JPS6351563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for instantaneously sweeping and generating a predetermined frequency or a frequency band including a predetermined frequency among the frequencies when a frequency having a required bandwidth is generated by a sweep repetition signal. The present invention relates to a sweep signal generator.

When generating a frequency with a desired bandwidth using a sweep repetition signal, if you want to generate the frequency excluding a predetermined frequency f ₀ or a frequency band in the vicinity including the predetermined frequency f ₀ , use a band-elimination filter. It is generally considered that the transmission is performed via

Furthermore, even if transmission characteristics do not need to be considered, if the bandwidth to be removed is narrow, a band-elimination filter using a crystal must be used, which poses a cost problem.

This invention was made in view of these problems, and the power level of the frequency band to be removed is attenuated by instantaneously sweeping the frequency band to be removed with a substantially steep waveform signal with a rising or falling edge. The present invention provides a sweep signal generating device that generates a sweep signal having substantially the same effect as that removed by a band-elimination filter. This invention will be explained below.

FIG. 1 shows an embodiment of the sweep signal generating device of the present invention, and FIG. 2 is a waveform diagram for explaining the operating state of the embodiment of FIG.

In FIG. 1, 1 is a sweep repetition signal generator that repeatedly generates a waveform such as a 50Hz or 60Hz sine wave or triangular wave. A comparator 2 is composed of a differential amplifier, and the output signal of the sweep repetition signal generator 1 is applied to one input terminal. 3 is a frequency controlled oscillator, which is composed of a voltage controlled oscillator, etc.
Generate a sweep signal with a bandwidth of 905-930MHz. 4 is a local oscillator, which is composed of a voltage controlled oscillator, etc., and normally oscillates at a frequency of 780MHz. 5
is a frequency mixer, in which the 905-935MHz sweep signal output from the frequency controlled oscillator 3 is applied to one input terminal, and the sweep signal from the local oscillator 4 is applied to the other input terminal.
Add a 780MHz signal and the difference frequency is 125 ~
Generates a swept signal in the 155MHz intermediate frequency band.
6 is the output terminal, 125~ from frequency mixer 5
Outputs a 155MHz signal. 7 is a frequency discriminator,
For example, PCD (Pulse Counted Discriminator)
After converting the output of the frequency mixer 5 into a rectangular wave with a constant pulse width, the rectangular wave is low-pass filtered and converted into a DC voltage according to a change in frequency. This DC voltage is applied to the other input of the comparator 2 and compared with the output of the sweep repetition signal generator 1 applied to said one input, and the frequency is adjusted to obtain a frequency that matches the comparison output. The controlled oscillator 3 is controlled to improve its linearity. 8 is a trigger pulse generator, mixer 8a, reference oscillator 8
b, and a low-pass filter 8c, and the intermediate frequency band signal of 125 to 155 MHz output from the frequency mixer 5 is applied to one input terminal of the mixer 8a, and the signal in the intermediate frequency band of 125 to 155 MHz is applied to the other input terminal of the mixer 8a. Of the intermediate frequency band signals, a reference frequency corresponding to the frequency f ₀ (for example, 138 MHz) is added from the reference oscillator 8b and mixed. The mixed output is applied to a low-pass filter 8c with a cut-off frequency of 500 KHz, and a trigger pulse is generated at a time position 0.5 μS before the generation time position of frequency f ₀ . 9 is a waveform signal generator, which is composed of a monostable multivibrator, etc., and generates a rectangular wave signal with a width of 1 μS with a steep rise or fall according to the trigger pulse output from the trigger pulse generator 8, and locally transmits this signal. In addition to the oscillator 4, its oscillation frequency is changed instantaneously.

Next, the operation will be explained with reference to the waveform diagram in FIG.

While the local oscillator 4 is oscillating a constant frequency of 780 MHz, the output terminal 6 outputs a frequency f ₀ and an intermediate frequency band f ₁ to f ₂ (126 to
A signal of 155 MHz is repeatedly generated by a sine wave of a sweep repetition signal generator 1. This sweep signal is applied to one input terminal of the mixer 8a, and the frequency (138MHz) of the reference oscillator 8b corresponding to the frequency f ₀ is added to the other input terminal for mixing. area filter 8c
In addition, when the sweep frequency is sweeping from low to high as shown in Figure 2b, (f ₀ -500)
Beat signal A is generated at the generation time position of the frequency of KHz, and when the sweep frequency is sweeping from high to low, beat signal B is generated at the generation time position of the frequency of (f ₀ +500) KHz. That is, beat signals A and B are located at a time position 0.5 μS earlier than the time position at which frequency f ₀ occurs. These beat signals are shaped into trigger pulses, and in addition to the waveform signal generator 9, a rectangular wave with a width of 1 μS with a steep rise or fall is generated from this waveform signal generator 9 as shown in Fig. 2c. Occur. By applying this rectangular wave to the local oscillator 4 and changing its oscillation frequency, a sweep signal that instantaneously sweeps a band of ±500KHz with respect to the frequency f ₀ is output to the output terminal 6, as shown in FIG. 2d. arises from. Figure 2e shows the waveform of the sweep signal, which is an enlarged view of the part surrounded by the dotted line in Figure 2d.As mentioned above, f _a (f ₀
−500) KHz to f _b (f ₀ +500KHz) above 1μS
It can be seen that the sweep occurs instantaneously at the rise of the square wave. Therefore, by instantaneously sweeping the frequency band to be removed at the rising or falling edge of a rectangular wave signal, the instantaneous swept f _a to f _b
The power level of each frequency of is reduced by about 30 dB or more compared to the power level under normal conditions, and the sweep has an effect substantially similar to that of removing the sweep signal of FIG. 2a with a band-elimination filter. can generate a signal.

FIG. 3 shows the frequency versus power level of the sweep waveform of FIG. 2d. The waveforms actually observed with a spectrum analyzer were also similar.

In the above embodiment, the output of the waveform signal generator 9 is added to the local oscillator 4 to generate the sweep signal shown in FIG. The signal may be superimposed on the output and applied to the comparator 2. Further, the trigger pulse generator 8 of the above embodiment can generate a predetermined trigger pulse even if the sweep signal of the frequency mixer ₅ is applied directly to the low _- pass filter 8c having a bandwidth of frequencies fa to fb. mixer 8a and reference oscillator 8.
b may be omitted. Furthermore, in the above embodiment, the waveform signal generator 9 generates a rectangular wave signal as shown in FIG. a
The waveforms shown in ~d may also be used.

As explained in detail above, the present invention allows a predetermined frequency or a frequency band including a predetermined frequency to be controlled by a rising or falling edge of a waveform signal having a steep rising edge or falling edge, out of a sweep signal having a required bandwidth. Since the sweep is generated instantaneously, the power level of each frequency swept instantaneously is attenuated, and the effect is essentially the same as that removed by a band-elimination filter without deteriorating the transmission characteristics. It has the advantage that it can be realized at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 a to e are waveform diagrams of essential parts to explain the operation of the embodiment of FIG. 1, and FIG. 3 is a sweep waveform of FIG. 2 d. Characteristic diagram showing the frequency versus power level of , Figure 4a
-d are waveform diagrams showing various other examples output from the waveform signal generator. In the figure, 1 is a sweep repetition signal generator, 2 is a comparator, 3 is a frequency control oscillator, 4 is a local oscillator, and 5
is a frequency mixer, 6 is an output terminal, 7 is a frequency discriminator, 8 is a trigger pulse generator, and 9 is a waveform signal generator.

Claims (1)

[Claims] 1 A sweep signal generating device that sweeps and generates a frequency having a required bandwidth by being swept by a sweep repetition signal: Receives the frequency having the required bandwidth, and detects the generation time position of a predetermined frequency f ₀ among these frequencies. a trigger pulse generator for generating a trigger pulse a predetermined time before the trigger pulse; and a waveform signal generator for generating a waveform signal with a steep rise or fall according to the trigger pulse; When a frequency having the required bandwidth is generated in a sweep manner using the sweep repetition signal, the predetermined frequency f ₀ is generated instantaneously at a rising edge or a falling edge of the waveform signal instead of the sweep repetition signal. A sweep signal generator characterized by: