KR20110100708A - Optimal mode transmit method for branch duct of wireless network using air conditioning duct - Google Patents

Abstract

The present invention relates to a technique for setting a feeding position to excite an optimal propagation mode to a small diameter duct constituting the end of a duct network when constructing a wireless network using a duct.

Description

Optimal Mode Transmit Method for Branch Duct of Wireless Network using Air Conditioning Duct}

  This technology is a field for building an in-building wireless network using air conditioning ducts, and it is a technology that can transmit radio waves to maintain an even reception level in the duct of the terminal connected to the diffuser. It is deeply related to propagation analysis such as propagation characteristics of duct, transmission mode of feeder and Ray high frequency approximation.

The air conditioning duct acts as a kind of waveguide, so the transmission speed, impedance and branching characteristics are different for each transmission mode. Since the purpose is to have the optimum propagation distribution characteristics by installing the feeder at an appropriate position according to the structure of the duct, it is a basic background technology to analyze the propagation characteristics in the waveguide. In addition, when the size of the waveguide is very large compared to the wavelength, it is easy to analyze the propagation mode by using ray theory because it is difficult to grasp the physical characteristics according to the position of the feeder because the transmission mode is too large. This technique uses a combination of two analysis methods depending on the size of the duct. Since branch ducts with smaller apertures have a limited number of transmission modes, modal analysis is applied. For large ductile main ducts, a 2-ray approximation model is used to analyze the distribution characteristics of the electromagnetic field.

The air conditioning duct network is a structure in which a diffuser is connected to a branch duct branched vertically from a main duct that crosses a section of a building to supply air. In this case, when feeding the main duct, a difference in reception level may occur between the duct branched near the feeding point and the branched duct far away. Therefore, it is necessary to reduce such a difference in order to construct a wireless network with an even reception level in the whole space of a building.

The present invention is a method of determining which transmission mode should be transmitted to a plurality of branch ducts of small diameter connected to the diffuser in order to transmit the radio wave to have a uniform reception level in the entire space when using the air conditioning duct for transmission In order to send such a transmission mode to the branch duct, we propose an algorithm that determines where the feeder should be placed in the large diameter main duct. The intensity of propagation propagated to branch duct increases as TEmo mode with larger k-vector in the axial cross section of the duct cross section, so branch duct near the feeding point is smaller older than m, and branch duct far away is larger than m. Transmission in higher order mode ensures an even reception level across the space. In order to transfer these modes to each branch duct, the position of the feeder should be interpreted using a 2 ray model for the large diameter duct and the algorithm was proposed.

By setting the position of the feeder by using the mode assignment method for each branch duct proposed by the present invention and the feeder position setting algorithm, an in-building wireless network having a more uniform reception level can be constructed along the connected duct network.

1 is a structure in which several branch end ducts are connected across a main duct, which is a typical duct network of an office building. The purpose of the present invention is to explain the feeding position selection for feeding in the optimal mode by feeding in the main duct. Fig. 2 shows the electric field center points of the transmission mode induced by the branch duct. Figs. 3, 4 and 5 show the cross-sectional electric field distributions of the vertically polarized modes TE10 / TE20 / TE30, respectively. Figure 6 shows the transmission characteristics to the branch duct for each vertical polarization mode. It can be seen that the TE30 mode exhibits the largest transfer characteristic to the branch duct. 7 shows the phase of the TE20 mode induced in the branch duct. 8 shows a positioning algorithm of a feeder.

The air-conditioning duct network usually has a structure in which branch ducts are connected across the main duct that runs long through the center. At this time, the branch duct is a terminal duct having a size of about 200mm × 200mm connected to the diffuser. In order to transmit the maximum propagation energy from the duct to the diffuser, a TEmo mode having a large k-vector component in the direction of the branch duct is advantageous. The reception level coupled to the branch duct according to the mode number m is shown in FIG.

In this case, when feeding is performed in the main duct in the center, the feeder should be a linear array antenna of vertical polarization, and the mode in which excitation to the branch duct is changed depending on the feeding position. To accurately interpret this, the modes that are excited into each branch duct according to the feeding position must be analyzed by simulation. However, when the size of the duct increases, too many modes are excited in the main duct, which requires a lot of computation time. In order to solve this problem, the present invention proposes a technique for obtaining a mode of induction from a large-diameter duct to a small-diameter end duct as the sum of several approximated rays. As shown in FIG. 7, the electric field at any point P of the branch duct connection can be expressed as follows. The electric field strength at any point is as follows.

The branch duct is far enough away from the feeding position

If,

Since the phase difference between each path is

Can be approximated by

In this way, the magnitude and phase of the electric field strength are obtained at several points of the connection portion of the small-diameter duct, and then the phase is compared with the phase of the desired excitation mode. 3, 4, and 5 show the electric field distribution of the TE10, TE20, and TE30 modes. It can be seen that the phase at the peak position on the x axis of each mode is 180 degrees from the adjacent peak. The feeding position selection algorithm proposed by the present invention is as follows.

1) A branch duct near the main duct causes the TE's m low (low order) mode to be sheared, while a distant branch duct causes the m high (high order) mode to be delivered.

2) Determine the point Pm by dividing the line segment of the main duct and the connection part uniformly by the mode number m.

3) Find the phase from each point Pm of the main duct's longitudinal axis to each point Pm of the branch duct joint, and find out which mode of the phases is close to the mode in [XX] and map it to the mode.

4) List the points on the longitudinal axis that move the feeder position on the longitudinal axis and excite the mode assigned to the corresponding branch duct in 1) above.

5) Set the feeding position at the position where the sum of distances from the feeding points corresponding to the assignment mode of each branch duct is the smallest.

This is shown in a flowchart as shown in FIG.

Field strength

: Wave vector

: Distance from feeding point to electric field

: Width of main duct and branch duct

= Height in the longitudinal direction of the duct from the feeding point to the electric field

Claims (2)

Optimal mode selection technique delivered to branch ducts; The duct branching near the feeder of the main duct transmits low order TEmo mode, and the duct branching far away transmits the high order mode, so that the reception level is distributed evenly over the entire space. Can be. Feeder positioning algorithm to excite the desired mode for each branch duct.

Images