CN102098470B - Table lookup optimization method and numerical controlled oscillator - Google Patents
Table lookup optimization method and numerical controlled oscillator Download PDFInfo
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Abstract
The invention aims to provide a table lookup optimization method, which comprises the following steps of: a, representing numerical controlled oscillator (NCO) forms corresponding to different television audio carrier frequencies by using a reference form; b, shortening and optimizing the reference form to a 1/4 length, and obtaining other non-reference forms from the reference form; and c, further optimizing and storing the reference form according to sine regularities to obtain a sine value and a cosine value by once addressing. The invention also provides a numerical controlled oscillator utilizing the table lookup optimization method, which comprises a form unit, a counting unit, an addressing unit, a splitting unit and a multiplication unit, wherein the form unit is set in a read-only memory (ROM), and stores NCO form data optimized by the table lookup optimization method; the counting unit counts the input television audio carrier frequencies, and takes a count as an index value; the addressing unit addresses the form unit to obtain required NCO form data; the splitting unit splits the required NCO form data into the sine value and the cosine value; and the multiplication unit receives the sine value and the cosine value, and multiplies the sine value and the cosine value by the input television audio carrier frequencies respectively.
Description
Technical field
The present invention relates to digital controlled oscillator, be specifically related to a kind of method of optimizing and numerically-controlled oscillator that utilizes this table lookup optimization method of tabling look-up.
Background technology
Audio signal in that simulated television tuner receiving terminal receives comprises FM, and the audio signal of the standards such as NICAM needs just can finish last digital decoding through after the demodulation.In order to satisfy the digital decoding of back, NCO (Numerical controlled oscillator, numerically-controlled oscillator) can be used to satisfy the demodulation of unlike signal.Multiplication between NCO executive signal and the plural sine is realized a kind of function that converts another frequency to of frequency.The sample of sinusoidal numerical value is stored in the look-up table, and look-up table is stored in the memory, for example is stored in traditional RAM (among random access memory () or the ROM (read-only memory).At present, the implementation of NCO usually adopts the mode of progressively approaching, and calculates the value near the sound carrier frequency, as the carrier frequency of demodulation.But because the accuracy that this method realizes is relevant with the degree of approaching, in order to improve precision, need to increase memory space and the hardware spending of NCO form.In addition, the also general NCO form made of the minimum step value of with good grounds signal although this NCO form versatility is very high, is applied in the chip of real-time decoding for needs, and it is low that efficient seemed again, can't satisfy the application of reality.
Shortcoming for said method, in order to obtain the exact value of corresponding carrier frequency, also have the NCO module is set a specific NCO form according to the specific carrier frequency of acknowledge(ment) signal, corresponding one by one with carrier frequency, although this method demodulating process is quick, cost is not high, and limitation is very large, in case carrier frequency changes, this NCO form has just cancelled.Simulated television audio frequency commonly used under the different systems exists 9 kinds of different carrier frequencies, if adopt a cover NCO form of every kind of standard correspondence oneself when designing, the list data amount that store will be very large, cause the high cost of decoding chip.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of table lookup optimization method and numerically-controlled oscillator.For particular range sound carrier frequency, this table lookup optimization method has been optimized form to greatest extent in TV analogue audio frequency demodulation field, and the numerically-controlled oscillator that utilizes table lookup optimization method not only improves the versatility of sound carrier frequency demodulation algorithm, accelerate addressing speed, reduce memory space, and reduce chip cost.
For solving the problems of the technologies described above, a kind of table lookup optimization method that utilizes that the object of the invention provides is used for numerically-controlled oscillator, and described table lookup optimization method may further comprise the steps: a. represents the NCO form that different TV audio carrier frequencies are corresponding with the benchmark form; B. described benchmark form is dwindled being optimized to 1/4th length, other non-benchmark forms are obtained from described benchmark form; C. according to sinusoidal regular, described benchmark form is further optimized storage, so that an addressing just obtains sine value and cosine value.
Further, describedly represent the method for the NCO form that different TV audio carrier frequencies are corresponding with the benchmark form, may further comprise the steps: a1. calculates the corresponding form length of different TV audio carrier frequencies, the tabulation of tabulation length; A2. the corresponding form of form length of choosing the numerical value maximum from the tabulation of described form length is as the benchmark form, according to formula:
sin[(2nf
c(b)π)/f
s]＝sin[2(N+f
c(a))π/f
s]＝sin[(2f
c(a)π)/f
s]
Wherein, f
c(b) be TV audio carrier frequency corresponding to benchmark form, f
c(a) be need to addressing in the benchmark form other TV audio carrier frequencies, n and N are integer, n=0,1,2 ...,
Getting TV audio carrier frequency corresponding to described benchmark form is f
c(b), the f in the described formula of described other TV audio carrier frequency substitutions
c(a) n when the right-hand N of described formula integer occurs for the first time, represents f since 0 value this moment
c(a) NCO form can pass through f
c(b) corresponding benchmark form represents.When the form length of described numerical value maximum has two when above, choose one of them corresponding form as the benchmark form.When the form of described other TV audio carrier frequencies can not represent with a benchmark form, in the scope of described other TV audio carrier frequencies, the form of all described other TV audio carrier frequencies represents that with the benchmark form method of the NCO form that different TV audio carrier frequencies are corresponding finds out another benchmark form again according to described, until can find corresponding benchmark form to represent.
Further, described regular according to sine, described benchmark form is further optimized storage, so that an addressing just obtains the method for sine value and cosine value, may further comprise the steps:
C1. the benchmark form length of getting after the optimization is w, and the described input index value of sin and cos value is corresponded to index in the form after the optimization, and rule is:
Input index (0-(w-1)-1), sin value index=input index,
Cos value index=(w-1)-input index;
Input index (w-1-2 (w-1)-1), sin value index=2 (w-1)-input index,
Cos value index=input index-(w-1);
Input index (2 (w-1)-3 (w-1)-1), sin value index=input index-2 (w-1),
Cos value index=3 (w-1)-input index;
Input index (3 (w-1)-4 (w-1)-1), sin value index=4 (w-1)-input index,
Cos value index=input index-3 (w-1);
C2. according to the rule of form stores, the address realm of the form after the optimization is (0-(w-1)/2), and the index value that obtains according to c1 carries out addressing to form, and rule is:
Sin value index (0-(w-1)/2): must be worth with sin value indexed addressing, upper byte is the sin tabular value, and low byte is got the negative cos value that is;
Cos value index (0-(w-1)/2): must be worth with cos value indexed addressing, upper byte is the cos tabular value, and low byte is the sin value;
C3. the reset sin obtain and the sign bit of cos value, rule is:
Input index (0-(W-1)-1): sin value=sin value; The cos value=-the cos value;
Input index (w-1-2 (w-1)-1): sin value=sin value; Cos value=cos value;
Input index (2 (w-1)-3 (w-1)-1): the sin value=-s in value; Cos value=cos value;
Input index (3 (w-1)-4 (w-1)-1): the sin value=-the sin value; The cos value=-the cos value.
Described different TV audio carrier frequency comprises 9 kinds of different carrier frequencies, is respectively 5.742MHz, 6.5MHz, 6.258MHz, 4.5MHz, 4.724MHz, 5.85MHz, 6.552MHz and 6.0MHz.
Another object of the present invention provides a kind of numerically-controlled oscillator that utilizes above-mentioned table lookup optimization method, comprising: list cell, be arranged among the ROM, and store the NCO list data after described table lookup optimization method is optimized; Counting unit receives input TV audio carrier frequency, and to the counting of described input TV audio carrier frequency, as index value; Selected cell, described selected cell carries out addressing according to described input sound carrier frequency and described index value to described list cell, obtains required NCO list data; Split cells receives described required NCO list data, and described required NCO list data is split as sine value and cosine value; Multiplication unit receives described sine value and described cosine value, and carries out multiplying with input TV audio carrier frequency respectively, obtains respectively the first quadrature component value and the second quadrature component value.
It is that benchmark form corresponding to 5.5MHz and TV audio carrier frequency are benchmark form corresponding to 6.258MHz that described NCO list data is preserved the TV audio carrier frequency.Described NCO list data can represent 9 kinds of different corresponding forms of TV audio carrier frequency, and described 9 kinds of different TV audio carrier frequencies are respectively 5.742MHz, 6.5MHz, 6.258MHz, 4.5MHz, 4.724MHz, 5.85MHz, 6.552MHz and 6.0MHz.
A kind of table lookup optimization method for numerically-controlled oscillator provided by the present invention, the method is according to the relevance between the different carrier wave NCO forms, seek out the benchmark form that can contain different N CO form, and the benchmark form further is optimized for original 1/4th length, this method not only realizes the exact matching with the sound carrier frequency, and the storage area of NCO form is dropped to minimum.In addition, utilize the characteristic of sine value, the form after optimizing is made up storage, so that an addressing can obtain corresponding sine and two tabular values of cosine, reduced the addressing process of half.
The numerically-controlled oscillator of this table lookup optimization method that utilizes provided by the present invention has been realized having optimized to greatest extent form in television audio demodulation field, reach the exact matching with carrier frequency, accelerated addressing speed, reduced memory space, reduced chip cost, improve simultaneously the versatility of demodulating algorithm, can satisfy the demodulation of the most of simulated television audio mode in the whole world.
Description of drawings
The table look-up structural representation of numerically-controlled oscillator of the method optimized of a kind of utilization that Fig. 1 provides for present embodiment.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in further detail below in conjunction with accompanying drawing.
The numerically-controlled oscillator of the method that present embodiment provides a kind of utilization to table look-up to optimize, as shown in Figure 1, this digital controlled oscillator (Numerical controlled oscillator, NCO) comprises counting unit 2, selected cell 3, list cell 4, split cells 5 and multiplication unit 6.Counting unit 2 receives input TV audio carrier frequency 1, and calculates the index value of the input of input TV audio carrier frequency 1; List cell 4 is arranged among the ROM, the NCO list data behind the storage optimization; Selected cell 3 calculates it in the lookup table index of benchmark form according to current input TV audio carrier frequency and index value, finds corresponding tabular value and taking-up according to lookup table index; Split cells 5 is to take out tabular value from list cell 4, and high-low-position split, respectively as sine value and cosine value, then, in multiplication unit 6, sine value get negative after with sampling after television audio signals multiply each other, television audio signals after cosine value and the sampling multiplies each other, and obtains final quadrature component value 7 and quadrature component value 8, as the output valve of NCO.As long as the numerically-controlled oscillator of present embodiment for the simulated television audio signal, so also need to add analog to digital converter at front end before digital controlled oscillator is processed, carries out analog-to-digital conversion to this simulated television audio signal.
Simulated television audio frequency commonly used comprises 9 kinds of different sound carrier frequencies at present, be respectively 5.5MHz, 5.742MHz, 6.5MHz, 6.257MHz, 4.5MHz, 4.724MHz, 5.85MHz (NICAM standard), 6.552MHz (NICAM standard) and 6.0MHz, present embodiment is optimized calculating according to these 9 kinds different sound carrier frequencies according to simulated television audio frequency demodulation NCO form.For the carrier frequency of different systems, according to formula:
Wherein, f
cBe carrier frequency, sample frequency f
s=18.432MHz.
According to above-mentioned formula, can obtain these the 9 kinds NCO form length N that different sound carrier frequencies is corresponding, as shown in the table.From above table, can draw:
1) carrier frequency is that the tabular value of 6.5MHz can 839 obtains from carrier frequency is the table of 5.5MHz for the index value at interval, the corresponding symbol rule of sin value is+,+,+,+..., the cos value is+,+,+,+
2) carrier frequency is that the tabular value of 6.0MHz can 420 obtains from carrier frequency is the table of 5.5MHz for the index value at interval, the corresponding symbol rule of sin value is+,+,+,+..., the cos value is+,+,+,+
3) carrier frequency is that the tabular value of 4.724MHz can 899 obtains from carrier frequency is the table of 5.5MHz for the index value at interval, the corresponding symbol rule of sin value is+,+,+,+..., the cos value is+,+,+,+
4) carrier frequency is that the tabular value of 5.742MHz can 273 obtains from carrier frequency is the table of 6.258MHz for the index value at interval, the corresponding symbol rule of sin value is-,-,-,-..., the cos value is+,+,+,+
5) carrier frequency is that the tabular value of 4.5MHz can 282 obtains from carrier frequency is the table of 6.258MHz z for the index value at interval, the corresponding symbol rule of sin value is+,-,+,-..., the cos value is+,-,+,-
6) carrier frequency is that the tabular value of 5.85MHz can 213 obtains from carrier frequency is the table of 6.258MHz for the index value at interval, the corresponding symbol rule of sin value is+,+,+,+..., the cos value is+,+,+,+
7) carrier frequency is that the tabular value of 6.552MHz can 300 obtains from carrier frequency is the table of 6.258MHz for the index value at interval, the corresponding symbol rule of sin value is+,-,+,-..., the cos value is+,-,+,-...
According to the rule of above-mentioned carrier frequency and form length, simulated television audio frequency demodulation NCO form is optimized, in order to represent that with minimum carrier frequency other have the carrier frequency of different form lengths, carry out according to following choosing method:
1) therefrom chooses and have the corresponding carrier frequency of maximum form length, the benchmark form of the pardon maximum of the form length of this carrier frequency;
2) this carrier frequency can be expressed the carrier frequency of maximum corresponding forms of other carrier frequency as much as possible.
According to above choosing method, can draw following result:
1) carrier frequency is 6.5MHz, 4.724MHz, and the NCO form of 6.0MHz can be that the NCO form of 5.5MHz obtains by carrier frequency;
2) carrier frequency is 5.742MHz, 4.5MHz, and 5.85MHz, the NCO form of 6.552MHz can be that the NCO form of 6.258MHz obtains by carrier frequency;
3) according to the various standards of simulated television audio frequency, we can find the FM dual track, and FM/NICAM etc., the corresponding master meter of two-way carrier wave does not have overlapping part.
The method of said reference form optimization further may be summarized to be:
sin[(2nf
c(b)π)/f
s]＝sin[2(N+f
c(a))π/f
s]＝sin[(2f
c(a)π)/f
s]
Wherein, f
c(b) be carrier frequency value as benchmark NCO form, f
c(a) be need to addressing in the benchmark form the carrier frequency value, n=0,1,2 ..., the interval lookup table index, n and N value are associated, at f
c(b) and f
cIn the situation about (a) determining, the value of n is during since 0 value, and N shows f when integer occurring for the first time
c(a) NCO form can be from f
c(b) corresponding benchmark form obtains.Can draw from above-mentioned calculating, the NCO form that different carrier frequencies is corresponding can obtain from master meter.
Further, according to result obtained above, can be optimized the NCO form:
Because the one by one correspondence of cos value and sin value, we choose the NCO that carrier frequency is 5.5MHz (sin) form and carrier frequency is that NCO (sin) form of 6.258MHz is the benchmark form;
Be an addressing of convenient each NCO operation, to carrier frequency be the NCO form of 5.5MHz with (0,1152), (1,1151), (2,1150), (3,1149) ... the mode of (576,576) is stored; To carrier frequency be the NCO form of 6.258MHz with (0,768), (1,767), (2,766), (3,765) ... the mode of (384,384) is stored.
The precision of choosing sampling in the present embodiment is 8, and accordingly, the value of NCO form is chosen 7 signed numbers just can meet required precision.According to above-mentioned storage mode, the form that we will store is that length is 962 14 bit digital.
When tabling look-up addressing, follows selected cell 3 following rule:
According to the rule of the corresponding master meter of carrier wave the index value of input is mapped in the benchmark form in the list cell 4, obtains its input index in the benchmark form, the NCO sin form take carrier frequency as 5.5MHz is the benchmark addressing:
Input index (0-1151): sin value index=input index; Cos value index=1152-inputs index;
Input index (0-576): with sin value indexed addressing, read two bytes, upper byte is the sin tabular value, and low byte is got the negative cos value that is;
Input index (577-1151): with cos value indexed addressing, read two bytes, upper byte is got the negative cos tabular value that is, low byte is the sin value;
Input index (1152-2303): sin value index=2304-inputs index; Cos value index=input index-1152;
Input index (1152-1726): with cos value indexed addressing, read two bytes, upper byte is the cos tabular value, and low byte is the sin value;
Input index (1727-2303): with sin value indexed addressing, read two bytes, upper byte is the sin tabular value, and low byte is the cos value;
Input index (2304-3455): sin value index=input index-2304; Cos value index=3456-inputs index;
Input index (2304-2880): with sin value indexed addressing, read two bytes, upper byte is got the negative sin tabular value that is, low byte is the cos value;
Input index (2881-3455): with cos value indexed addressing, read two bytes, upper byte is the cos tabular value, and low byte is got the negative sin value that is;
Input index (3456-4607): sin value index=4608-inputs index; Cos value index=input index-3456;
Input index (3456-4030): with cos value indexed addressing, read two bytes, upper byte is got the negative cos tabular value that is, low byte is got the negative sin value that is;
Input index (4031-4607): with sin value indexed addressing, read two bytes, upper byte is got the negative sin tabular value that is, low byte is got the negative cos value that is;
Data greater than 4607 are successively by top sequential loop.
NCO sin form take carrier frequency as 6.258MHz is the benchmark addressing:
Input index (0-767): sin value index=input index;
Cos value index=768-inputs index;
Input index (0-384): with sin value indexed addressing, read two bytes, upper byte is the sin tabular value, and low byte is got the negative cos value that is;
Input index (385-767): with cos value indexed addressing, read two bytes, upper byte is got the negative cos tabular value that is, low byte is the sin value;
Input index (768-1535): sin value index=1536-inputs index;
Cos value index=input index-768;
Input index (768-1150): with cos value indexed addressing, read two bytes, upper byte is the cos tabular value, and low byte is the sin value;
Input index (1151-1535): with sin value indexed addressing, read two bytes, upper byte is the sin tabular value, and low byte is the cos value;
Input index (1536-2303): sin value index=input index-1536;
Cos value index=2304-inputs index;
Input index (1536-1920): with sin value indexed addressing, read two bytes, upper byte is got the negative sin tabular value that is, low byte is the cos value;
Input index (1921-2303): with cos value indexed addressing, read two bytes, upper byte is the cos tabular value, and low byte is got the negative sin value that is;
Input index (2304-3071): sin value index=3072-inputs index;
Cos value index=input index-2304;
Input index (2304-2688): with cos value indexed addressing, read two bytes, upper byte is got the negative cos tabular value that is, low byte is got the negative sin value that is;
Input index (2689--3071): with sin value indexed addressing, read two bytes, upper byte is got the negative sin tabular value that is, low byte is got the negative cos value that is;
Data greater than 3071 are successively by top sequential loop.
What need to any be described is, the realization of this programme is not limited to provide in the present embodiment 9 kinds of different sound carrier frequencies, for the different sound carrier frequency of other kinds and number, the table look-up numerically-controlled oscillator of the method optimized of a kind of utilization that still can utilize this programme to realize.At this moment, in the constant situation of other conditions, list cell and corresponding selected cell need more general form optimization method and corresponding addressing method, and the part of modification comprises two places:
The first, in the situation for multiple different sound carrier frequencies, the method for benchmark form optimization is summarised as:
sin[(2nf
c(b)π)/f
s]＝sin[2(N+f
c(a))π/f
s]＝sin[(2f
c(a)π)/f
s]
Wherein, f
c(b) be carrier frequency value as benchmark NCO form, f
c(a) be need to addressing in the benchmark form the carrier frequency value, n=0,1,2 ..., the interval lookup table index, n and N value are associated, at f
c(b) and f
cIn the situation about (a) determining, the value of n is during since 0 value, and N shows f when integer occurring for the first time
c(a) NCO form can be from f
c(b) corresponding benchmark form obtains.Can draw from above-mentioned calculating, the NCO form that different carrier frequencies is corresponding can obtain from master meter.
The second, the benchmark form length after supposing to optimize is W, for more general addressing method, can adopt following methods to carry out:
The storage of benchmark form according to (0, w-1), (1, w-2), (2, w-3) ... the mode of ((w-1)/2, w-1)/2) is stored, so that the form address dwindles half;
Benchmark form length after supposing to optimize is W, the addressing of form:
The first step: with sin, the input index of cos value corresponds to the index in the form after the optimization, and rule is:
Input index (0-(w-1)-1), sin value index=input index,
Cos value index=(w-1)-input index;
Input index (w-1-2 (w-1)-1), sin value index=2 (w-1)-input index;
Cos value index=input index-(w-1)
Input index (2 (w-1)-3 (w-1)-1), sin value index=input index-2 (w-1);
Cos value index=3 (w-1)-input index;
Input index (3 (w-1)-4 (w-1)-1), sin value index=4 (w-1)-input index;
Cos value index=input index-3 (w-1);
Second step, according to the rule of form stores, the address realm of the form after the optimization is (0-(w-1)/2), and the index value that obtains according to the first step carries out addressing to form, and rule is:
Sin value index (0-(w-1)/2): must be worth with sin value indexed addressing, upper byte is the sin tabular value, and low byte is got the negative cos value that is;
Cos value index (0-(w-1)/2): must be worth with cos value indexed addressing, upper byte is the cos tabular value, and low byte is the sin value;
The 3rd step, the sin that resets and obtain, cos value sign bit, rule is
Input index (0-(w-1)-1): sin value=sin value; The cos value=-the cos value;
Input index (w-1-2 (w-1)-1): sin value=sin value; Cos value=cos value;
Input index (2 (w-1)-3 (w-1)-1): the sin value=-the sin value; Cos value=cos value;
Input index (3 (w-1)-4 (w-1)-1): the sin value=-the sin value; The cos value=-the cos value.
In situation without departing from the spirit and scope of the present invention, can also consist of many very embodiment of big difference that have.Should be appreciated that except as defined by the appended claims, the invention is not restricted at the specific embodiment described in the specification.
Claims (7)
1. a table lookup optimization method is used for numerically-controlled oscillator, it is characterized in that described table lookup optimization method may further comprise the steps:
A. represent the NCO form that different TV audio carrier frequencies are corresponding with the benchmark form, specifically may further comprise the steps:
A 1. calculates the corresponding form length of different TV audio carrier frequencies, the tabulation of tabulation length;
A2. the corresponding form of form length of choosing the numerical value maximum from the tabulation of described form length is as the benchmark form, according to formula:
sin[(2nf
c(b)π)/f
s]=sin[2(N+f
c(a))π/f
s]=sin[(2f
c(a)π)/f
s]
Wherein, f
c(b) be TV audio carrier frequency corresponding to benchmark form, f
c(a) be need to addressing in the benchmark form other TV audio carrier frequencies, n and N are integer, n=0,1,2 ...,
Getting TV audio carrier frequency corresponding to described benchmark form is f
c(b), the f in the described formula of described other TV audio carrier frequency substitutions
c(a), n when the right-hand N of described formula integer occurs for the first time, represents f since 0 value this moment
c(a) NCO form can pass through f
c(b) corresponding benchmark form represents;
B. described benchmark form is dwindled being optimized to 1/4th length, other non-benchmark forms are obtained from described benchmark form;
C. according to sinusoidal regular, described benchmark form is further optimized storage, so that an addressing just obtains sine value and cosine value, specifically may further comprise the steps:
C1. the benchmark form length of getting after the optimization is w, and the input index value of sin and cos value is corresponded to index in the form after the optimization, and rule is:
Input index (0-(w-1)-1), sin value index=input index,
Cos value index=(w-1)-input index;
Input index (w-1-2 (w-1)-1), sin value index=2 (w-1)-input index,
Cos value index=input index-(w-1);
Input index (2 (w-1)-3 (w-1)-1), sin value index=input index-2 (w-1),
Cos value index=3 (w-1)-input index;
Input index (3 (w-1)-4 (w-1)-1), sin value index=4 (w-1)-input index,
Cos value index=input index-3 (w-1);
C2. according to the rule of form stores, the address realm of the form after the optimization is (0-(w-1)/2), and the index value that obtains according to step c1 carries out addressing to form, and rule is:
Sin value index (0-(w-1)/2): must be worth with sin value indexed addressing, upper byte is the sin tabular value, and low byte is got the negative cos value that is;
Cos value index (0-(w-1)/2): must be worth with cos value indexed addressing, upper byte is the cos tabular value, and low byte is the sin value;
Sin and the cos value sign bit of c3. resetting and obtaining, rule is:
Input index (0-(W-1)-1): sin value=sin value; The cos value=-the cos value;
Input index (w-1-2 (w-1)-1): sin value=sin value; Cos value=cos value;
Input index (2 (w-1)-3 (w-1)-1): the sin value=-the sin value; Cos value=cos value;
Input index (3 (w-1)-4 (w-1)-1): the sin value=-the sin value; The cos value=-the cos value.
2. table lookup optimization method as claimed in claim 1 is characterized in that, when the form length of described numerical value maximum has two when above, chooses one of them corresponding form as the benchmark form.
3. table lookup optimization method as claimed in claim 1 or 2, it is characterized in that, when the form of described other TV audio carrier frequencies can not represent with a benchmark form, in the scope of described other TV audio carrier frequencies, the form of all described other TV audio carrier frequencies represents that with the benchmark form method of the NCO form that different TV audio carrier frequencies are corresponding finds out another benchmark form again according to described, until can find corresponding benchmark form to represent.
4. table lookup optimization method as claimed in claim 2, it is characterized in that, described different TV audio carrier frequency comprises 9 kinds of different carrier frequencies, is respectively 5.5MHz, 5.742MHz, 6.5MHz, 6.258MHz, 4.5MHz, 4.724MHz, 5.85MHz, 6.552MHz and 6.0MHz.
5. one kind is utilized the as claimed in claim 1 numerically-controlled oscillator of table lookup optimization method, it is characterized in that, comprising:
List cell is arranged among the ROM, stores the NCO list data after described table lookup optimization method is optimized;
Counting unit receives input TV audio carrier frequency, and to the counting of described input TV audio carrier frequency, as index value;
Selected cell, described selected cell carries out addressing according to described input sound carrier frequency and described index value to described list cell, obtains required NCO list data;
Split cells receives described required NCO list data, and described required NCO list data is split as sine value and cosine value;
Multiplication unit receives described sine value and described cosine value, and carries out multiplying with input TV audio carrier frequency respectively, obtains respectively the first quadrature component value and the second quadrature component value.
6. numerically-controlled oscillator as claimed in claim 5 is characterized in that, it is that benchmark list data corresponding to 5.5MHz and TV audio carrier frequency are benchmark list data corresponding to 6.258MHz that described NCO list data is preserved the TV audio carrier frequency.
7. numerically-controlled oscillator as claimed in claim 5, it is characterized in that, described NCO list data can represent 9 kinds of different corresponding forms of TV audio carrier frequency, and described 9 kinds of different TV audio carrier frequencies are respectively 5.5MHz, 5.742MHz, 6.5MHz, 6.258MHz, 4.5MHz, 4.724MHz, 5.85MHz, 6.552MHz and 6.0MHz.
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| CN1355655A (en) * | 2000-11-23 | 2002-06-26 | 华为技术有限公司 | Digital method for generating local oscillation signal and numeral controlled oscillator |
| EP1429231A1 (en) * | 2002-12-11 | 2004-06-16 | Samsung Electronics Co., Ltd. | Numerical control oscillator, digital frequency converter and radio frequency unit |
| CN1716760A (en) * | 2004-06-14 | 2006-01-04 | 安捷伦科技有限公司 | Numerically controlled oscillator and method of operation |
| CN101242391A (en) * | 2007-02-09 | 2008-08-13 | 卓胜微电子（上海）有限公司 | Carrier frequency recovery and tracking method |
| CN101335509A (en) * | 2007-06-29 | 2008-12-31 | 大唐移动通信设备有限公司 | Method and digital control oscillator for sinusoidal and cosine signal generator |
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|---|---|---|---|---|
| CN1355655A (en) * | 2000-11-23 | 2002-06-26 | 华为技术有限公司 | Digital method for generating local oscillation signal and numeral controlled oscillator |
| EP1429231A1 (en) * | 2002-12-11 | 2004-06-16 | Samsung Electronics Co., Ltd. | Numerical control oscillator, digital frequency converter and radio frequency unit |
| CN1716760A (en) * | 2004-06-14 | 2006-01-04 | 安捷伦科技有限公司 | Numerically controlled oscillator and method of operation |
| CN101242391A (en) * | 2007-02-09 | 2008-08-13 | 卓胜微电子（上海）有限公司 | Carrier frequency recovery and tracking method |
| CN101335509A (en) * | 2007-06-29 | 2008-12-31 | 大唐移动通信设备有限公司 | Method and digital control oscillator for sinusoidal and cosine signal generator |
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