Koji Tsutsumi

0.4-5.2GHz SiGe-MMIC Direct Conversion Mixer for Cognitive Radio Receiver

0.4-5.2 GHz broad-band SiGe-MMIC direct conversion quadrature mixer (Q-MDC) has been developed for multi-band multi-mode cognitive radio receivers by using 0.35 mum SiGe BiCMOS process. To realize broad-band characteristic, a static frequency divider with two-stage emitter follower is used as 90 degree power divider for LO and broad-band doubly balanced mixers are used as I/Q unit mixers. The 90 degree power divider enable to achieve multi-octave operation for LO which covers whole band of 0.4-5.2 GHz. Broad-band unit mixers also enable to achieves wide RF band (0.4-5.2 GHz) and wide base band (up to 500 MHz). The fabricated Q-MIX performs EVM of less than 3% over the whole RF frequency range of 0.4 -5.2 GHz and shows the dynamic range of more than 40 dB for 0.4 GHz UHF application (16 QAM/OFDM), 0.8 GHz/2 GHz W-CDMA (QPSK) and 5.2 GHz IEEE 802.11a W-LAN (64 QAM/OFDM) receptions

5.8GHz ETC SiGe-MMIC Transceiver having Improved PA-VCO Isolation with Thin Silicon Substrate

A fully integrated SiGe-MMIC transceiver having a power amplifier (PA), a transmit/receive switch (T/R SW), and a voltage controlled oscillator (VCO) is developed for electric toll collection system (ETC) terminals. To improve the isolation between the PA and the VCO, the back-polish technique of the silicon substrate (127mum thickness) is employed. Electro-magnetic simulation shows that a MMIC of 127mum thickness achieves the isolation improvement of 12.3dB compared with that of conventional 300mum thickness. As a result, the USB/LSB unbalance of the transmitted amplitude shift keying (ASK) signal can be reduced from 4.2dB to 1.2dB at 13dBm output power. The MMIC transceiver fabricated in 0.35mum SiGe BiCMOS process achieves the maximum output power of 15.5dBm with the adjacent channel power ratio (ACPR) of -33.5dBc

A double tuned Ku-band SiGe-MMIC VCO with variable feed-back capacitor

A double tuned Ku-band SiGe-MMIC voltage-controlled oscillator (VCO) with variable feedback capacitor is presented. The proposed VCO employs series varactors in feed-back paths in addition to varactors in tank circuit. By controlling both varactors, this VCO achieves wide tuning range compared to the conventional LC cross-coupled VCO. Furthermore, appropriately biased MOS varactors for feed-back paths realize linear tuning performance. The proposed configuration is experimentally validated with a 0.35 mum SiGe-BiCMOS fully integrated VCO. The oscillation frequency of the fabricated VCO varies 14.3 GHz to 16.2 GHz with 12.5% tuning range, which is increased by 120% from that of the conventional LC cross-coupled VCO.

High linearity SiGe-MMIC Q-MOD having self mixer current control circuit with output power detector for 0.4–5.8GHz cognitive radio transceiver

A 0.4-5.8 GHz high linearity SiGe-MMIC quadrature-modulator (Q-MOD) having a novel self mixer current control circuit is described. This control circuit, which consists of an output power detector and an envelope current feedback circuit, is applied to unit mixers, and it automatically controls the mixer current according to the output power level. As a result, high linearity can be obtained. In simulation, the Q-MOD employing the proposed unit mixers shows the P1dB improvement of more than 2.6 dB under the CW condition of the 0.4-5.8 GHz frequency range compared with the conventional Q-MOD. In measurement, the Q-MOD achieves P1dB improvement of more than 3.0 dB under the same condition. It also improves the maximum output power with EVM of 3.0% (Pout@EVM=3.0%) for both modulation conditions of UHF wireless systems (16 QAM/OFDM, 0.4 GHz) and IEEE 802.11a W-LAN (64 QAM/OFDM, 5.2 GHz).

Fast and highly accurate RF phase detector with analog integrator for APAA system

An RF phase detector employing an analog integrator is proposed for active phased array antenna system. The RF phase detector, consisting of an analog integrator, a mixer and a divider can realize both fast and highly accurate detection at the same time. By setting the integral time of the analog integrator as integral multiple of the half cycle of RF signal, the variation of output voltage due to second harmonic of the mixer output can be prevented. The proposed RF phase detector is fabricated in 0.18μm SiGe-BiCMOS process. It is achieved that the measured accuracy of phase detection is 0.52 deg.-rms in the detection time of 8ns at 1GHz.

A Simple Method of Jitter Evaluation for Designing Phase-Locked Loops for Optical Communication Systems

A simple method for evaluating jitter generation is proposed for phase-locked loops (PLLs) applied to optical communication systems. The precise but complex expressions in the conventional method involving the phase noise of the voltage-controlled oscillator, the jitter-transfer function of the PLL, and integration using a filter function are greatly simplified with the objective of providing a simple estimate of the jitter generation avoiding iterative design procedures. These simplifications together with the data from the International Telecommunication Union (ITU)-T Recommendations lead to an integral-free expression with only a small number of parameters, which enables jitter evaluation using a hand-held calculator. By applying bandwidth limits to the jitter tolerance and transfer specifications, both the sufficient and insufficient conditions for the phase noise of a voltage-controlled oscillator are obtained to enable the efficient design of a PLL with the jitter generation specified in the ITU-T Recommendations.

A low spurious 400M–6GHz SiGe-MMIC Direct Conversion Transceiver using 2ƒ LO LO switching configuration for cognitive radio

A low spurious SiGe-MMIC direct conversion transceiver using 2fLO LO switching configuration for cognitive radio is described. In the proposed configuration, LO signals for Tx and Rx blocks are generated by frequency divider behind switching circuits. By applying this configuration to the transceiver, the offset frequency of maximum Tx spurious in FDD mode is doubled compared to the conventional configuration. Also, theoretical analysis shows that the proposed configuration can lower LO signal spurious level by 12 dB. Through these effects, receiver sensitivity degradation by Tx signal can be avoided and required characteristics of Tx BPF is relaxed. The direct conversion transceiver MMIC using 2fLO LO switching configuration is fabricated in 0.18 mum SiGe-BiCMOS process. Measured results show a high modulation accuracy over 400 M-6 GHz, and low Tx spurious characteristics.

A 5.2 GHz Linearized SiGe Quadrature Modulator Using Current Feedback from Output Buffer

A linearized SiGe up-mixer using current feedback from output buffer is described. The up-mixer consists of a conventional Gilbert cell mixer, an output buffer and a current feedback circuit. According to the output envelope current of the output buffer, the bias current of the mixer is controlled by this feedback circuit. As a result, the proposed up-mixer can realize linearized performance. The simulated P1dB improvements of the proposed up-mixer and the quadrature modulator (QMOD) including this up-mixer are 3.3dB and 1.6dB compared with the conventional types, respectively. The fabricated 5.2 GHz SiGe QMOD achieves the P1dB of -13.9dBm.