TY  - RPRT
TI  - An approximate expression for the principal beamwidths of directive antennas in terms of aperture fields 
AU  - Yaghjian, Arthur D
PY  - 1981
PB  - National Bureau of Standards
CY  - Gaithersburg, MD
SN  - NBS IR 81-1644
DO  - 10.6028/NBS.IR.81-1644
ER  -