Application of lithium niobate - RF filter

Lithium niobate (LiNbO3) is an important crystal material with excellent optical, electrical and acoustic properties. It is widely used in optical communication, optical sensing, optical storage, optical computing, optical modulation and other fields. In the RF field, lithium niobate is also widely used ADE7755ARS Preparation of RF filter. This paper will introduce the application of lithium niobate in RF filters in detail.

1、 Basic properties of lithium niobate

Lithium niobate is a single crystal material with orthogonal crystal system. Its lattice constant is a=5.148 b=5.148?、c=13.863?， The crystal cell contains three lithium niobate molecules. Lithium niobate has high hardness (7.5 Mohs hardness) and can maintain good stability at higher temperatures. In addition, lithium niobate has a large electro-optic effect (r33=32pm/V) and piezoelectric effect (d33=27pC/N), which can be used to prepare optical waveguides and piezoelectric sensors.

2、 Preparation method of lithium niobate RF filter

RF filter refers to the electronic device used for modulation, demodulation, amplification, separation, multiplexing and other RF signal processing. In the preparation of RF filters, lithium niobate is mainly used in surface acoustic wave (SAW) filters and microwave surface acoustic wave (MSSW) filters.

1. SAW Filter

Surface acoustic wave filter is a device that can filter and selectively amplify RF signals by using the characteristics of surface acoustic wave propagation on the crystal surface. Lithium niobate, as a crystal material, has good surface acoustic wave propagation performance and can be used to prepare high-performance SAW filters.

A common method to prepare SAW filters is to deposit metal electrodes on the surface of lithium niobate wafer by photolithography, and then prepare electrode structures on lithium niobate wafer by electron beam evaporation or magnetron sputtering. Then, SAW propagation channels are fabricated on the wafer by using photolithography and ion beam etching. Finally, the chip is packaged into a filter device through external electrodes and packaging technology.

2. Microwave surface acoustic wave filter (MSSW Filter)

Microwave SAW filter is a device that uses the propagation characteristics of microwave SAW in lithium niobate crystal materials to filter RF signals. Compared with SAW filter, MSSW filter has higher operating frequency and better frequency selection performance.

A common method to prepare MSSW filters is to prepare a series of microwave SAW propagation channels on the surface of lithium niobate chips, and prepare input and output electrodes on both sides of the channels. Then, the microwave SAW propagation channels are fabricated on the wafer by photolithography and ion beam etching. Finally, the chip is packaged into a filter device through external electrodes and packaging technology.

3、 Performance advantages of lithium niobate RF filter

Lithium niobate RF filter has the following performance advantages:

1. High selectivity: lithium niobate crystal has excellent surface acoustic wave and microwave surface acoustic wave propagation characteristics, which can achieve high selectivity filtering function. This makes lithium niobate filter have a good application prospect in RF signal processing.

2. Wide bandwidth range: lithium niobate crystal has a wide operating frequency range, which can meet the RF signal processing requirements in different frequency ranges.

3. Low insertion loss: lithium niobate filter has low insertion loss, which can achieve efficient RF signal processing.

4. Small size: The lithium niobate filter has a small size, which is convenient for integration and packaging, and can meet the requirements of high-density integrated circuits.

4、 Application fields of lithium niobate RF filters

Lithium niobate RF filters have been widely used in communication, radar, satellite navigation, radio spectrum analysis, radio spectrum monitoring and other fields. Specific applications include:

1. RF filter in communication system: lithium niobate filter can be used in wireless communication system to filter and selectively amplify RF signals in different frequency bands.

2. RF filter in radar system: lithium niobate filter can be used in radar system to filter and selectively amplify radar signals in different frequency bands.

3. RF filter in satellite navigation system: lithium niobate filter can be used in satellite navigation system to filter and selectively amplify navigation signals of different frequency bands.

4. RF filter in radio spectrum analysis and monitoring: lithium niobate filter can be used in radio spectrum analysis and monitoring to filter and selectively amplify radio signals in different frequency bands.

5、 Development Trend of Lithium Niobate RF Filters

With the rapid development of communication technology and the increasing shortage of radio spectrum resources, the performance of RF filters is required to be higher and higher. As an important RF filter material, lithium niobate filter has better performance advantages, but there are also some challenges.

1. High frequency applications: With the high frequency of RF technology, lithium niobate filters need to adapt to a higher operating frequency range.

2. Low insertion loss: RF filters require lower insertion loss, and lithium niobate filters need to further improve their performance.

3. Size reduction: As the size of electronic devices continues to shrink, the lithium niobate filter needs to further reduce its size and improve its integration.

4. Broadband application: With the development of wireless communication technology, the demand for broadband RF filters is growing, and lithium niobate filters need to adapt to a wider working band.

In a word, as an important crystal material, lithium niobate has a broad application prospect in RF filters. With the continuous development of radio frequency technology and communication technology, lithium niobate filters will continuously improve their performance and be applied in more fields.