CN113193850A - Low-power filter - Google Patents
Low-power filter Download PDFInfo
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- CN113193850A CN113193850A CN202110353064.XA CN202110353064A CN113193850A CN 113193850 A CN113193850 A CN 113193850A CN 202110353064 A CN202110353064 A CN 202110353064A CN 113193850 A CN113193850 A CN 113193850A
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- 238000001914 filtration Methods 0.000 claims abstract description 59
- 230000005540 biological transmission Effects 0.000 claims abstract description 5
- 239000003990 capacitor Substances 0.000 claims description 78
- 238000004088 simulation Methods 0.000 abstract description 24
- 238000003780 insertion Methods 0.000 abstract description 21
- 230000037431 insertion Effects 0.000 abstract description 21
- 230000004913 activation Effects 0.000 abstract description 9
- 230000005764 inhibitory process Effects 0.000 abstract description 8
- 230000003321 amplification Effects 0.000 abstract description 6
- 238000003199 nucleic acid amplification method Methods 0.000 abstract description 6
- 238000010586 diagram Methods 0.000 description 12
- 238000012360 testing method Methods 0.000 description 10
- 230000001629 suppression Effects 0.000 description 9
- 238000013461 design Methods 0.000 description 7
- 230000001939 inductive effect Effects 0.000 description 2
- 238000013459 approach Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005662 electromechanics Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/04—Frequency selective two-port networks
Abstract
The invention provides a low-power filter, which sequentially comprises an input port, a first filtering unit, a second filtering unit, a third filtering unit, a fourth filtering unit and an output port along the transmission direction of a radio frequency input signal; the first filtering unit and the third filtering unit are series filtering circuits, and the second filtering unit and the fourth filtering unit are parallel filtering circuits. The invention defines the insertion loss of a low-power band-pass filter, the inhibition indexes at the positions of 4.5MHz outside a band and 27.095MHz of an activation signal of a transponder, and the simulation and implementation mode of the low-power filter, and defines the maximum insertion loss of the low-power band-pass filter inside the band (13.55+/-2.5MHz), the minimum inhibition indexes at the positions of 4.5MHz outside the band (FSK signal) and 27.095MHz (activation signal) in order to ensure the normal demodulation of the signal at a digital part after the low-power band-pass filter passes through a front-stage filtering amplification circuit and a rear-stage filtering amplification circuit.
Description
Technical Field
The invention belongs to the field of electromechanics, and particularly relates to a low-power filter.
Background
The european loop vehicle needs to receive CDMA (code division multiple access) signals from the trackside equipment while ensuring proper operation of the transponder. A transponder refers to an electronic module capable of transmitting a message reply message. In recent years, due to the rapid development of radio frequency technology, transponders have new meanings and meanings, also called smart tags or labels. The intelligent label is an innovation of a radio frequency label, and consists of a label with viscosity and an ultrathin radio frequency label. The working principle of the transponder is as follows: when the vehicle-mounted antenna approaches the transponder, a magnetic field of 27.095MHz is induced by a coupling coil of the transponder, and the energy receiving circuit converts the magnetic field into electric energy, so that a power supply required by the operation of the transponder is established, and the transponder starts to operate. The transponder activation signal was 27.095MHz and the transmit board output power was 44dBm (25W), both of which were carried in a coaxial cable.
The invention is matched with a high-power radio frequency filter or filters 27.095MHz signals according to the actual situation, thereby ensuring the normal receiving of the CDMA signals of 13.55 MHz.
Disclosure of Invention
In order to solve the above problems, the present invention provides a low power filter, which includes an input port, a first filtering unit, a second filtering unit, a third filtering unit, a fourth filtering unit, and an output port in sequence along a transmission direction of a radio frequency input signal;
the first filtering unit and the third filtering unit are series filtering circuits, and the second filtering unit and the fourth filtering unit are parallel filtering circuits.
Further, the first filtering unit comprises a capacitor C1 and an inductor L1, one end of the capacitor C1 is connected in series with the inductor L1, and the other end of the capacitor C1 is connected to the input port.
Furthermore, the second filtering unit includes a capacitor C2 and an inductor L2, one end of the capacitor C2 is connected to the inductor L1, the other end of the capacitor C2 is grounded, and two ends of the capacitor C2 are connected in parallel to the inductor L2.
Furthermore, the third filtering unit includes a capacitor C3 and an inductor L3, one end of the capacitor C3 is connected to the end of the capacitor C2 away from the ground, and the other end of the capacitor C3 is connected in series to the inductor L3.
Further, the fourth filtering unit includes a capacitor C4, a capacitor C5, and an inductor L4, one end of the capacitor C4 is connected to the inductor L3, the other end of the capacitor C4 is grounded, and two ends of the capacitor C4 are respectively connected in parallel to the capacitor C5 and the inductor L4.
Furthermore, one end of the capacitor C4, which is far away from the inductor L3, is connected to a radio frequency connector J1, and the radio frequency connector J1 has five pins, one of the pins is connected to the inductor L3, and the rest of the pins are grounded.
Further, the band-pass filter adopts a fourth-order LC filter circuit.
The invention defines the insertion loss of a low-power band-pass filter, the inhibition indexes at the positions of 4.5MHz outside a band and 27.095MHz of an activation signal of a transponder, and the simulation and implementation mode of the low-power filter, and defines the maximum insertion loss of the low-power band-pass filter inside the band (13.55+/-2.5MHz), the minimum inhibition indexes at the positions of 4.5MHz outside the band (FSK signal) and 27.095MHz (activation signal) in order to ensure the normal demodulation of the signal at a digital part after the low-power band-pass filter passes through a front-stage filtering amplification circuit and a rear-stage filtering amplification circuit. The low-power filter of the invention realizes ADS modeling simulation and is completed by optimizing the values of the inductance and the capacitance.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 shows a schematic representation of a simulation model of a bandpass filter in an embodiment of the invention;
FIG. 2 is a diagram illustrating simulation results of in-band insertion loss of a band-pass filter according to an embodiment of the present invention;
FIG. 3 is a diagram showing simulation results of standing waves at a port of a band-pass filter according to an embodiment of the present invention;
FIG. 4 is a schematic diagram illustrating a circuit design structure and connection relationship of a low-power filter according to an embodiment of the present invention;
FIG. 5 shows a circuit board schematic of a low power filter in an embodiment of the invention;
FIG. 6 is a diagram illustrating the in-band insertion loss test results of a low power filter according to an embodiment of the present invention;
FIG. 7 is a diagram showing the standing wave test result of the port of the low-power filter in the embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The present invention was made in accordance with the standard of Subset-044. The invention defines the insertion loss of a low-power band-pass filter (band-pass filter), the inhibition indexes of the positions of 4.5MHz out of band and 27.095MHz, and the simulation and implementation modes of the low-power filter. The invention effectively restrains the activation signal 27.095MHz, and ensures that the CDMA signal of 13.5MHz can be normally received in the radio frequency link.
The Subset-044 standard requires that the field intensity of a 13.55MHz receiving signal is between 23 and 76dBuA/m, and the power converted by an MFP (MAGNETIC FIELD PROBE) antenna is as follows: -36 to-89 dBm. After the signals pass through the front and rear filtering and amplifying circuits, in order to ensure the signals to be demodulated normally in the digital part, the maximum insertion loss of the low-power band-pass filter in the band (13.55+/-2.5MHz) and the minimum inhibition indexes of the low-power band-pass filter in the band (4.5 MHz (FSK signal) and 27.095MHz (activation signal) are defined. The low-power filter of the scheme is specifically realized by using ADS modeling simulation and optimizing the numerical values of the inductor and the capacitor.
The LC filter belongs to a passive filter, is a filter circuit formed by utilizing the combined design of an inductor, a capacitor and a resistor, and can filter one or more times of harmonic waves, and the most common LC filter structure which is easy to adopt is to connect the inductor and the capacitor in series and form a low-impedance bypass for main subharmonics (3, 5 and 7); the single-tuned filter, the double-tuned filter and the high-pass filter belong to passive filters. A band-pass filter is a device that allows waves of a particular frequency band to pass while shielding other frequency bands, and an LC circuit is generally referred to as a resonant circuit. For a passive port network including capacitive, inductive and resistive components, the ports may be capacitive, inductive and resistive, when the voltage U and current I at the ports of the circuit are in phase and the circuit is resistive. This is called a resonance phenomenon, and such a circuit is called a resonance circuit.
In the present invention, a low power band pass filter is used to increase the rejection of 4.5MHz and 27.095MHz signals, located after the LNA (low noise amplifier) amplifier.
The main index definition of the low-power band-pass filter is obtained by calculation according to the Subset-044 standard requirement and the link of the vehicle-mounted equipment of the actual antenna transponder transmission system, and the minimum requirement is as follows:
and (3) internal insertion loss:
the in-band insertion loss is the amount of signal attenuation that falls within the operating frequency when an input wideband signal passes through a low power bandpass filter. The signal pass band (11.05 MHz-16.05 MHz) is more than or equal to-4 dB, the working frequency is defined as the central frequency of 13.55MHz, the bandwidth is 5MHz, namely: 13.55+/-2.5MHz (11.05 MHz-16.05 MHz), and the maximum attenuation in this frequency band is defined as 4 dB.
Out-of-band suppression:
the out-of-band rejection refers to the attenuation of the filter outside a defined passband frequency range or for a certain specific frequency band, and the out-of-band rejection refers to the degree of rejection of signals outside the passband and is the amount of attenuation of signals at a specified frequency point after passing through the bandpass filter. For 27.095MHz, as much suppression as possible is required, less than or equal to-25 dB is required based on the RF board link budget, and less than or equal to-25 dB for 6MHz and 4.5 MHz.
Port standing wave:
the port standing wave refers to return loss (return loss RL (return loss) refers to the ratio of the power reflected by the radio frequency input signal to the power of the input signal, and the return loss is smaller and better) between 11.05MHz and 16.05MHz in a working band, and is less than or equal to-10 dB.
The insertion loss in the passband frequency range is defined as the ratio of the input power and the output power of the filter. The definition standard is often-3 dB, i.e. the so-called "3 dB bandwidth". In some testing and measurement applications (e.g., spectral surveys), the pass-band insertion loss of the filter is not very important, as the insertion loss produced by the filter can be corrected in the final result as part of the systematic error. In high power applications, the filter loss is very important, and even with an insertion loss of only 1dB, the power loss can reach about 20%.
Fig. 1 shows a schematic diagram of a simulation model of a bandpass filter in an embodiment of the present invention, in fig. 1, an ADS simulation design is used to perform simulation processing on the bandpass filter, and in order to ensure the flatness of amplitude-frequency characteristics in a passband, a maximum flat (butterworth) structure is used, in the design of the bandpass filter of the present invention, the center frequency is 13.55MHz, the 1dB bandwidth is 5MHz, the operating frequency band is 11.05MHz to 16.05MHz, three frequency suppression points are designed, one is 27.095MHz, one is 6MHz, and the other is 4.5 MHz. The out-of-band rejection is designed in terms of 25 dB. And (3) establishing an ideal model, performing simulation check, and after a preliminary result is obtained, replacing the selected inductor and capacitor with an actual model to perform simulation optimization. The band-pass filter can meet the performance requirement by adopting a four-order LC circuit, if the order is larger, the in-band insertion loss is increased, but the out-of-band rejection is better, and the band-pass filter adopts a four-order form in comprehensive consideration.
In fig. 1, a capacitor C10 and an inductor L10 are connected in series to form a first-order filter circuit, the element value of the capacitor C10 is 430pF, and the element value of the inductor L10 is 560 nH; a capacitor C9 and an inductor L9 are connected in parallel to form a second-order filter circuit, one end of a capacitor C9 is connected with the inductor L10, the other end of the capacitor C9 is grounded, the element value of the capacitor C9 is 470pF, and the element value of the inductor L9 is 330 nH; an inductor L7 and a capacitor C8 are connected in series to form a third-order filter circuit, one end of a capacitor C8 is connected with the inductor L9, wherein the element value of the inductor L7 is 1.5uH, and the element value of the capacitor C8 is 100 pF; the capacitor C11, the capacitor C12 and the inductor L11 are connected in parallel to form a fourth-order filter circuit, wherein the capacitor C12 is connected with the inductor L7, the capacitor C11 and the inductor L11 are connected in parallel to the capacitor C12, the element value of the capacitor C11 is 330pF, the element value of the capacitor C12 is 270pF, and the element value of the inductor L11 is 220 nH.
Fig. 2 shows a schematic diagram of a simulation result of in-band insertion loss of a band-pass filter in the embodiment of the present invention, and fig. 3 shows a schematic diagram of a simulation result of standing waves at a port of a band-pass filter in the embodiment of the present invention, and it can be seen from the simulation result that: in the working band, the insertion loss is maximum between 11.05MHz and 16.05 MHz: -3.639dB, with a rejection of-31.135 dB at 27.09MHz, of-30.91 dB at 6MHz outside the operating band, and-12.544 dB at the worst of the port standing wave inside the operating band. The simulation data can meet the design definition requirements.
Fig. 4 is a schematic diagram illustrating a circuit design structure and connection relationship of a low power filter according to an embodiment of the present invention, in which J1 represents a radio frequency connector, 0R represents a resistor of 0, and an input terminal of an LNA is connected to an input terminal of an LNA in a push-in type connection manner, which enables the connector to be connected and disconnected very quickly and shortens an installation time of the connector. The MCX connector still has good electrical property when the frequency reaches 6GHz, can be adapted to various cables including semi-rigid cables, flexible cables and the like, and is reliable in connection and long in service life.
In fig. 1, the filter includes an input port, a first filtering unit, a second filtering unit, a third filtering unit, a fourth filtering unit, and an output port in sequence along a transmission direction of a radio frequency input signal; the first filtering unit and the third filtering unit are series filtering circuits, and the second filtering unit and the fourth filtering unit are parallel filtering circuits. The first filtering unit comprises a capacitor C1 and an inductor L1, one end of the capacitor C1 is connected with the inductor L1 in series, the other end of the capacitor C1 is connected with the input port and corresponds to a simulation model, the element value of the capacitor C1 is 430pF, and the element value of the inductor L1 is 560 nH; the second filtering unit comprises a capacitor C2 and an inductor L2, one end of the capacitor C2 is connected with the inductor L1, the other end of the capacitor C3526 is grounded, the two ends of the capacitor C2 are connected with the inductor L2 in parallel, the element value of the capacitor C2 is 470pF, and the element value of the inductor L2 is 330 nH; the third filtering unit comprises a capacitor C3 and an inductor L3, one end of a capacitor C3 is connected with one end, far away from the grounding end, of the capacitor C2, the other end of the capacitor C3 is connected with an inductor L3 in series, the element value of the capacitor C3 is 100pF, and the element value of the inductor L3 is 1.5 uH; the fourth filtering unit comprises a capacitor C4, a capacitor C5 and an inductor L4, one end of the capacitor C4 is connected with the inductor L3, the other end of the capacitor C4 is grounded, two ends of the capacitor C4 are respectively connected with the capacitor C5 and the inductor L4 in parallel, the component value of the capacitor C4 is 270pF, the component value of the capacitor C5 is 330pF, and the component value of the inductor L4 is 220 nH.
Specifically, the one end that inductance L3 is kept away from to electric capacity C4 is connected with connector J1, has five pins on the connector J1, and one of them pin is connected with inductance L3, and all the other pins are all grounded, and connector J1 is for the test, and four pins are all grounded and can be reacted out test circuit's signal index, make things convenient for the test signal.
Specifically, the embodiment of the present invention is exemplified by a fourth-order filter circuit, and in the specific implementation process, the filter may be a filter of more than four orders, and is within the protection scope of the present invention as long as the effect that the bandwidth of the present invention is defined to include 11.05MHz to 16.05MHz, 27.09MHz, and the suppression is greater than 25dB (or more), and 6MHz, and the suppression of 4.5MHz is greater than 25dB (or more) can be achieved.
Fig. 5 is a schematic diagram of a circuit board of a low power filter according to an embodiment of the present invention, in fig. 5, a connector J1 and a connector J2 are disposed at two ends of the circuit board, one connector of the connector is connected to a circuit implemented by the present invention, and the position and the connection relationship of the circuit board in fig. 5 are the same as those of the circuit implemented by the embodiment of the present invention in fig. 4.
Fig. 6 shows a schematic diagram of a test result of in-band insertion loss of the low-power filter in the embodiment of the present invention, fig. 7 shows a schematic diagram of a test result of port standing wave of the low-power filter in the embodiment of the present invention, from the test result, the in-band insertion loss of 11.05MHz to 16.05MHz is-1.6 dB, which is better than the simulation result of-3.639 dB, the suppression at 27.095MHz out of band is-30.954 dB, which is close to the simulation result of-31.135 dB, the suppression at 6MHz is-30.27 dB, and the simulation result is substantially-30.91 dB. The standing wave of the port in the working band of 11.05 MHz-16.05 MHz is less than-10 dB, which is close to the simulation result. All the above test indexes are superior to the definition requirement. The design of the invention is satisfied and can be applied to practical engineering. The bandwidth is defined to include 11.05MHz to 16.05MHz, 27.09MHz, and the suppression is more than 25dB (or more), and the 6MHz, 4.5MHz suppression is more than 25dB (or more).
The invention defines the insertion loss of a low-power band-pass filter, the inhibition indexes at the positions of 4.5MHz outside a band and 27.095MHz of an activation signal of a transponder, and the simulation and implementation mode of the low-power filter, and defines the maximum insertion loss of the low-power band-pass filter inside the band (13.55+/-2.5MHz), the minimum inhibition indexes at the positions of 4.5MHz outside the band (FSK signal) and 27.095MHz (activation signal) in order to ensure the normal demodulation of the signal at a digital part after the low-power band-pass filter passes through a front-stage filtering amplification circuit and a rear-stage filtering amplification circuit. The low-power filter of the invention realizes ADS modeling simulation and is completed by optimizing the values of the inductance and the capacitance.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (7)
1. A low-power filter is characterized by comprising an input port, a first filtering unit, a second filtering unit, a third filtering unit, a fourth filtering unit and an output port in sequence along the transmission direction of a radio frequency input signal;
the first filtering unit and the third filtering unit are series filtering circuits, and the second filtering unit and the fourth filtering unit are parallel filtering circuits.
2. The low power filter according to claim 1,
the first filtering unit comprises a capacitor C1 and an inductor L1, wherein one end of the capacitor C1 is connected with the inductor L1 in series, and the other end of the capacitor C1 is connected with the input port.
3. The low power filter according to claim 2,
the second filtering unit comprises a capacitor C2 and an inductor L2, one end of the capacitor C2 is connected with the inductor L1, the other end of the capacitor C2 is grounded, and two ends of the capacitor C2 are connected with the inductor L2 in parallel.
4. The low power filter according to claim 3,
the third filtering unit comprises a capacitor C3 and an inductor L3, one end of the capacitor C3 is connected with one end, far away from the ground end, of the capacitor C2, and the other end of the capacitor C3 is connected with the inductor L3 in series.
5. The low power filter according to claim 4,
the fourth filtering unit comprises a capacitor C4, a capacitor C5 and an inductor L4, one end of the capacitor C4 is connected with the inductor L3, the other end of the capacitor C4 is grounded, and two ends of the capacitor C4 are respectively connected with the capacitor C5 and the inductor L4 in parallel.
6. The low-power filter according to claim 5, wherein a radio frequency connector J1 is connected to an end of the capacitor C4 away from the inductor L3, and the radio frequency connector J1 has five pins, one of the pins is connected to the inductor L3, and the other pins are grounded.
7. The low power filter according to claim 1, wherein the filter is a band pass filter, and the band pass filter employs a fourth order LC filter circuit.
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| CN202110353064.XA CN113193850A (en) | 2021-04-01 | 2021-04-01 | Low-power filter |
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| CN202110353064.XA CN113193850A (en) | 2021-04-01 | 2021-04-01 | Low-power filter |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9455686B1 (en) * | 2015-04-02 | 2016-09-27 | Wistron Neweb Corp. | Wireless communication device and tunable filter thereof |
| CN107425823A (en) * | 2017-07-20 | 2017-12-01 | 安徽矽芯微电子科技有限公司 | A kind of ultra wide band bandpass filter |
| CN110932699A (en) * | 2019-11-25 | 2020-03-27 | 中国计量大学上虞高等研究院有限公司 | Miniaturized high-suppression LTCC column-type inductance band-pass filter |
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2021
- 2021-04-01 CN CN202110353064.XA patent/CN113193850A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9455686B1 (en) * | 2015-04-02 | 2016-09-27 | Wistron Neweb Corp. | Wireless communication device and tunable filter thereof |
| CN107425823A (en) * | 2017-07-20 | 2017-12-01 | 安徽矽芯微电子科技有限公司 | A kind of ultra wide band bandpass filter |
| CN110932699A (en) * | 2019-11-25 | 2020-03-27 | 中国计量大学上虞高等研究院有限公司 | Miniaturized high-suppression LTCC column-type inductance band-pass filter |
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