An L-band HTS duplexer with improved performance for communication applications has been developed.This is an improved version of the duplexer previously developed by our group.The duplexer was composed of a T-junction and two channels.Each channel has a 10-pole quasi-elliptic function bandpass HTS filter with a bandwidth of 27 MHz,and center frequencies at 1200 MHz and 1260 MHz.To achieve higher performance,especially a good balance between selectivity and flat group delay,the two pairs of transmission zeros from the two filters were reassigned so that one pair is used for high selectivity and the other for flat group delay.To reduce the influence of parasitical coupling,new coupling structures were developed in the simulation process.The duplexer was fabricated on a 2 inch diameter,0.5 mm thick LaAlO3 wafer with a double-sided YBCO film.The measured results showed a very high performance:a mid-band insertion loss of 0.2 dB,a return loss better than-14 dB,a shape factor better than 1.4:1,an out-of-band rejection of better than 70 dB in a wide frequency range up to 3 GHz and excellent isolation(higher than 80 dB) between the two channels.In addition,the frequency band 5 ns group delay variation is over 10.5 MHz(38.7% of 1 dB bandwidth). An L-band HTS duplexer with improved performance for communication applications has been developed. This is an improved version of the duplexer previously developed by our group. The duplexer was composed of a T-junction and two channels. Each channel has a 10-pole quasi-elliptic function bandpass HTS filter with a bandwidth of 27 MHz, and center frequencies at 1200 MHz and 1260 MHz. To achieve higher performance, especially a good balance between selectivity and flat group delay, the two pairs of transmission zeros from the two filters were reassigned so that one pair is used for high selectivity and the other for flat group delay. To reduce the influence of parasitical coupling, new coupling structures were developed in the simulation process. The duplexer was fabricated on a 2 inch diameter, 0.5 mm thick LaAlO3 wafer with a double-sided YBCO film. The measured results showed a very high performance: a mid-band insertion loss of 0.2 dB, a return loss better than-14 dB, a shape factor better than 1. 4: 1, an out-of-band rejection of better than 70 dB in a wide frequency range up to 3 GHz and excellent isolation (higher than 80 dB) between the two channels. In addition, the frequency band 5 ns group delay variation is over 10.5 MHz (38.7% of 1 dB bandwidth).