Embodiment
In order to use purpose of the present invention, technical scheme and advantage more clear, below with reference to accompanying drawing, the present invention is described in more detail:
With reference to Fig. 1, this figure is a system block diagram of the present invention, and comprising AD conversion chip, finite impulse response FIR low pass filter, power detection module and CPU, wherein CPU is used for the default and power detection control of frequency.
Referring to figs. 2 and 3, the specific implementation process is: the first step, and behind the GSM digital remote system opening of device, the working frequency points tabulation (being called tabulation 1) before at first recovering to restart from memory as equipment initialization frequency, and is opened the relevant work channel;
Second step, in the current working frequency tabulation all frequency priority be set to the highest, suppose current working frequency for 5,10,15,20,25,30,35,40,45,50,55,60,65}, 13 frequencies altogether, its priority is for the highest, and coefficient is 10;
The 3rd step, utilize idle channel that all GSM working frequency points are carried out power scan, promptly change the centre frequency of idle channel, concrete scanning process is as follows:
The method that described FPGA detects frequency comprises the steps:
The a certain idle channel of CPU configuration mould/number conversion chip is a test channel;
CPU presets mould/pairing frequency of number conversion chip testing passage;
Carry out mixing and filtering with the test channel frequency preset again after the GSM to be measured that mould/number conversion chip will be imported is signal digitalized, obtain down-conversion signal; If the GSM signal frequency of input is identical with the test channel frequency preset, then test channel is output as baseband signal (being digitized carrier signal), otherwise is adjacent signal frequently;
With the data of test channel output through a low pass filter, the adjacent signal frequently of filtering;
CPU notice on-site programmable gate array FPGA (being the power detection module among Fig. 1) beginning frequency measuring ability;
After on-site programmable gate array FPGA detects the frequency measuring ability and enables, beginning power of data behind the statistical filtering in about 2 reframing time length, if detect number of times greater than a certain threshold value n more than or equal to m time in this time period, then this time detected value is adding up of m detection power; If detect number of times greater than a certain threshold value n in the period less than m time at this section, then this time detected value is 0;
On-site programmable gate array FPGA reports the equivalent power detected value of this predeterminated frequency correspondence;
Under the control of CPU, FPGA repeats above-mentioned steps, finishes until all frequency point scannings;
Obtain the performance number of each frequency correspondence that FPGA reports, finish the frequency point scanning measuring ability.
The 4th step, finish scanning after, known the equivalent power value of all frequencies.Find out wherein power maximum, and be worth as benchmark with this remaining frequency is carried out power screening, power is thought to be effective frequency greater than the Frequency point of 0.1 times of maximum, joins new search frequency tabulation (being called tabulation 2).Suppose scanning result such as following table:
According to above description content, then the power maximum is No. 5 frequencies in this example, and its performance number is 10000, and according to the power screening conditions, all new search frequencies are all effective in the table.
The 5th step, according to GSM frequency planning principles, in same sub-district, can not use two adjacent frequencies simultaneously, adjacent frequency is screened to tabulating in 2, such as No. 5 and No. 6 frequencies, after equivalent performance number compared, keep wherein No. 5 bigger frequencies of equivalent power value, No. 6 less frequencies of deletion equivalent power value, by that analogy.Then can delete No. 6 and No. 16 frequencies, it is as follows upgrading tabulation 2:
In the 6th step, will tabulate 21 comprehensively compares with tabulation, tabulates promptly with current new search that table 2 be that limit priority is other, and the deletion adjacent frequency of the frequency with in the table 2 in 1 of tabulating removes frequency No. 25, and then the tabulation 1 after the renewal is as follows:
The 7th step, to adjust according to up-to-date Search Results his-and-hers watches 1 intermediate-frequeney point priority, the adjustment principle is: whenever finish once search, the frequency priority that is present in the table 1 that searches increases by 1, and limit priority is 10, otherwise priority reduces 1, and minimum is 0.If the frequency that new search arrives be increased in the tabulation 1, and priority is for the highest.Then be to the 1 renewal back result that tabulates:
The 8th step, if frequency points surpasses the maximum functional number of channel of GSM radio frequency stretch system, then delete corresponding frequency from low to high according to priority level, then, should delete frequency No. 30 according to tabulation 1 situation.Then be to the 1 renewal back result that tabulates:
The 9th step was set to the tabulation of the frequency after upgrading in the far-drawing system base station end device, thereby and was broadcast to all far-ends by the system communication link and realizes automatic frequency search.Circulate by above step.