中文摘要：

被动雷达导引头为探测与跟踪目标可采用宽带等角螺旋天线，针对降低等角螺旋天线剖面，该文提出一种低剖面背腔式微带线-槽线馈电缝隙等角螺旋天线。微带线一槽线巴伦（Balun）中渐变微带线将同轴线激励的不平衡电场最终转化为槽线处平衡电场。实测结果表明，该缝隙等角螺旋天线实现了1：9的电压驻波Ht（VSWR）带宽，良好的辐射方向图与圆极化特性。在天线背面加入高度仅有0．05A，（A，为最低工作频率所对应自由空间中波长）的反射腔，腔内放置矩形环状吸波材料，有效拓展了天线低频段带宽。测试结果表明带有反射腔的缝隙等角螺旋天线实现了1：6．4的电压驻波比带宽，天线增益大于4dB，良好的圆极化与方向图特性。平面化、一体化的馈电方式与低剖面反射腔有效降低了缝隙等角螺旋天线剖面，测试结果验证了该文所提出的微带线一槽线巴伦馈电缝隙等角螺旋天线设计方法的有效性。

英文摘要：

Wideband equiangular spiral antennas are typically applied to detection and tracing of passive radar seeker. In order to reduce the height of the equiangular spiral antenna, a low-profile slot equiangular spiral antenna fed by a microstrip to slotline and backed by a cavity is proposed. This microstrip to slotline Balun （unbalance to balance） transforms unbalanced electrical distribution produced by coaxial line into balanced electrical distribution to feed the slot equiangular spiral antenna. Measure results indicate that a wide band （1 ： 9） of Voltage Standing Wave Ratio （VSWR）, good radiation pattern and circular polarization are realized. The height of back cavity for a unidirectional radiation is 0.05At （ AL is the wavelength of lowest operation frequency）. Lower working frequency band is expanded by filling the back cavity with a ring-shaped rectangular absorber. Measured results show that a frequency band of 1：6.4 （voltage standing wave ratio VSWR below 2）, better than 4 dB antenna gain, good circular polarization and radiation pattern are achieved. Planar feed structure and shallow cavity contribute to a low-profile slot equiangular antenna. Measured results verify the effectiveness of the microstrip to slotline Balun used to feed the slot equiangular slot antenna.