双信道应答器多天线间的互耦分析及降耦研究

Mutual Coupling Analysis and Decoupling of Multi-Antenna in Dual-Channel Balise

双信道应答器内部4个不同频率的天线间的互耦,破坏天线的调谐状态,影响天线的正常工作。基于天线的串、并联等效电路,推导天线带宽的计算公式;建立双信道应答器多天线的三维仿真模型,对串联等效电路进行仿真分析。结果表明:多天线间的互耦使损耗电阻增加,等效电感和自谐振频率减小,同时使天线间产生转移阻抗,进而导致调谐频率偏移;4.234 MHz FSK发射天线至27.095 MHz接收天线、9.032 MHz PSK发射天线至27.095 MHz接收天线、9.032 MHz PSK发射天线至4.234 MHz FSK发射天线、4.234 MHz FSK发射天线至9.032 MHz PSK发射天线的传输系数均大于-10dB。在4.234 MHz FSK发射天线和9.032MHz PSK发射天线的信号输出端增加低通滤波器后,天线间的传输系数均降低到-10dB以下,表明加载低通滤波器可有效降低多天线间的传输系数,从而实现了多天线间的降耦。

The mutual coupling among 4 antennas with different frequencies in the dual-channel balise destroys antenna tuning status and affects the normal operation of antennas. Based on the series and parallel equivalent circuit of antenna, the formula for calculating antenna bandwidth is derived. The three- dimensional simulation model is built for the multi-antenna in dual-channel balise to simulate and analyse the series equivalent circuit. Results indicate that the mutual coupling among multiple antennas makes the loss resistance increase, the equivalent inductance and self-resonance frequency decrease. Simultaneously, the transfer impedance is generated among antennas, which results in tuning frequency shift. The trans- mission coefficients from 4. 234 MHz FSK transmitting antenna to 27. 095 MHz receiving antenna, from 9. 032 MHz PSK transmitting antenna to 27. 095 MHz receiving antenna, from 9. 032 MHz PSK transmitting antenna to 4. 234 MHz FSK transmitting antenna, from 4. 234 MHz FSK transmitting antenna to 9. 032 MHz PSK transmitting antenna, are all greater than -10 dB. After low pass filters are added in the signal output terminals of 4. 234 and 9. 032 MHz transmitting antennas, all the transmission coefficients are reduced to below -10 dB. It indicates that adding low pass filter can effectively reduce the transmission coefficients among multiple antennas so as to realize the decoupling among multiple antennas.