Analysis of a novel active capacitance circuit using BJT and its application to RF bandpass filters

This paper presents a novel active capacitance circuit using BJT and RLC series-feedback. It is competitive in the noise performance and the stability by adjusting the feedback elements. We analyze its characteristics in detail and apply it to an RF application by designing a duplexer. The active capacitance circuit can replace the passive capacitors of resonators in Rx and Tx BPF, which provide negative resistance to compensate for parasitic resistance of inductors. With the detailed analysis, we can obtain the frequency range as well as the maximum value of negative resistance. The active duplexer is designed realized at cellular at Rx (824/spl sim/849 MHz) and Tx (869/spl sim/894 MHz) bands.

[1]  D. K. Adams,et al.  Active Filters for UHF and Microwave Frequencies , 1969 .

[2]  M. Hikita,et al.  Miniature SAW antenna duplexer module for 1.9 GHz PCN systems using SAW-resonator-coupled filters , 1998, 1998 IEEE MTT-S International Microwave Symposium Digest (Cat. No.98CH36192).

[3]  Jr. R. Wyndrum.  Microwave filters, impedance-matching networks, and coupling structures , 1965 .

[4]  H. Matsumoto,et al.  A miniaturized dielectric monoblock duplexer matched by the buried impedance transforming circuit , 1995, Proceedings of 1995 IEEE MTT-S International Microwave Symposium.

[5]  R. Weigel,et al.  A 900 MHz ladder-type SAW filter duplexer , 1996, 1996 IEEE MTT-S International Microwave Symposium Digest.

[6]  M. Guglielmi,et al.  Coplanar MMIC active bandpass filters using negative resistance circuits , 1994 .

[7]  Takeshi Nakao,et al.  SAW duplexer for PCS in US with excellent temperature stability , 2003, IEEE Symposium on Ultrasonics, 2003.

[8]  R. V. Snyder,et al.  Analysis and Design of a Microwave Transistor Active Filter , 1970 .

[9]  M. Guglielmi,et al.  Coplanar MMIC active bandpass filters using negative resistance circuits , 1994, Proceedings of 1994 IEEE Microwave and Millimeter-Wave Monolithic Circuits Symposium.

[10]  Sang-Won Yun,et al.  A novel bandpass filter using active capacitance , 2003, IEEE MTT-S International Microwave Symposium Digest, 2003.

[11]  P. Katzin,et al.  Active GaAs MMIC band-pass filters with automatic frequency tuning and insertion loss control , 1995 .

[12]  E. M. Jones,et al.  Microwave Filters, Impedance-Matching Networks, and Coupling Structures , 1980 .

[13]  Tatsuo Itoh,et al.  Microwave active filters based on coupled negative resistance method , 1990 .

[14]  C. Rauscher,et al.  Microwave Active Filters Based on Transversal and Recursive Principles , 1985 .