Background
The environment adaptation requirements of communication systems to communication equipment are higher and higher, and the design and manufacture of the communication industry also face a large number of test measurement and data acquisition tests. For example, radio frequency wireless communications require filters to remove unwanted information and interference. The signal passing through the filter will cause a phase shift resulting in an increase in the error rate. The development of modern wireless data communication is high speed, reliable and secure, which requires excellent filter characteristics and low phase offset, thereby reducing the bit error rate.
To manufacture a high performance filter, debugging is more important than design. Because the inductance of the coils in the filter is difficult to accurately test, various factors (collectively referred to as parasitic parameters) such as turn-to-turn capacitance, contact capacitance, and mutual inductance between the coils can cause a large difference between the characteristics of the actually manufactured filter and the characteristics expected during design. The effects and errors caused by these parasitic parameters must be adjusted to compensate.
The debugging of the filter has been a major and difficult point for the production process of the filter (including cavity filter, ceramic dielectric filter, etc.). Various filter debugging methods and theories have been successively developed by the industry and academia. The diagnosis of the filter has important guiding significance for the debugging of the filter. The filter diagnosis technique is to extract necessary information from the current scattering parameter (S parameter) of the filter and obtain the error of each tuning rod in the current state of the filter. The coupling matrix based diagnostic technique is a common method of filter diagnostics, which reconstructs the coupling matrix of the filter from the S-parameters and compares the coupling matrix with the standard coupling matrix of the filter to derive the error of each tuning rod. Since each element of the coupling matrix can correspond to the tuning rod one to one, the practical guiding significance of the method in debugging is very clear.
In the existing coupling matrix diagnosis method, a characteristic polynomial of a filter is obtained by using a Cauchy method, admittance parameters of the filter are obtained according to the characteristic polynomial, and partial fractional decomposition is carried out on the admittance parameters so as to obtain all elements of the coupling matrix, so that better diagnosis precision is obtained.
However, in the debugging process, it is a gradual process from detuning to completely reaching the technical index, so that the debugging process has many intermediate states, and the prior art has the problem of erroneous judgment caused by insufficient accuracy of obtaining the intermediate states when the intermediate states are obtained. According to the method proposed by Amari in the document "Adaptive synthesis and design of receiver filters with source/load-multiresotor coupling", the corresponding S parameters can be reversely deduced through the coupling matrix, and the reversely deduced S parameters can be compared with the S parameters measured by the vector network analyzer, so that whether the obtained coupling matrix is accurate or not can be guided.
Detailed Description
The invention is further illustrated by the following figures and examples.
The variable symbols used in the present invention are not limited to those used in the present invention. It is considered to be within the scope of the present invention to use other variable symbols instead of the variable symbols used in the filter tuning method of the present invention. The basic flow chart of constructing the coupling matrix by using the Cauchy method is shown in FIG. 1:
the detailed process of extracting the coupling matrix by improving the Cauchy method is as follows.
And S1, extracting the S parameters of the filter to be adjusted by using a Vector Network Analyzer (VNA) for standby.
S2, StructureHThe matrix is as follows:
wherein, VM(fL) Is a van der mond matrix, which is constructed as follows:
wherein,f 0 is the center frequency of the pass band and is,Bis the passband bandwidth, andQunamely the unloaded Q value to be extracted.f(i)The frequency corresponding to the S-parameter extracted for the VNA.
Remember again:
wherein,npfor the number of filter poles and reflection zeros,nzthe number of zeros is transmitted for the filter. Then solving equation (5) yields a characteristic polynomialFs、PsAndEsrespectively is a(1),a(2)And a(3)。
The method for solving a by carrying out singular value decomposition on the H matrix(1),a(2)And a(3). Namely, the method comprises the following steps:
Vthe last column of (a) is the feature vector, which is represented by a(1),a(2)And a(3)And (4) forming.
S3, after the eigenvector is obtained, the admittance matrix can be constructed according to the eigenvector[Y N ]
If the order of the filter is recorded asNAnd y is11And y12Need not be used in subsequent calculations, then y21And y22Is solved as follows:
Nis an even number:
Nis odd number:
wherein,
e i andf i ,i=0,1,2,3...Nare respectively polynomialE S AndF S the complex coefficient of (a).
And erThe ripple factor, if the designed in-band return loss of the filter is constantRLThen it is defined as follows:
the invention measures the average value of the in-band return loss in real timeRL A Instead of the formerRLAs a return loss value in the intermediate state, it is defined as follows:
wherein,S 11 (i),i=1,2,…Mis S in the pass band of the filter11And (6) measuring the values.
For the case of asymmetric zeros and a finite number of zeros smaller than the filter order, there are:
otherwise:
s4, for y in fractional form according to equation (7)21And y22Partial expansion is carried out to obtain corresponding pole lambda11、λ21And a residue r11、r21Note λ11、λ21And a residue r11、r21Is to be according to lambda21The imaginary parts are sorted in ascending order.
S5, according to the pole lambda11(k)、λ21(k) And a residue r11(k)、r21(k) The elements of the coupling matrix may be constructed according to (8):
further, the lateral coupling matrix can be obtained as follows:
according to the transverse coupling matrix, coupling matrixes corresponding to various filter structures in practical application can be obtained through matrix similarity transformation.
The invention, if the design target return loss of the filter is utilizedRLAs a basis for calculation, in the process of debugging the filter, since the difference between the in-band return loss and the target RL is large and the difference at each frequency point is not uniform, the S parameter of the coupling matrix back-estimation obtained by the method is greatly different from the S parameter measured by the actual filter.
The effect of the invention is illustrated below by taking the tuning of a filter with 10 reflection zeros, 10 poles and 4 zeros as an example,
average value of in-band return loss measured in real time according to the inventionRL A Instead of the formerRLThe coupling matrix constructed by the above method as the return loss value at the intermediate state is as follows:
embodiments of the present invention can be implemented in hardware or software, depending on certain implementation requirements. The implementation can be performed using the following digital storage medium having electronically readable control signals stored thereon: such as a floppy disk, DVD, CD, ROM, PROM, EPROM, EEPROM or flash memory, which cooperates with (or is capable of cooperating with) a programmable computer system such that the respective method is performed.
Some embodiments according to the invention comprise a data carrier with electronically readable control signals, the data carrier being capable of cooperating with a programmable computer system such that one of the methods described herein is performed.
Generally, embodiments of the invention can be implemented as a computer program product having a program code which is operable to perform one of the methods when the computer program product runs on a computer. For example, the program code may be stored on a machine readable carrier.
Other embodiments include a computer program for performing one of the methods described herein, where the program is stored on a machine-readable carrier or non-transitory storage medium.
In other words, an embodiment of the inventive method is thus a computer program with computer code for performing one of the methods described herein, when the computer program runs on a computer.
Another embodiment of the inventive method is thus a data carrier (or digital storage medium, or computer readable medium) comprising a computer program recorded thereon for performing one of the methods described herein.
Another embodiment of the invention is thus a data stream or signal sequence representing a computer program for performing one of the methods described herein. The data stream or signal sequence may for example be configured to be communicated via a data communication connection, for example via the internet.
Another embodiment comprises a processing device, such as a computer or programmable logic device, configured or adapted to perform one of the methods described herein.
Another embodiment comprises a computer having installed thereon a computer program for performing one of the methods described herein.
In some embodiments, a programmable logic device (e.g., a field programmable gate array) may be used to perform some or all of the functions of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor to perform one of the methods described herein. In general, the method is preferably performed by any hardware device.
The above-described embodiments are merely illustrative of the principles of the present invention. It is to be understood that modifications and variations to the arrangements and details described herein will be apparent to those skilled in the art. It is therefore intended that the scope of the claims be limited only by the pending patent claims and not by the specific details given herein by way of the description and illustration of the embodiments.