Exp.6 Studies of Antenna Introductions Antenna is a device which can effectively transmit or receive electromagnetic waves.There have many different types of antennas for different applications.One important parameter describing the antenna electrical properties is directivity.For different application,the directivity may different.The directivity of the antenna is generally refers to the angular dependence when the antenna transmits or receives EM radiation energy.In principle,one can have the answer by solving the Maxwell's equations with corresponding boundary condition.However,this is a much more complex than it looks like.You may refer monographs for details.Here we only study the directivity of antenna through experiments. Different Types of Antenna 1.Dipole Antenna: This kind of antennas is composed of two identical straight wires.Its radius is a,and the length is /This antenna is widely used in various wireless communication devices. Ignoring the radiation-induced attenuation effect and the transducer thickness effect,the normalized direction function can be expressed as: f(0)=cos(BIcos0)-cos(B) f()mx sin 0 Where B=2/A is phase coefficient.The figures following are the functions for different I Fig.1 I/A=0.25 Directivity Function Fig.2 /A=0.5 Directivity Function 101 840- 1 85- 17 1 20 Fig.3 I/A=0.75Dirctivity Function Fig.4 I/A=1 Directivity Function17 Exp.6 Studies of Antenna Introductions Antenna is a device which can effectively transmit or receive electromagnetic waves. There have many different types of antennas for different applications. One important parameter describing the antenna electrical properties is directivity. For different application, the directivity may different. The directivity of the antenna is generally refers to the angular dependence when the antenna transmits or receives EM radiation energy. In principle, one can have the answer by solving the Maxwell's equations with corresponding boundary condition. However, this is a much more complex than it looks like. You may refer monographs for details. Here we only study the directivity of antenna through experiments. Different Types of Antenna 1. Dipole Antenna: This kind of antennas is composed of two identical straight wires. Its radius is a, and the length is l. This antenna is widely used in various wireless communication devices. Ignoring the radiation-induced attenuation effect and the transducer thickness effect, the normalized direction function can be expressed as:       ( ) sin cos( cos ) cos( ) ( ) max f l l f − = Where β=2π/λ is phase coefficient. The figures following are the functions for different l l l Δ 2a 0.0 0.2 0.4 0.6 0.8 1.0 0 30 60 90 120 150 180 210 240 270 300 330 0.0 0.2 0.4 0.6 0.8 1.0 Fig. 1 l/λ=0.25 Directivity Function 0.00 0.25 0.50 0.75 1.00 0 30 60 90 120 150 180 210 240 270 300 330 0.00 0.25 0.50 0.75 1.00 Fig. 2 l/λ=0.5 Directivity Function 0.00 0.25 0.50 0.75 1.00 0 30 60 90 120 150 180 210 240 270 300 330 0.00 0.25 0.50 0.75 1.00 Fig. 4 l/λ=1 Directivity Function 0.00 0.25 0.50 0.75 1.00 0 30 60 90 120 150 180 210 240 270 300 330 0.00 0.25 0.50 0.75 1.00 Fig. 3 l/λ=0.75Dirctivity Function