Hi All,
During the Geneva interim a normative Tx/Rx specification at TP0a/TP5a was adopted and incorporated in:
93.8.1.4 Transmitter output return loss
93.8.2.2 Receiver input return loss
94.3.12.4 Transmitter output return loss
94.3.13.2 Receiver input return loss
This specification was intended to correlate to the package return loss as specified for COM @TP0 and TP5. These are specified in:
Table 93–8—Channel operating margin parameters
Table 94–17—Channel operating margin parameters
A concern was brought up that the extrapolation of the package return loss values from the device pins to TP0a and TP5a:
1. took into account the extra waviness of the return loss.
But:
2. Gave extra non relevant margin to the low frequency return loss
I find this concern very reasonable and therefore suggest to fix the limit at TP0a and TP5a to take into account that the test fixture has very minimal loss @ low frequencies.
The way I suggest doing that is by defining the following two sections of return loss:
RL(f) ≥ 6.25*f+10.3125 ; 0.05<f<3 ; f in GHz
I will be referencing this E-mail in the suggestion resolution to the comment I will be submitting.
Inputs are welcome (let’s have the debate here and save the time in Tx J).
Best regards,
--Liav