JP2011004287A - Wireless receiving circuit and switch apparatus using the same - Google Patents

Abstract

A radio receiving circuit capable of reducing a shift in an intermediate frequency without increasing power consumption and increasing receiving sensitivity and a switch device using the same.
When a temperature sensor TS detects an ambient temperature around a local oscillating unit and a receiving unit receives a radio signal, a correction processing unit CAL detects a voltage value detected by a voltage detecting unit VS and a storage unit. Based on the temperature / voltage relation information stored in 211, the duty ratio used in the pulse signal generation unit PWM-GEN is set, and the frequency of the oscillation signal generated in the local oscillator 22 is corrected.
[Selection] Figure 3

Description

  The present invention relates to a radio reception circuit having a local oscillator and controlling the oscillation frequency of the local oscillator by a PWM signal.

  FIG. 8 is a block diagram illustrating a configuration of a wireless reception circuit according to the background art. In FIG. 8, a radio wave transmitted from a radio transmission device (not shown) is converted into an electric signal on a circuit by an antenna ANT. Then, after the electric signal is amplified by the low noise amplifier LNA, unnecessary frequency components are removed by the high frequency filter RF-FLT. The output signal of the high frequency filter RF-FLT is mixed with the local oscillation signal oscillated by the local oscillator OSC in the mixer MIX.

  An IF (Intermediate Frequency) signal output from the mixer MIX passes through the IF filter IF-FLT, is amplified by the IF amplifier IF-AMP, is demodulated by the demodulator DMOD, and is output to the microcomputer MC. Is done. The oscillation frequency of the local oscillator OSC depends on the capacitance of the variable capacitor VC. Further, the capacitance of the variable capacitor VC depends on the magnitude of the DC voltage applied to the variable capacitor VC.

  The DC voltage applied to the variable capacitor VC is generated by smoothing a PWM signal generated from a PWM (Pulse Width Modulation) signal generator PWM-GEN in the microcomputer MC by a low-pass filter LPF. Thereby, in the PWM signal generation unit PWM-GEN, the oscillation frequency of the local oscillator OSC is adjusted by appropriately adjusting the ratio between the pulse width of the PWM signal and the pulse period, that is, the duty ratio ( (See FIG. 9).

  Such adjustment of the oscillation frequency of the local oscillator OSC is performed in the inspection process before product shipment, and the duty ratio of the PWM signal is fixedly set for each individual receiver. .

  Patent Document 1 discloses a technique for finely adjusting a reception frequency by changing a tuning voltage by controlling a PWM signal of a remote control receiver while receiving a carrier wave transmitted from a remote control transmitter. It is shown.

Japanese Utility Model Publication No. 5-39034

  However, in the conventional radio receiving circuit shown in FIG. 8, the oscillation frequency of the local oscillator OSC is adjusted only at the time of product shipment, and thereafter the duty ratio of the PWM signal remains fixed. In general, it is known that the oscillation frequency of the local oscillation circuit OSC varies according to the ambient temperature around the local oscillation circuit OSC (see FIG. 10). Therefore, when the oscillation frequency of the local oscillation circuit OSC fluctuates due to a change in the ambient temperature around the wireless reception circuit, the IF frequency obtained as the difference between the oscillation frequency of the local oscillation circuit OSC and the transmission frequency of the wireless transmission device is Deviation from the design center value. Similarly, if the transmission frequency of the wireless transmission device fluctuates due to a change in ambient temperature around the wireless transmission device (not shown), the IF frequency will deviate from the design center value. In order to cope with this, since it is necessary to widen the pass band of the IF filter IF-FLT and to widen the characteristics of the demodulator DMOD, there is a disadvantage that the reception sensitivity is lowered.

  Further, in the prior art of Patent Document 1, it is necessary to repeat the adjustment of the PWM signal by trial and error until the received signal reaches the peak value, so that the time required for communication becomes long and the usability deteriorates. There was a problem that the power consumption of the system increased.

  An object of the present invention is to provide a radio reception circuit capable of reducing a shift in IF frequency without increasing power consumption and increasing reception sensitivity, and a switch device using the same.

  In order to achieve the above object, the invention according to claim 1 is a reception unit that receives a radio signal, and a local unit that generates an oscillation signal having a local oscillation frequency and changes the frequency of the oscillation signal in accordance with a predetermined control voltage. An oscillation unit, a mixing unit that mixes a reception signal acquired by the reception unit and an oscillation signal generated by the local oscillation unit, converts the reception signal to an intermediate frequency to generate an intermediate frequency signal, and An intermediate frequency filter that filters the intermediate frequency signal generated by the mixing unit, a demodulator that demodulates a signal based on the intermediate frequency signal that has passed through the intermediate frequency filter, and a center voltage of the demodulated output signal output from the demodulator A voltage detection unit that detects a PWM signal, a PWM signal generation unit that generates a PWM signal having a predetermined duty ratio, and a PWM signal generated by the PWM signal generation unit By smoothing, a smoothing unit that generates the control voltage, a temperature detection unit that detects an ambient temperature around the local oscillation unit, a temperature detected by the temperature detection unit, and the intermediate frequency signal are predetermined. When the radio signal is received by the receiving unit and a temperature / voltage relationship storage unit that prestores temperature / voltage relationship information indicating a correspondence relationship with the voltage value detected by the voltage detection unit in the case of frequency The PWM signal generator uses the voltage value detected by the voltage detector, the temperature detected by the temperature detector, and the temperature / voltage relationship information stored in the temperature / voltage relationship storage unit. And a correction processing unit that corrects the frequency of the oscillation signal generated by the local oscillation unit by setting the duty ratio. In the present configuration, the predetermined frequency refers to a design value of the intermediate frequency, and, for example, matches the median value of the frequency band filtered by the intermediate frequency filter.

  According to a second aspect of the present invention, in the wireless reception circuit according to the first aspect, the correction processing unit is detected by the temperature detection unit based on temperature / voltage relationship information stored in the temperature / voltage relationship storage unit. If the wireless signal is received by the receiving unit when the voltage value corresponding to the current temperature is set as a target voltage and the duty ratio is set to the Nth duty ratio (N is a natural number), The voltage detection unit detects the Nth center voltage, and after changing the duty ratio from the Nth duty ratio to the N + 1th duty ratio so that the Nth center voltage changes in a direction approaching the target voltage, the voltage A value obtained by detecting a (N + 1) th center voltage by a detection unit and dividing a difference between the (N + 1) th center voltage and the Nth center voltage by a difference between the (N + 1) th duty ratio and the Nth duty ratio. An N + 2th duty ratio obtained by changing the N + 1 duty ratio by a value obtained by dividing the difference between the N + 1 center voltage and the target voltage by the change rate, as a change rate of the center voltage with respect to the duty ratio. By setting as a new duty ratio in the PWM signal generation unit, the frequency of the oscillation signal generated in the local oscillation unit is corrected.

  According to a third aspect of the present invention, in the radio reception circuit according to the second aspect, the correction processing unit repeatedly corrects the frequency of the oscillation signal generated by the local oscillation unit until the N reaches a predetermined number of times. It is characterized by performing. In this configuration, the predetermined number is the number of correction processes that can be estimated by repeating the correction process of the oscillation frequency so that the center voltage is sufficiently close to the target voltage so that it can be approximated without any practical problem. It can be determined by etc.

  According to a fourth aspect of the present invention, in the wireless reception circuit according to the second aspect, the correction processing unit causes the local oscillating unit until the difference between the Nth center voltage and the target voltage converges below a predetermined threshold value. The correction of the frequency of the oscillation signal generated in (1) is executed. In the present configuration, the predetermined threshold value is a value that can be determined to be close enough that the center voltage can be approximated to the target voltage without any practical problem, and can be determined in advance by experiments or the like.

  According to a fifth aspect of the present invention, in the wireless reception circuit according to any one of the first to fourth aspects, the duty ratio is set so as to cancel the change in the frequency of the oscillation signal accompanying the change in the environmental temperature. A temperature / duty ratio relation storage unit for preliminarily storing temperature / duty ratio relation information indicating a value, and generating a PWM signal having a duty ratio corresponding to the temperature detected by the temperature detection unit from the PWM signal generation unit; It is characterized by waiting for a radio signal in a state where

  According to a sixth aspect of the present invention, there is provided a wireless receiving circuit according to any one of the first to fifth aspects, an operation handle operated by a user, a switch element that opens and closes a power supply path to a load, and the wireless A switch device comprising: a switch control unit that opens and closes the switch element in accordance with a signal demodulated by the demodulation unit in the reception circuit and an operation input by the user to the operation handle.

  According to the first aspect of the present invention, when a radio signal is received by the receiving unit, the central voltage value detected by the voltage detecting unit and the temperature detected by the temperature detecting unit and the temperature / voltage relation storage unit are stored. The duty ratio used in the PWM signal generation unit is set based on the temperature-voltage relation information. The duty ratio set at this time corresponds to the temperature detected by the temperature detector. Then, the PWM signal output from the PWM signal generation unit is smoothed by the smoothing unit, so that a control voltage having a voltage corresponding to the set duty ratio is generated. The oscillation frequency of the local oscillator is generated according to the control voltage. Changes. As a result, the oscillation frequency of the local oscillator is corrected without trial and error, and the shift of the intermediate frequency is reduced. As a result, the passband of the intermediate frequency filter that filters the intermediate frequency signal can be narrowed without increasing the power consumption, or the characteristics of the demodulator can be narrowed. It can be easily improved.

  According to the invention of claim 2, the Nth center voltage detected by the voltage detector corresponding to the Nth duty ratio, and the N + 1th center voltage detected by the voltage detector corresponding to the N + 1 duty ratio Thus, the rate of change of the center voltage with respect to the duty ratio is obtained. Then, by newly setting the (N + 2) duty ratio based on this rate of change, the local oscillator can be accurately detected without being affected by the degree of temperature change or variations in the characteristics of the circuits constituting the specific device. It is possible to correct the oscillation frequency and reduce the deviation of the intermediate frequency. Even when the change rate calculation result includes an error due to a center voltage detection error or a calculation rounding error, the center voltage detected by the voltage detection unit is set by repeating the above correction processing. It becomes possible to approach the target voltage, and it is possible to correct the oscillation frequency of the local oscillator with high accuracy and reduce the deviation of the intermediate frequency. As a result, the pass band of the intermediate frequency filter can be further narrowed, or the characteristics of the demodulator can be narrowed, and the reception sensitivity of the radio receiving circuit can be easily improved.

  According to the third aspect of the present invention, when the oscillation frequency correction process is repeated a predetermined number of times and it can be estimated that the center voltage is sufficiently close to the target voltage to be practically satisfactory, the oscillation frequency correction process is performed. Since the operation is stopped, the correction process is not repeated more than necessary, and the power consumption of the apparatus can be further reduced.

  According to the invention of claim 4, the center voltage and the target voltage are directly compared, and when it is determined that both are sufficiently close enough to be approximated without any problem in practice, the oscillation frequency correction process is stopped. As in the case of the present invention, the correction process is not repeated more than necessary, and the power consumption of the apparatus can be further reduced.

  According to the fifth aspect of the present invention, it is possible to reduce the shift of the local oscillation frequency due to the influence of the temperature even when the receiving unit is not receiving the radio signal. Thereby, the pass band of the intermediate frequency filter can be further narrowed, or the characteristic of the demodulator can be narrowed, and the reception sensitivity of the radio reception circuit can be easily improved.

  According to the sixth aspect of the present invention, in the switch device in which the power supply path to the load is opened and closed according to the radio signal received by the radio reception circuit, the reception sensitivity of the radio reception circuit can be increased. It is possible to obtain a highly reliable switch device without an increase in

The figure which shows the structure of the load control system provided with the switch apparatus by one Embodiment of this invention. The block diagram which shows the structure of the same switch apparatus. The block diagram which shows the structure of the radio | wireless receiving circuit by one Embodiment of this invention. The figure which shows the relationship between the ambient environment temperature of a local oscillator, and a target voltage. The flowchart which shows operation | movement of each part when a correction | amendment process part sets a duty ratio. The figure which shows the relationship between a duty ratio and the center voltage detected by a voltage detection part. The figure which shows the relationship between the voltage detected by an intermediate frequency and a voltage detection part. The block diagram which shows the structure of the conventional radio | wireless receiver. The figure which shows the relationship between a duty ratio and the local oscillation frequency of a local oscillator. The figure which shows the surrounding environment temperature of a local oscillator, and the relationship of a local oscillation frequency.

  A radio reception circuit and a switch device using the same according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a switch device using a wireless receiving circuit according to an embodiment of the present invention and a load control system including the switch device. The load control system includes a transmitter W1 that transmits a radio signal, a switch device 1 that blinks the illumination load LD according to the radio signal, and the like. The switch device 1 is connected in series with the illumination load LD and connected to a power source (commercial AC power source) AC. The load is not limited to the illumination load LD such as a fluorescent lamp or a fluorescent lamp electronic ballast, but may be other illumination load or a load other than the illumination load.

  An operation handle 10 that is operated by a user is provided on the front surface of the switch device 1.

  FIG. 2 is a block diagram showing an example of the configuration of the switch device 1 shown in FIG. The switch device 1 includes a wireless reception circuit 2, a switch element 11, a switch control unit 12, and a switch input unit 13.

  The switch input unit 13 is configured using, for example, a tact switch (light touch switch) disposed so as to be interlocked with the operation handle 10. The switch element 11 is a switch element such as a triac. The switch element 11 opens and closes a power supply path to the illumination load LD in accordance with a control signal from the switch control unit 12.

  The switch control unit 12 is configured using, for example, a microcomputer. Then, the switch control unit 12 opens and closes the switch element 11 according to the signal transmitted from the transmitter W1 and received by the wireless reception circuit 2 and the on / off signal output from the switch input unit 13.

  FIG. 3 is a block diagram showing an example of the configuration of the wireless reception circuit 2 shown in FIG. 3 includes an antenna ANT, a low noise amplifier LNA, a high frequency filter RF-FLT, a mixer MIX (mixing unit), an IF filter IF-FLT, an IF amplifier IF-AMP, a demodulation unit DMOD, and a temperature sensor TS. (Temperature detection unit), a low-pass filter LPF (smoothing unit), a control unit 21, and a local oscillator 22.

  The radio signal transmitted from the transmitter W1 is received by the antenna ANT, the low noise amplifier LNA, and the high frequency filter RF-FLT, and is output to the mixer MIX as the received signal S2. The mixer MIX mixes the received signal S2 and the local oscillation signal S1, converts it to an IF signal S3 (intermediate frequency signal), and outputs it to the IF filter IF-FLT. The IF filter IF-FLT filters the IF signal S3 output from the mixer MIX.

  The IF signal output from the mixer MIX passes through the IF filter IF-FLT and is amplified by the IF amplifier IF-AMP. Then, the signal amplified by the IF amplifier IF-AMP, that is, the signal S4 based on the IF signal is demodulated by the demodulator DMOD and output to the controller 21 as a demodulated signal S5. The demodulator DMOD outputs the center voltage S6 of the demodulated signal S5 to the controller 21. The control unit 21 outputs the signal S5 demodulated by the demodulation unit DMOD to the switch control unit 12 shown in FIG. In this case, the antenna ANT, the low noise amplifier LNA, and the high frequency filter RF-FLT correspond to an example of a receiving unit.

  The low-pass filter LPF filters a low-frequency signal among the signals output from the control unit 21 and outputs the filtered low-frequency signal to the parallel resonance circuit 23 of the local oscillator 22.

  The control unit 21 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. A voltage detection unit VS, a pulse signal generation unit PWM-GEN (PWM signal generation unit), a storage unit 211, and peripheral circuits thereof. The voltage detector VS detects the center voltage of the demodulated output signal output from the demodulator DMOD. The storage unit 211 is configured using a nonvolatile storage element such as an EEPROM (Electrically Erasable and Programmable Read Only Memory) or a part of the ROM, for example.

  The control unit 21 functions as the correction processing unit CAL by executing a control program stored in the ROM, for example. The control unit 21 is configured using, for example, a one-chip microcomputer. Further, the switch control unit 12 and the control unit 21 may be configured integrally using the same microcomputer.

  The local oscillator 22 includes a parallel resonance circuit 23, an output circuit 24, and a coupling capacitor C3. The parallel resonance circuit 23 is configured by connecting a series circuit of a capacitor C1 and a variable capacitor VC (variable capacitor diode), a capacitor C2, and an inductor L in parallel. A connection point between the variable capacitor VC, the capacitor C2, and the inductor L is connected to the ground. A DC voltage Vvf output from the low-pass filter LPF is applied to a connection point P1 between the variable capacitor VC and the capacitor C1.

  The capacitance of the variable capacitor VC changes according to the DC voltage Vvf applied to the connection point P1. Then, the oscillation frequency of the parallel resonance circuit 23 changes according to the capacitance of the variable capacitor VC.

  The output circuit 24 includes a transistor Tr1, a resistor R1, and capacitors C4, C5, and C6. The base of the transistor Tr1 is connected to a connection point P2 between the capacitors C1 and C2 and the inductor L in the parallel resonance circuit 23 via the capacitor C3. The base of the transistor Tr1 is connected to the ground via resonance capacitors C4 and C5, and the connection point of the capacitors C4 and C5 is connected to the emitter of the transistor Tr1. The emitter of the transistor Tr1 is connected to the ground via the resistor R1.

  A DC power supply voltage Vcc is supplied to the collector of the transistor Tr1. The emitter of the transistor Tr1 is connected to the mixer MIX via the capacitor C6. Then, the output circuit 24 amplifies the resonance frequency component of the parallel resonance circuit 23 and outputs it as a local oscillation signal S1 to the mixer MIX.

  Then, since the resonance frequency of the parallel resonance circuit 23 changes according to the capacitance of the variable capacitor VC, the frequency of the local oscillation signal S1, that is, the local oscillation frequency changes according to the DC voltage Vvf. .

  In addition, since the characteristics of each part of the local oscillator 22 change depending on the temperature, the local oscillation frequency varies according to the temperature of the local oscillator 22. Therefore, the ambient temperature around the local oscillator 22 measured by the temperature sensor TS and the duty ratio Dr that cancels the fluctuation of the local oscillation frequency corresponding to the ambient environment temperature are stored as temperature / duty ratio relation information. 211.

  The temperature sensor TS is disposed in the vicinity of the local oscillator 22, detects the ambient temperature around the local oscillator 22, or the temperature T of the local oscillator 22, and outputs a voltage corresponding to the temperature T to the correction processing unit CAL. .

  The pulse signal generation unit PWM-GEN outputs the pulse signal PWM to the low-pass filter LPF with the period and the pulse width set by the correction processing unit CAL. That is, the pulse signal generation unit PWM-GEN outputs the pulse signal PWM having the duty ratio Dr set by the correction processing unit CAL to the low-pass filter LPF.

  The low-pass filter LPF smoothes the pulse signal PWM and outputs it to the parallel resonance circuit 23 of the local oscillator 22 as a DC voltage Vvf (control voltage of the local oscillator 22). In this case, assuming that the high level voltage of the pulse signal PWM is the voltage Vcc, Vvf = Vcc × Dr. Therefore, the correction processing unit CAL can adjust the DC voltage Vvf and adjust the frequency of the local oscillation signal S1 by adjusting the duty ratio Dr.

  The storage unit 211 has a duty that cancels out the variation in the local oscillation frequency corresponding to the ambient temperature around the local oscillator 22 measured by the temperature sensor TS and the variation in the local oscillation frequency corresponding to the ambient environment temperature. Temperature / duty ratio relationship information indicating a correspondence relationship with the ratio Dr is stored in advance. Further, in the storage unit 211, as shown in FIG. 4, when the ambient temperature around the local oscillator 22 and the intermediate frequency signal have a predetermined frequency (design center value), they are detected by the voltage detection unit VS. Temperature / voltage relationship information indicating a correspondence relationship with the voltage value is stored in advance. That is, the storage unit 211 corresponds to the temperature / voltage relationship storage unit described in claim 1.

  The correction processing unit CAL generates a pulse signal so as to cancel the amount of change in the local oscillation frequency corresponding to the temperature T detected by the temperature sensor TS based on the temperature / duty ratio relation information stored in the storage unit 211. The duty ratio Dr set in the section PWM-GEN is adjusted.

  Further, the correction processing unit CAL, when a radio signal is received by the receiving unit, the voltage value detected by the voltage detecting unit VS, the temperature detected by the temperature detecting unit, and the temperature stored in the storage unit 211 The frequency of the oscillation signal generated by the local oscillator 22 is corrected by setting the duty ratio used by the pulse signal generation unit PWM-GEN based on the voltage relation information.

  Next, the operation of each unit when the correction processing unit CAL sets the duty ratio used in the pulse signal generation unit PWM-GEN will be described with reference to FIGS. In FIG. 5, first, after setting the number of repetitions N (N is a natural number) to 1 (# 1), the control unit 21 sets the duty ratio to the first duty ratio D1 in the pulse signal generation unit PWM-GEN ( # 2) The wireless reception circuit 2 enters a reception standby state (# 3). Here, the first duty ratio D1 is, for example, the frequency of the intermediate frequency signal is a predetermined frequency when a wireless signal having a preset reference frequency is received at the center temperature of the environmental temperature fluctuation range that is assumed in advance. It is determined so as to obtain a local oscillation frequency of (design center value). Next, the temperature sensor TS detects the ambient temperature T around the local oscillator 22 (# 4), and the correction processing unit CAL refers to temperature / voltage related information (see FIG. 4) stored in the storage unit 211. Then, the target voltage Vt corresponding to the current environmental temperature T is set (# 5). When a radio signal is received by the receiving unit (YES in # 6), the first center voltage V1 is detected by the voltage detecting unit VS (# 7).

  Then, the control unit 21 changes the duty ratio in the pulse signal generation unit PWM-GEN from the first duty ratio D1 to the second duty ratio D2 so that the first center voltage V1 changes in a direction approaching the target voltage Vt. (# 8), the second center voltage V2 is detected by the voltage detector VS (# 9). As a result, the first center voltage V1 at the first duty ratio D1 and the second center voltage V2 at the second duty ratio D2 are obtained, and the relationship between the duty ratio and the center voltage detected by the voltage detector shown in FIG. 6 is obtained. It is done. Note that the second duty ratio D2 is such that the second center voltage V2 is closer to the target voltage Vt than the first center voltage V1 (in FIG. 6, since the first center voltage V1 is smaller than the target voltage Vt, The center voltage V2 is set to be larger than the first center voltage V1). In FIG. 6, the relationship between the duty ratio and the center voltage is not strictly a linear function (straight line), but the second duty is such that the duty ratio and the center voltage can be approximated by a linear function. The second duty ratio D2 is set so that the absolute value of the difference between the ratio D2 and the first duty ratio D1 is sufficiently small. The second duty ratio D2 is set so that the IF signal S3 output from the mixer MIX does not deviate from the IF filter IF-FLT pass frequency band. For example, the second duty ratio D2 is set so that the difference between the second duty ratio D2 and the first duty ratio D1 is a constant value. The second duty ratio D2 may be set so that the difference between the second duty ratio D2 and the first duty ratio D1 is a function of the difference between the first center voltage V1 and the target voltage Vt. Furthermore, the second duty ratio D2 may be set so that the difference between the second duty ratio D2 and the first duty ratio D1 is a function of the temperature detected by the temperature sensor TS.

  The slope of the linear function in FIG. 6, that is, the rate of change A of the center voltage with respect to the duty ratio varies depending on the ambient temperature around the transmitter W1 and the local oscillator 22. Therefore, the correction processing unit CAL calculates the change rate A of the center voltage with respect to the duty ratio (# 10). The change rate A of the center voltage can be calculated by dividing the difference between the second center voltage V2 and the first center voltage V1 by the difference between the second duty ratio D2 and the first duty ratio D1. Thereby, the change rate A adapted to the ambient temperature around the transmitter W1 and the local oscillator 22 can be obtained.

  Further, the correction processing unit CAL calculates the third duty ratio D3 (# 11) and sets it as a new duty ratio in the pulse signal generation unit PWM-GEN (# 12). The third duty ratio D3 is calculated by subtracting a value obtained by dividing the difference between the second center voltage V2 and the target voltage Vt by the change rate A from the second duty ratio D2.

  Further, the correction processing unit CAL detects the third center voltage V3 by the voltage detection unit VS after changing the duty ratio in the pulse signal generation unit PWM-GEN to the third duty ratio D3 (# 13). When third center voltage V3 approaches sufficiently to target voltage Vt and V3-Vt converges (YES in # 14), radio signals are further received. When the reception of the radio signal is completed (# 15), the duty ratio is initialized (# 16), and the process is terminated.

  On the other hand, when the third center voltage V3 is away from the target voltage Vt, that is, when V3-Vt does not converge (NO in # 14), N is incremented by 1 (# 21), the process returns to # 11, and # 12 , # 13, the fourth duty ratio D4 is calculated using the third duty ratio D3 and the third center voltage V3. As described above, when VN-Vt does not converge, the loops of # 21, # 11, # 12, and # 13 are repeated, so that D4, D5. . . Are sequentially calculated, and the center voltage V4 and the center voltage V5 are sequentially detected. The center voltage VN detected in this way approaches the target voltage Vt as the calculation is repeated (N increases), and the intermediate frequency IF can be brought closer to the design center value (see FIG. 7).

  Whether or not VN−Vt has converged in # 14 can be determined by comparing the absolute value of VN−Vt with a predetermined threshold value. The threshold value can be determined empirically according to the communication environment or the like. As another criterion for determining whether or not VN−Vt has converged, the number of times the loop of # 21, # 11, # 12, and # 13 is repeated, that is, a new duty ratio is set, and the frequency correction processing is performed. It is also possible to make a determination based on the number of times that is executed. That is, when the number of repetitions of the loops of # 21, # 11, # 12, and # 13 reaches a predetermined number that is determined empirically, it can be considered that VN−Vt has converged. This is because the center voltage VN approaches the target voltage Vt by repeating the loop of # 21, # 11, # 12, and # 13 as described above.

  As described above, according to the wireless reception circuit 2 of the present embodiment, when a wireless signal is received by the reception unit, the center voltage value detected by the voltage detection unit VS and the temperature / value stored in the storage unit 211 are determined. A duty ratio used in the pulse signal generation unit PWM-GEN is set based on the voltage relation information. The duty ratio set at this time corresponds to the temperature detected by the temperature sensor TS. Then, the PWM signal output from the pulse signal generation unit PWM-GEN is smoothed by the low-pass filter LPF, so that a control voltage having a voltage corresponding to the set duty ratio is generated. The oscillation frequency of the oscillator 22 changes. As a result, the oscillation frequency of the local oscillator 22 is corrected without trial and error, and the deviation of the intermediate frequency IF is reduced. As a result, the pass band of the IF filter IF-FLT that filters the intermediate frequency signal S3 can be narrowed without increasing the power consumption, or the characteristic of the demodulator DMOD can be narrowed. It is possible to easily improve the reception sensitivity.

  In addition, the Nth center voltage detected by the voltage detection unit VS corresponding to the Nth duty ratio and the N + 1th center voltage detected by the voltage detection unit VS corresponding to the N + 1th duty ratio, with respect to the duty ratio A change rate A of the center voltage is obtained. Then, by newly setting the (N + 2) duty ratio based on the rate of change A, the local oscillator can be obtained with high accuracy without being affected by the degree of temperature change and variations in characteristics of the circuits constituting the specific device. It is possible to correct the oscillation frequency of 22 and reduce the deviation of the intermediate frequency IF. Even when the change rate calculation result includes an error due to a center voltage detection error or a calculation rounding error, the center voltage detected by the voltage detection unit VS is set by repeating the above correction process. Thus, the oscillation frequency of the local oscillator 22 can be corrected with high accuracy, and the deviation of the intermediate frequency IF can be reduced. As a result, the pass band of the IF filter IF-FLT can be further narrowed, or the characteristic of the demodulator DMOD can be narrowed, and the reception sensitivity of the radio receiving circuit can be easily improved.

  The present invention is not limited to the configuration of the above embodiment, and the correction processing unit CAL is based on the temperature / voltage relation information stored in the storage unit 211 according to at least the temperature detected by the temperature sensor TS. Thus, it is sufficient that the duty ratio used in the pulse signal generation unit PWM-GEN is set. Further, the present invention can be modified in various ways. For example, based on the temperature detected in # 4 in FIG. 5 and the temperature / duty ratio relation information stored in advance in the storage unit 211, the environmental temperature varies. The first duty ratio D1 may be constantly updated so as to cancel out the fluctuation of the local oscillation frequency due to. Thereby, even when the receiving unit is not receiving a radio signal, it is possible to reduce the deviation of the local oscillation frequency due to the influence of temperature, and further narrow the pass band of the IF filter, or the characteristics of the demodulating unit DMOD. Can be narrowed. Further, when there is a margin in the processing capability of the correction processing unit CAL, the change rate A may be calculated by returning from # 21 to # 10. In this case, as the detected center voltage VN approaches the target voltage Vt, the change rate A is corrected. Therefore, the oscillation frequency of the local oscillator 22 is corrected with higher accuracy, and the deviation of the intermediate frequency IF is corrected. It becomes possible to reduce. Further, when it has been clarified in advance through experiments or the like that the deviation of the intermediate frequency IF can be sufficiently reduced in practice by setting the third duty ratio D3, the duty ratio is set to the third duty ratio D3 in # 12. Thereafter, # 13 and # 14 may be omitted and a radio signal may be received. Further, the demodulator DMOD is configured to output the demodulated signal S5 and the center voltage S6 of the demodulated signal S5, but the center voltage generator may be configured as another block.

DESCRIPTION OF SYMBOLS 1 Switch apparatus 2 Wireless receiver circuit 22 Local oscillation part (local oscillator)
211 storage unit (temperature / voltage relationship storage unit, temperature / duty ratio relationship storage unit)
ANT antenna (receiver)
LNA low noise amplifier (receiver)
RF-FLT High-frequency filter RF-FLT (receiver)
MIX mixer (mixing unit)
IF-FLT IF filter (intermediate frequency filter)
DMOD demodulator TS temperature sensor (temperature detector)
LPF Low pass filter (smoothing part)
VS voltage detector PWM-GEN pulse signal generator (PWM signal generator)
CAL correction processing section

Claims (6)

A receiver for receiving a radio signal;
A local oscillation unit that generates an oscillation signal having a local oscillation frequency and changes the frequency of the oscillation signal according to a predetermined control voltage;
Mixing a reception signal acquired by the reception unit and an oscillation signal generated by the local oscillation unit, converting the reception signal to an intermediate frequency to generate an intermediate frequency signal; and
An intermediate frequency filter for filtering the intermediate frequency signal generated by the mixing unit;
A demodulator that demodulates a signal based on the intermediate frequency signal that has passed through the intermediate frequency filter;
A voltage detector for detecting a center voltage of a demodulated output signal output from the demodulator;
A PWM signal generation unit that generates a PWM signal having a predetermined duty ratio;
A smoothing unit that generates the control voltage by smoothing the PWM signal generated by the PWM signal generation unit;
A temperature detection unit for detecting an ambient temperature around the local oscillation unit;
Temperature / voltage relation information indicating in advance a correspondence relationship between the temperature detected by the temperature detection unit and the voltage value detected by the voltage detection unit when the intermediate frequency signal has a predetermined frequency. A voltage-related storage unit;
When the wireless signal is received by the receiver, the voltage value detected by the voltage detector, the temperature detected by the temperature detector, and the temperature / voltage relationship stored in the temperature / voltage relationship storage unit And a correction processing unit configured to correct the frequency of the oscillation signal generated by the local oscillation unit by setting the duty ratio used by the PWM signal generation unit based on the information. circuit. The correction processing unit
A voltage value corresponding to the current temperature detected by the temperature detection unit based on the temperature / voltage relationship information stored in the temperature / voltage relationship storage unit is set as a target voltage,
When the wireless signal is received by the receiving unit when the duty ratio is set to the Nth duty ratio (N is a natural number), the voltage detecting unit detects the Nth center voltage,
The duty ratio is changed from the Nth duty ratio to the N + 1th duty ratio so that the Nth center voltage changes in a direction approaching the target voltage, and then the N + 1 center voltage is detected by the voltage detection unit,
A value obtained by dividing a difference between the N + 1 center voltage and the Nth center voltage by a difference between the N + 1 duty ratio and the Nth duty ratio is obtained as a rate of change of the center voltage with respect to the duty ratio.
The N + 2 duty ratio obtained by changing the N + 1 duty ratio by a value obtained by dividing the difference between the N + 1 center voltage and the target voltage by the change rate is set as a new duty ratio in the PWM signal generation unit. The radio reception circuit according to claim 1, wherein the correction of the frequency of the oscillation signal generated by the local oscillation unit is executed.   The radio reception circuit according to claim 2, wherein the correction processing unit repeatedly executes correction of the frequency of the oscillation signal generated by the local oscillation unit until the N reaches a predetermined number of times.   The correction processing unit performs correction of a frequency of an oscillation signal generated by the local oscillation unit until a difference between the Nth center voltage and the target voltage converges to a predetermined threshold value or less. The wireless receiving circuit according to claim 2. A temperature / duty ratio relationship storage unit that preliminarily stores temperature / duty ratio relationship information indicating a set value of a duty ratio that cancels a change in the frequency of the oscillation signal accompanying a change in the environmental temperature;
5. The wireless signal is awaited in a state in which a PWM signal having a duty ratio corresponding to the temperature detected by the temperature detection unit is generated by the PWM signal generation unit. 6. The wireless receiving circuit according to 1. A radio reception circuit according to any one of claims 1 to 5,
An operation handle operated by a user;
A switch element that opens and closes a power supply path to the load;
A switch device comprising: a switch control unit that opens and closes the switch element in response to a signal demodulated by the demodulation unit in the wireless reception circuit and an operation input by the user to the operation handle.

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