ISL5217KI Intersil, ISL5217KI Datasheet - Page 9

• Manufacturer Part Number: ISL5217KI
• Description: Up/Down Conv Mixer 2.5V 196-Pin BGA
• Manufacturer: Intersil

Specifications of ISL5217KI

• Package: 196BGA
• Maximum Power Dissipation: 1970 mW
• Operating Supply Voltage: 2.5 V

Modulation Mode 00 - QASK
This modulation mode configures the QPUC as a BPSK,
QPSK, OQPSK, MSK or m-QAM modulator. The block
diagram is shown in Figure 7. The data FIFO outputs are
routed to the shaping filters. Here the samples are
interpolated by 4, 8, or 16 and shaped using a FIR filter with
up to a 256 taps. The filter impulse response can span 4-16
input samples. A half (input) sample delay can be inserted in
the I/Q path after the FIR and is enabled through Main
Control (0xc, bit 13). The 20-bit output of the shaping filter is
routed through a gain adjust multiplier controlled by 0x0a,
bits 11:0 and into the interpolation filter. The interpolation
filter interpolates by a factor set in the resampling NCO with
the Interpolation Phases controlled by 0xd, bits 1:0. The
output of the interpolation filter is at the master clock
frequency, CLK. The samples are then mixed with the carrier
L.O. for quadrature upconversion. The output is then
summed with the cascade input signal, saturated (in the
case of overflow), and formatted for output.
Modulation Mode 01 - FM with Bandlimiting Filter
This mode configures the QPUC as an FM modulator with
post-modulation filtering. The block diagram is shown in
Figure 8. This mode provides for FSK and FM modulation
schemes. In this mode, the I input samples drive the
frequency control section of a quadrature NCO to produce a
zero IF FM signal. The 16-bit FM quadrature signals are then
routed to the shaping FIR filter and into the interpolation filter
for bandlimiting and interpolation up to the master clock rate.
The quadrature filtered FM signals are then upconverted to
the carrier frequency by the carrier NCO and mixers. The
output is then summed with the cascade input signal,
saturated (in the case of overflow), and formatted for output.
Note that pulse shaping in this mode must be provided prior
to the QPUC.
Modulation Mode 10 - FM with Pulse Shaping
This mode configures the QPUC as a FM modulator with
pre-modulation baseband pulse shaping. The block diagram
is shown in Figure 9. The data from the FIFO (I channel only)
is routed to the FIR shaping filter. The FIR shaping filter
output drives the frequency control section of a quadrature
NCO to produce a zero IF FM signal. These 18-bit FM
I
Q
I
MODULATOR
FM
SHAPING
FILTER
FIGURE 8. FM WITH BANDLIMITING
FIGURE 7. QASK
SHAPING
FILTER
PROFILE
GAIN
9
PROFILE
GAIN
TO
HALFBAND
ISL5217
modulated quadrature samples are then up sampled in the
interpolation filter to the output sample rate. The baseband
modulated signal is then upconverted to the carrier
frequency by the carrier NCO and mixers. The output is then
summed with the cascade input signal, saturated, and
formatted for output.
In Mode 10, the amplitude out of the shaping filter needs to
be limited in order to prevent frequency excursions that
cannot be filtered out in the interpolation filter.
NOTE: THE QUALITY OF THE FM SIGNAL IS AFFECTED BY
THE AMPLITUDE SLEW RATE OUT OF THE SHAPING FILTER.
AS A RULE OF THUMB, LIMITING THIS SLEW RATE TO LESS
THAN 1/8 THE SAMPLE RATE WILL MINIMIZE THIS
DISTORTION.
FM Modulator
The FM modulator provides for frequency modulation of the
carrier center frequency by the QPUC input data. The FM
modulator is driven either directly by the QPUC I input (Mode
01) or by the output of the FIR shaping filter (Mode 10). The
input data to the FM Modulator, is defined as dφ(n)/dt, where
φ(nT) is the phase of a theoretical sinusoid described by:
The block diagram is shown in Figure 10. The input to the
FM modulator, dφ(n)/dt, is integrated via the NCO
accumulator. The NCO accumulator output represents
phase and is used to address a SIN/COS generator,
synthesizing a sinusoid of the form described in
Equation 1. The phase accumulator feedback of the NCO is
20 bits and 18 bits of the phase word are routed to the
SIN/COS generator. Eighteen bits of amplitude are
provided on the Sine and Cosine outputs.
The transfer function of the FM modulator is defined by the
change in degrees per sample value, dφ(nT)/dt, where
dφ(nT)/dt is a 16-bit, twos complement, fractionally notated
frequency control word with a range from -F
+F
s n ( )
I
dφ(nT)/dt
01 OR 10
SAMP
MODE
=
FIGURE 10. FM MODULATOR BLOCK DIAGRAM
A (cos φ nT
FM
SHAPING
FILTER
/2. F
16 or 20
FIGURE 9. FM WITH PULSE SHAPING
SAMP
[
(
∑
) ]+ j sin φ nT
is defined as the sample rate into the FM
MODULATOR
FM
[
20
(
)
]); A ≈ 1 in Modulator
>
R
E
G
PROFILE
GAIN
φ(nT)
SAMP
18
18
/2 to
COS[φ(nT)]
SIN[φ(nT)]
July 8, 2005
FN6004.3
(EQ. 1)