5G anti-jamming satellite communication filter

1. Background introduction

As the country announced the frequency bands used for 5G: China Telecom obtained 5G test frequency resources with a bandwidth of 3400MHz-3500MHz and a total bandwidth of 100MHz; China Mobile obtained 5G test frequency resources in the frequency bands of 2515MHz-2675MHz and 4800MHz-4900MHz. Among them, the frequency bands of 2515-2575MHz, 2635-2675MHz and 4800-4900MHz are new frequency bands. The frequency band of 2575-2635MHz is the existing TD-LTE (4G) frequency band of China Mobile; China Unicom obtained 5G test frequency resources with a bandwidth of 3500MHz-3600MHz and a total bandwidth of 100MHz.

Since 2019, terrestrial mobile operators in China and other countries have begun testing and large-scale deployment of 5G base stations. However, the spectrum used by 5G overlaps with the C-band (3400-4200MHz, 4500-5000MHz) that has long been used for satellite communication services. To eliminate interference, engineering solutions need to be given.

2. Program introduction

The low-noise put-down frequency conversion module (LNB) routinely used in satellite receiving systems has only limited frequency selection capabilities. The 5G carrier is mainly located in the 3400-3600MHz and 4800-4900 MHz frequency bands, still within the input frequency range of the LNB. Considering that the power level of the 5G carrier may be much higher than the received satellite signal, it will cause interference to the satellite receiving system:

A) Co-frequency interference, that is, the satellite carrier and the 5G carrier frequency band overlap;

B) Adjacent frequency interference, that is, the satellite carrier is adjacent to the frequency band of the 5G carrier. Satellite signals are subject to deterioration of 5G spectrum regeneration and interference from out-of-band spurious emissions;

C) LNB saturation interference, that is, the high-power 5G carrier pushes the operating point of the LNB to the saturation or nonlinear region. The received satellite carrier signal of all C-band will suffer distortion or even be robbed of power.

Co-frequency interference: 5G base stations and satellite earth stations require a certain protection distance to avoid interference from 5G signals to satellite earth stations.

Both adjacent frequency interference and LNB saturation interference can be eliminated by satellite communication filters.

An ideal satellite communication filter is installed at the LNB input, capable of protecting the satellite carrier in the passband while suppressing the 5G carrier outside the passband. After using this filter, the 5G carrier transmitted by the adjacent channel cannot easily push the LNB to saturation or deteriorate it. However, in practice the design and production of such a BPF is not easy: First, the filter's in-band insertion loss will increase the total noise temperature of the receiving system and reduce the link margin. Second, the suppression level of the filter's out-of-band determines the distance that the satellite earth station can coexist with the 5G base station. Third, the in-band and out-of-band characteristics of the filter need to be weighed. The higher the out-of-band rejection, the greater the in-band insertion loss. Finally, the 5G frequency bands in different countries may be different.

3. Product indicators

According to the requirements of domestic and foreign customers, Chengdu Senesed Technology Co., Ltd. has developed two standard types of satellite communication filters. For different passband frequencies and out-of-band suppression requirements, our company can also customize the development.

The following are the specifications for two standard models of satellite communication filters:

A) 3700-4200MHz satellite communication filter

Model: 7-4.2 GW-2678

Technical indicators:

Interpolation loss: ≤ 0.8dB;

Standing wave: ≤ 1.3;

Suppression:≥70dBc@3400-3600MHz，≥70dBc@4300-4900MHz

Size: Length 120mm

B) 3625-4200MHz satellite communication filter

Model BPF3.0 625-4.2 GW-2680

Technical indicators:

Interpolation loss: ≤0.35dB

Standing wave: ≤1.2；

Suppression: ≥70dB@3400-3500MHz; ≥63dB@3500-3600MHz;≥70dB@4800-5000MHz

Size: 108*98.5*70mm

Weight: 560g

Other features: the surface spray three anti-paint, waveguide port with a sealing ring, with waterproof function.