NSB-9
CCS Technical Documentation
Page 44
Copyright
Nokia. All rights reserved.
Issue 1 04/03
RX tunings
Channel Select Filter Calibration
Description
Rx Channel select filter is tuned only in one band. The Hagar RF IC contains tunable fil-
ters for the I and Q channels. The calibration of these filters is carried out with a calibra-
tion circuit integrated in the IC.
By writing different control words to the Calibration Control Register in Hagar, internal
switches will connect various RC combinations between the TXC input line and the RXQ
output line.
During the calibration, the DSP generates a 67.71 kHz sine wave on the TXC line and
simultaneously receive the measured response from the Hagar on the RXQ line.
Altogether 6 measurements are made. The first measurement is a reference measure-
ment where the TXC signal is routed directly to the RXQ line without going through any
filter. The remaining 5 measurements are all done on first order low pass filters with a
nominal corner frequency of 67.71 kHz. This means that the received signal on the RXQ
line ideally will have an amplitude of 0.707 times the amplitude of the TXC.
Saved tuning values are:
DTOS_I
Calibration of I-channel DtoS collector resistances
DTOS_Q
Calibration of Q-channel DtoS collector resistances
BIQUAD_I_R
Calibration of I-channel filter resistances
BIQUAD_Q_R
Calibration of Q-channel filter resistances
BIQUAD_I_C
Calibration of I-channel filter capacitances
BIQUAD_Q_C
Calibration of Q-channel filter capacitances
Table 1: Channel Select Filter Calibration Limits
Item
Typical value
Low limit *)
High limit *)
DTOS_I
12...18
-6
37
DTOS_Q
12...18
-6
37
BIQUAD_I_R
12...20
-6
37
BIQUAD_Q_R
12...20
-6
37
BIQUAD_I_C
6...16
-6
37
BIQUAD_Q_C
6...16
-6
37