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9129AS–DAB–04/08
ATR2732N3
3. Functional Description
The ATR2732N3 front-end IC was developed as a tuner IC for DAB reception. It was designed
for operation in L-band (1452 MHz to 1492 MHz) and VHF BIII (167 MHz to 240 MHz). The front
end contains gain-controlled LNAs, an L-band mixer with a corresponding PLL, and a VHF-band
mixer with a fractional PLL. The IF path contains three gain-controlled amplifiers. The front-end
IC allows the use of automatic tuning, which contains an adjustable input filter for VHF BIII and
an adjustable preselection filter for L-band and VHF reception.
The high dynamic range of the RF inputs, the use of gain-controlled amplifiers and gain-con-
trolled mixers in the RF and IF path, and an integrated driver for an external PIN diode
attenuator (VHF band) offer the possibility of handling even strong RF input signals.
The RF and IF parts include AGC functional blocks, which are needed for proper operation. The
thresholds are programmable via a simple serial bus.
The SPI bus is used to adjust and control all functional blocks.
The following sections briefly describe the major functions and features.
3.1 Main Functions
The following description gives a short overview of the general signal flow using the ATR2732N3
front-end IC for reception of DAB signals. Numbers in the text refer to the numbers in Figure 3-1
on page 6.
A DAB signal in the L-band frequency range (1452 MHz to 1492 MHz) is received by the L-band
antenna; a separate LNA with a separate input is available for the VHF Band III signals. In both
cases, the signal is band-pass filtered using a filter with low insertion loss. The internal variable
gain LNA (for L-band (1), for Band III (3)) amplifies the signal. For the L-band reception, a sec-
ond band-pass filter is placed between the LNA output and mixer input at (2). This mixer
converts the L-band signal to the VHF BIII frequency range (167 MHz to 240 MHz). The signal
leaves the IC at point (4), followed by an external preselection filter.
This filter has an automatic tuner adjustment; that is, the tuning-voltage-generation block adjusts
the pass band of this filter to the desired frequency. After passing this filter, the RF signal is
down-mixed to a fixed IF frequency of 38.912 MHz. The IF signal is amplified and passed to a
SAW filter (5). The first IF variable-gain amplifier is followed by an IF filter at position (6). This fil-
ter is used as an anti-alias-filter. Finally, the DAB signal is amplified using the 2nd IF amplifier.
The signal leaves the front-end IC at (7), giving the signal to the DAB baseband IC.
