Papers by Author: Zhong Liang Deng

Abstract: This paper focuses on the method of pseudo-code ranging based on time divided CDMA-OFDM mixed signal system. A snapshot-replay method is proposed to make the receiver provide the measurement result of pseudo-code ranging under frequency fading channel, which enhance the continuity of the output of pseudo-code ranging result. The problem of ranging through tracking loop under frequency fading channel is analyzed. This paper analyzed and studied the design and realization of snapshot-replay method of pseudo-code ranging. Further, the impact due to limited frequency band is analyzed. Through software simulation and hardware verification, this method of snapshot-replay pseudo-code ranging is proved to be effective to enhance the continuity of the output of pseudo-code ranging result.

Abstract: Tunable bandpass filters are generally preferred and are used extensively in the mobile communication systems. In this paper, a design of the RF MEMS tunable combline bandpass filter is proposed. Firstly, the theory of the RF MEMS tunable combline bandpass filter is presented. Secondly, a combline bandpass filter which have a tunable frequency range from 18GHz to 27GHz is designed and simulated by using the EDA simulation software. Its bandwidth is about 1GHz in the tunable frequency range. From the simulation results, the designed filter is not only compact and effortless to fabricate but also relatively superior in some aspects.

Abstract: This letter presents a Ka-band(26.5GHz-40GHz) microstrip patch antenna with pattern reconfigurable characteristic. The antenna is provided with five rectangular patches and four RF MEMS (microelectromechanical systems for RF circuits) switches. The central patch and other surrounding patches are connected by the switches. By changing the states of the switches, the antenna can achieve four radiation patterns and it is designed and simulated by using Ansoft HFSS. In addition, the different states are operated at the same centre frequency of 35GHz and the gain of the main radiation direction is about 7.5dB

Abstract: In this paper, the design, optimization and equivalent circuit model for a K-band capacitive RF MEMS switch are presented. The fixed-fixed switch is designed with folded structures on the high-resistance silicon substrate, by using gold as the beam and silicon nitride as the dielectric layer. The resulting switch working on 25.2GHz exhibits the performance with insertion loss less than 0.20dB, isolation more than 40dB and the drive voltage less than 16V by simulation.

Abstract: This paper focuses on the research of weak signal acquisition based on time-division CDMA-OFDM (TC-OFDM) system by using long PN sequence with low power. An enhanced weak signal acquisition algorithm is proposed to improve the ability of weak signal acquisition compared with regular algorithm which uses short PN sequence with high power. Simulation shows that the ability of resistance to white noise in weak signal acquisition is enhanced by 12dB. Further, because of the good correlation of long PN sequence, the performance of resistance to strong signal interference has also improved 6dB.

Abstract: There are more acquisition cells and long stop time on each cell because of the features of the new GNSS signal systems. So the average acquisition time of the new signals increase much longer than the former one. The new signal features was analyzed at first in this paper, and then the acquisition algorithm of QPSK and MBOC modulated signals was introduced separately. A Multiplexing Channel of Time-Division technique and Multi-frequency aid algorithm was proposed to increase the acquisition speed. This new fast acquisition algorithm significantly reduced the average acquisition time of the new GNSS signal systems.

Abstract: This paper presents a K band (18GHz-26.5GHz) shunt capacitive micro-electromechanical systems (MEMS) switch. This switch used the coplanar waveguide (CPW) Defected ground structure (DGS) which is made by etching defect structure in CPW ground line. Furthermore the beam structure of the proposed switch is composed of one girder and two supporting beams. The design of the switchs structure is benefit to the apart between the DC signal and AC signal. The simulated values of the isolation of the switch on off-states is-55 dB at18.9 GHz, and the return loss at K band is greater than-0.3 dB. The pull-in voltage of the switch is 13.3 V.

Abstract: Location based service (LBS) is more and more important nowadays. Assisted with GNSS, Base Station Positioning System (BSPS) can offer seamless outdoor & indoor positioning. The fading channel causes problems in signal acquisition. In this paper, a new method of RAM-based frequency acquisition is introduced, which can acquire the residual carrier frequency in fading channel accurately.

Abstract: Some OFDM signal systems use PN (Pseudo-noise) sequence in time domain to synchronize. During the acquisition progress, the ground noise power has to be calculated, and the determination of the detection threshold is important. This paper introduced a simplified detection method for PN sequence, and analyzed the threshold to optimize the performance.

Abstract: The new generation of global navigation satellite systems will apply binary offset carrier (BOC) modulation technique, which can efficiently split the spectrums of navigation signals using the same frequency so as to reduce the interferences among different systems. But the autocorrelation function of BOC modulated signals has the drawback of multimodality, so it’s very hard to synchronize to the right peak when acquiring and tracking signals, especially under low SNR circumstances, which can decrease the positioning accuracy and even lead to wrong positioning results. Meanwhile, if there are multipath signals mixed in the receiving signal, the autocorrelation curve will be greatly distorted, and the number of side-peak will also increase exaggeratedly, which could deteriorate the situation mentioned above. A multipath cancellation method based on TK (Teager-Kaiser) operator is proposed in this article, which could not only detect the right peak in the autocorrelation curve, but also eliminate all the other multipath signals. As a result, this method could avoid the false lock of code phase and guarantee the high precision fix results.