Design of special monitoring antenna for GPS interference

Abstract

The invention designs a special monitoring antenna for GPS interference, and is suitable for the field of radio monitoring. The antenna system is composed of a PCB yagi antenna array, a bridge combiner, a band-pass filter and a low-noise amplifier, and the design aims at remarkably improving the receiving precision and the anti-interference capability of GPS L1 frequency band signals. The yagi antenna array is arranged in a 2 * 2 structure, the signal gain in the main direction is enhanced through the phase superposition technology, and meanwhile interference in the secondary direction is effectively restrained. The bridge combiner ensures phase consistency of the signals and impedance matching of the system, and the band-pass filter is used for filtering adjacent channel interference and enhancing the purity of the received signals. And the low-noise amplifier further amplifies the weak signal, keeps a low noise coefficient and ensures the signal quality. The antenna system has a compact structural design, can provide excellent interference monitoring and signal direction finding capabilities in a complex environment, is particularly suitable for cities, mountainous areas and high-interference scenes, and has a wide industrial application value.

Description

Technical Field

[0001] The present invention relates to the field of radio monitoring, in particular to a high-performance radio frequency monitoring front end for GPS signal monitoring, which is mainly composed of a PCB Yagi antenna array, a dedicated bridge combiner, a filter and a low noise amplifier. The present invention focuses on improving the reception accuracy and anti-interference ability of GPS L1 frequency band signals, and is particularly suitable for use in interference-intensive environments. Background Art

[0002] The Global Navigation Satellite System (GNSS) has been widely used in many key areas. However, due to the low power characteristics of GNSS signals, they are susceptible to external interference, especially in environments with dense electromagnetic interference sources, the reception quality and positioning accuracy of GNSS signals will be significantly reduced. For example, densely built-up areas in cities, mountainous areas, and military interference environments may cause the performance of GNSS positioning systems to be greatly reduced. Existing monitoring equipment has problems such as insufficient sensitivity and low direction-finding accuracy when detecting weak interference signals, which has prompted the demand for RF monitoring front-ends with high gain, high purity, and excellent direction-finding performance. Summary of the invention

[0003] The present invention aims to solve the deficiencies in the prior art and provide a high-performance GPS signal monitoring antenna array and its radio frequency monitoring front end, which can significantly improve the detection and direction finding capabilities of weak GPS interference signals. The antenna array is manufactured using printed circuit board (PCB) technology and consists of multiple optimized Yagi antenna units, which are matched with a dedicated bridge combiner, filter and low noise amplifier to achieve efficient reception and processing of GPS L1 frequency band signals; through the design of the present invention, the directional gain, signal purity and anti-interference capability of the system can be greatly improved, providing reliable technical support for GNSS monitoring.

[0004] Yagi Antenna Unit Design The Yagi antenna unit of the present invention is designed for the GPS L1 frequency band (1575.42 MHz) and is manufactured using printed circuit board (PCB) technology. The antenna unit includes a driving vibrator, a reflecting vibrator and two guiding vibrators, such as Figure 1As shown, its structural features are as follows: driving vibrator (1): 9.5 cm in length, it is the main radiation unit of the antenna, responsible for receiving and sending signals; reflecting vibrator (3): 20 cm in length, located on one side of the driving vibrator, plays a role in suppressing the signal transmitted from the back, thereby improving the directivity of the antenna; guiding vibrator (2): 8.3 cm in length, located on the other side of the driving vibrator, used to enhance the reception capability of the front signal; In order to achieve high performance of the antenna unit, the antenna material is selected from Rogers high-frequency board, whose low dielectric loss and high conductivity ensure the transmission stability of high-frequency signals; the outer copper thickness is 2.5 ounces to enhance the signal transmission performance; the spacing between the reflecting vibrator and the driving vibrator is set to 3.5 cm, and the spacing between the driving vibrator and the guiding vibrator is 3.8 cm to achieve 50Ω impedance matching; experimental results show that this design can effectively optimize the performance of the antenna; the input end of the antenna adopts SMA female connector (4), and a fixing screw hole is reserved at the tail end for easy installation and fixation.

[0005] Yagi Antenna Array Design In order to further improve the receiving gain and directivity, the present invention designs an array consisting of four Yagi antenna units, such as Figure 2 As shown. The array antenna uses the interference effect to enhance the signal in the main direction and attenuate the signal in the secondary direction through the phase superposition of multiple radiating units. Specifically, the array antenna adopts a 2×2 structure arrangement, and the center spacing between antenna units is 20cm to ensure the maximum gain in the main beam direction; the array antenna is fixed on a U-shaped acrylic bracket, which can effectively support the stability of the antenna array and reduce the impact of external vibration on the antenna performance; the antenna unit and the combiner are connected by SMA silver-plated RF cables to ensure the stability and consistency of signal transmission.

[0006] Design of bridge type RF combiner The present invention designs a special bridge type RF combiner, which is mainly used to combine the signals of multiple antenna units into one output signal, such as Figure 3 The combiner is composed of two 2-in-1 same-frequency bridge combiners, and the input ports (5) are bridged by a 50-ohm (6) resistor to ensure impedance matching of the system; the circuit layout of the combiner is strictly symmetrical to eliminate the phase difference of the signal and ensure the consistency and purity of the output signal; Figure 5 As shown, the antenna unit and the combiner are connected through SMA silver-plated RF connecting wires, and the lengths of the RF connecting wires between the four antenna units and the combiner are strictly equal to avoid the introduction of phase errors due to differences in the lengths of the RF connecting wires.

[0007] The output end (7) of the bandpass filter's selection combiner is connected to a GPS-specific bandpass filter (9) via an SMA silver-plated RF cable; the filter is a frequency selection circuit that only allows signals within a specific frequency band to pass through, and suppresses and attenuates signals in other frequency bands. Its main functions are: improving signal purity, effectively reducing interference from adjacent frequency signals, and improving the purity of received signals; enhancing anti-interference capability, by suppressing signals from high-power adjacent frequency stations, thereby enhancing the system's anti-interference capability; reducing intermodulation interference, and weakening intermodulation interference signals generated inside the receiver; The present invention uses a low-loss GPS SAW filter, which has the characteristics of low insertion loss, high isolation, and small size, making it an ideal choice for high-precision GPS signal monitoring.

[0008] The output end of the bandpass filter is connected to the low noise amplifier (LNA) (10) through an SMA silver-plated RF cable. The LNA is responsible for amplifying the weak signal received by the antenna and minimizing the noise and distortion introduced during the amplification process. The key performance indicators of the LNA include the noise figure and the third-order input cutoff point. To ensure the high performance of the system, the present invention adopts a high-performance LNA chip produced by a domestic company, and refers to relevant design examples to design the output, input and bias circuits for the present invention, such as Figure 4 .

[0009] Component fixing and layout design In order to achieve the compactness and practicality of the overall design, the bandpass filter (9) and LNA (10) are fixed side by side under the acrylic bracket, and the two output ports are protruding from the lower edge of the bracket to facilitate connection with subsequent instrument equipment; according to application requirements, when the bandpass filter is directly connected to the instrument equipment, the system is in passive antenna mode; if the bandpass filter is connected to the LNA and then connected to the instrument equipment, the system is in active antenna mode, which is suitable for different application scenarios; when switching to active antenna use, it is necessary to equip it with a battery with a voltage of 3-5V, which can be fixed to the inside of the acrylic bracket by tape to facilitate power supply for the LNA; in order to realize the portable use of the antenna, a lightweight handle (11) is installed above the combiner (8). Since the antenna is lightweight as a whole and has a low overall center of gravity, the antenna naturally faces forward after being held, which helps to save effort during walking monitoring. Example

[0010] In order to verify the actual performance of the present invention, the present invention has produced a sample antenna array and carried out detailed tests on it, such as Figure 6 As shown in the figure, the test environment covers densely built-up areas in cities, open areas in suburbs and complex terrain in mountains, simulating the GPS signal reception conditions under different interference intensities and environmental conditions.

[0011] In an urban environment, test results show that the antenna array of the present invention can effectively improve the reception strength of weak GPS signals, especially when the GPS signal is interfered by building reflections and multipath effects. The antenna array can still maintain high directivity and gain, reducing the positioning error by about 20%.

[0012] In the suburban test, the antenna array showed excellent anti-interference ability. In the environment of simulated strong interference sources (such as telecommunications base stations and broadcast transmission towers), the high selectivity of the bandpass filter effectively suppressed the adjacent frequency spurious interference signals and maintained the purity of the GPS signal. Through the synergy of the filter and LNA, the antenna array can still provide stable signal output under moderate interference intensity, ensuring that the monitoring equipment can continue to capture and process GPS interference signals.

[0013] In mountain tests, the antenna array demonstrated good signal acquisition capabilities and environmental adaptability. In conditions of complex terrain and where signals are easily obstructed, the antenna array was able to effectively capture weak GPS signals. The filter further removed interference signals, and the LNA ensured that the signal strength met subsequent processing requirements. Even in extreme environments (such as deep valleys or areas with many obstacles), the direction-finding error of the antenna array was only about 2 degrees.

[0014] In addition, we have conducted special tests for interference at different frequencies, such as Figure 7 As shown, the results show that the standing wave ratio of the design of the present invention is always kept below 1.9 in the working frequency band of 1570-1582MHz, indicating that the antenna has good impedance matching and frequency selection characteristics. In practical applications, the present invention can effectively detect extremely low-power interference signals, and its interference detection sensitivity is improved by about 30%.

[0015] In general, the sample antenna array and RF monitoring front end of the present invention perform well in various complex environments, especially in strong interference environments, and can still maintain high GPS signal reception accuracy and reliability. These test results verify the feasibility and superior performance of the present invention in actual radio monitoring tasks.

Claims

1. A design for a dedicated monitoring antenna for GPS interference, suitable for the field of radio monitoring, its features include the following: (1) PCB Yagi antenna array, the array is composed of multiple Yagi antenna units, each Yagi antenna unit includes a driving vibrator, a reflecting vibrator and a guiding vibrator, the Yagi antenna units are arranged in a 2×2 structure, and the phase superposition technology is used to enhance the signal gain in the main direction and effectively suppress the interference in the secondary direction; (2) dedicated bridge RF combiner, the combiner is used to combine the signals of multiple Yagi antenna units into one input signal, and through impedance matching and phase consistency design, the integrity and stability of the signal are guaranteed; (3) bandpass filter, the filter is used to filter adjacent frequency signals, enhance the purity of the received signal, and improve the anti-interference ability of the monitoring system; (4) low noise amplifier (LNA), the LNA is used to amplify the received weak signal while maintaining a low noise coefficient to ensure high-quality signal transmission.

2. The GNSS interference monitoring antenna according to claim 1, characterized in that: Each Yagi antenna unit in the PCB Yagi antenna array is manufactured using printed circuit board (PCB) technology. The material of the Yagi antenna unit is Rogers high-frequency board, and has low dielectric loss and high conductivity; the length of the reflection vibrator of the Yagi antenna unit is 20 cm, the length of the driving vibrator is 9.5 cm, the length of the guide vibrator is 8.3 cm, the spacing between the reflection vibrator and the driving vibrator is 3.5 cm, and the spacing between the driving vibrator and the guide vibrator is 3.8 cm. The relevant design ensures that the unit antenna impedance is 50Ω; a fixing screw hole is reserved at the tail end of the Yagi antenna unit, as shown in Figure 1.

3. The monitoring antenna according to claim 1, characterized in that: The array is composed of multiple Yagi antenna units, which are arranged in a 2×2 structure with a spacing of 20 cm and are fixed on a U-shaped acrylic bracket through reserved holes, as shown in FIG2 .

4. The monitoring antenna according to claim 1, characterized in that: The bridge RF combiner is composed of two 2-in-1 same-frequency bridge combiners, and the input ports are bridged by a 50-ohm resistor to achieve impedance matching of the system, as shown in FIG3 .

5. The monitoring antenna according to claim 1, characterized in that: The antenna system fixes the filter and the low-noise amplifier side by side under the acrylic bracket. Both output ports protrude from the lower edge of the bracket to facilitate connection with subsequent instrument equipment. The specific layout is shown in Figure 5.

6. The monitoring antenna according to claim 1, characterized in that: The antenna system has switchable active and passive antenna modes, which are switched by connecting or disconnecting a low noise amplifier (LNA) to adapt to different application scenarios.

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