Trim Skew and PLL Design Considerations
2
Tilt Control and PLL design considerations Introduction Traditional Phase Locked Loop designs include Voltage Controlled Oscillators (VCO) which are used to convert to the voltage value to a frequency value and are key component of the feedback control system. With proper design principles, the variations introduced in the loop get settled with the response of the type of the loop designed. The assumption of the design is that the components are linear, including the VCO. Because of the feedback control, the loop could get settled, even if the VCO is not linear. This application note discusses the effects of non linear VCOs and Rakon’s patented techniques to include “Tilt Control”. Background Applications that need high stability clocks use Temperature Compensated crystal based oscillators. One such application is Small Cells, the radio access nodes that support lower capacity and lower range compared to a tradition Macro node. The requirement for overall stability on the air interface of such radios is 50ppb to 250ppb accurate compared to a network master clock as defined by the 3GPP standards. ---- Typical PLL implementation [ Ullas] TCXO performance [Ullas] TCXO behaviour – Temperature Vs Frequency at constant input voltage TCXO behaviour –Input Voltage Vs Frequency at constant temperature TCXO behaviour –Input Voltage Vs Frequency at varying temperature [Harlow] The effect of Trim Skew [Ullas] Effect of non linearity on PLL design [Harlow] Impact of PLL behaviour on Small Cells [Ullas]
Transcript of Trim Skew and PLL Design Considerations
Tilt Control and PLL design considerations
Introduction
Traditional Phase Locked Loop designs include Voltage Controlled Oscillators (VCO) which are used to convert to the voltage value to a frequency value and are key component of the feedback control system. With proper design principles, the variations introduced in the loop get settled with the response of the type of the loop designed. The assumption of the design is that the components are linear, including the VCO. Because of the feedback control, the loop could get settled, even if the VCO is not linear. This application note discusses the effects of non linear VCOs and Rakon’s patented techniques to include “Tilt Control”.
Background
Applications that need high stability clocks use Temperature Compensated crystal based oscillators. One such application is Small Cells, the radio access nodes that support lower capacity and lower range compared to a tradition Macro node. The requirement for overall stability on the air interface of such radios is 50ppb to 250ppb accurate compared to a network master clock as defined by the 3GPP standards.
----
Typical PLL implementation [ Ullas]
TCXO performance [Ullas]
TCXO behaviour – Temperature Vs Frequency at constant input voltage
TCXO behaviour –Input Voltage Vs Frequency at constant temperature
TCXO behaviour –Input Voltage Vs Frequency at varying temperature [Harlow]
The effect of Trim Skew [Ullas]
Effect of non linearity on PLL design [Harlow]
Impact of PLL behaviour on Small Cells [Ullas]
