A fundamental study on the development of a frequency mixer with a field emitter array was conducted. A grid to control the electron beam was introduced to the vacuum triode, which consisted of a field emitter array and an external collector. The transconductance of the field emitter array was 1.3 μS. It was found that the collector current varied linearly with the grid voltage, and the rate of the variation was estimated to be 0.9 μS. It was suggested that the fabricated tetrode would work as a frequency mixer. A preliminary experiment on the mixing of signals with frequencies of 10 and 15 kHz was performed, and the generation of signals with the sum and difference frequencies was confirmed. The possible operating frequency of the field emitter array-based vacuum frequency mixer will be 1 MHz or higher, using a larger field emitter array that can be operated at higher currents. © 2013 American Vacuum Society.