JPH0810842B2 - Receiver for frequency hopping communication - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver in frequency hopping communication, and more particularly to a receiver in a communication system using frequency hopping and linear modulation.

[0002]

2. Description of the Related Art Amplitude modulation (AM), single sideband modulation (SS)
B), a receiver using linear modulation such as quadrature amplitude modulation (QAM) and frequency hopping is generally provided with an automatic gain control circuit for stabilizing a demodulated signal.
Hereinafter, the case of AM modulation will be described as an example.

FIG. 3 is a block diagram showing an automatic gain control section of a conventional receiver.

In the figure, the received radio frequency (RF)
The signal is amplified by the RF amplifier 101, and the mixer 10
2, the mixer 102 mixes the RF signal with the hopping local signal from the hopping local signal generator 103 to generate an intermediate frequency (IF) signal.

The IF signal is amplified by the IF amplifier 104 and then demodulated by the demodulation circuit 105. The demodulated signal is averaged by the low pass filter 106, and the average value is input to the IF amplifier 104 as a gain control signal.

FIG. 4 is a schematic signal waveform diagram for explaining the ideal operation of the above conventional example.

In the figure, the RF signal is an AM modulation signal whose carrier frequency hops. This RF signal is mixed with the hopping local signal to become an IF signal having a constant frequency (intermediate frequency). The hopping local signal changes its frequency in synchronization with the hopping carrier frequency so that an intermediate frequency occurs.

The IF signal is demodulated by the demodulation circuit 105, and the demodulated signal is averaged by the low-pass filter 106 to become a gain control signal. Therefore, this gain control signal is R
The signal has a magnitude proportional to the carrier level of the F signal.

The IF amplifier 104 changes its amplification degree in inverse proportion to the magnitude of the gain control signal. As a result, a constant level AM-modulated IF signal is obtained from the IF amplifier 104, and even if the carrier level of the RF signal changes.
The demodulation circuit 105 always outputs a constant demodulation signal.

A receiving device having such an automatic gain control circuit is disclosed in Japanese Patent Application Laid-Open No. 1-202031.

[0011]

However, in the above-mentioned conventional configuration, the cut-off frequency of the low-pass filter can be set to only the lowest frequency of the demodulation signal or less, so that the level fluctuation depending on the hopping of the carrier frequency is corrected. It was difficult to do.

The frequency of the RF signal changes every hopping time, but there may be a difference in propagation loss depending on the frequency. In this case, since the level fluctuation of the input RF signal occurs depending on the hopping of the carrier frequency,
In the configuration in which the demodulated signal is averaged by the low-pass filter to control the gain of the IF amplifier as in the conventional example, the level fluctuation cannot be completely corrected, and the demodulated signal is distorted.

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a receiving apparatus capable of correcting a level fluctuation caused by hopping of a carrier frequency to obtain a demodulated signal without distortion.

A receiving device according to the present invention is a receiving device in a communication system using frequency hopping and linear modulation, and a detecting means for extracting a signal including a signal level and a modulated signal component from a received signal, and the detecting means. Control means for removing the modulated signal component from the output signal and outputting a gain control signal corresponding to a signal level fluctuation for each hopping time, and a variable amplification for amplifying the received signal with a gain according to the gain control signal. Means and demodulation means for demodulating the signal output from the variable amplification means.

[0015]

The detecting means and the control means generate a gain control signal corresponding to the level fluctuation of the received signal for each hopping time, and the gain control signal of the variable amplifying means removes the level fluctuation of the received signal. Adjust the amplification. Therefore, the signal output from the variable amplification means has its level fluctuation corrected for each hopping time.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a receiving apparatus according to the present invention.

Frequency hopping and linear modulation (here A
In a receiver of a communication system using M modulation),
The RF amplifier 1 amplifies the received RF signal and outputs the amplified RF signal 11 to the mixer 2.

The hopping local signal generator 3 generates a hopping local (HL) signal whose frequency changes in synchronization with carrier frequency hopping and outputs it to the mixer 2.

The mixer 2 mixes the RF signal 11 and the HL signal to generate an IF signal 12 of an intermediate frequency, and the delay circuit 4
Output to.

The delay circuit 4 delays the input IF signal 12 by one hopping time, and delays the delayed IF signal 13 by IF.
Output to the amplifier 5.

The mixer 2 also outputs the IF signal 12 to the level detector 6. The level detector 6 detects the carrier level corresponding to the envelope line of the RF signal, and outputs the level detection signal 14 to the integrator 7.

The integrator 7 operates in synchronization with hopping,
The level detection signal 14 is integrated every hopping time, and the integrated signal 15 is output to the sample hold circuit 8. A reset signal R that resets the output every hopping time is input to the integrator 7. A low-pass filter may be used instead of the integrator 7.

The sample and hold circuit 8 also operates in synchronization with hopping, and holds the final result of the previous hopping time output by the integrator 7 for the next hopping time,
The holding signal 16 is output to the IF amplifier 5 as a gain control signal.

The IF amplifier 5 amplifies the delayed IF signal 13 in accordance with the holding signal 16 and corrects the IF as described later.
The signal 17 is output to the demodulation circuit 9.

The demodulation circuit 9 demodulates the IF signal 17 and outputs a demodulation signal 18. The demodulation circuit 9 of this embodiment is an envelope line detector.

The operation of this embodiment having such a configuration will be described with reference to the signal waveform diagram.

FIG. 2 is a schematic signal waveform diagram for explaining the operation of this embodiment.

The RF signal to be transmitted is an AM modulation signal whose frequency changes to f ₁ , f ₂ , f ₃ ... For each hopping time.

When such an RF signal is received, level fluctuation is included for each hopping due to the difference in propagation loss due to frequency. That is, as shown in the figure, the amplitude level of the received RF signal 11 varies with each frequency hopping.

The received RF signal 11 is HL by the mixer 2.
The resulting IF signal 12 mixed with the signal
Also includes level fluctuations like the received RF signal 11.
Therefore, even if the IF signal 12 is demodulated as it is, only a demodulated signal including distortion can be obtained.

The IF signal 12 is delayed by one hopping time by the delay circuit 4 and becomes a delayed IF signal 13.

On the other hand, the IF signal 12 input to the level detector 6 is level-detected, and the level detection signal 1 is thereby detected.
4 is obtained. The level detection signal 14 is a signal in which the AM modulation signal component and the carrier level fluctuation component due to hopping are added.

The level detection signal 14 has the modulated signal component removed by the integrator 7, and becomes the integrated signal 15. It should be noted that in FIG. 2, the hopping period is shorter than the modulation signal period for convenience of description.

The final value of the hopping time of the integrated signal 15 is held by the sample hold circuit 8 for the next hopping time, and is output to the IF amplifier 5 as a holding signal 16. The hold signal 16 becomes a signal having a level proportional to the carrier level fluctuation generated by hopping.

The hold signal 16 is input as a gain control signal, and the IF amplifier 5 controls the gain in inverse proportion to the signal level of the hold signal 16. As a result, the IF amplifier 5 can remove the carrier level fluctuation included in the delayed IF signal 13, and can obtain the corrected IF signal 17.

By demodulating the corrected IF signal 17, a correct demodulated signal 18 without distortion can be obtained.

Although the AM modulation is illustrated in this embodiment,
Of course, the present invention is not limited to this. It is easy to apply the present invention to other linear modulation receivers.

[0039]

As described in detail above, the receiving apparatus in the frequency hopping communication according to the present invention generates a gain control signal corresponding to the carrier level fluctuation at every hopping time, and amplifies the received signal by the gain control signal. Adjust the degree. Therefore, the received signal becomes a signal whose level fluctuation is corrected every hopping time, and a demodulated signal without distortion can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a receiving apparatus according to the present invention.

FIG. 2 is a schematic signal waveform diagram for explaining the operation of the present embodiment.

FIG. 3 is a block diagram showing an automatic gain control section of a conventional receiving device.

FIG. 4 is a schematic signal waveform diagram for explaining an ideal operation of the above conventional example.

[Explanation of symbols]

 1 RF Amplifier 2 Mixer 3 Hopping Local Signal Generator 4 Delay Circuit 5 IF Amplifier 6 Level Detector 7 Integrator 8 Sample Hold Circuit 9 Demodulation Circuit 11 Received RF Signal 12 IF Signal 13 Delayed IF Signal 14 Level Detection Signal 15 Integrated Signal 16 Hold signal 17 Corrected IF signal 18 Demodulated signal

Claims (5)

[Claims] 1. In a receiver in a communication system using frequency hopping and linear modulation, a detection unit for extracting a signal including a signal level and a modulation signal component from a reception signal, and the modulation signal from an output signal of the detection unit. A control unit that removes a component and outputs a gain control signal corresponding to the fluctuation amount of the signal level for each hopping time; a variable amplification unit that amplifies the reception signal with a gain according to the gain control signal; A demodulation unit that demodulates a signal output from the variable amplification unit. 2. A receiving device in a communication system using frequency hopping and linear modulation, wherein delay means delays a received signal by one hopping time, and a signal including a signal level and a modulated signal component is taken out from the received signal. Detecting means, control means for removing the modulation signal component for each hopping time from the output signal of the detecting means, and outputting a gain control signal proportional to the signal level fluctuation in the subsequent hopping time; A receiving device comprising: a variable amplifying unit that amplifies the delayed received signal output from the delay unit with a gain that is inversely proportional to the level; and a demodulating unit that demodulates the signal output from the variable amplifying unit. . 3. The control means comprises an integrator that integrates the signal from the detection means for each hopping time, and a sample hold circuit that holds the final output of the integrator for the next hopping time. The receiving device according to claim 2, wherein 4. In a receiver in a communication system using frequency hopping and linear modulation, frequency conversion means for converting a received high frequency signal into an IF signal of an intermediate frequency, and delay means for delaying the IF signal by one hopping time. A detection means for extracting a signal including a signal level and a modulation signal component from the IF signal; and removing the modulation signal component for each hopping time from the output signal of the detection means, and a signal level fluctuation component in a subsequent hopping time. Control means for outputting a gain control signal proportional to the IF, and IF for amplifying the delayed IF signal output from the delay means with a gain inversely proportional to the signal level of the gain control signal.
A receiving apparatus comprising: an amplifying unit; and a demodulating unit that demodulates the signal output from the IF amplifying unit. 5. The control means comprises an integrator that integrates the signal from the detection means for each hopping time, and a sample hold circuit that holds the final output of the integrator for the hopping time for the next hopping time. The receiving device according to claim 4, wherein: