Electro-Optic(EO) probing techniques are advancing rapidly in recent years due to their superior performance in characterization of semiconductor devices and circuits. Although the conventional systems can only monitor the amplitude distribution of electric field, some advanced EO probing techniques are able to measure not only the electric-field amplitude, but also direction of the electric field. Because valuable information can be released in such as chamfered bending transmission lines, patch antennas and wireless devices, etc., EO probing technique becomes an important tool to the characterization of radio frequency devices. These systems often require two beams or two different EO crystals to differentiate the directions of the electric field under test because only one type of EO modulation, compressed/stretched deformation modulation, is utilized in the measurement. Therefore, the measurements are inaccurate and complicated due to the fact that the path length and EO interaction strength of the two probing beams are different. In this research, we demonstrate the EO probing technique with one beam and one EO crystal to extract 2-D electric-field vector using an additional modulation effect, i.e. rotational deformation modulation. This electric field vector measurement technique is compact, accurate and low cost. We not only prove that on-wafer 2-D electric-field-vector measurement using single-beam electro-optic probing technique is feasible theoretically and experimentally, but also combine rotational deformation modulation and compressed/stretched deformation modulation to a practical circuit measurement. Commercial software, Ansoft Maxwell 3-D Field Simulator, is employed to verify our measurements. Good agreement is obtained between experiment and simulation results. In addition to 2-D electric-field-vector measurement, we made an attempt to high-frequency real-time measurement. With the trend of low voltage operation in wireless communication, the most serious issue of high-frequency real-time EO probing technique is the improvement of signal to noise ratio. We tried to improve the stability of laser source, control the polarization of incident beam, and utilize Fabry-Perot filter in order to implement high-frequency real-time measurement. A bandwidth of 900 MHz was achieved, which is record-high to our knowledge.