Terahertz space angle filter
By designing a terahertz spatial angle filter for hollow core cylindrical waveguide and terahertz transmitter/receiver in the terahertz frequency band, using Fabry-Perot resonance and Talbot effect, the complex and cost-effective traditional filter design is solved, and efficient and flexible frequency selective filtering is achieved.
Patent Information
- Application Number
- CN202411769646.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-04
- Publication Date
- 2025-03-28
AI Technical Summary
Traditional terahertz band filters have problems with complex design, high cost and tunability limitations, making them difficult to meet the dynamic needs of the terahertz band.
A terahertz spatial angle filter is designed, using a hollow core cylindrical waveguide, a terahertz transmitter and receiver. Through Fabry-Perot resonance and Talbot effect, flexible frequency adjustment and all-round uniform filtering are achieved.
High-efficiency frequency selective filtering within a specific exit angle range is realized, which enhances the flexibility and selectivity of filtering, reduces production costs, and increases market potential.
Smart Images
Figure CN119726021A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of terahertz regulation and control, and in particular to a terahertz space angle filter. Background Art
[0002] Terahertz waves usually refer to electromagnetic waves with frequencies in the range of 0.1THz-10 THz. Due to its advantages such as instantaneity, broadband, coherence, and penetration into non-polar substances, terahertz technology is widely used in many fields such as medicine, biology, materials science, chemistry, military defense, and security inspection.
[0003] The terahertz band is considered to be the core band of future 6G communication technology, but compared with other mature bands, many related issues are still under exploration. Traditional circuit filters and optical filters are usually complex in design, expensive to manufacture, and have great limitations in adjustability, making it difficult to meet the dynamic requirements of the terahertz band. This lack of flexibility in design limits their effectiveness in practical applications. Therefore, it is particularly important to develop an efficient and low-cost terahertz filter. Summary of the invention
[0004] In response to the above-mentioned terahertz frequency band filtering problem, a terahertz spatial angle filter is proposed. By optimizing the design and material selection, it can achieve flexible frequency adjustment and reduce production costs, thereby greatly improving its market potential in terahertz applications.
[0005] The technical solution of the present invention is: a terahertz spatial angle filter, comprising a hollow cylindrical waveguide, a terahertz transmitter and a receiver at both ends of the hollow cylindrical waveguide, the broadband terahertz wave emitted by the terahertz transmitter is grazingly incident on the input end of the hollow cylindrical waveguide, Fabry-Perot resonance is generated in the waveguide, the terahertz wave oscillates and outputs in the hollow cylindrical waveguide, the terahertz receiver rotates to receive terahertz light at different exit angles, and specific frequencies in the broadband terahertz wave are filtered out at specific angles, thereby achieving the effect of frequency selective filtering.
[0006] Preferably, the terahertz transmitter and receiver use photoconductive antennas, and two terahertz focusing lenses are installed at the transmitting end and the receiving end of the terahertz transmitter and the receiver respectively along the terahertz transmitting path and the receiving path, so as to jointly realize the transmission and reception of linearly polarized terahertz signals.
[0007] A method for calculating the filtering frequency range of a terahertz space angle filter is disclosed. For the terahertz space angle filter, a ray model is established according to the Talbot effect in a waveguide, the emission angle range is calculated, and then the filtering frequency range is determined according to the relationship between the filtering frequency f and the terahertz wave emission angle α.
[0008] Furthermore, the ray model is:
[0009]
[0010] where α max , α min are the maximum and minimum emission angles of the terahertz wave, respectively, L is the length of the hollow cylindrical waveguide, and D is the diameter of the hollow cylindrical waveguide.
[0011] Furthermore, the relationship between the filtering frequency f and the terahertz wave emission angle α is as follows:
[0012]
[0013] Where c is the speed of light in vacuum.
[0014] The beneficial effects of the present invention are as follows: the terahertz spatial angle filter of the present invention, by combining Fabry-Perot resonance and Talbot effect, can realize efficient frequency selective filtering within a specific range of emission angles, which not only enhances the flexibility and selectivity of filtering, but also utilizes the symmetry of the hollow cylindrical waveguide within the range of 360° to realize all-round uniform filtering, which not only improves the utilization of space and angle, but also simplifies the operation process. In addition, the filter proposed by the present invention has the advantage of selecting the filtering frequency according to the emission angle, highlighting its high utilization rate in spatial angle selection, and is expected to provide convenience for a variety of terahertz applications and promote the progress of related technologies. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is a schematic diagram of the filtering frequency of the radial cross section of a cylindrical waveguide incident at different angles at the same frequency based on Fabry-Perot resonance of the present invention;
[0016] Figure 2 The light path diagram of the radial cross section in the cylindrical waveguide under N=2 reflections based on the Talbot effect of the present invention is shown;
[0017] Figure 3 It is a diagram of the experimental device of the present invention;
[0018] Figure 4 This is an experimental data diagram of the output angle and filtering frequency under two reflections in a cylindrical waveguide with a diameter of 10 mm and a length of 140 mm according to the present invention. DETAILED DESCRIPTION
[0019] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.
[0020] A terahertz spatial angle filter. When a broadband terahertz wave is incident on the input end of a hollow cylindrical waveguide, a Fabry-Perot resonance is generated in the waveguide, and the terahertz wave oscillates and outputs in the waveguide to filter out a specific frequency at a specific angle, thereby achieving a frequency selective filtering effect. In addition, based on the Talbot effect in the waveguide, the terahertz wave's exit angle range can be calculated, thereby determining the filtering frequency range.
[0021] like Figure 1 As shown in the figure, when the terahertz wave of the same frequency is incident on the hollow cylindrical waveguide at three different angles α1, α2, and α3, Fabry-Perot resonance will be generated in the hollow cylindrical waveguide. In this process, the terahertz wave oscillates and outputs in the waveguide, and the frequency incident at angle α2 is filtered out (the incident angle is the same as the exit angle). The relationship between the filter frequency f and the terahertz wave exit angle α is as follows:
[0022]
[0023] Where c is the speed of light in a vacuum and D is the diameter of the hollow cylindrical waveguide.
[0024] like Figure 2 As shown in the figure, a Q point is assumed as a terahertz emission source, which emits a light beam to the hollow cylindrical waveguide, which is transmitted in the waveguide and finally reaches the receiving end. The length of the hollow cylindrical waveguide is defined as L, the diameter is defined as D, the angle between the light beam and the waveguide wall is α, and the waveguide axis is along the Z direction, coaxial with the terahertz source.
[0025] Based on the Talbot effect, a ray model was established, such as Figure 2 By analyzing the geometric relationship, the minimum and maximum emission angles α of the terahertz wave corresponding to different reflection times are calculated. min , α max The relationship between the number of reflections N of the terahertz wave in the hollow cylindrical waveguide is as follows:
[0026]
[0027] Wherein L is the length of the hollow cylindrical waveguide, and D is the diameter of the hollow cylindrical waveguide.
[0028] exist Figure 2 In the figure, a ray model constructed when the number of reflections N = 2 is shown. The model depicts the path of the terahertz wave incident from point Q, after two reflections in the waveguide, at the maximum and minimum exit angles respectively. Points Q1 and Q2 represent the intersection of the reverse extension lines of the first and second reflected rays with the plane of the waveguide input end, respectively. Figure 2 When the terahertz wave is emitted from the lower edge of the waveguide, the maximum emission angle α is shown in (a). max ; Figure 2 When the light is emitted from the upper edge of the waveguide as shown in (b), the minimum emission angle α min .
[0029] like Figure 3 The experimental device diagram shown shows the terahertz transmitter and receiver modules. The device uses a photoconductive antenna (TERA15-RX-FC-MENLO) as a terahertz transmitter and receiver. Two terahertz focusing lenses (TPX) are installed on the transmitter and receiver along the terahertz transmission path and the receiving path, respectively, to jointly realize the transmission and reception of linearly polarized terahertz signals. We made a hollow cylindrical waveguide (D = 10mm (diameter), L = 140mm (tube length)) and placed it between the terahertz transmitter and the receiver. In this experiment, the receiver is rotated to receive terahertz light at different emission angles.
[0030] like Figure 4 As shown in Figure 1, we compared the experimental data of the hollow cylindrical waveguide with the theoretical calculation results. First, we used formula (2) to calculate the theoretical output angle range of the waveguide under 2 reflections, and the result was 3.6° to 7.8°. Then, we substituted these angle values into formula (1) and calculated the theoretical filtering frequency range to be 0.23THz to 0.48THz. This theoretical calculation result is Figure 4 Indicated by the blue line.
[0031] During the experiment, the terahertz light at different emission angles was received by rotating the receiving end. This method can accurately measure the filter frequency within the emission angle range of 3.6° to 7.8°. The experimental results show that within this angle range, the measured filter frequency range is 0.25THz to 0.43THz. The experimental results are compared with the theoretical calculation results. Figure 4 It can be clearly seen that the experimental data is basically consistent with the theoretical calculation. This result more strongly confirms that the hollow cylindrical waveguide can filter out signals of a specific frequency at a specific angle, verifying the effectiveness of its filtering function.
[0032] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.
Claims
1. A terahertz spatial angle filter, characterized in that: It includes a hollow cylindrical waveguide, a terahertz transmitter and a receiver at both ends of the hollow cylindrical waveguide. The broadband terahertz wave emitted by the terahertz transmitter is grazingly incident on the input end of the hollow cylindrical waveguide, Fabry-Perot resonance is generated in the waveguide, and the terahertz wave oscillates and outputs in the hollow cylindrical waveguide. The terahertz receiver rotates to receive terahertz light at different output angles, and specific frequencies in the broadband terahertz wave are filtered out at specific angles, thereby achieving the effect of frequency selective filtering.
2. The terahertz spatial angle filter according to claim 1, characterized in that: The terahertz transmitter and receiver use photoconductive antennas, and two terahertz focusing lenses are installed on the transmitting end and receiving end of the terahertz transmitter and receiver respectively along the terahertz transmitting path and receiving path, so as to realize the transmission and reception of linearly polarized terahertz signals.
3. A method for calculating the filtering frequency range of a terahertz spatial angle filter, characterized in that: For the terahertz spatial angle filter described in claim 1 or 2, a ray model is established based on the Talbot effect in the waveguide, the emission angle range is calculated, and then the filtering frequency range is determined based on the relationship between the filtering frequency f and the terahertz wave emission angle α.
4. The method for calculating the filtering frequency range of a terahertz spatial angle filter according to claim 3, characterized in that: The ray model is: where α max , α min are the maximum and minimum emission angles of the terahertz wave, respectively, L is the length of the hollow cylindrical waveguide, and D is the diameter of the hollow cylindrical waveguide.
5. The method for calculating the filtering frequency range of a terahertz spatial angle filter according to claim 4, characterized in that: The relationship between the filtering frequency f and the terahertz wave emission angle α is as follows: Where c is the speed of light in vacuum.