L-Band SiGe HBT Frequency-Tunable Dual-Bandpass or Dual-Bandstop Differential Amplifiers Using Varactor-Loaded Series and Parallel LC Resonators
IEICE transactions on electronics
L-band SiGe HBT frequency-tunable dual-bandpass or dual-bandstop differential amplifiers have been developed for the next generation adaptive and/or reconfigurable wireless radios. Varactor-loaded, stacked LC-resonators are used in the output circuit of differential amplifiers for realizing dual-bandpass responses as well as in the series feedback circuit for dual-bandstop responses. The varactor-loaded, stacked LC-resonator can provide bandpass or bandstop responses for multiple frequencies
... iple frequencies and the resonant frequencies can be tuned independently. With the use of the varactor-loaded, dual-band resonator in the output circuit of 0.35µm SiGe HBT differential amplifiers, the lower bandpass frequency can be varied from 0.6 to 1 GHz with a fixed upper bandpass frequency of 1.12 GHz. Meanwhile, the upper bandpass frequency can be varied from 0.69 to 1.07 GHz for a fixed lower bandpass frequency of 0.62 GHz. The dual-band gain was 9 to 13 dB over the whole frequency band. In addition, with the use of the varactor-loaded, dual-band resonator in the series feedback circuit of 0.35µm SiGe HBT differential amplifiers, the lower bandstop frequency can be varied from 0.87 to 1.28 GHz with a fixed upper bandstop frequency of 1.55 GHz. 414 K. Sakamoto and Y. Itoh Meanwhile, the upper bandstop frequency can be varied from 0.97 to 1.54 GHz with a fixed lower bandstop frequency of 0.87 GHz. The maximal dual-band rejection of gain was 16 dB. The varactor-loaded, stacked resonator presented in this paper is expected to be a key circuit technology for realizing bandpass or bandstop responses for multiple frequencies in the next generation adaptive and/or reconfigurable wireless transceivers.