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Antenna Segment Tradeoffs The antenna segment establishes the available RF bands. Although much research has been applied toward creating an “all-band” antenna, multiband radios generally require at least one antenna per decade of RF band (., HF, VHF, UHF, SHF, etc.). In addition, the antenna determines the directional properties of the receiving system. Sectorized antennas, static beamforming arrays, and adaptive beamforming arrays (smart antennas) each have different spatial and temporal properties, the most significant of which is the pattern of transmit and/or receive gain | Software Radio Architecture Object-Oriented Approaches to Wireless Systems Engineering Joseph Mitola III Copyright 2000 John Wiley Sons Inc. ISBNs 0-471-38492-5 Hardback 0-471-21664-X Electronic 7 Antenna Segment Tradeoffs The antenna segment establishes the available RF bands. Although much research has been applied toward creating an all-band antenna multiband radios generally require at least one antenna per decade of RF band . HF VHF UHF SHF etc. . In addition the antenna determines the directional properties of the receiving system. Sectorized antennas static beamforming arrays and adaptive beamforming arrays smart antennas each have different spatial and temporal properties the most significant of which is the pattern of transmit and or receive gain. The antenna may also constrain the phase noise of the overall system. In addition the interface between the antenna and the RF conversion stage determines VSWR insertion loss and other miscellaneous losses. In bands above 100 MHz this interface can determine the overall system noise floor. This chapter characterizes the systems-level antenna segment tradeoffs relevant to SDR architecture. I. RF ACCESS From a SDR perspective the enabling RF-access parameters of the antenna segment are RF band and bandwidth as illustrated in Figure 7-1. Antennatype in the figure lists the mechanical structure and the physical principle on which the antenna is based. Bandwidth is expressed either as a percent of carrier frequency or as a ratio of lowest RF to highest RF over which the antenna efficiency VSWR etc. are workable. Narrowband antennas have only a few percent relative bandwidth. Frequency limits are typically defined in terms of the 3 dB bandwidth of the antenna. An HF antenna for example that is operable between 2 MHz and 20 MHz has a relative bandwidth of 20 2 or 10 1. An antenna that operates effectively between 2 and 4 GHz on the other hand has a relative bandwidth of only 2 1. This ratio is one octave. Wideband .

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