The working principle of X-band filters in different application fields is mainly based on their frequency selection characteristics (passing signals in a specific frequency band and suppressing other frequency bands). Still, the particular implementation methods and optimization targets vary depending on the application scenario:
1. Radar system
Working principle
The high-resolution characteristics of the X-band (8~12 GHz) filter make it widely used in scenarios such as synthetic aperture radar (SAR) and weather radar.
- Target detection
The target echo signal is separated from the ground clutter through a bandpass or high-pass X-band filter (such as a cutoff frequency of 8 GHz); for example, the improved CMD algorithm uses the zero-speed characteristics of ground clutter for dynamic suppression.
- Anti-interference
Use a cavity or microstrip structure (such as Hairpin type) to achieve a steep roll-off (such as 100 dB suppression) to avoid interference from adjacent frequency bands.
- Example parameters
Insertion loss is ≤0.5 dB in the passband of 7.25~8.4 GHz; some designs use spherical resonators to improve the unloaded quality factor.
2. Satellite communication
Working principle
Mainly used to separate uplink and downlink (7.25~7.75 GHz reception/7.9~8.4 GHz transmission):
- Intermodulation suppression
High-order pseudo-elliptic technology can reduce intermodulation products between sub-bands (such as 75 dB suppression) to avoid signal distortion.
- Anti-rain attenuation
The stability of the X-band filter relies on high-pass filtering (such as suspended stripline design) to reduce the impact of bad weather.
- Terminal optimization
Portable devices use LTCC technology to achieve lightweight (such as BSC design with insertion loss ≤0.5 dB).
3. Meteorological and ocean monitoring
Working principle
Optimize signal processing for dynamic environments:
- Clutter filtering
X-band filter smoothes the differential propagation phase (ΦDP) to improve the accuracy of precipitation estimation.
- Noise suppression
The improved median filter algorithm in marine radar can retain effective grayscale information; The signal-to-noise ratio is significantly improved.
Reference:
1. X-Band Bandpass Filter Supplier | Cavity Filter for Radar Systems Manufacturer. [2016-04-22]
2. X-Band High Pass Filter | C, X, Ku & Ka Band filters for Satcom and Radar. AWG Tech. [2017-01-19]
4. SATCOM 365-01. BSC. [2022-12-08]
5. Attenuation Correction of Reflectivity for X-Band Dual Polarization Radar. Hui Xiao et al.
6. Filters in Radar Receivers [2024-03-27]
7. How Can RF Microwave Filters Work in Radar Systems?. Temwell Corporation. [2021-04-09]
8. N. Bharadwaj, V. Chandrasekar et al. "Signal Processing System for the CASA Integrated Project I Radars." Journal of Atmospheric and Oceanic Technology.