A novel optical frequency-domain imaging system is demonstrated that employs a passive optical demodulation circuit and a chirped digital acquisition clock derived from a voltage-controlled oscillator. The demodulation circuit allows the separation of signals from positive and negative depths to better than 50 dB, thereby eliminating depth degeneracy and doubling the imaging depth range. Our sy...

We present two options for length sensing and control of a three mirror coupled cavity. The control of the first cavity uses phase modulation and single demodulation, whereas the control scheme for the second cavity incorporates amplitude or single sideband modulation and phase modulation in combination with a beat frequency demodulation scheme. Their theoretical and experimental performances a...

Conventional Orthogonal Frequency–Division Multiplexing (OFDM) receivers disregard oversized guard intervals. An (adaptive) Nyquist–shaped receive window could exploit signal samples in its unconsumed portion to improve demodulation. The OFDM transmitter is not modified, subcarrier orthogonality is preserved, and the DFT size may be retained. In this paper, we optimize the window shape by consi...

In OFDM communications, the loss of orthogonality due to carrier offset must be compensated before DFT-based demodulation can be performed. In this paper, we present a high accuracy blind carrier offset estimation algorithm and a blind channel equalizer which exploit the intrinsic structure information of OFDM signals. The latter method allows the receiver to perform coherent demodulation in ch...

Although one of the simplest and powerful approaches for the demodulation of a single fringe pattern with closed fringes is the regularized phase-tracking (RPT) technique, this technique has two important drawbacks: its sensibility at the fringe-pattern modulation and the time employed in the estimation. We present modifications to the RPT technique that consist of the inclusion of a rough esti...

Speech resonance signals appear to contain significant amplitude and frequency modulations. An efficient demodulation approach is based on energy operators. In this paper, we develop two new robust methods for energy-based speech demodulation and compare their performance on both test and actual speech signals. The first method uses smoothing splines for discrete-to-continuous signal approximat...

In this paper we examine demodulation methods for nonuniform Pulse Position Modulation (PPM), which is generated by the crossings of a modulating signal with a sawtooth wave. At high sampling rates (several times the Nyquist), demodulation can be achieved by an appropriate low pass filter of the PPM pulses. However, at sampling rates near the Nyquist rate, this approach creates unacceptable dis...

The increasing requirement for efficient and cost effective aircraft fleet management necessitates the integration of on-line health monitoring capability. Such capability must be reliable, robust and must easily respond to the physical and environmental constraints imposed by the aircraft environment. Highly multiplexed fibre optic Bragg grating sensors are assessed to meet this challenging en...

The frequency shift of the ultra-narrow frequency shift keying (UNFSK) is far less than the ordinary binary frequency shift keying (FSK) method. Because the two frequencies of UNFSK are extremely close, the traditional demodulation method cannot separate them successfully. This study aims to successfully demodulate the UNFSK signals by applying cycle extension and notch filter. The signal proce...