Official bladeRF forum

Hi,
I'm trying to measure the phase shift that a carrier acquires when propagating through a length of cable. I have the bladeRF x40. I simply connect a 1 m sma cable from the TX port to the RX port. I'm using a Matlab script to configure the bladeRF using cli commands. My Tx samples are just ones, so that I just transmit a tone at the carrier frequency at 900 MHz. Then I expect to be able to obtain the phase acquired from propagation through the cable just by atan(imag(rx_sig)/real(rx_sig)). But when I try this, the measured phase is not consistent. It seems to be random between different measurements. Is there some fundamental reason why this won't work? Or am I just not implementing it incorrectly? I don't get why the phase measurement is not repeatable.
I should be able to use this phase measurement along with the permittivity of the cable I'm using, to back out the length of the cable (modulo the wavelength).

The sign does to be sure move at the speed of light for that medium, which is typically some type of plastic protecting the cajole.

Most strong plastics have a dielectric steady of somewhat more than 2, so their speed of light will in general be around the 0.65c territory. Frothed dielectrics have a lower dielectric consistent, so support quicker flags.

To a decent first estimate, you can utilize the equation

length = wavelength(in link) * (stage shift in degrees/360),

where the wavelength(in link) = 0.65c/recurrence = 0.65wavelength(in air)

Assuming you need more precision than that rough 0.65 figure, then, at that point, look into the information sheet for the speed of signs in your particular sort of link.

As the impedance of the link relies upon the sqrt(ratio) of L and C per unit length, and the speed relies upon the sqrt(product) of L and C, the speed and the impedance are not straightforwardly related.