WO2009052716A1

WO2009052716A1 - Method and mobile terminal for eliminating frequency deviation

Info

Publication number: WO2009052716A1
Application number: PCT/CN2008/072156
Authority: WO
Inventors: Lin XUE
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2007-10-22
Filing date: 2008-08-27
Publication date: 2009-04-30
Also published as: CN101150330A

Abstract

A method for eliminating frequency deviation comprises: a GPS satellite signal is received and time information is obtained; the frequency deviation estimation is performed on a voltage-controlled crystal oscillator of a mobile terminal according to the time information; a bias voltage of the voltage-controlled crystal oscillator of the mobile terminal is adjusted according to the frequency deviation of the voltage-controlled crystal oscillator; the working frequency of the voltage-controlled crystal oscillator is controlled by using the adjusted bias voltage. The mobile terminal is used for implementing the method.

Description

Method for eliminating frequency offset and mobile terminal

Technical field

The present invention relates to the field of communications technologies, and in particular, to a method for eliminating frequency offset and a mobile terminal. Background technique

In WCDMA (Wide-Band Code Division Multiple Access) wireless mobile communication system, the base station on the network side uses a high-stability temperature-compensated crystal oscillator as the working clock source, and its frequency stability usually reaches 0.05. Ppm (part per million, parts per million), and the mobile terminal on the terminal side uses a VCXO (Voltage-Controlled Crystal Oscillator), and its frequency stability is generally only about 5 ppm. This causes the mobile terminal to generate a frequency offset (Frequency Offset) when it receives the downlink signal sent by the base station, which is generally referred to as a frequency offset. In addition to the frequency offset generated in this case, the mobile terminal also generates a Doppler shift in the case of high-speed movement.

The frequency offset of the mobile terminal relative to the base station generally includes two parts: one part is the carrier frequency offset between the down-conversion radio frequency carrier generated by the mobile terminal VCX0 and the downlink carrier sent by the base station; the other part is the sampling clock frequency generated by the mobile terminal VCX0. Partial. For example, for a 2 GHz carrier used in a WCDMA system, the frequency stability of the mobile terminal VCXO lppm will result in a carrier frequency offset of 2 kHz, while the 15.36 MHz sample clock has a 15.36 Hz sampling frequency offset.

The above two partial frequency offsets are generally relatively large when the mobile terminal is powered on, at around 2 kHz. The carrier frequency offset will cause the signal-to-noise ratio of the cell search to deteriorate, and the probability of cell search failure will increase; the frequency offset of the sample will cause the searched radio frame real-band boundary and frame boundary to deviate from the correct position. After completing the initial cell search, the mobile terminal can use the following method to eliminate the frequency offset, that is, by establishing synchronization with the network side, and using the network downlink reference channel for frequency locking, so that the frequency stability of the mobile terminal is controlled within O.lppm.

The effect of frequency offset on cell search is compared when the wireless channel environment is bad. Prominent, because a poor channel environment requires a long time initial cell search to obtain a higher signal to noise ratio, but a long time cell search will increase the phase error of the frequency offset cumulative, but actually make the received letter The noise ratio decreases, and a serious situation can cause the cell search to fail.

In view of this situation, the prior art proposes a method for calibrating the initial bias voltage of the VCXO of each mobile terminal during the manufacturing process of the mobile terminal, and obtaining the VCXO required to generate the nominal frequency at different temperatures. The initial bias voltage value table (referred to as a configuration table) stores the configuration table in the memory of the mobile terminal. After the mobile terminal is turned on, query the configuration table according to the temperature measured at the time of power-on, find the bias voltage for controlling the VCXO, and calibrate the operating frequency of the VCXO.

However, VCXO will continue to age during use, and its frequency stability characteristics will also change. After a long time, the calibration values in the previously saved configuration table are still used.

The bias voltage of the VCXO will cause the actual frequency offset to increase.

The prior art also has a solution to the problem that the phase error accumulated by the frequency offset causes the cell search to fail. In the process of initial cell search after the power is turned on, the mobile terminal uses the PSCH (Primary Synchronous Channel) of WCDMA to estimate the frequency offset of the VCXO, and adjusts the bias voltage of the VCXO according to the frequency offset estimation amount to achieve elimination. The purpose of frequency offset.

However, the disadvantage of this method is that the accuracy of the frequency offset estimation is not high, especially in the case of a relatively harsh wireless channel environment, which is affected by noise and interference, and the accuracy of the frequency offset estimation is more limited, and the frequency offset cannot be effectively eliminated. Summary of the invention

The embodiment of the invention provides a method for eliminating frequency offset and a mobile terminal, so as to eliminate the frequency offset when the mobile terminal is initially powered on, and improve the probability of successful initial cell search.

The embodiment of the present invention is implemented as follows: A method for eliminating frequency offset, comprising: receiving a GPS satellite signal to obtain time information;

Performing frequency offset estimation on the voltage controlled crystal oscillator of the mobile terminal according to the time information; Adjusting a bias voltage of the voltage controlled crystal oscillator of the mobile terminal according to the frequency offset of the voltage controlled crystal oscillator;

The operating frequency of the voltage controlled crystal oscillator is controlled using the adjusted bias voltage. A mobile terminal includes:

a GPS receiving module, configured to receive a GPS satellite signal, and obtain time information; a first frequency offset estimating module, configured to perform frequency offset estimation on the voltage controlled crystal oscillator of the mobile terminal according to the time information;

a bias voltage adjustment module for adjusting a bias voltage of the voltage controlled crystal oscillator of the mobile terminal according to a frequency offset of the voltage controlled crystal oscillator;

A frequency offset calibration module that controls the operating frequency of the voltage controlled crystal oscillator using the adjusted bias voltage.

Compared with the prior art, the embodiment of the present invention eliminates the frequency offset of the mobile terminal at the initial startup by utilizing the GPS (Global Positioning System) signal with high frequency stability, and improves the probability of successful initial cell search. DRAWINGS

1 is a flowchart of a method according to an embodiment of the present invention;

2 is a schematic diagram of an apparatus according to an embodiment of the present invention. detailed description

Embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

The embodiment of the present invention provides a method for eliminating frequency offset. As shown in FIG. 1, the method includes the following steps: Step 101: Receive a GPS satellite signal to obtain timing information. The frequency stability of the satellite can reach O.OOlppm, and the accuracy of the timing information received by the mobile terminal can reach

0.005ppm.

Step 102: Output a timing pulse signal according to the timing information. The timing pulse signal can reach IPPS (One Pulse Per Second), which is a pulse signal with a width of 50 ns per second.

Step 103: Perform frequency offset estimation on the VCXO of the mobile terminal by using the timing pulse signal Count.

The method for performing frequency offset estimation may be: using the timing pulse signal as a count control signal, measuring a number of VCXO output clocks in a statistical period, and obtaining a number of VCXO output clocks measured in the statistical period to obtain a mobile terminal The frequency offset of VCXO.

AF = ^ ± {^ - F )

Specifically, the mobile terminal can be calculated by ^N ^ ^ ^τ

The frequency offset of VCXO. Where 7 is the statistical period, ^ is the number of VCXO output clocks obtained for the first measurement, and w is the number of repeated measurements, ^F ^. For the nominal operating frequency of the VCXO of the mobile terminal, ^ is the frequency offset of the VCXO of the mobile terminal.

Steps 104 and 4 adjust the bias voltage of the VCXO of the mobile terminal according to the frequency offset of the VCXO.

Generally, the bias voltage value Δν of the VCXO and the frequency offset Δ/ are linear: Δν = Α * Δ/. Therefore, the bias voltage adjustment amount Δ _{ν ∞} . = Α * Δ^ _∞ if the initial bias voltage of the VCXO is . , then the adjusted VCXO bias voltage is . ^{+ Δί} ^. .

Step 105: Control the operating frequency of the VCXO by using the adjusted bias voltage to eliminate the frequency offset of the VCXO.

Step 106: Perform frequency offset estimation on the VCXO after the frequency offset calibration by using the timing pulse signal. The method for estimating the frequency offset is the same as the method of step 103, and details are not described herein again.

Step 107, when the frequency offset of the VCXO. When the value is less than the preset frequency offset, the initial cell search is performed; when the VCXO is frequency offset. When it is greater than or equal to the preset frequency offset, perform step 104 until the VCXO frequency offset. Less than the preset frequency offset threshold ^.

The method may further comprise the steps of:

The adjusted bias voltage value is saved, and the adjusted bias voltage value is used as the initial bias voltage of the mobile terminal VCXO. In this way, when the mobile terminal VCXO is powered on for the next time, or after the first frequency offset adjustment is performed by using the above embodiment, the frequency offset of the VCXO is small, and the time for eliminating the frequency offset is shortened.

The embodiment of the invention further provides a mobile terminal, as shown in FIG. 2, comprising: GPS The receiving module 21, the first frequency offset estimating module 22, the bias voltage adjusting module 23, the frequency offset calibration module 24, the second frequency offset estimating module 25, and the determining module 26.

The GPS receiving module 21 is configured to receive a GPS satellite signal and obtain timing information. The frequency stability of the satellite can reach O.OOlppm, and the timing information received by the mobile terminal can reach 0.005ppm.

The first frequency offset estimation module 22 is configured to perform frequency offset estimation on the VCXO of the mobile terminal according to the time information. The first frequency offset estimation module 22 includes: a timing pulse signal module, configured to output a timing pulse signal according to the timing information; and a first frequency offset estimation submodule, configured to use the timing pulse signal to the mobile terminal The voltage controlled crystal oscillator performs frequency offset estimation. The timing pulse signal can reach 1PPS (One Pulse Per Second), which is a pulse signal with a width of 50ns per second.

The first frequency offset estimation sub-module includes: a measurement module, configured to use the timing pulse signal as a count control signal to measure a number of VCXO output clocks in a statistical period; and a frequency offset calculation module, configured to perform statistics according to the The number of VCXO output clocks measured during the period is calculated, and the frequency offset of the VCXO of the mobile terminal is calculated. The frequency offset calculation module may be a first frequency offset calculation module, configured according to a formula

Calculate the frequency offset of the VCXO of the mobile terminal, where 7 is the statistical period, ^M ! is the number of VCXO output clocks obtained by the first measurement, and ^ is the number of repeated measurements, ^F ^. For the nominal operating frequency of the VCXO of the mobile terminal, ^ is the frequency offset of the VCXO of the mobile terminal.

The bias voltage adjustment module 23 is configured to adjust a bias voltage of the VCXO of the mobile terminal according to a frequency offset of the VCXO. The bias voltage adjustment module 23 may be a first bias voltage adjustment module for using a VCXO bias voltage value Δν and a frequency offset Δ/ in a linear relationship: Δν = Α * Δ/ The frequency offset adjusts the bias voltage of the VCXO of the mobile terminal, and the bias voltage adjustment amount is eight^«. ^{= )3⁄4:} *^«. The adjusted VCXO bias voltage is ^v o ^{+ AV} _vcxo , where . The initial bias voltage for the VCXO.

The frequency offset calibration module 24 is configured to control the operating frequency of the VCXO by using the adjusted bias voltage to eliminate the frequency offset of the VCXO.

The second frequency offset estimation module 25 is configured to use the timing pulse signal to frequency offset The calibrated VCXO performs frequency offset estimation. The second frequency offset estimation module 25 and the first frequency offset estimation module 22 may be two independent modules, or may be combined into one module, or two independent parts of one module.

The determining module 26 is configured to determine a frequency offset of the VCXO. Is it less than the preset frequency offset? When the frequency offset of the VCXO is ^«. When less than the preset frequency offset threshold ^, the cell search module 27 is notified to perform an initial cell search; when the frequency offset of the VCXO is greater than or equal to a preset frequency offset threshold ^, the bias voltage adjustment module 23 is notified according to the bias voltage adjustment module 23 The calibrated frequency offset adjusts the bias voltage of the mobile terminal VCXO, and the frequency offset calibration module 24 recalibrates the frequency offset of the VCXO until the frequency offset of the VCXO is ^«. Less than the preset frequency offset value ^.

The mobile terminal may further include: a cell search module 27, configured to perform an initial cell search when the frequency offset of the VCXO is less than a preset frequency offset threshold.

The mobile terminal may further include: a setting module, configured to save the adjusted bias voltage value, and use the adjusted bias voltage value as an initial bias voltage of the mobile terminal VCXO. In this way, when the mobile terminal VCXO is powered on for the next time, or after the first frequency offset adjustment using the above embodiment, the frequency offset of the VCXO is small, and the time for eliminating the frequency offset is shortened.

The embodiments of the present invention can be applied to mobile terminals of WCDMA systems and other 2G or 3G systems.

In the embodiment of the present invention, the frequency offset of the mobile terminal at the initial startup is eliminated by using the GPS signal with high frequency stability, and the probability of successful initial cell search is improved.

Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by hardware or by software plus a necessary general hardware platform. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), including several The instructions are for causing a computer device (which may be a personal computer, server, or network device, etc.) to perform the methods described in various embodiments of the present invention.

In summary, the above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention. The scope of protection of the invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

Rights request

A method for eliminating frequency offset, characterized in that it comprises:

Receiving GPS satellite signals to obtain time information;

Performing a frequency offset estimation on the voltage controlled crystal oscillator of the mobile terminal according to the time information;

Adjusting a bias voltage of the voltage controlled crystal oscillator of the mobile terminal according to the frequency offset of the voltage controlled crystal oscillator;

The operating frequency of the voltage controlled crystal oscillator is controlled using the adjusted bias voltage.

2. The method according to claim 1, further comprising: performing frequency offset estimation on the frequency offset crystal oscillator after the frequency offset calibration using the timing pulse signal;

When the frequency offset of the voltage controlled crystal oscillator is greater than or equal to a preset frequency offset, the step of adjusting the bias voltage of the voltage controlled crystal oscillator of the mobile terminal according to the frequency offset of the voltage controlled crystal oscillator is performed until The frequency offset of the voltage controlled crystal oscillator is less than a preset frequency offset threshold.

3. The method according to claim 2, further comprising: when the frequency offset of the VCXO is ^«. When the value is smaller than the preset frequency offset, the initial cell search is performed.

The method according to claim 1, wherein the step of performing frequency offset estimation on the voltage controlled crystal oscillator of the mobile terminal according to the time information comprises:

Outputting a timing pulse signal according to the time information;

A frequency offset estimation of the voltage controlled crystal oscillator of the mobile terminal is performed using the timing pulse signal.

The method according to claim 4, wherein the step of estimating the frequency offset of the voltage controlled crystal oscillator of the mobile terminal by using the timing pulse signal comprises: measuring the timing pulse signal as a count control signal The number of output clocks of the voltage controlled crystal oscillator in the statistical period, and the frequency of the voltage controlled crystal oscillator of the mobile terminal is obtained according to the number of output clocks of the voltage controlled crystal oscillator measured in the statistical period Partial.

The method according to claim 5, wherein the step of obtaining a frequency offset of the voltage controlled crystal oscillator of the mobile terminal according to the number of output clocks of the voltage controlled crystal oscillator measured in the statistical period comprises: by

The frequency offset of the voltage controlled crystal oscillator of the mobile terminal; wherein, 7 is the statistical period, ^Μ ! is the number of output clocks of the voltage controlled crystal oscillator obtained by the ^7th measurement, ^ is the number of repeated measurements, ^F ^. For the nominal operating frequency of the voltage controlled crystal oscillator of the mobile terminal, ^ is the frequency offset of the voltage controlled crystal oscillator of the mobile terminal.

7. The method according to claim 1, wherein the step of adjusting a bias voltage of the voltage controlled crystal oscillator of the mobile terminal according to a frequency offset of the voltage controlled crystal oscillator comprises:

When the bias voltage value Δν of the voltage controlled crystal oscillator and the frequency offset Δ/ are linear: = ^ Δ/, the bias voltage of the voltage controlled crystal oscillator of the mobile terminal is adjusted according to the frequency offset of the voltage controlled crystal oscillator , the bias voltage adjustment amount is eight ^«. ⁼ ^*^«. The bias voltage of the adjusted voltage controlled crystal oscillator is . ^{+ Δί} ^. , among them, . It is the initial bias voltage of the voltage controlled crystal oscillator.

8. The method according to claim 1, further comprising: saving the adjusted bias voltage value, and using the adjusted bias voltage value as an initial bias voltage of the mobile terminal VCXO.

9. A mobile terminal, comprising:

Global Positioning System (GPS) GPS receiving module for receiving GPS satellite signals and obtaining time information;

a first frequency offset estimation module, configured to perform frequency offset estimation on the voltage controlled crystal oscillator of the mobile terminal according to the time information; a bias voltage adjustment module, configured to adjust a bias voltage of the voltage controlled crystal oscillator of the mobile terminal according to a frequency offset of the voltage controlled crystal oscillator;

The mobile terminal according to claim 9, wherein the mobile terminal further comprises:

a second frequency offset estimation module, configured to perform frequency offset estimation on the voltage-controlled crystal oscillator after frequency offset calibration using the timing pulse signal;

The judging module is configured to determine whether the frequency offset of the voltage controlled crystal oscillator is d, and is at a preset frequency offset threshold ^, when the frequency offset of the voltage controlled crystal oscillator is greater than or equal to a preset frequency offset threshold, the notification The bias voltage adjustment module adjusts a bias voltage of the voltage controlled crystal oscillator of the mobile terminal according to the calibrated frequency offset, and the frequency offset calibration module recalibrates the frequency offset of the voltage controlled crystal oscillator until the frequency of the voltage controlled crystal oscillator The deviation d is at a preset frequency offset.

The mobile terminal according to claim 10, wherein the mobile terminal further comprises:

The cell search module is configured to perform initial cell search when the frequency offset of the voltage controlled crystal oscillator is less than a preset frequency offset.

The mobile terminal according to claim 9, wherein the first frequency offset estimation module comprises:

And a timing pulse signal module, configured to output a timing pulse signal according to the timing information; and a first frequency offset estimation submodule, configured to perform frequency offset estimation on the voltage controlled crystal oscillator of the mobile terminal by using the timing pulse signal.

The mobile terminal according to claim 12, wherein the first frequency offset estimation submodule comprises:

a measuring module, configured to use the timing pulse signal as a counting control signal to measure a number of output clocks of the voltage controlled crystal oscillator in a statistical period;

And a frequency offset calculation module, configured to calculate a frequency offset of the voltage controlled crystal oscillator of the mobile terminal according to the number of output clocks of the voltage controlled crystal oscillator measured in the statistical period.

The mobile terminal according to claim 13, wherein the frequency offset

AF = ^∑{^ - F ) The calculation module is the first frequency offset calculation module, which is used to calculate the frequency offset of the voltage controlled crystal oscillator of the mobile terminal according to ^N ^ ^ ^T J, where 7 is the statistical period, ^Μ ι The number of output clocks of the voltage controlled crystal oscillator obtained for the ^7th measurement, ^ is the number of repeated measurements, ^F ^. The nominal operating frequency of the voltage controlled crystal oscillator for mobile terminals, ^«. The frequency offset of the voltage controlled crystal oscillator for the mobile terminal.

The mobile terminal according to claim 9, wherein the bias voltage adjustment module is a first bias voltage adjustment module for bias voltage value Δν and frequency offset of the voltage controlled crystal oscillator Δ/linear relationship: Δν = Α * Δ/, adjust the bias voltage of the voltage controlled crystal oscillator of the mobile terminal according to the frequency offset of the voltage controlled crystal oscillator, and the bias voltage adjustment amount Δ = Δ^ _∞ The voltage controlled crystal oscillator bias voltage is . + Δ , where, . It is the initial bias voltage of the voltage controlled crystal oscillator.

The mobile terminal according to claim 9, wherein the mobile terminal further comprises: a setting module, configured to save the adjusted offset voltage value, and use the adjusted offset voltage value as a mobile terminal pressure Control the initial bias voltage of the crystal oscillator.

The mobile terminal according to claim 10, wherein the second frequency offset estimation module and the first frequency offset estimation module are two independent modules, or one module, or one module. Two separate parts.