CN110736879B

CN110736879B - Short-wave radio frequency direct-acquisition bridge type vector impedance detection method

Info

Publication number: CN110736879B
Application number: CN201910938560.4A
Authority: CN
Inventors: 邹晶晶; 罗磊
Original assignee: CETC 30 Research Institute
Current assignee: CETC 30 Research Institute
Priority date: 2019-09-30
Filing date: 2019-09-30
Publication date: 2022-03-18
Anticipated expiration: 2039-09-30
Also published as: CN110736879A

Abstract

The invention discloses a short-wave radio frequency direct acquisition bridge type vector impedance detection method, which comprises the following stepsThe method comprises the following steps: step one, building a bridge type detection circuit; step two, coupling voltage signals

Performing radio frequency direct sampling; and step three, calculating to obtain a load impedance value through amplitude and phase information of the two paths of sampling signals. Compared with the prior art, the invention has the following positive effects: the invention provides a short-wave radio frequency direct acquisition bridge type vector impedance detection (hereinafter referred to as bridge type detection) method, which aims at solving the problems of complex circuit, large volume, high power consumption, high data processing complexity and the like of a short-wave vector impedance detector under a frequency conversion processing framework and improves two aspects of a circuit processing framework and a data processing algorithm. Compared with the traditional method, the method has a simpler circuit processing framework, reduces the complexity, power consumption and volume of a processing circuit, optimizes a data processing algorithm and improves the detection precision to a certain extent.

Description

Short-wave radio frequency direct-acquisition bridge type vector impedance detection method

Technical Field

The invention relates to a short-wave radio frequency direct acquisition bridge type vector impedance detection method.

Background

Vector impedance detection is a key functional module in a vector short wave antenna tuner (hereinafter referred to as an "antenna tuner"), is the basis of a tuning algorithm executed by the antenna tuner, and directly determines the tuning accuracy of the antenna tuner. The high-precision vector impedance detection technology can provide accurate load impedance detection in a short-wave full-frequency band, and is a key technology for realizing a fast and high-precision tuning tuner. Two circuit processing architectures generally exist for vector impedance detection techniques in the short-wave band: the frequency conversion processing framework and the radio frequency direct sampling processing framework are adopted.

The working principle of the frequency conversion processing framework is as follows: after the radio frequency signal is subjected to down-conversion, voltage and current vector signals on a load are obtained through an ADC (analog-to-digital converter), and the vector impedance definition formula is based on

And calculating to obtain the load impedance. The method is intuitive, and the amplitude of the impedance is the phase difference of the voltage and current signals. The voltage and current vector signal acquisition mode is generally completed by adopting a coupler, a transformer couples a radio frequency voltage signal, a current coupler couples a current signal passing through a load, in order to reduce the influence of the coupler on the load impedance, the coupling coefficient is relatively small, the coupled signal needs to be amplified and then subjected to subsequent down-conversion, filtering and other processing to obtain an intermediate frequency signal, the intermediate frequency signal is subjected to low-frequency sampling after being amplified and filtered, the amplitude and phase information of the low-frequency sampling signal is extracted in a digital domain, and an impedance value is obtained by calculation, and the processing framework is as shown in fig. 1.

The circuit processing framework of the method is complex, load impedance is calculated through data processing after intermediate frequency sampling, Hilbert transform is often needed for extracting current and voltage signal amplitude and phase characteristics in the data processing, and algorithm complexity is high. In addition, in the engineering implementation, the coupler has natural frequency characteristics, and the imbalance of the two radio frequency processing circuits causes great influence on the impedance detection error (the error is 5% -10%). The inductive coupler in the detection mode has the advantages of large size, complex circuit and high power consumption, and is difficult to realize in equipment with limited volume and power consumption.

Under the radio frequency direct sampling framework, voltage and current signals representing load impedance directly enter a high-speed ADC for sampling without down-conversion processing, and data processing is carried out in a digital domain to obtain the load impedance. In this way, a down-conversion processing circuit does not exist, the circuit complexity is reduced, and the design with low power consumption and small volume can be realized.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a short-wave radio frequency direct acquisition bridge type vector impedance detection method.

The technical scheme adopted by the invention for solving the technical problems is as follows: a short-wave radio frequency direct acquisition bridge type vector impedance detection method comprises the following steps:

step one, building a bridge type detection circuit;

step two, coupling voltage signals

Performing radio frequency direct sampling;

and step three, calculating to obtain a load impedance value through amplitude and phase information of the two paths of sampling signals.

Compared with the prior art, the invention has the following positive effects:

the invention provides a short-wave radio frequency direct acquisition bridge type vector impedance detection (hereinafter referred to as bridge type detection) method, which aims at solving the problems of complex circuit, large volume, high power consumption, high data processing complexity and the like of a short-wave vector impedance detector under a frequency conversion processing framework and improves two aspects of a circuit processing framework and a data processing algorithm. Compared with the traditional method, the method has a simpler circuit processing framework, reduces the complexity, power consumption and volume of a processing circuit, optimizes a data processing algorithm, and improves the detection precision to a certain extent, and the method is specifically represented as follows:

1) in the aspect of hardware circuit implementation, based on a radio frequency direct acquisition circuit framework and parts such as a non-inductive coupler, a mixer, a filter, an amplifier and the like, the size and the power consumption of a detection circuit module are reduced, and detection errors introduced by a peripheral circuit are reduced;

2) a pure resistance network with better short-wave frequency characteristics is adopted to replace a voltage and current coupler, so that the detection error caused by the frequency characteristics of the coupler is reduced;

3) in the aspect of a data processing algorithm, the sampling data is directly processed without performing down-conversion, Hilbert conversion and other processing on the data, and the processing algorithm is simple and efficient.

Drawings

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic block diagram of vector impedance detection for a variable frequency architecture;

FIG. 2 is a schematic block diagram of a bridge detection circuit architecture;

fig. 3 is a diagram illustrating an example of phase calculation.

Detailed Description

The bridge detection circuit structure adopted by the invention is shown in figure 2, and the detection circuit consists of a reference bridge impedance Z₀And a signal sampling circuit.

For any load Z ═ R + jX, it can be assumed that Z flows through₀Also flows into the load Z_LThe following formula holds:

wherein,

is obtained by

Wherein

Sampling signal

And satisfies the following formula:

r1 and R2 in the signal sampling circuit are pure resistors, when R1 and R2 are far greater than Z_LIn time, after sampling, the detection signal is not influenced at the reference bridge impedance Z₀The phases at both ends are only scaled down equally in magnitude, so that the ratio of the vector voltages is available

Expressed as:

wherein | U₀|、|U₁L is the amplitude of the sampled signal,

is the phase difference. To pair

To proceed directlySampling, analyzing and processing the sampling point data, extracting phase and amplitude information, and calculating to obtain load impedance Z_L。

It can be seen that only the detector Z has to be determined₀The voltage vectors of the front end and the rear end can obtain the load Z_L. Due to the fact that₀Also flows through Z_LThis requires that the introduction of the branch U1 not affect Z_LI.e., the impedance of the U1 branch is much greater than the load branch impedance.

And extracting amplitude and phase information of the two paths of signals based on sampling point data, and substituting the amplitude and phase information into an impedance calculation formula to obtain a load impedance value. The amplitudes of the two paths of sampling signals can be obtained by calculating the root mean square value from the sampling point data. The phase difference of the signals is carried out in two steps: first step of calculating absolute value of phase difference

The second step determines the lead/lag relationship of U0 and U1 to determine the sign of the phase difference.

The determination of (2) is based on a correlation analysis method. Two-way sampling signal U₀(n) and U₁(n) can be represented as:

wherein T is_SIs the sampling period. Cross correlation function thereof

Wherein N is the number of the sampling points,

absolute value of phase difference

The phase lead-lag judgment is based on a statistical thought, the occurrence time of the maximum value of the two paths of signals is judged, the occurrence time of the maximum value is counted, and the phase difference symbol is judged according to a statistical result. The maximum value is defined as: in a section of continuous sampling interval, if the value of a certain point in the interval is greater than the values of all the points in the preamble in the interval and is greater than the values of all the points in the sequence in the interval, the point is called as a maximum value point of the sequence. The length of the interval varies with the frequency of the tuning signal, taking into account sampling errors. Comparing the time axes (the sampled sequence IDs) of the maximum value points, defining the point with the maximum value at first as a phase advance point of the sequence, defining the point with the maximum value at the later as a sequence phase lag point, and discarding the point if the IDs of the maximum values are the same. Counting the number of leading and lagging points of the phase, if the number of leading points of the phase is more than the number of lagging points of the phase, determining that the phase is leading, and the phase difference sign is plus; if the number of the phase lag is larger than the number of the phase lead, the phase lag is determined, and the phase difference sign is "-".

The phase calculation process is exemplified below. FIG. 3 shows data when the detected signal is 2MHz and the number of samples is 128. Wherein: fig. 3 (top) is a time domain signal, fig. 3 (middle) is sample data, and fig. 3 (bottom) is a two-path signal maximum (non-0 point) sequence.

The absolute value of the phase difference can be obtained by the formula ninthly

The U0 maximum point is the same as the U1 maximum point, and both lag behind U1, the phase difference is determined to lag, the phase difference sign bit "-", and therefore, the final phase difference:

Claims

1. a short-wave radio frequency direct acquisition bridge type vector impedance detection method is characterized by comprising the following steps: the method comprises the following steps:

step one, building a bridge type detection circuit, wherein the bridge type detection circuit is composed of a reference bridge impedance Z₀And the signal sampling circuit consists of sampling resistors R1 and R2 and a high-speed ADC (analog to digital converter), wherein R1 and R2 are pure resistors, and R1 and R2 are far greater than load impedance Z_LTwo groups of series-connected R1 and R2 are connected in parallel at Z₀At two ends, R1 and R2 divide the main path radio frequency signal into partial pressure and sample, and then send the partial pressure and sample into ADC, and the ADC completes synchronous sampling of two-path sampling signal to obtain digital signal U₀(n)、U₁(n); and calculating the load impedance value according to the following formula:

wherein: i U₀|、|U₁L is the amplitude of the sampled signal,

the phase difference is calculated by the following method:

(1) the absolute value of the phase difference is calculated according to the following formula

Wherein:

n is the number of sampling points;

(2) according toU₀And U₁Determining the phase difference sign according to the lead/lag relation;

step two, coupling voltage signals

Performing radio frequency direct sampling, wherein

Is Z₀The radio frequency signals at two ends are subjected to equal proportion voltage division by sampling resistors R1 and R2 to obtain coupling voltage signals;

2. The short-wave radio frequency direct sampling bridge type vector impedance detection method according to claim 1, characterized in that: the amplitudes of the two paths of sampling signals are obtained by calculating the root mean square value of sampling point data.

3. The short-wave radio frequency direct sampling bridge type vector impedance detection method according to claim 1, characterized in that: the method for determining the phase difference sign comprises the following steps: comparing the time axes of the maximum value points, defining the point with the maximum value as a phase advance point of the sequence, and defining the point with the maximum value as a phase lag point of the sequence; counting the number of leading points and the number of lagging points of the phase: if the number of phase advance points is more than that of phase lag points, the phase advance is determined, and the phase difference sign is plus; if the number of phase lag points is more than the number of phase lead points, the phase lag is determined, and the phase difference sign is "-".