TUA6039 Infineon Technologies Corporation, TUA6039 Datasheet - Page 9

• Manufacturer Part Number: TUA6039
• Description: Stationary - Mopll & Silicon Tuner
• Manufacturer: Infineon Technologies Corporation

5
8.
9.
10. In order to have the confidence in the stability of the loop, an open loop analysis is performed to estimate the
near 10kHz offset at around -150dBc/Hz. The free running oscillator to be phase locked typically has
much higher close-in noise but continues down to around -120dBc/Hz beyond 1MHz. At some offset the
reference noise multiplied up to the output frequency becomes higher than the oscillator's free running
noise. This is the point where normally the loop bandwidth is set. Inside the loop the oscillator noise is
improved by the reference, yet outside the loop is not degraded by the reference. Because of the wide
tuning range of the oscillator, the loop bandwidth should be very carefully chosen with deep consideration
of the noise contribution mechanism.
The phase noise level within the loop bandwidth can be approximated by
One of the most common sources of noise is the power supply to the IC. This can be caused in many
ways, but most commonly are due to supply ripple and electric or magnetic coupling to Vcc line. Proper
PCB layout and necessary AC blocking are critical to ensure decent noise performance. The signal line
with highest level in the Half NIM is the IF output line, and all those sensitive blocks like oscillator, loop
filter and long DC lines should be well-protected from coupling from IF lines.
1.6. IF Block
structure that helps much better adjacent channel rejection. Especially in simul-casting signal
environment as in Fig.5, it is a big advantage combined with internal AGC of TUA6039-2 to efficiently
suppress strong adjacent PAL signals. The tuner provides a balanced IF output to drive directly a SAW
filter. The AGC Controlled amplifier on-chip feeds out the IF signal directly to the demodulator IC.
.
Close
1992, pp.436.
Typically, the crystal oscillator used for the reference has very good phase noise that they levels off
G.Vendelin, A.Pavio, U.Rohde, Microwave Circuit Design using Linear & Nonlinear Techniques, John Wiley & Sons, New York,
TUA6039-2 has separated mixer outputs and SAW driver inputs to realize an IF filter of band pass filter
There are other sources of phase noise that need to be considered when designing the Half NIM.
than C68, i.e.,
A bigger time constant results in somewhat better filtering action, but tends to be associated with lower stability.
gain and phase margin. By closed loop analysis we can obtain the frequency response & transient response of
the loop. We use a mathmatic tool to analyse these parameters though a spreadsheet program is enogh for the
above calculations.
Calculate C65, which is used to damp transients from the charge pump and should be at least 20 times smaller
Calculate R40 & C24 within these limits and the phase noise contribution of R40 by Eq.(5).
_
in
_
phase
Fig. 5 Spectrum of a DVB-T signal between strong analog PAL signals
_
noise
PAL Signal
τ
=
1
Application Notes Revision 3.0
L
R
=
1 (
Φ
39
C
Hz
(
68
=
fm
_
2
×
)
normalized
×
=
R
ζ
39
20
×
,
log
τ
2
I




=
cp
C
K
C
65
vco
×
24
_
Application Engineering
K
phase
≤
×
vco
N
2
R
C
k
40
fm
20
×
×
68
DVB-T Signal
,
_
C
T
noise
68
×
R
8
39
_
ohm




. 0
floor
01
dBc/Hz
<
)
τ
τ
+
2
1
20
<
0
log
1 .
PAL Signal
N
+
(5)
(4)
Communication Solutions
10
IFAP COM Tuner Systems
5
log
f
ref
May 2007
(6)