JPS6161564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microwave band frequency multiplier circuit, and more particularly to a frequency multiplier circuit for a signal generator used in a microwave band transmitter or the like.

FIG. 1 is a block connection diagram showing an example of a conventional circuit, in which 1 is a first intermediate frequency amplifier, 2 is a first
Mixer (frequency converter), 3 is a second intermediate frequency filter, 4 is a second mixer, 5 is a transmission frequency band filter, 6 is a transmission frequency amplifier, 7 is a diode switch, 8 is a first local oscillator, 9 is a second A local oscillator, 10 is a fault detection circuit, and 11 is an input terminal for a reference frequency signal. If the frequency of the signal input from the terminal 11 is f _S , the output frequency of the first intermediate frequency amplifier 1 is f ₁ , and the output frequency of the first local oscillator 8 is f _C , then the output frequency f ₀ of the transmission frequency amplifier 6 is, for example, f ₀ = f ₁ + f _C + mnf _S (1). Here, both m and n are arbitrary positive integers, and it is easy to change m or n or m and n and change f ₀ by adjusting the second local oscillator 9. It is often used in transmission frequency converters for satellite communications, etc.

FIG. 2 is a block connection diagram showing an example of the internal connection of the second local oscillator 9 shown in FIG. 1, in which 11 is the reference frequency signal input terminal like 11 in FIG. In the example, an L-band voltage controlled oscillator (hereinafter abbreviated as VCO), 13 a reference frequency signal amplifier, 14 a phase comparator, 15 a loop filter, 16 an out-of-sync detector, 17 an L-band amplifier, and 18 a frequency 19 is an output filter, 20 is an output terminal, and terminal 20 is a multiplier.
is connected to one input of the second mixer 4 in FIG.

A phase lock loop is formed by the circuit of VCO 12 → phase comparator 14 → loop filter 15 → VCO 12, and the oscillation frequency of VCO 12 is maintained accurately at _nfS . In other words, if the oscillation frequency of the VCO 12 deviates slightly from nf _S , an output is generated in the phase comparator 14, which is averaged by the loop filter 15.
Towards zeroing the phase difference between the output frequency f _S of the reference frequency signal amplifier 13 and the output frequency nf _S of the VCO 12 by feedback controlling the VCO 12
Controls the oscillation frequency of VCO12. The output frequency nf _S of the VCO 12 is amplified by the L-band amplifier 17, and the frequency is multiplied by m by the frequency multiplier 18.
mnf _S , passes through output filter 19 to terminal 20
is added to the second mixer 4 in FIG. To change the value of n, adjust the VCO 12, and to change the value of m, adjust the frequency multiplier 18.

If the reference frequency signal is not input from the terminal 11, or if the synchronization is lost for some reason, there will be no DC component from the input of the loop filter 15, so the loop filter 15 will operate as a sweep oscillator and its output DC voltage will be reduced. Since the value of is varied over a wide range, the oscillation frequency of the VCO 12 is also varied over a wide range. Even when the oscillation frequency of the VCO 12 varies over a wide range, if the phase comparator 14 does not output a DC voltage that can stop the sweep oscillation of the loop filter 15, the loop filter 15 continues the sweep oscillation, and therefore the VCO
12 is swept over a wide range, and the output frequency of the transmission frequency amplifier 6 is similarly swept over a wide range. If a transmission wave of such a frequency is output, it will cause a big interference to other communications, so the out-of-synchronization is detected by the out-of-synchronization detector 16,
A method is adopted in which a signal is sent to the diode switch 7 via the fault detection circuit 10 together with a signal indicating that another fault has been detected, and the transmission output is cut off.

In the conventional circuit as described above, the degree of attenuation when the output is cut off is determined by the characteristics of the diode switch 7, so that a sufficient degree of attenuation can be obtained over a wide band.
It was difficult to prevent interference radio waves from being output. Also, the time delay in comprehensive operations became a problem.

The invention aims to eliminate the above-mentioned drawbacks in conventional circuits. 3 is a connection diagram showing the connection of the output stage after the frequency multiplier 18 in FIG. 2, 21 indicates the output terminal of the L-band amplifier 17 in FIG. (multiplier diode), 23 is a C-band tuning circuit, 24 is a resistor, 25, 26, 27 are L
A coil and a capacitor equivalently represent a band tuning circuit. That is, in the conventional circuit, the varactor 22 is short-circuited by the resistor 24 and placed in a biased state with good frequency multiplication efficiency, and the signal of the frequency nf _S inputted from the terminal 21 is sent to the circuit 23 at the frequency
Output as mnf _S signal. The value of m can be changed by changing the circuit 23.

In the present invention, the diode switch 7 in the conventional circuit can be omitted simply by slightly changing the wiring shown in FIG. 3 and adding a control circuit for causing a forward bias current to flow through the varactor 22. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a connection diagram showing an embodiment of the present invention, in which the same reference numerals as in FIG. It is controlled by the output of the fault detection circuit 10 shown in FIG.

That is, in order to design a circuit equivalent to the conventional microwave signal generator shown in FIG. 1 using the circuit of the present invention, the diode switch 7 is omitted from the circuit shown in FIG. the second
into the local oscillator 9, and by changing part of the circuit of the second local oscillator 9 as shown in FIG.
may be controlled by the output of the fault detection circuit 10. When there is no output from the out-of-sync detector 16, the terminal 28 is grounded and operates in the same way as the circuit shown in Figure 3, and the frequency nf _S of the input signal to the terminal 21 is mnf _S
However, when there is an output from the out-of-sync detector 16, a voltage that causes a forward bias current to flow through the varactor 22 is connected to the terminal 28 via the failure detection circuit 10, and the frequency of the varactor 22 is multiplied and output. Efficiency is significantly reduced and the output from terminal 20 of FIG. 2 is virtually eliminated, and therefore the output of transmit frequency amplifier 6 of FIG. 1 is effectively eliminated. According to the inventor's experiments, by controlling the terminal 28 in FIG. 4 as described above, an attenuation of 60 dB or more can be obtained at the output of the transmission frequency amplifier 6 in FIG. 1.

Moreover, if the terminal 28 is grounded, the frequency multiplication efficiency is immediately recovered and the frequency is increased from the transmitting frequency amplifier 6.
Can output mnf _S signal.

As described above, according to the present invention, a sufficient degree of attenuation can be obtained compared to the conventional circuit, and the diode switch 7 can be omitted. Furthermore, since both the fault detection and the control based on the fault detection are performed within the second local oscillator 9, the problem of time delay can be greatly improved.

The present invention has been described above with reference to the case where it is applied to a signal generator used in a microwave band transmitter, etc., but it goes without saying that the present invention can be applied to all frequency multiplier circuits using diodes.

[Brief explanation of the drawing]

FIG. 1 is a block connection diagram showing an example of a conventional circuit, FIG. 2 is a block connection diagram showing an example of internal connections of the second local oscillator shown in FIG.
FIG. 4 is a connection diagram showing the connection of the output stage after the frequency multiplier shown in the figure, and FIG. 4 is a connection diagram showing one embodiment of the present invention. In these figures, 4 is a second mixer, 5 is a transmission frequency band filter, 6 is a transmission frequency amplifier, 9 is a second local oscillator, 10 is a fault detection circuit, and 12 is a
VCO, 13 is a reference frequency amplifier, 14 is a phase comparator, 15 is a loop filter, 16 is an out-of-sync detector, 22 is a varactor, and 28 is a varactor control terminal. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A signal with a reference frequency _S and a voltage controlled oscillator 1
2, a loop filter 15 that amplifies the output of this phase comparator 14 and outputs its average value, and this loop A phase lock loop that feedback-controls the oscillation frequency of the voltage controlled oscillator 12 using the output of the filter 15 and locks the fundamental frequency to be equal to n _S (where n is any positive integer); When the lock is released, the loop filter 15 is automatically operated as a sweep oscillator and the voltage controlled oscillator 12 is activated.
means for frequency modulating the output of the oscillator, a frequency multiplier circuit 18 that applies a signal of the fundamental frequency to the diode 22 and generates a harmonic frequency with respect to the fundamental frequency due to the nonlinear characteristics of the diode, and the loop filter 15 operates as a sweep oscillator. A frequency multiplier circuit comprising: an out-of-synchronization detector for detecting that the out-of-synchronization detector is operating; and a control circuit for controlling a forward bias current to flow through the diode 22 based on the output of the out-of-synchronization detector.