An integrated filter antenna

Abstract

The application discloses an integrated filter antenna and relates to the technical field of antennas.The integrated filter antenna comprises a dielectric substrate, a ground inductor and a radiation inductor are printed on the dielectric substrate, the radiation inductor is connected with a microstrip filter, the microstrip filter comprises a first open-circuit stub, an impedance line and a second open-circuit stub, one end of the impedance line is connected with the first open-circuit stub, the other end of the impedance line is connected with the second open-circuit stub, and the microstrip filter further comprises an impedance reference surface which is connected with the ground inductor.The integrated filter antenna has the radiation and filtering capabilities, and the structure size is more compact.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and more particularly to an integrated filter antenna. Background Technology

[0002] Currently, filtering antennas are mainly divided into two categories. One category involves deforming the antenna radiator to create a filtering structure, thereby affecting the antenna's radiation mode to achieve filtering. This type of structure is often used in narrowband filtering applications, such as adding slots to microstrip patch antennas to achieve harmonic suppression, or using slot antennas with defective ground structures. The disadvantage of this type of filtering antenna is that it is difficult to meet the multifunctional requirements of electronic devices.

[0003] Another type integrates a filter on the feed line to implement the filtered antenna. This requires the filter and antenna element to be designed independently. The advantage of this structure is that it reduces the complexity of antenna design and increases the flexibility of selection. However, the disadvantage is that it requires an additional impedance matching network, which increases the insertion loss of the circuit and reduces the performance of the circuit. If an impedance matching network is not used, the filtering characteristics at the passband edge will be greatly deteriorated, and the selectivity of the system will be worse. Summary of the Invention

[0004] Therefore, it is necessary to provide an integrated filtering antenna to address the aforementioned technical problems, thereby solving the problem that the separate design of the antenna and filter in the prior art increases the insertion loss of the circuit, reduces the circuit performance, and results in poor antenna filtering effect.

[0005] To achieve the above objectives, an integrated filtering antenna includes:

[0006] A dielectric substrate has a grounding element and a radiating element printed on it. The radiating element is connected to a microstrip filter. The microstrip filter includes a first open-circuit stub, an impedance line, and a second open-circuit stub. One end of the impedance line is connected to the first open-circuit stub, and the other end of the impedance line is connected to the second open-circuit stub. The microstrip filter also includes an impedance reference surface, which is connected to the grounding element.

[0007] The above solution has the following beneficial effects:

[0008] The integrated filter antenna of this invention integrates a microstrip filter on the antenna, consisting of a first open-circuit stub, a second open-circuit stub, an impedance line, and a reference surface. This elliptic-like filter, compared to other types of filters, achieves a narrower transition bandwidth and lower stopband ripple, which is beneficial for achieving high suppression and miniaturization. Furthermore, this antenna does not require an additional impedance matching network, thus reducing production costs to some extent.

[0009] Optionally, the first open-circuit stub and the second open-circuit stub are symmetrically distributed on both sides of the impedance line, or the first open-circuit stub and the second open-circuit stub are distributed on one side of the impedance line.

[0010] Optionally, in the integrated filter antenna, the first open-circuit stub, the impedance line, and the second open-circuit stub are connected in sequence to form an S-shape.

[0011] Optionally, the narrower end of the radiating oscillator is connected to the microstrip filter.

[0012] Optionally, the dielectric substrate may also be printed with microstrip LC matching segments.

[0013] The effect is:

[0014] The microstrip LC matching section is used to adjust the impedance change caused by wire stripping at the feed port and the impedance mismatch between the microstrip filter input, suppressing the high-frequency energy of the second harmonic. This matching section also constitutes a low-pass filter to improve the filtering effect of the antenna.

[0015] Optionally, the dielectric substrate comprises four layers, with the radiating oscillator, the microstrip filter, and the microstrip LC matching segment all disposed on the first layer, the impedance reference surface disposed on the second layer, the grounding oscillator disposed on the fourth layer, and the third layer of the dielectric substrate not having copper plating.

[0016] Optionally, in the integrated filter antenna, the ground element is a square element.

[0017] Optionally, in the integrated filter antenna, the radiating element is trapezoidal with a gradually widening shape.

[0018] Optionally, each layer of the dielectric substrate has two rows of grounding vias, wherein the first row of grounding vias on each layer is arranged in the same position, the second row of grounding vias on each layer is arranged in the same position, the first row of grounding vias on the first layer is arranged adjacent to the first open-circuit stub, and the second row of grounding vias on the first layer is arranged adjacent to the second open-circuit stub. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1-1 This is a structural diagram of an integrated filter antenna provided in one embodiment of the present invention;

[0021] Figure 1-2This is a structural diagram of the second layer of the dielectric substrate in one embodiment of the present invention;

[0022] Figure 1-3 This is a structural diagram of the fourth layer of the dielectric substrate in one embodiment of the present invention;

[0023] Figure 2 This is an equivalent circuit diagram of a low-pass filter with open-circuit stub loading in one embodiment of the present invention;

[0024] Figure 3 This is a simulation result diagram of the S-parameters of a microstrip filter in one embodiment of the present invention;

[0025] Figure 4 This is a simulation result diagram of the parameters of the integrated filter antenna S11 in one embodiment of the present invention;

[0026] Figure 5 This is a structural diagram of an integrated filter antenna provided in one embodiment of the present invention;

[0027] Figure 6 This is a structural diagram of an integrated filter antenna provided in one embodiment of the present invention;

[0028] Figure 7 This is a structural diagram of an integrated filter antenna provided in one embodiment of the present invention;

[0029] The symbols are explained as follows:

[0030] 100, Dielectric substrate; 200, Radiating oscillator; 300, Microstrip filter; 301, First open-circuit stub; 302, Second open-circuit stub; 303, Impedance line; 400, Microstrip LC matching segment; 401, Inductive microstrip line; 402, Capacitive microstrip line; 501, Feed pad; 502, Feed solder joint; 601, Ground via; 602, Ground via; 700, Impedance reference plane; 800, Grounding oscillator. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0032] In one embodiment, a method such as Figure 1-1The integrated filter antenna shown includes a dielectric substrate 100 made of a four-layer board of FR4 (a type of flame-retardant material) with a thickness T = 1.6 mm and a dielectric constant of 4.3. A grounding element 800 and a radiating element 200 are printed on the dielectric substrate 100, forming a dipole antenna. The radiating element 200 is connected to a microstrip filter 300, which includes a first open-circuit stub 301, an impedance line 303, and a second open-circuit stub 302. One end of the impedance line 303 is connected to the first open-circuit stub 301, and the other end is connected to the second open-circuit stub 302. The microstrip filter 300 also includes an impedance reference surface 700 connected to the grounding element 800.

[0033] like Figure 1-1 As shown, the first open-circuit stub 301 and the second open-circuit stub 302 are symmetrically distributed on both sides of the impedance line 303. Furthermore, the first open-circuit stub 301 is connected to one end of the impedance line 303, and the second open-circuit stub 302 is connected to the other end of the impedance line 303, forming an S-shape.

[0034] Specifically, the microstrip filter 300 mentioned above uses a 4800MHz 1 / 4 wavelength first open-circuit stub 301, a 5000MHz 1 / 4 wavelength second open-circuit stub 302, and a 4900MHz impedance line 303. Together with the impedance reference plane 700, it is equivalent to a low-pass filter loaded with open-circuit stubs, which belongs to the elliptic filter category.

[0035] The aforementioned elliptic-like filter has both zeros and poles at a finite frequency range. The poles and zeros generate equiripple in the passband, while the finite number of transmission zeros in the stopband reduces the transition region, resulting in an extremely steep attenuation curve. Under the same order condition, the elliptic-like filter equivalent to the aforementioned microstrip filter 300 achieves a narrower transition bandwidth and smaller stopband ripple compared to other types of filters, which is beneficial for achieving high suppression and miniaturization.

[0036] The equivalent circuit diagram of the low-pass filter loaded by the first open-circuit stub 301 and the second open-circuit stub 302 is as follows: Figure 2 As shown, L3 is Figure 1-1 The impedance line 303 in the circuit is replaced with a quarter-wavelength open circuit by replacing the series resonators L2, C2 and L4, C4. The resulting circuit produces two transmission zeros at the resonant frequencies of L2, C2 and L4, C4, corresponding to... Figure 1-1 The first open-circuit stub is 301, and the second open-circuit stub is 302. The effect of using two open-circuit stubs is to generate two transmission zeros at 4800MHz and 5000MHz, thereby improving the antenna's suppression bandwidth.

[0037] like Figure 1-1 As shown, the dielectric substrate 100 is printed with a microstrip LC matching segment 400, which includes an inductive microstrip line 401 and a capacitive microstrip line 402. One end of the inductive microstrip line 401 is connected to the impedance line 303, and the other end of the inductive microstrip line 401 is connected to the capacitive microstrip line 402.

[0038] The aforementioned microstrip LC matching section 400 is used to adjust the impedance mismatch between the feed port caused by wire stripping and the input terminal of the microstrip filter 300. This invention aims to suppress the high-frequency energy of the second harmonic. The matching section 400 adopts a series inductor and a parallel capacitor, and this matching section constitutes a low-pass filter.

[0039] The dielectric substrate 100 includes four layers, such as Figure 1-1 As shown, the radiating oscillator 200, the microstrip filter 300, and the microstrip LC matching 400 segments are all arranged in the first layer, as... Figure 1-2 As shown, the impedance reference surface 700 is arranged on the second layer, as... Figure 1-3 As shown, the grounding vibrator 800 is arranged on the fourth layer, and the third layer of the dielectric substrate 100 is not copper-plated and is not shown here.

[0040] In this embodiment, the antenna grounding element 800 is a square element with a wavelength of 2450MHz and a wavelength of 1 / 4 wavelength. As another implementation, the antenna grounding element 800 can also be an element of other shapes, such as a rounded square element.

[0041] like Figure 1-1 As shown, the radiating oscillator 200 is a 2450MHz 1 / 4 wavelength trapezoidal asymptotic radiating oscillator, and the narrower end of the radiating oscillator 200 is connected to the microstrip filter 300.

[0042] The aforementioned trapezoidal gradually widening radiating oscillator 200 can achieve antenna broadband and reduce the Q (quality factor) value. Its effect is that within the useful bandwidth of 2400-2500MHz, the antenna input impedance has good convergence around 50 ohms, which reduces the load pulling effect and provides good matching with the filter when used as a filter load.

[0043] like Figure 1-1 As shown, each layer of the dielectric substrate 100 has two rows of grounding vias 601 and 602. The first row of grounding vias 601 on each layer is arranged in the same position, and the second row of grounding vias 602 on each layer is arranged in the same position. The first row of grounding vias 601 on the first layer is arranged adjacent to the first open-circuit stub 301, and the second row of grounding vias 602 on the first layer is arranged adjacent to the second open-circuit stub 302.

[0044] The areas where the aforementioned grounding vias 601 and 602 are located are high-current areas. Using two rows of grounding vias can better ensure contact between the impedance reference surface 700 and the 1 / 4 wavelength grounding vibrator 800, thus avoiding the generation of other parasitic parameters.

[0045] like Figure 1-1 and Figure 1-2 As shown, the impedance reference plane 700 provides a reference ground for the microstrip filter 300 and the microstrip LC matching section 400. Its first layer spacing with the dielectric substrate 100 is 5 mil, which aims to reduce the microstrip line width and obtain equivalent inductance and capacitance within a smaller width range.

[0046] like Figure 1-1 As shown, feed pads 501 and 502 are feed soldering points. Feed soldering point 502 is connected to the impedance reference ground 700 on the third layer of the dielectric substrate 100 through grounding vias 601 and 602, and to the grounding vibrator 800 on the fourth layer of the dielectric substrate 100 through grounding vias 601 and 602. The function of the feed line is to connect the antenna to the transceiver and receiver, and to transmit radio frequency energy.

[0047] To verify the effectiveness of the microstrip filter 300 in this embodiment, an online simulation of the antenna's microstrip filter 300 was performed, such as... Figure 3 The simulation results shown are as follows: from the left side, the lower curve is the return loss curve, and the upper curve is the insertion loss curve. According to sampling points 5 and 6 on the return loss curve, the return loss is less than -12.6 dB in the passband 2.4-2.5 GHz, indicating good impedance matching. According to sampling points 3 and 4 on the insertion loss curve, the insertion loss is less than -31.7 dB in the suppression band 4.8-5.0 GHz, achieving high suppression.

[0048] To verify the antenna filtering effect of this embodiment, an online simulation of the antenna was performed, such as... Figure 4 As shown, the simulation results of the integrated 2.4G second harmonic filter antenna parameters show that, according to the results of sampling points 1, 2, and 3 on the curve, the matching is good in the useful frequency band of 2400-2500MHz. According to the results of sampling points 4 and 5 on the curve, the mismatch is in the suppression band of 4800-5000MHz, which is consistent with the expectations.

[0049] The integrated filter antenna in this embodiment has a radiating element 200 connected to a microstrip filter 300, and the microstrip filter 300 is connected to an LC matching section 400. It has the capabilities of radiation, impedance matching, and filtering, and its structural size is often more compact than designs that separate the antenna and the filter.

[0050] In one embodiment, a method such as Figure 5The integrated filter antenna shown includes a dielectric substrate 100 made of a four-layer board of FR4 (a type of flame-retardant material) with a thickness T = 1.6 mm and a dielectric constant of 4.3. A grounding element 800 and a radiating element 200 are printed on the dielectric substrate 100, forming a dipole antenna. The radiating element 200 is connected to a microstrip filter 300, which includes a first open-circuit stub 301, an impedance line 303, and a second open-circuit stub 302. One end of the impedance line 303 is connected to the first open-circuit stub 301, and the other end is connected to the second open-circuit stub 302. The microstrip filter 300 also includes an impedance reference surface 700 connected to the grounding element 800.

[0051] like Figure 5 As shown, the first open-circuit stub 301 and the second open-circuit stub 302 are symmetrically distributed on both sides of the impedance line 303. The first open-circuit stub 301 and the second open-circuit stub 302 are serrated L-shaped. The first open-circuit stub 301 is connected to one end of the impedance line 303, and the second open-circuit stub 302 is connected to the other end of the impedance line 303, forming an S-shape.

[0052] In this embodiment, the microstrip filter using the above structure can achieve the same level as... Figure 1-1 The microstrip filter 300 shown has the same filtering effect.

[0053] In one embodiment, a method such as Figure 6 The integrated filter antenna shown includes a dielectric substrate 100 made of a four-layer board of FR4 (a type of flame-retardant material) with a thickness T = 1.6 mm and a dielectric constant of 4.3. A grounding element 800 and a radiating element 200 are printed on the dielectric substrate 100, forming a dipole antenna. The radiating element 200 is connected to a microstrip filter 300, which includes a first open-circuit stub 301, an impedance line 303, and a second open-circuit stub 302. One end of the impedance line 303 is connected to the first open-circuit stub 301, and the other end is connected to the second open-circuit stub 302. The microstrip filter 300 also includes an impedance reference surface 700 connected to the grounding element 800.

[0054] like Figure 6As shown, the first open-circuit stub 301 and the second open-circuit stub 302 are symmetrically distributed on both sides of the impedance line 303. The first open-circuit stub 301 and the second open-circuit stub 302 are G-shaped. The first open-circuit stub 301 is connected to one end of the impedance line 303, and the second open-circuit stub 302 is connected to the other end of the impedance line 303, forming an S-shape.

[0055] In this embodiment, the microstrip filter using the above structure can achieve the same level as... Figure 1-1 The microstrip filter 300 shown has the same filtering effect.

[0056] In one embodiment, a method such as Figure 7 The integrated filtering antenna shown includes a dielectric substrate 100 made of a four-layer board of FR4 (a type of flame-retardant material) with a thickness T = 1.6 mm and a dielectric constant of 4.3. A grounding element 800 and a radiating element 200 are printed on the dielectric substrate 100. The radiating element 200 is connected to a microstrip filter 300. The microstrip filter 300 includes a first open-circuit stub 301, an impedance line 303, and a second open-circuit stub 302. One end of the impedance line 303 is connected to the first open-circuit stub 301, and the other end is connected to the second open-circuit stub 302. The microstrip filter 300 also includes an impedance reference surface 700 connected to the grounding element 800.

[0057] like Figure 7 As shown, the first open-circuit stub 301 and the second open-circuit stub 302 are distributed on one side of the impedance line 303. The first open-circuit stub 301 and the second open-circuit stub 302 are L-shaped. The first open-circuit stub 301 is connected to one end of the impedance line 303, and the second open-circuit stub 302 is connected to the other end of the impedance line 303, forming a G-shape.

[0058] In this embodiment, the microstrip filter using the above structure can achieve the same level as... Figure 1-1 The microstrip filter 300 shown has the same filtering effect.

[0059] As other implementations, the open-circuit stubs 301 and 302 included in the microstrip filter 300 of the integrated filter antenna can also have various other shapes and distributions.

[0060] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An integrated filter antenna, characterized in that, include: A dielectric substrate has a grounding element and a radiating element printed on it. The radiating element is connected to a microstrip filter. The microstrip filter includes a first open-circuit stub, an impedance line, and a second open-circuit stub. One end of the impedance line is connected to the first open-circuit stub, and the other end of the impedance line is connected to the second open-circuit stub. The microstrip filter also includes an impedance reference surface, which is connected to the grounding element. The first open-circuit stub and the second open-circuit stub are symmetrically distributed on both sides of the impedance line; The dielectric substrate is also printed with a microstrip LC matching segment, which includes an inductive microstrip line and a capacitive microstrip line. One end of the inductive microstrip line is connected to the impedance line, and the other end of the inductive microstrip line is connected to the capacitive microstrip line. The dielectric substrate comprises four layers. The radiating oscillator, the microstrip filter, and the microstrip LC matching segment are all disposed on the first layer of the dielectric substrate. The impedance reference surface is disposed on the second layer of the dielectric substrate. The grounding oscillator is disposed on the fourth layer of the dielectric substrate. The third layer of the dielectric substrate is not copper-plated. Each layer of the dielectric substrate has two rows of grounding vias, wherein the first row of grounding vias on each layer is arranged in the same position, and the second row of grounding vias on each layer is arranged in the same position. The first row of grounding vias on the first layer is arranged adjacent to the first open-circuit stub, and the second row of grounding vias on the first layer is arranged adjacent to the second open-circuit stub.

2. The integrated filter antenna as described in claim 1, characterized in that, The first open-circuit stub, the impedance line, and the second open-circuit stub are connected in sequence to form an S-shape.

3. The integrated filter antenna as described in claim 1, characterized in that, The first open-circuit stub is connected to the impedance line to form a G-shape, and the impedance line is connected to the second open-circuit stub to form a G-shape.

4. The integrated filter antenna as described in claim 1, characterized in that, The grounding vibrator is a square vibrator.

5. The integrated filter antenna as described in claim 1, characterized in that, The radiating oscillator is trapezoidal and gradually widens, and the narrower end of the radiating oscillator is connected to the microstrip filter.

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