JPS6337538B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiving device using a communication system that transmits information to be transmitted by changing a plurality of frequencies.

This type of communication method is called the so-called spread spectrum communication method, and one of the methods is the frequency hopping method (FH method: Frequency hopping method).
Hopping System). In this method, for example, as shown in FIG. 1a, N center frequencies ₁ , ₂ , ₃ , . . . _N , predetermined as shown in FIG. The bit information is expressed as a frequency deviation Δ to the positive side or negative side with respect to each center frequency, and this is repeatedly transmitted every N bits.
On the other hand, on the receiving side, since the above frequency arrangement and frequency deviation are known, after receiving the transmitted signal and establishing synchronization, the direction of frequency deviation from the center frequency (positive or negative side) is detected. Restore digital information by However, conventional communication systems of this type transmit digitized information using N irregularly changing frequencies, so the transmission frequency changes irregularly over a wide band. For this reason, the receiving filter had to have a wide bandwidth, and had the disadvantage of being susceptible to interference.

In order to eliminate this interference, some devices have conventionally combined a wide band filter and N narrow band filters, while others have used a wide band filter and the center frequency of the passband to be changed by external control. This was achieved by combining narrow band filters.

Therefore, since the former device uses a large number of narrow band filters with different center frequencies, the speed of frequency change is not restricted by the time required for control as in the latter device, but on the other hand, the device is large and compact. There was a drawback that it could not be applied to equipment that required

In addition, the latter device requires only one narrow-band filter whose passband center frequency is changed by external control, and can be applied to a small device. Since the frequency change speed is restricted by the time required for this control, the amount of information to be transmitted is reduced.

The present invention provides a receiving device which is small in size, does not reduce the transmission speed, and effectively eliminates reception interference such as interference in a communication system that transmits information using a plurality of frequency changes.

In other words, the present invention is a communication system in which information to be transmitted is transmitted by changing a plurality of frequencies corresponding to the information, in which a filter with a wide bandwidth is applied to the high frequency input on the receiving side, and the center frequency of the passband is changed under external control. has a narrow bandwidth filter that
When out of synchronization, synchronization is achieved by receiving signals through a wide-bandwidth filter, and after synchronization is achieved, reception is performed by switching to a narrow-bandwidth filter whose center frequency changes under external control, and changes in the frequency on the transmitting side are performed. It is comprised of a control circuit that controls the center frequency of the narrow bandwidth filter and switches between a plurality of filters in accordance with the above.

Next, an embodiment of the present invention will be described with reference to FIG. 2 showing a block diagram.

The receiving device according to the present invention includes an antenna 1 that captures incoming radio waves, a high frequency changeover switch 2 that switches high frequency input from a filter synchronously or asynchronously,
A wideband filter 3 through which signals pass during asynchronous times, narrowband filters 5 and 7 through which signals pass during synchronization, a synchronization section 10 that synchronizes during asynchronous times, and control that controls the center frequency of the pass band of the narrowband filters 5 and 7 during synchronization. 11, and DA converters 6 and 8 that convert the digital control signal from the control unit 11 into DA converters and control the center frequencies of the passbands of the narrowband filters 5 and 7, whose center frequencies of the passbands change under external control.
, narrowband filter switching devices 4 and 9 for switching the narrowband filter 5 , a demodulator 12 , and an output terminal 13 .

Next, the operation of the receiving apparatus according to the present invention will be explained.

Since the incoming radio waves input from the antenna 1 are not synchronized in the initial state, they are passed through the wideband filter 3 by the high frequency selector switch 2, and then
After being led to the synchronization section 10 and synchronized, the high frequency switch 2 is switched to switch to a narrowband filter. After synchronization is achieved, the control section 11 controls the frequencies of the filters 5 and 7 and the changeover switches 4 and 9 in accordance with the frequency change on the transmitting side. For example, if the frequency on the transmitting side changes in the order of ₁ , ₂ , ₃ , etc., while receiving the frequency before ₁ , the control unit 11 sends the digital signal corresponding to ₁ to the AD converter 6. The AD converter 6 converts the digital signal from 11 into an analog signal and sends it to the filter 5.
In addition to the varicap, the center frequency of filter 5 is controlled to ₁ .

Next, from the moment when ₁ is received, the switches 4 and 9 are switched to the filter 5 side by the control unit 11, and the signal is received through the filter 5 whose center frequency is controlled to ₁ . ₂
The AD converter 8 converts the digital signal from 11 into an analog signal, adds it to the varicap of the filter 7, and controls the center frequency of the filter 7 to ₂ .

Next, from the moment when ₂ is received, switches 4 and 9 are switched to the filter 7 side by the control unit 11, and the center frequency is received through the filter 7 controlled to ₂ , and during that time, the control unit 11 passes the AD conversion unit 6 to the filter Control the center frequency of 5 to ₃ .

Similarly, the filter 5 and the filter 7 are alternately switched and received, and the filter output is sent to the demodulator 12.
and outputs the demodulated output to the output terminal 13.

As explained above, the present invention provides a band-limiting filter 2 whose center frequency is changed by external control.
By configuring it to alternately switch between
A communication method that is compact and uses multiple frequencies to transmit information without being constrained by the speed of frequency change due to the time required to control the center frequency of the passband. By attenuating unnecessary frequencies and eliminating receiver mixer spurious noise, external interference, interference, etc., it is possible to significantly improve reception conditions.

[Brief explanation of the drawing]

FIGS. 1a and 1b are diagrams showing an example of a communication system for transmitting digital information by changing a plurality of frequencies, and FIG. 2 is a block diagram showing an embodiment of a receiving device according to the present invention. be. 1... Antenna, 2... High frequency selection switch,
3... Broadband filter, 4, 9... Narrowband filter switching device, 5, 7... Narrowband filter whose pass band center frequency is changed by external control.
6, 8...DA conversion section, 10...Synchronization section, 11...
...Control unit, 12...Demodulation unit, 13...Output terminal.

Claims (1)

[Claims] 1 In a receiving device for a signal in which information is transmitted by changing a plurality of predetermined frequencies, a first filter having a wide bandwidth through which the plurality of frequency components pass, and a center frequency of the pass band having a plurality of second filters with narrow bandwidths that change under control; a synchronization means that synchronizes with the changes in the plurality of frequencies; and a synchronization means that receives the signals through the first filters when they are out of synchronization; and a control means for controlling the center frequency of the passband of the second filter and a plurality of filters for reception according to changes in the frequency on the transmitting side. Features of the receiving device.