quadrature amplitude and phase mismatch

how to convert quadrature amplitude mismatch in mV to dB?

how to convert quadrature phase mismatch in degrees to dB?

Do youy mean dB of sideband rejection?

There is no representation of phase in dB units.
dB gives the magnitude part only.
If you want to represent the phase also then add the line L_90 degree.
I could not represent the phase symbol above.

If you are in fact referring to phase and amplitude balance as it relates to SSB rejection then
Refer to the link below.

http://www.synergymwave.com/articles...ar-Signals.pdf

BTW, way if you hold down the ALT key and type ( 2, 4, 8 ) you will get the ° symbol.