JPS6318899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase synchronized microwave signal generator that is often used as a local oscillator of a frequency converter in microwave band wireless communication equipment, etc.
In particular, it relates to the fault (out of synchronization) detection circuit.

FIG. 1 shows the circuit configuration of a conventionally used phase-locked signal generator. In the figure, 1 is a reference signal oscillator, which is usually composed of a crystal oscillator or a frequency synthesizer, and its output is amplified by an amplifier 2 and then applied to a harmonic generator 3, where harmonics are generated. It is applied to the phase comparator 4.
On the other hand, 5 is usually an oscillator using a semi-coaxial circuit, etc., and the oscillator 5 is a so-called voltage controlled oscillator whose oscillation frequency can be controlled by a varactor.
Controlled Oscillator (hereinafter referred to as VCO). The output of the VCO 5 is applied to a multiplier 6, which multiplies it by M to obtain a desired output frequency. Depending on the required frequency, the multiplier 6 may not be used and the output of the VCO 5 may be used as is. On the other hand, the output of the VCO 5 is also taken out to the phase comparator 4 side, the phase difference with the harmonic of the reference signal is detected by the phase comparator 4, and the output is applied to the loop filter 7. After the loop filter 7 amplifies the phase difference signal, the output is sent to the VCO.
The oscillator is configured such that the frequency of the VCO 5 is finally synchronized with the harmonics of the reference signal of the reference signal oscillator 1.

If the reference signal is not output or if the synchronization is lost for some reason, the loop filter 7 causes a sweep oscillation by the positive feedback circuit, and thereby
The output signal of the VCO 5 is configured to sweep until synchronization occurs.

If the synchronization occurs here, in order to detect it as a failure, in the conventional method, the detection circuit 8
is used. This detection circuit 8 consists of a capacitor diode detector 8a and a Schmitt trigger circuit 8b, which are directly connected to the output of the loop filter 7. While the oscillator is synchronized, the output of the loop filter 7 becomes DC, so the detector 8a Although nothing is input, when the oscillator is out of synchronization, the loop filter 7 causes sweep oscillation, so AC input is applied to the detector 8a, and its output drives the Schmitt trigger circuit 8b in the next stage to generate a fault signal. .

In this conventional circuit, a fault is detected by the generation of a sweep signal, so the fault is not detected until after the oscillator has swept at least one cycle. For example, before the sweep signal is transmitted by a transmitter, etc. It is impossible to turn off the output at any time, and if the sweep signal does not occur even though it is not synchronized for some reason, for example, if the offset voltage of the loop filter occurs, it cannot be detected. There were flaws.

The present invention has been made to eliminate such drawbacks of the conventional system, and includes a beat signal detection circuit that detects a beat signal from a signal obtained by mixing a signal multiplied by a reference signal and the output of a VCO. Furthermore, by providing a reference signal detection circuit, it is possible to detect a fault at the same time as the start of the sweep if synchronization is lost, and also to effectively detect a fault even when a sweep signal is not generated. The purpose of the present invention is to provide a wave signal generator.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a phase-locked microwave signal generator according to an embodiment of the present invention. 1 to 7 in the diagram are the first
Although it is exactly the same as the figure, in the present invention, each circuit 9 to 13 is used in place of the detection circuit 8 of FIG. Here, 9 is a multiplier circuit that multiplies the output of amplifier 2, 10 is a mixer that mixes the output of multiplier circuit 9 and the output of VCO 5, 11 is an amplifier that amplifies the output of mixer 10, and 12 is a capacitor diode detector. A beat signal detection circuit 13 is a reference signal detection circuit that detects a reference signal from the output of the amplifier 2.

Next, the operation will be explained. The multiplier circuit 9 takes out a part of the output of the amplifier 2 and multiplies it by N to obtain the necessary harmonics. This multiplier circuit 9 is equivalent to the harmonic generation circuit 3, but the harmonic generation circuit 3
This case differs from the multiplier circuit 9 in that there is no need to suppress harmonics of different orders. The output of this multiplier circuit 9 is applied to a mixer 10. On the one hand, the output signal of the VCO 5 is applied to this mixer 10, which is extracted by a new combiner. An amplifier 11 is connected to the output of the mixer 10, and a beat signal detection circuit 12 comprising a capacitor diode detector 12a and a Schmitt trigger circuit 12b is further connected to the output. According to this circuit configuration, while the oscillator is synchronized, the frequencies of the output of the multiplier circuit 9 and the output of the oscillator 5 are exactly the same, so the output of the mixer 10 becomes DC, and the beat signal detection circuit 12 does not operate. . However, if the oscillator gets out of synchronization,
Since the output of the multiplier circuit 9 and the output of the oscillator 5 have different frequencies, a difference signal, that is, a beat signal, appears in the output of the mixer 10. If this beat signal is amplified and detected by the beat signal detection circuit 12, a failure can be detected at the same time as the sweep oscillation starts.

Further, the reference signal detection circuit 13 detects the multiplier circuit 9 when there is no reference signal or when the reference signal becomes extremely low.
If the oscillator is made to operate when the beat signal detection circuit 12 does not operate (naturally, the oscillator will be out of synchronization in this case as well), it is possible to issue a failure signal when the beat signal detection circuit 12 does not operate.

Furthermore, by setting the band of the amplifier 11 to be similar to the sweep frequency range of the oscillator 5, all beat signals can be detected, and even if the sweep signal is not generated due to lack of synchronization, failures can be detected. It is possible.

In fact, with this circuit configuration, the detection time, which was several tens of milliseconds according to the conventional method, could be shortened to several microseconds.

In the above embodiment, a phase-locked signal generator using a varactor has been described, but the present invention can be applied to any phase-locked oscillator.

As described above, according to the present invention, there is provided a beat signal detection circuit that detects a beat signal from a signal obtained by mixing a signal obtained by multiplying a reference signal and the output of a VCO, and further a reference signal detection circuit is provided. Therefore, high-speed out-of-synchronization detection is possible, and when combined with a diode switch etc., when the oscillator in a communication device is out of synchronization, the output can be detected before the sweep signal is sent out or during a slight deviation in the output signal. It is possible to refuse. This is particularly useful in devices that use a frequency synthesizer or the like as a reference signal and switch the output frequency many times.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional phase-locked microwave signal generator, and FIG. 2 is a circuit diagram of a phase-locked microwave signal generator according to an embodiment of the present invention. 1... Reference signal oscillator, 3... Harmonic generator,
4... Phase comparator, 5... VCO, 7... Loop filter, 9... Multiplier, 10... Mixer, 12
...Beat signal detection circuit, 13...Reference signal detection circuit. In the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A reference signal oscillator that oscillates a reference signal, a high frequency generator that generates a high frequency of the reference signal, and a phase comparator that detects the phase of the output of this high frequency generator and the output of the voltage controlled oscillator. A loop filter receives the output of the phase comparator and applies the output to the voltage controlled oscillator, a multiplier multiplies the reference signal, and mixes the output of the multiplier with the output of the voltage controlled oscillator. 1. A phase synchronized microwave signal generator comprising: a mixer for detecting a beat signal; and a beat signal detection circuit for detecting a beat signal from the output of the mixer. 2. The phase-locked microwave signal generator according to claim 1, further comprising a reference signal detection circuit for detecting a reference signal from the output of the reference signal oscillator.