TABLE OF CONTENTS In MTs like mobile phones equipped with small antennas, more or less radiation current flows on the conducting materials such as ground planes of the circuit board, metal chassis, and so forth. When evaluating the antenna performance, these currents should be included along with the currents on the antenna element. Care must be taken when the antenna performances are measured, because currents induced on the outside of the RF coaxial cable connecting the test antenna and the instrument may disturb accurate measurement. Conventionally, the radiation pattern is measured by using a voltage controlled oscillator (VCO) in the MT, instead of using a coaxial cable to avoid the disturbance due to the extra current on the cable. However, this method has a disadvantage that it cannot measure the phase pattern, but only the amplitude pattern when measuring radiation patterns of the antenna under test, because it cannot transmit the reference signal to the receiver of the measurement system. In addition, the radiation patterns cannot be measured in multiple frequencies at the same time, because the frequency is fixed to that of the VCO. If multifrequency measurements should be performed, the frequency of the VCO should be changed each time for the different frequency measurement. A disadvantage of doing this is the extra time required. In order to avoid these complexities, a novel measurement method was developed [134]. Figure 5.94 illustrates this system, where RF signals from a synthesizer are transformed...
