A simultaneous-dual-beam densely interleaved TX linear antenna array

We present a general analysis of a densely interleaved array (DIA) transmitter, which can transmit two independent beams with the same polarization at closely spaced frequencies from the same aperture. We use standard array theory to show that the array factor and bandwidth of the DIA remain comparable to those of a uniform linear array (ULA). The analysis also reveals that the effective isotropic radiated power (EIRP) of the DIA is 3 dB lower than that of a ULA; however, the two beams can be combined into one, which results in an EIRP increase of 3 dB over the same ULA. We validate the theory by building a DIA demonstrator consisting of two 8-element ULAs of reflector-backed dipoles, which have been interleaved with one another with quarter-wavelength spacing, having the same polarization, and two dummy elements on either end. Half of the dipoles operate at 2.39 GHz and the other half at 2.41 GHz. Even with increased mutual coupling between the antenna elements, the active interaction between the two tones does not generate significant mixing products. The DIA offers good versatility and allows for free-space power combining, which can effectively reduce the output power requirements of the transmitting (TX) amplifiers.