Rx Tunings - Nokia NSB-9 Service Manual

NSB-9

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
DTOS_Q
BIQUAD_I_R
BIQUAD_Q_R
BIQUAD_I_C
BIQUAD_Q_C
Item
DTOS_I
DTOS_Q
BIQUAD_I_R
BIQUAD_Q_R
BIQUAD_I_C
BIQUAD_Q_C
Page 44
Calibration of I-channel DtoS collector resistances
Calibration of Q-channel DtoS collector resistances
Calibration of I-channel filter resistances
Calibration of Q-channel filter resistances
Calibration of I-channel filter capacitances
Calibration of Q-channel filter capacitances
Table 1: Channel Select Filter Calibration Limits
Typical value
12...18
12...18
12...20
12...20
Copyright Nokia. All rights reserved.
CCS Technical Documentation
Low limit *)
-6
-6
-6
-6
6...16 -6
6...16 -6
High limit *)
37
37
37
37
37
37
Issue 1 04/03