JPH0832490A - Hopping filter - Google Patents

Abstract

PURPOSE:To enhance high speed of a frequency changeover (settling time) of a hopping filter used in frequency hopping communication or direct spread/ frequency hopping hybrid communication. CONSTITUTION:When a band pass filter BPF-A105 is selected, filter selection switch sections 107, 108 select the band pass filter BPF-A105 and simultaneously a D/A converter 103 applies a band pass filter BPF-B applied voltage 115 representing a hopping frequency used for a succeeding period to a band pass filter BPF-B 106. Thus, a tuned frequency of the band pass filter BPF-B 106 is set to a succeeding hopping frequency till a succeeding hopping period, the switch sections 107, 108 select the band pass filter BPF-B 106 at the start of the succeeding period to select a hopping frequency quickly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fast tuning filter, that is, a so-called hopping filter used in a transceiver of frequency hopping communication or direct spread / frequency hopping hybrid communication.

[0002]

2. Description of the Related Art Frequency hopping (hereinafter referred to as FH) communication is used as one of spread spectrum communication systems. This FH communication system is a communication system in which the frequency used for communication is switched at regular intervals. Therefore, in the transceiver used in this communication system, a so-called hopping filter in which the tuning frequency is switched at regular intervals is used. An example of the structure of a conventional hopping filter is shown in FIG. In the example shown in FIG. 4, a filter having a fixed tuning frequency is provided for each hopping channel, and these fixed filters are switched by each hopping cycle. This switch includes an input side filter selection switch section 10 to which an RF signal is input and an output side filter selection switch section 12 from which an RF signal is output. These switches 10 and 12 switch the filters BPF-1 to BPF-n having a fixed tuning frequency. Also,
As shown in FIG. 4, frequency channel information representing the frequency at the time of hopping is input to the input-side and output-side filter selection switch units 10 and 12, respectively.
Switching is performed based on this frequency channel information.

In FIG. 4, the input side and output side filter selection switch sections 10 and 12 are shown as mechanical switches, but this is the switch section 1.
This is a schematic representation of the functions of 0 and 12, and in practice it is often composed of electronic switching elements such as transistors.

Another example of the configuration of a conventional hopping filter is shown in FIG. In the hopping filter shown in FIG. 5, the pass band frequency of the filter is hopped by switching the applied voltage applied to the varicap diode that determines the frequency characteristic of the filter for each hopping cycle. . This is generally called a varicap tuning method. As shown in FIG. 5, the applied voltage applied to the varicap diode is generated by the memory 20 and the D / A converter 22 based on the frequency channel information. This memory 20 is composed of, for example, a P-ROM, inputs the input frequency channel information into the address terminal, and outputs the binary value of the applied voltage (applied to the varicap diode) representing the frequency from the data terminal. To do. The binary value of the applied voltage is supplied to the D / A converter 22, and the D / A converter 22 converts the binary value into a desired applied voltage. By applying this applied voltage to the varicap diode, the pass band characteristic of the filter changes.

[0005]

As described above, as shown in FIG.
According to the filter switching method shown in (1), there is a problem in that band-pass filters are required for the number N of hopping channels, the size of the hopping filter becomes large, and the cost also increases. Further, the input side and output side selection switch units 10 and 12 also have to sequentially select a desired channel from the number of N channels, which causes a problem that the circuit becomes complicated.

In addition, the varicap shown in FIG.
In the tuning method, it takes a certain time to generate an applied voltage to be applied to the varicap diode based on the frequency channel information. That is, the memory 2
It takes a certain time until the D / A converter 22 needs the applied voltage after the data of 0 is output. Also,
Further, since it takes a certain period of time from the application of this applied voltage to the varicap diode until the tuning of the bandpass filter, there is a certain limit in the frequency switching, that is, the hopping speed.

The present invention has been made in view of the above problems, and an object thereof is to set a frequency switching time (setting time) of a hopping filter used in frequency hopping communication or direct spread / frequency hopping hybrid communication. ) Is faster, and is also synchronized with the frequency hopping synthesizer.

[0008]

In order to solve the above-mentioned problems, a first hopping filter used in frequency hopping communication or direct spread / frequency hopping hybrid communication determines a pass band by an applied voltage. The first and second tunable bandpass filters that can be changed and the first and second tunable bandpass filters are alternately selected in synchronization with the hopping period, and the selected first Alternatively, the selection means for outputting the output signal of the second variable tuning bandpass filter is included.

Since the two variable tuning bandpass filters are provided in this manner, the hopping frequency can be switched at high speed.

In order to solve the above problems, the second aspect of the present invention is capable of changing the pass band in an hopping filter used for frequency hopping communication or direct spread / frequency hopping hybrid communication by an applied voltage. Variable tuning bandpass filter, correction table means for correcting frequency channel information of hopping frequency, and frequency channel information corrected by the correction table means is converted into an applied voltage to be supplied to the variable tuning bandpass filter. A converter, and the tuning frequency of the variable tuning bandpass filter matches the frequency of the signal generated by the frequency hopping synthesizer based on the frequency channel information by the correction in the correction table means.

Therefore, the data can be easily corrected by writing the corrected data in the correction table. As a result, the frequency output by the frequency hopping synthesizer used in the transceiver and the tuning frequency of the hopping filter match with each other with high accuracy.

[0012]

In the first aspect of the present invention, since the two variable tuning bandpass filters are provided, the hopping frequency can be switched at high speed by switching them according to the hopping cycle. That is, while the first variable tuning bandpass filter is being used, the second variable tuning bandpass filter is tuned to the next hopping frequency, and after the hopping period elapses, the second variable tuning bandpass filter is tuned. By switching to the pass filter, the hopping frequency can be switched quickly.

The correction table means in the second aspect of the present invention corrects the frequency channel information. Even if frequency channel information is input from the code generator and control voltage from the code generator is applied to the varicap diode, it takes a certain amount of time to tune as described above. It was not possible to synchronize with the generated frequency.

Therefore, with this correction table, it is possible to match the tuning frequency set in the variable tuning bandpass filter with the frequency generated by the frequency hopping synthesizer. An explanatory diagram showing how the frequency hopping synthesizer and the hopping filter are connected in the transmitter and the receiver is shown in FIG. As shown in FIG. 6, in the transmitter, the modulated signal output from the modulator 30 is spectrum-spread, and therefore is multiplied by the hopping frequency output from the frequency hopping synthesizer 34 in the multiplier 32. The multiplication result is the hopping filter 3
After being filtered by 6, it is emitted from the antenna 38 as a radio wave into the space. Here, the frequency hopping synthesizer 34 and the hopping filter 36 are supplied with the frequency channel information from the code generator 40, and ideally, the frequency output from the frequency hopping synthesizer 34 and the hopping filter It must match the tuning frequency.

The receiver also has substantially the same configuration as the transmitter. As shown in FIG. 6, at the receiver, the signal received from the antenna 50 is
After being filtered by the filter 52, the multiplier 54 multiplies the signal output from the frequency hopping synthesizer 56. In this way, in the receiver, by passing through the route opposite to the transmitter,
So-called spectrum demodulation is performed. The signal thus spectrally demodulated is demodulated by the demodulation unit 1 for general demodulation.
8 is supplied. As shown in FIG. 6, the frequency channel information from the code generator 60 is also supplied to the hopping filter 52 and the frequency hopping synthesizer 56 in the receiver as well. As a result, the tuning frequency of the hopping filter 52 and the frequency of the signal output by the frequency hopping synthesizer 56 are ideally matched.

In the second aspect of the present invention, the correction table means is provided so that the frequency specified by the frequency channel information and the tuning frequency of the hopping filter can be exactly matched, and the spread spectrum and demodulation can be performed. It will be.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a hopping filter according to a preferred embodiment of the present invention. As shown in FIG. 1, the hopping filter of the present embodiment is equipped with a bandpass filter BPF-A105 and a BPF-B106 of a varicap tuning type, and these two bandpass filters are used for high speed operation. The switch is switchable to select.

First, as shown in FIG. 1, the hopping filter is supplied with frequency channel information 10. The frequency channel information 110 is supplied as an address signal of the memory 101. The memory 101 is configured by using, for example, a P-ROM or the like as in the conventional configuration. Further, a hopping clock 112 is supplied to this hopping filter as a band pass filter B.
It is supplied for switching between the PF-A 105 and the BPF-B 106. The hopping clock 112 is divided by the frequency divider 109 into 1/2. The divided clock 113 is supplied to the input side filter selection switch unit 10
7 and the output side filter selection switch unit 108, the band pass filters BPF-A105 and BPF-B106 are switched every hopping cycle. The divided clock 113 is used in the switch unit 1
It is supplied as one of the address signals to the memory 101 described above as well as to 07 and 108. Since the divided clock 113 is obtained by dividing the hopping clock 112, it is a signal that repeats "0" and "1" for each hopping cycle. As described above, the input side filter selection switch unit 107 and the output side filter selection switch 10
In No.8, "0" and "1" for each hopping cycle
The filter is switched by using the repetition of and. Since the frequency-divided clock 113 is also supplied to the memory 101, the frequency-divided clock 11 is stored in the memory 101 even if the frequency channel information 110 is the same.
Different data can be output due to the different values of 3. In other words, the memory 101 has the selected band pass filter from the BPF-A 105 to the BPF.
Different values can be output depending on -B106.

With such a configuration, for example, BPF-A
Even if the band pass filter 105 and the BPF-B 106 have different characteristics, it is possible to set a more accurate tuning frequency by outputting the corresponding data. That is, according to this embodiment, the two band pass filters BPF-A105 and BPF-B10 are provided.
Therefore, it is possible to correct the variation with respect to 6.
Of course, as for this correction data, the relationship between the applied voltage and the tuning frequency in the band pass filters BPF-A105 and BPF-B106 is checked in advance,
It is necessary to create correction data.

The data output from the memory 101 includes two band pass filters BPF-A105 and BPF-B10.
It is output to both the D / A converters 102 and 103 respectively provided for every six. Note that each of the D / A converters 102 and 103 is provided with a latch, and the supplied data can be held independently. As shown in FIG.
The divided clock 113 is supplied to each latch. The divided clock 113 is directly supplied to the latch of the D / A converter 103, and the divided clock 113 is supplied to the latch of the D / A converter 102 via the inverter 104. As a result, one of the latches latches the data output from the memory 101 every hopping cycle.

The characteristic of this embodiment is that the two band-pass filters BPF-A10 provided in this way.
5 and the BPF-B 106 are provided with the D / A converters 102 and 103, respectively. In this way, the dedicated D / A converters 102 and 10 are respectively provided.
The provision of 3 allows the memory 101 to output different data depending on the selected bandpass filter, and the latch independently holds the data supplied to each bandpass filter. And D / A
The converters 102 and 103 can perform D / A conversion. Therefore, one of the band pass filters (BPF
-A105 or BPF-B106) while supplying the applied voltage to one D / A converter 102 or 103, the other D / A converter 103
Alternatively, 102 performs D / A conversion of a separate applied voltage, and the other band pass filter BPF-A105 or BPF-
It is possible to supply it to B106 beforehand.
Therefore, there is a time margin of about a hopping period after the applied voltage is applied to the bandpass filter and before the switching of the filter occurs.Therefore, the tuning frequency of the bandpass filter after switching is set to a desired frequency in advance. It is possible to set. Therefore, it is possible to realize a hopping filter capable of switching the tuning frequency extremely quickly.

Next, the operation of the hopping filter of this embodiment will be described with reference to the time chart shown in FIG. As shown in FIG. 2, the hopping clock 112 represents the timing at which the frequency channel information 110 changes. The divided clock 113 obtained by dividing the hopping clock 112 is a signal that repeats "0" and "1" for each hopping cycle. In the present embodiment, this divided clock 113 is used as the selected bandpass filter (BPF-A105 or BPF-).
B106) is supported, and in the case of "0", BPF-
In the case of A105 and "1", BPF-B106 is instructed respectively. As shown in FIG. 2, the output frequencies of the frequency hopping synthesizer are f1, f depending on the values Df1, Df2, ... Df7 of the frequency channel information 110.
It changes like 2 ... f7.

As shown in FIG. 2, since the divided clock 113 is "0" in the cycle 1, the band pass filter BPF-A105 is selected. At this time, the output frequency of the frequency hopping synthesizer is f1 according to Df1 of the frequency channel information 110. At this time D
The / A converter 102 supplies Vf1A as the BPF-A applied voltage 114 to the bandpass filter BPF-A105.

The characteristic feature of this embodiment is that in this cycle 1, the applied voltage generating digital data 111 output from the memory 101 is the band pass filter BPF-B10.
6 is f2B. That is, this cycle 1
In this case, the value f2B of the applied voltage generating digital data 111 is held in the latch of the D / A converter 103, and the D / A converter 103 starts to apply the applied voltage Vf2 corresponding to the f2B to the band pass filter BPF-B106. Is. Thus, in cycle 1, the BPF
-B applied voltage 115 is band pass filter BPF-B1
It is possible to set the tuning frequency of the band-pass filter BPF-B106 to f2 by the next period 2 because it starts to be applied to 06. Thus, the hopping frequency can be automatically switched by switching the input side filter selection switch section 107 and the output side filter selection switch section 108 at the start of the cycle 2. In the conventional bandpass filter using the varicap diode, it takes a certain time from when the applied voltage is changed until the desired tuning frequency is set again. According to the method, the required tuning frequency in the cycle 2 can be set in the band-pass filter BPF-B106 which is not selected in the previous cycle 1 in advance, so that the hopping frequency can be switched quickly. Becomes In the same way, this cycle 2
In this case, a new BPF-A applied voltage 114 is applied to the band pass filter BPF-A105 (Vf3A), so that the tuning frequency in cycle 3 is set in advance in the band pass filter BPF-A105. It is possible. As a result, the hopping frequency can be quickly switched by switching the switch units 107 and 108 at the start of the cycle 3 as described above. Thereafter, the band pass filter BPF-A105 and the band pass filter BPF-B106 are alternately used in the cycles 4, 5, 6, and 7.

FIG. 3 is an explanatory diagram of the stored contents of the memory 101 used in the hopping filter of this embodiment. As shown in FIG. 3, the stored contents of the memory 101 are whether the address MSB is “0” or “1”, whether the band pass filter BPF-B106 is used,
It is determined whether it is for the band pass filter BPF-A105. That is, since the applied voltage generating digital data can be stored and held for each of the two band pass filters provided in the memory 101 in the present embodiment, the digital data that matches the characteristics of each band pass filter is stored. It is possible. As a result, it is possible to realize the tuning with the synthesizer by storing the data for respectively correcting the timing information of the hopping frequency. The values of the frequency channel information 110 supplied from the outside are used as they are for bits other than the MSB of the address of the memory 101.

As described above, according to the present embodiment, two variable band pass filters whose tuning frequency is set by the applied voltage are provided and alternately switched for each hopping cycle, so that the hopping can be switched at high speed. -A filter can be realized. Further, two band pass filters BPF-A105 and BPF-B1 are provided.
Since the memory 101 capable of holding digital data according to their characteristics is provided for each 06, it is possible to correct variations in characteristics of the bandpass filter and realize an accurate tuning frequency. This makes this hopping
The tuning frequency of the filter can be easily matched with the frequency output by the frequency hopping synthesizer.

[0028]

As described above, according to the first aspect of the present invention, since two variable tuning bandpass filters are provided,
Since the filters can be switched at high speed, it is possible to realize a hopping filter adaptable to communication with a short hopping cycle.

According to the second aspect of the present invention, since the frequency channel information supplied to the converter can be corrected in advance, a hopping filter which requires a more accurate tuning frequency can be realized. As a result, since the output frequency of the frequency hopping synthesizer and the tuning frequency of the hopping filter can be matched, more accurate frequency hopping communication can be performed.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a hopping filter which is a preferred embodiment of the present invention.

FIG. 2 is a time chart showing the operation of the preferred embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating stored contents of a memory 101 of a hopping filter which is a preferred embodiment of the present invention.

FIG. 4 is a configuration block diagram of a hopping filter according to a conventional filter switching method.

FIG. 5 is a configuration block diagram of a hopping filter according to a conventional varicap tuning method.

FIG. 6 is a configuration block diagram of a transmitter and a receiver in frequency hopping communication.

[Explanation of symbols]

 101 memory 102, 103 D / A converter 104 inverter 105 band pass filter BPF-A 106 band pass filter BPF-B 107 input side filter selection switch section 108 output side filter selection switch section 109 frequency divider 110 frequency channel information 111 applied voltage Digital data for generation 112 Hopping clock 113 Divided clock 114 Applied voltage for BPF-A 115 Applied voltage for BPF-B

Claims (2)

[Claims] 1. Frequency hopping communication or direct spreading /
In a hopping filter used for frequency hopping hybrid communication, first and second tunable bandpass filters capable of changing a pass band according to an applied voltage, and the first and second tunable bands in synchronization with a hopping period. A hopping filter, comprising: a selection unit that alternately selects two variable tuning band pass filters and outputs an output signal of the selected first or second variable tuning band pass filter. 2. Frequency hopping communication or direct spread /
In a hopping filter used for frequency hopping hybrid communication, a tunable band pass filter capable of changing a pass band according to an applied voltage, a correction table unit for correcting frequency channel information of a hopping frequency, and the correction table A converter for converting the frequency channel information corrected by the means into an applied voltage to be supplied to the variable tuning bandpass filter, and the tuning frequency of the variable tuning bandpass filter is corrected by the correction table means. A hopping filter, which matches the frequency of a signal generated by a frequency hopping synthesizer based on the frequency channel information.