Travelling wave magnetic resonance imaging (twMRI) offers to overcome the inhomogeneities due to the standing wave patterns [1-2], and the use of coil arrays with multiple coil elements [3]. The excitation of the spins have been commonly done with RF surface coils, dipole and patch antennas, etc. The resonant device should be able to generate an adequate magnetic field to transmit the signal to a distant object using a waveguide. In this paper, we numerically simulated the magnetic field of the principal mode (TM0) as a function of the driving voltage phase.To investigate how the TM0 magnetic field propagates inside a PPWG for twMRI, numerical simulations were run using the finite element method. Waveguide plates were assumed made out of copper. The surface coil was located at the exterior end of the waveguide and, the phantom was at the opposite end inside the magnet bore. The PPWG was 200 cm long and 16 cm wide and plates were separated 16 cm. The phantom had a 7 cm radius and was 1.5 m away from the RF coil. The surface coil had a 7 cm radius and was linearly driven. The phase of the driving voltage varied from 00 to 3600, to investigate the optimal phase value. The simulated setup used for all simulation is shown in Fig. 1. All simulations were performed along the z-direction at 300 MHz (7 T for protons) with the commercial tool, CST (CST Microwave Studio, Darmstadt, Germany). Electrical constants used in all simulations: a) Destilled-water phantom: μ=0.999991, ε=78.4, σ = 5.55e^-6 S/m, ρ=998 Kg/m³ and, thermal conductivity = 0.6 W/K/m, b) Copper waveguide plates: μ=1, σ=5.8e^-7 S/m, ρ=8930 Kg/m³, thermal conductivity=401 W/K/m.Numerical simulations of the magnetic fields (B₁) as a function of the driving voltage phase for a parallel-plate waveguide were computed. Fig. 2 shows some simulations acquired at different phases along the z-direction. Despite the fact that the transmission coil is outside the imager and 1.50 m away from the phantom, the PPWG is able to transmit the signal. These simulation results were then used to compute B₁ in the phantom for the different phase values. Fig. 3 shows the B₁ variation as a function of the voltage phase. As expected, B1 show a a sinusoidal pattern, reaching its maximum values at 𝜋/2 and 3𝜋/2. Consequently, these two phases represent the optimal values to transmit the RF signal to a distant phantom with a PPWG. Additionally, profiles along the z-direction inside and outside the PPWG were taken for comparison purposes. Fig. 4 shows profiles obtained from the phase 900 simulation. For the green profile, the peak at 50 cm represents the RF coil B₁, and the peak around 2 m is the B₁ inside the spherical phantom. The red profile shows very interesting results because peaks appear right at both waveguide ends. The rest of the B₁ magnitude along the z-direction has a pretty similar magnitude compared to the green profile. This a is rather interesting result, this might imply that it is possible to acquire images outside the PPWG also, whenever the waveguide is inside the magnet bore. It is important to highlight that no dielectric material were use for RF signal transmission at certain resonant frequency. These numerical results demonstrate that it is possible to transmit the RF signal with a specific driving voltage phase using a PPWG and, a simple circular coil to a phantom 1.5 m away outside the magnet.