Re: Radar Project - BladeRF2.0

[Doug]

On 6/24/2020 9:03 AM, Dionísio de Carvalho wrote:
> hi everybody
> This is my fisrt message here. I am pretty new in the SDR world.
>
> I am intended to develop a Radar with BladeRF2.0 from Nuand.
> Is anybody in this boat?
>
> I have some start questions that I will be grateful for any help:
>
> - How can I sweep the  Frequency at osmocom-sink?  any idea?
> - How can I figure out the TX power?  I am trying to measure an antenna 
> S21 parameter!
>
> thanks for any help
>
> Att
>
> Dionisio Carvalho
> Sao Paulo University - Brazil

It is not easy to get a valid measurement of antenna gain or radiated 
power. It is easier to design the antenna according to a published 
formula (i.e., plans) and use the gain figures provided by the 
originator. Be careful to observe whether the gain figure is in
reference to isotropic or to a dipole. A dipole has 2.1dB greater gain 
than isotropic.

(An isotropic radiator is a theoretical point-source that radiates
in all directions--all points along a sphere surrounding it. 
Professional antenna engineers use the isotropic source as a
reference point; radio amateurs tend to use a dipole as their reference 
value.)

Now, measure the power out of your transmitter, with an appropriate 
power meter--a lab meter for power levels up to about 10mW (+10dBm) or
a Bird or other higher-power meter for levels greater than +10dBm.
(A lab meter can be used with suitable fixed attenuators of known
value. Be careful not to overload the lab meter!)
Then calculate the effective radiated power: RF power from the 
transmitter times the gain of the antenna. Use the same measurement
units (db, dbm, Watts, numerical gain or dB gain, etc.) to find the 
ERP--effective radiated power.

Values in dB or dBm are ADDED, not multiplied!

--doug, WA2SAY, retired RF engineer