CN201060266Y

CN201060266Y - Real time clock circuit for accelerating GPS signal capture

Info

Publication number: CN201060266Y
Application number: CNU2007200322072U
Authority: CN
Inventors: 王江安; 张会锁; 周文益
Original assignee: XIAN HUAXUN MICROELECTRONIC CO Ltd
Current assignee: XIAN HUAXUN MICROELECTRONIC CO Ltd
Priority date: 2007-07-06
Filing date: 2007-07-06
Publication date: 2008-05-14
Anticipated expiration: 2017-07-06

Abstract

The utility model discloses a high-precision real-time clock circuit for speeding GPS signal location. The clock circuit comprises the following modules: a low-power oscillator generating cyclic clock pulses under a set rate; an N-bit counter responding to the low-power oscillator and generating one pulse signal per second; an M-bit counter responding to the pulse signal generated per second and generating a definite clock count; a rapid storage for preventing data loss in shutdown of a GPS receiver; and a backup power supply for maintaining the normal operation of each module. The utility model is characterized in that the clock circuit also comprises a trigger; one input interface of the trigger is connected with the connecting line of the receiver time base of the GPS receiver to a navigation tracking processor, and the other input interface is connected with the N-bit counter; the output interface of the trigger is connected with a navigation tracking processor 3; the trigger is used for reading data of the N-bit counter at every millisecond.

Description

Quicken the real time clock circuit that gps signal is caught

Technical field

The utility model relates to the real time clock circuit of a kind of GPS (GPS) receiver.Be a kind of a kind of real time clock circuit that quickens the gps signal location specifically.

Background technology

The GPS accurate in locating needs local receiver to have accurate real-time time.We will obtain the relevant satellite position accurately of pseudo range measurement, and the signal transmission time between needs acquisition GPS receiver and each satellite is determined the measured value of pseudorange.The clock time of GPS information is the absolute time signal of precise synchronization on satellite.Most important in the receiver performance index is exactly positioning time, and in the field of many keys, be vital positioning time.Length positioning time of receiver is by the design decision of receiver itself, and is the key factor that the user selects the GPS receiver to consider.

Existing GPS receiver usually uses the real time clock circuit that has only 1 second resolution, and can't with gps receiver internal timebase precise synchronization.In case thereby device power, this GPS receiver is forced to directly regain the time from satellite-signal.And the shortest GPS receiver generally also wants 10-15 just can finish first locating information second after powering on positioning time on the market.

Summary of the invention

The purpose of this utility model provides a kind of high precision real time clock circuit that quickens the gps signal location.

The utility model takes following technical scheme to be achieved: a kind ofly quicken the real time clock circuit that gps signal is caught, comprise following module:

A low-power oscillator that under set rate, generates the cycle clock pulse;

A N-bit counter responds to above-mentioned low-power oscillator, and per second generates a pulse signal;

A M-bit counter, the pulse signal that above-mentioned per second is generated responds, and generates a clear and definite clock count;

A short-access storage prevents loss of data when being used for the shutdown of GPS receiver;

A standby power supply is used to keep the normal operation of above-mentioned each module;

It is characterized in that, also comprise a trigger, base was to the line of the tracking processor that navigates when input interface of this trigger connected the receiver of GPS receiver; Another input interface connects the N-bit counter; Output interface connects navigation tracking processor 3; This trigger is used for every millisecond of data to the N-bit counter and reads.

In such scheme, can comprise that also is arranged on the other temperature sensor of low-power consumption oscillator, this temperature sensor is connected to the navigation tracking processor of GPS receiver; Described short-access storage is a nonvolatile memory.

The utility model can obtain the position of satellite and time during exact value at receiver, and the GPS receiver transmits a timing reference signal for improved real time clock circuit.In case synchronously down, this value can have individual slight influence to the precise time value aspect site error in receiver; When measuring, collects on satellite accurate gps time once more again up to receiver.Therefore this absolute time just during the receiver of GPS receiver in the base unknown clock jitter after powering on, can become a precise time parameter, and before position calculation begins, avoid from the satellite broadcasting data, obtaining precise time, therefore shortened positioning time.The utility model utilizes improved real time clock circuit to make to shorten to positioning time in 1 second under the situation that receiver has started.

Description of drawings

Fig. 1 has shown the design frame chart of GPS receiver, the real time clock circuit of outstanding existing receiver.

Fig. 2 has shown the improved real time clock circuit structured flowchart of the utility model.

Embodiment

As shown in Figure 1, the real time clock circuit of existing GPS receiver comprises low-power (0.5mW) oscillator that operates in relative low frequency (32.768kHz) 5,9,2 counters 6 that produce 1 second counting of short-access storage, 7, one independently standby power supply 8 normal operations of being used for keeping each module of real time clock circuit.

Peripheral GPS receiver comprises a radio frequency processing module 1, and radiofrequency signal is become baseband signal; A digital signal processing block 2 is used for that digital signal is carried out high speed signal and handles, and for example synchronous and CDMA signal despreading is estimated and removal signal Doppler or carrier phase etc.; A navigation tracking processor 3 carries out relevant control, and navigation tracking processor 3 is also with obtaining and tracing function in the Digital Signal Processing Control Software.

After obtaining the gps satellite position, the time deviation of base 4 when receiver is inferred receiver with the precise time of decoding of satellite, after obtaining position signalling, precise time also can calculate in navigation tracking processor 3 as a result of calculation of navigation.The main difficulty of existing minimizing positioning time is a predicted time accurately.If there is precise time can avoid collecting the process of satellite broadcasting data, also can predictive coding phase place to a sufficiently high precision significantly reduce whole encoding phases search volume.

Generally speaking, common GPS receiver need be carried out following step and just can position.

As shown in table 1, the T.T. of carrying out these steps is 23 to 43 seconds (almanac information that does not have storage) and 5 to 13 seconds (almanac information of having stored is arranged).

As shown in Figure 2, the real time clock circuit of the utility model GPS receiver is to increase a trigger 11 and a temperature sensor 10 that is arranged on the low-power consumption oscillator 5 on the basis of Fig. 1 real time clock circuit, base 4 was to the line of navigation tracking processor 3 when input interface of trigger 11 connected the receiver of GPS receiver, another input interface connects N-bit counter 6, and the output interface of trigger 11 connects navigation tracking processor 3; This trigger is used for every millisecond of data to N-bit counter 6 and reads.Temperature sensor 10 can be arranged on the next door of low-power consumption oscillator 5, and its output connects the navigation tracking processor 3 of GPS receiver, and temperature sensor 10 is used for low-power consumption oscillator 5 is calibrated.

Every millisecond trigger 11 interface read N output bit from N-bit counter 6, the clock signal of trigger 11 interfaces during by receiver base 4 produce, therefore read counting at the every 1KHz edge that improves real-time clock.Since every 1KHz also can represent the receiver measurement epoch in the edge, promptly can be with coming acquisition time from real-time clock with the data that test epoch, corresponding inner 1KHz interrupted reading N-bit counter 6M-bit counter 7, this step can realize by the certain software of navigation tracking processor 3 operations.Fig. 2 shows that temporal resolution can reach 1/32 millisecond.In common receiver, can only reach 1 second temporal resolution and also can not be with receiver the time base 4 synchronous.

In the utility model, when receiver can obtain the position of satellite and time coordinate, transmit a precise time reference signal to real time clock circuit from the GPS receiver.Real time clock circuit can every millisecond reads N output bit by trigger 11 from N-bit counter 6, so just can allow the resolving accuracy of real time clock circuit maintain on 1/32 millisecond.When system power supply was closed, real-time clock carried out work by standby power supply 8, by the stable output of low-power oscillator 5, can keep real-time time equally on an accurate grade.Accurately last given value of gps time and corresponding real-time clock count value are stored in the non-volatile short-access storage 9.When re-powering, short-access storage 9 returns the count value transmission of this time and real time clock circuit to navigation tracking processor 3, just can calculate precise time at that time.And read the N-bit counter by trigger 11 every 1KHz edges and continue to keep this precise time.Thereby when GPS precise time reference signal is invalid, can provide a more accurate time reference.In case this more accurate time is decided in receiver, the error that this value is measured the position mistake is very little, until receiver can receive precise time once more once more from gps satellite signal.Therefore, the time the during receiver of GPS receiver in the base 4 can obtain after powering on accurately, has also just avoided position calculation to obtain precise time before beginning from the satellite broadcasting data, has therefore shortened positioning time.

Improved real time clock circuit can shorten acquisition time greatly, because it can keep this precise time during closing primary power; Or when gps signal is invalid, directly obtain the spread spectrum signal by forced coding phase search algorithm, this encoding phase is (based on current precise time, satellite known location, the estimated value of the position after slave unit cuts off) in the encoding phase scope that may exist.As long as this has fully reduced search time, promptly the sub-fraction of whole encoding phases search volume.This also allows to remove bit synchronous and message synchronization process, just needs to obtain from satellite the data decode step of current time.By the utility model, can make at receiver behind the electrical source consumption of short-term to shorten to positioning time about 1 second.Position obtaining step and the corresponding time of finishing these steps, as shown in table 2:

From table 1 and table 2 more as can be seen, the time altogether of carrying out these steps the 5-13 from table 1 shorten to very significantly second and to have only 1.3 seconds (comprising the almanac data of having stored).This is because the time of having removed several steps and having reduced other steps.The orbital prediction step has been removed, because the supposition receiver is a most recently used, thereby not too influences the selection of satellite.Time after using the last time can measure by real-time clock, and can be used for judging the homogeneity of visibility.Predict Doppler among the Doppler who measures before before, current time and previous satellite broadcasting almanac data are stored in the nonvolatile memory, and back fast prediction satellite visibility and Doppler power on.

The code synchronism step is greatly diminished, and the present encoding phase place that base 4 is relevant since with the receiver of receiver the time can be with the encoding phase of measurement recently, Measurement Phase speed, and the time of these measurements and the current time of representing with the improvement real-time clock estimate.When powered-down, preserve these parameters in nonvolatile memory.

Bit synchronization and message synchronization step can be removed under most of condition, as time of position transmission can before anteposition synchronous regime data in prediction come out.It should be noted that, data bit, bit synchronization and code phase are synchronous, therefore, knew code phase before the power supply off period, bit synchronization and frame synchronization position are in the later accurately predictive code phase place of power supply off period, also can be after the power supply off period prediction bits synchronously and frame synchronization state, therefore get rid of necessity of search.If code phase can be estimated that the transmission location of data bit also can be predicted so, it is synchronous just to there is no need search bit.

Use the temperature sensor 10 of navigation tracking processor 3 readabilities, the low-power consumption oscillator 5 that changes with temperature is calibrated.Calibrating principle is when system power supply is opened, at first measure oscillator temperature at that time by temperature sensor 10, then can be by the oscillation frequency deviation of the prior low-power consumption oscillator of storing 5 and the corresponding look-up table of temperature, find out the oscillation frequency deviation of this moment, the count value in the short-access storage 9 is carried out corresponding modification.When system power supply is closed, at first measure oscillator temperature at that time at short-access storage 9 by temperature sensor 10, temperature when powering on once more with system power supply then averages, medial temperature when obtaining system power supply and closing, the count value of storage is revised when with this temperature system power supply being closed.Temperature sensor 10 has been revised the temperature variant error of output frequency of low-power consumption oscillator 5, and it is more accurate to make that this real time clock circuit can keep the time.

By above-mentioned two improved technical schemes of the present utility model, real time clock circuit is kept and is predicted that the ability of correct time has improved, and the uncertainty of absolute time also greatly reduces.

Claims

1. one kind is quickened the real time clock circuit that gps signal is caught, and comprises following module:

A low-power oscillator that under set rate, generates the cycle clock pulse;

It is characterized in that, also comprise a trigger, base was to the line of the tracking processor that navigates when input interface of this trigger connected the receiver of GPS receiver, another input interface connects the N-bit counter, output interface connects navigation tracking processor 3, and this trigger is used for every millisecond of data to the N-bit counter and reads.

2. the real time clock circuit that acceleration gps signal according to claim 1 is caught is characterized in that, also comprises a temperature sensor that is arranged on by the low-power consumption oscillator, connects the navigation tracking processor of GPS receiver.

3. the real time clock circuit that acceleration gps signal according to claim 1 and 2 is caught is characterized in that, described short-access storage is a nonvolatile memory.