JPH0222940A - Frequency synthesizing device - Google Patents

Abstract

PURPOSE:To reduce an unstable section in the switching of a frequency and to improve transmission efficiency by providing two tuning type band-pass filters at an output stage, and switching and using them selectively by a switching control signal. CONSTITUTION:A frequency synthesizer 1 outputs a hopping signal whose frequency channel changes in prescribed sequence by a frequency control signal. It is assumed that the output signal performs frequency hopping in sequence of the frequency channels F1, F2,... as shown in figure (a). Switches 2 select the tuning type band-pass filters 3a and 3b alternately with a switching control signal with a timing (the timing synchronized with the frequency control signal) shown in Fig. (a), and the output signal is filtered and outputted from the frequency synthesizer 1. In such a way, it is possible to reduce a period where data becomes unstable at the time of switching the frequency, and to improve the transmission efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a frequency synthesis device in a frequency hopping type communication device that communicates by switching frequency channels in a time series according to a predetermined procedure.

(Summary of the Invention) The present invention provides a frequency synthesis device for a frequency hopping communication device that communicates by switching frequency channels in time series in a predetermined procedure. By switching between frequency channels, the period during which data becomes unstable when frequency channels are switched is shortened as much as possible, thereby making it possible to improve transmission efficiency.

(Prior Art) FIG. 4 is a block diagram showing a conventional frequency synthesizer of this type of communication device, as shown in, for example, "Latest Spread Spectrum Communication System" (Shachik Publishing). In this figure, 1 is a frequency synthesizer and 3 is a tuned bandpass filter.

Next, the operation will be explained.

The frequency synthesizer 1 outputs a signal (hopping signal) in which frequency channels change in a predetermined order according to a frequency control signal. The hopping signal is input to a tuned bandpass filter 3, which attenuates unnecessary waves outside the band and outputs it. Tunable bandpass filter 3 is controlled to tune to the output frequency channel by a tuning control signal.

(Problem to be Solved by the Invention) Since the conventional frequency synthesizer is configured as described above, when the frequency is switched by the frequency control signal, the tuning response time of the tunable bandpass filter 3 is required until the output is stabilized. For example, when the hopping signal changes in the order of frequency channels F+-Fz*Fx as shown in FIG.
FI T + occurs.

Therefore, when demodulating data, it is necessary to provide a hold time to invalidate the data in that section, resulting in problems such as deterioration of transmission efficiency.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a frequency synthesizer that can configure a communication device with a short load time and little deterioration in transmission efficiency.

(Means for Solving the Problems) A frequency synthesizer according to the present invention includes two tuned bandpass filters or a plurality of bandpass filters to which the output of a frequency synthesizer of a frequency hopping type communication device is input. The tunable bandpass filter or the bandpass filter is selectively used by being switched by a switching control signal.

(Operation) The frequency synthesizer according to the present invention includes two tuned bandpass filters provided in the output stage and each tuned to the next hopping frequency channel, or a plurality of tuned bandpass filters each corresponding to each of a plurality of frequency channels. Since the configuration is such that the bandpass filters are switched and selectively used, the unstable section during frequency switching becomes smaller.

(Embodiment) An embodiment of the frequency synthesizer according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a frequency synthesizer according to an embodiment of the present invention. In the figure, 1 is a frequency synthesizer that changes the output frequency according to a frequency control signal, and 2 is a tunable bandpass filter. Switcher to switch and select 3 at
3b is a tuned bandpass filter that attenuates unnecessary waves outside the output band.

FIGS. 2(a), 2(b), and 2(c) are explanatory diagrams showing the desired output signal, the tuning frequency of the tunable bandpass filter 3a, and the tuning frequency of the tunable bandpass filter 3b, respectively.

Moreover, FIG. 5 is a waveform diagram showing the output signal of the frequency synthesizer, and FIG. 5(a) is the output from the conventional frequency synthesizer, and FIG. 5(b) is the output from the frequency synthesizer according to the present embodiment. It is.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

The frequency synthesizer 1 outputs a hopping signal in which frequency channels change in a predetermined order according to a frequency control signal. It is assumed that this output signal undergoes frequency hopping in the order of frequency channels F l # F 21 F 3 t, . . . as shown in FIG. 2(a), for example. The switching control signal causes the switching device 2 to switch on the tunable bandpass filter 3 at the timing shown in #i2 diagram (a) (timing synchronized with the frequency control signal).
at 3 b are selected alternately, and the output signal from the frequency synthesizer 1 is filtered and output.

As can be seen from Fig. 2, the tunable bandpass filter 3at 3
b is twice the switching time of the output signal (switching speed 1/2
) is provided with a tuning control signal, as shown in FIG. 2(b).

As shown in parentheses, it is previously tuned to the next hopping frequency channel before being selected by switch n2.

Therefore, the tuning response time of the tunable bandpass filter is reduced, and as shown in Fig. 5, the period T2 during which data is unstable during frequency switching is shortened compared to the conventional frequency synthesizer, resulting in improved transmission efficiency. Significantly improved.

In the above embodiment, a tuned bandpass filter is used, but as shown in another embodiment in FIG. It is also possible to use a plurality of containers and switch between them, and the same effect as in the above embodiment can be obtained. In FIG. 3, 1 is a frequency synthesizer for frequency hopping, 2 is a switch, and 4 is a fixed bandpass filter. Here, the bandpass filter 4 has tuning frequencies corresponding to a plurality of frequency channels sequentially output from the frequency synthesizer 1.

In another embodiment of FIG. 3, the frequency synthesizer 1 selects the frequency channels FIIF 21
39..., the switching control signal causes the switch 2 to output the bandpass filter tuned to Fl, F
The bandpass filters 4 are switched in synchronization with the frequency hopping period and selected in the following order: a bandpass filter tuned to F.2, a bandpass filter tuned to F, and so on. In this case too,
This has the effect of shortening the period during which data becomes unstable during frequency switching and improving transmission efficiency.

In the other embodiment shown in FIG. 3, the tuning control signal can be omitted compared to the case where a tuned bandpass filter is used, and if the bandpass filter 4 can be made smaller (for example, S
(using an AW filter, etc.), it is possible to provide a smaller device than one using a tuned bandpass filter.

In addition, in the above embodiment and other embodiments, the switching device 2 is provided before and after the tuned bandpass filter 3 and the bandpass filter 4. A distributor that distributes high frequency signals or a synthesizer that combines high frequency signals may be used, and the same effects as the above embodiments and modifications can be achieved.

(Effects of the Invention) As described above, according to the present invention, two tuned bandpass filters or a plurality of bandpass filters are provided in the output stage, and the configuration is such that they can be selectively used by switching with a switching control signal. Therefore, by providing a frequency synthesizer with a short unstable interval during frequency switching, it is possible to obtain a communication device with a short guard time and little deterioration in transmission efficiency.

[Brief explanation of the drawing]

FIG. 2 is an explanatory diagram showing the relationship between the output signal of the frequency synthesizer and the tuning frequency of the tunable bandpass filter,
FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG.
FIG. 5 is a block diagram showing a conventional frequency synthesizer, and FIG. 5 is an explanatory diagram comparing output signals of the frequency synthesizer in the conventional case and in the case of the present invention. 1... Frequency synthesizer, 2... Switcher, 3... Tunable bandpass filter, 4... Bandpass filter. Figure 1 Figure 2

Claims (2)

[Claims] (1) A frequency synthesizer for a frequency hopping communication device that communicates by switching frequency channels in a predetermined order in a time sequence, comprising: a frequency synthesizer that outputs a plurality of frequency channels in a predetermined order; and two tuned bandpass filters that are alternately switched and selected by a switching control signal so that the output of the frequency synthesizer is input, and each tuned bandpass filter is connected to the frequency synthesizer before being switched and selected. A frequency synthesizer characterized in that the frequency synthesizer is controlled by a tuning control signal to tune to the frequency channel of the output of the frequency synthesizer. (2) A frequency synthesizer for a frequency hopping type communication device that communicates by switching frequency channels in a predetermined order and time series, comprising: a frequency synthesizer that outputs a plurality of frequency channels in a predetermined order; and a plurality of bandpass filters that are switched and selected by a switching control signal so as to receive the output of the frequency synthesizer as input, and each bandpass filter is configured to input one of the frequency channels of the output of the frequency synthesizer. A frequency synthesizer characterized by being synchronized.