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A design for OFDMA receiver

Jianhua Zhang — 2008-04-23T18:38:14-00:00

Vehicular Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, Vol. 2 (2005), pp. 1268-1272 Vol. 2.

In this paper, a design for OFDMA receiver is given. Timing synchronization is achieved by ML algorithm with Gold sequence and then multipath delay estimate is achieved by the correlation operation between the local training sequence and the sampled received signal. In order to decrease the overhead for channel estimation, multiple users are combined as a group to share the pilot subcarriers and Walsh codes are used as pilots for different users. For such user group, LS algorithm with the forward estimated delay is adopted to estimate the channels of users. The simulation results show that this receiver can achieve the timing synchronization, multipath delay estimate at low SNR and good BER performance with accurate channel estimation.

A Microtransceiver for UHF Proximity Links Including Mars Surface-to-Orbit Applications

W Kuhn — 2008-04-10T06:21:25-00:00

Proceedings of the IEEE, Vol. 95, No. 10. (2007), pp. 2019-2044.

A low-volume low-mass low-power ultra-high-frequency radio transceiver for future planetary missions is described. The project targets a volume of less than 10 , mass of less than 50 grams, and power consumption of 50 mW on receive and 100 mW, 300 mW, or 3 W on transmit (for 10 mW, 100 mW, and 1 W output options). The transmitter design supports convolutionally coded binary phase-shift keying (BPSK), RC-BPSK, and quadrature phase-shift keying transmission from 1 to 256 kbps. Command/control instructions can be received at 2 or 8 kbps, with a sensitivity of better than 120 dBm. In addition to its low volume/mass/power features, temperature compensation to 100 C and radiation tolerance to 100 krad allow operation outside of thermally controlled, shielded enclosures, further reducing the mass and complexity of exploration vehicles. The design is described in a top-down format, beginning with system requirements and proceeding through digital modem algorithm development, discussion of the silicon-on-sapphire CMOS process used and elaboration of key blocks in the radio-frequency (RF) integrated circuit design. Techniques to address coupling between high-sensitivity RF and on-chip digital circuits are also presented, and test results are given for prototypes of all major functions. Although designed for the Martian environment, the transceiver is expected to be useful in other proximity links where a small low-power radio compatible with Prox-1 space-link protocols is desired.

Dual structure of composite right/left-handed transmission line

Xin Hu — 2007-11-07T07:53:03-00:00

Journal of Zhejiang University - Science A, Vol. 7, No. 10. (23 October 2006), pp. 1777-1780.

Abstract A dual structure of composite right/left handed (CRLH) transmission line (TL) is analyzed in which an inductance L R is in parallel with a capacitance C L and a shunt capacitance C R is in series with an inductance L L. Both the distributed and lumped cases are considered. The dispersion diagram and transmission properties of the dual CRLH TL are given and compared with those of a standard CRLH TL. Contrary to the frequency response of a standard CRLH TL, a dual CRLH TL has a left-handed (negative phase shift) band at higher frequencies and a right-handed (positive phase shift) band at lower frequencies. A novel dual-band balun is presented as an application.

A new broadband differential phase shifter fabricated using a novel CRLH structure

Yong-Zhuo Zou — 2007-11-07T07:47:38-00:00

Journal of Zhejiang University - Science A, Vol. 8, No. 10. (29 October 2007), pp. 1568-1572.

Abstract Broadband phase shifters are mostly proposed and fabricated based on the scheme proposed by Shiffman, which uses a coupled line with far ends connected together and a uniform transmission line to give a differential phase shift. Based on the unique dispersion property of the composite right/left-handed (CRLH) metamaterial structure, a new configuration is presented in this paper for fabricating the broadband differential phase shifter, which employs a novel CRLH metamaterial structure as one of the differential phase-shift arms, instead of the conventional coupled line. The new circuit can achieve a phase shift of 90� in an operational bandwidth as broad as one octave and its phase deviations are quite small. An original design of the novel broadband phase shifter is presented, in which the artificial CRLH structure was implemented by microstrip quasi-lumped elements. Both the simulated and measured results of the 90� broadband differential phase shifter are presented.

Codirectional coupler and power divider mixed microstrip and metamaterials with lumped-elements L-C

Dongke Zhang — 2007-11-02T17:41:07-00:00

Microwave and Millimeter Wave Technology, 2004. ICMMT 4th International Conference on, Proceedings (2004), pp. 304-307.

A coupled-line backward coupler and a power divider, composed of the conventional microstrip line and the composite left-handed line with lumped-elements L-C, are presented. The coupler exhibits arbitrary coupling level and broad bandwidth. The power divider shows multi-ports, different coupling level output. The theoretical circuit-model simulated results are demonstrated by experiments. Both a 3-dB coupler and a trisecting power divider are demonstrated experimentally.