A miniaturized broadband 90° phase shifter with filtering characteristics

Abstract

The application discloses a miniaturized wideband 90-degree phase shifter with filtering characteristics and belongs to the technical field of radio frequency and microwave. The application comprises a dielectric substrate, a metal floor located on the lower surface of the dielectric substrate, a short-circuit stub loading line located on the upper surface of the dielectric substrate, two sections of microstrip delay lines, two sections of microstrip coupling lines and two radio frequency switch control devices; the phase shifter is combined with the microstrip circuit through the radio frequency switch control device, the stable phase relationship in the wideband is realized while the filtering performance is ensured by controlling the circuit parameters; the passband width and the insertion loss of the circuit in the two states can be adjusted by changing the electrical length and the respective characteristic impedance of the coupling line and the microstrip delay line, and compared with the existing filtering phase independent structure, the size is significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency microwave technology, and specifically relates to a miniaturized broadband 90° phase shifter with filtering characteristics. Background Technology

[0002] Integrating multiple passive components together, i.e., realizing the multi-functionality of a single device in the RF transceiver link, has become a trend. For example, the integration of filters and antennas, filters and couplers, and filters and phase shifters forms passive devices with filtering characteristics, which helps to miniaturize the entire RF front end.

[0003] In the 5G era, the most significant features of radio communication technology include faster information transmission and greater wireless channel capacity, which are inseparable from the development and application of technologies such as beamforming and multiple antennas. In communication systems, to reduce the number of transceiver channels while maintaining a constant number of antenna elements, hybrid beamforming is often used, with the phase shifter connected between the filter and the antenna. In this scenario, the design space reserved for the phase shifter is limited to minimize its impact on the antenna layout. Integrating the filter and phase shifter can reduce the device's footprint. However, in existing filter-phase-shifting structures, the combination of the filter and phase shifter is rather rigid, and the phase shifting implementation often uses a two-way independent switching linear structure. Even if this structure is used in all channels of the transceiver, the circuit size will still be large. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a miniaturized broadband 90° phase shifter with filtering characteristics, which can achieve good filtering and phase shifting performance.

[0005] The technical problem addressed by this invention is solved as follows:

[0006] A miniaturized broadband 90° phase shifter with filtering characteristics includes a short-circuit stub loading line TL1, two microstrip delay lines, two microstrip coupling lines, two radio frequency switch controllers, a metal ground plane, and a dielectric substrate; the metal ground plane is located on the lower surface of the dielectric substrate, and the short-circuit stub loading line TL1, the two microstrip delay lines, the two microstrip coupling lines, and the two radio frequency switch controllers are located on the upper surface of the dielectric substrate.

[0007] The input terminal of the first microstrip coupling line CL1 serves as the circuit input terminal, and its coupling terminal is connected to one end of the first microstrip delay line TL2 and the positive terminal of the second RF switch controller Switch2, respectively. The other end of the first microstrip delay line TL2 is connected to the positive terminal of the first RF switch controller Switch1 and one end of the second microstrip delay line TL3, respectively. The negative terminal of the first RF switch controller Switch1 is connected to one end of the short-circuit stub loading line TL1, and the other end of the short-circuit stub loading line TL1 is connected to the metal ground plane through a metallized via. The negative terminal of the second RF switch controller Switch2 is connected to the other end of the second microstrip delay line TL3 and the input terminal of the second microstrip coupling line CL2, and the coupling terminal of the second microstrip coupling line CL2 serves as the circuit output terminal.

[0008] Furthermore, the first microstrip coupling line CL1 and the second microstrip coupling line CL2 have the same structure and are placed symmetrically. They consist of two mutually coupled microstrip lines with open-circuit ends and isolation sections, forming open-circuit microstrip coupling lines.

[0009] Furthermore, the characteristic impedances of the first microstrip delay line TL2 and the second microstrip delay line TL3 are equal, and the characteristic impedance of the short-circuit stub loading line TL1 is half of the characteristic impedances of the first microstrip delay line TL2 / the second microstrip delay line TL3, where / represents or; the electrical lengths of the first microstrip delay line TL2, the second microstrip delay line TL3, and the short-circuit stub loading line TL1 are equal, and the electrical lengths of the first microstrip coupling line CL1 and the second microstrip coupling line CL2 are twice the electrical lengths of the first microstrip delay line TL2 / the second microstrip delay line TL3 / the short-circuit stub loading line TL1; the electrical lengths of the first microstrip coupling line CL1 and the second microstrip coupling line CL2 are one-quarter wavelengths corresponding to the center frequency.

[0010] Furthermore, the simultaneous cutoff of the first RF switch controller Switch1 and the second RF switch controller Switch2 corresponds to circuit state 1; after the RF signal is input from the circuit input terminal to the phase shifter circuit, it flows sequentially through the first microstrip coupling line CL1, the first microstrip delay line TL2, the second microstrip delay line TL3, and the second microstrip coupling line CL2 before being output from the circuit output terminal; in circuit state 1, the upper half of the microstrip lines of the first microstrip delay line TL2, the second microstrip delay line TL3, the first microstrip coupling line CL1, and the first microstrip coupling line CL2 are connected in series to form the first SIR structure. The phase shifter circuit structure is equivalent to being composed of the coupled feed structure located at the circuit input and output terminals and the first SIR structure, forming a broadband filter circuit based on a multimode resonator.

[0011] The first RF switch controller Switch1 and the second RF switch controller Switch2 are simultaneously turned on, corresponding to circuit state 2. The short-circuited stub loading line TL1, the first RF switch controller Switch1, the second RF switch controller Switch2, the first microstrip delay line TL2, and the second microstrip delay line TL3 form a T-shaped loop. After the RF signal is input from the circuit input terminal to the phase shifter circuit, it flows sequentially through the first microstrip coupling line CL1, the T-shaped loop, and the second microstrip coupling line CL2, and is output through the circuit output terminal. In circuit state 2, the T-shaped loop is equivalent to a new short-circuited stub loading line. Compared with the original short-circuited stub loading line TL1, its characteristic impedance is equal to that of TL1, and its electrical length is twice that of TL1. It is connected in parallel in the middle of the upper half of the microstrip lines of the first microstrip coupling line CL1 and the first microstrip coupling line CL2 and forms a second SIR structure with them. The phase shifter circuit structure is equivalent to a combination of the coupled feed structure and the second SIR structure located at the circuit input and output terminals, forming a broadband filter circuit based on a multimode resonator.

[0012] Furthermore, analyzing the phase frequency response of the phase shifter, the difference in the inserted phase shift between the two circuit states is the phase shift amount. for:

[0013]

[0014] Where i is the imaginary part symbol, Z1 and θ1 represent the characteristic impedance and electrical length of the short-circuit stub loading line TL1, respectively, and Z2 and θ2 represent the characteristic impedance and electrical length of the first microstrip delay line TL2, respectively.

[0015] Given Z1 = Z2 / 2 and θ1 = θ2, then:

[0016]

[0017] Where f is the frequency, f0 is the center frequency of the phase shifter, and n is an integer ≥ 0.

[0018] Furthermore, for circuit state 1, analyzing the amplitude-frequency response of the phase shifter, the fixed transmission zeros are located at 0 and 2f0. By using the Chebyshev function with equal ripple for synthesis, we can obtain that its filter order is 4th order. Its ripple coefficient and cutoff frequency in the passband are jointly determined by the characteristic impedance of the microstrip delay line and the odd-even mode impedance of the microstrip coupling line.

[0019] For circuit state 2, analyzing the amplitude-frequency response of the phase shifter, the fixed transmission zeros are located at 0 and 2f0. By synthesizing the Chebyshev function with equal ripple, we can obtain that its filter order is 5th. Its ripple coefficient and cutoff frequency in the passband are also determined by the characteristic impedance of the microstrip delay line and the odd-even mode impedance of the microstrip coupling line.

[0020] The beneficial effects of this invention are:

[0021] The phase shifter described in this invention combines a radio frequency switch control device with a microstrip circuit. By controlling the circuit parameters, it achieves a stable phase relationship within a wide bandwidth while ensuring filtering performance. By changing the electrical length and characteristic impedance of the coupling line and the microstrip delay line, the passband width and insertion loss of the circuit can be adjusted in two states. Moreover, compared with the existing independent filter phase shifting structure, the size is significantly reduced. Attached Figure Description

[0022] Figure 1 This is a circuit topology diagram of the phase shifter described in this invention;

[0023] Figure 2 The amplitude-frequency response curves of the phase shifter of the present invention in circuit state 1 and circuit state 2 are shown, where (a) is circuit state 1 and (b) is circuit state 2.

[0024] Figure 3 The phase shift curves of the phase shifter described in this invention in circuit state 1 and circuit state 2 are shown.

[0025] Figure 4 This is a circuit implementation diagram of the phase shifter described in the embodiment;

[0026] Figure 5 The amplitude-frequency response curves of the phase shifter described in the embodiment are shown in circuit state 1 and circuit state 2, where (a) is circuit state 1 and (b) is circuit state 2.

[0027] Figure 6 The phase shift curves of the phase shifter described in the embodiment are shown in circuit state 1 and circuit state 2. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] This embodiment provides a miniaturized broadband 90° phase shifter with filtering characteristics, and its circuit topology diagram is as follows. Figure 1 As shown, it includes a short-circuit stub loading line TL1, two microstrip delay lines, two microstrip coupling lines, two radio frequency switch controllers, a metal ground plane, and a dielectric substrate; the metal ground plane is located on the lower surface of the dielectric substrate, and the short-circuit stub loading line TL1, two microstrip delay lines, two microstrip coupling lines, and two radio frequency switch controllers are located on the upper surface of the dielectric substrate.

[0030] The input terminal of the first microstrip coupling line CL1 serves as the circuit input terminal, and its coupling terminal is connected to one end of the first microstrip delay line TL2 and the positive terminal of the second RF switch controller Switch2, respectively. The other end of the first microstrip delay line TL2 is connected to the positive terminal of the first RF switch controller Switch1 and one end of the second microstrip delay line TL3, respectively. The negative terminal of the first RF switch controller Switch1 is connected to one end of the short-circuit stub loading line TL1, and the other end of the short-circuit stub loading line TL1 is connected to the metal ground plane through a metallized via. The negative terminal of the second RF switch controller Switch2 is connected to the other end of the second microstrip delay line TL3 and the input terminal of the second microstrip coupling line CL2, and the coupling terminal of the second microstrip coupling line CL2 serves as the circuit output terminal.

[0031] Given Z1 = 22.45 ohms, the odd-mode impedance Z of the microstrip coupled line... o = 42.1 ohms, even-mode impedance Z of the microstrip coupled line e =140.2 ohms, θ1=θ2=45°, the RF switch is an ideal model, and the amplitude-frequency response curves of circuit state 1 and circuit state 2 are as follows. Figure 2 As shown, the phase shift curve is as follows Figure 3 As shown. The results show that under circuit state 1, the return loss is better than 23dB in the 2.05-3.95GHz frequency band, and under circuit state 2, the return loss is better than 16dB in the 1.62-4.38GHz frequency band, with an insertion loss of less than 0.1dB; at 90° phase shift, the bandwidth of phase imbalance ±4.2° is 1.64-4.36GHz (relative bandwidth 90.6%).

[0032] In this embodiment, the center frequency of the circuit is set to 3GHz, and the RF switch is a Skyworks SMP1340-079LF PIN diode. The circuit implementation diagram is shown below. Figure 4 As shown. Two RF switches are connected with a common anode and controlled by the control voltage Vc at port P3. Substituting the PIN diode circuit model into the simulation circuit, at the center frequency, the insertion loss of the PIN diode under a forward current of 10mA is less than 0.1dB, the forward conduction resistance is approximately 1Ω, and there is a phase shift of approximately -7.2° to the signal. Connecting the PIN diode switch in series in the circuit, the isolation under -10V reverse bias is -11dB, and the reverse bias capacitance is approximately 0.3pF.

[0033] In this embodiment, the dielectric substrate has a relative permittivity of 3.66 and a thickness of 20 mil.

[0034] The short-circuit stub loading line TL1 is implemented at one end of the microstrip line through a circular metal via with a radius of 0.2 mm to the metal ground plane. The impedance value of the short-circuit stub loading line TL1 is half the impedance value of the first microstrip delay line TL2 / second microstrip delay line TL3. Therefore, the linewidth w1 of the short-circuit stub loading line TL1 is greater than the linewidth w2 of the first microstrip delay line TL2 / second microstrip delay line TL3, w1 = 1.24 mm, w2 = 0.97 mm. According to theoretical derivation, the line length l1 of the short-circuit stub loading line TL1 is approximately equal to the line length l2 of the first microstrip delay line TL2 / second microstrip delay line TL3. However, due to the phase shift of the signal when the PIN diode is turned on, l1 is less than l2, l1 = 6.1 mm, l2 = 7.1 mm. The coupling gap s of the microstrip coupling line is 0.1mm, the width wc of a single microstrip line in the coupling line is 0.13mm, and the line length lc = 17mm, which is close to the 1 / 4 wavelength corresponding to the center frequency of 3GHz. The DC blocking capacitor C2 has a capacitance of 8pF, and P3 is the DC feed port. The control terminal feed line length L1 of S1 and the control terminal feed line length L2 of S2 are high-impedance lines corresponding to the 1 / 4 wavelength of the center frequency of 3GHz, with a line width of 0.1mm and a length of 23mm. C1 is a bypass capacitor with a capacitance of 8pF. Ports P1 and P2 are the RF input and output. The overall circuit size is approximately 24mm x 16.5mm.

[0035] In the circuit, the simultaneous cutoff of radio frequency switches S1 and S2 corresponds to circuit state 1, and their simultaneous conduction corresponds to circuit state 2. Figure 5 This is the amplitude-frequency response curve of the phase shifter described in this embodiment. Figure 6 This is the phase shift curve of the phase shifter described in this embodiment. From... Figure 5 and Figure 6 It can be seen that the amplitude-frequency response curves in both circuit states exhibit a pair of out-of-band transmission zeros at the same location. The bandwidths in circuit state 1 and circuit state 2 are 2.28-3.62GHz and 2.14-3.82GHz, respectively. The corresponding maximum insertion losses are 0.74dB and 0.55dB, and the in-band insertion loss imbalances are 0.49dB and 0.32dB, respectively. The corresponding in-band return losses are better than 8.8dB and 10.7dB. Figure 6 The results show that with a 90° phase shift, the phase shift bandwidth with a phase shift error of ±5° ranges from 2.67 GHz to 3.5 GHz. In summary, the phase shifter operates with a bandwidth of 2.67-3.5 GHz, an in-band phase shift error of less than 5°, and an in-band insertion loss of less than 0.56 dB.

Claims

1. A miniaturized broadband 90° phase shifter with filtering characteristics, characterized in that, It includes a short-circuit stub loading line TL1, two microstrip delay lines, two microstrip coupling lines, two radio frequency switch controllers, a metal ground plane, and a dielectric substrate; the metal ground plane is located on the lower surface of the dielectric substrate, and the short-circuit stub loading line TL1, two microstrip delay lines, two microstrip coupling lines, and two radio frequency switch controllers are located on the upper surface of the dielectric substrate. The input terminal of the first microstrip coupling line CL1 serves as the circuit input terminal, and its coupling terminal is connected to one end of the first microstrip delay line TL2 and the positive terminal of the second RF switch controller Switch2, respectively. The other end of the first microstrip delay line TL2 is connected to the positive terminal of the first RF switch controller Switch1 and one end of the second microstrip delay line TL3, respectively. The negative terminal of the first RF switch controller Switch1 is connected to one end of the short-circuit stub loading line TL1, and the other end of the short-circuit stub loading line TL1 is connected to the metal ground plane through a metallized via. The negative terminal of the second RF switch controller Switch2 is connected to the other end of the second microstrip delay line TL3 and the input terminal of the second microstrip coupling line CL2, and the coupling terminal of the second microstrip coupling line CL2 serves as the circuit output terminal.

2. The miniaturized broadband 90° phase shifter with filtering characteristics according to claim 1, characterized in that, The first microstrip coupling line CL1 and the second microstrip coupling line CL2 have the same structure and are placed symmetrically. They consist of two microstrip lines that are coupled to each other, with the through end and the isolation section open-circuited, forming a terminal open-circuit microstrip coupling line.

3. The miniaturized broadband 90° phase shifter with filtering characteristics according to claim 1, characterized in that, The characteristic impedances of the first microstrip delay line TL2 and the second microstrip delay line TL3 are equal. The characteristic impedance of the short-circuit stub loading line TL1 is half of the characteristic impedances of the first microstrip delay line TL2 / the second microstrip delay line TL3, where / represents or. The electrical lengths of the first microstrip delay line TL2, the second microstrip delay line TL3, and the short-circuit stub loading line TL1 are equal. The electrical lengths of the first microstrip coupling line CL1 and the second microstrip coupling line CL2 are twice the electrical lengths of the first microstrip delay line TL2 / the second microstrip delay line TL3 / the short-circuit stub loading line TL1. The electrical lengths of the first microstrip coupling line CL1 and the second microstrip coupling line CL2 are one-quarter wavelengths corresponding to the center frequency.

4. The miniaturized broadband 90° phase shifter with filtering characteristics according to claim 1, characterized in that, The simultaneous cutoff of the first RF switch controller Switch1 and the second RF switch controller Switch2 corresponds to circuit state 1. After the RF signal is input to the phase shifter circuit from the circuit input terminal, it flows sequentially through the first microstrip coupling line CL1, the first microstrip delay line TL2, the second microstrip delay line TL3, and the second microstrip coupling line CL2 before being output from the circuit output terminal. In circuit state 1, the upper half of the microstrip lines of the first microstrip delay line TL2, the second microstrip delay line TL3, the first microstrip coupling line CL1, and the second microstrip coupling line CL2 are connected in series to form the first SIR structure. The phase shifter circuit structure is equivalent to the combination of the coupled feed structure located at the circuit input and output terminals and the first SIR structure, forming a broadband filter circuit based on a multimode resonator. The simultaneous conduction of the first RF switch controller Switch1 and the second RF switch controller Switch2 corresponds to circuit state 2. The short-circuited stub loading line TL1, the first RF switch controller Switch1, the second RF switch controller Switch2, the first microstrip delay line TL2, and the second microstrip delay line TL3 form a T-shaped loop. The RF signal, after being input to the phase shifter circuit from the circuit input terminal, flows sequentially through the first microstrip coupling line CL1, the T-shaped loop, and the second microstrip coupling line CL2 before being output from the circuit output terminal. In circuit state 2, the T-shaped loop is equivalent to a new short-circuited stub loading line, compared to the original short-circuited stub loading line TL1. Its characteristic impedance is equal to that of TL1, and its electrical length is twice that of TL1. It is connected in parallel in the middle of the upper half of the microstrip lines of the first microstrip coupling line CL1 and the second microstrip coupling line CL2 to form a second SIR structure. The phase shifter circuit structure is equivalent to the combination of the coupled feed structure and the second SIR structure located at the input and output terminals of the circuit, forming a broadband filter circuit based on a multimode resonator.

5. The miniaturized broadband 90° phase shifter with filtering characteristics according to claim 4, characterized in that, Analyzing the phase frequency response of the phase shifter, the difference in the inserted phase shift between the two circuit states is the phase shift amount. for: Where i is the imaginary part symbol, Z1 and θ1 represent the characteristic impedance and electrical length of the short-circuit stub loading line TL1, respectively, and Z2 and θ2 represent the characteristic impedance and electrical length of the first microstrip delay line TL2, respectively. Given Z1 = Z2 / 2 and θ1 = θ2, then: Where f is the frequency, f0 is the center frequency of the phase shifter, and n is an integer ≥ 0.

6. The miniaturized broadband 90° phase shifter with filtering characteristics according to claim 4, characterized in that, For circuit state 1, analyzing the amplitude-frequency response of the phase shifter, the fixed transmission zeros are located at 0 and 2f0. By using the Chebyshev function with equal ripple for synthesis, we can obtain that its filter order is 4th. Its ripple coefficient and cutoff frequency in the passband are jointly determined by the characteristic impedance of the microstrip delay line and the odd and even mode impedance of the microstrip coupling line. For circuit state 2, analyzing the amplitude-frequency response of the phase shifter, the fixed transmission zeros are located at 0 and 2f0. By synthesizing the Chebyshev function with equal ripple, we can obtain that its filter order is 5th. Its ripple coefficient and cutoff frequency in the passband are also determined by the characteristic impedance of the microstrip delay line and the odd-even mode impedance of the microstrip coupling line.

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