JP2002152064A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of cross modulation and mutual modulation and to previously avoid the drop of communication quality. SOLUTION: In a receiver 1, a second amplifier 16 measures the received electric field intensity of a third intermediate frequency signal. A first amplifier 6 controls to drop a gain based on the measured result of the second amplifier 16. An orthogonal demodulation circuit can previously avoid the influence of an interference wave, can suppress the occurrence of cross modulation and mutual modulation and can previously avoid the drop of communication quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for performing communication in accordance with, for example, a frequency hopping standard.

[0002]

DISCLOSURE OF THE INVENTION Direct Diffusion (DS: Dire)
ct Sequence) method, by increasing the spreading factor,
Although it is possible to increase the interference resistance against interference waves,
On the other hand, frequency hopping (FH)
In the pping method, when any one of a plurality of carriers in the own station collides with any carrier in another station, an interference wave may be input into the receiver. Then, in this case, when an interference wave having a relatively large received power is input into the receiver, a quadrature demodulation circuit or the like is affected by the interference wave, and cross-modulation or intermodulation occurs. Therefore, there is a possibility that the error rate is reduced and the communication quality is reduced.

[0003] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a receiving apparatus capable of suppressing the occurrence of cross-modulation and inter-modulation, and capable of avoiding a decrease in communication quality. To provide machines.

[0004]

According to the receiver of the present invention, the receiving electric field strength measuring means measures the receiving electric field strength of the intermediate frequency signal, and the gain controlling means measures the receiving electric field strength measuring means. Since the gain of the radio frequency signal is controlled based on the result, the gain of the radio frequency signal is reduced so that the gain of the radio frequency signal is reduced when an interference wave having relatively large received power is input into the receiver. , It is possible to prevent the influence of the interference wave on the quadrature demodulation circuit and the like, thereby suppressing the occurrence of cross-modulation and inter-modulation, and preventing the communication quality from deteriorating. Can be avoided.

According to a second aspect of the present invention, the signal-to-noise ratio measuring means measures the signal-to-noise ratio of the baseband signal, and the gain control means calculates the signal-to-noise ratio of the baseband signal. In addition, since the gain of the radio frequency signal is controlled based on the measurement result of the signal-to-noise ratio measuring means, the cross-modulation and the intermodulation can be performed in the same manner as in the above-described claim 1. Generation can be suppressed,
A decrease in communication quality can be avoided beforehand. Also,
In this case, the gain of the radio frequency signal is controlled based on the measurement result of the signal-to-noise ratio measurement means as well as the measurement result of the reception electric field strength measurement means. The reliability can be improved as compared with the above-mentioned one.

According to the third aspect of the present invention, since the receiver is applied to a device that performs communication according to the standard of the frequency hopping system, the standard of the frequency hopping system is widely released for medical, scientific and industrial applications. ISM (Indu
Considering the fact that there is a wide range of radio waves that can be interference waves for receivers that communicate in accordance with the frequency hopping standard, the above-mentioned advantages are fully exploited. We can make use of it.

[0007]

(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. First, FIG. 1 shows, as a functional block diagram, a portion related to the gist of the invention in the receiver. In an RF (Radio Frequency) unit 2 of the receiver 1, a first band-pass filter 3 transmits a radio frequency signal (R
When the F signal is input, the band of the input radio frequency signal is limited, and the band-limited radio frequency signal is output to the first amplifier 6 through the switch 5. When a radio frequency signal is input from the first bandpass filter 3 through the switch 5, the first amplifier 6 (gain control means in the present invention) amplifies the input radio frequency signal and converts the amplified radio frequency signal into a second signal. The first multiplier 7 and the second multiplier 8
Output to Also. In this case, the first amplifier 6 has a function of automatic gain control (AGC: Automatic Gain Control).

When the first multiplier 7 receives a radio frequency signal from the first amplifier 6, the first multiplier 7 performs a first phase shift from a voltage controlled oscillator 10 of a PLL (Phase Lock Loop) circuit 9. A first intermediate frequency signal (IF (Intermediate Frequency) signal) is generated by multiplying a local oscillation signal input through the shifter 11, and the generated first intermediate frequency signal is output to the second phase shifter 12. I do. When the first intermediate frequency signal is input from the first multiplier 7, the second phase shifter 12 shifts the phase of the input first intermediate frequency signal and adds the shifted first intermediate frequency signal. Output to the container 13.

When the second multiplier 8 receives the radio frequency signal from the first amplifier 6, the second multiplier 8 receives the input radio frequency signal and the radio frequency signal from the voltage controlled oscillator 10 of the PLL circuit 9 through the first phase shifter 11. A second intermediate frequency signal is generated by multiplying the second intermediate frequency signal by the local oscillation signal.
Is output to the third phase shifter 14. Third
When the second intermediate frequency signal is input from the second multiplier 8, the phase shifter 14 shifts the phase of the input second intermediate frequency signal, and adds the phase-shifted second intermediate frequency signal to the adder 13. Output to

[0010] The adder 13 outputs the signal from the second phase shifter 12 to the first phase shifter.
, And the third phase shifter 14
, A second intermediate frequency signal is input to generate a third intermediate frequency signal by adding the two input intermediate frequency signals, and the generated third intermediate frequency signal is supplied to the second bandpass filter 15. Output. When the third intermediate frequency signal is input from the adder 13, the second band-pass filter 15 performs band limitation on the input third intermediate frequency signal, and converts the band-limited third intermediate frequency signal into the second intermediate frequency signal. 2 to the second amplifier 16.

When the second amplifier 16 (receiving electric field strength measuring means in the present invention) receives the third intermediate frequency signal from the second band pass filter 15, the second amplifier 16 amplifies the input third intermediate frequency signal. , And outputs the amplified third intermediate frequency signal to the discriminator 17. Also, in this case, the second amplifier 16 measures the received electric field strength of the third intermediate frequency signal, and based on the measurement result, the first amplifier 6
To control the gain. And the discriminator 17
Receives a third intermediate frequency signal from the second amplifier 16, generates a baseband signal by demodulating the input third intermediate frequency signal, and sends the generated baseband signal to the baseband unit 18. Output.

The above-mentioned PLL circuit 9 includes a frequency divider 19 and a phase comparator 2 which inputs a reference oscillation signal from a reference oscillator 20.
1. It is configured to include a first low-pass filter 22 and a voltage-controlled oscillator 10. When a baseband signal is input from the baseband unit 18 through a second low-pass filter 23, feedback control of a radio frequency signal is performed, and feedback control is performed. The output radio frequency signal is output to the third amplifier 24. When the radio frequency signal is input from the PLL circuit 9, the third amplifier 24 amplifies the input radio frequency signal, and switches the amplified radio frequency signal to the switch 5.
To the first band-pass filter 3 through.

When a radio frequency signal is input from the third amplifier 24 through the switch 5, the first band pass filter 3 limits the band of the input radio frequency signal, and transmits the band-limited radio frequency signal to the antenna 4. Output to When the radio frequency signal is input from the first band pass filter 3, the antenna 4 radiates the input radio frequency signal as a radio wave.

Next, the operation of the above configuration will be described with reference to FIG.
This will be described with reference to FIG. Here, FIG. 2 is a flowchart showing the contents of control performed when the receiver 1 connects a line, and FIG. 3 is a flowchart showing contents of control performed after the receiver 1 connects a line. Is shown.

First, control performed when the receiver 1 connects a line will be described with reference to a flowchart shown in FIG. When detecting the presence of a device that can be a communication partner near itself, the receiver 1 determines “Y” in step S1.
ES ”, a predetermined line connection procedure is started (step S2), and the second amplifier 16 measures the received electric field strength of the third intermediate frequency signal (step S3).

Then, the receiver 1 compares the measured received electric field strength with a predetermined threshold value serving as a reference electric field strength (step S4), and if the measured received electric field strength exceeds the threshold value, "YES" in step S4
Is determined, and the second amplifier 16 outputs a gain reduction instruction to the first amplifier 6, thereby temporarily lowering the gain in the first amplifier 6 (step S5).

After the gain is temporarily reduced in this way, the receiver 1 again compares the measured received electric field strength with a predetermined threshold value serving as a reference electric field strength (step S6). If the measured received electric field strength is less than the threshold value, it is determined to be “YES” in step S6, and the second amplifier 16 outputs a gain return instruction to the first amplifier 6, whereby the first amplifier 6 Is restored (step S7).

On the other hand, if the measured received electric field strength is equal to or smaller than the threshold, the receiver 1 determines “NO” in step S4, performs a correlation process using an access code (step S8), and determines whether synchronization is maintained. A synchronization determination is made as to whether or not there is (Step S9). If the synchronization is maintained, the receiver 1 determines “YES” in step S9,
A request or response to the inquiry or call is performed (step S10), authentication is performed (step S11), encryption is performed (step S12), and a line is established. If the synchronization is not maintained, the receiver 1 determines “NO” in step S9 and stops the reception.

In this way, when connecting the line, the receiver 1 measures the reception electric field strength of the third intermediate frequency signal, and the reception electric field strength of the third intermediate frequency signal exceeds the threshold value. In such a case, the gain of the first amplifier 6 is reduced to prevent the quadrature demodulation circuit (for example, the discriminator 17) from being affected by the interference wave.

Next, control performed after the receiver 1 connects the line will be described with reference to the flowchart shown in FIG. The receiver 1 measures the reception electric field strength of the third intermediate frequency signal in the second amplifier 16 (Step S).
21). Then, the receiver 1 compares the measured received electric field strength with a predetermined threshold value serving as a reference electric field strength (step S22). If the measured received electric field strength exceeds the threshold value, the receiver 1 proceeds to step S22. "YE
S ", and the second amplifier 16 outputs a gain reduction instruction to the first amplifier 6 to temporarily lower the gain in the first amplifier 6 (step S23).

In this case as well, after the gain is temporarily lowered in this case, the receiver 1 again compares the measured reception electric field strength with a predetermined threshold value which is a reference electric field strength. Then, if the measured received electric field strength is less than the threshold value (step S24), it is determined to be “YES” in step S24, and the second amplifier 16 outputs a gain return instruction to the first amplifier 6, so that the second amplifier 16 outputs a gain return instruction. The temporarily reduced gain of the first amplifier 6 is restored (step S25).

On the other hand, if the measured reception electric field strength is equal to or smaller than the threshold, the receiver 1 determines “NO” in step S22.
Is determined, and synchronization is maintained (step S26). Then, when a request to disconnect the line is generated, the receiver 1 determines “YES” in step S27 and disconnects the line.

In this manner, the receiver 1 measures the reception electric field strength of the third intermediate frequency signal after the line is connected, in the same manner as in the case where the line is connected, and receives the third intermediate frequency signal. When the received electric field strength of the intermediate frequency signal exceeds the threshold value, the gain in the first amplifier 6 is reduced to prevent the quadrature demodulation circuit and the like from being affected by the interference wave.

As described above, according to the first embodiment, in the receiver 1, the reception field strength of the third intermediate frequency signal is measured by the second amplifier 16 and the reception of the third intermediate frequency signal is performed. If the electric field strength exceeds the threshold, the first
Is configured to reduce the gain in the amplifier 6 of the above, so that it is possible to prevent the quadrature demodulation circuit and the like from being affected by the interference wave, thereby suppressing the occurrence of cross-modulation and inter-modulation. The communication quality can be prevented from deteriorating. In this case, the second amplifier 16 is configured to measure the received electric field strength of the third intermediate frequency signal.
In view of the fact that 6 is configured to have a high gain, there is an advantage that it is suitable for measuring the received electric field strength.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
An embodiment will be described with reference to FIGS.
The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, different parts will be described.
In the first embodiment, the gain of the radio frequency signal is controlled based on the received electric field strength of the third intermediate frequency signal. On the other hand, in the third embodiment, The configuration is such that the gain of the radio frequency signal is controlled based on the signal-to-noise ratio of the baseband signal in addition to the received electric field strength of the third intermediate frequency signal.

That is, in FIG. 4, the receiver 31
An RF unit 32 is provided instead of the RF unit 2 described in the first embodiment, and the baseband unit 2 described in the first embodiment is provided.
Instead of 0, a baseband unit 33 (signal-to-noise ratio measuring means in the present invention) is provided. Then, in this case, the baseband unit 33 measures the signal-to-noise ratio of the baseband signal, and controls the gain of the first amplifier 34 (gain control means in the present invention) based on the measurement result.

In this case, when connecting a line, the receiver 31 measures the received electric field strength of the third intermediate frequency signal as shown in FIG. 5 (step S3), and Is compared with a predetermined threshold value of the reference electric field intensity (step S4). If the measured reception electric field intensity is equal to or less than the threshold value, "NO" is determined in step S4, and then the signal of the baseband signal is determined. The noise-to-noise ratio is measured (step S31), and the measured signal-to-noise ratio is compared with a predetermined threshold value that is a reference signal-to-noise ratio (step S32).

If the received electric field strength exceeds the threshold or the signal-to-noise ratio exceeds the threshold, the receiver 31 performs the processing of step S5 described in the first embodiment. Then, the receiver 31 thus operates the first
After temporarily lowering the gain in the amplifier 34 of
The measured reception electric field strength is again compared with a predetermined threshold value serving as a reference electric field strength (step S3).
3) If the measured received electric field strength is less than the threshold value, “YES” is determined in step S33, and the temporarily reduced gain in the first amplifier 34 is restored (step S35). If the measured reception electric field strength is not less than the threshold value, the receiver 31 determines “NO” in step S33, and determines the measured signal-to-noise ratio and a threshold value that is a predetermined reference signal-to-noise ratio. Are compared again (step S34), and if the measured signal-to-noise ratio is less than the threshold, it is determined to be “YES” in step S34, and the temporarily reduced gain in the first amplifier 34 is restored (step S34). Step S35).

On the other hand, when the received electric field strength is equal to or less than the threshold value and the signal-to-noise ratio is equal to or less than the threshold value, the receiver 31 performs the processing from step S8 described in the first embodiment.

Also, as shown in FIG. 6, the receiver 31 performs the same processing as in the case of connecting the line, even after connecting the line, that is, receiving the third intermediate frequency signal. The electric field intensity is measured (step S21), and the measured received electric field intensity is compared with a predetermined threshold value serving as a reference electric field intensity (step S22). A determination of "NO" is made in S22, and then the signal-to-noise ratio of the baseband signal is measured (step S41), and the measured signal-to-noise ratio is compared with a predetermined reference signal-to-noise ratio threshold. A comparison is made (step S42).

If the received field strength exceeds the threshold or the signal-to-noise ratio exceeds the threshold,
The process of step S23 described in the first embodiment is performed. Then, the receiver 31 also performs the first
After temporarily lowering the gain in the amplifier 34 of
The measured received electric field strength is again compared with a predetermined threshold value that becomes the reference electric field strength (step S4).
3) If the measured received electric field strength is less than the threshold value, “YES” is determined in step S43, and the temporarily reduced gain of the first amplifier 34 is restored (step S45). If the measured reception electric field strength is not less than the threshold value, the receiver 31 determines “NO” in step S43, and determines the measured signal-to-noise ratio and a predetermined reference signal-to-noise ratio. Are compared again (step S44), and if the measured signal-to-noise ratio is less than the threshold, it is determined to be “YES” in step S44, and the temporarily reduced gain in the first amplifier 34 is restored (step S44). Step S45).

On the other hand, if the received electric field strength is equal to or less than the threshold value and the signal-to-noise ratio is equal to or less than the threshold value, the receiver 31 performs the processing from step S26 described in the first embodiment.

As described above, according to the second embodiment, in the receiver 31, the second amplifier 16 measures the received electric field strength of the third intermediate frequency signal, and the baseband unit 32 measures the received electric field strength. The signal-to-noise ratio of the band signal is measured, and if the received field strength of the third intermediate frequency signal exceeds the threshold, or if the signal-to-noise ratio of the baseband signal exceeds the threshold, Since the gain of the first amplifier 34 is reduced, the first
In the same manner as described in the embodiment, it is possible to prevent the quadrature demodulation circuit and the like from being affected by the interference wave, thereby suppressing the occurrence of cross-modulation and intermodulation, and Deterioration of quality can be avoided beforehand.

In this case, the gain of the first amplifier 34 is reduced based on not only the received electric field strength of the third intermediate frequency signal but also the signal-to-noise ratio of the baseband signal. As compared with the first embodiment, the reliability can be improved.

(Third Embodiment) Next, a third embodiment of the present invention will be described.
An embodiment will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, different parts will be described. In the above-described first embodiment, the first amplifier 6 having the function of automatic gain control is employed, but in contrast thereto,
In the third embodiment, an amplifier, an attenuator, and a bypass path are switched and controlled in place of the first amplifier 6.

That is, in FIG.
The F section 42 includes a switching circuit 48 (referred to in the present invention) including an input-side switch 43, an amplifier 44, an attenuator 45, a bypass path 46, and an output-side switch 47, instead of the first amplifier 6 described in the first embodiment. Gain switching means). Then, the second amplifier 16 is connected to the third amplifier 16.
The received electric field strength of the intermediate frequency signal is measured, and based on the measurement result, the switching circuit 48 is switched and controlled by one of the amplifier 44, the attenuator 45 and the bypass path 46 so as to obtain the optimum gain.

As described above, according to the third embodiment, in the receiver 41, the second amplifier 16 measures the reception electric field strength of the third intermediate frequency signal, and receives the third intermediate frequency signal. When the electric field intensity exceeds the threshold value, the gain in the switching circuit 48 is configured to be reduced. Therefore, in the same manner as described in the first embodiment,
It is possible to prevent the quadrature demodulation circuit and the like from being affected by the interference wave, thereby suppressing the occurrence of cross-modulation and inter-modulation, and preventing the deterioration of communication quality. .

(Other Embodiments) The present invention is not limited to the above embodiment, but can be modified or expanded as follows. The configuration may be such that the gain in the switching circuit described in the third embodiment is controlled based on the reception electric field strength of the third intermediate frequency signal and the signal-to-noise ratio of the baseband signal.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart.

FIG. 3 is a diagram corresponding to FIG. 2;

FIG. 4 is a functional block diagram showing a second embodiment of the present invention.

FIG. 5 is a diagram corresponding to FIG. 2;

FIG. 6 is a diagram corresponding to FIG. 2;

FIG. 7 is a functional block diagram showing a third embodiment of the present invention.

[Explanation of symbols]

In the drawing, 1 is a receiver, 6 is a first amplifier (gain control means), 16 is a second amplifier (received electric field strength measuring means),
31 is a receiver, 33 is a baseband unit (signal-to-noise ratio measuring means), 34 is a first amplifier (gain control means), 41
Is a receiver, and 48 is a switching circuit (gain control means).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04L 27/22 H04L 27/22 Z

Claims (3)

[Claims] 1. A receiving electric field strength measuring means for measuring a receiving electric field strength of an intermediate frequency signal, and a gain controlling means for controlling a gain of a radio frequency signal based on a measurement result of the receiving electric field strength measuring means. Receiver. 2. A signal-to-noise ratio measuring means for measuring a signal-to-noise ratio of a baseband signal, wherein the gain control means measures a measurement result of the reception electric field strength measuring means and a measurement result of the signal-to-noise ratio measuring means. The receiver according to claim 1, wherein the gain of the radio frequency signal is controlled based on the result. 3. The receiver according to claim 1, wherein communication is performed according to a standard of a frequency hopping system.