JPS627982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a frequency detection device that detects a received frequency using an instantaneous frequency discriminator.

Conventionally, an instantaneous frequency discriminator (Polar Frequency Discriminator)
When detecting frequencies using a discriminator (hereinafter abbreviated as PFD), two orthogonal video signals are obtained from the output of the DFD, these are displayed on the XY indicator, and the cursor is placed on the displayed video on the indicator CRT. A manual frequency detection device is used that also performs frequency measurements. However, since this conventional device performs manual frequency detection, it has the drawback that it is time-consuming and inevitably suffers from an upper-side fixed error. Furthermore, on a cathode ray tube, a display line extending in the radial direction from the center of the XY coordinate system is displayed as it is at the amplitude level of the incoming radio wave, so amplitude fluctuations appear as changes in the length of the display line, making it difficult to detect.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned conventional drawbacks, and provides an apparatus that can reduce measurement errors and detect frequencies in a short time.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 1, a high frequency signal received by an antenna 10 is supplied to a limit amplifier 11, where it is amplitude limited and amplified.
2. As is already known, PFD12 consists of four signals υ1, υ2, υ expressed by the following equations.
3, output υ4. υ1=kp/2(1-cosθ), υ2=kp/2(1+cosθ), υ3=kp/2(1-s
in θ), υ4=kp/2(1+sinθ), where k is the diode detection efficiency in the PFD, p is the received power, and θ
is angle information proportional to frequency. These four signals are supplied to the next-stage operational amplifiers 13, 14, and 15, where predetermined calculations are executed respectively.
That is, the operational amplifier 13 receives the signals υ1 and υ2.
is input and executes the operation υ2−υ1, and the signal
Output = υ2 - υ1 = kpcosθ. Similarly, the operational amplifier 14 inputs the signals υ3 and υ4 and outputs υ4−υ.
Execute the operation 3, Y=υ4−υ3=kpsinθ
Output. In addition, the operational amplifier 15 outputs signals υ3, υ
4 or input signals υ1 and υ2 and calculate (υ1
+υ2 or υ3+υ4) to obtain a signal Z = υ1 + υ2 = υ3 representing the direct detection signal level.
+υ4=kp is output. Of these signals, the output signal X of the operational amplifier 13 is supplied to an analog-to-digital converter (hereinafter abbreviated as A/D converter) 16, where it is converted into a digital quantity of a predetermined number of bits. Similarly, the output signal Y of the operational amplifier 14 is converted by the A/D converter 17 into a digital amount having a predetermined number of bits. The output signal Z of the operational amplifier 15 is branched and sent to the A/D converter 16, 1 as a control signal.
7. The A/D converters 16 and 17 derive the signals X and Y from the operational amplifiers 13 and 14 as digital amplitude information based on the sampling pulse generated from this control signal, and this information is transmitted to the next stage X/Y division circuit. 18. Further, the information in the quadrant in which these digital amplitude information X and Y exist is driven and generated by a sampling pulse based on the signal Z from the operational amplifier 15, and is derived as two judgment bits. These 2-bit determination bits relate to angle information proportional to frequency, and are sequentially converted into 2-bit codes from the first quadrant to the fourth quadrant, namely (1, 1), (0, 1), (0,
0), (1, 0), respectively A/D
It is obtained by extracting the most significant bit (MSB) from converters 16,17. Therefore, the digital information X and Y from the A/D converters 16 and 17 are applied to a division circuit 18 composed of, for example, a ROM (Read Only Memory), where digital division (Y/X) is performed. the result,
Output tangent angle information H (=Y/X=tanθ). This tangent angle information tan θ is converted into angle information θ by an inverse conversion circuit 19 configured as a table using a ROM, for example. The judgment bits (2 bits) obtained by combining this angle information θ and the sign bit for quadrant judgment of the signals X and Y are, for example,
It is added to the frequency conversion circuit 20 which is configured with a table based on ROM, and here a frequency having a certain relationship (what quadrant) is calculated from the angle information θ.

According to an embodiment of the frequency detection device according to the present invention shown in FIG. 1, an angle information conversion circuit is provided,
Since the signal X/Y is calculated by the division circuit 18, the amplitude information of each signal X, Y is standardized, and there is an advantage that fluctuations in the amplitude information do not appear in subsequent circuits.

In addition, since the present invention uses signal Z to A/D convert signals X and Y, there is no need to provide a separate detection circuit, and the configuration is simple and the frequency of incoming radio waves can be changed instantaneously and automatically only when radio waves arrive. Since there is no need for an operator to operate a scale on a cathode ray tube like in the past, accurate frequency detection is possible in a short period of time.

FIG. 2 explains another embodiment of the present invention, and in particular, in FIG. 2, the parts common to FIG. 1, that is, from the antenna 10 shown in FIG. The systems up to this point are omitted because they have the same structure. Components that are the same as those in FIG. 1 are given the same reference numerals and detailed explanations will be omitted. Therefore, the digital output signal X=pcosθ of the A/D converter 16 is applied to the absolute value calculator 21, where absolute value calculation is performed, and the signal X1=|pcosθ
becomes ｜. Similarly, the digital output signal Y=psinθ of the A/D converter 17 is converted into the signal Y1=|psinθ| by the absolute value calculator 22. Absolute value calculator 2
The output signals X1 and Y1 of 1 and 22 are supplied to corresponding logarithmic transformers 23 and 24, respectively, where logarithmic transformation is performed. This can be done, for example, by using a fixed table composed of ROM in the logarithmic converters 23 and 24, and using PROM (Programme Read Only).
Based on the control of the output signal X1,
This is done by reading the logarithmic value corresponding to Y1 from the table. Output signal X2 of logarithmic converter 23=logX1 and output signal Y2 of logarithmic converter 24=
logY1 is fed to a subtractor 25, where Y2−X2
The following calculation is executed. Therefore, the signal H=logtan θ is obtained at the output of the subtracter 25. This subtractor 2
For example, the output signal H=logtan θ of No. 5 is converted into angle information θ by an inverse converter 26 using a conversion table configured in a ROM under the control of a PROM. This angle information θ is further converted into a frequency proportional to the angle by a frequency converter 27 composed of a ROM as described above.

The angle information θ output from the inverse converter 26
includes the frequency distortion of the PFD 12.
Therefore, in this embodiment, when converting angle information θ to frequency, a correction table created by taking into account the frequency distortion unique to the PFD measured in advance is used in the frequency converter to perform frequency conversion. is going on. Also, the sign bit (1
Quadrant determination of the signals X and Y is performed using determination bits (2 bits) similar to those shown in FIG. Determining the frequency.

According to other embodiments of the invention described above, the A/D
The converted digital signal is converted into a conversion table 23,
The signals obtained by logarithmically converting the signals using the subtracter 24 and subtracting the logarithmically converted signals using the subtracter 25 become independent of received level fluctuations and level fluctuations due to frequency characteristics, allowing reliable measurement. It is. In addition, in the device shown in FIG. 1, the signal after A/D conversion by the A/D converters 16 and 17 is directly divided by the division circuit 18, so there is a problem with accuracy, especially when the value of the denominator X is small. In order to improve the precision of , it is necessary to increase the number of bits of the quotient generated in the process of executing the division operation.
Therefore, the number of operation bits becomes enormous, and the device becomes extremely complex. Furthermore, limiting the number of bits directly increases the frequency calculation error. In this regard, in the device shown in FIG. 2, the division circuit is composed of conversion tables 23 and 24 and the subtraction circuit 25, so the number of operation bits can be reduced, and as a result, the device can be simplified and costs can be reduced. It is possible to reduce measurement errors.

Also, when converting angle information θ to frequency,
Since the frequency distortion inherent to the PFD can be corrected, the frequency error inherent to the PFD can be corrected, allowing for more accurate frequency measurement.

As described above, according to the present invention, it is possible to perform high-accuracy frequency measurement, which is independent of received signal level fluctuations and level fluctuations due to gain errors within the frequency band, and in addition, it is possible to simplify the device and reduce measurement errors. A frequency detection device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the frequency detecting device according to the present invention, and FIG. 2 is a block diagram showing the main configuration of another embodiment of the frequency detecting device according to the present invention. 10... Antenna, 12... Instantaneous frequency discriminator (PFD), 13-15... Operational amplifier, 16,1
7...Analog-digital converter, 21, 22
... Absolute value calculator, 23, 24 ... Logarithmic converter,
25...Subtractor, 26...Inverse converter, 27...Frequency converter.

Claims (1)

[Claims] 1. an instantaneous frequency discriminator that discriminates the frequency of a received input signal from an antenna; an arithmetic circuit that introduces the output of this instantaneous frequency discriminator and derives an angular sine signal and cosine signal corresponding to the received input signal frequency; a derivation circuit for deriving a signal representing the detected signal level from the output of the instantaneous frequency discriminator; and first and second analog converters for digitally converting each output signal of the arithmetic circuit using the output signal of the derivation circuit. Digital converter and this analog
an angle information conversion circuit that introduces the output of a digital converter and derives angle information corresponding to a frequency based on tangent information obtained from sine information and cosine information;
deriving means for deriving the received input signal frequency from which code information of the sine signal and cosine signal output from the first and second analog-to-digital converters is supplied together with the angle information of the angle information conversion circuit; Frequency detection device.