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Circulators are often used in RF systems; however, their size, cost, and weight increase greatly at lower frequencies (<300 MHz). The development of a load-insensitive active quasi-circulator is presented as an alternative for the traditional circulators to be used in low-frequency systems such as Doppler ultrasound. Major challenges to these active devices are limited power and low isolation between non-consecutive ports. The use of current-feedback operational amplifiers allowed higher-power delivery to the load. Simulations using Monte Carlo method showed an isolation >19 dB for 20% of variation of the load impedance. The circuit was implemented and tested with an ultrasound probe in a water tank. The results show that the circuit was able to send and receive signals simultaneously from a single ultrasound transducer element.
References
-
-
1)
-
11. Sedra, A.S., Smith, K.C.: ‘Microelectronic circuits’ (Oxford University Press, New York, NY, USA, 2009, 6th edn.).
-
2)
-
4. El-Khatib, Z., MacEachern, L., Mahmoud, S.A.: ‘A fully-integrated linearized CMOS bidirectional distributed amplifier as UWB active circulator’. Int. Conf. on Microelectronics, 2008 ICM 2008, Sharjah, United Arab Emirates, 2008, pp. 106–109.
-
3)
-
5. Evans, D.H., McDicken, W.N.: ‘Doppler ultrasound: physics, instrumentation and signal processing’ (John Wiley & Sons, Chichester, United Kingdom, 2000).
-
4)
-
12. Metropolis, N., Ulam, S.: ‘The Monte Carlo method’, J. Am. Stat. Assoc., 1949, 44, (247), pp. 335–341 (doi: 10.1080/01621459.1949.10483310).
-
5)
-
7. Wenzel, C.: ‘Low frequency circulator/isolator uses no ferrite or magnet’, RF Des., 1991, 14, pp. 39–43.
-
6)
-
1. Shin, S.-C., Huang, J.-Y., Lin, K.-Y., Wang, H.: ‘A 1.5–9.6 GHz monolithic active quasi-circulator in 0.18 m CMOS technology’, Microw. Wirel. Compon. Lett., 2008, 18, (12), pp. 797–799 (doi: 10.1109/LMWC.2008.2007703).
-
7)
-
3. Kim, J., Krishnamurthy, N., Santini, T., Zhao, Y., Zhao, T., Bae, K.T., Ibrahim, T.S.: ‘Experimental and numerical analysis of b 1 + field and SAR with a new transmit array design for 7t breast MRI’, J. Magn. Reson., 2016, 269, pp. 55–64 (doi: 10.1016/j.jmr.2016.04.012).
-
8)
-
8. Chang, C.-H., Lo, Y.-T., Kiang, J.-F.: ‘A 30 GHz active quasi-circulator with current-reuse technique in CMOS technology’, Microw. Wirel. Compon. Lett., 2010, 20, (12), pp. 693–695 (doi: 10.1109/LMWC.2010.2079321).
-
9)
-
10. Chen, P.-H., Narayanan, R.M.: ‘Design of active circulators using high-speed operational amplifiers’, Microw. Wirel. Compon. Lett., 2010, 20, (10), pp. 575–577 (doi: 10.1109/LMWC.2010.2060317).
-
10)
-
6. Müller, M., Hermes, M., Brückmann, H., et al: ‘Transcranial Doppler ultrasound in the evaluation of collateral blood flow in patients with internal carotid artery occlusion: correlation with cerebral angiography’, Am. J. Neuroradiol., 1995, 16, (1), pp. 195–202.
-
11)
-
2. Linkhart, D.K.: ‘Microwave circulator design’ (Artech House, Norwood, MA, USA, 2014).
-
12)
-
9. Tanaka, S., Shimomura, N., Ohtake, K.: ‘Active circulators – the realization of circulators using transistors’, Proc. IEEE, 1965, 53, (3), pp. 260–267 (doi: 10.1109/PROC.1965.3683).
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