JPH02246565A - Automatic frequency controller - Google Patents

Abstract

PURPOSE:To perform automatic frequency control without requiring a reference pilot signal by multiplying by (n) the frequency of a reception signal, which is subjected to digital modulation in accordance with the pattern and the form of a modulating signal. CONSTITUTION:An input terminal 50 is the input terminal of an automatic frequency controller 1, and for example, an n-phase PSK modulated signal ((n) is an integer >=2) is received by this terminal. When the reception signal subjected to digital modulation is received, this signal has the frequency multiplied by (n) in a frequency multiplier 9. The n-multiplied signal is inputted to a frequency discriminator 10, and control information to control the frequency of a local oscillator is outputted based on the output signal of this discriminator 10. Thus, the automatic frequency control is performed without requiring the pilot signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic frequency control (AFCI) device, particularly an automatic frequency control device advantageously applied to communication devices.

(Prior art) As a conventional technology of an automatic frequency control device, for example, "Introduction to Maritime Satellite Communication" by Toshio Sato, published by Institute of Electronics and Communication Engineers, Vol. 100-
On page 103, there is described a device that detects a pilot signal that is being sent in order to automatically control level fluctuations and frequency shifts, and performs automatic frequency control using this signal as a reference. Additionally, pages 356-361 of "Microwave Communication Engineering" published by the Telecommunications Association of Japan describes a well-known automatic frequency control device that discriminates the frequency of an intermediate frequency signal and returns it to a local oscillator. .

(Problems to be Solved by the Invention) However, in the conventional technology that uses a pilot signal as a reference signal, in addition to an information signal obtained by modulating a carrier wave, it is necessary to transmit a pilot signal shifted by a certain frequency from the carrier wave. Furthermore, the receiver side must also receive both the pilot signal and the information signal, which has the drawback of complicating the system configuration and lowering its economic efficiency.

In addition, in the conventional technology that performs frequency discrimination on an intermediate frequency signal and feeds it back to a local oscillator, a digital signal containing a DC component is used to generate a
ing) modulation and 5K (Maxisus 5hift)
When applied to a communication device that performs Keyingl, etc., the spectrum will be biased due to the pattern of the modulated signal. For this reason, it has been practically difficult to apply it to communication devices that handle such signals.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks of the prior art, and to provide an automatic frequency control device that does not require a pilot signal and is applicable to PSK modulation, MSK modulation, and the like.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides an automatic frequency control device that receives a digitally modulated reception signal and controls the frequency of a local oscillator based on this signal. A frequency multiplier for frequency-multiplying a signal; and a control means for inputting the frequency-multiplied output signal from the frequency discriminator to a frequency discriminator and outputting control information for controlling the frequency of the local oscillator using the frequency discriminator output signal. have

According to the present invention, there is also a frequency dividing means for dividing the frequency of the output signal frequency-multiplied by the 1-frequency multiplication means, and the control means controls the frequency of the local oscillator by a signal obtained by frequency-discriminating the output signal frequency-divided by 1. control information may be output.

According to the present invention, the present invention further includes a storage means in which the control signal output from the control means is stored and updated at a predetermined timing, and the frequency of the local oscillator may be controlled by the control information stored in the storage means. Actually.

(Function) According to the present invention, when a digitally modulated reception signal is received, this reception signal is frequency-multiplied by the frequency multiplier. The frequency-multiplied signal is then input to a frequency discriminator, and control information for controlling the frequency of the local oscillator is output based on the output signal of the discriminator.

According to the present invention, the received signal frequency-multiplied by the 1-frequency multiplier is frequency-divided by the 1-frequency divider. The frequency-divided signal is then input to a frequency discriminator, and control information for controlling the frequency of the local oscillator is output based on the output signal of the discriminator.

According to the present invention, the control information output from the frequency discrimination means is further stored in the storage means at a predetermined timing. Then, the frequency of the local oscillator is controlled according to the control information stored in the storage means.

(Example) Next, an example of an automatic frequency control device according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a functional block diagram of one embodiment of an automatic frequency control device according to the present invention is shown. The automatic frequency control device 1 in this embodiment is disposed in a transmitting section or a receiving section of a communication device, and automatically controls the frequency of a transmitting or receiving local oscillator of this communication device based on a digitally modulated received signal. The 0 frequency control device l, which is a device for performing this, includes a mixer 3, an intermediate frequency amplifier 6. demodulator 7,
It is composed of a frequency multiplier 9, a frequency discriminator tOi5, and a variable frequency oscillator 12.

The input terminal 50 is an input terminal of the automatic frequency control device fl, and receives, for example, an n-phase PSK modulated signal (n is an integer of 2 or more). The terminal 50 is connected to the first input terminal 2 of the MIFSA 3. The second input terminal 5 of the mixer 3 is connected to the output terminal 13 of the variable frequency oscillator 12 via a signal line 150, and is a frequency conversion circuit that extracts an intermediate frequency signal of the signals inputted from these input terminals. The output terminal 4 of the mixer 3 is connected to the input side of an intermediate frequency amplifier 6, to which an intermediate frequency signal is sent.

The amplifier 6 is an amplification circuit that amplifies the input signal to a predetermined power. The amplifier 6 has a demodulator 7j1 on its output side.
5 and frequency multiplier 9, and sends the power amplified signal Sl to these. The demodulator 7 is a circuit that demodulates the received signal SL into a digital signal before modulation.

That is, when the demodulator 7 receives the transmitted signal St that has been subjected to n-phase PSK modulation, the transmitted received signal is demodulated to the original digital signal and sent to the output terminal 60.

The frequency multiplier 9 is a circuit that frequency-multiplies the received signal St by a factor of 0 equal to the number of modulation phases n (n is an integer of 2 or more). Thereby, the frequency multiplier 9 can send the multiplied output signal S2, in which the modulation component of the signal Sl has disappeared, to the frequency discriminator lO connected to the signal output side.

The frequency discriminator 10 detects the amount of deviation of the input frequency. Therefore, detecting the frequency of the intermediate frequency is detecting the difference between the received signal frequency and the frequency of one local oscillator. The output side of the discriminator 10 is a signal line 110
is connected to the control input terminal U of the variable frequency oscillator 12 via.

The variable frequency oscillator 12 variably controls the output frequency output to the mixer 3 based on the control information input from the 1-frequency discriminator l port.

An n-phase PSK modulated signal 100 is input to the input terminal 2 of the mixer 3 via the input terminal 50 . Mixer 3 receives modulated signal 1
00 and the output signal 15G from the variable frequency oscillator 12, it is converted into an intermediate frequency signal 102. This signal 102 is sent to intermediate frequency amplifier 6. When the amplifier 6 receives the signal 102, the amplifier 6 amplifies the power of the signal 102 and outputs it as a signal Sl. The signal Sl is
The signal is received by the demodulator 7 and outputted from the output terminal 60 after demodulation, and is also sent to the frequency multiplier 9.

The signal S1 can be expressed, for example, as shown in equation 11).

5l=Asin (IJL÷φ(t)), , , ,
, (1) However, +(tl(2x/nlXm,
m=1-n This signal Sl is input to the frequency multiplier 9, and when this frequency is multiplied by n, the modulation component φ (11 is 2
It becomes an integer multiple of π and disappears. Therefore, the signal S2 output from the multiplier 9 can be expressed as shown in equation (2), for example.

S2= Bs1n (nωtl, , , ,
, , , , +21 This multiplied output signal S2
is input to a frequency discriminator lO with nω as the center frequency, and the frequency error is detected by this discriminator 10.

The frequency error information 110 detected by the discriminator lO is the variable frequency oscillator! 2 control terminals! As a result, the frequency of the output signal 50 from the oscillator 12 is automatically controlled.

FIG. 2 shows an automatic frequency 1liIIflI device 8, which is another embodiment of the automatic frequency control device. As shown in the figure, a frequency divider 18 may be inserted between the frequency multiplier 9 and the frequency discriminator lO.
When a signal 52 is provided, the signal 52 input thereto is frequency-divided and sent to the frequency discriminator 10 as a signal S3. The frequency discriminator l port of the automatic frequency control device 8 receives this signal S.
By having a center frequency equal to 3, it is possible to detect a frequency error and apply automatic frequency control as in the previous embodiment.

Further, as shown in the figure, a control signal 110 from the discriminator lO is connected between the frequency discriminator 10 and the variable frequency oscillator 12.
may be inserted at a predetermined timing and the memory contents may be updated. In this way, the memory circuit 2
When 0 is provided, the frequency of the oscillator 12 is controlled by the control information stored in this circuit 20. The update timing of the memory contents is determined by the automatic frequency control device 8, for example.
This is done by control signals generated by a communication device including the

In the embodiment shown in FIG. 2, the one-minute cycle 1815 and the memory circuit 20 are provided, but of course only one of them may be provided.

Further, in these embodiments, the frequency control when a modulated signal is received from the input terminal 50 in the n-phase PS has been described, but the present invention is not particularly limited to such a signal. When a modulation signal is input, the phase changes by ±π/2 radians for each modulation time slot, so it is sufficient to multiply the signal by 4.

(Effects of the Invention) As described above, according to the present invention, a digitally modulated received signal is multiplied by n depending on the pattern and shape of the modulated signal. Thereby, automatic frequency control can be performed without being affected by the bias of the spectrum of the input signal and without requiring a pilot signal as a reference. Therefore, the configuration of the automatic frequency control device becomes simple and it becomes possible to effectively utilize frequency resources.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the automatic frequency control device according to the present invention, and FIG. 2 is a block diagram showing another embodiment of the automatic frequency control device according to the present invention. Of, of! Automatic frequency control device Mixer Intermediate frequency amplifier Demodulator Frequency multiplier Frequency discriminator Variable frequency oscillator Period division storage circuit Patent applicant Oki Electric Industry Co., Ltd. Representative Person number Takao Maruyama Takao Example of automatic frequency control device Fig. 1 Automatic Another embodiment of the frequency control device Fig. 2

Claims (1)

[Claims] 1. An automatic frequency control device that receives a digitally modulated received signal or a received intermediate frequency signal and controls the frequency of a local oscillator based on the signal, the device comprising: a frequency multiplier for frequency-multiplying an intermediate frequency signal; an output signal frequency-multiplied by the frequency multiplier is inputted to a frequency discriminator, and control information for controlling the frequency of the local oscillator is outputted by the frequency discriminator output signal. An automatic frequency control device comprising a control means. 2. The apparatus according to claim 1, further comprising frequency dividing means for dividing the frequency of the output signal frequency-multiplied by the frequency multiplication means, and wherein the control means divides the frequency of the frequency-multiplied output signal by the frequency-multiplying means. An automatic frequency control device characterized in that the automatic frequency control device outputs control information for controlling the frequency of the local oscillator. 3. The device according to claim 1 or 2, further comprising storage means for storing and updating the control information at a predetermined timing, and controlling the local oscillator according to the control information stored in the storage means. An automatic frequency control device characterized in that frequency is controlled.