JP4554006B2 - Frequency error detection method and frequency error detection apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a frequency error detection method and a frequency error detection device for detecting an error in the frequency of an input signal used in an automatic frequency correction circuit or the like that automatically corrects the frequency.
[0002]
[Prior art]
As a conventional frequency error detector for detecting an error in the frequency of an electric signal, a cross product type frequency error detector described in Japanese Patent Laid-Open No. 9-200209 is known. A conventional cross product type frequency error detector is shown in FIG.
[0003]
This frequency error detector includes an input terminal 102 for inputting an in-phase component of a received signal and an input terminal 104 for inputting a quadrature component of the received signal. Further, the delay element 106 that delays the signal input from the input terminal 102 by time τ 1, the delay element 108 that delays the signal input from the input terminal 102 by time τ 2, the output of the delay element 106, and the input terminal 104 A multiplier 110 that multiplies the input signal, a multiplier 112 that multiplies the output of the delay element 108 and the signal input from the input terminal 102, and the difference between the output of the multiplier 110 and the output of the multiplier 112. And a subtractor 114 for obtaining and outputting. The frequency error component that is the output of the subtracter 114 is output from the output terminal 116.
[0004]
If the in-phase component of the received signal is sin (Δωt + θ) and the quadrature component is cos (Δωt + θ), the output of the subtractor 114 is sin (Δωτ1). When the frequency error is sufficiently small, the relational expression sin (Δωτ1) ≈Δωτ1 is established, and the output of the frequency error detector can be approximated as a frequency error.
[0005]
[Problems to be solved by the invention]
However, when the frequency error increases, the above approximation is not established and the detection error increases. For this reason, it has been difficult to correct a wideband frequency error.
[0006]
An object of the present invention is to provide a frequency error detection method and a frequency error detection apparatus capable of detecting a wideband frequency error.
[0007]
[Means for Solving the Problems]
In the frequency error detection method for detecting an error in the frequency of an input signal, the object is to count the frequency of the input signal, and to convert the frequency variation of the input signal into an amplitude variation. based on the frequency of the signal, the control Gyoshi such gain is changed at a frequency near, by the filter, and converts the frequency variation of the input signal amplitude variations, on the basis of the converted amplitude variations by the filter This is achieved by a frequency error detection method characterized by detecting an error in the frequency of the input signal.
[0008]
The object is to provide a frequency error detecting device for detecting an error in the frequency of an input signal, a filter for converting the frequency fluctuation of the input signal into an amplitude fluctuation, means for counting the frequency of the input signal, and means for counting. Based on the counted frequency of the input signal, means for controlling the characteristics of the filter so that the gain changes in the vicinity of the frequency, and an error in the frequency of the input signal based on the amplitude fluctuation converted by the filter It is achieved by a frequency error detecting device characterized by having a detecting means for detecting.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
A frequency error detection apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a circuit diagram of a frequency error detection device according to the present embodiment, and FIG. 2 is a graph showing filter characteristics in the frequency error detection device according to the present embodiment.
[0010]
In the frequency error detection device of this embodiment, the input signal is input to the YIG tuning filter 10. On the other hand, the input signal is also input to the frequency coefficient means 16 and the frequency of the input signal is counted. Based on the frequency value counted by the frequency counting unit 16, the filter frequency control unit 18 changes the attenuation characteristic of the YIG tuning filter 10, for example, the cut-off frequency, so that the optimum frequency characteristic according to the frequency of the input signal is obtained. To be.
[0011]
For example, if the frequency of the input signal is 1 to 1.5 GHz, the cutoff frequency as shown in FIG. 2A is 1 GHz, and if the frequency of the input signal is 1.5 to 2 GHz, FIG. The attenuation characteristic of the YIG tuning filter 10 is changed so that the cutoff frequency as shown in FIG. Thereby, the YIG tuning filter 10 has a characteristic that attenuates substantially linearly in the vicinity of the frequency f of the input signal. Due to the attenuation characteristics of the YIG tuning filter 10, the frequency fluctuation of the input signal can be converted into the amplitude fluctuation of the output signal.
[0012]
The output signal from the YIG tuning filter 10 is input to the detector 12, and its amplitude vibration is detected. The output signal of the detector 12 is input to the differential amplifier 14. A predetermined offset voltage is input to the differential amplifier 14, and the difference between the output signal from the detector 12 and the predetermined offset voltage is output from the differential amplifier 14. This output signal becomes a frequency error.
[0013]
The operation of the frequency error detection device of this embodiment will be described using equations. When the amplitude of the input signal is A and the frequency is f, the input signal is expressed as A · sin (2πft).
[0014]
When the characteristic of the YIG tuning filter 10 is G when the gain is G and the slope of the attenuation characteristic near the frequency f is K (= ΔG / Δf), the output signal of the YIG tuning filter 10 is A · G · sin (2πft). At this time, the output of the detector 12 is A · G. Since A · G is input to the differential amplifier 14 as an offset voltage, the output signal of the differential amplifier 14 becomes zero.
[0015]
When the frequency f of the input signal varies by Δf, the input signal becomes A · sin (2π (f + Δf) t). The output signal of the filter 10 at this time has an attenuation characteristic as shown in FIG.
A · (G + ΔG) · sin (2π (f + Δf) t)
= A · (G + K · Δf) · sin (2π (f + Δf) t)
It becomes. The output signal of the detector 12 at this time is A · (G + K · Δf). At this time, from the differential amplifier 14,
A · (G + K · Δf) −A · G = A · K · Δf
Is output. In the output signals A, K, and Δf, A is the amplitude of the input signal, and K is the slope of the attenuation characteristic of the YIG tuning filter 10, and therefore is a value proportional to the frequency variation Δf.
[0016]
As described above, according to the present embodiment, the detection result depends only on the frequency fluctuation amount Δf and not on the frequency fluctuation ratio (Δf / f), and thus falls within the range of the attenuation characteristic of the filter inclination K. As long as it is possible to detect a frequency error in a wide band, it is possible to perform frequency correction in a wide band based on the detection result. Furthermore, even if the frequency band of the input signal is greatly different, the filter characteristics can be automatically converted to an optimum one suitable for the frequency band of the input signal, so that further wideband frequency correction is possible. .
[0017]
An application example of the frequency error detection apparatus according to the present invention will be described.
[0018]
When the frequency of the signal under measurement fluctuates in the spectrum analyzer, the frequency of the signal under measurement can be made constant by using the frequency error detection device according to the present invention. The frequency error of the signal under measurement is detected by the frequency error detection device according to the present invention, and the detection result is fed back to make the frequency of the signal under measurement constant. In this way, it is possible to make the frequency constant without affecting the signal under measurement unlike the PLL.
[0019]
A frequency error detection method for a high frequency input signal will be described. In particular, in the case of a high-frequency input signal, it is conceivable that a filter having a large slope of attenuation characteristics at that frequency cannot be prepared. In such a case, a high frequency input signal is converted into a low frequency signal, and a frequency error is detected using a filter having a large slope of attenuation characteristics at the low frequency. For example, a 4 GHz input signal is converted into a 100 MHz signal, and an error in the frequency of the 100 MHz signal is detected using a filter having a large slope of the attenuation characteristic at 100 MHz.
[0020]
The present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, the frequency fluctuation is converted into the amplitude fluctuation using the attenuation characteristic in which the gain of the filter attenuates. However, the frequency fluctuation may be converted into the amplitude fluctuation using the characteristic in which the gain of the filter increases. .
[0021]
In addition, if the frequency variation of the input signal is converted into the amplitude variation by the filter and the frequency error of the input signal is detected based on the amplitude variation, the configuration is limited to the specific configuration of the above embodiment. is not.
[0022]
【The invention's effect】
As described above, according to the present invention, since the detection result depends only on the amount of frequency fluctuation, it is possible to detect a frequency error in a wide band and perform wideband frequency correction based on the detection result. Furthermore, even if the frequency band of the input signal is greatly different, the filter characteristics can be automatically converted to an optimum one suitable for the frequency band of the input signal, so that further wideband frequency correction is possible. .
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a frequency error detection apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing characteristics of a YIG tuning filter in the frequency error detection device of one embodiment of the present invention.
FIG. 3 is a circuit diagram of a conventional cross-product type frequency error detector.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... YIG tuning filter 12 ... Detector 14 ... Differential amplifier 16 ... Microwave counter 18 ... Constant current source 102, 104 ... Input terminal 106, 108 ... Delay element 110, 112 ... Multiplier 114 ... Subtractor 116 ... Output terminal

Claims (2)

In the frequency error detection method for detecting the frequency error of the input signal,
Count the frequency of the input signal,
The characteristics of the filter for converting a frequency variation of the input signal amplitude variations, on the basis of the frequency of the counted input signal, Gyoshi control so that the gain is changed at the frequency near,
The filter converts the frequency fluctuation of the input signal into an amplitude fluctuation,
An error in frequency of the input signal is detected based on the amplitude fluctuation converted by the filter. In the frequency error detection device for detecting the frequency error of the input signal,
A filter that converts frequency fluctuations of the input signal into amplitude fluctuations;
Means for counting the frequency of the input signal;
Means for controlling the characteristics of the filter so that the gain changes in the vicinity of the frequency based on the frequency of the input signal counted by the means for counting ;
A frequency error detection apparatus comprising: a detecting unit that detects an error in the frequency of the input signal based on the amplitude fluctuation converted by the filter.

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