JP2006217020A - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a receiver of which the communication range can be extended by improving the reception sensitivity in configuring an ASK/FSK receiver with weak radio or low power facility. <P>SOLUTION: An impedance matching circuit comprising a varactor diode VC1, an inductor L2, and a capacitor C2 is configured between a SAW band pass filter 2a of the receiver 110 and a high frequency input circuit of a detection IC7. Further, a level detection circuit 8 is connected to an RSSI output terminal of an intermediate frequency amplifier circuit (not shown), and a control voltage for maximizing an output level of the RSSI circuit is stored in a memory 9 by changing the control voltage applied to the varactor diode VC1 while the level detection circuit 8 monitors the RSSI output level in a state where a high frequency signal with a prescribed level is received from an antenna input circuit end. Concurrently with the start of operation of the receiver 110, the control voltage stored in the memory 9 is applied to the varactor diode VC1 via a resistor R1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a reception device for weak wireless or low power equipment, and more particularly to an FM / FSK reception device that improves reception sensitivity by correcting variations in circuit constants with reference to RSSI output.

Conventionally, short-distance FM voice communication and ASK / FSK data communication using weak radio or low-power radio do not require a license to use a frequency for operating a radio station, and can configure a communication system at low cost. For this reason, it is used in a wide range of fields such as analog cordless telephones, wireless speakers, and game machines.
FIG. 4 is a schematic configuration diagram illustrating an example of a receiving apparatus compatible with the conventional FSK. As shown in FIG. 1A, the receiving apparatus 100 includes an antenna 1, a high frequency input circuit 2 including a SAW filter 2a and an impedance matching circuit (not shown), a high frequency amplifier circuit 3, a mixer 4a, and a frequency multiplier. 4b and a local oscillator 4c, a frequency converter 4, an IF bandpass filter 5a, an IF limiter amplifier 5b, an IF amplifier 5 comprising an RSSI circuit 5c, a detector 6a and a discriminator circuit 6b, and a filter (not shown) The detection output unit 6 includes a detection low-pass filter 6c including an amplifier and a CR circuit, and a comparator 6d.

In the figure, the received radio wave received by the antenna 1 has a predetermined frequency band selected by the SAW filter 2 a of the high frequency input circuit 2, level-amplified by the high frequency amplifier circuit 3, and one of the mixers 4 a of the frequency converter 4. Output to the input terminal.
The oscillation output of the local oscillator 4c multiplied to a predetermined frequency by the frequency multiplier 4b is input to the other input terminal of the mixer 4a.
A received wave (hereinafter referred to as an IF received wave) frequency-mixed with the frequency multiplier 4b output signal in the mixer 4a and converted to a predetermined intermediate frequency is output to the IF bandpass filter 5a of the IF amplifier 5.

The IF reception wave from which the unnecessary wave is removed by the IF bandpass filter 5 a is amplified to a predetermined level by the IF limiter amplifier 5 b and output to the detection output unit 6.
The IF reception wave input to the detection output unit 6 is detected by the detection unit 6a using the discriminator circuit 6b as a phase shift circuit.
The detection output of the detection unit 6a is removed from the high-frequency component by the detection low-pass filter circuit 6c and output to the comparator 6d. The comparator 6d forms the waveform, and the demodulated signal is taken out from the DATA-OUT terminal in the figure. Further, the detection output signal can be directly taken out from the AF-OUT end in the figure.
From the other output end of the IF limiter amplifier 5b, a DC voltage corresponding to the input level of the IF limiter amplifier 5b can be taken out from the RSSI-OUT end of the figure via the RSSI circuit 5c.

In order to reduce the size of the receiving apparatus 100 configured as described above, for example, the high-frequency amplifier circuit 3, the mixer 4a, the frequency multiplying unit 4b, the IF limiter amplifier 5b, the RSSI circuit 5c, the detecting unit 6a, and the detecting low-pass filter circuit 6c shown in FIG. A general-purpose ASK / FSK-compatible detection IC (hereinafter simply referred to as a detection IC) including a low-pass filter amplifier (not shown) and a comparator 6d included therein is provided on the market.

FIG. 4B is a schematic configuration diagram in the case where an ASK / FSK compatible receiving apparatus 100 having the same function as that in FIG. 4A is configured using the detection IC. As shown in the figure, the receiving device 100a includes an antenna 1, a high-frequency input circuit 2 including a SAW filter 2a, a local oscillator 4c, an IF bandpass filter 5a, a discriminator circuit 6b, and an active filter. The detection low-pass filter circuit 6c is constituted by a CR circuit 6c1 and a detection IC 7, and the other components are externally attached to predetermined connection terminals of the detection IC 7 to constitute a receiving device. .
JP 2002-033690 A

Weak radio or low-power radio stations can be configured to be small and light and do not require a license to use the frequency, but on the other hand, because the transmission power is regulated low by the Radio Law, it is convenient for the user by extending the communication distance In order to improve the performance, it is desired to improve the reception sensitivity characteristic.
As described above, in a receiving device composed of a general-purpose detection IC and external parts, there is a problem that reception characteristics are lowered due to deterioration of circuit characteristics due to variations in constants of parts used in each circuit. there were.
Further, in ASK / FSK reception, if the cutoff frequency of the low-pass filter is increased to improve the accuracy of the pulse width between the accuracy of the pulse width and the reception sensitivity in the detection low-pass filter constituted by the active filter, the reception is performed. The sensitivity decreases, and there is a trade-off relationship that the accuracy of the pulse width deteriorates when the cutoff frequency is lowered to improve the reception sensitivity. Therefore, in response to a request to make the pulse width of the demodulated data as close as possible to the pulse width of the transmission data, there is a problem that reception sensitivity is lowered when importance is attached to the pulse width accuracy.
The present invention has been made to solve the above problems, and an object of the present invention is to provide an ASK / FSK compatible receiver using a general-purpose detection IC and having excellent reception sensitivity characteristics.

In order to solve the above problem, in claim 1, an antenna, a high-frequency input circuit including a high-frequency bandpass filter, a high-frequency amplifier circuit, a frequency conversion unit including a local oscillation circuit, an intermediate frequency bandpass filter, an RSSI An ASK / FSK-compatible receiving device including an intermediate frequency amplification circuit including a circuit, a detection circuit including a discriminator, a detection low-pass filter, and a comparator,
An impedance matching circuit including a capacitor including a variable capacitance diode and an inductor is provided between the high-frequency bandpass filter and the high-frequency amplifier circuit, and a certain level of signal is applied to the high-frequency input circuit so that the output level of the RSSI circuit is A memory is provided that stores a control voltage to be applied to the variable capacitance diode at the maximum.

According to a second aspect of the present invention, there is provided the ASK / FSK compatible receiving device according to the first aspect, wherein the control voltage stored in the memory is supplied to the variable capacitance diode when the ASK / FSK compatible receiving device starts operation. It is characterized by being configured to apply.

According to a third aspect of the present invention, an intermediate frequency amplifier including an antenna, a high frequency input circuit including a high frequency band pass filter, a high frequency amplifier circuit, a frequency converting unit including a local oscillation circuit, an intermediate frequency band pass filter, and an RSSI circuit is provided. ASK / FSK-compatible receiving device including a circuit, a detection circuit including a discriminator, a detection low-pass filter, and a comparator,
The variable capacitance diode having a variable capacitance diode as an oscillation circuit capacitance component of the local oscillation circuit, and when the output level of the RSSI circuit is maximized by applying a constant level signal to the high frequency input circuit And a memory storing a control voltage to be applied.

4. The ASK / FSK-compatible receiving device according to claim 3, wherein the control voltage stored in the memory is applied to the variable capacitance diode when the operation of the ASK / FSK-compatible receiving device is started. It is characterized by having comprised.

In claim 5, an intermediate frequency amplifier including an antenna, a high frequency input circuit including a high frequency band pass filter, a high frequency amplifier circuit, a frequency converter including a local oscillation circuit, an intermediate frequency band pass filter, and an RSSI circuit. ASK / FSK-compatible receiving device including a circuit, a detection circuit including a discriminator, a detection low-pass filter including an active filter, and a comparator,
Each capacitor constituting the low-pass filter for detection is provided with another capacitor connected in parallel via a switch, and when the RSSI circuit output level exceeds a predetermined level, the switch is closed. It is characterized in that a driving voltage is applied to connect each of the other capacitors.

According to the first and second aspects of the present invention, a capacitor and an inductor including a varactor diode are provided between the high frequency bandpass filter of the high frequency input circuit of the ASK / FSK compatible receiver using the detection IC and the high frequency input circuit of the detection IC. And a control voltage to be applied to the varactor diode when the output level of the RSSI circuit of the intermediate frequency amplifier circuit is maximized by adding a signal of a constant level to the high frequency input circuit. With memory.
The control voltage stored in the memory is applied to the varactor diode of the impedance matching circuit when the operation of the receiving device is started.
As a result, the impedance mismatch between the input circuit of the high-frequency bandpass filter and the detection IC is corrected, and the reception sensitivity of the receiving apparatus is improved.

According to the third and fourth aspects of the present invention, the oscillation circuit capacitance component of the local oscillator of the ASK / FSK compatible receiver using the detection IC is constituted by a varactor diode, and a signal of a certain level is applied to the high frequency input circuit. In addition, a memory is provided that stores a control voltage to be applied to the varactor diode when the output level of the RSSI circuit of the intermediate frequency amplifier circuit is maximized.
The control voltage stored in the memory is applied to the varactor diode of the local oscillator at the start of the operation of the receiving device.
As a result, it is possible to correct a deviation between the best sensitivity point and the center frequency of the IF reception wave caused by variations in the component constants of the components of the local oscillator or other circuit components. As a result, the receiving sensitivity of the receiving device can be improved.

According to the fifth aspect of the present invention, the other capacitors connected in parallel to each of the capacitors constituting the low-pass filter for detection composed of the active filter of the ASK / FSK-compatible receiving device using the detection IC via the switch When the output level of the RSSI circuit exceeds a predetermined level, a drive voltage with the switch as a closed circuit is applied to connect each of the other capacitors to change the cutoff frequency of the filter. It was configured to make it.
As a result, when the reception electric field strength is strong, the cutoff frequency of the filter can be increased to improve the accuracy of the pulse width rather than the reception sensitivity.
Also, when the received electric field strength is weak, the filter can be changed so as to increase the reception sensitivity by lowering the cutoff frequency of the filter.
Therefore, according to the receiving apparatus of the present invention, it is effective in providing an ASK / FSK compatible receiving apparatus having excellent receiving sensitivity characteristics.

The present invention will be described based on the embodiments shown in the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of an ASK / FSK-compatible receiving apparatus by a weak radio or low power radio station according to the present invention.
As shown in the figure, the receiving apparatus 110 includes an antenna 1, a high-frequency input circuit 20 including a SAW filter 2a, a local oscillator 4c, a bandpass filter 5a, a discriminator circuit 6b, and a detector for detection (not shown). A low-pass filter circuit CR circuit 6c1, an ASK / FSK compatible detection IC (hereinafter simply referred to as a detection IC) 7, a level detection circuit 8, and a memory 9 are included.
The receiving apparatus 110 replaces the high-frequency input circuit 2 in the conventional receiving apparatus 100 shown in FIG. 4 with the high-frequency input circuit 20, and further detects the level between the RSSI-OUT terminal of the detection IC 7 and the high-frequency input circuit 20. The circuit configuration is such that the circuit 8 and the memory 9 are connected. Further, the detection IC 7 is the same detection IC as the detection IC 7 of FIG.
The demodulating operation of the receiving device 110 is the same as the receiving operation of the receiving device 100 of FIG. 4 except for the operations of the high-frequency input circuit 20, the level detecting circuit 8, and the memory 9. Omitted.

As shown in FIG. 1, the high-frequency input circuit 20 of the receiving apparatus 110 includes a SAW bandpass filter 2a, an impedance matching circuit between the antenna 1 and the SAW bandpass filter 2a including the capacitor C1 and the inductor L1, and a varactor. A SAW bandpass filter 2a composed of a diode (variable capacitance diode) VC1, an inductance L2, and a capacitor C2, and an impedance matching circuit between a high-frequency amplifier circuit (not shown) built in the detection IC 7 are included.
A control voltage is applied to the varactor diode VC1 from the memory 9 via a resistor R1.

The level detection circuit 8 is connected to an RSSI-OUT terminal of an intermediate frequency amplification unit (not shown) and detects the RSSI output level of the receiving apparatus.
Prior to use of the receiving device 110 having the above configuration, a control voltage applied to the varactor diode VC1 is monitored while the RSSI output level is monitored by the level detection circuit 8 in a state in which a high-frequency signal of a certain level is input from the antenna input circuit end. By changing the control voltage, the control voltage that maximizes the RSSI circuit output level is stored in the memory 9.
Simultaneously with the start of the operation of the receiving apparatus 110, the control voltage stored in the memory 9 is applied to the varactor diode VC1 through the resistor R1 to have a desired capacitance value.
Thereby, the impedance mismatch between the SAW filter 2a and the detection IC 7 input circuit is corrected, and the receiving sensitivity of the receiving apparatus 110 is improved.

FIG. 2 is a schematic configuration diagram showing a second embodiment of an ASK / FSK-compatible receiving apparatus by a weak radio or low power radio station according to the present invention.
As shown in the figure, the receiving apparatus 120 includes an antenna 1, a high-frequency input circuit 2 including a SAW filter 2a, a local oscillator 40, a bandpass filter 5a, a discriminator circuit 6b, and a detector for detection (not shown). The low-pass filter circuit includes a CR circuit 6c1, a detection IC 7, a level detection circuit 8a, and a memory 9a.
The receiving apparatus 120 replaces the local oscillator 4c in the conventional receiving apparatus 10 shown in FIG. 4 with the local oscillator 40, and further, between the RSSI-OUT terminal of the detection IC 7 and the local oscillator 40, the level detection circuit 8a. The circuit configuration is such that the memory 9a is connected. Further, the detection IC 7 is the same detection IC as the detection IC 7 of FIG.
The demodulating operation of the receiving device 120 is the same as the receiving operation of the receiving device 100 of FIG. 4 except for the operations of the local oscillator 40, the level detection circuit 8a, and the memory 9a. To do.

As shown in FIG. 2, the local oscillator 40 of the receiving apparatus 120 includes a piezoelectric vibrator X1, a varactor diode VC2, and an amplifier circuit 41. The varactor diode VC2 is connected to the varactor diode VC2 via a resistor R2. Connected to the memory 9a.
The local oscillator 40 continuously oscillates and outputs the vibration of the piezoelectric vibrator X1 in the amplifier circuit 41 using the capacity of the varactor diode VC2 controlled by the control voltage applied from the memory 9a as the capacity component of the oscillation circuit.

The level detection circuit 8a is connected to an RSSI-OUT terminal of an intermediate frequency amplification unit (not shown) built in the detection IC 7 to detect the RSSI output level of the receiving apparatus.
Prior to use of the receiving device 120 having the above-described configuration, the RSSI output level is monitored by the level detection circuit 8a while being applied to the varactor diode VC2 of the local oscillator 40 while a high-frequency signal of a constant level is input from the antenna input circuit end. And the control voltage that maximizes the RSSI circuit output level is stored in the memory 9a.
Simultaneously with the start of the operation of the receiving device 120, the control voltage stored in the memory 9a is applied to the varactor diode VC2 via the resistor R2, and the capacitance of the varactor diode VC2 becomes a desired capacitance value.

By configuring in this way, it is possible to correct a deviation between the best sensitivity point and the center frequency of the IF received wave caused by variations in the component constants of the components of the local oscillator 40 or other circuit components. As a result, the receiving sensitivity of the receiving device 120 can be improved.

FIG. 3 is a schematic configuration diagram showing a third embodiment of an ASK / FSK-compatible receiving apparatus by a weak radio or low power radio station according to the present invention.
As shown in FIG. 2A, the receiving apparatus 130 includes an antenna 1, a high-frequency input circuit 2 including a SAW filter 2a, a local oscillator 4c, a bandpass filter 5a, a discriminator circuit 6b, The detection low-pass filter circuit includes a CR circuit 6c10, a detection IC 7, a level detection circuit 8c, and a drive unit 10.
The receiving apparatus 130 replaces the RC circuit 6c1 of the low-pass filter circuit for detection in the conventional receiving apparatus 100 shown in FIG. 4 with the CR circuit 6c10, and further, between the RSSI-OUT terminal of the detecting IC 7 and the RC circuit 6c10. The level detection circuit 8c and the drive unit 10 are connected to each other. Further, the detection IC 7 is the same detection IC as the detection IC 7 of FIG.
The demodulating operation of the receiving apparatus 130 excludes the operations of the low-pass filter circuit for detection composed of the CR circuit 6c10 and the low-pass filter amplifier built in the detection IC 7, the level detection circuit 8c, and the drive unit 10. Since this is the same as the receiving operation of the receiving apparatus 100 of FIG. 4, the description of the operation of the common part is omitted.

FIG. 2B is a diagram showing a circuit configuration example of a detection low-pass filter circuit including the CR circuit 6c10 and a low-pass filter amplifier built in the detection IC 7.
As shown in the figure, the detection low-pass filter circuit of the receiving apparatus 130 includes a buffer amplifier 6C2 built in the detection IC 7, resistors R21, R22, R23, capacitors C21, C22, C23, and the capacitor C21. A capacitor C21a connected in parallel via a switch SW21, and an RC circuit 6c10 comprising capacitors C22a and C23a connected in parallel to the capacitors C22 and C23 via switches SW22 and SW23, respectively. This is a third-order Butterworth low-pass filter circuit configured.
The switches SW21 to SW23 are connected to the driving unit 10 and operate according to the driving voltage.

This receiving apparatus 130 is a receiving apparatus that is configured to meet the desire to make the pulse width of the demodulated data as close as possible to the pulse width of the transmission data while maintaining the necessary reception sensitivity.
In the above configuration, the level detection circuit 8b constantly monitors the RSSI output level. When the detection level in the level detection circuit 8b is equal to or lower than a predetermined level, the drive unit 10 does not operate, and each switch SW21, SW22 and SW23 are open circuits and form a basic circuit of a third-order Butterworth low-pass filter circuit.
When the received electric field strength is strong and the RSSI output detection level in the level detection circuit 8b is equal to or higher than a predetermined level, the drive voltage is output from the drive unit 10 to the switch SW21, SW22, SW23, and each switch is It becomes a closed circuit. For this reason, the capacitor C21 is connected in parallel to the capacitor C21a, the capacitor C22 is connected to the capacitor C22a, and the capacitor C23 is connected to the capacitor C21a.
As a result, the cutoff frequency of the detection low-pass filter circuit is increased, and the reception sensitivity of the reception device 130 is reduced, but the accuracy of the pulse width is improved.

With this configuration, it is possible to improve the accuracy of the pulse width of the demodulated data while maintaining a predetermined reception sensitivity.

BRIEF DESCRIPTION OF THE DRAWINGS The structure schematic diagram which shows the 1st form example of implementation of the receiving apparatus corresponding to ASK / FSK by the weak radio | wireless or low power radio station concerning this invention. The structure outline | summary figure which shows the 2nd example of implementation of the receiving apparatus corresponding to ASK / FSK by the weak radio | wireless or low electric power radio station concerning this invention. It is a figure which shows the 3rd example of implementation of the receiving apparatus corresponding to ASK / FSK by the weak radio | wireless or low power radio station concerning this invention, (a) is a structure schematic diagram, (b) is in (a). The circuit block diagram which shows the Example of the low-pass filter for a detection. It is a figure which shows an example of the receiving apparatus corresponding to ASK / FSK by the conventional weak radio | wireless or low power radio station, (a) is a structure schematic diagram, (b) is a general-purpose ASK / FSK with the circuit structure of (a). The structure schematic diagram comprised using corresponding detection IC.

Explanation of symbols

1. ・ Antenna, 2. ・ High frequency input circuit, 2a ・ ・ SAW filter, 3. ・ High frequency amplifier circuit,
4. Frequency converter, 4a Mixer, 4b Frequency multiplier, 4c Local oscillator,
5. IF amplifier, 5a IF band-pass filter, 5b IF limiter amplifier,
5c ··· RSSI circuit, ··· detection output unit, 6a ··· detection unit,
6b ... Discriminator circuit, 6c ... Low pass filter for detection,
6c1, 6c10 .. CR circuit of low-pass filter circuit for detection,
6c2 ・ ・ Low-pass filter amplifier, 6d ・ ・ Comparator,
7. ・ Detection IC for ASK / FSK, 8, 8a, 8b ・ ・ Level detection circuit,
9, 9a .. Memory, 10 ... Drive unit,
20 ... High frequency input circuit, 40 ... Local oscillator, 41 ... Amplifier circuit,
100, 100a, 110, 120, 130 .. ASK / FSK receiver,
C1, C2, C21, C21a, C22, C22a, C23, C23a .. capacitor
L1, L2, .. Inductor, R1, R2, R21, R22, R23 .. Resistance,
SW21, SW22, SW23... Switch, VC1, VC2 .. varactor diode,
X1 ・ ・ Piezoelectric vibrator

Claims (5)

An antenna, a high-frequency input circuit including a high-frequency bandpass filter, a high-frequency amplifier circuit, a frequency converter including a local oscillation circuit, an intermediate-frequency bandpass filter, an intermediate-frequency amplifier circuit including an RSSI circuit, and a discriminator ASK / FSK-compatible receiving device including a detection circuit including a low-pass filter for detection, and a comparator,
An impedance matching circuit including a capacitor including a variable capacitance diode and an inductor is provided between the high-frequency bandpass filter and the high-frequency amplifier circuit, and a certain level of signal is applied to the high-frequency input circuit so that the output level of the RSSI circuit is A receiver compatible with ASK / FSK, comprising a memory storing a control voltage to be applied to the variable capacitance diode at the maximum. 2. The ASK / FSK-compatible receiving device according to claim 1, wherein the control voltage stored in the memory is applied to the variable capacitance diode when the operation of the ASK / FSK-compatible receiving device is started. 3. . An antenna, a high-frequency input circuit including a high-frequency bandpass filter, a high-frequency amplifier circuit, a frequency converter including a local oscillation circuit, an intermediate-frequency bandpass filter, an intermediate-frequency amplifier circuit including an RSSI circuit, and a discriminator An FM / FSK-compatible receiving device including a detection circuit including a low-pass filter for detection, and a comparator,
The variable capacitance diode having a variable capacitance diode as an oscillation circuit capacitance component of the local oscillation circuit, and when the output level of the RSSI circuit is maximized by applying a constant level signal to the high frequency input circuit A receiver compatible with ASK / FSK, comprising a memory storing a control voltage to be applied to. 4. The ASK / FSK-compatible receiving device according to claim 3, wherein a control voltage stored in the memory is applied to the variable capacitance diode when the operation of the ASK / FSK-compatible receiving device is started. An antenna, a high-frequency input circuit including a high-frequency bandpass filter, a high-frequency amplifier circuit, a frequency converter including a local oscillation circuit, an intermediate-frequency bandpass filter, an intermediate-frequency amplifier circuit including an RSSI circuit, and a discriminator An ASK / FSK-compatible receiving device including a detection circuit including a detection low-pass filter including an active filter, and a comparator,
Each capacitor constituting the low-pass filter for detection is provided with another capacitor connected in parallel via a switch, and when the RSSI circuit output level exceeds a predetermined level, the switch is closed. An ASK / FSK-compatible receiving device, wherein a driving voltage is applied to connect each of the other capacitors.

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