JPH11205169A - Receiver - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce power consumption in intermittent reception operation by shortening a carrier sense time. SOLUTION: In a PLL system receiving apparatus which converges the frequency of a VCO 3 within a predetermined range by a fractional frequency division method and switches to an integer frequency division method for reception, an integer frequency division method is used in a fractional frequency division state. Before switching to the carrier sense.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver using a PLL system for channel selection, and more particularly to a receiver which is driven by a battery and performs intermittent reception to prevent battery consumption.

[0002]

2. Description of the Related Art In a receiving apparatus of an intermittent receiving operation in which reception is continued when a radio wave is received and the power of a receiving circuit is turned off when there is no radio wave, how to detect the presence or absence of a radio wave in a short time is to reduce power consumption. It is a big factor. For this reason, a receiving apparatus using the PLL system has recently used a fractional frequency dividing system in which the convergence time of the PLL circuit is short. However, the fractional frequency division method uses the signal-to-noise ratio (S
/ N) Since the characteristics are poor, the PLL circuit is started up at high speed by the fractional frequency division method, and then switched to the conventional integer frequency division method for reception. The detection of the presence or absence of radio waves, that is, the carrier sense is switched to the integer frequency division method, and then the confirmation is made after confirming that the phase error has converged within a predetermined range.

[0003]

However, in the above-mentioned conventional receiver, when switching from the fractional frequency division method to the integer frequency division method, the oscillation frequency of the VCO fluctuates due to noise generated at the time of switching. For this reason, VC
At the moment when the switching to the integer frequency division method is performed even though the oscillation frequency of O is converging, the oscillation frequency of the VCO fluctuates and it takes time to converge. As a result, there is a problem that the time from the start of the intermittent reception operation to the start of the carrier sensing is unnecessarily extended.

[0004]

In order to solve the above-mentioned problems, the present invention confirms that the oscillation frequency of the VCO has converged within a predetermined range by a fractional frequency division method, and then performs carrier sensing to perform intermittent reception. The time from the start of the operation to the carrier sense can be reduced, thereby reducing the power consumption.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a receiving means, a carrier sensing means for detecting whether a signal inputted to the receiving means is at a predetermined level or more, and a timing for carrier sensing by the carrier sensing means. Control means, a voltage-controlled oscillating means whose oscillation frequency changes by a voltage applied to select a frequency to be received by the receiving means, and a variable frequency-dividing means for dividing the oscillation frequency of the voltage-controlled oscillating means. An integer frequency division / fraction frequency division selecting means for selecting a fraction frequency dividing method for switching the frequency dividing number of the variable frequency dividing means at a predetermined cycle or an integer frequency dividing method fixed to the predetermined frequency dividing number; Generating means, phase comparing means for comparing the phases of the signals of the variable frequency dividing means and the reference signal generating means and outputting a phase error signal, and calculating the phase error signal from the phase comparing means. A configuration for controlling the oscillation frequency is fed back to said voltage controlled oscillator means via a loop filter,
The control means is configured to perform carrier sense detection by the carrier sense means in a state in which the variable frequency dividing means is selected to be a frequency-divided fraction system. Then, the carrier sense detection can be performed by the carrier sense means in a state where the frequency division and fraction system is selected, so that the time required for carrier sense can be shortened.

The control means switches the variable frequency dividing means to the integer frequency dividing method after performing the carrier sense detection by the carrier sensing means with the variable frequency dividing means selected to the fractional frequency dividing method. The carrier sense detection is performed again by the carrier sense means. Then, carrier sensing can be performed again by the integer frequency division method for actually receiving data.

Further, the carrier sense means includes a carrier squelch means for directly detecting the presence or absence of a carrier based on the level of a signal input to the receiving means, and a carrier presence or absence based on the level of a noise component included in the demodulated signal demodulated by the receiving means. After performing carrier sense detection with the carrier squelch means in a state where the variable frequency dividing means is selected as the fractional frequency dividing method, the control means switches the variable frequency dividing means to the integer frequency dividing method. Thus, the carrier sense detection is performed by the noise squelch means. Then, carrier switching after switching to the integer frequency division method can be performed by the noise squelch method.

The loop filter is constituted by a low-pass filter, and the cut-off frequency is set to be equal to or lower than a switching frequency for switching the frequency of the variable frequency dividing means at a predetermined cycle. Then, a spurious component generated by the switching frequency included in the oscillation frequency of the VCO can be reduced.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

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

In FIG. 1, 1 is an antenna, 2 is transmitting / receiving means, 3 is a VCO, 4 is a variable frequency dividing means for dividing the frequency from the VCO to 1 / N or 1 / (N + 1), and 5 is a phase comparing means. , 6 are frequency dividing means for dividing the input frequency to 1 / M, 7 is a loop filter, 8 is a crystal oscillator, and the frequency dividing means 6 and the crystal oscillator 8 constitute a reference signal generating means. 9 is a fractional frequency division / integer frequency division switching means, 10 is a control means, 11 is a carrier sense means, 12 is a waveform shaping means,
13 is reception data output, 14 is carrier detection output, 15
Is a lock detecting means.

The control means 10 includes a transmitting / receiving means 2 and a VCO 3
And the like, the power supply of the receiving device is turned on intermittently to start the receiving operation. The frequency divider 6 divides the frequency of the signal from the crystal oscillator 8, generates a predetermined reference frequency, for example, 200 kHz, and outputs it to the phase comparator 5. At the beginning of the intermittent operation, the control means 10 keeps the fractional frequency division / integer frequency division switching means 9 in a fractional frequency division state. Therefore, the variable frequency dividing means 4 changes the oscillation frequency of the VCO 3 to 1 / N frequency dividing and 1 / (N + 1) frequency dividing by 1 / (200) under the control of the fractional frequency dividing / integer frequency dividing switching means 9.
(kHz). For example, 1 / (2
It is assumed that the 1 / N frequency division is performed n times and the 1 / (N + 1) frequency division is performed (L−n) times in the L times using the (00 kHz) time as one unit.
Then, the average frequency division number of the variable frequency dividing means 4 is 1 / ((N + 1)
− (N / L)).

Therefore, when the oscillation frequency of the VCO is fv, the output of the variable frequency divider 4 is fo, and the reference frequency is fr, fv
= ((N + 1)-(n / L)) × fr.

If fr = 200 kHz and L = 16, fv can be changed by 200 kHz in 12.5 kHz steps by changing n one by one from 0 to 15. A change of fv of 200 kHz or more can be made by N. As described above, in the fractional frequency division method, although the reference frequency fr is 200 kHz, 12.
Fv can be changed in 5 kHz steps. Since the reference frequency fr is as high as 200 kHz, the convergence of the frequency fv can be accelerated. The lock detecting means 15 detects that the phase error of the phase comparing means 5 has entered a predetermined range. After starting the intermittent operation, the control means 10 monitors the signal from the lock detection means 15 and when detecting the signal from the lock detection means 15, activates the carrier sense means 11 to perform the carrier sense operation.

If there is no carrier, the control means 10
Turns off the power and ends the receiving operation. On the other hand, if there is a carrier, the control means 10 switches the fractional frequency division / integer frequency division switching means 9 to integer frequency division. Then, the fractional frequency dividing / integer frequency dividing switching means 9 controls the frequency dividing number of the variable frequency dividing means 4 to be fixed at 1 / N, and at the same time, divides the frequency of the frequency dividing means 6 so that the output of the frequency dividing means 6 becomes 12.5 kHz. Switch numbers. As a result, a normal integer frequency division type PLL operation is performed. Then, the data receiving operation is started, and the demodulated output from the transmitting / receiving means 2 is converted into a data signal by the waveform shaping means 12 and output.

The control unit 10 may have the following functions. After switching to the integer frequency division method, the output of the lock detecting means 15 is monitored again, and when the signal from the lock detecting means 15 is detected, the carrier sensing means 11 is operated again to perform the carrier sensing operation. If there is no carrier, the control means 10 turns off the power and ends the receiving operation. On the other hand, if there is a carrier, the data receiving operation is started, and the demodulated output from the transmitting / receiving means 2 is converted into a data signal by the waveform shaping means 12 and output.

The loop filter 7 is composed of a low-pass filter, and the reference frequency fr is different between the fractional frequency division method and the integer frequency division method. It is controlled so that it is switched in the case of the lap method. In the case of the fractional frequency division method, a spurious signal of 12.5 kHz which is the reference frequency fr in the case of the integer frequency division method is generated. Therefore, in order to eliminate it, the cutoff frequency is set to 1
If the frequency is set to 2.5 kHz or less, malfunction of carrier sense due to spurious components can be prevented in carrier sense in the fractional frequency division method.

(Embodiment 2) FIG. 2 is a block diagram of a receiving apparatus according to Embodiment 2 of the present invention.

In FIG. 2, the same functional blocks as those in FIG. 1 are given the same numbers. The difference from FIG. 1 is that the carrier sense unit 11 in FIG.
-1 and carrier squelch means 11-2 and switch means 16. The basic operation is the same as that of the first embodiment shown in FIG. 1, and a device for detecting the carrier sense operation is provided. The carrier sensing operation in the fractional frequency division mode is performed using the carrier squelch means 11-2. Therefore, in the state of the fractional frequency division system, the switch means 16 is connected to the carrier squelch means 11.
-2 is output. Carrier squelch means 11-2
Rectifies the output of the intermediate frequency signal stage of the transmission / reception means 2 and converts it to a DC level to detect the presence or absence of a carrier. That is, since the presence or absence of the intermediate frequency signal is detected, the time required for the rectified DC signal to rise can be reduced by reducing the time constant of the rectification, so that the time for carrier sense detection can be shortened.

Next, when the carrier is detected by the carrier squelch means 11-2, switching to the integer frequency division system is performed and carrier sense is performed again, as in the first embodiment. At this time, the noise sensing means 11-1 is used as the carrier sensing means. Therefore, the switch means 16 is connected to the noise kerch means 11-.
1 is output. The noise squelch means 11-1
The noise component included in the demodulated output of the transmission / reception means 2 is taken out, rectified and converted into a DC component, and the magnitude of the noise component is detected. When a signal is received by the transmission / reception means 2, the noise component included in the demodulated output is suppressed, and the signal-to-noise ratio is improved. Therefore, when the noise component is below a predetermined level, it can be detected that there is a carrier. The noise squelch means 11-1 needs a large time constant to rectify noise components and to prevent jitter. For this reason, the rise time becomes long, and it takes time to detect carriers. However, when noise is input to the transmission / reception means 2, the carrier squelch means 11-2 erroneously detects the noise, but the noise squelch means 11-1 judges that the noise is noise and does not perform carrier sense. Since the carrier sensing by the noise squelch means 11-1 performs the carrier sensing operation accurately, it is suitable for the carrier sensing in the integer frequency division method in which the carrier sensing may take some time.

[0021]

As described above, according to the present invention, receiving means, carrier sensing means for detecting whether a signal input to the receiving means is at or above a predetermined level, and carrier sensing means for the carrier sensing means Control means for controlling the timing at which the signal is received, voltage-controlled oscillating means whose oscillation frequency changes with a voltage applied to select a frequency to be received by the receiving means, and variable for dividing the oscillation frequency of the voltage-controlled oscillating means. Frequency dividing means and integer frequency division / fraction frequency division selecting means for selecting a fraction frequency dividing method for switching the frequency dividing number of the variable frequency dividing means at a predetermined cycle or an integer frequency dividing method fixed at a predetermined frequency dividing number Reference signal generating means, phase comparing means for comparing the phases of the signals of the variable frequency dividing means and the reference signal generating means and outputting a phase error signal, and the phase from the phase comparing means The difference signal is fed back to the voltage-controlled oscillating means via a loop filter to control the oscillating frequency. Since the configuration is such that the carrier sense is detected, the time required for the carrier sense can be shortened, and the power consumption in the intermittent reception operation can be reduced.

Further, the control means performs carrier sense detection by the carrier sense means in a state where the variable frequency dividing means is selected to the fractional frequency dividing method, and then switches the variable frequency dividing means to the integral frequency dividing method. Since carrier sense detection is performed again by the carrier sense means, carrier sense can be performed again by an integer frequency division method for actually receiving data, and erroneous detection of carrier sense can be prevented. Therefore, power consumption can be reduced.

The carrier sensing means includes a carrier squelch means for directly detecting the presence or absence of a carrier based on the level of a signal input to the receiving means, and a carrier presence or absence based on the level of a noise component included in the demodulated signal demodulated by the receiving means. After performing carrier sense detection with the carrier squelch means in a state where the variable frequency dividing means is selected as the fractional frequency dividing method, the control means switches the variable frequency dividing means to the integer frequency dividing method. Therefore, since the carrier sense detection is performed by the noise squelch means,
Carrier sensing after switching to the integer frequency division method can be performed by the noise squelch method, and erroneous detection of carrier sense due to noise can be more accurately prevented. Therefore, power consumption can be reduced.

Further, the loop filter is constituted by a low-pass filter, and the cutoff frequency is set to be equal to or lower than the switching frequency for switching the frequency of the variable frequency dividing means at a predetermined cycle. Spurious components generated by the frequency can be reduced, and erroneous detection of carrier sense due to spurious components can be prevented. Therefore, power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a receiving device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a receiving apparatus according to a second embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna 2 Transmitting / receiving means 3 VCO 4 Variable frequency dividing means 5 Phase comparing means 6 Frequency dividing means 7 Loop filter 8 Crystal oscillator 9 Fractional frequency dividing / integer frequency dividing switching means 10 Control means 11 Carrier sensing means 11-1 Noise squelch means 11 -2 carrier squelch means 12 waveform shaping means 13 received data output 14 carrier sense output 15 lock detecting means

Claims (4)

[Claims] 1. A receiving means, a carrier sensing means for detecting whether a signal input to the receiving means is at or above a predetermined level, a control means for controlling timing of carrier sensing by the carrier sensing means, Voltage-controlled oscillating means whose oscillation frequency changes by a voltage applied to select a frequency to be received by the receiving means, variable frequency dividing means for dividing the oscillation frequency of the voltage-controlled oscillating means,
Integer division / fraction division selection means for selecting between a fractional frequency division method for switching the frequency division number of the variable frequency division means at a predetermined cycle or an integer frequency division method fixed to a predetermined frequency division number, and reference signal generation Means, a phase comparison means for comparing the phases of the signals of the variable frequency dividing means and the reference signal generation means and outputting a phase error signal, and the phase error signal from the phase comparison means through the loop filter to the voltage. A receiving means configured to perform a carrier sense detection by the carrier sensing means in a state where the variable frequency dividing means is selected to be a frequency division / fraction system by feeding back to the control oscillation means. apparatus. 2. The control means switches the variable frequency dividing means to an integer frequency dividing method after performing carrier sense detection by the carrier sensing means with the variable frequency dividing means selected to a fractional frequency dividing method. 2. The receiving apparatus according to claim 1, wherein said carrier sense means performs carrier sense detection again. 3. The carrier sense means includes: a carrier squelch means for directly detecting presence / absence of a carrier based on a level of a signal input to the reception means; and a carrier presence / absence detection based on a level of a noise component included in a demodulated signal demodulated by the reception means. After performing carrier sense detection with the carrier squelch means in a state where the variable frequency dividing means is selected as the fractional frequency dividing method, the control means switches the variable frequency dividing means to the integer frequency dividing method. 3. The receiver according to claim 2, wherein said noise squelch means performs carrier sense detection. 4. A loop filter comprising a low-pass filter, wherein a cutoff frequency is set to a switching frequency for switching the frequency of the variable frequency dividing means at a predetermined cycle.
The receiving device according to any one of claims 1 to 3.