Absorbing microstrip switched-slot antenna and filtering absorbing method thereof

Abstract

This invention discloses an absorptive microstrip slotted antenna and its filtering and absorption method. The microstrip slotted antenna includes a microstrip feed line, a slotted ground plane, a bandpass filter absorption circuit, and a dielectric substrate. The microstrip feed line is mounted on the upper surface of the dielectric substrate, and the slotted ground plane is mounted on the lower surface of the dielectric substrate. The bandpass filter absorption circuit is disposed on the microstrip feed line and includes a resistor and a resonant circuit connected in parallel. The resonant circuit includes a capacitor and an inductor connected in series. It also includes a feed connector connected to the microstrip feed line. This application achieves anti-reflection performance by using a microstrip line structure to excite the slotted line and connecting a bandpass filter absorption circuit in series at the optimal loading position of the microstrip feed line. This invention has a wide anti-reflection bandwidth, extremely high structural integration, and good antenna radiation performance, making it well-suited for application in the field of wireless communication systems.

Description

Technical Field

[0001] This invention relates to the field of non-reflective / absorbent antenna technology, and in particular to an absorptive microstrip slot antenna with a wide quasi-non-reflective bandwidth, high integration, and lumped element loading, and its filtering and absorption method. Background Technology

[0002] Non-reflective or absorbing devices play an increasingly important role in modern high-performance communication systems and highly integrated RF terminals. By effectively absorbing out-of-band signals, these devices can suppress signal crosstalk and minimize multiple reflections between RF modules, thereby improving the sensitivity and stability of the entire RF system. Therefore, they help reduce reliance on traditional components such as isolators, high-order multiplexers, and attenuators, thus achieving lower system cost, miniaturization, and higher performance. Among various non-reflective components, non-reflective filters and antennas are the two most representative and widely studied types.

[0003] In the research of reflectionless filters, researchers have proposed various basic topologies and general design schemes to achieve broadband matching and out-of-band absorption. Representative methods include even-mode and odd-mode subcircuit compensation, complementary duplexer networks, and balanced circuit-based topologies. These general theories and their extended configurations have been widely applied to the design of reflectionless filters, power dividers, couplers, and antennas.

[0004] Meanwhile, research on reflection-free antennas is still in its early stages, with most existing designs implemented using complementary duplexer networks. Based on this general structure, various types of reflection-free antennas have been realized, including patch antennas, Yagi antennas, slot antennas, ultra-wideband (UWB) monopole antennas, and waveguide cavity slot antennas.

[0005] Other methods achieve reflection-free operation by cascading a reflection-free filter with the antenna. For example, reflection-free conical slot antennas and quasi-Yagi antennas have been realized by integrating a reflection-free filter into the antenna feed structure, while providing excellent absorption and filtering performance. Coupler-based structures have also been explored, in which orthogonal couplers are used to connect the radiating elements to achieve reflection-free and circularly polarized characteristics.

[0006] Therefore, the existing technology has the following drawbacks:

[0007] Designs implemented using terminal complementary duplexer networks generally require additional absorbing branches, which inevitably increases the complexity of the antenna structure and may reduce its radiation performance.

[0008] The quasi-reflection-free bandwidth of designs implemented by cascading reflection-free filters with antennas is generally limited to the vicinity of the antenna's operating frequency band. Furthermore, cascading and coupler-based configurations typically lead to increased antenna size and complexity. Overall, existing reflection-free antenna designs still have significant room for improvement in terms of antenna integration and reflection-free bandwidth, prompting the development of new topologies and more efficient implementation methods.

[0009] A search revealed Chinese invention patent CN120262003A, which discloses a broadband, reflection-free filter antenna. The antenna comprises a stopband energy absorption structure, high- and low-impedance microstrip lines, and a Yagi-like radiator connected in sequence. The Yagi-like radiator consists of a pair of dipole arms and two pairs of bilateral parallel parasitic patches. The stopband energy absorption structure consists of two microstrip band-stop filters, two grounded patch resistors, a folded phase line, and an input microstrip feed line. Each of the two microstrip band-stop filters is connected to a grounded patch resistor, and the two microstrip band-stop filters are connected via the folded phase line. This antenna structure is highly compact, achieving integrated design of the filter and antenna, as well as an ultra-wide reflection-free bandwidth.

[0010] The technical comparison between this application and the aforementioned patent is as follows:

[0011] 1. The mechanisms for achieving non-reflection are different;

[0012] The patented broadband non-reflective filter antenna relies on multiple distributed band-stop filters connected in parallel to form an absorption network, while this application achieves reflection suppression through a lumped element absorption circuit. The two are fundamentally different in their implementation mechanism and circuit topology.

[0013] 2. The antenna radiation structures are different;

[0014] The patent describes a broadband, non-reflective filter antenna that uses a Yagi-like structure and parasitic structures to introduce a radiation null point. This application uses a microstrip slotted radiation structure, which does not rely on parasitic radiators, and the structural forms are significantly different.

[0015] 3. Different levels of structural integration;

[0016] The patented broadband non-reflective filter antenna requires the introduction of multiple distributed filters and phase structures, resulting in high overall complexity; this application has a simple structure, high integration, and is more suitable for modular integration.

[0017] Therefore, this application differs from the broadband non-reflective filter antenna in terms of its non-reflective implementation method, radiation structure form, and system integration path, and the two have significant technical differences. Summary of the Invention

[0018] To address the aforementioned technical problems, this invention proposes an absorptive microstrip slot antenna and its filtering and absorption method, which achieves excellent non-reflective characteristics and a high radiation efficiency of over 80%.

[0019] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0020] An absorptive microstrip slotted antenna includes a microstrip feed line, a slotted ground plane, a bandpass filter absorption circuit, and a dielectric substrate. The microstrip feed line is mounted on the upper surface of the dielectric substrate, and the slotted ground plane is mounted on the lower surface of the dielectric substrate. The bandpass filter absorption circuit is disposed on the microstrip feed line, and its input and output terminals are directly connected to the microstrip feed line, respectively. The bandpass filter absorption circuit includes a resistor and a resonant circuit connected in parallel. The resonant circuit includes a capacitor and an inductor connected in series.

[0021] It also includes a power supply connector, which connects to the microstrip feeder to excite the microstrip feeder.

[0022] Preferably, the microstrip feed line is mounted at the center of the dielectric substrate.

[0023] Preferably, the bandpass filter absorption circuit is connected in series at the optimal loading position of the microstrip feeder.

[0024] Preferably, the capacitor, inductor, and resistor are all provided with a protective shell.

[0025] Preferably, the dielectric substrate has a thickness of 0.813 mm, a relative permittivity of 3.55, and a loss tangent of 0.0027.

[0026] Preferably, the capacitor is a Murata GJM03 capacitor, the inductor is a WireTech 0402HP inductor, and the resistor is a 0402 packaged precision thin film 50Ω resistor.

[0027] A filtering and absorption method for an absorptive microstrip slot antenna includes the following steps:

[0028] The microstrip slotted antenna operates at the resonant frequency f0, which is also the resonant frequency of the resonant circuit. At the antenna's operating frequency f0, the resonant circuit in the bandpass filter absorption circuit is in a short-circuit state, and the resistor will not play a role. Therefore, the signal near the antenna's operating frequency f0 will flow through the bandpass filter absorption circuit without loss and be efficiently radiated by the microstrip slotted antenna.

[0029] When the microstrip slotted antenna is far from the operating frequency f0, the impedance of the inductor or capacitor in the bandpass filter absorption circuit is higher than a preset threshold. At this time, the impedance of the bandpass filter absorption circuit is provided by the resistor, and all out-of-band energy flows into the resistor. Signals within the operating frequency band of the microstrip slotted antenna can pass through the bandpass filter absorption circuit without loss and flow to the microstrip slotted antenna for radiation, while out-of-band signals are confined in the bandpass filter absorption circuit and absorbed by the resistor, thus forming a non-reflective characteristic inside and outside the band.

[0030] This application proposes an absorptive microstrip slotted antenna, comprising a microstrip feed line, a slotted ground plane, a bandpass filter absorption circuit, and a dielectric substrate. The microstrip feed line is mounted on the upper surface of the dielectric substrate, and the slotted ground plane is mounted on the lower surface of the dielectric substrate. The bandpass filter absorption circuit is disposed on the microstrip feed line, and its input and output terminals are directly connected to the microstrip feed line to achieve anti-reflection characteristics. The bandpass filter absorption circuit includes a resistor and a resonant circuit connected in parallel. The resonant circuit includes a capacitor and an inductor connected in series. A feed connector is connected to the microstrip feed line. The entire circuit uses the feed connector to excite the microstrip feed line and excites the slotted ground plane near the open-circuit end of the microstrip feed line. This application achieves anti-reflection performance by using a microstrip line structure to excite the slotted line and connecting a bandpass filter absorption circuit in series at the optimal loading position of the microstrip feed line.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] The novel topology employed in this invention is a first-order lumped anti-reflection network without additional absorbing branches. This network has a simple structure, achieves good anti-reflection characteristics over a very wide frequency range, and maintains good radiation performance.

[0033] The novel topology employed in this invention is a new first-order lumped non-reflective network without additional absorbing branches. The lumped element loading allows the antenna to almost completely retain its original structural characteristics, achieving process integration.

[0034] This invention achieves excellent non-reflective properties while also realizing a high radiation efficiency of over 80%. This design successfully balances high performance and structural simplicity, breaking through the previous limitation that it was difficult to achieve both simultaneously, and has outstanding practical value and prospects for widespread application. Attached Figure Description

[0035] Figure 1 This is a three-dimensional structural diagram of the present invention.

[0036] Figure 2 This is a top view of the present invention.

[0037] Figure 3This is a three-dimensional structural schematic diagram of the bandpass filter absorption circuit in this invention.

[0038] Figure 4 This is the circuit schematic diagram of the present invention.

[0039] Figure 5 This is a reflection coefficient curve of the simulation and testing process of the present invention.

[0040] Figure 6 This is a graph showing the gain and overall efficiency of the processing test results of this invention.

[0041] Figure 7 This is the E-plane radiation pattern of the present invention at the center frequency point.

[0042] Figure 8 This is the H-plane radiation pattern of the present invention at the center frequency point.

[0043] List of reference numerals in the attached diagram:

[0044] 1. Microstrip feeder; 2. Slotted ground plane; 3. Bandpass filter absorption circuit; 4. Power supply connector; 5. Dielectric substrate; 6. Capacitor; 7. Inductor; 8. Resistor. Detailed Implementation

[0045] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0046] like Figure 1-3 As shown, the present invention proposes an absorptive microstrip slotted antenna, comprising a microstrip feed line 1, a slotted ground plane 2, a bandpass filter absorption circuit 3, and a dielectric substrate 5. The microstrip feed line 1 is mounted on the upper surface of the dielectric substrate 5, and the slotted ground plane 2 is mounted on the lower surface of the dielectric substrate 5. The bandpass filter absorption circuit 3 is disposed on the microstrip feed line 1, and its input and output terminals are directly connected to the microstrip feed line 1, respectively. The bandpass filter absorption circuit 3 includes a resistor 8 and a resonant circuit, which are connected in parallel. The resonant circuit includes a capacitor 6 and an inductor 7, which are connected in series.

[0047] It also includes a power supply connector 4, which is connected to the microstrip feed line 1 to excite the microstrip feed line 1.

[0048] The microstrip feed line 1 is mounted at the center of the dielectric substrate 5. The bandpass filter absorption circuit 3 is connected in series at the optimal loading position of the microstrip feed line 1.

[0049] This application proposes an absorptive microstrip slotted antenna, comprising a microstrip feed line 1, a slotted ground plane 2, a bandpass filter absorption circuit 3, and a dielectric substrate 5. The microstrip feed line 1 is mounted on the upper surface of the dielectric substrate 5, and the slotted ground plane 2 is mounted on the lower surface of the dielectric substrate 5. The bandpass filter absorption circuit 3 is disposed on the microstrip feed line 1, and its input and output terminals are directly connected to the microstrip feed line 1 to achieve anti-reflection characteristics. The bandpass filter absorption circuit 3 includes a resistor 8 and a resonant circuit connected in parallel. The resonant circuit includes a capacitor 6 and an inductor 7 connected in series. A feed connector 4 is connected to the microstrip feed line 1. The entire circuit uses the feed connector 4 to excite the microstrip feed line 1, and excites the slotted ground plane 2 near the open-circuit end of the microstrip feed line 1. This application achieves anti-reflection performance by using a microstrip line structure to excite the slotted line and connecting a bandpass filter absorption circuit 3 in series at the optimal loading position of the microstrip feed line 1.

[0050] This invention also proposes a filtering and absorption method for an absorptive microstrip slot antenna, comprising the following steps:

[0051] The microstrip slotted antenna operates at the resonant frequency f0. At the same time, the resonant frequency of the resonant circuit is also f0. As a result, at the antenna operating frequency f0, the resonant circuit in the bandpass filter absorption circuit 3 is in a short-circuit state, and the resistor 8 will not play a role. Therefore, the signal near the antenna operating frequency f0 will flow through the bandpass filter absorption circuit 3 without loss and be efficiently radiated by the microstrip slotted antenna.

[0052] When the microstrip slotted antenna is far from the operating frequency f0, the impedance of the inductor 7 or capacitor 6 in the bandpass filter absorption circuit 3 is higher than the preset threshold, i.e., it presents a high impedance state. At this time, the impedance of the bandpass filter absorption circuit 3 is played by the low impedance resistor 8. All out-of-band energy flows into the resistor 8 and is absorbed by it. Based on the above description, the signal within the operating frequency band of the microstrip slotted antenna can pass through the bandpass filter absorption circuit 3 without loss and flow to the microstrip slotted antenna for radiation, while the out-of-band signal is confined in the bandpass filter absorption circuit 3 and absorbed by the resistor 8, thus forming a non-reflection characteristic inside and outside the band.

[0053] Therefore, within the operating frequency band: the bandpass filter absorption circuit 3 is in a short-circuit state, and the signal can flow into the subsequent microstrip slot antenna without loss, achieving effective in-band radiation;

[0054] Outside the operating frequency band: out-of-band signals are absorbed by resistor 8 in bandpass filter absorption circuit 3. In this way, neither in-band nor out-of-band energy is reflected back to the input port, and reflection-free characteristics can be achieved over a fairly wide frequency band.

[0055] The capacitor 6, inductor 7, and resistor 8 are all provided with protective shells to protect them from damage.

[0056] Taking into account both antenna cost and requirements, this invention selects Rogers RO4003 with a thickness of 0.813 mm for the dielectric substrate 5, which has a relative permittivity of 3.55 and a loss tangent of 0.0027.

[0057] In this simulation, the relative permittivity of the dielectric substrate 5 is set to 3.66, a value that has been calibrated and verified through actual measurement.

[0058] like Figure 4 As shown, in the bandpass filter absorption circuit 3 of this invention, the inductor 7 is a wire-engineered 0402HP inductor, the capacitor 6 is a Murata GJM03 capacitor, and the resistor 8 is a 0402 packaged precision thin film 50 Ω resistor. The specific parameter settings are shown in Table 1, which shows the values ​​of the loaded components.

[0059] Table 1

[0060]

[0061] Combination Figure 2 The preferred dimensions of the absorptive microstrip slotted antenna in this embodiment are shown in Table 2, which contains the antenna's structural parameters.

[0062] Table 2

[0063]

[0064] Based on the above structural parameters, a three-dimensional full-wave electromagnetic simulation tool was used to perform parameter scanning and performance evaluation.

[0065] In this embodiment, three antenna prototypes were designed and fabricated: Antenna Sample I, Antenna Sample II, and Antenna Sample III. The reflection coefficient was measured using an R&S ZND vector network analyzer, while the radiation mode, overall efficiency, and antenna gain were measured in a far-field measurement system.

[0066] Figure 5 shows a comparison of the simulated and measured reflection coefficients of the three antenna prototypes. The physical test results of this embodiment show that it exhibits quasi-reflection-free properties (|S0|) in the frequency range of 0.8 GHz to 1.82 GHz. 11 The |<-10 dB characteristic demonstrates state-of-the-art performance in terms of reflection suppression level and quasi-reflection-free bandwidth. Measurements from all three prototypes agree well with optimized simulation results, with minor deviations primarily at the tolerances of actual lumped element values. Furthermore, a degree of reflection suppression is maintained over a wider frequency range beyond this range.

[0067] Figure 6 shows the simulated and measured antenna gain and overall efficiency of antenna sample I in this embodiment. The measured results show that the overall efficiency is approximately 81%, slightly lower than the simulation result; the peak gain measured at 1.31 GHz is 4.06 dBi, and the 3 dB gain bandwidth frequency range is 1.24 GHz ~ 1.38 GHz, which is slightly narrower than the simulation result.

[0068] like Figure 7 and Figure 8 The figures show the simulated and measured radiation patterns of the absorptive microstrip slotted antenna in the E-plane and H-plane at the center frequency, respectively, demonstrating bidirectional radiation characteristics. The cross-polarization level at the main lobe exceeds 14 dB, indicating good radiation performance. Compared to the simulated values, the measured cross-polarization is higher, which may be due to scattering effects introduced by the SMA connector and feed cable.

[0069] In practice, apart from a small amount of f0 signal loss in the bandpass filter absorption circuit 3 (device loss), most of the energy can be effectively radiated through the slot antenna; the measured antenna efficiency can reach 81%; thus, without changing the traditional microstrip slot antenna structure characteristics, the traditional reflective microstrip slot antenna can be converted into an absorptive microstrip slot antenna with wideband quasi-reflection-free characteristics, effectively reducing parasitic signal interference at the RF front-end antenna port.

[0070] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. An absorptive microstrip slot antenna, characterized in that: The system includes a microstrip feed line (1), a slotted ground plane (2), a bandpass filter absorption circuit (3), and a dielectric substrate (5). The microstrip feed line (1) is mounted on the upper surface of the dielectric substrate (5), and the slotted ground plane (2) is mounted on the lower surface of the dielectric substrate (5). The bandpass filter absorption circuit (3) is disposed on the microstrip feed line (1), and its input and output terminals are directly connected to the microstrip feed line (1). The bandpass filter absorption circuit (3) includes a resistor (8) and a resonant circuit, which are connected in parallel. The resonant circuit includes a capacitor (6) and an inductor (7), which are connected in series. It also includes a power supply connector (4), which connects to the microstrip feed line (1) to excite the microstrip feed line (1).

2. The absorptive microstrip slotted antenna according to claim 1, characterized in that: The microstrip feed line (1) is installed at the center of the dielectric substrate (5).

3. The absorptive microstrip slotted antenna according to claim 1, characterized in that: The bandpass filter absorption circuit (3) is connected in series at the optimal loading position of the microstrip feeder (1).

4. The absorptive microstrip slotted antenna according to claim 1, characterized in that: The capacitor (6), inductor (7) and resistor (8) are all provided with protective shells.

5. The absorptive microstrip slotted antenna according to claim 1, characterized in that: The thickness of the dielectric substrate (5) is set to 0.813 mm, the relative permittivity is 3.55, and the loss tangent is 0.0027.

6. The absorptive microstrip slotted antenna according to claim 1, characterized in that: The capacitor (6) is a Murata GJM03 capacitor, the inductor (7) is a wire-engineered 0402HP inductor, and the resistor (8) is a 0402 packaged precision thin film 50Ω resistor.

7. A filtering and absorption method for an absorptive microstrip slotted antenna according to any one of claims 1-6, characterized in that, Includes the following steps: The microstrip slotted antenna operates at the resonant frequency f At 0, the resonant frequency of the resonant circuit is also f 0, at the antenna operating frequency f At position 0, the resonant circuit in the bandpass filter absorption loop (3) is short-circuited, and the resistor (8) will have no effect. Therefore, the antenna operating frequency... f Signals near 0 will flow through the bandpass filter absorption circuit (3) without loss and be efficiently radiated via the microstrip slot antenna; Microstrip slotted antennas far from the operating frequency f At 0, the impedance of the inductor (7) or capacitor (6) in the bandpass filter absorption circuit (3) is higher than the preset threshold. At this time, the impedance of the bandpass filter absorption circuit (3) is provided by the resistor (8). All out-of-band energy flows into the resistor (8). The signal in the working frequency band of the microstrip slot antenna can pass through the bandpass filter absorption circuit (3) without loss and flow to the microstrip slot antenna for radiation. The out-of-band signal is confined in the bandpass filter absorption circuit (3) and absorbed by the resistor (8), thus forming the non-reflection characteristics inside and outside the band.

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