JPS59181728A - Microwave communication device of dual frequency converting system - Google Patents

Abstract

PURPOSE:To use only one oscillator having high frequency stability, and to obtain a device which is inexpensive, adjusted easily and has high frequency stability by using a higher harmonic of a local oscillation signal as a frequency stabilizing reference microwave signal source or a voltage control oscillator. CONSTITUTION:A part of an output of a microwave voltage control oscillator 14 is mixed with a higher harmonic of (n) times from a higher harmonic output terminal 12 of the first local oscillator 10 by the second frequency mixer 13, and an automatic control intermediate frequency 1F is made. This 1F is amplified by an amplifier 15, and applied to an automatic phase controlling circuit 16. A DC portion of an output of the circuit 16 is smoothed by a loop filter of the circuit 16, applied to said oscillator 14, and its microwave local oscillation frequency is stabilized. An oscillation frequency of the oscillator 14 can be varied by switching a frequency dividing number of a programmable frequency divider by a switch 18. Accordingly, only one oscillator which is expensive and has high frequency stability is enough, and it will do to provide an inexpensive reference oscillator in an automatic controlling circuit

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radio wave communication device, and particularly to a device in which a microwave frequency oscillator is a voltage controlled oscillator.

Conventionally, among microwave communication systems, most frequency conversion systems have one local oscillator and one frequency converter. In this method, the output band is limited by the band limit of the band-pass E-wave device, which is used to cut off unnecessary signals such as local oscillator signals leaking from the frequency converter.
Broadband expansion was difficult. In order to widen the band of this microwave output, the intermediate frequency may be set high. However, intermediate frequencies are generally standardized internationally and cannot be selected freely. Therefore, in order to achieve multiple channels using this method, it is necessary to have a local oscillator, frequency converter, and bandpass P-wave device for each necessary channel, which has the disadvantage of being uneconomical and large. . Therefore, a double frequency conversion method was developed in which a fixed intermediate frequency is once converted to a higher frequency, and this frequency is used as a second intermediate frequency. According to this double frequency conversion method, only one frequency converter and one bandpass P-wave device are required for microwaves. However, in order to reduce the number of local oscillators used, it is possible to use a voltage controlled oscillator as the local oscillator and change the control voltage for each channel.
A predetermined local oscillation frequency can be obtained. in this case,
A problem arises in stabilizing the local oscillation frequency. That is, in order to stabilize frequencies that vary over a wide range, automatic phase control or automatic frequency control is usually performed. A frequency divider is usually used to automatically control the mouth wave frequency, but frequency dividers in the microwave band have a complicated configuration, are difficult to adjust, are expensive, and in some cases are expensive. has the disadvantage of narrow bandwidth. Therefore, instead of using a frequency divider in the microwave band, a microwave signal source with high frequency stability is used, and the oscillation frequency of the voltage controlled oscillator is divided into a frequency in the relatively inexpensive UHF band using a frequency converter. It is conceivable to beat down to the frequency at which the device operates. In this case, a microwave signal source with high frequency stability is required to control the voltage controlled oscillator, and the output of the crystal controlled oscillator is usually configured using a frequency multiplier. However, in order to multiply the output of a crystal controlled oscillator and obtain a high-quality microwave signal source with good C/N and no spurious signals, a large number of filters are required, which are large, complicated, and expensive. becomes.

An object of the present invention is to provide an expensive oscillator with high frequency stability by using harmonics of a local oscillation signal as a reference microwave signal source for frequency stabilization of a voltage controlled oscillator in a dual frequency conversion type microwave communication device. The number of units is 1
It is an object of the present invention to provide a dual frequency conversion type microwave communication device which is inexpensive as a whole, has easy adjustment, has high frequency stability, and operates in a wide band.

Below, one embodiment of the present invention will be explained with reference to the drawings. A part of the output from the microwave voltage controlled oscillator is mixed to create an intermediate frequency for automatic control, and this intermediate frequency is detected to automatically control the microwave voltage controlled oscillator, and the frequency of the voltage controlled oscillator is adjusted to a predetermined value. It is designed to control the frequency. That is, the first local oscillation frequency is fI
L, the first intermediate frequency is fl■F, the second intermediate frequency is f21F, N the oscillation frequency of the microwave voltage controlled oscillator is fr, and the input/output frequency is fo, then fzrF= ft
L+ htF−−°゛(1) fo = fr±fzIF
It is expressed as = fr±(fu, + flxF) −(2).

On the other hand, the automatic control frequency fc is fc===1fr-n-fo,l (where n=
1.2-)...(3).

If fc is automatically controlled to a constant value depending on fo, fr becomes a constant value depending on the input/output frequency. Therefore, by controlling fc((, fr ), fr can be controlled to a predetermined frequency.As seen from equation (3), the control range of fr is equal to or less than fIL,
By selecting an appropriate value for fIL, the maximum fH can be achieved.

It is possible to cover a range of up to

Therefore, the present invention provides a first local oscillator that outputs a local oscillation signal for frequency conversion, a voltage controlled oscillator that outputs a local oscillation signal for frequency conversion as a second local oscillator,
mixing a harmonic of the local oscillation signal output from the first local oscillator and a part of the output of the voltage controlled oscillator;
A mixer that obtains a control intermediate frequency; and a mixer that detects the intermediate frequency and uses harmonics from the first local oscillator as a reference microwave signal source for frequency stabilization of the voltage controlled oscillator to stabilize the oscillation frequency of the voltage controlled oscillator. It is equipped with a control circuit for controlling the

FIG. 1 shows an embodiment in which the present invention is applied to a dual frequency conversion type microwave transmitter. In other words, in FIG.
The baseband signal applied to is applied to the first intermediate frequency signal modulator 2 and converted into a first intermediate frequency signal.

This first intermediate frequency signal is switched between the external intermediate frequency signal applied to the first intermediate frequency signal external input terminal 3 and the IF switch 4 . This switched first intermediate frequency signal is mixed with the fundamental wave oscillation output terminal 110 local signal of the first local oscillator 10 by the first frequency mixer 5, and unnecessary by the first bandpass F-wave generator 6. waves are suppressed and become a second intermediate frequency signal. This second intermediate frequency signal is amplified at a predetermined level by an amplifier 7, and mixed by a third frequency mixer 8 with the output of a microwave voltage ttilJ control oscillator 14 used as a second local oscillator. Out of the mixed output, only the desired microwave signal is sent to the second
It is taken out by the bandpass F-wave generator 9, and the microwave output terminal 1
Obtain the signal from 7. The above configuration is almost the same as a conventional microwave transmitter.

By the way, in the present invention, a part of the output of the microwave voltage controlled oscillator 14 is mixed with n times higher harmonics from the harmonic output terminal 12 of the first local oscillator 10 in the second frequency mixer 13, and automatic Create an intermediate frequency for control.

This intermediate frequency is amplified to a required level by the amplifier 15 and applied to the automatic phase control circuit 16.The DC component of the output from the automatic phase control circuit 16 is
6 is applied to the microwave voltage controlled oscillator 14 to stabilize the microwave local oscillation frequency of the oscillator 14. The oscillation frequency of the microwave voltage controlled oscillator 14 can be changed by switching the frequency division number of the programmable frequency divider using the switch 18.

As is clear from FIG. 1, in this embodiment, only one expensive oscillator with high frequency stability is required, and only one inexpensive reference oscillator in the automatic control circuit is required, and the microwave transmission is controlled. This has the effect of configuring a machine.

FIG. 2 shows an example in which the present invention is applied to a microwave receiver. That is, in the second drawing, the input terminal 19
The microwave reception signal added to the fourth mixer 20
It is mixed with the output of the voltage controlled oscillator 14 and converted into a high frequency first intermediate frequency signal.

amplifying the output of the fourth mixer 20 by an amplifier 21;
This is mixed with the output of the first local oscillator 10 by the fifth mixer 22 to obtain a second intermediate frequency signal. This mixer 22
The output of the signal is band-limited by the band p-wave generator 23. The band-limited output is amplified to a partial level by an automatic gain control amplifier 24. The second intermediate frequency signal is applied to the external intermediate frequency output terminal 25 and becomes an intermediate frequency output. The signal is still applied to the demodulator 26, demodulated, and output from the output terminal 27 as a baseband output. In other words, the receiver operates in the same way as the transmitter, only the signal flow is reversed. The first component required for the frequency conversion section is
The second local oscillation signal is obtained by I) exactly the same structure, function, and operation as the transmitter.

Next, a specific example will be given and explained. Here, since the functions and operations are the same for both the transmitter and the receiver, the case of the transmitter will be explained. The first intermediate frequency is assumed to be 130 MHz.

This is the intermediate frequency of a standard domestic television microwave repeater.

The first local oscillator is a surface acoustic wave resonator controlled oscillator (or crystal controlled oscillator), and the oscillation frequency is set to 894 MHz, and its harmonics are set to 5,364 MHz, which is six times higher. The second intermediate frequency frequency is 894 MHz + 13
Use 1,024 MHz of 0 MH2. Also, the oscillation frequency range of the microwave voltage controlled oscillator is 5,41
0 MHz to 6.090 MHz. The microwave signal output at this time is 6,434 MHz to 7,114 MHz.
MHz, and the band is 680 MHz. The intermediate frequency for automatic phase control is 46 MHz to 726 MHz, and the leakage of the reference signal of the first local oscillator to the automatic phase control intermediate frequency signal at the input of the automatic phase control circuit is due to the band characteristics of the automatic phase control intermediate frequency amplifier. It can be easily and sufficiently small so as not to affect the operation of the automatic phase control circuit.

As explained above, the present invention utilizes harmonics from an oscillator with high frequency stability, mixes a part of the output of a microwave voltage controlled oscillator with this to obtain an intermediate frequency for control, and Since the frequency of the frequency is detected and the oscillation frequency of the voltage controlled oscillator is stably controlled, it is possible to create a microwave communication device with high frequency stability without using two or more expensive oscillators with high frequency stability. It has the effect of being able to obtain the following.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a block diagram showing a second embodiment of the present invention. 10... First local oscillator, 13... Frequency mixer, 14... Microwave voltage controlled oscillator, 16... Automatic phase control circuit - Patent applicant NEC Corporation

Claims (1)

[Claims] (1) A first local oscillator that outputs a local oscillation signal for frequency conversion, a voltage controlled oscillator that outputs a local oscillation signal for frequency conversion as a second local oscillator, and a voltage controlled oscillator that outputs a local oscillation signal for frequency conversion; a mixer for obtaining a control intermediate frequency by mixing the harmonics of the first local oscillator signal and a part of the output of the voltage controlled oscillator; 1. A dual frequency conversion type microwave communication device, comprising: a control circuit for stabilizing the oscillation frequency of the voltage controlled oscillator as a reference microwave signal source for frequency stabilization of the controlled oscillator.