• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.651-659
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• 2010

In this paper, a new six-port direct conversion receiver for high-speed multi-band multi-mode wireless communication system such as software defined radio(SDR) is proposed. The designed receiver is composed of two CMOS four-port BPSK receivers and a dual-band one-stage polyphase filter for quadrature LO signal generation. The four-port BPSK receiver, implemented in 0.18 ${\mu}m$ CMOS technology for the first time in microwave-band, is composed of two active combiners, an active balun, two power detector, and an analog decoder. The proposed polyphase filter adopt type-I architecture, one-stage for reduction of the local oscillator power loss, and LC resonance structure instead of using capacitor for dual-band operation. In order to extent the operation RF bandwidth of the proposed six-port receiver, we include I/Q phase and amplitude calibration scheme in the six-port junction and the power detector. The calibration range of the phase and amplitude mismatch in the proposed calibration scheme is 8 degree and 14 dB, respectively. The validity of the designed six-port receiver is successfully demonstrated by modulating M-QAM, and M-PSK signal with 40 Msps in the two-band of 900 MHz and 2.4 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2267-2272
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• 2009

The six-port direct conversion receiver front-end that is comprised of a carrier recovery and a phase shifter, which gets the same structure with six-port phase correlator using the multi-layer coupled line, was designed and fabricated in this paper. The six-port element that is comprised of the power divider and the hybrid coupler is designed by multi-layer coupled line structure. The multi-coupled structure is utilized as the basic structure in receiver phase correlator, carrier recovery circuit and phase shifter. The receiver front-end with the same multi-layer coupled line structure for the receiver elements shows the simple structure and no difficulty in integration. The fabricated multi-layer coupled six-port receiver front-end re-generates the carrier signal with a constant phase and demodulates the PSK transmission signal.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2194-2200
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• 2010

In this paper, the power detectors using metamaterials were designed and fabricated for multi-band six-port direct conversion method. The RF short-stubs for power detector were designed by using metamaterials which provide multi-band characteristics. The power detectors with metamaterial RF short-stub were analyzed and fabricated by using lumped and distributed element. The measured results of metamaterial power detectors show the good agreement with the simulation results. The performance of lumped-metamaterial RF short-stub shows the insertion loss below 1 dB and the good frequency response characteristics. Also, the distributed-metamaterial RF short-stub shows the good frequency response characteristics and the insertion loss under that of lumped-metamaterial RF short-stub. The multi-band power detectors with metamaterial RF short-stub detect the input RF signal in the designed dual frequency bands very well.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.23-28
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• 2009

The general six-port phase correlator is comprised of a Wilkinson power divider and three $90^{\circ}$ hybrid coupler, which has less than 10 % bandwidth. In this paper, the six-port phase correlator using two section power divider has 33 % bandwidth and external matching $90^{\circ}$ hybrid coupler with 15 % bandwidth was designed at the center frequency of 2.5 GHz. The simulation result by ADS2003A indicates that RF port and LO port of proposed six-port phase correlator got wide frequency bandwidth of 14 % for VSWR of 1.5. The fabricated six-port phase correlator has a bandwidth of 12 % similar to the simulation result. The maximum phase discrepancy and insertion loss are $6^{\circ}$ and 2.5 dB over a bandwidth, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.129-132
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• 2008

The generally six-port phase correlator is comprised of a wilkinson power divider and three $90^{\circ}$ hybrid coupler, got bandwidth performance of less than 10%. in this paper, the six-port phase correlator using two section power divider has 33% bandwidth and external matching hybrid coupler has 15% bandwidth was designed with the center frequency of 2.5GHz. Analysis of the simulation result indicates that RF port and LO port got frequency bandwidth of 13%. Insert loss performance of fabricated six-port phase correlator is incremented, but bandwidth resembles simulation result. And phase tolerance within bandwidth is less than $90^{\circ}$.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.1-7
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• 2004

The development of direct receiver techniques is expected to be a solution for future wideband or multi-band wireless systems based on software defined radio. In this Paper, we study the regeneration of I and Q signals for the SDR based direct conversion receiver, so that we can handle a wide bandwidth and maintain maximal flexibility in system utilization. After modeling the basic system considering the real wireless communication environment, and studying the impact of imperfect phase imbalance on the performance of a direct conversion receiver, we propose a suboptimal I and Q signal regeneration algorithm for the system. The proposed algerian regenerates I and Q signals using a real time early-late compensator which effectively estimates phase imbalances and gives feedback in a directreceiver. The proposed algorithm is shown to mitigate the impact of AWGN and improves performance especially at low SNR channel condition. According to the computer simulation, the BER performance of the proposed system is at least about 4 dB better than conventional systems under $45{\~}55$ degrees random phase errors.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.770-776
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• 2009

We propose and demonstrate an I/Q demodulator using four-port BPSK demodulator base on additive mixing and reflection-type phase shifter using hybrid technique. Previously, the conventional I/Q demodulator base on multiplicative or additive mixing method divides I/Q signal path from mixer to parallel-to-serial converter. In this paper, we propose new I/Q demodulator without dividing I/Q baseband signal path. The proposed schematic requires half size in implementation and half power consumption in baseband path compared with the conventional receiver. Also, the proposed receiver eliminates parallel-to-serial converter after data decoding. The proposed circuit has been successfully demodulated a QPSK signal with the L-band carrier frequency and 20 Mbps data rate.