Time synchronizing apparatus for mobile WiMAX analyzer
Disclosed herein is a time synchronizing apparatus for a mobile WiMAX analyzer. The time synchronizing apparatus includes a Global Positioning System (GPS) receiver and a synchronization control unit. The GPS receiver outputs a GPS signal that is synchronized with the GPS time using information received from a GPS satellite. The synchronization control unit compares the GPS signal and a reference signal, which is generated using an internal clock, and controls synchronization according to the result of the comparison. The synchronization control unit includes an oscillator, a divider, an offset comparison unit and a processor. The oscillator outputs an oscillation signal having a predetermined frequency. The divider divides the oscillation signal into the reference signal. The offset comparison unit compares the differences between the GPS signal and the reference signal, and outputs the result value of the comparison. The processor controls the oscillation frequency of the oscillator until the result value satisfies a predetermined reference value.
1. A time synchronizing apparatus for a mobile WiMAX analyzer, comprising:
a Global Positioning System (GPS) receiver for outputting a GPS signal that is synchronized with GPS time using information received from a GPS satellite; and
a synchronization control unit for comparing the GPS signal, which is received from the GPS receiver, and a reference signal, which is generated using an internal clock, and controlling synchronization according to the result of the comparison;
wherein the synchronization control unit comprises:
an oscillator for outputting an oscillation signal having a predetermined frequency, which is used as an internal clock source;
a divider for dividing the oscillation signal, which is output from the oscillator, to generate the reference signal, which has a frequency lower than that of the oscillation signal;
an offset comparison unit for comparing differences between the GPS signal, which is received from the GPS receiver, and the reference signal, which is generated by the divider, and outputting a result value of the comparison; and
a processor for controlling an oscillation frequency of the oscillator until the result value output from the offset comparison unit satisfies a predetermined reference value;
wherein each of the GPS signal and the reference signal is a 1 PPS signal, and when the GPS signal or the reference signal is received, the offset comparison unit starts counting based on the oscillation signal output from the oscillator, latches a count number reached until the GPS signal or the reference signal is received again, and then outputs the count number as the result value.
2. The time synchronizing apparatus as set forth in claim 1 , wherein the offset comparison unit and the processor are implemented using Field Programmable Gate Arrays (FPGAs).
3. The time synchronizing apparatus as set forth in claim 1 , wherein the oscillator is implemented using an Oven-Controlled Crystal Oscillator (OCXO).
4. A time synchronizing apparatus for a mobile WiMAX analyzer, comprising:
a Global Positioning System (GPS) receiver for outputting a GPS signal that is synchronized with GPS time using information received from a GPS satellite;
a synchronization control unit for comparing the GPS signal, which is received from the GPS receiver, and a reference signal, which is generated using an internal clock, and controlling synchronization according to the result of the comparison; and
a Light Emitting Diode (LED) display unit for visually displaying a stabilized state of the synchronization;
wherein the synchronization control unit comprises:
an oscillator for outputting an oscillation signal having a predetermined frequency, which is used as an internal clock source;
a divider for dividing the oscillation signal, which is output from the oscillator, into the reference signal, which has a frequency lower than that of the oscillation signal;
an offset comparison unit for comparing differences between the GPS signal, which is received from the GPS receiver, and the reference signal, which is generated by the divider, and outputting a result value of the comparison; and
a processor for controlling an oscillation frequency of the oscillator until the result value output from the offset comparison unit satisfies a predetermined reference value;
wherein the processor causes the LED to be turned on when the reference value is satisfied; and
wherein each of the GPS signal and the reference signal is a 1 PPS signal, and when the GPS signal or the reference signal is received, the offset comparison unit starts counting based on the oscillation signal output from the oscillator, latches a count number reached until the GPS signal or the reference signal is received again, and then outputs the count number as the result value.
5. The time synchronizing apparatus as set forth in claim 4 , wherein the offset comparison unit and the processor are implemented using Field Programmable Gate Arrays (FPGAs).
6. The time synchronizing apparatus as set forth in claim 4 , wherein the oscillator is implemented using an Oven-Controlled Crystal Oscillator (OCXO).