Calibration device and calibration method for an active rod antenna

Abstract

This application discloses a calibration device and method for an active rod antenna, relating to the field of antenna calibration. The device includes a metal shielding housing and a resistive T-network module and a capacitor integrated within the metal shielding housing. The resistive T-network module simulates the input impedance of the active rod antenna, and the capacitor simulates the distributed capacitance. When the input RF interface is connected to a standard signal source, the output RF interface is connected to a spectrum analyzer, and the ground terminal is connected to the active antenna host, the antenna factor of the active rod antenna is calculated by measuring the first signal strength at the output RF interface and the second signal strength at the output port of the active antenna host, thus completing the calibration. This application enables portable, accurate, and efficient calibration of active rod antennas.

Description

Technical Field

[0001] This application relates to the field of antenna calibration, and in particular to a calibration device and calibration method for an active rod antenna. Background Technology

[0002] Active rod antennas are widely used for electromagnetic radiation interference measurement and field strength detection in the 9kHz~30MHz frequency band. Their key parameters, such as antenna coefficient and input impedance, directly determine the accuracy and reliability of signal reception and detection. However, during long-term use, the antenna's electrical parameters can drift due to factors such as changes in ambient temperature, component aging, and power supply system losses, leading to performance degradation. Therefore, periodic calibration is necessary.

[0003] Currently, the main calibration methods for active rod antennas include the standard field method and the standard antenna method. These methods have drawbacks such as high equipment cost, large footprint, complex and time-consuming calibration process, and sensitivity to environmental electromagnetic noise. Furthermore, they cannot achieve online calibration and cannot meet the needs of rapid on-site calibration. Summary of the Invention

[0004] The purpose of this application is to provide a calibration device and method for active rod antennas, which can achieve portable, accurate and efficient calibration of active rod antennas.

[0005] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a calibration device for an active rod antenna, comprising: a metal shielding housing and a resistor-T network module and a capacitor integrated within the metal shielding housing; The metal shielded housing is equipped with an input RF interface, an output RF interface, and a grounding terminal; the input terminal of the resistor T-type network module is connected to the input RF interface, and the output terminal of the resistor T-type network module is connected to the output RF interface; one end of the capacitor is connected to the resistor T-type network module, and the other end of the capacitor is connected to the grounding terminal. The resistor T-type network module is used to simulate the input impedance of the active rod antenna, and the capacitor is used to simulate the distributed capacitance of the active rod antenna. When the input RF interface is connected to a standard signal source, the output RF interface is connected to a spectrum analyzer, and the ground terminal is connected to the active antenna host, the antenna factor of the active rod antenna is calculated by measuring the first signal strength at the output RF interface and the second signal strength at the output port of the active antenna host, thus completing the calibration.

[0006] Secondly, this application provides a calibration method utilizing the aforementioned calibration apparatus for active rod antennas, comprising: Power off the active antenna host, install the calibration device onto the active antenna host, and connect the grounding terminal of the calibration device to the grounding point of the active antenna host; Connect the standard signal source to the input RF interface of the calibration device and the spectrum analyzer to the output RF interface of the calibration device, and record the first signal strength read by the spectrum analyzer. Disconnect the spectrum analyzer from the output RF interface of the calibration device, connect the spectrum analyzer to the output port of the active antenna host, connect the load to the output RF interface of the calibration device, turn on the active antenna host, and record the second signal strength read by the spectrum analyzer. The antenna factor of the active rod antenna is calculated based on the first and second signal strengths to complete the calibration.

[0007] According to the specific embodiments provided in this application, this application has the following technical effects: This application integrates a resistor-type T-network module and a capacitor within a metal shielded housing, resulting in a compact structure and small size. It eliminates the need for large calibration equipment, significantly reducing calibration costs and floor space. The metal shielded housing effectively shields against external electromagnetic interference, solving the problem of traditional calibration methods being sensitive to environmental noise. By simulating the input impedance of an active rod antenna with the resistor-type T-network module and the distributed capacitance of the antenna with the capacitor, the electrical characteristics of the antenna can be accurately reproduced. Only a standard signal source and a spectrum analyzer are needed; the antenna factor can be calculated by measuring and comparing the signal strengths at two points. The calibration process is simple and time-saving, enabling rapid on-site and online calibration. This meets the periodic calibration requirements for antenna parameter drift in practical applications, ensuring the accuracy and reliability of active rod antenna measurements. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 A schematic diagram of the functional modules of a calibration device for an active rod antenna provided in an embodiment of this application; Figure 2 This is a circuit diagram of a resistor-T network module and a capacitor. Detailed Implementation

[0010] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0011] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0012] In one exemplary embodiment, such as Figure 1 As shown, a calibration device for an active rod antenna is provided, including: a metal shielding housing 1 and a resistor T-type network module 2 and a capacitor 3 integrated within the metal shielding housing 1.

[0013] The metal shielding housing 1 is provided with an input RF interface 11, an output RF interface 12, and a grounding terminal 13. The input terminal of the resistor T-type network module 2 is connected to the input RF interface 11, and the output terminal of the resistor T-type network module 2 is connected to the output RF interface 12; one end of the capacitor 3 is connected to the resistor T-type network module 2, and the other end of the capacitor 3 is connected to the grounding terminal 13.

[0014] Among them, the resistor T-type network module 2 is used to simulate the input impedance of the active rod antenna, and the capacitor 3 is used to simulate the distributed capacitance of the active rod antenna. When the input RF interface 11 is connected to the standard signal source 4, the output RF interface 12 is connected to the spectrum analyzer 5, and the ground terminal 13 is connected to the active antenna host 6, the antenna factor of the active rod antenna is calculated by measuring the first signal strength at the output RF interface 12 and the second signal strength at the output port of the active antenna host 6, thus completing the calibration.

[0015] Furthermore, the metal shielding housing 1 is made of rounded rectangular aluminum alloy, with dimensions of approximately 56mm × 48mm × 27mm. The surface undergoes a brushed, natural-colored anodizing treatment, with rounded edges to improve grip and prevent stress concentration and scratches from sharp corners. The metal shielding housing 1 features a top-and-bottom mating design, secured with countersunk screws around the bottom, facilitating the assembly and maintenance of internal circuit boards and components while ensuring good electromagnetic shielding performance. The sides of the metal shielding housing 1 are equipped with BNC RF interfaces marked "Input" and "Output" (i.e., input RF interface 11 and output RF interface 12). An M6 copper conductive threaded terminal (i.e., conductive threaded terminal 13) with an insulating bushing extends from the bottom of the metal shielding housing 1, covered with copper threads, for connecting to the active antenna host 6. Copper nuts are used to ensure grounding performance, reduce contact resistance, and effectively reduce potential difference and interference. An insulating bushing is provided on the outside of the conductive threaded terminal to prevent short circuits and ensure electrical isolation. The grounding terminal 13 is fixed to the metal shielding housing 1 by a crimped metal ring, which makes it easy to carry and prevents loss.

[0016] Furthermore, such as Figure 2As shown, the resistor T-type network module 2 consists of three high-precision thin-film resistors with low temperature coefficient and low parasitic inductance forming a T-type topology, namely the first resistor R1, the second resistor R2 and the third resistor R3.

[0017] One end of R1 is soldered to the input RF interface 11, and the other end is connected to one end of R2, one end of R3, and one end of capacitor 3. This connection point is called the center node. Figure 2 Node C in the diagram.

[0018] The other end of R2 is soldered to the output RF interface 12.

[0019] The other end of R3 is connected to the grounding terminal 13.

[0020] The resistance values ​​of R1, R2, and R3 are carefully selected to ensure that the input and output terminals present a characteristic impedance match of 50Ω within the target frequency band, guaranteeing stable transmission of RF signals and reducing reflection loss.

[0021] Furthermore, capacitor 3 is a mica capacitor C1. One end of C1 is connected in series with the resistor T-type network module 2 through node C, and the other end is directly connected to the ground terminal 13 from inside the housing. The mica capacitor has extremely high stability, and its self-resonant frequency can reach the GHz level, which is far higher than the 30MHz upper limit of this device's operation. It can cover the 9kHz~30MHz frequency band and can accurately simulate the distributed capacitance of an active rod antenna, ensuring calibration accuracy.

[0022] The working principle of resistor T-type network module 2 and capacitor 3 is as follows: Impedance matching: R1, R2, and R3 form a resistor T-type network, which, together with C1 for high-frequency shunt, optimizes the input and output impedance within the target frequency band and reduces signal reflection.

[0023] Low-frequency level attenuation: In the 9kHz-1MHz frequency band, the capacitive reactance of C1 is extremely high, almost open-circuit, and the circuit is a purely resistive network. A fixed 1 / 3 attenuation is achieved for low-frequency signals, used for level matching or signal amplitude calibration, while maintaining the signal phase essentially unchanged.

[0024] Intermediate frequency bandwidth limitation: In the 1MHz-10MHz frequency band, C1 and R3 are connected in parallel. The output amplitude decreases as the frequency increases, and the phase begins to lag, forming a first-order low-pass filter, which gradually suppresses signals above 1MHz, realizes bandwidth control, and the response of the analog antenna decreases in the high-frequency band.

[0025] High-frequency noise filtering: In the 10MHz-30MHz frequency band, the capacitive reactance of C1 is extremely small, almost short-circuited, and the potential of node C is clamped. The output amplitude decays rapidly at a slope of 20dB per decade, and the phase approaches -90°. This effectively filters out high-frequency noise and interference, avoids high-frequency signal reflection or crosstalk, ensures the integrity of low-frequency signals, and also simulates the failure or low sensitivity characteristics of a real rod antenna in the high-frequency band.

[0026] In an exemplary embodiment, a calibration method using the above-described calibration apparatus for an active rod antenna is provided, comprising the following steps: S1: Install the calibration device onto the active antenna host.

[0027] Disconnect the power to the base of the active antenna host 6. Insert the mounting studs on the back of the calibration device into the mounting holes on the top of the active antenna host 6, and rotate the calibration device to tighten it, ensuring a secure mechanical connection. Connect the grounding terminal 13 of the calibration device to one of the balance support mounting screws of the active antenna host 6 to achieve reliable grounding.

[0028] S2: Connect the standard signal source to the input RF interface of the calibration device, connect the spectrum analyzer to the output RF interface of the calibration device, and record the first signal strength read by the spectrum analyzer.

[0029] Connect the standard signal source 4 (used to output a standard RF excitation signal with traceable amplitude and frequency) to the input RF interface 11 of the calibration device. Connect the spectrum analyzer 5 to the output RF interface 12 of the calibration device. Connect a 50Ω load to the BNC output port of the active antenna main unit base.

[0030] Set the standard signal source parameters as follows: start frequency 9kHz, stop frequency 30MHz, step size can be set according to requirements (e.g., 100 points), and output power -60dBm.

[0031] Configure the spectrum analyzer parameters as follows: Set the resolution bandwidth (RBW) to 100Hz and the sweep width (SPAN) to 5kHz.

[0032] Start the scan and record the signal strength values ​​read by the spectrum analyzer 5 at each frequency point, denoted as P1 (unit: dBm). This step measures the standard signal strength after attenuation by the calibration device.

[0033] S3: Disconnect the spectrum analyzer from the output RF interface of the calibration device, connect the spectrum analyzer to the output port of the active antenna host, connect the load to the output RF interface of the calibration device, turn on the active antenna host, and record the second signal strength read by the spectrum analyzer.

[0034] Disconnect the spectrum analyzer 5 from the output RF interface 12 of the calibration device. Move the input cable of the spectrum analyzer 5 to the BNC output port of the active antenna host 6 base. Connect a 50Ω load to the output RF interface 12 of the calibration device. Turn on the power switch of the active antenna host 6 base to put it into normal operation. Keep the standard signal source settings unchanged (frequency and power as above). Start the scan and record the signal strength value read by the spectrum analyzer 5 at each frequency point, denoted as P2 (unit: dBm). This step measures the signal strength of the active antenna host 6 after receiving the antenna signal simulated by the calibration device, and then amplifying and processing it internally.

[0035] S4: Calculate the antenna factor of the active rod antenna based on the first signal strength and the second signal strength to complete the calibration.

[0036] The formula for calculating the antenna factor is: AF = P1 - P2 - C + D; Where AF is the antenna factor, P1 is the first signal strength, P2 is the second signal strength, C is the correction parameter with an equivalent height of 0.5m, and D is the voltage divider coefficient. In this embodiment, C=-6dB and D=5dB.

[0037] This calibration device is compact, portable, easy to operate, highly resistant to interference, and offers high calibration accuracy. It can meet the antenna coefficient calibration requirements of rod antennas in the 9kHz~30MHz frequency band in both laboratory and field environments. This device uses circuitry to replace electromagnetic waves in the air, eliminating the need for an anechoic chamber, a transmitting antenna, or antenna disassembly. Measurements can be performed entirely in the laboratory or on a desktop, solving problems such as high interference, complex calibration procedures, long processing times, low accuracy, and inability to perform online calibration in existing methods. It also simplifies the calibration process, reduces calibration costs, and is suitable for various calibration scenarios in both laboratories and the field.

[0038] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0039] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A calibration device for an active rod antenna, characterized in that, include: Metal shielding housing and resistor T-type network module and capacitor integrated within the metal shielding housing; The metal shielded housing is equipped with an input RF interface, an output RF interface, and a grounding terminal; the input terminal of the resistor T-type network module is connected to the input RF interface, and the output terminal of the resistor T-type network module is connected to the output RF interface; one end of the capacitor is connected to the resistor T-type network module, and the other end of the capacitor is connected to the grounding terminal. The resistor T-type network module is used to simulate the input impedance of the active rod antenna, and the capacitor is used to simulate the distributed capacitance of the active rod antenna. When the input RF interface is connected to a standard signal source, the output RF interface is connected to a spectrum analyzer, and the ground terminal is connected to the active antenna host, the antenna factor of the active rod antenna is calculated by measuring the first signal strength at the output RF interface and the second signal strength at the output port of the active antenna host, thus completing the calibration.

2. The calibration device for an active rod antenna according to claim 1, characterized in that, The resistor-T network module includes a first resistor, a second resistor, and a third resistor; One end of the first resistor is connected to the input RF interface, and the other end of the first resistor is connected to one end of the second resistor, one end of the third resistor, and one end of the capacitor, respectively. The other end of the second resistor is connected to the output RF interface; The other end of the third resistor is connected to the ground terminal.

3. The calibration device for an active rod antenna according to claim 1, characterized in that, The capacitors are made of mica; the resonant frequency of the mica capacitors covers the frequency band from 9kHz to 30MHz.

4. The calibration device for an active rod antenna according to claim 1, characterized in that, The metal shielding shell has an upper and lower interlocking structure, and the surface of the metal shielding shell has undergone a brushed and natural-colored oxidation treatment.

5. The calibration device for an active rod antenna according to claim 1, characterized in that, Both the input and output RF interfaces are BNC RF interfaces.

6. The calibration device for an active rod antenna according to claim 1, characterized in that, The grounding terminal is a conductive threaded terminal extending from the bottom of the metal shielding housing, and an insulating bushing is provided on the outside of the conductive threaded terminal.

7. The calibration device for an active rod antenna according to claim 1, characterized in that, The grounding terminal is fixed to the metal shielding housing by a crimped metal ring.

8. A calibration method using the calibration apparatus for an active rod antenna according to any one of claims 1 to 7, characterized in that, include: Install the calibration device onto the active antenna main unit; Connect the standard signal source to the input RF interface of the calibration device, connect the spectrum analyzer to the output RF interface of the calibration device, and record the first signal strength read by the spectrum analyzer. Disconnect the spectrum analyzer from the output RF interface of the calibration device, connect the spectrum analyzer to the output port of the active antenna host, connect the load to the output RF interface of the calibration device, turn on the active antenna host, and record the second signal strength read by the spectrum analyzer. The antenna factor of the active rod antenna is calculated based on the first and second signal strengths to complete the calibration.

9. The line calibration method according to claim 8, characterized in that, The formula for calculating the antenna factor is: AF = P1 - P2 - C + D; Where AF is the antenna factor, P1 is the first signal strength, P2 is the second signal strength, C is the correction parameter for the equivalent height, and D is the voltage division coefficient.

10. The line calibration method according to claim 8, characterized in that, The standard signal source has a start frequency of 9kHz, a stop frequency of 30MHz, and an output power of -60dBm; the spectrum analyzer's resolution bandwidth is set to 100Hz, and the sweep width is set to 5kHz.

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