Tam/WB2TT wrote:

I will have to try your configuration. I did C - L - C/2 - L -C, with
C=1000PF, L=2.2uH. According to SWCad, the gain is flat above 2 MHz, but
there is 120 degrees phase shift at 4 MHz, relative to the phase at 100 MHz.

The center component should be 2C, or 2000 pF for your experiment, not
C/2. The circuit is simply two pi networks in cascade, each having all
component reactances equal to the "transmission line" Z0. Each pi
section mimics a quarter wave transmission line.

Roy Lewallen, W7EL