Phased Array Antenna Simulation Considering the Effect of TR Components

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Phased Array Antenna Simulation Considering the Effect of TR Components [Copy link]

Simulation of Patch Array Antenna with TR module ' s effect

Chengcheng Xie Bhargava Anurag

Agilent TechnologiesEEsofEDA

Abstract: In this paper,a new simulation method of patch arrayantennais introduced. Not only simulate patch array antenna's EM performance, but also concern the affects of feed networks including power divider network, digital phase shifter , TR module etc. At last, a compare of gain with integrate array antenna and with ideal array antenna is given.

Keywords: Patch Array Antenna, TR module, co-simulation

1 Introduction

Phased array antennas were first used in military radars. Due to their many unique advantages, such as fast tracking speed, good electrical performance, high reliability, and easy conformal installation with the carrier, they have also become the preferred solution for various station antennas for satellite mobile communications, and have received high attention and wide application.

The traditional phased array design process usually considers the antenna array and TR components separately without considering the mutual influence. In fact, after the signal source passes through power distribution, electrical phase shifting, attenuation, and TR components, there are large differences in the amplitude and phase reaching the antenna feed end, which will affect the working performance of the phased array antenna array.

In this paper, the link from the signal source to the antenna is simulated using Agilent Technologies' Advanced Design System ( ADS ^[1] ), taking into account the differences between different RF channels and the interaction between the TR component and the antenna. Finally, the gain obtained by the joint simulation is compared with the traditional ideal feeding method.

2 Array Antenna Joint Simulation

The entire phased array system block diagram is shown in Figure 1. After the power source, it also includes a power distribution network, a digital phase shifter, a TR component, and a 4 × 4 antenna array.

Figure 1 Phased array antenna RF system block diagram

In the power distribution network, the 16- way power divider is simulated by using three-dimensional planar electromagnetic field and schematic linear simulation . While considering the coupling and discontinuity between transmission lines, the influence of isolation resistance is also added. As shown in Figure 2 , the inconsistency of the transmission and reflection characteristics of the 1 -to- 16 power distribution network is shown.

( a )

( b )

Figure 2 Power distribution network characteristics ( a ) transmission, ( b ) reflection

In the CNC phase shifter unit, the phase of each row is consistent, and the phase difference between adjacent rows is an integer multiple of phasegrad . The phase difference is a variable that can be set in the schematic diagram.

In the TR component unit, the behavioral model is used to model the TR component. In particular, key indicators such as the nonlinear characteristics of the power amplifier in the transmission link and the noise figure of the low noise amplifier in the receiving link are set. The block diagram of the TR component is shown in Figure 3 .

Figure 3 TR component block diagram

The array antenna simulation uses the planar three-dimensional electromagnetic field simulation tool Momentum embedded in ADS , which can take into account the coupling between antennas and the specific layout, and obtain the S parameters of each port of the entire array.

After simulating the entire circuit using the harmonic balance method, accurate information about the amplitude and phase of each antenna feed port can be obtained ^[2] , as shown in Figure 4. It can be seen that the amplitude consistency of each port is acceptable, but the phase difference is large, with the difference between the maximum and minimum values reaching 24.7 degrees. The impact caused by the discreteness of amplitude and phase will be considered later. It can be seen that when designing power distribution networks and TR components, phase consistency should be considered and optimized as an important indicator.

Figure 4 Antenna port amplitude and phase comparison

After using Momentum 's 3D electromagnetic field post-processor, the amplitude and phase of each port of the antenna are loaded at the same time, and the 2D and 3D far-field characteristics of the entire system can be obtained. Figure 5 shows the 3D far-field comparison of the antenna array when each row is fed with equal amplitude and in phase and when each row is fed with equal amplitude and 30 degrees difference in phase. It can be clearly seen that the main lobe direction of the antenna has shifted.

( a ) Three-dimensional far-field gain diagram of the antenna array when fed with equal amplitude and in phase

( b ) 3D far-field gain diagram of the antenna array when feeding with equal amplitude and 30 degrees phase difference

Figure 5 Comparison of far-field three-dimensional radiation patterns of phased array antennas

To verify the impact of the RF circuit before the antenna array on the far field of the antenna, the 16 port excitations were directly set as equal-amplitude and in-phase signals in Momentum to obtain its far-field gain. Comparing the ideal feeding and the situation taking into account the amplitude and phase difference of the RF circuit, it can be seen that the phase inconsistency of the circuit leads to larger side lobes of the antenna.

Figure 6 Comparison of far-field gain of an ideal antenna array and an antenna array considering the influence of RF circuits

3 Conclusion

By using the schematic diagram and planar three-dimensional electromagnetic field joint simulation method, the influence of RF circuits such as power distribution network and TR components on array antenna can be taken into account, making the simulation results closer to the actual situation.