Nokia 9110 Service Manual
PAMS
Technical Documentation
RAE–2
BS8_RF
Page 3 – 14
Original 02/99
ing signals. Selectivity is required in this place, because of needed lineari-
ty and adjacent channel interferers will be on too high signal level for the
stages following.
ty and adjacent channel interferers will be on too high signal level for the
stages following.
The next stage in the receiver chain is AGC–amplifier. It is integrated into
SUMMA–ASIC. The AGC has got analog gain control. The control volt-
age for the AGC is generated with DA–converter in COBBA in baseband.
AGC–stage provides accurate gain control range ( min. 57 dB ) for the
receiver.
SUMMA–ASIC. The AGC has got analog gain control. The control volt-
age for the AGC is generated with DA–converter in COBBA in baseband.
AGC–stage provides accurate gain control range ( min. 57 dB ) for the
receiver.
After the AGC there is the second mixer, which generates the second in-
termediate frequency, 13 MHz. The local signal is generated in SUMMA
by dividing VHF–synthesizer output ( 232 MHz ) by four, so the 2nd LO–
frequency is 58 MHz.
termediate frequency, 13 MHz. The local signal is generated in SUMMA
by dividing VHF–synthesizer output ( 232 MHz ) by four, so the 2nd LO–
frequency is 58 MHz.
The 2nd IF–filter is a ceramic bandpass filter at 13 MHz. It attenuates ad-
jacent channels, except for +/– 200 kHz there is not much attenuation.
Those +/– 200 kHz interferers are filtered digitally by the baseband. So
the RX DACs are so good, that there is enough dynamic range for the
faded 200 kHz interferer. Also the whole RX has to be able to handle sig-
nal levels in a linear way
jacent channels, except for +/– 200 kHz there is not much attenuation.
Those +/– 200 kHz interferers are filtered digitally by the baseband. So
the RX DACs are so good, that there is enough dynamic range for the
faded 200 kHz interferer. Also the whole RX has to be able to handle sig-
nal levels in a linear way
After the 13 MHz filter there is a buffer for the IF–signal, which also con-
verts and amplifies single ended signal from filter to balanced signal for
the buffer and AD–converters in COBBA. Buffer in SUMMA has got volt-
age gain of 36dB and buffer gain setting in COBBA is 0 dB. It is possible
to set gainstep ( 9.5 dB ) into COBBA via control bus, if needed..
verts and amplifies single ended signal from filter to balanced signal for
the buffer and AD–converters in COBBA. Buffer in SUMMA has got volt-
age gain of 36dB and buffer gain setting in COBBA is 0 dB. It is possible
to set gainstep ( 9.5 dB ) into COBBA via control bus, if needed..
Transmitter
The transmitter chain consists of IQ–modulator, upconversion mixer, pow-
er amplifier and there is a power control loop.
er amplifier and there is a power control loop.
I– and Q–signals are generated by baseband in COBBA–ASIC. After
post filtering ( RC–network ) they are fed into IQ–modulator in SUMMA. It
generates modulated TX IF–frequency, which is VHF–synthesizer output
divided by two, that is 116 MHz. The TX–amplifier in SUMMA has two se-
lectable gain levels. Output is set to maximum via control register of
SUMMA. After SUMMA there is a bandpass LC–filter for noise and har-
monic filtering before the signal is fed for upconversion into final TX–fre-
quency in CRFU_1a.
post filtering ( RC–network ) they are fed into IQ–modulator in SUMMA. It
generates modulated TX IF–frequency, which is VHF–synthesizer output
divided by two, that is 116 MHz. The TX–amplifier in SUMMA has two se-
lectable gain levels. Output is set to maximum via control register of
SUMMA. After SUMMA there is a bandpass LC–filter for noise and har-
monic filtering before the signal is fed for upconversion into final TX–fre-
quency in CRFU_1a.
Upconversion mixer in CRFU_1a is a so called image reject mixer. It at-
tenuates the unwanted sideband in the upconverter output. The mixer
itself is a double balanced Gilbert cell. The phase shifters required for
image rejection are also integrated. The local signal needed in upconver-
sion is generated by the UHF–synthesizer, but buffers for the mixer are
integrated into CRFU_1a.
tenuates the unwanted sideband in the upconverter output. The mixer
itself is a double balanced Gilbert cell. The phase shifters required for
image rejection are also integrated. The local signal needed in upconver-
sion is generated by the UHF–synthesizer, but buffers for the mixer are
integrated into CRFU_1a.
The output of the upconverter is buffered and matching network makes a
single ended 50 ohm impedance.
single ended 50 ohm impedance.
The next stage is a TX interstage filter, which attenuates the unwanted
signals from the upconverter, mainly LO–leakage and image frequency
signals from the upconverter, mainly LO–leakage and image frequency