JPS6336697B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a communication system receiving device that transmits information 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, for each bit of time-series digital information to be transmitted, N center frequencies ₁ , ₂ , ₃ , ... _N are predetermined as shown in Fig. 1b. 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 doing so. However, conventionally, this type of communication system transmits 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 drawback of being susceptible to interference.

The present invention provides a receiving device that effectively eliminates the above-mentioned drawbacks (reception interference), interference, etc. that occur in a communication system that transmits information by changing a plurality of frequencies.

In order to achieve this object, the present invention has a filter with a wide bandwidth at the input stage of the receiving device and a filter with a narrow bandwidth whose passband center frequency changes under external control. When synchronization is achieved, the center frequency of the passband is switched to a narrowband filter in which the center frequency of the passband changes under external control, and the center frequency of the passband is changed to the change of the transmitting side frequency ( It is configured to receive data by changing it according to the frequency arrangement).

Next, one 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 synchronizes the antenna 1 that captures incoming radio waves and the high frequency input from the antenna 1 when they are not synchronized, and after synchronization, the center frequency of the normal band is changed by external control. A control section 5 and a demodulation section 6 that output a digital output that controls the center frequency of the passband of the narrow filter 4 to change in accordance with changes in the frequency on the transmitting side.
a high-frequency bypass switch 3 which is connected through a broadband filter 2 and disconnects the connection under the control of the control section 5 during synchronization; a switch 9 which operates reciprocally with the bypass switch 3; and a control section 5.
A DA converter 7 converts the digital control output of the digital control output to control the change in the center frequency of the passband of the narrow-band filter 4 whose passband center frequency changes by external control, and the output of the demodulator 6. terminal 8.

Next, the operation of the receiving apparatus according to the present invention will be explained.
Incoming radio waves enter the receiving device through the antenna 1, and since they are not synchronized in the initial state of reception, the high frequency bypass switch 3 becomes conductive, and the high frequency input passes through the broadband filter 2 to the control unit 5,
The signal is input to the demodulator 6. At this time, since the switch is in a non-conductive state, no incoming radio waves are input to the filter 4. When synchronization is established by the control section 5, the high frequency bypass switch 3 becomes non-conductive, while the switch 9 becomes conductive, and the incoming radio wave is input to the filter 4. At the same time, the controller 5 outputs a digital output that changes the center frequency of the passband of the filter 4, which has a narrow bandwidth and whose center frequency changes under external control, in accordance with changes in the frequency on the transmitting side. , is input to the DA converter 7. The DA converter 7 converts the digital output from the controller 5 into analog and supplies it to the variable capacitance diode of the filter 4. Therefore, the center frequency of the passband of the filter 4 is controlled to match the change in frequency on the receiving side. Demodulator 6
receives the output from the broadband filter 2 or filter 4 and outputs the demodulated output to the output terminal 8.

As explained above, the present invention transmits information using a plurality of frequencies by changing the center frequency of the receiving band limiting filter and configuring a narrow band filter that matches irregular frequency changes on the transmitting side. While covering the wide band of reception frequencies characteristic of communication systems, it attenuates unnecessary frequencies at certain moments, eliminating receiver mixer spurious noise, external interference, interference, etc., greatly improving reception conditions. effective.

[Brief explanation of drawings]

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 apparatus according to the present invention. 1...Antenna, 2...Broadband filter, 3
...9... High frequency bypass switch, 4... Narrow bandwidth filter whose passband center frequency changes under external control, 5... Control section, 6... Demodulation section, 7... DA conversion section, 8...Output terminal.

Claims (1)

[Claims] 1. In a signal receiving device in which information is transmitted by changing a plurality of predetermined frequencies, a first filter with a wide bandwidth that passes the plurality of frequency components, and a center frequency of the pass band that is a second filter with a narrow bandwidth that varies under control;
synchronization means for synchronizing the plurality of frequency changes;
control means for receiving through the first filter when out of synchronization, switching to the second filter for reception when synchronization is established, and controlling the center frequency of the passband in synchronization with changes in the frequency on the transmitting side; A receiving device comprising: