Band elimination filter circuit and capsule endoscope system

Abstract

The utility model discloses a band-stop filter circuit and a capsule endoscope system, the band-stop filter circuit comprises an input port, an output port, a first band-stop filter unit and a second band-stop filter unit, the first band-stop filter unit is electrically connected between the input port and the output port, one end of the second band-stop filter unit is grounded, and the other end of the second band-stop filter unit is grounded. The other end of the first band-stop filter unit is electrically connected between the input port and the first band-stop filter unit or electrically connected between the first band-stop filter unit and the output port; the stop-band frequency band of the first band-stop filtering unit comprises 1710 MHz to 1980 MHz, and the stop-band frequency band of the second band-stop filtering unit comprises 824 MHz to 915 MHz; the second band-stop filtering unit is a four-order or higher-order filtering circuit formed by connecting discrete components in series. According to the invention, interference signals of a low-frequency part and an intermediate-frequency part of a mobile phone signal are filtered, a frequency response curve of 824MHz-915MHz is steep, and the insertion loss is low.

Description

Technical Field

[0001] The utility model relates to the technical field of medical devices, in particular to a band-stop filter circuit and a capsule endoscope system comprising the band-stop filter circuit. Background Art

[0002] In order to non-invasively examine the body cavity organs in animals or humans, especially the digestive tract cavity, a swallowable capsule endoscope is currently used to obtain the internal information of the subject.

[0003] The capsule, swallowed into the body, communicates wirelessly with its control device using the 433MHz frequency band, receiving control commands from the control device or transmitting image information captured within the body to the control device. The low-frequency portion of mobile phone signals includes the uplink frequency bands of Band 5 (824-849MHz) and Band 8 (880-915MHz). The mid-frequency portion of mobile phone signals includes the uplink frequency bands of Band 3 (1710-1785MHz) and Band 1 (1920-1980MHz). The low-frequency portion of mobile phone signals is close to the 433MHz frequency band used by the capsule endoscope system for communication, significantly interfering with the data transmission of the capsule endoscope system. Therefore, the capsule endoscope system needs to suppress interference signals from the mobile phone frequency band within its circuits.

[0004] However, if an integrated band-pass filter chip is used to filter the above two frequency bands of the mobile phone, the insertion loss of the 433MHz signal in the capsule endoscope system communication frequency band will be too large, reaching more than 2dB; if an integrated low-pass filter chip is used for filtering, its cutoff filter frequency cannot be adjusted. The upper limit of the cutoff frequency of the integrated low-pass filter chip is generally 960MHz, which cannot effectively suppress the interference of the low-frequency part of the mobile phone communication 824MHz-915MHz. Utility Model Content

[0005] In order to solve the above technical problems existing in the prior art, the utility model provides a band-stop filter circuit and a capsule endoscope system including the band-stop filter circuit.

[0006] A first aspect of the present application provides a band-stop filter circuit, comprising an input port, an output port, a first band-stop filter unit, and a second band-stop filter unit, wherein the first band-stop filter unit is electrically connected between the input port and the output port, and one end of the second band-stop filter unit is grounded, and the other end is electrically connected between the input port and the first band-stop filter unit, or between the first band-stop filter unit and the output port;

[0007] The stop band frequency band of the first band-stop filter unit includes 1710MHz-1980MHz,

[0008] The stop band frequency band of the second band-stop filter unit includes 824MHz-915MHz;

[0009] The second band-stop filter unit is a 4th-order or higher-order filter circuit constructed by connecting discrete components in series.

[0010] A second aspect of the present application provides a capsule endoscope system, comprising a circuit board and the above-mentioned band-stop filter circuit arranged on the circuit board.

[0011] The band-stop filter circuit provided in the present application can filter the interference signals of the low-frequency and medium-frequency parts of the mobile phone signal. The second band-stop filter unit adopts a fourth-order or higher-order filter circuit formed by connecting discrete components in series, so that the frequency response curve of the band-stop filter circuit to 824MHz-915MHz is steeper, which is conducive to maintaining a low insertion loss at 433MHz, and the wireless communication sensitivity is higher. Compared with the use of integrated filter chips, it is also more cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention.

[0013] Figure 1 A schematic structural diagram of a band-stop filter circuit provided in the first embodiment of the present application;

[0014] Figure 2 A schematic structural diagram of a band-stop filter circuit provided in a second embodiment of the present application;

[0015] Figure 3 A schematic structural diagram of a band-stop filter circuit provided in a third embodiment of the present application;

[0016] Figure 4 for Figure 3 The simulation schematic diagram of the band-stop filter circuit shown. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] The technical solution of this patent is further described in detail below in conjunction with specific implementation methods.

[0019] The following describes in detail embodiments of the present invention, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] The present application provides a band-stop filter circuit 100 for use in a 433 MHz wireless communication circuit. The 433 MHz communication frequency band used by capsule endoscopy systems and other medical devices is close to the low-frequency communication band of mobile phones. The transmission frequency range of GSM Band 5, WCDMA Band 5, LTE Band 5, and NR Band 5 used by mobile phones is 824 MHz to 849 MHz.

[0021] The 433MHz frequency belongs to the ISM band, which has a significant drawback: it is very susceptible to interference. This includes co-channel interference from the 433MHz band, interference from low-frequency (824MHz-915MHz) and mid-frequency (1710MHz-1980MHz) mobile phone wireless transmissions, and interference from 2.4GHz Wi-Fi.

[0022] This application uses a band-stop filter circuit built with discrete components to filter out collected mobile phone interference signals other than 433MHz. It can suppress the low-frequency and intermediate-frequency energy of the mobile phone to a certain extent while ensuring that the insertion loss of 433MHz is large and small, thereby ensuring that the 433MHz receiver will not be interfered with by the high power of other frequency bands, thereby improving the clarity and reliability of the 433MHz signal and effectively improving the communication quality.

[0023] The band-stop filter circuit provided in the present application can be applied to various devices and equipment that perform wireless communications in the 433MHz frequency band and require filtering of mobile phone signals, such as medical equipment, aviation navigation equipment, etc. In the present application, the application of the band-stop filter in a capsule endoscope system is used as an example for explanation, that is, the capsule endoscope system includes a circuit board and the above-mentioned band-stop filter circuit arranged on the circuit board. The capsule endoscope system includes a capsule endoscope and a control device for wirelessly communicating with the capsule endoscope. The above-mentioned circuit board provided with the band-stop filter circuit can be arranged in the control device of the capsule endoscope system and / or the capsule endoscope. It can be understood that the band-stop filter circuit can also be applied to the devices and equipment mentioned or not mentioned above.

[0024] See also Figure 1In a first embodiment of the present application, a band-stop filter circuit 100 is provided, comprising an input port 80, an output port 90, a first band-stop filter unit 10, and a second band-stop filter unit 20. The first band-stop filter unit 10 is electrically connected between the input port 80 and the output port 90. One end of the second band-stop filter unit 20 is grounded, and the other end is electrically connected between the input port 80 and the first band-stop filter unit 10, or electrically connected between the first band-stop filter unit 10 and the output port 90. The stopband frequency band of the first band-stop filter unit 10 includes 1710MHz-1980MHz, and the stopband frequency band of the second band-stop filter unit includes 824MHz-915MHz. The second band-stop filter unit is a 4th-order or higher-order filter circuit constructed by serially connecting discrete components.

[0025] In the band-stop filter circuit 100 provided in the present application, the stopband frequency band of the first band-stop filter unit 10 includes 1710MHz-1980MHz, and the stopband frequency band of the second band-stop filter unit includes 824MHz-915MHz, thereby being able to filter the interference signals of the low-frequency part and the intermediate-frequency part of the mobile phone signal. The second band-stop filter unit adopts a fourth-order or higher-order filter circuit formed by connecting discrete components in series, so that the frequency response curve of the band-stop filter circuit 100 to 824MHz-915MHz is steeper, which is conducive to maintaining a low insertion loss at 433MHz, and the wireless communication sensitivity is higher, which has more cost advantages than the use of integrated filter chips.

[0026] The stopband frequency band in this application refers to the frequency band in which the signal output is attenuated by more than -3dB. The stopband frequency band of the first band-stop filter unit 10 includes 1710MHz-1980MHz. In some embodiments, the stopband frequency band of the first band-stop filter unit 10 also includes other frequency ranges outside the 1710MHz-1980MHz frequency band. Similarly, the stopband frequency band of the second band-stop filter unit includes 824MHz-915MHz. In some embodiments, the stopband frequency band of the second band-stop filter unit also includes other frequency ranges outside the 824MHz-915MHz frequency band.

[0027] Furthermore, the first band-stop filter unit 10 is a second-order filter circuit, comprising a first capacitor C1 and a first inductor L1 electrically connected to each other. Figure 1 As shown, the first capacitor C1 is connected in parallel with the first inductor L1, where the first capacitor is 2.7pF and the first inductor is 2.4nH. In other embodiments, the first capacitor and the first inductor can have other values. In other embodiments, the first capacitor C1 and the first inductor L1 can also be connected in series to filter 1710MHz-1980MHz interference.

[0028] The second band-stop filter unit 20 includes a plurality of subunits 21 connected in series, each of which includes a second capacitor C2 and a second inductor L2 connected in series. A second inductor L2 is electrically connected between adjacent second capacitors C2 in the second band-stop filter unit 20, and a second capacitor C2 is electrically connected between adjacent second inductors L2 in the second band-stop filter unit 20. That is, the second capacitors C2 and the second inductors L2 in the second band-stop filter unit 20 are alternately arranged.

[0029] In the subunit 21, the capacitance value of the second capacitor is L, and the inductance value of the second inductor is C. According to the resonant circuit formula After selecting f in the 824MHz-915MHz range, design the corresponding L*C value and then select the appropriate L and C to meet the requirements. Calculation shows that the L*C value is between 28 and 40. L is in nH and C is in pF, meaning 28pF*nH < LC < 40pF*nH. Preferably, C = 7.2pF and L = 4.3nH.

[0030] Subunit 21 is a second-order filter circuit constructed by connecting discrete components in series. In this embodiment, the second band-stop filter unit 20 includes two subunits 21 and uses a fourth-order filter circuit to achieve rapid attenuation. In other embodiments, if there is ample space on the circuit board, the second band-stop filter unit 20 can optionally include more subunits 21 connected in series, such as three subunits 21 connected in series to form a sixth-order filter circuit, or more subunits 21 connected in series to form a higher-order filter circuit, which can achieve better suppression effects.

[0031] like Figure 1 As shown, one end of the second band-stop filter unit 20 is grounded, and the other end is electrically connected between the first band-stop filter unit 10 and the output port 90. In some variations, one end of the second band-stop filter unit 20 is grounded, and the other end is electrically connected between the first band-stop filter unit 10 and the input port 80. Figure 1 The band-stop filter circuit 100 shown is applied to a wireless communication circuit of a capsule endoscope system to filter out interference from mobile phones in wireless signals.

[0032] See also Figure 2 The second embodiment of the present application provides a band-stop filter circuit 200. The main difference between the band-stop filter circuit 200 and the band-stop filter circuit 100 is that the band-stop filter circuit 200 is provided with a third band-stop filter unit 30, and one end of the second band-stop filter unit 20 is connected between the first band-stop filter unit 10 and the input port 80.

[0033] The third band-stop filter unit 30 and the first band-stop filter unit 10 are connected in series between the input port 80 and the output port 90. The stopband frequency band of the third band-stop filter unit 30 includes 2402MHz-2483MHz, which is used to suppress 2.4GHz short-range wireless communication signals, thereby suppressing the influence of WiFi signals on wireless communications.

[0034] The stopband frequency band of the third band-stop filtering unit 30 includes 2402 MHz-2483 MHz. In some embodiments, the stopband frequency band of the third band-stop filtering unit 30 also includes other frequency ranges other than 2402 MHz-2483 MHz.

[0035] Specifically, the third band-stop filter unit 30 is a second-order filter circuit comprising a third capacitor C3 and a third inductor L3 electrically connected to each other. In this embodiment, the third capacitor C3 and the third inductor L3 are connected in parallel, with the third capacitor C3 being 1.8 pF and the third inductor L3 being 2 nH. It will be appreciated that in other embodiments, the third capacitor C3 and the third inductor L3 may be configured with other values. In other embodiments, the third capacitor C3 and the third inductor L3 in the third band-stop filter unit 30 are connected in series to trap the 2.4 GHz frequency band. When both the third band-stop filter unit 30 and the first band-stop filter unit 10 are LC series circuits, the first inductor L1 or the third inductor L3 is electrically connected between the third capacitor C3 and the first capacitor C1, and the third capacitor C3 or the first capacitor C1 is electrically connected between the first inductor L1 and the third inductor L3. That is, in all four components of the third band-stop filter unit 30 and the first band-stop filter unit 10, the capacitors and inductors are alternately arranged.

[0036] like Figure 2 As shown, the second band-stop filter unit 20 and Figure 1 The second band-stop filter unit 20 provided in the embodiment has the same structure, one end of which is grounded, and the other end is connected between the input port 80 and the first band-stop filter unit 10. In the modified embodiment, one end of the second band-stop filter unit 20 is grounded, and the other end is connected between the output port 90 and the third band-stop filter unit 30.

[0037] See also Figure 3 The third embodiment of the present application provides a band-stop filter circuit 300. The difference between the band-stop filter circuit 300 and the band-stop filter circuit 200 is that one end of the second band-stop filter unit 20 is connected between the first band-stop filter unit 10 and the second band-stop filter unit 30, thereby realizing 824MHz-915MHz frequency band notch.

[0038] See also Figure 4The second band-stop filter unit 20 uses a 4th-order filter circuit to achieve rapid attenuation, and can have a suppression of more than 14dB in the frequency band of 824MHz-915MHz (the frequency band between points m2 and m3 in the figure), and maintains a small insertion loss in the communication frequency band of 433MHz (point m1 in the figure), with only about 0.3dB of suppression, and the wireless communication sensitivity is relatively high.

[0039] For the two suppression frequency bands of 1710MHz-1980MHz and 2402MHz-2483MHz, which are relatively far from 433MHz, second-order filtering circuits (first band-stop filter unit 10 and second band-stop filter unit 30) are used to suppress signals in the corresponding frequency bands. Simulation data shows that the 1710MHz-1980MHz frequency band (the frequency band between points m4 and m5 in the figure) produces approximately 12dB or more of suppression, and the 2402MHz-2483MHz frequency band (the frequency band between points m6 and m7 in the figure) produces over 14dB of suppression, achieving ideal noise filtering results.

[0040] By utilizing the band-stop filter circuit provided in the present application, the out-of-band signal power received in the capsule endoscope system is low, and the low noise amplifier (LNA) at the receiving end is not easily saturated due to excessive power, or because the out-of-band power is too large, other factors that are unfavorable to reception are generated when the internal digital filter is debugged in order to filter out out-of-band interference.

[0041] The above describes in detail the optional implementation methods of the embodiment of the present invention in conjunction with the accompanying drawings. However, the embodiment of the present invention is not limited to the specific details in the above implementation methods. Within the technical concept of the embodiment of the present invention, the technical solution of the embodiment of the present invention can be subjected to various simple modifications, and these simple modifications all fall within the protection scope of the embodiment of the present invention.

[0042] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the embodiments of the present utility model will not further describe various possible combinations.

[0043] In addition, the various implementations of the embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed in the embodiments of the present invention.

Claims

1. A band-stop filter circuit, characterized in that: The device comprises an input port, an output port, a first band-stop filter unit, and a second band-stop filter unit, wherein the first band-stop filter unit is electrically connected between the input port and the output port, and one end of the second band-stop filter unit is grounded, and the other end is electrically connected between the input port and the first band-stop filter unit, or between the first band-stop filter unit and the output port; The stop band frequency band of the first band-stop filter unit includes 1710MHz-1980MHz, The stop band frequency band of the second band-stop filter unit includes 824MHz-915MHz; The second band-stop filter unit is a 4th-order or higher-order filter circuit constructed by connecting discrete components in series.

2. The filter circuit according to claim 1, wherein: The first band-stop filter unit includes a first capacitor and a first inductor electrically connected to each other.

3. The filter circuit according to claim 2, wherein: The first capacitor and the first inductor are connected in parallel, wherein the first capacitor is 2.7 pF and the first inductor is 2.4 nH.

4. The filter circuit according to claim 1, wherein: The second band-stop filter unit includes a plurality of subunits connected in series, and each subunit includes a second capacitor and a second inductor connected in series.

5. The filter circuit according to claim 4, wherein: The capacitance value of the second capacitor is L, the inductance value of the second inductor is C, and then 28pF*nH<LC<40pF*nH.

6. The filter circuit according to claim 5, wherein: C=7.2pF, L=4.3nH.

7. The filter circuit according to any one of claims 1 to 6, wherein: A third band-stop filter unit is included. The third band-stop filter unit and the first band-stop filter unit are connected in series between the input port and the output port. The stopband frequency band of the third band-stop filter unit includes 2402MHz-2483MHz.

8. The filter circuit according to claim 7, wherein: The third band-stop filter unit includes a third capacitor and a third inductor electrically connected to each other.

9. The filter circuit according to claim 8, wherein: The third capacitor and the third inductor are connected in parallel, the third capacitor is 1.8 pF, and the third inductor is 2 nH.

10. A capsule endoscopy system, characterized in that: The invention comprises a circuit board and the band-stop filter circuit according to any one of claims 1 to 9 arranged on the circuit board.

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