In this paper, a low-noise preamplifier for MRI is designed and studied. A noise matching network consisting of three elements is presented. To the single-stage AsGa-FET preamplifier working at 128 MHz, the measured g...In this paper, a low-noise preamplifier for MRI is designed and studied. A noise matching network consisting of three elements is presented. To the single-stage AsGa-FET preamplifier working at 128 MHz, the measured gain through network analyzer (HP8712C) and noise figure through noise figure analyzer (8970B) are 25 and 0.43 dB, respectively.展开更多
This paper reports a wideband passive mixer for direct conversion multi-standard receivers.A brief comparison between current-commutating passive mixers and active mixers is presented.The effect of source and load imp...This paper reports a wideband passive mixer for direct conversion multi-standard receivers.A brief comparison between current-commutating passive mixers and active mixers is presented.The effect of source and load impedance on the linearity of a mixer is analyzed.Specially,the impact of the input impedance of the transimpedance amplifier（TIA）,which acts as the load impedance of a mixer,is investigated in detail.The analysis is verified by a passive mixer implemented with 0.18 μm CMOS technology.The circuit is inductorless and can operate over a broad frequency range.On wafer measurements show that,with radio frequency（RF） ranges from 700 MHz to 2.3 GHz,the mixer achieves 21 dB of conversion voltage gain with a-1 dB intermediate frequency（IF） bandwidth of 10 MHz.The measured IIP3 is 9 dBm and the measured double-sideband noise figure（NF） is 10.6 dB at 10 MHz output.The chip occupies an area of 0.19 mm2 and drains a current of 5.5 mA from a 1.8 V supply.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 60871001)
文摘In this paper, a low-noise preamplifier for MRI is designed and studied. A noise matching network consisting of three elements is presented. To the single-stage AsGa-FET preamplifier working at 128 MHz, the measured gain through network analyzer (HP8712C) and noise figure through noise figure analyzer (8970B) are 25 and 0.43 dB, respectively.
基金Project supported by the National Science and Technology Major Project (No.2010ZX03007-002-01)the State Key Development Program for Basic Research of China (No.2010CB327404)
文摘This paper reports a wideband passive mixer for direct conversion multi-standard receivers.A brief comparison between current-commutating passive mixers and active mixers is presented.The effect of source and load impedance on the linearity of a mixer is analyzed.Specially,the impact of the input impedance of the transimpedance amplifier（TIA）,which acts as the load impedance of a mixer,is investigated in detail.The analysis is verified by a passive mixer implemented with 0.18 μm CMOS technology.The circuit is inductorless and can operate over a broad frequency range.On wafer measurements show that,with radio frequency（RF） ranges from 700 MHz to 2.3 GHz,the mixer achieves 21 dB of conversion voltage gain with a-1 dB intermediate frequency（IF） bandwidth of 10 MHz.The measured IIP3 is 9 dBm and the measured double-sideband noise figure（NF） is 10.6 dB at 10 MHz output.The chip occupies an area of 0.19 mm2 and drains a current of 5.5 mA from a 1.8 V supply.
