SINAD

Abstract: A noise squelch circuit for a radio receiver (100) includes an adaptive filter (204) for shaping frequency characteristics of a demodulator out put (115) according to factors which effects squelch sensitivity. Such factors may include channel spacing of the receiver, received signal strength level, received signal deviation, and SINAD. The adaptive filter (204) comprises a switched capacitor filter, the response of which may be controlled by a control signal (212) according to one or more of such factors.

Abstract: A gain error correction (GEC) technique is presented that continuously measures and digitally compensates for analogue gain errors present in each stage of a pipelined analogue-to-digital-converter (ADC). Simulations with and without the GEC technique indicate that the technique results in a large improvement in the signal-to-noise-and-distortion (SINAD) and spurious-free-dynamic-range (SFDR) of the converter.

Abstract: Fiber-optic interferometric sensors (FOISs) are widely used in seismometers, hydrophones, and gyroscopes. The arctangent approach of phase-generated carrier (PGC-Arctan) demodulation algorithm is one of the key demodulation techniques in FOISs. The conventional PGC-Arctan demodulation algorithm requires the specific value of the phase modulation depth C to work properly. However, C will variate with laser wavelength, temperature, and humidity in the actual working environment, which leads to harmonic distortion and even demodulation failure. In this paper, a novel PGC demodulation algorithm called self-calibration PGC-Arctan (PGC-Arctan-SC) demodulation algorithm is presented. The proposed algorithm can jointly estimate the accurate C value by the elliptical parameters and C-related components while suppressing nonlinear distortion by ellipse fitting algorithm (EFA). Then C can be calibrated to the specific predefined optimal value by the closed-loop proportion integration differentiation (PID) module. The simulation results are consistent with theoretical analysis, and the all-digital PGC-Arctan-SC demodulation system is implemented on the embedded SoC. The experimental results show that C can be estimated and calibrated accurately in real time. The signal-to-noise and distortion ratio (SINAD) of the PGC-Arctan-SC demodulation output achieves 61.57 dB.

Abstract: An quality testing apparatus and method for providing an objective and real-time evaluation of voice quality in a wireless communication system. The system under evaluation would include a receiving and transmitting apparatus at both ends of the system. To evaluate voice quality, one apparatus transmits a TDM base band voice test signal to a receiving apparatus. The configuration of the transmitted TDM base band voice test signal permits the receiving end to synchronize a test sentence, contained within the TDM test signal, with a corresponding reference sentence stored at the receiving apparatus. After synchronization, the receiving apparatus uses a model of human hearing to objectively compare the two sentences, and based on the result, outputs an AQS ranking. In addition to voice quality, the apparatus measures SINAD, noise, distortion, and signal level of transmitted test tones and maintains a log of call progress statistics.