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Eq. 12 MICROSTRIP ANTENNA DESIGN Although the previous text and equations have indicated a significant performance dependence on the width of the microstrip conductor, the astute reader may recognize that no guidelines or formulae have been offered for the width calculation. A practical starting point has been suggested by Bancroft in the following equation: 14 Eq. 13 The procedure for the design of a single element, rectangular microstrip antenna is summarized in Table 3. TABLE 3: MICROSTRIP ANTENNA DESIGN PROCEDURE PROCEDURE NUMBER DESIGN PROCEDURE DESCRIPTION NOTE – COMMENT – REFERENCE 1. Specify: A. substrate dielectric constant – e r B. operational frequency – f o C. substrate height – h A. Preferred values of dielectric constant 2.0 < e r < 6. Higher dielectric constants reduce efficiency B. Desired center frequency C. substrate height should be compatible with achievable line width and impedance levels Bancroft recommends: 2. Calculate the width – W Equation 13. 3. Calculate the effective dielectric constant – e eff Equation 1. 4. Calculate the length extension – DL Equation 2. 5. Calculate the actual length – L Equation 4. Note the terms must be rearranged to solve for L. L is nominally a half-wavelength in the effective dielectric medium 6. Calculate the input impedance at resonance – R in Equation 5. 14 Bancroft, R., Microstrip and Printed Antenna Design, 2nd Ed., Scitech Publishing, Raleigh, NC, 2009, p. 60. ( ) ( ) ( ) ( ) ( ) f q f q q q q p l p p p d d sin sin L k cos cos sin cos cos W k sin I I W D eff o o o ÷ ÷ ø ö ç ç è æ × × ÷ ÷ ø ö ç ç è æ × × ÷ ÷ ÷ ÷ ø ö ç ç ç ç è æ ÷ ø ö ç è æ × = × ÷ ÷ ø ö ç ç è æ = ò ò 2 2 2 2 3 0 0 2 2 2 2 2 where 1 2 2 + × = r o f c W e r o max f c . h e p 2 3 0 < Microstrip Antenna Design 9 www.cadence.com/go/awr