JP2646879B2 - Automatic frequency control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic frequency control device used for a digital car telephone receiver or the like.

[0002]

2. Description of the Related Art FIG. 2 shows a configuration of a conventional automatic frequency control device. In FIG. 2, reference numeral 11 denotes a received signal input terminal, 12 denotes a receiver, 13 denotes a phase quantizer, 14 denotes a quantized phase output terminal, 15 denotes a frequency error detector, and 16 denotes a first error detector.
An integrator, 17 is a second integrator, 18 is a digital VCO,
19 is a frequency controller.

The operation of the automatic frequency control device configured as described above will be described below. First, a reception signal is input from the reception signal input terminal 11 to the receiver 12. The receiver 12 converts the frequency of the received signal and outputs it to the phase quantizer 13. The frequency-converted received signal is also output to the frequency controller 19. The frequency controller 19 measures the average frequency of the input signal, calculates an error from the expected average frequency, and controls the frequency conversion characteristics of the receiver 12 so as to eliminate the error. The phase quantizer 13 quantizes the phase of the received signal using the reference signal from the digital VCO 18 and outputs the result to the quantized phase output terminal 14. The quantization phase is also input to the frequency error detector 15. Frequency error detector 15
Determines whether the value of the quantization phase is delayed or advanced compared to the expected value, and outputs the advanced or delayed as 1-bit information. The first integrator 16 integrates the lead and lag, and outputs the overflow signal and the sign as 2-bit information when a certain value is reached. When the overflow signal and sign are output,
The first integrator 16 is initialized and repeats the above operation. The second integrator 17 integrates the sign when the first integrator 16 generates an overflow signal. The integration result is output as frequency division error data and input to the digital VCO 18. The digital VCO 18 controls the output frequency according to the value of the input frequency division error data, and operates so that the quantization phase matches the expected value.

As described above, even the above-described conventional automatic frequency control device can perform frequency control for frequency conversion and frequency control for phase quantization.

[0005]

However, in the above-mentioned conventional automatic frequency control apparatus, since the frequency controller 19 measures the frequency of the modulated signal on which noise is superimposed by the pulse counting method, an error occurs. There is a problem that the operation is largely unstable.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an excellent automatic frequency control device which operates stably with a simple circuit having a small error.

[0007]

According to the present invention, a third integrator and a D / A converter are provided in place of a frequency controller in a conventional automatic frequency controller to achieve the above object. It is.

[0008]

Therefore, according to the present invention, frequency division error data generated from the result of phase quantization is integrated by the third integrator, and the D / A converter is operated with this value to convert the frequency of the receiver. By controlling the characteristics, there is an effect that the effect of noise can be reduced and automatic frequency control with a small error and stable operation can be performed.

[0009]

FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, 1 is a received signal input terminal, 2 is a receiver, 3 is a phase quantizer, 4 is a quantized phase output terminal, 5 is a frequency error detector, 6 is a first integrator, and 7 is a second integration. vessel,
8 is a digital VCO, 9 is a third integrator, 10 is D / A
It is a converter.

The operation of the automatic frequency control device configured as described above will be described below. First, a reception signal is input from the reception signal input terminal 1 to the receiver 2. The receiver 2 converts the frequency of the received signal and inputs it to the phase quantizer 3. The phase quantizer 3 quantizes the phase of the received signal using the reference signal from the digital VCO 8 and outputs it to the quantized phase output terminal 4. The quantization phase is also input to the frequency error detector 5. The frequency error detector 5 determines whether the value of the quantization phase is delayed or advanced as compared with the expected value, and outputs the advanced or delayed as 1-bit information. The first integrator 6 integrates the lead and lag, and when the signal reaches a certain value, the overflow signal and the sign are compared by two.
Output as bit information. When the overflow signal and the sign are output, the first integrator 6 is initialized, and the above operation is repeated. The second integrator 7 integrates the sign when the overflow signal of the first integrator 6 occurs. The integration result is output as frequency division error data and input to the digital VCO 8. The digital VCO 8 controls the output frequency according to the value of the input frequency division error data, and operates so that the quantization phase matches the expected value. The third integrator 9 integrates the output of the second integrator 7 when the second integrator 7 performs an integrating operation. The third integrator 9 calculates the integration result as D / A
Output to converter 10. The output of the D / A converter 10 controls the frequency conversion characteristics of the receiver 2.

The output of the second integrator 7 and the digital VCO 8
And the control states of the third integrator 9 and the receiver 2 are
When the output of the second integrator 7 is positive, it means that the output frequency of the receiver 2 input to the phase quantizer 3 is high, so that the output frequency of the digital VCO 8 is increased. When the output of the third integrator 9 is positive, the output frequency of the receiver 2 is reduced. When the input frequency of the phase quantizer 3 is high, the output of the second integrator 7 increases and the digital VC
The frequency is adjusted by increasing the frequency of O8. Further, as the output of the second integrator 7 increases, the output of the third integrator 9 increases, and the input frequency to the phase quantizer 3 decreases. According to the control by the third integrator 9, the output frequency of the digital VCO 8 decreases because the output frequency of the digital VCO 8 becomes too high in the previous control of the second integrator 7. Lower. By making the time constant of the third integrator 9 larger than that of the second integrator 7, this operation is stabilized, the output of the second integrator 7 becomes zero, and the signal is received under the control of the third integrator 9. Machine 2
Is in a steady state with no frequency error. Thus, automatic frequency control is performed.

As described above, according to the above embodiment, the frequency error of the received signal can be corrected by the control of the second integrator 7 and the third integrator 9, and the noise of the received signal can be reduced by the low-pass filter characteristic of the integrator. The effect is that the influence can be reduced and frequency control with a small error and stable operation can be performed. In addition, the circuit configuration is simple, the high-frequency analog circuit and the digital logic circuit can be clearly distinguished, and there is an effect that the noise countermeasures of the radio become easy.

[0013]

As described above, according to the present invention, by providing the third integrator and the D / A converter, the influence of noise can be reduced by the low-pass filter characteristic of the integrator, and the error is small and the frequency can be stably set. There is an effect that control can be performed. In addition, the circuit configuration is simple, the high-frequency analog circuit and the digital logic circuit can be clearly distinguished, and there is an effect that the noise countermeasures of the radio become easy.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an automatic frequency control device according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a conventional automatic frequency control device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reception signal input terminal 2 receiver 3 phase quantizer 4 quantization phase output terminal 5 frequency error detector 6 first integrator 7 second integrator 8 digital VCO 9 third integrator 10 D / A converter

Claims (1)

(57) [Claims] 1. A receiver for performing frequency conversion upon receiving a received signal, a phase quantizer for quantizing the phase of the received signal,
A frequency error detector that determines whether the value of the quantization phase is delayed or advanced compared to the expected value, and integrates the overflow signal and sign when the value of the quantization phase is integrated and reaches a certain value. A first integrator for outputting the signal, a second integrator for integrating the sign when the overflow signal is output, and controlling the output frequency based on the result of the integration so that the quantization phase matches the expected value. Digital VC for controlling the phase quantizer
O, a third integrator for integrating the output of the second integrator,
An automatic frequency control device comprising a D / A converter for controlling the frequency conversion characteristics of the receiver based on the result of the integration.