Search

In this paper, channel spatial characteristics which mainly depend on the spatial correlation are selected as the significant factors in over-the-air (OTA) testing for multiple input multiple output (MIMO) devices. The multi-probe anechoic chamber method, a promising candidate of the MIMO OTA testing methods, can reproduce the multipath environments in a controllable manner. A novel physical configuration based on the variation of relative positions of probes in a MIMO OTA setup is put forward to obtain better spatial characteristics. Two physical configurations are presented to make a comparison with the typical configuration in this paper. The simulation results show that by making a proper probe configuration, good channel simulation accuracy can be achieved. Meanwhile, in order to get better performance of emulating channel spatial characteristics, probes in the first and the last probe rings should be placed symmetrically in three dimensional (3D) physical probe configuration.

This paper proposes a low-cost hardware architecture based on concurrent dual-band digital pre-distorter (DPD). The architecture is implemented on field programmable gate array (FPGA) to compensate for the nonlinearity of the concurrent dual-band power amplifier (PA). This implementation introduces a novel model complexity reduction technique into system, namely, time-division multiplexing for out-of-band lookup tables (LUTs) sharing. Performances are evaluated with an experimental test setup using a wideband class-F PA. The dual-band signal center frequency separated by 80 MHz. Lower and upper center frequency are located at 2.61 GHz and 2.69 GHz, respectively. This novel DPD implementation maintains excellent performance, but uses hardware resources reduced by 29.17% compared with conventional approaches. The results show that the adjacent channel power ratio (ACPR) is less than 59 dBc and normalized mean square error (NMSE) is around 62dB for lower sideband (LSB) and 63dB for upper sideband (USB).

This paper studies the behaviors of power amplifier (PA) driven by a single-carrier continuous wave (CW) signal and a two-carrier CW signal both in theory and simulation, and explains why the traditional dual-band PA failed to perform satisfactory results when a two-carrier CW signal is applied to, called concurrently. Besides that, an evaluation standard of concurrent dual-band PA was presented to value its performance. Solution was given with design and fabrication of a concurrent 1.85 GHz/2.65 GHz class F PA, employing a 10W GaN HEMT device from Cree, CGH40010, whose measurement shows the saturated output power is 40.6 dBm and 40.8dBm with drain efficiencies (DE) of 77.4% and 75.3% at 1.85 GHz and 2.65 GHz, respectively. On the other hand, we see that the peak DE achieves 59.7% with an output power of 39.9 dBm in concurrent mode, which follows up with the standard.

A new compact bandpass filter based on two meandered parallel-coupled lines of different lengths in shunt is presented, using the signal-interference technique, this filter obtains a low insertion loss and sharp rejection. A set of analytical formulas and guidelines for the design of the bandpass filter are provided in two theoretical analysis methods. According to the number of attenuation poles of the reflection coefficients in the passband, it can be summed up two types of filters. To validated this topology, two wideband bandpass filters centered at 3 GHz are built to verify the theoretical prediction, the measured frequency response of the filter agrees excellently with the predicted result.

A triangular memory polynomial (TMP) predistorter is presented in this paper to linearize a power amplifier's nonlinear with memory effects. Compared with the traditional memory polynomial (MP) predistorter, the coefficients of TMP predistorter is reduced more than 75%, which can effectively decrease the implementation complexity. The coefficients of predistorter are directly extracted from an offline system identification process by an open-loop structure in our approach. Several signals with data rate 5 MHz, 10 MHz, 15 MHz and 20 MHz are used to verify the performance of the proposed predistorter. Experimental results show that the proposed TMP predistorter and the traditional MP predistorter almost have the same performance.

In this paper, a novel design of planar dual-band multi-way lossless power dividers (PDs), namely Bagley Polygon PDs, is presented. The proposed PDs use Π-type dual-band transformers as basic elements, whose design formulas are analyzed and simplified to a concise form. The equivalent circuit of the dual-band Bagley Polygon PD is established, based on which design equations are derived mathematically. After that, the design procedure is demonstrated, and special cases are discussed. To verify the validity of the proposed design, 3-way and 5-way examples are simulated and fabricated at two IMT-Advanced bands of 1.8GHz and 3.5GHz, then simulation and measurement results are provided. The presented PDs have good performances on the bandwidths and phase shifts. Furthermore, the planar configuration leads to convenient design procedure and easy fabrication.

The high-directivity single- and dual-band directional couplers based on substrate integrated coaxial line (SICL) are first proposed in this paper. As the SICL features the propagation of TEM mode, the SICL directional coupler can keep its high-directivity compared with the microstrip one. The SICL coupler also characterizes a vias-shielded structure keeping it away from lateral leakage, cross-talk or unwanted parallel-plate mode. The design approaches of the single- and dual-band SICL couplers with proper width-spacing are given. Experiments are carried on a SICL 2.35 GHz coupler and a SICL 0.8/2.35 GHz coupler. Compared with microstrip couplers, the SICL ones show a great enhancement in directivity.

In order to communicate successfully for mobile stations in signal dead zone, this paper presents an inverse-gain- feedback dual-loop automatic gain control (AGC) circuit used in WCDMA repeater uplink system. The repeater employs two stages radio frequency AGC circuits, which are gain control of input part and output part respectively, so that the system can work normally and automatically control the output power. Agilent advanced design system (ADS) is used as a simulation tool to analyze the performance. The results show that it is performed well, which has the characteristic of good frequency selectivity and channel selectivity, steady controllable output, large range of AGC gain and wide range of output power. Therefore, the proposed system is suitable to solve the problem of the dead zone in WCDMA communication.

In this paper the finite-difference time-domain (FDTD) method and the transmission lines (TL) method are used respectively in the calculation of voltage standing wave ratio (VSWR) in an axisymmetric coaxial connector with nonuniform medium. Numerical results between the two methods are compared; more details of signal propagation in the connector can be given from the FDTD method, but the TL theory used is more simple and satisfactory results can also be obtained; the experimental result is in agreement with the calculations.

In this paper crosstalk between transmission lines. (TL) in special directions such as perpendicular and parallel is studied in the frequency domain and time domain via electromagnetic field (EMF) theory. Magnitude of crosstalk between the two states is compared. Regulations of when the peaks or troughs should occur are summarized, results are verified with that of the finite-difference time-domain (FDTD) method.