JPH0818404A - Automatic frequency control system for millimeter wave band fm transmitter-receiver - Google Patents

Abstract

PURPOSE:To provide the AFC of a transmission frequency in a millimeter wave band transmitter-receiver in a small size at a low cost by using the leakage component of transmission signals for which a part of the transmission signals leaks in an antenna multicoupler and is frequency converted. CONSTITUTION:The transmission signals generated in a frequency modulator 2 are passed through the antenna multicoupler 3 and supplied to an antenna 4 and reception signals from the antenna 4 are filtered by a reception filter 5, converted to an IF frequency by a local oscillator 6 and a frequency converter 7 and amplified in an IF amplifier 8. In this case, the leakage of the transmission signals from the antenna multicoupler 3 is normally inputted to the reception filter 5 and the signals of the leakage are utilized for the AFC by using the circuits of a reception system. The transmission signals are frequency converted by the local oscillator 6 and the frequency converter 7 and the error of the transmission frequency is detected in a frequency discrimination device 10. Since the ones of the reception system are used without providing the local oscillator and the frequency converter in a transmission system, miniaturization is performed and a cost is lowered compared to conventional constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automatic frequency control (AFC: AUTOMATIC FREQUE) of a transmission frequency of a millimeter waveband transceiver.
NCY CONTROL) method improvement.

[0002]

2. Description of the Related Art FIG. 2 is a conceptual diagram of the AFC method. Figure 2
In, the output of the self-excited oscillator 21 having the frequency control input terminal is input to the frequency discriminator 22 and the frequency error voltage is output. The error voltage is applied to the frequency control terminal of the self-excited oscillator 21 through the low pass filter 23 to control the oscillation frequency.

FIG. 3 is a block diagram of a conventional circuit using such an AFC circuit for stabilizing the transmission frequency of a transceiver.
Generally, when the transmission / reception frequency changes from the microwave band to the millimeter wave band, a self-excited oscillator is often used as an oscillator. However, when the transmission modulation method is FM (frequency modulation), the frequency is changed by the oscillator. Since the variable capacitance diode or the like is added, the Q of the oscillator is lowered and the stability of the oscillation frequency is deteriorated. Therefore, a circuit for stabilizing the frequency is added.

FIG. 3 shows a transmission system of a millimeter-wave band transceiver, in which the FM modulator 2 generates a transmission frequency.
The FM modulator 2 is a voltage controlled oscillator (VCO: VO
LTAGE CONTROLLED OCSILLATOR), and the FM modulated wave is output by the modulation signal input and becomes the transmitted wave. In order to stabilize the transmission frequency, a part of the output of the FM modulator 2 is frequency-converted by the local oscillator 12 and the frequency converter 13 and input to the frequency discriminator 10. In the frequency discriminator 10, a frequency error signal is generated, and the low pass filter 1
1 is added to the modulated signal by the adder 1 and is input to the FM modulator 2 to correct the frequency. In such a system, the transmission frequency accuracy is equal to the sum of the frequency accuracy of the local oscillator 12 and the frequency discriminator 10. here,
Since the local oscillator 12 is an oscillation of a fixed frequency, a resonator having a high Q can be used, so that the frequency stability is high, and the frequency discriminator 10 has a frequency lower than the transmission frequency. It can be regarded as high when compared with.

[0005]

However, in the millimeter-wave band transceiver, the local oscillator 12, the frequency converter 13 and the like are expensive, and there is a drawback in that the external dimensions increase as the circuit becomes complicated.

An object of the present invention is to provide an automatic frequency control system which realizes an AFC of a transmission frequency in a millimeter wave band transceiver at low cost and in a small size.

[0007]

An automatic frequency control system for a millimeter-wave band transceiver according to the present invention includes an FM modulator which generates a millimeter-wave band transmission carrier and outputs a transmission signal FM-modulated by an input modulation signal. , An antenna duplexer that outputs the transmission signal input from one terminal to the antenna and outputs a reception signal from the antenna from the other terminal, and is output from the other terminal of the antenna duplexer A reception filter that selectively outputs a signal in a predetermined band from the reception signal, a frequency converter that converts the output from the reception filter into an intermediate frequency signal by a local oscillation frequency signal, and a part of the transmission signal is the antenna duplexer And a bandpass filter for extracting the leakage component of the transmission signal that has been frequency-converted and has been frequency-converted from the output of the frequency converter, and the output of the bandpass filter after frequency discrimination. A frequency discriminator that detects a frequency error of a carrier wave, and a low pass filter that removes a transmission modulation signal included in a detection signal of the frequency discriminator and extracts a DC error voltage are output from the low pass filter. It is characterized in that the DC error voltage is added to the input modulation signal of the FM modulator to suppress the fluctuation of the transmission carrier frequency of the FM modulator.

[0008]

1 is a block diagram showing an embodiment of the present invention.
In the figure, 1 is an adder, 2 is an FM modulator, 3 is an antenna duplexer, 4 is an antenna, 5 is a reception filter, 6 is a local oscillator, 7 is a frequency converter, 8 is an IF amplifier, 9 is a bandpass filter, Reference numeral 10 is a frequency discriminator, and 11 is a low-pass filter.

The transmission signal generated by the FM modulator 2 is supplied to the antenna 4 via the antenna duplexer 3, and the reception signal from the antenna 4 is filtered by the reception filter 5, and the local oscillator 6 and the frequency converter. Converted to IF frequency by 7 and I
It is amplified by the F amplifier 8. Here, normally, the leakage of the transmission signal from the antenna duplexer 3 is input to the reception filter 5, but the leakage signal is used for AFC using a circuit of the reception system. That is, the transmission signal is frequency-converted by the local oscillator 6 and the frequency converter 7 by setting the attenuation amount of the transmission signal of the reception filter 5 to such an extent that the reception system is not saturated with the transmission signal. Only the signal near the transmission frequency is taken out from the output of the frequency converter 7 by the bandpass filter 9, and the error of the transmission frequency is detected by the frequency discriminator 10. Since this detection signal contains the transmission modulation wave, the low-pass filter 11 extracts the DC signal component and adds it to the adder 1 of the FM modulation input of the transmission system.

As described above, according to the AFC method of the present invention,
Since the receiving system is used without providing a local oscillator and a frequency converter in the transmitting system, it is smaller and cheaper than the conventional configuration.

[0011]

As described above, according to the present invention, the AFC for stabilizing the transmission frequency of the transceiver can be constructed in a small size and at a low cost.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram of AFC.

FIG. 3 is a diagram illustrating a configuration example of a conventional AFC circuit.

[Explanation of symbols]

 1 adder 2 FM modulator 3 antenna duplexer 4 antenna 5 reception filter 6 local oscillator 7 frequency converter 8 IF amplifier 9 bandpass filter 10 frequency discriminator 11 low pass filter 12 local oscillator 13 frequency converter 21 oscillator 22 frequency discriminator 23 Low pass filter

Claims (1)

[Claims] 1. An FM modulator that generates a millimeter-wave band transmission carrier and outputs a transmission signal that is FM-modulated by an input modulation signal, and outputs the transmission signal input from one terminal to an antenna. An antenna duplexer that outputs a reception signal from the antenna from the other terminal, a reception filter that selectively outputs a signal in a predetermined band from the reception signal output from the other terminal of the antenna duplexer, and the reception filter A frequency converter for converting the output from a local oscillation frequency signal into an intermediate frequency signal, and a part of the transmission signal leaking in the antenna duplexer and a leakage component of the transmission signal whose frequency is converted by the frequency converter. A bandpass filter extracted from the output, a frequency discriminator for discriminating the output of the bandpass filter to detect a frequency error of the transmission carrier, and a frequency discriminator With a low-pass filter that removes the transmission modulation signal included in the detection signal of and extracts the DC error voltage,
The DC error voltage output from the low pass filter is set to the F
The FM by adding to the input modulation signal of the M modulator
An automatic frequency control system for a millimeter-wave band FM transmitter / receiver configured to suppress fluctuations in the transmission carrier frequency of a modulator.