An Experimental Comparison Between Direct and Indirect PAM by a High-Efficiency Microwave Frequency Multiplier with Varactor Diodes (Correspondence)

Two pulse amplitude modulation (PAM) methods by a high-efficiency frequency multiplier with varactor diodes are compared. Typical results achieved for an X-band to Q-band tripler prove that the direct PAM is better than the indirect one under the same conditions. The former acts as a pulse shaper (PS), and has an output rise time smaller than the rise time of the output voltage of the modulator chain.