lecture0902 - x School of Electrical and Computer...

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School of Electrical and Computer Engineering, Cornell University ECE 4880: RF Systems Fall 2015 Lecture 09/02/2015 Reading Assignments: 1. T. H. Lee, The Design of CMOS Radio Frequency Integrated Circuits , 2 nd Ed , Cambridge, 2004. Chap. 3 2. Lecture 2 and 13 of ECE 3030 notes Lecture Flow: Continue the three topics for electromagnetic review: LC resonator for impedance analysis (continuing from 8/31 lecture) Conjugate impedance match From Maxwell equations to the distributed and lumped transmission lines RLC resonator bandwidth and regulations Carriers as a single-tone do not carry identifiable information (it does carry the range information in its time-of-flight or phase shift). Any modulation in amplitude, phase, frequency or code will spread the spectrum usage a little bit. Let’s restrict ourselves first to this small frequency spreading around the center carrier frequency. Actually this will be most of the semester until we generalize to ultra-wide-band (UWB) radios, which we will NOT spend much time in this class. The bandwidth BW = 2 is typically smaller than 1% of the carrier frequency, mostly for the sharing purposes. A typical example for the RFID regulation for one channel is shown below, where f carrier is around 866MHz in EU and 910MHz in US FCC (Federal Communication Commission). BW here is about 0.23% in EU and 0.55% in US in the respective carrier frequency. To share the same “free” space for everyone, central regulation on frequency and power transmission is necessary for wireless communication. If the radio waves are confined in a cable or waveguide (such as cable TV and Internet, or in general, light in optical fibers), only the leakage out of the outer shield needs to be regulated. If the radio waves are confined in a chamber (such as your microwave oven with 2.45GHz operations), again only the leakage is important. Different regions may have different regulations in various frequency bands. Lack of global standards is an additional design burden for RF products, because some circuits need to be tuned to fit the different regulations in a specific country of operation. The other concern is the human health and safety. In the bands between 30MHz to 1GHz, the OSHA (Occupation Safety and Health Administration) regulates the emission has to be lower than 1mW/cm 2 over a six-minute averaging period, mainly for the non-ionizing heat concerns. Higher frequency regulation can be found at OSHA web page: x 1
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fcarrier fcarrier +200kHz fcarrier 200kHz Example: RFID regulation on frequency and bandwid
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