A compact feeding network with radiation contribution is proposed in designing microstrip patch array antenna (MPAA) for X-band marine radar applications. The 1-to-4 feeding network consists of two circular-sector patch balun, which can radiate electromagnetic wave with the same polarization of the patch array for enhancing the gain and suppressing the cross polarization. The feeding line in the series-fed patch subarray is modified as the step-impedance microstrip line to decrease the side-lobe level (SLL). To verify the method, a 28-element 9.41-GHz MPAA with the proposed radiated feeding network is designed and fabricated. Measured results show that the impedance bandwidth is 183 MHz with a peak gain of 21.3 dBi. The SLL is 27.8 and 21.4 dB in the E-and H-planes, respectively. The cross polarization is effectively reduced, which is lower than the copolarization of about 57 dB. K E Y W O R D S cross-polarization suppression, gain enhancement, patch array antenna,

A novel Gysel power divider with negative group delay (NGD), good matching, and low insertion loss is proposed. Resistors connected with short-circuited coupled lines (RCSCL) are shunted at output ports of the Gysel power divider to obtain NGD characteristics, and another resistor is shunted at the input port to realize perfect input and output matching. To verify the proposed structure, an NGD Gysel power divider is designed and fabricated. At the center frequency of 1.0 GHz, the measured NGD times for different output ports are −1.94 ns and −1.97 ns, the input/output port return loss is greater than 38 dB, the insertion loss is less than 8.3 dB, and the isolation between output ports is higher than 41 dB. To enhance the NGD bandwidth, two RCSCL networks having slightly different center frequencies are connected in parallel, which provides wider bandwidth with good input matching characteristics.