JPH0884025A - Super-regenerative receiver - Google Patents

Abstract

PURPOSE: To provide a super-regenerative receiver which has a high selectivity and reduces the disturbance to another system. CONSTITUTION: The super-regenerative receiver is roughly provided with an antenna 1, a super-regenerative detection circuit 2, and an impedance matching circuit 5. The super-regenerative detection circuit 2 oscillates with a high frequency including a prescribed frequency and intermittently repeats the oscillating state of high frequency oscillation and the non-oscillation state by the quenching frequency between the prescribed frequency and the frequency of a low frequency signal. An SAWF 4 is provided between the antenna 1 and the super- regenerative detection circuit and allows only the high frequency component of the prescribed frequency to pass through. At least a part of the super- regenerative detection circuit 2 and the SAWF 4 is shielded by a shield 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a super reproduction receiver,
More specifically, the present invention relates to a super regenerative receiver that extracts a low frequency signal superimposed on a high frequency signal of a predetermined frequency received by an antenna. In recent years, such super playback receivers have been able to remotely lock automobile doors.
It is used in keyless entry modules for unlocking.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a configuration of a conventional super reproduction receiver. In FIG. 3, the super reproduction receiver is used for a keyless entry module that receives a radio wave of 314 MHz, for example, and includes an antenna 1, a super reproduction detection circuit 2, and an impedance matching circuit 3. The impedance matching circuit 3 includes a resistor R31 and a capacitor C31 inserted in series between the antenna 1 and the super regenerative detection circuit 2.
And the impedance between the antenna 1 and the super regenerative detection circuit 2 is matched.

The super regeneration detection circuit 2 has a power supply terminal 20 to which a predetermined voltage Vcc is applied from a DC power supply (not shown).
A transistor Q2, a load resistor R21, base bias resistors R22 and R23, a coil L21 and a capacitor C21 forming the high frequency oscillation circuit section 21.
And capacitors C22 and C23 for positive feedback, a coil L22 forming the quenching oscillation circuit section 22, and a resistor R2.
4 and capacitors C24, C25, C26, a capacitor C27 for bypassing a high frequency signal, and a low pass filter (referred to as LPF) 23 for extracting a low frequency signal superimposed on the high frequency signal, that is, a detection output. The capacitor C26 also operates as a positive feedback capacitor.

The high frequency oscillation circuit section 21 oscillates at a high frequency at a frequency including a predetermined frequency (314 MHz). The quenching oscillation circuit unit 22 sets the oscillating state and the non-oscillating state of the high frequency oscillation at a quenching frequency (for example, several tens to several hundreds kHz) between 314 MHz and the frequency of the low frequency signal (for example, audible frequency). Repeat intermittently. LPF23
Outputs a low frequency signal superimposed on a high frequency signal, that is, outputs a detection output.

Next, the operation of the super reproduction receiver of FIG. 3 will be described. When the radio wave of 314 MHz is received from the antenna 1, the high frequency signal of 314 MHz is input to the super reproduction detection circuit 2 via the impedance matching circuit 3. The high frequency oscillation circuit section 21 of the super reproduction detection circuit 2 oscillates at a high frequency in the vicinity of the frequency input from the antenna 1. The quenching oscillation circuit unit 22 intermittently repeats the oscillation state and the non-oscillation state of the high frequency oscillation circuit unit 21 in the high frequency oscillation state.
Here, the time to reach the saturation oscillation amplitude value when the high frequency signal is input to the quenching oscillation circuit unit 22 is shorter than the time to reach the saturation oscillation amplitude value when the high frequency signal is not input, and the quenching oscillation frequency is shorter. Therefore, the super-reproduction detection circuit 2 can extract the low-frequency signal superimposed on the high-frequency signal. As it is, since it contains the high frequency oscillation component and the quenching oscillation component,
The low frequency signal is taken out through the LPF 23.

[0006]

By the way, in recent years,
Due to an increase in demand for radio waves, a plurality of frequencies such as 314 MHz is assigned to a keyless entry module and 280 MHz is assigned to a pager in close proximity.

However, the internal capacitance of the transistor Q2 of the super reproduction detection circuit 2 changes abruptly during high frequency oscillation. Further, the Q of the high frequency oscillation circuit section 21 is low.
Further, the oscillation frequency of the high frequency oscillation circuit unit 21 changes depending on the temperature. Therefore, the super reproduction detection circuit 2 tunes in a wide range of frequency bands. As a result, the conventional super reproduction receiver has the first problem that the selectivity is poor.

Further, since the super reproduction detection circuit 2 operates as a high frequency oscillator, radio waves in a plurality of frequency bands are radiated from the antenna 1 and interfere with other systems using the radio waves. Moreover, since the oscillation spectrum is widened by tuning in a wide frequency band, there is a second problem that the frequency spectrum radiated from the antenna 1 is wide and interferes with many other systems.

Further, since the antenna 1 and the super-reproduction detection circuit 2 are connected by the impedance matching circuit 3, the radiation intensity of the radio wave from the antenna 1 is large and the third problem is that it interferes with a distant system. there were.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above technical problems and to provide a super regenerative receiver which has good selectivity and reduces interference with other systems.

[0011]

The invention according to claim 1 is
A super regenerative receiver that extracts a low frequency signal superimposed on a high frequency signal from a high frequency signal received by an antenna, oscillates at a frequency including a predetermined frequency, and It is provided between the super regenerative detection circuit and the super regenerative detection circuit that repeats the oscillating state and the non-oscillating state of the high frequency oscillation intermittently at a quenching frequency between the frequency of the frequency signal and the predetermined frequency. A narrow band filter that passes only the high frequency component of the frequency is provided.

According to a second aspect of the present invention, according to the first aspect, a high frequency amplifier circuit having a low reverse transfer coefficient is provided between the antenna and the narrow band filter.

The invention according to claim 3 is the invention according to claim 1 or 2.
The super-recovery detection circuit and the shielding means for electromagnetically shielding at least a part of the narrow band filter from the outside thereof.

[0014]

In the invention according to claim 1, an antenna,
A narrow band filter, which is provided between the super regenerative detection circuit and passes only a high frequency component of a predetermined frequency, is provided. Therefore, even if the frequency range of the high frequency signal received by the antenna is wide, only the high frequency component of the predetermined frequency is given to the super reproduction detection circuit by the narrow band filter. As a result, tuning to frequencies other than the predetermined frequency is eliminated, and the selectivity is improved. Further, even if the super regenerative detection circuit operates as a high frequency oscillator, the narrow band filter limits the frequency band of the radio wave radiated from the antenna to a predetermined frequency band. As a result, it is possible to prevent interference with other systems using radio waves.

According to the second aspect of the invention, a high frequency amplifier circuit having a low reverse transfer coefficient is provided between the antenna and the narrow band filter. For this reason, the sensitivity is increased and the radiation intensity of the radio wave radiated from the antenna is reduced. As a result, the selectivity is further improved and interference with other systems is reduced.

According to the third aspect of the present invention, the super-regeneration detection circuit and at least a part of the narrow band filter are electromagnetically shielded from the outside thereof. Therefore, the radiant intensity of the radio wave radiated from the super reproduction detection circuit becomes small. This results in less interference to other systems.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a super reproduction receiver according to an embodiment of the present invention. It should be noted that parts corresponding to those of the conventional super reproduction receiver of FIG. In FIG. 1, the super regenerative receiver is used for a keyless entry module that receives a radio wave of 314 MHz, for example, and includes an antenna 1, a super regenerative detection circuit 2, and an antenna 1.
And a super-recovery detection circuit 2 and a surface acoustic wave filter (hereinafter referred to as SAWF) as a narrow band filter that passes only a high frequency component of a predetermined frequency (314 MHz).
It is written. ) SAWF4 and impedance matching circuit 5
A super reproduction detection circuit 2 and a shield 6 electromagnetically shielding at least a part of the SAWF 4 from the outside. The impedance matching circuit 5 includes an antenna 1 and an S
The antenna 1 and the SAW include a π-type coil L51 inserted between the AWFs 4 and capacitors C51 and C52.
The impedance between F4 is matched.

The SAWF 4 has a narrow band characteristic of about 314 MHz with a center frequency of about 100 kHz above and below, and from the viewpoint of low loss and high sensitivity, the so-called double mode obtained by solving the degeneracy of the energy trapping type resonance mode. A mode resonance type or a unidirectional IDT (interdigital transducer) type is used. As the substrate (not shown) of the SAWF 4, an ST-cut crystal is preferable in view of the temperature characteristics of sound velocity, but a piezoelectric substrate made of lithium niobate, lithium tantalate, zinc oxide, gallium arsenide, or the like can be used. A normal transversal type can be used as the SAWF4, but in this case,
The loss is large, and the reception sensitivity and noise figure deteriorate.

The super regeneration detection circuit 2 has a power supply terminal 20 to which a predetermined voltage Vcc is applied from a DC power supply (not shown).
A transistor Q2, a load resistor R21, base bias resistors R22 and R23, a coil L21 and a capacitor C21 forming the high frequency oscillation circuit section 21.
And capacitors C22 and C23 for positive feedback, a coil L22 forming the quenching oscillation circuit section 22, and a resistor R2.
4 and capacitors C24, C25, C26, a capacitor C27 for bypassing a high frequency signal and a high frequency choke coil RFC1, and a low pass filter (L) for extracting a low frequency signal superimposed on the high frequency signal, that is, a detection output.
It is written as PF. ) 23, a capacitor C28 for preventing direct current from flowing to the SAWF 4, and a capacitor C29 for preventing direct current from flowing to the LPF 23. The capacitor C26 also operates as a positive feedback capacitor.

The high frequency oscillation circuit section 21 oscillates at a high frequency at a frequency including a predetermined frequency (314 MHz). The quenching oscillation circuit unit 22 sets the oscillating state and the non-oscillating state of the high frequency oscillation at a quenching frequency (for example, several tens to several hundreds kHz) between 314 MHz and the frequency of the low frequency signal (for example, audible frequency). Repeat intermittently. LPF23
Outputs a low frequency signal superimposed on a high frequency signal, that is, outputs a detection output.

Next, the operation of the super reproduction receiver of FIG. 1 will be described. When the radio wave of 314 MHz is received from the antenna 1, the high frequency signal of 314 MHz is input to the SAWF 4 via the impedance matching circuit 5. For this reason,
Even if the frequency range of the high frequency signal received by the antenna is wide, only the high frequency component of 314 MHz is applied to the super reproduction detection circuit 2 by the SAWF 4. As a result,
For example, tuning to frequencies other than a predetermined frequency such as 280 MHz is eliminated, and selectivity is improved.

The 314 MHz band high frequency signal that has passed through the SAWF 4 is input to the super reproduction detection circuit 2. The high frequency oscillation circuit section 21 of the super reproduction detection circuit 2 is synchronized with the high frequency signal input from the antenna 1 and oscillates at a high frequency as in the conventional case. The quenching oscillation circuit unit 22 intermittently repeats the oscillation state and the non-oscillation state of the high frequency oscillation circuit unit 21 in the high frequency oscillation state. Here, the time to reach the saturation oscillation amplitude value when the high frequency signal is input to the quenching oscillation circuit unit 22 is shorter than the time to reach the saturation oscillation amplitude value when the high frequency signal is not input, and the quenching oscillation frequency is shorter. Therefore, the super-reproduction detection circuit 2 can extract the low-frequency signal superimposed on the high-frequency signal. As it is, the high frequency oscillation component and the quenching oscillation component are included, so that the low frequency signal is taken out through the LPF 23.

Here, the super-reproduction detection circuit 2 is 314 MHz.
Even if it operates as a high frequency oscillator such as
Passing through the SAWF 4 is limited to a narrow spectrum within the pass band. Therefore, the frequency band of the radio wave radiated from the antenna 1 is limited to the 314 MHz band. As a result, it does not interfere with other surrounding systems. Further, at least a part of the super reproduction detection circuit 2 and the SAWF 4 is electromagnetically shielded from the outside by a shield 6. Therefore, the radiation intensity of the radio wave radiated from the super reproduction detection circuit 2 becomes small. This results in less interference to other systems.

FIG. 2 is a circuit diagram showing the configuration of a super reproduction receiver according to another embodiment of the present invention. The parts corresponding to those of the super reproduction receiver of FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. In this embodiment, it should be noted that the antenna 1 and the SAWF
4, a high-frequency amplifier circuit 7 having a low reverse transfer coefficient S12, an impedance matching circuit 8, and a capacitor C30 for bypassing a high-frequency signal are provided. The impedance matching circuit 8 includes a resistor R81 inserted in series between the antenna 1 and the high frequency amplifier circuit 7.
The coil L81 and the capacitor C81 are provided to match the impedance between the antenna 1 and the high frequency amplifier circuit 7.

The high frequency amplifier circuit 7 includes a transistor Q7.
A bias adjusting resistors R71, R72, R73 and a capacitor C71, a high frequency choke coil RFC2 for cutting high frequency components, and a capacitor C72 for preventing direct current from flowing to the SAWF4. In this high frequency amplifier circuit 7, the forward transfer coefficient S21 and the reverse transfer coefficient S12 are 10 to 20 dB and -10, respectively.
It can be about -20 dB. Therefore, in the case of reception, the high frequency signal is amplified and the sensitivity is increased, and in the case of oscillation, the isolation is increased and the radiation intensity of the radio wave radiated from the antenna 1 is reduced. As a result,
Furthermore, the selectivity is improved and the interference with other systems is reduced.

On the printed circuit board, the impedance matching circuits 5 and 8, the super reproduction detection circuit 2 and the high frequency amplification circuit 7 are provided.
It is also possible to realize the super-regenerative receiver shown in FIGS. 1 and 2 by mounting individual elements constituting the above, that is, a transistor, a resistor, a coil, a capacitor, and the like, and connecting them by solder. Some circuits can be formed over a semiconductor substrate such as silicon or gallium arsenide. In particular, gallium arsenide is capable of generating or propagating surface acoustic waves because it has a slight piezoelectric property, so that not only SAWF4 but also R, L, and C passive elements, as well as semiconductor amplifying elements-transistors. It is also possible to realize an integrated monolithic integrated circuit (IC) including the above. In this case, since the monolithic IC element can be easily enclosed in the metal container, the shield effect is improved, and the interference given to the outside is further reduced.

Further, in the high-frequency amplifier circuit 7 of FIG. 2, the emitter grounded circuit of the bipolar transistor is shown, but base grounding / collector grounding is also possible, and the gate grounding circuit of the FET (field effect transistor) is similar to the base grounding circuit. High isolation can be obtained. Of course, normal source grounding is also possible.

Further, although the SAWF4 is used as the narrow band filter, an AT cut crystal may be used to use a high frequency / narrow band crystal filter utilizing the thickness shear vibration mode of the fundamental wave or overtone.

Further, although the keyless entry module is implemented, it may be implemented for another super reproduction receiver such as a pager.

[0030]

According to the invention of claim 1, since the narrow band filter that passes only the high frequency component of the predetermined frequency is provided between the antenna and the super regenerative detection circuit, Even if the frequency range of the received high frequency signal is wide, only the high frequency component of the predetermined frequency is given to the super reproduction detection circuit by the narrow band filter. Therefore, tuning to frequencies other than the predetermined frequency is eliminated, and the selectivity is improved. Further, even if the super regenerative detection circuit operates as a high frequency oscillator, the narrow band filter limits the frequency band of the radio waves radiated from the antenna to a predetermined frequency band. Therefore, it does not interfere with other systems using radio waves.

According to the second aspect of the present invention, since the high frequency amplifier circuit having a low reverse transfer coefficient is provided between the antenna and the narrow band filter, the sensitivity is increased and the radiation from the antenna is achieved. Radiation intensity of radio waves is reduced. Therefore, the selectivity is further improved and the interference with other systems is reduced.

According to the third aspect of the present invention, the super-reproduction detection circuit and the shield means for electromagnetically shielding at least a part of the narrow band filter from the outside thereof are provided. The radiant intensity of the radio wave radiated from the circuit becomes small. This results in less interference to other systems.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a super reproduction receiver according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a super reproduction receiver according to another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a conventional super reproduction receiver.

[Explanation of symbols]

 1 ... Antenna 2 ... Super reproduction detection circuit 4 ... SAWF 6 ... Shield 7 ... High frequency amplification circuit

Claims (3)

[Claims] 1. A super-regenerative receiver for extracting a low-frequency signal superimposed on a high-frequency signal from a high-frequency signal of a predetermined frequency received by an antenna, the high-frequency oscillator oscillating at a frequency including the predetermined frequency, A super regenerative detection circuit that intermittently repeats an oscillating state and a non-oscillating state of the high frequency oscillation at a quenching frequency between the predetermined frequency and the frequency of the low frequency signal, the antenna, and the super regenerative detecting circuit. A super-regenerative receiver provided with a narrow band filter provided between the high frequency component and the high frequency component of the predetermined frequency. 2. The super regenerative receiver according to claim 1, further comprising a high frequency amplifier circuit having a low reverse transfer coefficient, which is provided between the antenna and the narrow band filter. 3. The super regenerative receiver according to claim 1, further comprising a shield means for electromagnetically shielding the super regenerative detection circuit and at least a part of the narrow band filter from the outside thereof.