We present a design and realization of a high efficiency C-Band (5.2 GHz-5.8 GHz) internally-matched gallium nitride (GaN) power amplifier (PA). To reduce power dissipation and to achieve high efficiency, both input and output matching networks, along with 2nd-harmonic modulation circuits, are designed accurately according to the source and load optimum impedances extracted by source-pull and load-pull measurements. The PA realizes an excellent rf performance under a pulsed condition, demonstrating a maximum output power of 52.2 dBm (164 W) with at least 13.5 dB gain in the frequency range from 5.2 GHz to 5.8 GHz (10% relative bandwidth). At the same time, a power-added efficiency (PAE) of 69.4% is observed at 5.6 GHz and over 65.0% throughout the whole bandwidth. The PAE is the state-of-art performance for C-band GaN high-electron-mobility transistor PA with such high output power, to the best of our knowledge.
An X-band inverse class-F power amplifier is realized by a 1-mm AlGaN/GaN high electron mobility transistor (HEMT). The intrinsic and parasitic components inside the transistor, especially output capacitor C ds , influence the harmonic impedance heavily at the X-band, so compensation design is used for meeting the harmonic condition of inverse class-F on the current source plane. Experiment results show that, in the continuous-wave mode, the power amplifier achieves 61.7% power added efficiency (PAE), which is 16.3% higher than the class-AB power amplifier realized by the same kind of HEMT. To the best of our knowledge, this is the first inverse class-F GaN internally-matched power amplifier, and the PAE is quite high at the X-band.
A high-efficiency C-band internally matched power amplifier, developed with 12 mm AlGaN/GaN high-electron mobility transistors is described. The second-harmonic frequency (2f 0) tuning network is applied to confine the impedance at 2f 0 in safe efficiency regions. The packaged power amplifier achieves 71% power-added efficiency (PAE) and 102 W output power, associated with 17 dB power gain. The PAE is believed to be the highest of the C-band GaN power amplifiers reported to date. power of more than 92 W. At 4 GHz, a PAE of 71% is achieved with an output power of 102 W. To the best of our knowledge, this is the state-of-the-art performance ever reported for a C-band internally matched 12 mm GaN HEMTs power amplifier.
An energy detection-based active spectrum sensing scheme is proposed to carry out spectrum sensing and secondary transmissions simultaneously. It successfully avoids the widely used quiet periods, which have at least two shortcomings. First, periodical interruptions of secondary transmissions degrade the quality of service of secondary networks (e.g. decreasing the system capacity and increasing end-to-end packet delay). Second, frequent tight synchronisation is necessary but very difficult to implement in the distributed networks. With the assistance of the geolocations, the proposed sensing scheme is able to decompose the received power into the primary signal power, secondary signal power, and the device noise power. The power decomposition is formulated into a problem of solving a homogeneous linear equation set with a coefficient matrix involving only the distances among the primary users, secondary users, and the sensors. Through the decomposition, the primary signal power can be differentiated from the secondary signal power, which is generally treated as interference in spectrum sensing. When constructing the test statistic, such interference can be cancelled from the collected energy. As a result, the noise uncertainty problem, which significantly compromises the performance of the energy detection, can be greatly alleviated by noticing the fact that the interference dominates the noise uncertainty problem. Because the achieved signal-to-interference ratio can be improved by cancelling the interference, the detection errors in terms of the probability of false alarm and missed detection can be significantly reduced. Simulations verify the feasibility and efficiency of the proposed scheme.
As the precondition of dynamic spectrum access (DSA), the accuracy and efficiency of spectrum sensing (SS) have an important impact on performance of cognitive networks. However, the performance of energy-aware SS is greatly compromised by the accompanying inter-channel interference (ICI). Aiming to alleviate ICI, this paper proposes an energyaware cooperative SS method with ICI cancellation. The proposed method consists of two parts: the determination of the optimal threshold and the ICI cancellation. The optimal threshold is obtained by minimizing the sum of probabilities of false alarm and missed detection. The ICI cancellation is implemented indirectly by solving a non-homogeneous linear equation set with a coefficient matrix depending only on the distances between the secondary users and the transmitters of primary users. Simulation shows that the proposed SS method can efficiently cope with the ICI and can achieve much better performance in the range with low signal to interference-plusnoise ratio.
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