Introduction
Motivation of this research
Mode generator …
Gaussian beam
Circular fluted horn is shown in figure 4.4. The inner surface of the waveguide is periodically repeated by a series of corrugated structure. The effect on the attachment of the λ/4 fluted tapered section was investigated and the geometry considered in the simulation is shown in Fig. The whole structure is set in aluminum and using Gaussian beam of the excitation and a radiation boundary structure.
First, the aperture of the cavity is larger, measuring the beam pattern at the aperture would be easier. The distance between the horn opening and the probe was changed to as close as 1 mm. The E-field distribution has been scanned directly at the exit of the cavity in vertical polarization.
The electric field pattern at the cavity exit is investigated for backpropagation. Meixner, "Large Aperture Parabolic Mirror as an Imaging Device for Confocal Microscopy", International Online Journal of Optics, Vol.
Theory of mode generator
Corrugated feed horn
- Hybrid modes
- Gaussian-like beam of a corrugated waveguide
- Gaussian modes
The TM and TE modes, which are the direct equivalent of the wave equation inside a smooth circular waveguide, are the fundamental modes in a circular waveguide. However, if the waveguide is wavy, it could also be useful to define the field inside the smooth circular waveguide with hybrid modes EH and HE. In fact, we can therefore decide to define the field inside the wave horn antenna in terms of TE and TM modes or in terms of HE and EH modes [15].
But actually, this mode mixing is not perfect, (99.2% efficient with HE1.1 mode), the perfect mode mixing in terms of smooth wave modes, assuming the hybrid state can be seen in the table. It is well known that one of the best ways to determine a free-space radiation from an antenna is by means of paraxial free-space mode radii, Gaussian modes, which are a solution of the paraxial free-space equation [ 20]. 𝑘 ∙ 𝑤0)2 (2.7) It is also important to check the similarity between the fundamental Gaussian mode and the HE1.1 mode in an aperture of a given diameter.
Mirror system
- Parabolic Mirror
- Elliptic mirror
And the distances from the two focal points F1 and F2, denoted R1 and R2 respectively, to a point p on the surface are related to. We define θi to be the angle of incidence of the ray with respect to the local surface normal and consider an ellipse used to bend the ray in the x, z plane.
Cavity
- Electromagnetic fields of a cavity
Due to limited computer resources (Table 3-1) and runtime, we used symmetry of the structure. The wall with a thickness of 0.2 mm is made and the size of the holes is λ/3 diameter. A short length of the entire structure had confirmed that the desired pattern was shown by simulation.
The measurement is very sensitive to the experimental condition such as alignment, coupling of the cavity and unwanted interception of reflected rays. The intensity is low at the inner bar position of the center, the radial axis is likewise the desired mode pattern. The measurement is very sensitive to the experimental condition such as alignment, coupling of the cavity, and unwanted interception of reflected beam.
This mode generator is successfully designed to perform low-power verification of the quasi-optical system for a W-band 𝑇𝐸62 mode. Gyrotron Oscillators", in partial fulfillment of the requirements for the degree of Doctor of Philosophy at MIT.
Design and experiment of a mode generator
Design and experiment of a corrugated feed horn
It excites a mixture of TE11 and TM11 mode content which has an E-field distribution similar to the HE11 mode and forms Gaussian-like beams. For low-loss transmission, the desired ripple mode of operation is the HE11 mode [26, 27]. The frequency for the simulation is set to be in the W band where the geometrical parameters such as depth (d), pitch (p), width (w) and thickness (t) are defined accordingly.
After measuring the beam generated from the corrugated inlet horn, we compared it with the simulation results obtained with the HFSS program. Based on this, the total length of the corrugated feeder horn is 129 mm, and the radius at the horn opening is 16 mm [40]. The whole structure was made of aluminum and using wave coupling excitation and symmetrical boundary structure.
An electric beam pattern is converted from the 𝐻𝐸11 mode to a Gaussian-like beam pattern at the horn opening, which is confirmed by simulation results. To check the simulation result, the field pattern of the horn antenna was measured. An Agilent PNA-X N5247A was connected to a W-band corrugated power horn and an open waveguide probe.
Where W(z) is the radius after the wave has propagated a distance z, Wo is the radius of 1/e2 where the wavefront is flat and z is the distance propagated from the plane distance. Based on this, one can confirm that the expected beam size will be injected into the cavity.
Design and experiment of a mirror
Each directional component was analyzed separately to determine Gaussian beam size as the beam propagates. As shown in figure 3-11, the beam center of the fluted feed horn is 6 mm (radius). Due to limited computing resources and runtime, we used limited geometric size by applying symmetry.
A beam reflected from the mirror propagates into the cavity and we want to control the desired beam size. One can check measurement results such as the elliptical mirror of the x-axis and the parabolic mirror of the y-axis. Each directional component was analyzed separately to determine the Gaussian beam size as the beam propagates.
The measurement results of beam reflected from mirror agree well with calculations and simulations. The measurement results of beam reflected from mirror agree well with calculations and simulations.
Design and experiment of a cavity
- Comparison between counter clockwise and clockwise
- Inserting an inner rod in a cavity
- Changing the measurement distance
- Two mirror system of a mode generator
The requirements to provide good coupling are selected by the diameter of the holes and the thickness of the wall. Due to complex structures of the cavity, we divided two kinds of simulations, such as upward cut and coupling simulation. When the incident wave is injected on the inner surface of the cavity, the results differ from the way it is taken, such as anti-clockwise or clockwise.
We thought that an inner rod is used in a coaxial cavity to improve the mode purity. We define a function called a 1D error function, calculated by the difference results of the CST 𝐸𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒(𝑖) and measurement data 𝐸𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑚𝑒 𝑎𝑠𝑢𝑟𝑒𝑚𝑒𝑛𝑡( 𝑖) at each point as the error function is shown in figure. However, due to proximity, this must be controlled. Each structure and one mirror system undergo interference such as cavity coupling, misalignment and unwanted interception of the reflected beam.
3-37, the mirror curvature can be determined by matching the incoming Gaussian beam with the reflected Gaussian beam using Eq. The measurement takes considerable time because the measurement is so sensitive to the alignment, position and unwanted interceptions of the beams. Carter, "Electromagnetic Field of a Gaussian Beam with an Elliptical Cross Section", Journal of the optical Society of America, Vol.
Ramon Gonzalo, Jorge Teniente and Carlos del Rio, "Gaussian profiled horn antennas", On The Determination of The Phase Center of Gaussian, 1996. Martin, "Corrugated horn antenna for low-power testing of the quasi-optical transmission lines at TJ-II stellarator , ” Int.
