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This paper represents a new enhanced Colpitts oscillator, which is designed based on g_m-boosting of a conventional Colpitts oscillator. The proposed topology increases the negative resistant and enhances the start-up difficulty of the conventional Colpitts oscillator. This enables the Colpitts oscillator to operate in low-power consumption. Moreover, the differential and balanced structure helps limit even-order harmonics and degrades the common mode noise effects in output. The proposed circuit is designed using 0.18 μm technology and is simulated under 1.8 V supply voltage in advanced design system (ADS). Simulations show the output phase noise of -140 dBc/Hz at 1 MHz offset frequency when the operating frequency is 1 GHz.

A large number of simultaneous frequency and amplitude data from an electronic chaotic circuit (Chua's circuit) have been obtained. These acquisitions are validated by plotting the bifurcation diagrams of the experimental data versus the bifurcation parameter. We introduce a topological parallel between the Colpitts oscillator and Chua's circuit, and look for similar behavior of the frequency fluctuations using the Allan deviation.

This paper presents an experimental verification of the theoretical predictions, recently published in [Maggio et al., 1999; De Feo et al., 2000], about the bifurcation phenomena occurring in the Colpitts oscillator. Specifically, we performed an automated series of simulations based on the Spice model and, more importantly, a computer-assisted set of measurements on a concrete realization of the oscillator. It turns out that the bifurcation phenomena exhibited by the oscillator are relatively independent of the simplifying assumptions on the transistor model. Moreover, it is shown that the predicted behaviors can be reproduced experimentally, both qualitatively and quantitatively, in a robust way.

A novel version of chaotic Colpitts oscillator is described. Instead of a linear loss resistor, it includes an extra inductor and a diode in the collector circuit of the transistor. The modified circuit in comparison with the common Colpitts oscillator may generate chaotic oscillations at the fundamental frequency f* noticeably closer to the threshold frequency f_T of the employed bipolar junction transistor, up to f* ≈ 0.6f_T.

We propose a method to locate wire faults using a chaotic signal generated by an improved Colpitts oscillator. The chaotic signal is divided into two parts: one serves as a reference signal, and the other serves as a probe signal which is sent down to the wire. The fault is detected by correlating the reference signal with the probe signal back-reflected from the fault. Experimental and numerical studies show that the chaotic signal generated by the improved Colpitts oscillator has a broad spectrum and excellent correlation properties. Using this chaotic signal, we experimentally prove our method can be used to locate open circuits, short circuits, impedance discontinuities and other different damage cases on wires, and also demonstrate its ability for testing live wires through the numerical simulation. The results show that a spatial resolution of 0.2 m and a maximum range of about 930 m can be achieved. Furthermore, the interference margin is about 167 dB for the digital signals such as Mil-Std 1553 data on wire.

We experimentally demonstrate radar remote imaging using a radio technique based on ultra-wideband chaotic signals over fiber links. The radar system includes three parts, i.e. a central station, some optical fiber links and a base station. At the central station, an ultra-wideband chaotic signal is generated from an improved Colpitts oscillator and then is up-converted as a probe signal. The probe signal is then converted to be in optical domain by the external modulation technique on laser diode for transmitting over a fiber link to a remote base station. At the base station, the probe signal is converted to be in electrical domain and then launched by a microwave antenna. After being received by another antenna, the echo signal from a target is converted to be in optical domain and then transmitted over a fiber link back to the central station. By optical-to-electrical conversion and down conversion, the echo chaotic signal is recovered. Utilizing the correlation method and back projection algorithm, an image of the target in the two-dimensional space can be realized at the central station. Our experiments successfully performed remote imaging for both planar and spherical reflectors with a distance over 10 km. The down-range resolution of 6-cm and 8-cm cross-range resolution were obtained, respectively. We will show that the power spectrum of the probe signal is adjustable in the spectral mask according to the Federal Communications Commission standards, therefore can avoid interference to the existing narrowband radio signals.