Filter loop structure for synchronization in a mobile communication terminal and a method of using the same
View Patent ↗Filtering loop and method for maintaining synchronization between a receiver and a transmitter reduces overhead and enables more robust operation. The method includes the step of receiving an error signal corresponding to a synchronization parameter. A first order filter is applied to the error signal such that a residual signal results. The method further provides for compensating the residual signal for drift such that the compensated residual signal estimates a rate of change in the residual signal. By compensating the residual signal for drift, difficulties associated with time lag and signal degradation are obviated.
1. A method for maintaining synchronization between a receiver and a transmitter, the method comprising the steps of:
receiving an error signal corresponding to a synchronization parameter; applying a first order filter to the error signal such that a residual signal results;
compensating the residual signal for drift such that the compensated residual signal estimates a rate of change in the residual signal and enables synchronization between the receiver and the transmitter;
applying a second order filter to the residual signal such that a correction signal results;
forcing the correction signal beyond a predetermined quantization threshold;
modeling a quantizer of the receiver;
applying the quantizer model to the correction signal such that a quantizer adjustment signal results; and
adding the quantizer adjustment signal to the correction signal.
2. The method of claim 1 further including the step of repeating the applying and adding steps until the correction signal exceeds the predetermined quantizer threshold.
3. A method for maintaining synchronization between a receiver and a transmitter, the method comprising the steps of:
receiving an error signal corresponding to a synchronization parameter;
applying a first order filter to the error signal such that a residual signal results;
compensating the residual signal for drift such that the compensated residual signal estimates a rate of change in the residual signal and enables synchronization between the receiver and the transmitter;
applying a second order filter to the residual signal such that a correction signal results;
forcing the correction signal beyond predetermined quantization threshold;
selecting a response time of the second order filter in accordance with a desired filter response; and
adjusting the response time on a channel-by-channel basis such that each receiver channel has a corresponding response setting.
4. The method of claim 3 further including the step of referencing the response settings to a fastest burst spacing of the channels.
5. A method for compensating a residual signal for drift, the method comprising the steps of:
applying a second order filter to the residual signal such that a correction signal results;
forcing the correction signal beyond a predetermined quantization threshold;
modeling a quantizer of a receiver;
applying the quantizer model to the correction signal such that a quantizer
adjustment signal results; and adding the quantizer adjustment signal to the correction signal.
6. The method of claim 5 further including the step of repeating the applying and adding steps until the correction signal exceeds the predetermined quantizer threshold.
7. A method for compensating a residual signal for drift, the method comprising the steps of:
applying a second order filter to the residual signal such that a correction signal results;
forcing the correction signal beyond a predetermined quantization threshold;
selecting a response time of the second order filter in accordance with a desired filter response; and
adjusting the response time on a channel-by-channel basis such that each receiver channel has a corresponding response setting.
8. The method of claim 7 further including the step of referencing the response settings to a fastest burst spacing of the channels.
9. A method for maintaining synchronization between a mobile receiver and a transmitter, the method comprising the steps of:
receiving an error signal from a demodulator of the receiver, the error signal corresponding to a synchronization parameter;
applying a first order filter to the error signal such that a residual signal results;
selecting a response time of a second order filter in accordance with a desired filter response;
applying the second order filter to the error signal such that a correction signal results;
forcing the correction signal beyond a predetermined quantization threshold such that a compensated residual signal results, the compensated residual signal estimating a rate of change in the residual signal;
modeling a quantizer of the receiver;
applying the quantizer model to the correction signal such that a quantizer adjustment signal results; and
adding the quantizer adjustment signal to the correction signal.
10. An error signal filtering loop comprising:
a first order filter for smoothing the error signal such that a residual signal results, the error signal corresponding to a synchronization parameter;
an integrator for integrating a normalized signal such that a final adjustment signal results, the final adjustments signal enabling a hardware quantizer of a receiver to maintain synchronization between a transmitter and the receiver; and
a drift compensation module for generating the normalized signal based on the residual signal such that the normalized signal estimates a rate of change in the residual signal; and
wherein the drift compensation module includes:
a drift estimator for applying a second order filter to the residual signal such that a correction signal results; and
a quantizer compensator operatively coupled to the drift estimator, the quantizer compensator forcing the correction signal beyond a predetermined quantization threshold.