L M K 0 3 0 0 0 C
E V A L U A T I O N B O A R D O P E R A T I N G I N S T R U C T I O N S
18
Appendix A: VCO Performance
The internal VCO performance is measured by using a narrow bandwidth loop filter. By default
the narrow loop bandwidth filter is stuffed as Loop Filter #2 in positions C1_AUX, C2_AUX,
C2p_AUX, and R2_AUX and has a loop bandwidth of 77 Hz.
See the Loop Filter section in Board Options for more detail about switching between the two
different loop filters.
Loop Filter
Phase Margin
58.7º
K
φ
100 uA
Loop Bandwidth
77 Hz
f
PD
1.023 MHz
Crystal Frequency
19.44 MHz
Output Frequency
1185 to 1296 MHz
Supply Voltage
3.3 Volts
VCO Gain
10 MHz/Volt
VCO
820 nF
10 uF
820
Ω
150 pF
110 pF
600
Ω
200
Ω
CPout
Charge Pump
C1
C2
R2
R3
R4
C3
C4
This loop filter is located on the top side of the PCB and is selected by placing a
0 ohm resistor on pad R5.
This loop filter has been designed with a very small loop bandwidth to minimize
the PLL from interacting with the noise of the VCO to permit a VCO phase noise
measurement.