Product Manual

Product Manual for Tornado Radio Unit
32
7.3.1.1 To Calibrate The TX Side
1. Refer to the above figure. Connect Port 1 to TX Port, connect Port 2 to Antenna Port, Connect 50ohm
Load to Rx Port, Connect +5V (If you keep the duplexer in the chassis, with +5V connected, you can use
the radio +5V by powering the radio unit during calibration).
2. Ensure TX and Rx duplexer is completely detuned away from the frequency of operation.
3. With TX frequency set to marker 1, Tune 2Tx to peak at marker 1 (note #TX represents the tuning slug
and is marked on the printed circuit board). When tuning ensure that the slug height is not greater
than 5.6mm higher than the printed circuit board, otherwise the slug will contact the chassis.
4. Tune 3TX peak such that two peaks are centred around Marker 1
5. Tune 1TX and 4TX such that the pass band (S21) and return loss (S11) are within acceptable limits.
Acceptable limits will vary across the band. As a guide a pass band loss of approximately 3.4dB and return
loss of greater than 18dB are considered acceptable.
6. Tune notch trimmer, TP2, such that Marker 2 is in the centre of the notch. You should target at least 60dB
of notch rejection; however, this will increase to approximately 65dB of rejection when the Rx side is tuned.
7.3.1.2 To Calibrate The Rx Side
1. Ensure the source power from the VNA is less than -15dBm for the Rx port to avoid overloading the LNA
on the duplexer printed circuit board.
2. Connect Port 1 to the Antenna Port, connect Port 2 to Rx Port, connect a 50ohm load to TX Port, Connect
+5V.
3. Ensure Rx is completely detuned.
4. Tune 2RX to peak at Marker 2.
5. Tune 3RX to peak such that two peaks are centred around Marker 2.
6. Tune 1RX and 4RX such that the pass band (S21) and return loss (S11) are within acceptable limits.
Acceptable limits will vary across the band. As a guide a pass band gain of approximately 10.5dB and
return loss of greater than 15dB are considered acceptable.
7. Tune notch trimmer, TP1, such that Marker 1 is in the centre of notch. You should target at least 50dB of
notch rejection. In addition to the gain of 10.5 the total notch rejection relative to the pass band will be
greater than 60dB.
8. Recheck TX Tuning to ensure that the Rx hasn’t upset the match and to confirm that the TX notch depth
is approx. 65 dB or greater. If the TX match has changed it is likely that 1TX will need to be re-tuned to
correct for the Rx interaction.
9. Once both channels have been re-tuned then reconnect the four duplexer coax cables to the RF board,
reconnect +5V and assemble the chassis. Ensure the two O-ring seals are fitted and the main radio
seal around the perimeter of the unit is seated firmly in its channel on the digital side of the clam
shell. Once the radio is reassembled proceed with power calibration as per Section 6.5.
7.4 RSSI CALIBRATION
The RSSI and AGC control voltage are in linear relationship, as shown in formula 1.
RSSI = A x Vagc + B (1)
Where A represents the slope of the curve and B is the offset.
NOTE: The RSSI reading has an uncertainty of +/- 1.5dB
To find out A and B value we need two points (RSSI1, Vagc1) and (RSSI2, Vagc2), which are obtained by applying
-40dBm and -60dbm signal at the receiver and recording the AGC voltage respectively.