode network (SCDMN). By employing a switched-capacitor architecture, SCDMN achieves dynamic mode switching, effectively overcoming the limitations of narrow bandwidth and poor phase accuracy of traditional bridged T-type STPS. Summary of the Invention

[0019] To address the above problems, this invention discloses an ultrawideband passive phase shifter and its control method based on a switched-capacitor dual-mode network, thereby solving the three major technical bottlenecks of traditional phase shifters:

[0020] (1) Breaking through bandwidth limitations: Overcoming the defect of traditional bridged T-type phase shifters with a phase error of ±4° in the >8GHz frequency band, achieving a phase error ≤ ±0.5° in the 2-20GHz ultra-wide frequency band;

[0021] (2) Eliminate static power consumption: Replace the active vector synthesis scheme with a pure passive architecture to completely eliminate external power supply dependence and adapt to large-scale phased array integration;

[0022] (3) Simplified circuit structure: Small phase steps such as 5.625°, 11.25°, and 22.5° are achieved through a single-stage SCDMN unit, avoiding the accumulation of losses and size expansion caused by multi-stage cascading.

[0023] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0024] The ultrawideband passive phase shifter based on a switched-capacitor dual-mode network includes the following components: a switched-capacitor dual-mode network, a control module, and an impedance matching network.

[0025] The switched-capacitor dual-mode network consists of symmetrically distributed LC resonant units, capacitor regulation units, and PIN diode switches.

[0026] The LC resonant unit includes a parallel capacitor C. p1 and parallel capacitor C p2 ;

[0027] The capacitor regulation unit consists of a series capacitor C s1 Series capacitor C s2 Parallel capacitor C p3 And the compensation inductor L constitutes,

[0028] Parallel capacitor C p1 and parallel capacitor C p2 Connect the compensation inductor L respectively;

[0029] The PIN diode switch is controlled by Vc, thereby controlling whether the capacitor is connected to the circuit and changing the circuit's operating mode by switching between the on and off states.

[0030] When the switch is off, the capacitor controlled by the switch is not connected to the circuit, and the circuit generates a reference phase φ. o ;

[0031] When the switch is turned on, the capacitor controlled by the switch is connected to the circuit, and the corresponding capacitor C resonates with the compensating inductor L, generating the target phase φ1=φ o -Δφ, where Δφ is the phase difference, Δφ∈{5.625°,11.25°,22.5°};

[0032] The phase difference Δφ is determined by the odd mode reflection coefficient. Even mode reflection coefficient Decide;

[0033] The control module includes an FPGA controller, a bias circuit, and an S-parameter monitoring unit.

[0034] The FPGA controller generates a switch control signal, which is converted into a bias voltage Vc by a bias circuit. The bias voltage Vc changes the circuit operating mode by switching the PIN diode on or off.

[0035] The S-parameter monitoring unit calculates the transmission coefficient S in real time. 21 Phase;

[0036] The impedance matching network includes:

[0037] It adopts a gradient microstrip line structure and operates in a frequency band of 2-20GHz.

[0038] As a further improvement to the phase shifter of the present invention, the phase difference of the switched capacitor dual-mode network... By odd mode reflection coefficient Even mode reflection coefficient The following relationship is satisfied:

[0039] ;

[0040] in and Dynamic control is achieved through switch status.

[0041] As a further improvement to the phase shifter of the present invention, the odd-mode reflection coefficient Sum-mode reflection coefficient From equivalent sense resistance With equivalent capacitance Calculation yielded:

[0042] ;

[0043] Z o This is the characteristic impedance.

[0044] As a further improvement to the phase shifter of the present invention, the series capacitor C s1 The value ranges from 0.15 to 0.35 pF, and together with the coupling inductor and other capacitors, it forms the key series branch for dual-mode switching;

[0045] The series capacitor C s2 Its value ranges from 0.1 to 0.5 pF, and it participates in the impedance and phase modulation of high-frequency signal paths to help broaden the phase shift bandwidth.

[0046] The parallel capacitor C p1 The value ranges from 0.15 to 0.35 pF. It serves as the bottom parallel branch capacitor and works in conjunction with the control switch to change the equivalent capacitance value of the resonant circuit.

[0047] The parallel capacitor C p2 The value range is 0.1-0.4pF, which optimizes the low-frequency phase compensation and loop resonance characteristics, and enhances the phase shift accuracy.

[0048] The parallel capacitor C p3 The value ranges from 0.1 to 0.4 pF. In conjunction with the switching transistors on both sides controlled by Vc, the equivalent load and phase shift of the signal port are adjusted.

[0049] As a further improvement to the phase shifter of the present invention, the inductance of the single set of the compensation inductor ranges from 1.5 to 2.2 nH, and is connected in series with the capacitor C. s1 Series capacitor C s2 Parallel capacitor C p1 Parallel capacitor C p2 and parallel capacitor C p3 A multi-stage LC network is constructed, and the switching action is driven by switching capacitors to change the connection state of the corresponding capacitors, so as to achieve a phase step of 5.625°, 11.25° or 22.5° within the 2-20GHz frequency band with an error of <±0.5°.

[0050] As a further improvement to the phase shifter of the present invention, the impedance matching network satisfies:

[0051] The microstrip line width gradually changes from 0.8 mm to 0.2 mm;

[0052] The length is λ / 4, where λ is the 2GHz wavelength.

[0053] Insertion loss ≤0.5dB@20GHz.

[0054] This invention provides a phase control method for an ultrawideband passive phase shifter in a switched-capacitor dual-mode network, comprising the following steps:

[0055] (a) Receive target phase command Δφ t , Δφ t ∈{5.625°, 11.25°, 22.5°}, the control module initializes the bias voltage Vc control signals for each channel;

[0056] (b) When the reference phase needs to be output, the control module outputs the corresponding bias so that the switch driven by the bias voltage Vc is in the off state, i.e., the MOS is turned off, and the capacitors controlled by the switch are not connected to the network, thus constructing the basic phase-shifting mode.

[0057] (c) When the target phase command Δφ needs to be superimposed t When the phase is active, the control module outputs a drive voltage, causing the switch of the target capacitor branch to close, i.e., the MOS to turn on. Each capacitor controlled by the switch is connected to the LC resonant network, cooperating with the inductor group with a mutual inductance coefficient of k.

[0058] If the series capacitor C is adjusted s1 Branch switch, series capacitor C s1 Upon access, the equivalent parameters of the LC network change, the LC re-resonates, and the phase-shifting mode is switched to compensate for the target phase;

[0059] (d) Through the transmission coefficient S 21 The phase monitoring module acquires the actual phase difference Δφ of the signal path. r Verify whether |Δφ is satisfied. t - Δφ r If the accuracy requirement of ≤0.5° is not met, adjust the switching state of the capacitor branch controlled by the bias voltage Vc or the equivalent parameters of the compensation inductor until the requirement is met.

[0060] As a further improvement to the control method of the present invention, if a phase error > ±0.5° is detected in step (d), the following compensation operation is automatically performed:

[0061] Adjust the bias voltage by ±0.2V to correct the junction capacitance of the PIN diode;

[0062] The voltage value is iteratively optimized using the gradient descent algorithm until the error is ≤ ±0.5°.

[0063] As a further improvement to the control method of the present invention, the transmission coefficient S in step (d) 21 Phase calculations satisfy:

[0064] ;

[0065] in It is the phase difference of the output of the capacitor dual-mode network. For odd mode reflection coefficient and The reflection coefficient is for even modes.

[0066] As a further improvement to the control method of the present invention, the supporting system of the phase control method includes at least 8 phase shifter units, each of which has an ultra-wideband passive phase shifter based on a switched capacitor dual-mode network. Each unit is independently controlled to achieve beam scanning, and the scanning accuracy is better than ±0.5° in the 2-20GHz frequency band.

[0067] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0068] The beneficial effects of this invention are as follows: It proposes an ultra-wideband passive phase shifter based on a switched-capacitor dual-mode network, which achieves high-precision phase control across the 2-20GHz full-bandwidth through a dynamic mode switching mechanism. The errors of phase steps of 5.625°, 11.25°, and 22.5° are all kept within ±0.5°. Compared with the traditional bridged T-type phase shifter (phase error ±4° and only supports the 8-16GHz band), it significantly improves bandwidth and accuracy. The pure passive architecture completely eliminates static power consumption, solving the bottleneck of active solutions that rely on external power supplies. The single-stage circuit structure achieves small phase steps, avoiding the accumulation of losses and size expansion caused by multi-stage cascading. It provides a high-performance core component for ultra-wideband systems such as phased array radar and satellite communication. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0070] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0071] This invention provides an ultrawideband passive phase shifter based on a switched-capacitor dual-mode network, such as... Figure 1 As shown, it includes the following components: switched capacitor dual-mode network (SCDMN), control module, and impedance matching network.

[0072] The SCDMN is composed of symmetrically distributed LC resonant units, capacitor control units, and PIN diode switches; the LC resonant unit includes a parallel capacitor C.p1 and C p2 C p1 The value range is 0.15-0.35 pF, C p2 The value range is 0.1-0.4pF, and a compensation inductor L (1.5-2.2nH) is connected; the PIN diode switch changes the circuit operating mode by switching the on / off state:

[0073] When the switch is off, the capacitor controlled by the switch is not connected to the circuit, and the circuit generates a reference phase φ. o ;

[0074] When the switch is turned on, the capacitor controlled by the switch is connected to the circuit, and C and L resonate, generating the target phase φ1=φ o -Δφ(Δφ∈{5.625°,11.25°,22.5°});

[0075] The phase difference Δφ is determined by the odd mode reflection coefficient. Even mode reflection coefficient Decide;

[0076] The control module includes an FPGA controller, a bias circuit, and an S-parameter monitoring unit.

[0077] The FPGA controller generates switch control signals with a response time of <10ns;

[0078] The bias circuit converts the control signal into a 3-5V drive voltage to control the switching of the PIN diode state.

[0079] The S-parameter monitoring unit calculates the transmission coefficient S in real time. 21 Phase;

[0080] Furthermore, when a phase error > ±0.5° is detected, the bias voltage is automatically adjusted to ±0.2V to compensate for capacitor parameter drift.

[0081] The impedance matching network adopts a tapered microstrip line structure;

[0082] The microstrip line width is gradually reduced from 0.8 mm to 0.2 mm, and the length is set to 1 / 4 (λ / 4) of the 2 GHz wavelength.

[0083] Within the 2-20GHz frequency band, insertion loss ≤0.5dB and return loss ≤-15dB;

[0084] The present invention also provides a phase-shifting control method, characterized by comprising the following steps:

[0085] Step 1: Dynamic switching between dual modes;

[0086] Receive target phase command Δφ t;

[0087] When a reference phase needs to be output, the control module outputs a 0V bias voltage to turn off the PIN diode;

[0088] When Δφ needs to be generated t When there is a phase difference, the control module outputs a Vc bias voltage to turn on the PIN diode;

[0089] Furthermore, the microstrip line impedance matching parameters are dynamically adjusted according to the operating frequency.

[0090] Step 2: Phase closed-loop calibration;

[0091] Real-time data collection S 21 Phase data, calculate the actual phase difference Δφ r ;

[0092] If |Δφ t -Δφ r If the angle is greater than 0.5°, initiate the gradient descent algorithm to optimize the bias voltage;

[0093] Furthermore, a full-temperature range recalibration from -40℃ to 85℃ is triggered by a temperature sensor.

[0094] This invention discloses an ultrawideband passive phase shifter based on a switched-capacitor dual-mode network (SCDMN). Through the dual-mode switching mechanism of SCDN, it achieves phase steps of 5.625° / 11.25° / 22.5° within the 2-20GHz frequency band, with an error of <±0.5°. Compared to traditional solutions, it offers a 125% increase in bandwidth and an 8-fold improvement in phase accuracy, without requiring external power. It is suitable for 5G / 6G phased array systems.

Claims

1. An ultrawideband passive phase shifter based on a switched-capacitor dual-mode network, characterized in that, It includes the following components: a switched-capacitor dual-mode network, a control module, and an impedance matching network; The switched-capacitor dual-mode network consists of symmetrically distributed LC resonant units, capacitor regulation units, and PIN diode switches. The LC resonant unit includes a parallel capacitor C. p1、 Parallel capacitor C p2 And the compensating inductor L; The capacitor regulation unit consists of a series capacitor C s1 Series capacitor C s2 Parallel capacitor C p3 It is composed of series capacitor Cs1 and series capacitor Cs2 connected in parallel, and then connected in parallel capacitor Cp3. Parallel capacitor C p1 and parallel capacitor C p2 Connect the compensation inductor L respectively; The PIN diode switch is controlled by Vc connected to it, thereby controlling whether the capacitor connected in series with the PIN diode switch is connected to the circuit. The circuit operating mode is changed by switching the on or off state. When the switch is off, the capacitor controlled by the switch is not connected to the circuit, and the circuit generates a reference phase φ. o ; When the switch is turned on, the capacitor controlled by the switch is connected to the circuit, and the capacitor connected in series with the turned-on switch is also connected to the circuit, thus forming a resonance with the compensation inductor L, generating the target phase φ1=φ o -Δφ, where Δφ is the phase difference, Δφ∈{5.625°,11.25°,22.5°}; The phase difference Δφ is determined by the odd mode reflection coefficient. Even mode reflection coefficient Decide; The control module includes an FPGA controller, a bias circuit, and an S-parameter monitoring unit. The FPGA controller generates a switch control signal, which is converted into a bias voltage Vc by a bias circuit. The bias voltage Vc changes the circuit operating mode by switching the PIN diode on or off. The S-parameter monitoring unit calculates the transmission coefficient S in real time. 21 Phase; The impedance matching network includes: It adopts a gradient microstrip line structure and operates in a frequency band of 2-20GHz.

2. The ultra-wideband passive phase shifter based on a switched-capacitor dual-mode network according to claim 1, characterized in that, Phase difference of the switched capacitor dual-mode network By odd mode reflection coefficient Even mode reflection coefficient The following relationship is satisfied: ； in and Dynamic control is achieved through switch status.

3. The ultra-wideband passive phase shifter based on a switched-capacitor dual-mode network according to claim 2, characterized in that, The odd mode reflectance Sum-mode reflection coefficient From equivalent sense resistance With equivalent capacitive Calculation yielded: ； Z o This is the characteristic impedance.

4. The ultra-wideband passive phase shifter based on a switched-capacitor dual-mode network according to claim 1, characterized in that, The series capacitor C s1 The value ranges from 0.15 to 0.35 pF, and together with the coupling inductor and other capacitors, it forms the key series branch for dual-mode switching; The series capacitor C s2 Its value ranges from 0.1 to 0.5 pF, and it participates in the impedance and phase modulation of high-frequency signal paths to help broaden the phase shift bandwidth. The parallel capacitor C p1 The value ranges from 0.15 to 0.35 pF. It serves as the bottom parallel branch capacitor and works in conjunction with the control switch to change the equivalent capacitance value of the resonant circuit. The parallel capacitor C p2 The value range is 0.1-0.4pF, which optimizes the low-frequency phase compensation and loop resonance characteristics, and enhances the phase shift accuracy. The parallel capacitor C p3 The value ranges from 0.1 to 0.4 pF. In conjunction with the switching transistors on both sides controlled by Vc, the equivalent load and phase shift of the signal port are adjusted.

5. The ultra-wideband passive phase shifter based on a switched-capacitor dual-mode network according to claim 1, characterized in that, The inductance of the single set of the compensation inductor ranges from 1.5 to 2.2 nH, and is connected in series with the capacitor C. s1 Series capacitor C s2 Parallel capacitor C p1 Parallel capacitor C p2 and parallel capacitor C p3 A multi-stage LC network is constructed, and the switching action is driven by switching capacitors to change the connection state of the corresponding capacitors, so as to achieve a phase step of 5.625°, 11.25° or 22.5° within the 2-20GHz frequency band with an error of <±0.5°.

6. The ultrawideband passive phase shifter based on a switched-capacitor dual-mode network as described in claim 1, characterized in that, The impedance matching network satisfies: The microstrip line width gradually changes from 0.8 mm to 0.2 mm; The length is λ / 4, where λ is the 2GHz wavelength. Insertion loss ≤0.5dB@20GHz.

7. A phase control method for an ultrawideband passive phase shifter based on a switched-capacitor dual-mode network as described in any one of claims 1-6, characterized in that, The following steps are involved: (a) Receive target phase command Δφ t , Δφ t ∈{5.625°, 11.25°, 22.5°}, the control module initializes the bias voltage Vc control signals for each channel; (b) When the reference phase needs to be output, the control module outputs the corresponding bias so that the switch driven by the bias voltage Vc is in the off state, i.e., the MOS is turned off, and the capacitors controlled by the switch are not connected to the network, thus constructing the basic phase-shifting mode. (c) When the target phase command Δφ needs to be superimposed t When the phase is active, the control module outputs a drive voltage, causing the switch of the target capacitor branch to close, i.e., the MOS to conduct. Each capacitor controlled by the switch is connected to the LC resonant network, cooperating with the inductor group with a mutual inductance coefficient of k. If the series capacitor C is adjusted s1 Branch switch, series capacitor C s1 Upon access, the equivalent parameters of the LC network change, the LC re-resonates, and the phase-shifting mode is switched to compensate for the target phase; (d) Through the transmission coefficient S 21 The phase monitoring module acquires the actual phase difference Δφ of the signal path. r Verify whether |Δφ is satisfied. t - Δφ r If the accuracy requirement of ≤0.5° is not met, adjust the switching state of the capacitor branch controlled by the bias voltage Vc or the equivalent parameters of the compensation inductor until the requirement is met.

8. The phase control method based on the ultrawideband passive phase shifter based on a switched-capacitor dual-mode network as described in claim 7, characterized in that, If a phase error > ±0.5° is detected in step (d), the following compensation operation will be automatically performed: Adjust the bias voltage by ±0.2V to correct the junction capacitance of the PIN diode; The voltage value is iteratively optimized using the gradient descent algorithm until the error is ≤ ±0.5°.

9. The phase control method based on the ultrawideband passive phase shifter based on a switched-capacitor dual-mode network as described in claim 7, characterized in that, In step (d), the transmission coefficient S 21 Phase calculations satisfy: ； in It is the phase difference of the output of the capacitor dual-mode network. For odd mode reflection coefficient and is the even-mode reflection coefficient.

10. The phase control method based on the ultrawideband passive phase shifter based on a switched-capacitor dual-mode network as described in claim 7, characterized in that, The supporting system for the phase control method includes at least 8 phase shifter units, each of which has an ultra-wideband passive phase shifter based on a switched capacitor dual-mode network. Each unit is independently controlled to achieve beam scanning, and the scanning accuracy is better than ±0.5° in the 2-20GHz frequency band.

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