LMX2434EVAL/NOPB National Semiconductor, LMX2434EVAL/NOPB Datasheet - Page 3

• Manufacturer Part Number: LMX2434EVAL/NOPB
• Description: EVAL BOARD FOR LMX2434
• Manufacturer: National Semiconductor
• Series: PLLatinum™r
• Type: Frequency Synthesizer (RF/IF)r

Specifications of LMX2434EVAL/NOPB

• Frequency: 2.5GHz, 5GHz
• For Use With/related Products: LMX2434
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2.0 Optimizing Sensitivity at 6.0
GHz
Now suppose the requirement is to optimize the perfor-
mance at 6.0 GHz for an LO to be used in a particluar
cordless phone application. According to Figure 2, the FinRF
input impedance again lies on the upper half of the Smith
Chart. From the LMX243x UTCSP FinRF Input Impedance
Table, ZFinRF = 7.11 + j28.00Ω at 6.0 GHz.
This time a 0.5 pF shunt capacitor is placed between the
VCO output and the FinRF input of the PLL as shown in
Figure 6. This makes the impedance at 6.0 GHz close to
50Ω as illustrated in Figure 7.
FIGURE 7. LMX243x UTCSP FinRF Input Impedance
FIGURE 6. 0.5 pF Shunt Match at 6.0 GHz
with 0.5 pF Shunt Match
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Figure 8 shows that an approximate 3.0 dB improvement in
sensitivity is achieved at 6.0 GHz with the addition of the 0.5
pF shunt capacitor. Again, this evaluation is performed under
typical conditions, with Vcc = 2.50V and T
Note: The LMX2434 is only guaranteed for operation up to
5.0 GHz. For further information, refer to the LMX2430/33/34
datasheet.
FIGURE 8. LMX243x UTCSP FinRF Input Sensitivity
Improvement at 6.0 GHz
A
= 25˚C.
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