PLUTO
INITIALISATION
Transmit
On power-up or reset (RESETB) the Tx reconstruction
filters are tuned to give the specified cut-off frequency. This
calibration is internal and requires no external input. The
calibration time is 1ms.
Receive
On power-up or reset (RESETB) an autocalibration algo-
rithm is started which can be used to tune the programmable
filters in Jupiter. (Jupiter is a programmable active filter de-
signed for use in dual mode CDMA/AMPS system -further
details of which can be found in the Jupiter Datasheet). The
autocalibration is also initiated when Pluto is switched into
CDMA mode via FMB control.
When Pluto enters calibration mode the En Test (pin 68)
goes high. A test signal at 364kHz is then generated at the
Vtest output (pin 67). This signal is input to Jupiter which
provides a response which is digitised by the I and Q Rx ADCs.
An output DAC - BAL - (Pin 71) then tunes the Q channel to
match the I and Q channel amplitude via a successive approxi-
mation routine. The test signal is then switched to 728kHz
which is above the required cut off of the filter. DAC outputs,
FC_I and FC_Q are then adjusted to tune the I and Q filters to
the correct amplitude with reference to the in band test signal.
The filter cut off is tuned to 690kHz. Oversampling in the Rx
ADC's ensures sufficient accuracy for the calibration. This
calibration routine takes 26ms and after completion En Test
goes low and the test signal Vtest is disabled. Only the CDMA
filter is tuned, the matching within Jupiter ensures that the FM
(AMPS) filter performance meets specification.
0
-0.8
-4
CDMA TX FILTER RESPONSE
0
-0.6
FM TX FILTER RESPONSE
Relative
Amplitude
(dB)
Relative
Amplitude
(dB)
-5.8
-3.0
1k
630k
Frequency (Hz)
1.25M
10M
10k
29k
100k
Frequency (Hz)
Figure 9 Baseband RX interface circuit
9
MITEL [ MITEL NETWORKS CORPORATION ]
