Testing of a read channel for hard disk drives (HDD) requires an extremely high-speed arbitrary waveform generator (AWG) to emulate Lorentzian waveforms for read functional tests. If a sampling rate required to the AWG exceeds the maximum available rate of the instrument, a possible solution is to use two AWG's together running at the same rate synchronously and generating signal alternately to make their equivalent sampling rate doubled. One of the key components of such interleaving AWG is a high-speed analog selector. However it is not easy to find a good selector in ultra high frequency range. An application note proposes a practical solution that is a pseudo interleaving AWG. It is a variation of traditional signal combining method using a power combiner instead of a high-speed selector. This paper describes about performance analysis and experimental results of the pseudo interleaving compared to a true interleaving. Data stored in two AWG's are created with the same method as the true interleaving AWG. The data are simply distributed alternately into each AWG. The results show that the pseudo interleaving works well in spite of its simple structure and can be useful for generating Lorentzian waveforms