Design of Broadband Transmitter Based on Multichannel Parallel Modulations

With the rapid growth of science and technology, the requirements for signal performance indicators in terms of radar, wireless communication, electronic testing and other fields are increasingly stringent. Therefore, the systems based on traditional hardware architecture cannot meet current requirements. Combined with superheterodyne and zero intermediate frequency transmitter architectures, this article presents a new transmitter architecture based on multichannel parallel piecewise modulation to satisfy the indicator of instantaneous bandwidth. The core circuit of the architecture is designed with a piecewise homodyne quadrature modulation scheme. That is, an ultra-wideband radio-frequency signal is generated through the multichannel quadrature modulation circuit and combiner based on multichannel digital complex signals with the same bandwidth, which are processed via digital complex mixer and corresponding low-pass filter. To validate the rationality and feasibility of the new transmitter architecture, a platform is built in simulation software, and then the hardware platform is excited by three digital complex signals different in characteristics, namely single-tone signal, dual-tone signal and chirp signal. Simulation results reveal that, compared with two traditional transmitter systems, the implementation of broadband signal transmitter mainly constructed based on multiple low-sampling rate digital-to-analog converters and low-instantaneous bandwidth modulator avoids restrictions of presence or absence of chips and price level on instantaneous bandwidth indicator of the system.