Low Phase Noise Power Distribution Technology in the Design of Reference Frequency Source Circuits

Phase noise is one of the core features in reference frequency source circuits, and directly affects the performance of frequency synthesizer. When a source is used as reference signalits phase noise is transferred to IF signal through down converter circuit, and reduces the signal noise ratio. In multi-channel applications, the number of reference signals should match to the quantity of channels. Thus, a power distribution circuit (including power divider, amplifier and impedance matching circuit, etc.) is adopted to realize the required quantity of reference signals from one input reference signal. However, phase noise is decreased because of the power distribution circuit. Therefore, low noise power distribution circuit technology is strictly important in the design of reference frequency source circuits. In this paper, first, the influence of signal amplitude, amplifier selection, and the layout of reference frequency source circuits are detailed analyzed, according to the measured results. Then, comparisons of different circuits are given to verify the proposed design. Finally, the design method of a low phase noise power divider circuit is introduced for practical applications.