CN102832434B - Equal power splitter integrating band-pass filtering function - Google Patents

Abstract

The invention discloses an equal-divided power divider with integrated band-pass filtering function, which comprises an upper-layer microstrip structure, an isolation element, a middle-layer dielectric substrate and a lower-layer grounding metal plate. Each equal-division power divider integrated with band-pass filter function includes two single-frequency band-pass filter circuits and an isolation element connected between the two single-frequency band-pass filter circuits. The input impedance and output impedance of the equalized power divider with integrated band-pass filter function are the same, and the input and output impedance of each single-frequency band-pass filter circuit can be adjusted by changing the coupling strength and port position between resonators for power distribution and Make a match. Each single-frequency bandpass filter circuit consists of three quarter-wavelength resonator couplings. The invention can be used in various radio frequency front-end systems, has the functions of power distribution and frequency selection, and is smaller in volume than cascaded filter circuits and power dividers, and is beneficial to the integration and miniaturization of devices.

Description

Equal Power Divider with Integrated Bandpass Filter

technical field

The invention relates to a power divider with filter function, in particular to an equal-divided power divider with integrated band-pass filter function applicable to radio frequency front-end circuits.

Background technique

Power splitters are a fundamental part of microwave circuits and are used in many antenna arrays and balanced circuits because of their ability to separate and combine signals. The band-pass filter circuit is another indispensable part in the wireless communication system, because it can separate the required frequency band. Both elements are present in many microwave systems.

In the past few decades, there has been a lot of research on power dividers. The focus of the research is widening the frequency band, reducing the area, dual frequency response and harmonic suppression. At the same time, band-pass filter circuit is also an important research field in passive circuit design. Single-passband and multi-passband filter circuits are two different research directions. The focus of the research is to reduce the size, improve the frequency selectivity, flexibly control the operating frequency and bandwidth of multiple passbands, and increase the transmission zero point.

In many radio frequency subsystems, power dividers and filter circuits usually need to be connected together to achieve the functions of separating and filtering signals. However, all the above-mentioned studies on power dividers and filter circuits only focus on their own characteristics, and seldom consider the possibility of combining the two. Traditional systems usually use discrete devices to implement these two functions. However, this size will be large. A single device with dual functions can have two functions at the same time, which can meet the requirement of miniaturization. Dual-function devices capable of separating/combining power signals and frequency selection at the same time have been studied by some scholars. In K. J. Song, and Q. Xue, “Novel Ultra-Wideband (UWB) Multilayer Slotline Power Divider With Bandpass Response,” IEEE Microw. Wireless Compon. Lett., vol. 20, no. 1, pp. 13-15, Jan , 2010. The author completed an ultra-wideband power divider with a corresponding bandpass. Multilayer microstrip slotted line coupling is used to separate/combine signals and block unwanted frequency bands. In addition, a Wilkinson Power Divider with Bandpass Response and Harmonic Suppression is designed in P. Cheong, K. Lai, and K. Tam, “Compact Wilkinson Power Divider with Simultaneous Bandpass Response and Harmonic Suppression,” proposed in 2010 IEEE MTT-S International Microwave Symposium Digest, Snaheim, USA, 2010. In this design, interdigitated ladder impedance coupled lines are used to realize the function. In addition, mentioned in the literature X. Y. Tang, and K. Mouthaan, "Filter Integrated Wilkinson Power Dividers," Microwave and Optical Technology Letters, vol. 52, no. 12, pp. 2830-2833, Dec, 2010., Π- The Π-type transmission line can be integrated into the power divider, however, only the Π-type transmission line is used in this article, and its filtering function needs to be improved. In order to fill this gap, the present invention proposes a novel equal-division power divider with integrated band-pass filtering function.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art, and propose an equal power divider with integrated band-pass filtering function. In the present invention, a single-frequency band-pass filter circuit is used as an impedance converter to replace the traditional quarter-wavelength transmission line. Resistors, capacitors or inductors are used as isolation elements and connected to the open ends of the two single-frequency band-pass filter circuits to obtain a good isolation effect. Because of the special position of the isolation device, the proposed structure has a smaller size, which can improve the integration level of the circuit. Because the single-frequency band-pass filter circuit is integrated in the power divider, the functions of power distribution and frequency selection can be realized at the same time.

For realizing the object of the present invention, the technical scheme adopted in the present invention is as follows:

Equal power divider with integrated bandpass filtering function, including upper microstrip structure, isolation element, middle dielectric substrate and lower ground metal plate, upper microstrip structure is attached to the upper surface of the middle dielectric board, and the lower surface of the middle dielectric board It is a grounded metal; it is characterized in that: the upper microstrip structure includes two single-frequency band-pass filter circuits, the two single-frequency band-pass filter circuits have the same structure, arranged in a symmetrical structure up and down, and the two single-frequency band-pass filter circuits share one input port As the input port I/P of the equally divided power divider with integrated band-pass filter function, the output ports of the two single-frequency band-pass filter circuits are used as the first output port O/P1 and the first output port of the equalized power divider with integrated band-pass filter function. The second output port O/P2.

In the aforementioned equal-divided power divider with integrated band-pass filter function, the single-frequency band-pass filter circuit located above is composed of three quarter-wavelength resonator couplings, which are the first resonator, the second resonator and the third resonator ; wherein the first resonator is a microstrip line with an open circuit at the beginning and a grounded end formed by the first microstrip line, the second microstrip line, the third microstrip line and the fourth microstrip line connected in sequence; the second resonator is The fifth microstrip line, the sixth microstrip line, the seventh microstrip line, the eighth microstrip line, the ninth microstrip line and the tenth microstrip line connected in sequence are microstrip lines whose starting ends are grounded and whose ends are open; The third resonator is a microstrip line whose beginning end is grounded and whose end is open circuit formed by the eleventh microstrip line, the twelfth microstrip line, the thirteenth microstrip line and the fourteenth microstrip line connected in sequence; The coupling between the microstrip line and the thirteenth microstrip line, the coupling between the third microstrip line and the twelfth microstrip line, the coupling between the fourth microstrip line and the fifth microstrip line, and the coupling between one end of the fifth microstrip line and the eleventh microstrip line One end of the microstrip line is coupled; the open end of the first resonator is connected to the input port I/P, and the thirteen microstrip line of the third resonator is connected to the first output port O/P; one end of the isolation element is connected to the The open-circuit end of the upper second resonator is connected, and the other end is connected with the open-circuit end of the corresponding resonator of the lower single-frequency bandpass filter circuit.

In the aforementioned equal-division power splitter with integrated band-pass filter function, the length L of the quarter-wavelength resonator is a quarter of the wavelength λ corresponding to the resonant frequency f of the single-frequency band-pass filter circuit; wherein, L is the actual Microstrip line length.

In the equal power divider with integrated band-pass filtering function, the left and right transmission zeros of the single-band band-pass filter circuit are generated by cross-coupling between resonators.

The input impedance and output impedance of the above equalized power divider with integrated bandpass filter function are the same as the output impedance, and the input and output impedance of each single-frequency bandpass filter circuit can be changed by changing the resonator The coupling strength and port position are adjusted to match.

In the equal power divider with integrated band-pass filtering function, the isolation element is a resistor, capacitor or inductor.

Compared with the prior art, the present invention has the following advantages:

(1) The band-pass filter function is integrated in the traditional power divider, which can realize the function of power distribution and filter signal at the same time, and compared with the cascaded filter circuit and power divider, the smaller size is beneficial to the RF front-end System integration and miniaturization.

(2) The equal-divided power divider with integrated band-pass filtering function has lower insertion loss than the traditional discrete power divider and filter combination system.

Description of drawings

Figure 1 is a structural diagram of an equal-divided power divider with integrated band-pass filtering function.

Fig. 2 is a curve diagram of transmission characteristics of a single-frequency band-pass filter circuit.

Fig. 3 is a schematic structural diagram of an equal-division power divider integrated with a band-pass filtering function.

Fig. 4a is a transmission characteristic curve diagram of an equal-divided power divider integrated with a band-pass filtering function.

Figure 4b shows the output return loss and isolation factor of an equal-division power divider with integrated band-pass filtering.

concrete way

The present invention will be described in further detail below in conjunction with the accompanying drawings, but the scope of protection claimed by the present invention is not limited to the scope of the following examples.

As shown in Figure 1, the equal power divider with integrated bandpass filtering function includes an upper microstrip structure, an isolation element, a middle dielectric substrate and a lower ground metal plate. The upper microstrip structure is attached to the upper surface of the middle dielectric board, and the middle The lower surface of the layer dielectric board is grounded metal; it is characterized in that: the upper microstrip structure includes two single-frequency band-pass filter circuits, the two single-frequency band-pass filter circuits have the same structure, arranged in a symmetrical structure up and down, and the two single-frequency band-pass filter circuits The circuit shares one input port as the input port I/P of the equal-division power divider with integrated band-pass filter function, and the output ports of the two single-frequency band-pass filter circuits are used as the first output of the equal-division power divider with integrated band-pass filter function port O/P1 and a second output port O/P2. One end of the isolation element 18 is connected to the open-circuit end of the second resonator 2 located above, and the other end is connected to the open-circuit end of the corresponding resonator of the single-frequency bandpass filter circuit located below. Wherein, the isolation element 18 can be a resistor, a capacitor or an inductor.

As shown in Figure 1, the single-frequency bandpass filter circuit in the box is composed of three quarter-wavelength resonator couplings, which are the first resonator 1, the second resonator 2 and the third resonator 3; A resonator 1 is a microstrip line with an open end and a grounded end formed by the first microstrip line 4, the second microstrip line 5, the third microstrip line 6 and the fourth microstrip line 7 connected in sequence; the second resonant The device 2 is the starting end composed of the fifth microstrip line 8, the sixth microstrip line 9, the seventh microstrip line 10, the eighth microstrip line 11, the ninth microstrip line 12 and the tenth microstrip line 13 connected in sequence Grounded, open-ended microstrip line; the third resonator 3 is composed of the eleventh microstrip line 14, the twelfth microstrip line 15, the thirteenth microstrip line 16 and the fourteenth microstrip line 17 connected in sequence The start end of the microstrip line is grounded and the end is open; the second microstrip line 5 is coupled to the thirteenth microstrip line 16, the third microstrip line 6 is coupled to the twelfth microstrip line 15, and the fourth microstrip line 7 Coupled with the fifth microstrip line 8, one end of the fifth microstrip line 8 is coupled with one end of the eleventh microstrip line 14; the open end of the first resonator 1 is connected to the input port I/P, and the third resonator 13 microstrip lines 16 of 3 are connected to the first output port O/P1; the length L of the quarter-wavelength resonator is a quarter of the wavelength λ corresponding to the resonant frequency f of the single-frequency bandpass filter circuit ; Among them, L is the actual microstrip line length.

The input and output impedance of each single-frequency band-pass filter circuit can be adjusted by changing the coupling strength between resonators and the port position to achieve matching. The single-frequency bandpass filter circuit in the box shown in Figure 1 has an input impedance of 100 ohms and an output impedance of 50 ohms. Figure 2 is the magnitude simulation response of this single-frequency bandpass filter circuit. The equal split power divider with integrated band-pass filter function is composed of two single-frequency band-pass filter circuits with the same structure. These two single-frequency band-pass filter circuits are equivalent to parallel connection, so the input impedance of the parallel circuit matches 50 ohms. It is precisely because the input and output impedance of the single-frequency band-pass filter circuit can be adjusted by changing the coupling strength and port position between resonators to achieve matching, so it can be used to replace the quarter-wavelength transmission line used in traditional power dividers , to achieve the function of impedance transformation, and the matching state can be achieved only by adjusting the input and output impedance. Therefore, when the input impedance and output impedance of the equal-divided power divider integrated with band-pass filtering function are the same, the input impedance of each single-frequency band-pass filter circuit is 100 ohms, and the output impedance is 50 ohms, and between the two circuits Connect an isolation resistor in parallel to form a typical Wilkinson power divider.

Example

The structure of the equal power splitter with integrated band-pass filtering function is shown in Figure 1, and the relevant dimensions are shown in Figure 3 below. The thickness of the dielectric substrate is 0.81mm, and the relative permittivity is 3.38. The isolation element 18 connected between the single-frequency band-pass filter circuits adopts a 5.1k ohm resistor to enhance isolation. As shown in Figure 3, the length L of each resonator of the single-frequency band-pass filter circuit is a quarter of the wavelength λ corresponding to the resonant frequency f of the single-frequency band-pass filter circuit, and L is the sum of L1, L2, L3 and L4 . Design the power divider according to Figure 3 to obtain the required input and output impedance characteristics, in-band transmission characteristics and out-of-band attenuation characteristics.

Figure 4a is the simulation result of the transmission characteristics of an equal-divided power divider with integrated band-pass filtering function designed according to the above parameters; the horizontal axis in the transmission characteristic graph represents the frequency, and the vertical axis represents the transmission characteristics, where S ₁₁ represents the integrated The return loss of the equally divided power divider with band-pass filtering function, S ₂₁ represents the insertion loss from the input port I/P to the first output port O/P1, and S ₃₁ represents the insertion loss from the input port I/P to the second output port Insertion loss of O/P2; it can be seen from the simulation results that the actual test insertion loss curves S ₂₁ and S ₃₁ basically coincide, the center frequency of the passband is 2GHz, and the insertion loss S ₂₁ and S ₃₁ at the center frequency point are -4.0dB . Due to the integration of a single-frequency band-pass filter circuit, the insertion loss of the equal-divided power divider integrated with the band-pass filter function is slightly greater than that of the standard power divider. At the center frequency point, the return loss S ₁₁ of the equal split power divider with integrated bandpass filter function is -31dB, and there is a transmission zero point on both sides of the passband, which greatly improves the roll-off of the filter function in the power divider characteristic. Fig. 4b is a simulation result of output return loss S ₂₂ and isolation coefficient S ₂₃ of an equal power divider integrated with band-pass filtering function designed according to the above parameters. The output return loss S ₂₂ at the center frequency point is -15dB, and the isolation coefficient S ₂₃ between port 2 and port 3 is -22dB.

The simulation result of the embodiment shows that the device of the present invention has two functions, not only can distribute the input energy equally, but also can screen out the required frequency band.

The above descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (5)

1. The equal power divider integrating the band-pass filtering function comprises an upper-layer microstrip structure, an isolation element, a middle-layer dielectric substrate and a lower-layer grounding metal plate, wherein the upper-layer microstrip structure is attached to the upper surface of the middle-layer dielectric plate, and the lower surface of the middle-layer dielectric plate is made of grounding metal; the method is characterized in that: the upper-layer microstrip structure comprises two single-frequency band-pass filter circuits, the two single-frequency band-pass filter circuits are identical in structure and are arranged in an up-down symmetrical structure, one input port is shared by the two single-frequency band-pass filter circuits and serves as an input port (I/P) of the equal power distributor with the integrated band-pass filter function, and output ports of the two single-frequency band-pass filter circuits serve as a first output port (O/P1) and a second output port (O/P2) of the equal power distributor with the integrated band-pass filter function; the single-frequency band-pass filter circuit positioned above the single-frequency band-pass filter circuit is formed by coupling three quarter-wavelength resonators, namely a first resonator (1), a second resonator (2) and a third resonator (3); the first resonator (1) is a microstrip line with an open start end and a grounded tail end, and the microstrip line is formed by a first microstrip line (4), a second microstrip line (5), a third microstrip line (6) and a fourth microstrip line (7) which are sequentially connected; the second resonator (2) is a microstrip line which is composed of a fifth microstrip line (8), a sixth microstrip line (9), a seventh microstrip line (10), an eighth microstrip line (11), a ninth microstrip line (12) and a tenth microstrip line (13) which are connected in sequence, the starting end of the microstrip line is grounded, and the tail end of the microstrip line is open; the third resonator (3) is a microstrip line with a grounded initial end and an open-circuit tail end, and the microstrip line consists of an eleventh microstrip line (14), a twelfth microstrip line (15), a thirteenth microstrip line (16) and a fourteenth microstrip line (17) which are connected in sequence; the second microstrip line (5) is coupled with the thirteenth microstrip line (16), the third microstrip line (6) is coupled with the twelfth microstrip line (15), the fourth microstrip line (7) is coupled with the fifth microstrip line (8), and one end of the fifth microstrip line (8) is coupled with one end of the eleventh microstrip line (14); the open end of the first resonator (1) is connected with the input port (I/P), and the thirteen-microstrip line (16) of the third resonator (3) is connected with the first output port (O/P1); one end of the isolation element (18) is connected with the open end of the second resonator (2) positioned above, and the other end is connected with the open end of the corresponding resonator of the single-frequency band-pass filter circuit positioned below.

2. The integrated bandpass filtering equal-fraction power divider as claimed in claim 1, wherein the quarter-wave resonators have lengthsLIs the resonance frequency of the single-frequency band-pass filter circuitfCorresponding wavelengthλOne fourth of (a); wherein,Lis the actual microstrip line length.

3. The equal power divider with integrated band-pass filtering function according to claim 1, wherein the transmission zeros at left and right sides of the passband of the single-frequency band-pass filtering circuit are generated by cross-coupling between the resonators.

4. The integrated band-pass filter function equal-division power divider according to claim 1, wherein the input impedance and the output impedance of the integrated band-pass filter function equal-division power divider are the same, and the input and output impedances of each single-frequency band-pass filter circuit are adjusted by changing the coupling strength between the resonators and the port positions to achieve matching.

5. The integrated band-pass filter function equal power divider according to claim 1, characterized in that the isolation element (18) is a resistor, a capacitor or an inductor.