Signal source structure principle

     1) Reference source part: determines the frequency stability of the entire signal source;
     2) Frequency synthesis part: determines the output signal frequency parameters;
     3) Output power control part: determines the output signal power parameters.

   FIG. 1 is a block diagram of a typical traditional signal source.

Figure 1   Typical signal source block diagram

    Signal power control part:
     1) ALC: maintain the stability of signal output amplitude;
     2) Attenuator: There are two types: mechanical or electronic, to achieve a large output power range (such as: -136dBm ~ +13dBm).
    Frequency synthesis part:
     It is a typical PLL structure, controlling the output frequency range, frequency resolution, spectrum purity, etc.

    Modern signal sources add vector signal generation capabilities on the basis of traditional signal sources, making the signal source a multi-standard signal transmitter.

Figure 2 is a block diagram of the structure of a modern signal source.

Figure 2   Structural block diagram of a modern vector signal source

   The design of the vector signal source can integrate various components onto a PCB to achieve miniaturization of the instrument. The entire MXG signal source is mainly composed of three parts: power module, CPU assembly board, and signal generation assembly board. Figure 3 is the signal generation assembly board of Agilent MXG.

  Figure 3   MXG assembly board