| dc.description.abstract | A bandstop filter is required in broad-band receivers to attenuate the interference signal from the wanted signal. Due to the voltage, temperature, and process variation, automatic tuning circuitry is required to maintain filter characteristics and improve the filter performance. This research proposes a new design method for a second-order tunable bandstop filter and a new technique to tune the center frequency, the bandwidth, and the attenuation of the bandstop filter. The first part of the work presents a tunable bandstop filter based on source follower. The filter is designed using a source follower architecture with partial positive feedback and feed-forward paths using a 0.18µm CMOS technology. The filter consumes about 1.4 mW from a 1.8V power supply, and it is designed to have 1.5 GHz center frequency with 360 MHz bandwidth and 80 dB attenuation. The filter achieves 10 dBm IIP3 for two tones at 1.2GHz and 1.203 GHz. The second part of the work discusses a new automatic tuning scheme for the bandstop filter. The method is tuning the filter parameters such as center frequency, bandwidth, and attenuation by using phase comparison. The phase difference between the input and the output of the bandstop filter is detected by D flip flops. The tuning circuit consists of D flip-flops, counters, switches, digital to analogue converter, and passive components. The tuning method was verified by simulation and experimental results. The simulation results show the frequency tuning error of 0.13% and the bandwidth tuning error of 0.88% at 1.5 GHz with bandwidth of 478MHz.
Experiment results were obtained using discrete components, showing the frequency tuning error of 0.22% and the bandwidth tuning error of 0.66% at 1KHz with bandwidth of 200Hz. | en |
