Broadband microwave electric field measurement based on a planar dipole antenna as the local oscillator source

We propose a superheterodyne microwave electric field measurement scheme based on Rydberg atoms that utilizes a planar dipole antenna as the local oscillator source. By designing a two-dimensional asymmetric dipole antenna, broadband microwave near-field radiation is achieved in the region of 1.7 GHz-9 GHz with return loss less than -10 dB, and the feasibility of using a planar antenna as the local oscillator source has been verified through simulations and experiments. In the experiments, high-sensitivity electric field measurements are performed by using near-field radiation from the planar antenna as local oscillator field for three resonant frequencies, 3.999 GHz, 5.048 GHz, and 7.981 GHz, with an optimal sensitivity of 3.16 µV/cm/Hz^1/2. Comparative experiments with a horn antenna as the local oscillator source show that the planar antenna can achieve equivalent measurement sensitivity. Continuous-frequency electric field measurements are also investigated with a planar antenna in the frequency range of 2.5 GHz-9 GHz, and a minimum detectable field strength ranging from 3.16 µV/cm to 25.95 µV/cm is achieved. Our findings provide an alternative design approach for compact superheterodyne Rydberg atomic sensors.