Masashi Nogawa, Sr. Member of Technical Staff, Qorvo

Published on Microwave

Explore the world of RF power supply and the challenges that power rails present in noise-sensitive RF and signal chain applications. In ‘PSRR in the Real World,’ authored by Masashi Nogawa, a Senior Member of Technical Staff at Qorvo. This article published on August 3, 2023, is an essential read if you are working in the RF field. Understand how to optimize your systems for peak performance and minimal noise interference.

 In this blog post, we continue our investigation into a VRM’s Power Supply Ripple Rejection (PSRR) performance. In earlier posts, we reviewed PSRR concepts by running a couple of simulations and now we power up a real VRM in the lab.

Our DUT (Device under Test) is the VRTS1.5 ‘Voltage Regulator Test Standard’ from Picotest (thanks to Mr. Steve Sandler for the board).

By using the Bode 100 Vector Network Analyzer (VNA) from Omicron Lab, together with the J2121A High Power Line Injector (though it doesn’t need to be ‘high current’ – this is what I had available in my lab), we get this PSRR plot (Figure 1).

Figure 1: VRTS1.5 PSRR curve

My lab setup for obtaining this curve is shown in Figure 2. In this setup, everything is straightforward except for one point: I’m using four series load resistors of 50? each, a total of 200?, into the 50? terminated input ‘port 1’ of the Bode 100 unit, to form ×1/5 attenuation. This avoids too high current loading on the VRTS1.5 DUT.

Read the full article here – PSRR in the Real World | Microwave Journal