A reconfigurable OTA-C baseband filter with wide digital tuning for GNSS receivers

The design of a digitally-tunable sixth-order reconfigurable OTA-C filter in a 0.18-μm RFCMOS process is proposed.The filter can be configured as a complex band pass filter or two real low pass filters.An improved digital automatic frequency tuning scheme based on the voltage controlled oscillator technique is adopted to compensate for process variations.An extended tuning range（above 8：1） is obtained by using widely continuously tunable transconductors based on digital techniques.In the complex band pass mode,the bandwidth can be tuned from 3 to 24 MHz and the center frequency from 3 to 16 MHz.

On-chip digitally tunable positive/negative dispersion controller using bidirectional chirped multimode waveguide gratings

A silicon-based digitally tunable positive/negative dispersion controller(DC)is proposed and realized for the first time using the cascaded bidirectional chirped multimode waveguide gratings(CMWGs),achieving positive and negative dispersion by switching the light propagation direction.A 1×2 Mach-Zehnder switch(MZS)and a 2×1 MZS are placed before and after to route the light path for realizing positive/negative switching.The device has Q stages of identical bidirectional CMWGs with a binary sequence.Thus the digital tuning is convenient and scalable,and the total dispersion accumulated by all the stages can be tuned digitally from−(2^(Q)−1)D0 to(2^(Q)−1)D_(0) with a step of D_(0) by controlling the switching states of all 2×2 MZSs,where D_(0) is the dispersion provided by a single bidirectional CMWG unit.Finally,a digitally tunable positive/negative DC with Q=4 is designed and fabricated.These CMWGs are designed with a 4-mm-long grating section,enabling the dispersion D_(0) of about 4.16 ps∕nm in a 20-nm-wide bandwidth.The dispersion is tuned from−61.53 to 63.77 ps∕nm by switching all MZSs appropriately,and the corresponding group delay is varied from−1021 to 1037 ps.

Micro EEG/ECG signal's chopper-stabilization amplifying chip for novel drycontact electrode

Facing the body＇s EEG（electroencephalograph, 0.5–100 Hz, 5–100 μV） and ECG＇s（electrocardiogram,〈 100 Hz, 0.01–5 mV） micro signal detection requirement, this paper develops a pervasive application micro signal detection ASIC chip with the chopping modulation/demodulation method. The chopper-stabilization circuit with the RRL（ripple reduction loop） circuit is to suppress the ripple voltage, which locates at the single-stage amplifier＇s outputting terminal. The single-stage chopping core＇s noise has been suppressed too, and it is beneficial for suppressing noises of post-circuit. The chopping core circuit uses the PFB（positive feedback loop） to increase the inputting resistance, and the NFB（negative feedback loop） to stabilize the 40 dB intermediate frequency gain. The cascaded switch-capacitor sample/hold circuit has been used for deleting spike noises caused by non-ideal MOS switches, and the VGA/BPF（voltage gain amplifier/band pass filter） circuit is used to tune the chopper system＇s gain/bandwidth digitally. Assisted with the designed novel dry-electrode, the real test result of the chopping amplifying circuit gives some critical parameters： 8.1 μW/channel, 0.8 μVrms（@band-widthD100 Hz）, 4216–11220 times digitally tuning gain range, etc. The data capture system uses the NI CO＇s data capturing DAQmx interface,and the captured micro EEG/ECG＇s waves are real-time displayed with the PC-Labview. The proposed chopper system is a unified EEG/ECG signal＇s detection instrument and has a critical real application value.