An antenna element with low harmonic radiation

Abstract

The application provides an antenna unit with low harmonic radiation, comprising a first filter circuit arranged between an energy transmitting ring of an antenna and a BTM, for low-pass filtering of a BTM cable transmission signal, so as to reduce harmonic radiation of the energy transmitting ring. The antenna unit of the application can reduce harmonic components on the BTM main signal, so as to reduce harmonic radiation emission of the antenna on the main signal path, and improve the matching range of the antenna unit and the BTM.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of rail transit communication technology, and particularly relates to an antenna unit with low harmonic radiation. BACKGROUND

[0002] The BTM antenna unit can be used for detecting transponders and has two basic functions: 1. radiating energy to the transponder through an A4 interface; and 2. receiving the FSK (A1 interface) signal of the transponder. In order to be able to detect whether the BTM detection antenna circuit is working normally, a self-checking circuit is further provided: responding to the antenna unit self-checking request sent by the BTM and sending a detection signal.

[0003] The BTM antenna unit can be used for transmitting and receiving the bidirectional transmission of energy carriers, and generally comprises a receiving coil and a transmitting coil, can radiate the energy carrier transmitted by the BTM to the ground, receive the uplink signal sent by the transponder, and transmit the uplink signal to the BTM. In the BTM open state, the BTM antenna unit can continuously radiate a 27MHz energy carrier (CW, Continuous Wave) to the ground, while receiving the FSK (Frequency-shift keying) of the uplink of the transponder. When idle (no transponder), the self-checking of the antenna transmission energy intensity and the receiving link is triggered and executed by the decoding board of the BTM.

[0004] In the prior art, when the second, third and multiple harmonics of the BTM cable signal (main signal) should be radiated, it is difficult to meet the harmonic radiation emission requirements of the relevant railway standards, and therefore, the requirements for the main signal emitted by the BTM are very high, the processing difficulty of the BTM main signal is large, and the use range is small. SUMMARY

[0005] In view of the above problems, the application provides an antenna unit with low harmonic radiation, comprising: a first filter circuit,

[0006] The first filter circuit is arranged between the energy transmission ring of the antenna and the BTM, and is used for low-pass filtering the BTM cable transmission signal, so as to reduce the harmonic radiation of the energy transmission ring.

[0007] Further, the first filter circuit is arranged on an independent board card different from the antenna main board and the antenna transmission board.

[0008] The first port of the first filter circuit is connected with the BTM cable; the second port is connected with the signal port of the antenna main board; and the third port is connected with the signal port on the antenna transmission board.

[0009] Further, the first filter circuit comprises a first port, a second port, a third port and a filter module.

[0010] The first end of the filter module is connected to the first port, and the second end is connected to the second port and the third port respectively;

[0011] The filter module comprises a first capacitor, a second capacitor, a third capacitor, a first inductor and a second inductor; the first inductor and the second inductor are connected in series, the first end of the first inductor is the first end of the filter module, the second end of the first inductor is connected to the second inductor, the first end of the second inductor is connected to the second end of the first inductor, and the second end of the second inductor is the second end of the filter module;

[0012] The first end of the first capacitor is connected to the first end of the first inductor, and the second end of the first capacitor is grounded; the first end of the second capacitor is connected to the second end of the first inductor, and the second end of the second capacitor is grounded; the first end of the third capacitor is connected to the second end of the second inductor, and the second end of the third capacitor is grounded.

[0013] Further, the second end of the filter module is connected to the third port through a fourth capacitor.

[0014] Further, the antenna unit further comprises a first resonator and a power isolation unit;

[0015] The receiving end of the signal interface of the antenna mainboard is connected to the first end of the energy receiving ring through the first resonator;

[0016] The ground end of the signal interface of the antenna mainboard is connected to the second end of the energy receiving ring through the power isolation unit; the power isolation unit is used for isolating the direct current power supply;

[0017] The first resonator is used for adjusting the characteristic impedance parameter of the antenna and performing impedance matching.

[0018] Further, the power isolation unit comprises a plurality of parallel capacitors.

[0019] Further, the first resonator comprises a fifth capacitor and a third inductor connected in parallel.

[0020] Further, the energy transmitting ring comprises a plurality of resonant units connected in series and a first resistor; the first resistor is a nominal value of 50 ohms resistor with a ground end, the power is not less than 20W, and the first resistor is cooled through an external heat sink.

[0021] Further, the antenna unit further comprises a second filter circuit,

[0022] The second filter circuit is used for isolating the high-frequency signal of the BTM cable backward power supply and the trigger circuit power supply. Further, the second filter circuit comprises a fourth inductor, a fifth inductor, a sixth capacitor and a seventh capacitor;

[0023] The first end of the fourth inductor is connected to the input end of the second filter circuit, the second end of the fourth inductor is connected to the first end of the fifth resonant unit, and the fifth resonant unit comprises a fifth inductor, a sixth capacitor and a seventh capacitor in parallel;

[0024] The second end of the fifth resonant unit is connected to the output end of the second filter circuit.

[0025] The second end of the fifth resonant unit is connected to the output end of the second filter circuit.

[0026] The application adds a low-pass filter function by designing a BTM antenna unit, improves the port reflection coefficient of the antenna in the working frequency band, has very low harmonic energy radiation, greatly improves the matching ability of the BTM, improves the receiving signal capability, and improves the receiving effect in a complex electromagnetic environment.

[0027] The addition of the low-pass filter plate realizes that when the antenna radiates signals outward, the BTM cable signal can be radiated out in a large amount, the second harmonic, the third harmonic and the multiple harmonics of the BTM cable signal are reduced, and the requirements of relevant standards are more easily met, thereby reducing the requirements on the BTM cable signal. The low-pass filter plate has excellent port reflection coefficient, plays a "bridge" role in the matching connection between the BTM and the antenna, and improves the application range of the BTM antenna unit. In addition, by changing the circuit structure and the resonant unit, the signal processing performance of the antenna is further improved.

[0028] Other features and advantages of the present application will be described in the following description, and some will become apparent from the description, or will be learned by practice of the present application. The purposes and other advantages of the present application can be achieved and obtained by the structure indicated in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0030] Figure 1 A module structure schematic diagram of the low-harmonic radiation antenna unit according to the embodiment of the present application is shown;

[0031] Figure 2 A circuit structure schematic diagram of the low-pass filter plate according to the embodiment of the present application is shown;

[0032] Figure 3A simulation result diagram of a forward transmission coefficient of a first port of a low-pass filter plate according to an embodiment of the present application is shown;

[0033] Figure 4 A simulation result diagram of a reflection coefficient of a first port of a low-pass filter plate according to an embodiment of the present application is shown;

[0034] Figure 5 A network analyzer test result diagram of a circuit of a low-pass filter plate according to an embodiment of the present application is shown;

[0035] Figure 6 A schematic diagram of a positional relationship of a low-pass filter plate, an antenna main plate and an antenna transmitting plate according to an embodiment of the present application is shown;

[0036] Figure 7 A schematic diagram of a structure of a first resonator and a power isolation unit according to an embodiment of the present application is shown;

[0037] Figure 8 A schematic diagram of a circuit structure of an energy transmitting coil antenna according to an embodiment of the present application is shown;

[0038] Fig. 9(a) shows a smith chart under 50 ohm matching according to an embodiment of the present application;

[0039] Fig. 9(b) shows a smith chart under a port mismatch of 9.5 dB port reflection coefficient and an impedance value of 25.81 ohm according to an embodiment of the present application;

[0040] Fig. 9(c) shows a smith chart under a port open circuit state and an impedance of 0.8 ohm according to an embodiment of the present application;

[0041] Figure 10 A simulation result diagram of a reflection coefficient of a port of an antenna transmitting plate circuit according to an embodiment of the present application is shown;

[0042] Figure 11 A schematic diagram of a structure of a second filter circuit according to an embodiment of the present application is shown;

[0043] Figure 12 A simulation result diagram of a forward transmission coefficient of a second filter circuit according to an embodiment of the present application is shown;

[0044] Figure 13 A schematic diagram of a structure of an A4 interface signal filter circuit according to an embodiment of the present application is shown;

[0045] Fig. 14(a) shows a schematic diagram of a structure of a first energy decision circuit of an A4 interface signal decision circuit according to an embodiment of the present application;

[0046] Fig. 14(b) shows a structural diagram of a second energy decision circuit of an A4 interface signal decision circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0047] To make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely explain the technical solutions in the embodiments of the present application with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall into the scope of the present application.

[0048] The embodiments of the present application provide an antenna unit (referred to as an antenna unit hereinafter) with low harmonic radiation, as shown in Fig. 1. Figure 1 As shown in Fig. 1, the antenna unit comprises a first filter circuit, a power supply and trigger circuit, a logic control unit and a signal acquisition decision circuit.

[0049] The first filter circuit is arranged between an energy transmission ring of the antenna and a BTM, for reducing the harmonic radiation of the energy transmission ring.

[0050] One end of the power supply and trigger circuit is connected to an energy receiving ring, and the other end is connected to the logic control unit, for stabilizing the electric signal on the BTM cable and outputting a trigger signal to the logic control unit.

[0051] The signal acquisition decision circuit is used for acquiring the A4 interface signal, making a decision on the A4 interface signal, and outputting the decision result to the logic control unit.

[0052] The logic control unit is used for controlling the A4 interface signal acquisition and signal transmission according to the trigger signal and the decision result.

[0053] The antenna unit of the embodiments of the present application can suppress the harmonic by the first filter circuit, reduce the harmonic radiation, and more effectively transmit the signal energy, which is beneficial to enhancing the signal transmission capability. Meanwhile, the alarm and accurate signal acquisition are realized by the signal control relationship between the logic control unit and the signal acquisition decision circuit, and the stability of the antenna unit and the reliability of the signal analysis are improved.

[0054] The antenna unit further comprises a signal transmission circuit, one end of which is connected to the logic control unit, and the other end is connected to a D3 interface signal transmission ring. The logic control unit transmits the signal to the D3 interface signal transmission ring through the signal transmission circuit. The signal transmission circuit comprises an FSK output filter circuit, which is used for filtering the FSK signal to be transmitted.

[0055] The following will explain the modules and units of the antenna unit in detail.

[0056] The first filter circuit is a low-pass filter circuit, and is used to realize low-pass filtering of the BTM cable transmission signal. Figure 2 As shown in FIG. 1, the first filter circuit includes a first port D1, a second port D2, a third port D3 and a filter module. D1, D2 and D3 are realized by radio frequency sockets, and each port is packaged by five pins. The first pin (pin 1) in the middle is used as a connection port of the first filter circuit and other circuits, and the other four pins (pin 2, pin 3, pin 4 and pin 5) are grounded. The first end of the filter module is connected to D1, and the second end is connected to D2 and D3 respectively.

[0057] The filter module includes a first capacitor C1, a second capacitor C2, a third capacitor C3, a first inductor L1 and a second inductor L2. L1 and L2 are connected in series. The first end of L1 is used as the first end of the filter module, the second end of L1 is connected to L2, the first end of L2 is connected to the second end of L1, and the second end of L2 is used as the second end of the filter module.

[0058] The inductance values of L1 and L2 are the same, and are 270nH without loss of generality. C1, C2 and C3 are respectively connected to the two ends of the two inductors L1 and L2. Specifically, the first end of C1 is connected to the first end of L1, and the second end of C1 is grounded. The first end of C2 is connected to the second end of L1, and the second end of C2 is grounded. The first end of C3 is connected to the second end of L2, and the second end of C3 is grounded. The capacitance values of C1 and C3 are the same, and the capacitance value of C2 is n times the capacitance values of C1 and C3, n>1. Exemplarily, n is 4. Exemplarily, the capacitance values of C1 and C3 are 30pF, and the capacitance value of C2 is 120pF. The structure design of the first filter circuit of the embodiment of the present application can adjust the inductance and capacitance values to change the insertion loss of 27MHz in the band and the attenuation value at the harmonic point outside the band, and suppress the reflection coefficient and harmonic frequency of the D1 and D2 ports.

[0059] Further, the second end is connected to D3 through a fourth capacitor C4. Without loss of generality, the capacitance value of C4 is 10nF. C4 is used to filter out the direct current voltage. Specifically, one end connected to D2 is connected to the antenna mainboard 1. There is a direct current voltage in the line signal, and the direct current voltage can be isolated by the capacitor C4.

[0060] The first filter circuit in the above example is simulated and constructed Figure 2 The performance of the first filter circuit in the antenna unit is simulated, and the simulation result is shown in FIG. 2. Figure 3The simulation results of S(2, 1) (representing the positive transmission coefficient) show that the second harmonic suppression is 5.6 dB, the third harmonic suppression is 19.8 dB, the fourth harmonic suppression is 31.1 dB, the fifth harmonic suppression is 40.1 dB, and the sixth harmonic suppression is 47.6 dB. After adding a low-pass filter design in the antenna unit, the harmonic radiation can be reduced, and the antenna performance can be improved. The port reflection coefficient of the low-pass filter is -45 dB, which is well matched with the BTM cable, the antenna main board and the antenna sending board. The antenna can more effectively emit signal energy, which is conducive to enhancing the ability of signal emission.

[0061] As shown in Figure 4 , the simulation diagram of S(1, 1) (representing the D1 port reflection coefficient) / S22 (representing the D2 port reflection coefficient) shows that the port reflection coefficient of the low-pass filter is -45 dB, which is well matched with the BTM cable, the antenna main board and the antenna sending board. The antenna can more effectively emit signal energy, which is conducive to enhancing the ability of signal emission.

[0062] As shown in Figure 5 , the network analyzer test results show that the actual performance indicators of the low-pass filter board are close to the simulation values, and the expected design goal is achieved.

[0063] Preferably, the first filter circuit of the embodiment of the present application is arranged on a separate board card, which is referred to as a low-pass filter board 3 in the embodiment of the present application. That is, the first filter circuit is arranged on a board card different from the antenna main board 1 and the antenna sending board 2, as shown in Figure 6 . The D1 of the first filter circuit is connected with the BTM cable (i.e. the coaxial cable used for connecting the BTM), the D2 is connected with the signal port of the antenna main board 1, and the D3 is connected with the signal port on the antenna sending board 2. The BTM antenna adopts a PCB antenna, and in the embodiment of the present application, the energy receiving ring for receiving energy signals is arranged on the antenna main board 1, and at the same time, the power supply and the trigger circuit, the logic control unit and the signal acquisition and judgment circuit are also arranged on the antenna main board 1. The energy sending ring is arranged on the antenna sending board 2. The energy receiving ring and the energy sending ring are connected with the low-pass filter board through coaxial cables, specifically, the signal port of the energy receiving ring is connected with the D2 of the first filter circuit, and the signal port of the energy sending ring is connected with the D3 of the first filter circuit. The energy sending ring and the energy receiving ring are connected with the low-pass filter board through one port, and the three ports of the low-pass filter board are connected with the BTM, the energy sending ring and the energy receiving ring respectively.

[0064] As shown in Figure 7As shown, the antenna unit also includes a first resonator and a power isolation unit. The receiving end of the signal interface (also referred to as P4 port) of the antenna main board is connected to the first end of the energy receiving ring through the first resonator; the ground end of the signal interface of the antenna main board is connected to the second end of the energy receiving ring through the power isolation unit. Specifically, the P4 port adopts a radio frequency socket, including five pins, wherein the first pin (pin 1) is connected to the first resonator, and the remaining pins (pins 2, 3, 4, and 5) are grounded.

[0065] The power isolation unit includes a plurality of parallel capacitors, exemplarily including four parallel capacitors, including two 10nF capacitors and one 2.2nF capacitor. The power isolation unit is connected to the ground end of the coaxial cable. The 27MHz energy signal will pass through the power isolation unit into the first-stage transmitting coil (transmitting ring), and at the same time, the first-stage transmitting coil is also a receiving coil (energy receiving ring), and the 4MHz message signal is transmitted from the receiving coil to the BTM through the P4 port. The function of the power isolation unit is to isolate the direct current power supply. The first resonator includes a fifth capacitor C5 and a third inductor L3 in parallel, which are used to adjust the characteristic impedance parameter of the antenna and perform impedance matching. The antenna is designed as a wideband antenna to be able to receive signals within the frequency band occupied by the FSK message signal.

[0066] As shown in FIG. 4, the antenna on the antenna transmitting board is designed as two copper foils close to the edge of the board. Figure 8 As shown in FIG. 4, the antenna on the antenna transmitting board is designed as two copper foils close to the edge of the board.

[0067] Exemplarily, the energy transmitting ring coil includes a plurality of series resonant units and a first resistor. For example, it includes a first resonant unit, a second resonant unit, a third resonant unit, and a fourth resonant unit connected in series, wherein the second resonant unit and the fourth resonant unit are the same in structure and each include four parallel capacitors and an inductor connected in series with the capacitors. The first resonant unit and the third resonant unit are the same in structure and each include a plurality of (for example, four) parallel capacitors, at least one of which is an adjustable capacitor. One end of the signal interface (i.e., the signal interface of the antenna transmitting board) D1 of the energy transmitting ring is connected to the first resonant unit, and the other end is connected to the fourth resonant unit.

[0068] The energy transmitting ring coil is connected in series with the first resistor R1. Specifically, D1 is a radio frequency socket, which adopts a five-pin package. The first pin (pin 1) in the middle is connected to the resistor R1 through the PCB trace, and the nominal value of the resistance is 50 ohms, and the actual use is between 47 and 51 ohms. The power of R1 is not less than 20W. The other four pins (pins 2, 3, 4, and 5) of D1 are connected to the fourth resonant unit through the PCB.

[0069] The antenna transmitting board is matched with 50 ohms. The selection of 50 ohms: 1) the antenna is a standard 50 ohm transmission system, and the best transmission point is at 50 ohm impedance, at this time, on the Smith impedance circle, it is represented as a center point, far from the center point of the Smith circle represents the antenna mismatch state, at the outermost of the Smith circle, it represents that the antenna is in an open state, which is the most serious mismatch. Because the impedance of the entire PCB antenna itself is very small, an external resistance needs to be connected to form a 50 ohm transmission system. 2) the BTM signal amplitude is large, and the power reaches 20W, so the resistance needs to be selected as a high-power resistance to prevent burning. 3) considering the heat dissipation problem, a 50 ohm resistance with a grounding end is selected, and a heat sink is connected to dissipate heat.

[0070] The Smith circle under the 50 ohm matching is as shown in Fig. 9(a).

[0071] The Smith circle of the port mismatch at 9.5 dB port reflection coefficient and the impedance value at 25.81 ohms is as shown in Fig. 9(b).

[0072] The Smith circle of the port open state at the impedance of 0.8 ohms is as shown in Fig. 9(c).

[0073] The antenna transmitting board is directly connected with the BTM cable. The D1 port of the energy transmitting ring is connected with the D3 port of the low-pass filter board through a radio frequency cable. The advantage is that the signal from the BTM is directly processed by the filter and then transmitted through the antenna transmitting board, avoiding the signal being radiated to the antenna transmitting board through the antenna mainboard, thereby improving the signal transmission efficiency and enhancing the signal.

[0074] The embodiment of the application utilizes the excellent port reflection coefficient of the low-pass filter board to connect the BTM cable and the antenna transmitting board, so that the signal transmission is more efficient and smooth, and at the same time, the harmonic suppression function is also provided, so that the antenna signal out-of-band radiation is more perfect. At the same time, the in-band attenuation is small, so that more BTM output power is transmitted, and the efficiency is improved. Under the same conditions, the BTM can use lower power to achieve the same transmission effect and obtain the same action distance.

[0075] Figure 10 The simulation result diagram of the reflection coefficient of the port of the antenna transmitting board circuit according to the embodiment of the application is shown, and the reflection coefficient is -58.77 dB, which indicates that the antenna transmitting board and the low-pass filter board in front of it are well matched. Figure 1As shown, the power supply and trigger circuit includes a first voltage regulator circuit, a second voltage regulator circuit, a trigger pulse circuit, and a second filter circuit. The first voltage regulator circuit is a 3.3V regulator circuit, and the second voltage regulator circuit is a 1.8V regulator circuit. The input terminals of the power supply and trigger circuit are connected to a coaxial cable, and the output terminals provide a 3.3V regulated power supply, a 1.8V regulated power supply, and a trigger pulse. The 1.8V power supply is obtained through a 3V power converter, and the 3V power supply is obtained through a 24V power converter.

[0076] The 24V power supply and trigger pulse input are both provided to the power supply and trigger circuit via a coaxial cable. The coaxial cable also transmits energy signals, message signals, detection signals, and power signals. To isolate the high-frequency signals (energy signals and message signals) from the coaxial cable, a second filter circuit is used to isolate the signals before supplying power to the self-test circuit (not shown in the figure). The self-test circuit is used to verify whether the antenna is functioning correctly. This embodiment of the invention does not limit the implementation of the self-test circuit.

[0077] like Figure 11 As shown, the second filter circuit includes a fourth inductor L4, a fifth inductor L5, a sixth capacitor C6, and a seventh capacitor C7. The first terminal of the fourth inductor L4 is connected to the input terminal of the second filter circuit, and the second terminal of the fourth inductor L4 is connected to the first terminal of the fifth resonant unit. The fifth resonant unit includes the fifth inductor L5, the sixth capacitor C6, and the seventh capacitor C7 connected in parallel. The second terminal of the fifth resonant unit is connected to the output terminal of the second filter circuit. After the signal from the coaxial cable is filtered by the fourth inductor L4 and the fifth inductor L5, the detection signal and the power signal enter the self-test circuit and are then input to the first voltage regulator circuit and the trigger pulse circuit. The function of L4 and L5 is to attenuate the 27MHz signal from the BTM and the 4MHz signal from the transponder. Since the 4MHz signal has relatively weak energy, the attenuation of the 27MHz signal is the primary focus. The inductance value of L4 is 47uH, and the inductance value of L5 is 560nH, resulting in a 38dB attenuation of the 27MHz signal. L4 and L5 do not attenuate DC signals. The second terminal of the fifth resonant unit is grounded through the first diode for voltage clamping protection of the circuit. The first diode is a transient diode TVS1. The anode of the first diode is grounded, and the cathode is connected to the second end of the fifth resonant unit.

[0078] like Figure 12 As shown, the 4MHz signal and the 27MHz signal are attenuated by 22dB and 38dB respectively after passing through L4 and L5.

[0079] The logic control unit is used to control the acquisition and transmission of A4 interface signals based on trigger signals and decision results. In this embodiment of the invention, the logic control unit is implemented using a CPLD (Complex Programmable Logic Device). In other embodiments, other types of logic devices may also be used.

[0080] The logic control unit receives a trigger signal, specifically a trigger pulse, from a power supply and a pulse trigger circuit; the logic control unit receives a decision result signal from a signal collection and decision circuit, specifically including an energy high flag input signal (over high), an energy low flag input signal (over low) and an energy alarm flag input signal (zero); the logic control unit obtains an AD data input signal from the signal collection and decision circuit; the logic control unit outputs an AD control signal to the signal collection and decision circuit for controlling signal collection of the signal collection and decision circuit; the logic control unit outputs a self-check DDS control output signal (peripheral circuit of the CPLD, not shown in the figure). When the energy high flag input signal, the energy low flag input signal and the energy alarm flag input signal are all zero, the logic control unit outputs the AD control signal to the signal collection and decision circuit, controls the signal collection and decision circuit to collect the A4 interface signal, and obtains the A4 interface signal converted by the AD in the signal collection and decision circuit, that is, the AD data input signal.

[0081] The CPLD is provided with a clock by an external crystal oscillator, and in order to facilitate modulation of the FSK signal, a crystal oscillator with a frequency of 27.095MHz is used in the embodiment of the application.

[0082] The JTAG interface is used on the board to debug and program the CPLD.

[0083] The signal collection and decision circuit is used to collect the A4 interface signal, make a decision on the A4 interface signal, and output the decision result to the logic control unit, including an A4 interface energy decision circuit, an A4 interface energy collection circuit and an AD sampling circuit.

[0084] The first end of the A4 interface energy decision circuit is connected to the logic control unit, the second end is connected to the first end of the A4 interface energy collection circuit, the second end of the A4 interface energy collection circuit is connected to the energy pickup ring, the first end of the AD sampling circuit is connected to the logic control unit, and the second end is connected to the first end of the A4 interface energy collection circuit.

[0085] The A4 interface energy collection circuit is used to collect the A4 interface signal through the energy pickup ring. The A4 interface energy collection circuit inputs the collected A4 interface signal to the A4 interface energy decision circuit for decision, and the A4 interface energy decision circuit outputs the energy high flag input signal, the energy low flag input signal and the energy alarm flag input signal to the logic control unit according to the decision result of the collected A4 interface signal. The AD sampling circuit is realized by an AD chip, and is used to control the collection operation of the A4 interface energy collection circuit and perform data processing (AD conversion) on the obtained A4 interface signal. The CPLD drives the AD sampling chip by the AD control signal, and obtains the AD data signal.

[0086] As Figure 13As shown, the A4 interface signal is received by the energy pickup ring on the PCB antenna, and is input to the A4 interface signal energy collection circuit through the collection interface unit (P2). The A4 interface energy collection circuit includes a third filter circuit, a fourth filter circuit and a voltage division protection circuit connected in series. The first end of the third filter circuit is connected to the collection interface unit of the A4 signal, the second end is connected to the first end of the fourth filter circuit, the second end of the fourth filter circuit is connected to the first end of the voltage division protection circuit, and the second end of the voltage division protection circuit outputs voltage signals through two output interfaces.

[0087] The third filter circuit includes an eighth capacitor C8, a second resistor R2, a ninth capacitor C9 and a tenth capacitor C10. Wherein the first end of C8 is connected to the collection interface unit and the first end of R2, and the second end is grounded; the second end of R2 is connected to the first end of C9, and the second end of C9 is grounded; the first end of C10 is connected to the second end of R2, and the second end is connected to the first end of the fourth filter circuit. Exemplarily, C8 is 10P, R2 is 5.1O ohms, C9 is 220P, and C10 is 82P.

[0088] The fourth filter circuit includes a sixth inductor L6, an eleventh capacitor C11, a twelfth capacitor C12 and a thirteenth capacitor C13. Wherein C11 and C12 are connected in series and connected in parallel with L6. The first end of L6 is connected to the second end of C10, the second end of L6 is connected to the first end of C13, the second end of C13 is grounded and connected to the first end of the voltage division protection circuit. Exemplarily, C11 and C12 are 12P, L6 is 1uH, and C13 is 10P.

[0089] The voltage dividing protection circuit includes a first voltage dividing circuit and a second voltage dividing circuit, which are connected through two reverse connection diodes and output different voltage levels, i.e., a first voltage level and a second voltage level. The first voltage dividing circuit includes a third resistor R3 and a fourteenth capacitor C14. The second voltage dividing circuit includes a fourth resistor R4 and a fifteenth capacitor C15. The first voltage dividing protection circuit and the second voltage dividing protection circuit are connected through a first Schottky diode D1 (specifically, a BAT54A) and connected to the fourth filter circuit through the first Schottky diode. Specifically, the anode of the first Schottky diode is connected to the second end of the fourth filter circuit, i.e., one end of C13. The first cathode of the first Schottky diode is connected to the first voltage dividing protection circuit, specifically, the first cathode of the first Schottky diode is connected to the first end of R3 and the first end of C14, the second end of R3 is grounded, and the second end of C14 is grounded. The second cathode of the first Schottky diode is connected to the second voltage dividing protection circuit, specifically, the second cathode of the first Schottky diode is connected to the first end of R4 and the first end of C15. The second end of R4 is grounded, and the second end of C15 is grounded. The first end of C14 serves as the output end of the first voltage dividing circuit and outputs the first voltage level, and the first end of C15 serves as the output end of the second voltage dividing circuit and outputs the second voltage level. The resistance values of R3 and R4 are different, and the capacitance values of C14 and C15 are different. For example, R3 is not welded, R4 is 8K ohms, C14 is 100P, and C15 is 33P. When the output amplitude of level1 needs to be changed, R3 can be welded, and the amplitude of level1 can be adjusted by adjusting the value of R3 according to the actual situation of the circuit.

[0090] The signal received by the PCB antenna is filtered by the resonator to filter out signals of specific frequencies, and a direct current voltage signal is obtained after rectification and input to the A4 interface energy collection circuit.

[0091] The voltage signal output by the A4 interface energy collection circuit is sent to three magnetic flux judgment circuits composed of LM139, which respectively provide the state information that the energy of the A4 interface is too high, too low, or zero. When the outputs of the three judgment circuits are all 0, the energy is within the allowed range. The outputs of the three comparison judgments are sent to the logic control unit, which changes the state code according to the three input state lines and transmits the energy information of the channel to the BTM through the D3 interface.

[0092] The energy high and energy low judgment circuits are obtained by comparing with the set reference voltage, and the reference voltage of the two-way judgment is obtained by 3V voltage division. The reference voltage is adjusted so that the comparison threshold of the energy low is higher than the first threshold Φ1, and the comparison threshold of the energy high is lower than the second threshold Φ4.

[0093] The A4 interface energy decision circuit includes a first energy decision circuit and a second energy decision circuit, the first energy decision circuit is used for judging whether the first-stage voltage is in a specified range; and the second energy decision circuit is used for judging whether the second-stage voltage is zero-crossed.

[0094] As shown in FIG. 14(a), the first energy decision circuit includes a low threshold adjustment circuit, a first comparator, a high threshold adjustment circuit and a second comparator.

[0095] The first-stage voltage is input to a first input end of the first comparator and a second input end of the second comparator, the first comparator is used for judging whether the first-stage voltage is less than a first threshold value, and the second comparator is used for judging whether the first-stage voltage is greater than a second threshold value, wherein the first threshold value is less than the second threshold value. The first input end of the first comparator and the second input end of the second comparator are voltage clamped by a first clamping device to prevent the comparators from being burnt out. Exemplarily, the first clamping device is a second Schottky diode D2, specifically a BAT54S, which has two series-connected diodes inside. A third pin (i.e. the connection point of the two diodes) of the second Schottky diode is connected to the first input end of the first comparator and the second input end of the second comparator, a first pin (anode) of the second Schottky diode is grounded, and a second pin (cathode) of the second Schottky diode is connected to a power supply. Specifically, the power supply is a 3V power supply.

[0096] Exemplarily, the first comparator and the second comparator both adopt LM139DR. The first input end of the first comparator is a negative pin, and the second input end is a positive pin. The first input end of the second comparator is a negative pin, and the second input end is a positive pin.

[0097] The low threshold adjustment circuit is connected to the second input end of the first comparator, and is used for determining the first threshold value.

[0098] The low threshold adjustment circuit includes two groups of resistors, a first group of resistors is connected in parallel between a first voltage division node and a power supply, and a second group of resistors is connected in parallel between the first voltage division node and a ground. Specifically, the first group of resistors includes a fifth resistor R5, a seventh resistor R7 and a ninth resistor R9, the second group of resistors includes a sixth resistor R6, an eighth resistor R8 and a tenth resistor R10, and the first voltage division node is connected to the second input end of the first comparator through an adjusting resistor, i.e. a twelfth resistor R12. The adjusting resistor is used for adjusting the resistance values of the first group of resistors and the second group of resistors, so that a specified comparison voltage (the first threshold value) is obtained within a reasonable resistance value range. The low threshold adjustment circuit further includes a sixteenth capacitor C16, a first end of the sixteenth capacitor C16 is connected to the first voltage division node, and a second end of the sixteenth capacitor C16 is grounded, which is used for filtering out the interference in the power supply.

[0099] The second input terminal of the first comparator is connected to the output terminal of the first comparator through a resistor (thirteenth resistor R13), and the first comparator is configured to output an energy low flag input signal (LOW). When the input voltage (first-stage voltage) of the first energy decision circuit is less than the first threshold value, the energy low flag input signal outputs a high level (1), and otherwise outputs a low level (0). The output terminal of the first comparator is connected to a power supply (3V) through a fourteenth resistor R14.

[0100] The first energy decision circuit further comprises a fifth filter circuit connected between the power supply and the first voltage division node, configured to filter the ripple signal on the power supply side. The fifth filter circuit comprises a resistor (eleventh resistor R11) and a capacitor (seventeenth capacitor C17) connected in parallel.

[0101] The high threshold adjustment circuit is connected to the first input terminal of the second comparator, and is configured to determine the second threshold value.

[0102] The high threshold adjustment circuit comprises two groups of resistors, a third group of resistors connected in parallel between the second voltage division node and the power supply, and a fourth group of resistors connected in parallel between the second voltage division node and the ground. Specifically, the third group of resistors comprises a fifteenth resistor R15, a seventeenth resistor R17 and a nineteenth resistor R19, and the fourth group of resistors comprises a sixteenth resistor R16, an eighteenth resistor R18 and a twentieth resistor R20. The second voltage division node 8 is connected to the first input terminal of the second comparator. The high threshold adjustment circuit further comprises an eighteenth capacitor C18, with a first end connected to the second voltage division node and a second end grounded.

[0103] The second input terminal of the second comparator is connected to the output terminal of the second comparator through a resistor (twenty-second resistor R22), and the second comparator is configured to output an energy high flag input signal (HIGH). When the input voltage (first-stage voltage) of the first energy decision circuit is greater than the second threshold value, the energy high flag input signal outputs a high level (1), and otherwise outputs a low level (0). The output terminal of the second comparator is connected to a power supply (3V) through a thirty-third resistor R33.

[0104] The high threshold adjustment circuit is connected to the first input terminal of the second comparator, and is configured to determine the second threshold value.

[0105] Further, the input end of the first level voltage (LEVEL1) is connected with the first input end of the first comparator, and the input end of the first level voltage is connected with the second input end of the second comparator in series with the twenty-third resistor R23 and the twenty-first resistor R21. The R23 and R21 are respectively grounded through the nineteenth capacitor C19, the twenty-fourth resistor R24, the twentieth capacitor C20 and the twenty-fifth resistor R25. The combination of R23, R21, R24 and R25 makes the subsequent output direct current signal level value of level1 in a reasonable range. If the level is too high or too low, the resistance value of the first energy decision circuit will also affect the threshold accuracy. Therefore, through the above resistance adjustment, the subsequent output level of level1 can be ideally in the middle part of the minimum and maximum.

[0106] As shown in FIG. 14(b), the second energy decision circuit includes a third comparator, and a second level voltage (LEVEL2) is input to the first input end of the third comparator. The third comparator is used to determine whether the second level voltage is zero-crossing. If the second level voltage is zero-crossing, a warning signal (WARNING PULSE) is output. The zero-crossing in the embodiment of the present application refers to the degree that the energy cannot meet the measured quantity.

[0107] The second input end of the third comparator is connected with a fourth clamping device for voltage clamping to prevent the comparator from being burnt out. Exemplarily, the fourth clamping device is a fourth Schottky diode D4, specifically a BAT54S, which has two series diodes inside. The third pin (i.e. the connection point of the two diodes) of the D4 is connected with the second input end of the third comparator, the first pin (anode) of the D4 is grounded, and the second pin (cathode) of the D4 is connected with a power supply. Specifically, the power supply is a 3V power supply. The voltage drop of the diode of the D4 is used as a reference voltage for the energy warning determination. One end of the D4 is connected with +3V, the other end is grounded, and the middle is connected with the level2 input signal. When the voltage of the level2 is higher than 3.8V, the left diode is turned on, and the level2 is clamped at 3V, thereby protecting the subsequent circuit. Exemplarily, the third comparator uses LM139DR. The first input end of the third comparator is a negative pin, and the second input end is a positive pin.

[0108] The first input terminal of the third comparator is connected to a power supply (3V) through a twenty-sixth resistor R26. The first end of R26 is connected to the power supply, and the second end of R26 is connected to the first input terminal of the third comparator. The first input terminal of the third comparator and R26 are grounded through a twenty-first capacitor C21. The first end of C21 is connected to the second end of R26, and the second end of C21 is grounded. The first input terminal of the third comparator is connected to a third clamping device for voltage clamping, and the power supply voltage is clamped at a specified low voltage (for example, 0.21V) as a reference signal, which is compared with the signal from the “+” pin of the LM139DR (the signal from level 2) to make a judgment. Exemplarily, the third clamping device can be a diode, and the cathode of the diode is grounded, and the anode of the diode is connected to the second end of R26. The third clamping device can also be a third Schottky diode D3, specifically a BAT54S, which has two series-connected diodes inside. The first pin (anode) of D3 is connected to the first input terminal of the third comparator, the third pin (the connection point of the two diodes) of D3 is grounded, and the second pin (cathode) of D3 is left floating.

[0109] The output terminal of the third comparator is connected to the power supply (3V) through a twenty-seventh resistor R27, and is connected to the second input terminal of the third comparator through a thirtieth resistor R30.

[0110] The second-level voltage is input to the second input terminal of the third comparator through a twenty-eighth resistor R28 and a twenty-ninth resistor R29 connected in series. That is, the first end of R28 is connected to the input terminal of the second-level voltage, and the second end of R28 is connected to the first end of R29. The first end of R29 is connected to the first end of R28, and the second end of R29 is connected to the second input terminal of the third comparator. The connection points between R28 and R29 are respectively grounded through a twenty-second capacitor C22 and a thirty-first resistor R31. That is, the second end of R28 is connected to the first end of C22, and the second end of C22 is grounded. The second end of R28 is connected to the first end of R31, and the second end of R31 is grounded.

[0111] The combination of R28, R29, R30, and R31 makes the subsequent output DC signal level value of level 2 within a reasonable range. If the level is too high or too low, the values of other resistors in the second energy decision circuit will also affect the threshold accuracy. Therefore, through the above resistance adjustment, the subsequent output level of level 2 can be ideally within the middle part of the minimum and maximum.

[0112] Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions described in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and such modifications or replacements 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 application.

Claims

1. An antenna element with low harmonic radiation, characterized in that, The low harmonic radiation antenna unit comprises: a first filter circuit, the first filter circuit is arranged between an energy transmitting ring of an antenna and a BTM, and is used for low-pass filtering of a BTM cable transmission signal, so as to reduce harmonic radiation of the energy transmitting ring; the first filter circuit is arranged on a separate board different from an antenna main board and an antenna transmitting board; wherein a first port of the first filter circuit is connected with the BTM cable; a second port is connected with a signal port of the antenna main board; and a third port is connected with a signal port on the antenna transmitting board; the first filter circuit comprises a first port, a second port, a third port and a filter module; a first end of the filter module is connected with the first port; and second ends of the filter module are respectively connected with the second port and the third port; the filter module comprises a first capacitor, a second capacitor, a third capacitor, a first inductor and a second inductor; the first inductor and the second inductor are connected in series; a first end of the first inductor is used as a first end of the filter module; a second end of the first inductor is connected with the second inductor; a first end of the second inductor is connected with the second end of the first inductor; and a second end of the second inductor is used as a second end of the filter module; a first end of the first capacitor is connected with the first end of the first inductor; a second end of the first capacitor is grounded; a first end of the second capacitor is connected with the second end of the first inductor; a second end of the second capacitor is grounded; a first end of the third capacitor is connected with the second end of the second inductor; and a second end of the third capacitor is grounded.

2. The low harmonic radiation antenna unit according to claim 1, wherein a fourth capacitor is connected between the second end of the filter module and the third port.

3. The low harmonic radiation antenna unit according to claim 1, wherein the antenna unit further comprises a first resonator and a power isolation unit; a receiving end of a signal interface of the antenna main board is connected with a first end of an energy receiving ring through the first resonator; a grounding end of the signal interface of the antenna main board is connected with a second end of the energy receiving ring through the power isolation unit; the power isolation unit is used for isolating a direct current power supply; the first resonator is used for adjusting a characteristic impedance parameter of the antenna, and performing impedance matching.

4. The low harmonic radiation antenna unit according to claim 3, wherein the power isolation unit comprises a plurality of capacitors connected in parallel.

5. The low harmonic radiation antenna unit according to claim 3, wherein the first resonator comprises a fifth capacitor and a third inductor connected in parallel.

6. The low harmonic radiation antenna unit according to any one of claims 1-5, wherein the energy transmitting ring comprises a plurality of resonant units connected in series and a first resistor; the first resistor is a resistor with a nominal value of 50 ohms and a grounding end; the power of the resistor is not less than 20 W; and the resistor is cooled through an external heat sink.

7. The low harmonic emission antenna element of any of claims 1-5, wherein, The low harmonic radiation antenna unit further comprises a second filter circuit, the second filter circuit is used for isolating a high-frequency signal of the BTM cable from a backward power supply and a trigger circuit.

8. The low harmonic radiation antenna unit according to claim 7, wherein the second filter circuit comprises a fourth inductor, a fifth inductor, a sixth capacitor and a seventh capacitor; a first end of the fourth inductor is connected with an input end of the second filter circuit; a second end of the fourth inductor is connected with a first end of a fifth resonant unit; the fifth resonant unit comprises the fifth inductor, the sixth capacitor and the seventh capacitor connected in parallel. The second end of the fifth resonant unit is connected with the output end of the second filter circuit; The second end of the fifth resonant unit is connected with the output end of the second filter circuit;

Images