Volume 67, Issue 7-8

The limited availability of analog-to-digital converters with high enough speed and dynamic range makes conventional heterodyne receivers still a reasonable solution for millimeter wave work when a wide frequency tuning range is desired. These basically well-known arrangements from the microwave bands may show surprising phenomena if the features of individual millimeter building blocks are not carefully analyzed. LNA gain below the frequency range of interest can be 10–20 dB more than expected which could severely impair the system noise performance after downconversion. Local oscillator tuning sensitivity above 1000 MHz/V, partly based on almost mandatory multiplication, together with very large tuning speed easily cause stability problems. Particularly active multipliers have often less than 20 dB rejection of fundamental frequency and unwanted harmonics output, which together with mixer LO/IF feed through can completely desensitize the front-end. An improperly matched mixer IF port may confuse even an experienced designer by phantom responses. Finally, modern logarithmic detectors chips can unexpectedly waste more than 10 dB of receiver sensitivity.

In this paper, a novel narrow-wall double-slot 3 dB coupler is proposed. Efficient coupling is achieved between a substrate integrated waveguide (SIW) and a ground coplanar waveguide (GCPW). Such hybrid integrated coupler combines the low-loss property of SIW with the flexibility of CPW. The coupling mechanism between TE 10 mode of SIW and TEM mode of GCPW is studied. According to the provided theory, a 3 dB coupler is designed and fabricated operating around 18 GHz and achieves a relative bandwidth of 10%. The measured results are in agreement with the simulated ones.

This paper discusses the application of Lagrange interpolation and cubic spline interpolation to predict acceleration/velocity and to adapt better window lengths for any range of target acceleration. The estimated velocity/acceleration is then smoothed using Kalman and adaptive Kalman filters. Simulation results show that in a ‘high-level noise’ scenario, the interpolated adaptive filter gives a more accurate estimation than the existing method of using a rectangular window function. Track initialization error minimized with spline interpolation was comparable to that minimized with Lagrange interpolation.

Due to the increasing data transfer rates in hard disk drives, the crosstalk has become a source of operation failures during electrical and magnetic testing. In order to reduce this detrimental effect, the differential mode signal system of high-speed and high-density interconnects based on a new magnetic technique is proposed. The scattering parameters are evaluated in terms of the crosstalk and the transmission parameters, and then calculated using the 3D full wave simulation software. From the results, it is found that the proposed technique can suppress the near-end crosstalk and far-end crosstalk in a wide range of 1–20 GHz. In addition, the transmission signal levels from the proposed structure are still comparable to the conventional structure. Hence, the proposed technique provides an effective reduction of crosstalk, while maintaining the comparable transmission signal in a wide range of frequency.

In our previous work, we employed the frame aggregation method and the multipolling method based on the dynamic search algorithm for the AP (Access Point) to efficiently collect the real-time RFID tag data from the RFID readers. However, when a huge number of the RFID readers are associated with the AP, which may be a case in future wireless sensor networks, the dynamic search algorithm is expected not to derive the polling sequence in real-time. In this paper, to deal with this problem we propose the random sequence based multipolling method combined with the frame aggregation method.

A scheme of frequency synthesizer with radio frequency modulation using reference clock is proposed, implemented and tested. The synthesizer is based on direct digital synthesis (DDS) and phase locked loop (PLL). The proposed hybrid scheme offers a new approach in frequency modulation of the DDS output signal by modulating the signal used as a reference clock for DDS. The results of measurement confirm a high performance of the proposed scheme.

In this paper, a new expression of the equations describing the locked states of two van der Pol oscillators coupled through a broadband network and allowing an accurate prediction of the oscillators' amplitudes is presented. To do so, the York's theory is improved using a more accurate van der Pol model in order to obtain a new system of four equations with four unknowns describing the locked states of two van der Pol oscillators coupled through a resonant network. Then, the case of a resistive coupling circuit is deduced from this new system of equations. The theory regarding the prediction of the oscillators' amplitudes is verified using Agilent's ADS software for the practical case of an array made of two differential Voltage Controlled Oscillators (VCOs) coupled through a resistive network.

Cooperative temporal sensing and distributed estimation are two vital aspects of cognitive radio. This paper studies a joint cooperative temporal sensing and distributed estimation scheme for Bayesian optimal threshold. This scheme studies the impact of distributed estimation error on the performance of cooperative temporal sensing by using Bayesian cost, and the Bayesian optimal threshold is obtained by minimizing the Bayesian cost. Finally, we examine the performances of other optimal thresholds with different criterions, and the effect of imperfect channel estimation is also tested. Numerical results show the performance of proposed scheme and validate our analysis.

In this paper, the performance of the two-way relaying under the influence of channel estimation error and co-channel interference is analyzed. At the very beginning, based on the expression of the received signal-to-interference-plus-noise ratio (SINR), we work out the cumulative probability distribution function and the exact closed-form and approximate expressions of the outage probability. Then, we further derive the bit error rate (BER) of system. Finally, in order to reduce the impact of channel estimation error and interference on the system, we propose an appropriate power allocation scheme to reach a compromise between the outage probabilities of the two terminals. Our theoretical analysis is justified by the result of numerical simulation.