JPS58186249A - Automatic frequency controlling system - Google Patents

Abstract

PURPOSE:To use an oscillator with a fixed frequency and high Q for a local oscillator at the receiver side, by transmitting the frequency error detected at the receiver to the transmission side, and changing the carrier frequency at the transmission side. CONSTITUTION:A modulator 4 of a transmitter 1 modulates a signal at a modulation signal input terminal 3, mixes the result with an output of a local oscillator 6 at a mixer 5, and a radio wave is transmitted from an antenna 7. The waves are received at an antenna 8 of a receiver 2, mixed with an output of a local oscillator 22 at a mixer 9, the output passes through a band pass filter 10, amplified at an intermediate frequency amplifier 11, and applied with FM modulation at a frequency discriminator 12 and a demodulated output is transmitted from an output terminal 13. Further, a frequency counter 24 measures the error between an intermediate frequency carrier wave obtained from the amplifier 11 and the normal intermediate frequency, this error is transmitted to the opposite transmission line to control the carrier frequency at the transmission side.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a wireless communication system using a digital FM modulation system. %K, relates to an automatic [1 bush control method] that suppresses deterioration of transmission quality due to radio-like frequency drift.

[Description of conventional technology]

The oscillation frequencies of the transformer and station S oscillator, which are the components of the radio, vary depending on changes in temperature f and changes in power supply voltage. For this reason, a relationship Kjl wave number difference between the carrier frequency of the transmitted modulated wave and the tuning frequency of the receiver occurs, causing distortion in the detected waveform and deterioration of the error rate characteristic. In order to prevent such deterioration of transmission quality, automatic frequency control (AFO) has been considered, which detects frequency errors and compensates for them by feeding them back.

FIG. 1 shows a configuration diagram of a conventional example. This is the known inter-receiver s
'#5 This is an application of the automatic frequency control method for the oscillation frequency to a digital FM signal transmission system.

In FIG. 1, ltj is a transmitter and 2 is a receiver.

3 is a modulation signal input terminal, 4 is a modulator, 5 is a FiZ mixer, 6 is a
ij is a local oscillator, and 7 is an antenna. 8Fi antenna, 11 mixer, 10Fi band passing P-wave device, 11 is intermediate frequency amplifier, and the branch is frequency discriminator. 13 is a demodulation output terminal. 14 is a low-pass P wave device (LP?), 15Fi
This oscillator 15, which is a voltage controlled oscillator (VCO), operates as a local oscillator of the receiver 2.

In this configuration, modulator 4, local oscillator 6 and excavator 1
50 Frequency Doria) Due to K, the carrier frequency of the human input signal of the frequency discriminator 12 deviates from the regular intermediate frequency. Frequency discriminator 12#'i outputs a voltage signal proportional to the difference between the instantaneous frequency of the human input signal and the regular intermediate frequency to the output terminal 13, and the variable signal component (AC component) included in this output is When it is removed by the low-pass raw 14, a DC voltage proportional to the carrier m-wave number difference can be obtained.

When this DC voltage is applied to the voltage controlled oscillator 15 to change its oscillation frequency t-, the carrier frequency of the frequency detector input signal also changes accordingly. In this way, a feedback loop is formed, and the carrier frequency error can be reduced to almost zero.

However, in this configuration, the configuration of the receiver becomes complicated and a voltage controlled oscillator with relatively low q is used as one local oscillator, so the selectivity f% and desensitization characteristics of the receiver deteriorate. There was a drawback that there was a lot of noise.

[Purpose of the invention]

The present invention does not deteriorate the selectivity characteristics and desensitization characteristics of the receiver, has a simple configuration, and is digital? M
The purpose of this invention is to provide an automatic frequency control system suitable for one-way systems.

[Key points of the invention]

In the present invention, the receiver local oscillator has a fixed frequency Q
Using an oscillator with a high frequency, the difference in wave number detected by the receiver is transmitted to the transmitting side, and by changing the transmitting wave w@@ wave number of the modulator on the transmitting side, the receiver's detector manually adjusts the carrier wave frequency of each signal. The feature is to suppress errors.

[Explanation based on examples]

FIG. 2 is a block diagram of the main parts of the apparatus according to the embodiment of the present invention.

A signal from a modulated signal input terminal 3 of one transmitter installed in the wireless communication device A is modulated by a modulator 4, mixed with the output of a local oscillator 6 by a mixer 5, and a radio wave is transmitted from an antenna 7. The receiver 2 of the wireless communication device B receives this electric power using the antenna 8.
It is received and mixed with the output of the local oscillator 22 by the mixer 9, and the output is passed through the band-pass P wave 510, amplified by the intermediate frequency amplifier 11, demodulated by the frequency discriminator 12, and output from the demodulation output terminal 13. Send demodulated output.

Here, the oscillation frequency of the local S oscillator 21 is fixed. 1 frequency counter 24 which branches the output signal of the intermediate frequency amplifier ll of the receiver 2 and connects it to the frequency counter 24;
Fi, error (Δf) of the intermediate frequency carrier obtained at the output of the intermediate frequency amplifier 11 from the normal Nakaguan Liu wave number (f)
Measure. Information on this error (Δf) is transmitted to the transmitting circuit 25
The signal is transmitted from the transmitter 1' of the wireless communication device B to the receiver 2' of the wireless communication device A through the transmission path in the opposite direction, and is transmitted by the receiving circuit 26 to Ij:! believe The output of this receiving circuit is given to a digital arithmetic circuit n. The output of this arithmetic circuit n is applied to the g# adjuster 4 through the terminal. Digital calculation (b)
This circuit includes a 27Fi Micro 70 processor, and can be shared with automatic frequency control and other controls in a wireless communication device that are not directly related to Fi.

Information on the error passing through the transmission path in the opposite direction is obtained by modulating the in-service control signal of the circuit in the opposite direction in the preferred embodiment.

The transmitter l' and the receiver 2' are also provided with circuits for transmission and reception and circuits for automatic frequency control similar to the above configuration, but these are omitted in FIG. 2 because they would complicate the drawing.

In such devices, a frequency counter measures the error (Δf) of the intermediate frequency carrier intermittently at predetermined shoulders. The information of this figure (Δf) is added to the digital arithmetic circuit 27, and this digital arithmetic circuit n calculates the amount of compensation based on the error 1fl.The signal on this compensation line is given to the modulator 4 from between the terminals. , the carrier frequency of the output signal of the modulator 4 operates to exactly cancel out the above error (Δf).

Next, modulation '64 will be explained in detail.

5 is an example of the configuration of the Vi modulator 4. The digital control signal applied to the terminal 28 is converted into an analog signal by the DA converter 31, and is applied to one analog adder blade together with the signal arriving at the input terminal 3.

This addition output is f1111i1 of the voltage controlled oscillator 33.
i11 is given to human power, and its oscillation output is output from each terminal.
The signal is sent out as a signal output and input to the mixer 5.

According to this construction, the voltage controlled oscillator 3
Since the output frequency can be shifted, an automatic frequency control loop as explained in FIG. 2 can be created.

FIG. 4 is a diagram showing an example of the configuration of a transformer 4 configured as a digital system. The signal at the modulation signal input terminal 3 is applied to a waveform generation circuit 42 . This waveform generation circuit 42 includes a microprocessor and generates instantaneous frequency shift data of a digital FM modulated wave in response to an input digital signal. This output data is applied to the digital adder circuit 43 along with data corresponding to the error (Δf) applied between the terminals. The addition output of the digital addition circuit corresponds to the output of the addition circuit 32 in the circuit shown in FIG. 3 described above.

The addition output of the digital addition circuit is based on the internal clock (
Data is integrated every time τ), and the variable N['0 is obtained and outputted. This output is added to the complex envelope generating circuit 47, and an analog cosine signal and an analog sine signal corresponding to this instantaneous phase data are generated from the cosine circuit 47 and the sine circuit 47, respectively. This output signal Vi
The signal is applied to the orthogonal modulation circuit 48.

A sine wave is applied to the auto-alternating modulation circuit 48 from an oscillator 49, and the analog cosine signal is applied to this sine wave by the analog cosine signal in the MIKI V50, and the sine wave total phase shifter 51 applies a 90[shift] to the sine wave. The output signal 17 is modified by the analog sine signal at 2x 52. The outputs of both mixers and 52 are added at addition 053 and sent out from output terminal 34.

According to the circuit shown in FIG. 4, oscillation! A 7M digital modulated wave corresponding to the data applied to the terminal 3 is obtained by using a carrier wave having the output frequency of 49 shifted by Δf according to the data applied to the terminal 28 as a carrier wave. This circuit is variable
Since the instantaneous phase of the four waves is calculated by digital processing,
The modulation index is accurate and deterministic. Additionally, no adjustments are required during manufacturing and maintenance. The circuit of FIG. 4 is suitable for integrated circuit implementation.

The "error information" referred to in the claims is not limited to the error Δf of one receiving intermediate frequency from the reference value as shown in the above embodiment, and the value measured by the station wave number counter, but also the carrier frequency at the receiving intermediate frequency stage. Any information that includes the error from the reference frequency may be used. For example, the calculation of the -difference may be performed by the transmitting device (device A in the example shown in FIG. 2).

This error information can also be transmitted as an analog signal.

In addition to transmitting this error information by modulating the in-service control signal on a transmission line in one opposite direction as shown in the above example, any other transmission method may be used.

In addition, when transmitting error information on the transmission path in the opposite direction, inquiries about this repeatedly transmitted signal in repeated transmission and reception @ are performed so that the error information is transmitted correctly even when the line quality deteriorates. It is good to spend money.

[Explanation of effects]

As explained above, according to the present invention, fixed frequency oscillation S sound can be used for the local oscillator of the receiver.
The Q of the oscillator can be increased, and the selectivity characteristics and desensitization characteristics can be improved. Thereby, reception noise can be greatly reduced.

Furthermore, the method of the present invention is suitable for a digital system, and can be integrated into an integrated circuit to make the device smaller and more stable. As a result, complicated and man-hour-intensive adjustments related to automatic frequency control during manufacturing and maintenance can be performed in a cylindrical manner.

[Brief Description of the Drawings] Fig. 1 is a schematic diagram of a conventional system. Figure 2 is a configuration diagram of the embodiment system of the present invention. In addition, in order to avoid complicating the drawing, FIG. 2 shows the configuration for only one transmission direction. FIG. S is a diagram showing an example of a configuration of a modulator using an analog system. FIG. 4 is a diagram showing an example of a configuration of a modulator using a digital system. Patent applicant: Nippon Telegraph and Telephone Public Corporation - Agent: Patent attorney Naotaka Ide', No. 112
I Tail 2 figure

Claims (3)

[Claims] (1) In the automatic frequency control system of two wireless communication devices Q that mutually communicate digital frequency modulated signals, at least one device K of the wireless communication devices is based on the reference frequency of the carrier wave frequency in the intermediate frequency stage of the received signal. and means for transmitting information on this error to the other wireless communication device, further comprising means for receiving and demodulating the information sound of the error in the other wireless communication device. The transmission (I! signal modulator) of the other wireless communication device inputs the error information obtained from the reception and demodulation means together with the transmission signal, and outputs the transmission signal by an amount corresponding to the error information. An automatic frequency control method that is configured to change the carrier wave frequency. (2) The means for transmitting all the error information is configured to transmit the error information as a digital signal, and calculates the error information from the means for receiving and demodulating the error signal to the transmitting signal modulator. Claims comprising circuit means including a microprocessor for processing v! A@ (Automatic frequency control method described in Section 11. (3) A waveform generation circuit in which the transmission signal modulator outputs instantaneous frequency shift data of a modified sea bream wave corresponding to a digital signal given from the transmission signal human input, and a circuit including the output of this waveform generation circuit and a miter 9 processor. a digital addition circuit that adds up the error O information given from the means; an integration circuit that integrates the output of this addition circuit at a predetermined period; and a cosine signal and a sine signal t according to the output of this integration circuit.
A complex envelope generation circuit that outputs an analog signal, and jIil#I as the output 1r complex envelope input of this circuit.
The automatic frequency control system according to claim (2), comprising a modulated wave cross-modulation circuit that generates an L number modulated wave.