Volume 68, Issue 9-10

In this article the behavior of continuous mode amplifiers at different reference planes is discussed using the example of a continuous class-F −1 amplifier mode. The variation of the output impedances and the conversion of the output voltage and current waveforms are analyzed depending on the considered reference plane. For instance, the frequently discussed current source reference plane has a way different impedance characteristic than the accessible lead reference plane. In order to study this aspect, a broadband continuous class-F −1 mode amplifier has been realized using a bare-die GaN-HEMT. From 1.0 to 1.8 GHz, this amplifier attains 44.5–45.2 dBm output power with corresponding drain efficiency of 65–68%.

While the vast majority of GaN X-band PAs is realized as microstrip circuits, this paper reports design, fabrication and measurement of a coplanar version. The amplifier is processed using the FBH 4-inch GaN-on-SiC technology with 0.25 µm-gate GaN HEMTs. The two-stage power amplifier circuit delivers more than 12 W cw output power at 10 GHz, with a large-signal gain of 20 dB and a final stage drain efficiency of 45%. Benchmarking shows that these are best-in-class values for a coplanar X-band MMIC, which come very close to the state-of-the-art microstrip counterparts.

A method to improve the directivity of the microstrip coupler is presented. The pattern of the coupler is modified for phase velocity compensation, which results in high directivity. Using this procedure, two 15 dB couplers are designed and fabricated at 0.9 GHz. A high directivity of 35 dB and 39 dB are measured. The validity of the design concept is verified by simulations and measurements.

A novel three-pole tunable bandpass filter using mixed combline resonators with a center frequency band of 0.9–1.8 GHz is proposed in this paper. The varactor-tuned filter is designed on a Rogers substrate with ε r  = 2.2 and h  = 1 mm, with 1-dB fractional bandwidth of 11% ± 0.6% (absolute bandwidth 97 MHz to 187.2 MHz). Its insertion loss is varying from 4.58 dB to 2.86 dB and return loss is better than 10 dB within the tuning frequency range. The measured third-order inter-modulation intercept point and 1-dB power compression point at midband (1.35 GHz) are higher than 17 and 8 dBm, respectively. The measured results show good agreement with the simulated ones.

In this paper, a kind of concentric split-ring slots structure is utilized to design a novel triple-band-notched UWB antenna. Firstly, a concentric split-ring slots structure that has a higher VSWR than that of a single slot at notch frequency is presented. What's more, the structure is very simple and feasible to obtain notched-band at different frequency by adjustment of the length of slot. Secondly, a triple-band-notched antenna, whose notched bands are at 3.52–3.81 GHz for WiMAX and 5.03–5.42 GHz and 5.73–56.17 GHz for WLAN, is designed by using this structure. At last, a compact size of 24 × 30 mm 2 of the proposed antenna has been fabricated and measured and it is shown that the proposed antenna has a broadband matched impedance (3.05–14 GHz, VSWR < 2), relatively stable gain and good omnidirectional radiation patterns at low bands.

In this paper, the evaluation of cathode-heater assembly of magnetron injection gun (MIG) for 42 GHz, 200 kW gyrotron is presented. The cathode-heater assembly is purchased from M/S SEMICON.The cathode-heater assembly is experimentally studied in three different conditions; in a belljar system, during vacuum processing of MIG and during MIG testing to ensure the required rise of cathode surface temperature for pre-set heater power.

This paper obtains the exact solution for solitons propagating through magneto-optic waveguides. There are three forms of nonlinear media that are considered. They are Kerr law, power law and log-law nonlinearity. The ansatz approach retrieves bright, dark as well as singular soliton solutions. There are several constraint conditions that needs to be in place for the solitons and Gaussons to exist.

In this paper, we investigate the outage performance of decode-and-forward cognitive relay networks for Nakagami-m fading channels, with considering both best relay selection and interference constraints. Focusing on the relay selection and making use of the underlay cognitive approach, an exact closed-form outage probability expression is derived in an independent, non-identical distributed Nakagami-m environment. The closed-form outage probability provides an efficient means to evaluate the effects of the maximum allowable interference power, number of cognitive relays, and channel conditions between the primary user and cognitive users. Finally, we present numerical results to validate the theory analysis. Moreover, from the simulation results, we obtain that the system can obtain the full diversity.

In this paper, a novel companding scheme is proposed to reduce the peak-to-average power ratio (PAPR) of lattice orthogonal frequency division multiplexing (LOFDM) system. By transforming the statistics of original signals into a specified distribution form, which is defined by a continuous sine function, this scheme can achieve a simple companding form as well as an improved PAPR and bit-error-rate (BER) performance. Moreover, by introducing the variable companding parameters in the desired probability density function (PDF), a great design flexibility in the companding form and an effective trade-off between the PAPR reduction and BER performance can be achieved to satisfy various system demands. The general formulas of the proposed scheme are derived and a theoretical analysis regarding the achievable transform gain and the selection criteria of companding parameters are also conducted. Simulation results show that the proposed scheme can substantially outperform the conventional μ -law companding, exponential companding (EC), piecewise companding (PC) in terms of PAPR reduction, BER performance and bandwidth efficiency.

Consideration of the channel capacity temporal behavior, in order to design a system that could adapt the transmission rate according to the capacity evolving process, and could transmit close to the ergodic capacity, is provided in this paper. Channel conditions have been modeled by the recently introduced general κ-μ fading model. We have studied statistical properties of the capacity of κ-μ fading channels. Analytical expressions for the first order statistical properties: probability density function (PDF), cumulative distribution function (CDF) and the outage capacity (OC), as well as the second-order statistical properties, such as the level-crossing rate (LCR), and average fade duration (AFD) of the instantaneous channel capacity, have been derived. Obtained results are numerically presented and visualized by the corresponding graphs.

The Golden Code (GC) is a full-rate and full-diversity, space-time code for 2 × 2 multiple-input multiple-output (MIMO) systems with non-vanishing minimum determinant. Thanks to its algebraic construction, the GC achieves diversity-multiplexing gain trade-off and preserves the mutual information. The zero-forcing (ZF) detection is one of the simplest detection techniques that has a low computational complexity and provides a suboptimal performance. The purpose of this work is to investigate the effect of channel estimation error on the performance of the MIMO-ZF receiver for golden coded systems in spatio-temporally correlated Rayleigh fading channels. An upper and a lower bounds of the error probability are delivered and compared to the Monte Carlo simulation results. We quantify the capacity reduction due to the channel estimation error and to the spatio-temporally correlation. A tight lower bound of the ergodic capacity is provided. Numerical results show an excellent agreement between analytic bounds and Monte Carlo simulation curves. Moreover, the performances of the GC, in terms of bit error rate (BER) and channel capacity, are compared with those of the Alamouti coding.

In this paper, a detailed performance analysis of switch-and-stay combining receivers over non identical distributed extended generalized K fading channels is presented. The analysis has been performed in both noise and interference-limited environments (the level of interference or noise is ignored, respectively). The expressions for the output signal-to-noise (SNR) and signal-to-interference (SIR) probability density function and cumulative distribution function, in a form of Fox's H functions, are presented. Based on this, analytical expressions for evaluating the moments, outage probability, average bit error rate and average channel capacity are derived. The influence of fading and shadowing phenomena, as well as the influence of unbalanced input SNR/SIR on the most important performance metrics is obtained. Presented numerical results are confirmed by Monte Carlo simulations.

In Orthogonal Frequency Division Multiplexing (OFDM) the transmit signals have a highly fluctuating, non-constant envelope which is a technical challenge for the High Power Amplifier (HPA). Without any signal processing procedures the amplitude peaks of the transmit signal will be clipped by the HPA resulting in out-ofband radiation and in bit error rate (BER) performance degradation. The classical Tone Reservation (TR) technique calculates a correction signal in an iterative way to reduce the amplitude peaks. However this step leads to a high computational complexity. Therefore, in this paper an alternative TR technique is proposed. In this case a predefined signal pattern is shifted to any peak position inside the transmit signal and reduces thereby all amplitude peaks. This new procedure is able to outperform the classical TR technique and has a much lower computational complexity.