JPH04301928A - Portable radio receiver - Google Patents

Abstract

PURPOSE:To improve service for users by eliminating a reception disable range caused by jamming waves having the large electric field strength of the portable radio receiver. CONSTITUTION:One part of an intermediate frequency output having desired waves within the communication service area of the hetelodyne type portable radio receiver is branched, amplified, detected and rectified, a low-pass filter 14 for passing the rectified output and blocking the reverse flow of received signals from an antenna is connected to an antenna output circuit, the equivalent resistance value of a diode 15 provided between the antenna output and a ground is lowered while increasing the intermediate frequency output of the desired waves and by lowering the impedance of the antenna, the reception input of the jamming wave with the high electric field strength is lowered.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable radio receiver.

0002

2. Description of the Related Art FIG. 3 is a block diagram of a conventional portable radio receiver. Superheterodyne receivers are common, and the received wave received by an antenna 1 is converted into an intermediate frequency signal by a local oscillation frequency output from a local oscillator 4 at a mixer 3 via a high frequency amplifier 2,
) 6, demodulated by a demodulator 7, and controlled by a controller 8 to output a speaker 9, a display 10, and a light emitting element (LED).
11 as necessary.

0003

[Problem to be Solved by the Invention] However, it is well known that in the actual field, the reception sensitivity of such a portable radio receiver for the desired signal deteriorates due to intermodulation distortion caused by the input of multiple interference waves at a large level. It is exactly as it is written.

FIG. 5 shows a transmitting antenna 31 that transmits a desired wave fD and a plurality of interference waves fUD (fUD1 to fUDn).
) is a diagram illustrating the positional relationship of the transmitting antennas 32 that transmit the signals, the field strength of the radio waves radiated from each antenna, and the unreceivable area, where (a) shows the positional relationship of the transmitting antennas 32 that transmit
The side view of (b) shows the relationship between the electric field strength EfD of radio waves radiated from each antenna and the distance of EfUD from the antenna, and ER represents the minimum electric field strength receivable by the mobile radio receiver. In addition, (c) is a plane map showing the electric field strength EPUD ~ EOUD and its range d1 ~ d2 at which the conventional mobile radio receiver is unable to receive the desired wave fD due to the above-mentioned intermodulation distortion etc. Although the mobile radio receiver can receive the desired wave fD within the receivable electric field range, the distance d around the transmitting antenna 32 is
This indicates that reception is not possible within a circular range 33 from 1 to d2.

[0004] FIG. 4 is a diagram showing the situation in which a portable radio receiver can receive data in terms of the relationship between the field strength of the desired wave fD and the field strength of the interfering wave fUD. Reception is possible in range A defined as a boundary, and in the explanation of FIG. 5, the range from EoUD to EmUD is in range B in FIG. 4, indicating that the receiver cannot receive. In this way, the desired wave electric field strength is ER
This is extremely inconvenient for the user, as the receiver cannot receive the signal even if it is located within a sufficiently large range where the receiver can receive the signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a portable radio receiver that can eliminate unreceivable areas that occur within communication service areas, which was a problem with the prior art, and can provide reliable service.

[0006]

[Means for Solving the Problems] As shown in FIG. 1, the portable radio receiver of the present invention amplifies a high frequency signal received by an antenna 1 with an amplifier 2, and mixes it with a signal supplied from a local oscillator 4. In a heterodyne receiver that selectively amplifies only the received wave of a desired frequency by passing the output through a bandpass filter 5, an amplifier 12 amplifies a part of the output signal of the bandpass filter 5, and the output is detected and rectified. a detection rectifier circuit 13 that converts the signal into a DC signal, and a detection rectifier circuit 1
a low-pass filter (LPF) 14 for passing the output of antenna 3 and simultaneously blocking high frequencies from antenna 1;
A diode 15 is provided for changing the value of the equivalent resistance depending on the magnitude of the output of the LPF 14, and the impedance of the antenna 1 is reduced by the output of the low-pass filter 14.

[0007]

Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 is the desired wave fD and multiple interference waves (fUD
1 to fUDn) is in a resonant state. 2 is an amplifier, and 3 is a mixer, which is mixed with the signal supplied from the local oscillator 4 and converted to an intermediate frequency, and only the desired wave fD component passes through the bandpass filter 5 and is sent to the intermediate frequency amplifier 6 and demodulation circuit 7. and is demodulated. 8 is a control unit, which includes a speaker 9, a display 10, and a light emitting element (LED) 1.
1 to give a predetermined output. When the multiple interference waves fUD received by the antenna 1 exceed a certain value, intermodulation occurs due to the nonlinearity of the amplifier 2 and mixer 3, resulting in intermodulation spurious. As a result, the reception sensitivity of the desired wave fD deteriorates. This is as explained in FIGS. 4 and 5 above. Therefore, in the present invention, a part of the output of the bandpass filter 5 is amplified by the amplifier 12, the output is converted into a DC voltage by the detection rectifier circuit 13, and the low-pass filter (LPF) 1
In addition to the output of antenna 1 through 4, the diode 15
Connect to circuit ground through. Only the component of the desired wave fD is output from the bandpass filter 5, and a part of it is converted into direct current by the amplifier 12 and the detection rectifier circuit 13, so the current flowing through the diode 15 is the desired wave fD.
The equivalent resistance value changes as shown in FIG. 2.

In FIG. 2, the changes in characteristics (a), (b), and (c) are determined by the amplification factor of the amplifier 12, and (a) shows when the amplification factor is high, and (b) shows when the amplification factor is high. indicates when is low. On the other hand, since the output of the antenna 1 is output with a certain resonant impedance, when the electric field strength of the desired wave fD becomes larger than a certain value, the equivalent resistance of the diode 15 decreases as described above, and the antenna impedance is lowered. Therefore, the input level to the amplifier 2 is equivalently lowered. Therefore, by adding the circuit of the present invention consisting of the amplifier 12, the detection rectifier circuit 13, the low-pass filter 14, and the diode 15, the receiver can detect the desired wave f.
Automatic gain control (AGC) is applied by D. As a result, even if the reception field strength of the interference wave fUD is strong, if the desired signal has a strong reception field strength equal to or higher than the AGC operation level, the input level of the interference wave fUD to the amplifier 2 is suppressed, and the sensitivity deterioration is reduced as shown in FIG. The reception limit value shown in is shown as a curve ◯, and the range B can be expanded as the receivable range A. The position of point (a) is the operating position of the AGC, which can be determined by setting the gain of the amplifier 12.

In the embodiment, a single superheterodyne type receiver has been described, but the same result can be obtained with a double superheterodyne type receiver. Incidentally, the same effect can be obtained by reversing the polarity of the diode 15 or by reversing the polarity of the commutator of the detection rectifier circuit 13. Further, in the example, the output of the low-pass filter 14 is connected to the diode 15, but the output of the low-pass filter 1
Even when the output of 4 is connected to the bias of the active element of amplifier 2, AGC is applied and the same effect can be obtained.

0010

By carrying out the present invention, it is possible to eliminate the unreceivable range due to interference waves, and the effect of improving services for users of portable radio receivers is significant.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention.

[Figure 2] Characteristic diagram of desired wave electric field strength versus diode equivalent resistance value

[Figure 3] Block diagram of a conventional receiver

[Figure 4] An explanatory diagram of the receivable range of the receiver for interference waves

[Figure 5] Explanatory diagram of desired wave and interference wave transmission locations, electric field strength, and unreceivable range

[Explanation of symbols]

1 Antenna 2 Amplifier 3 Mixer 4 Local oscillator 5 Bandpass filter 6 Intermediate frequency amplifier 7 Demodulator 8 Control section 9 Speaker 10 Display 11 LED 12 Amplifier 13 Detection rectifier circuit 14 Low pass filter 15 Diode 31, 32 Transmission antenna 33 Unreceivable range due to interference waves

Claims (1)

[Claims] Claim 1: A heterodyne mobile radio that selects a signal of a desired frequency from a received signal received by an antenna by mixing it with a predetermined local oscillation frequency, converting it to an intermediate frequency, passing it through a bandpass filter, and outputting the detected signal. In the receiver, an amplifier that amplifies a part of the output of the bandpass filter, a detection rectifier circuit that detects and rectifies the output of the amplifier, and a detection rectifier connected between the detection rectifier circuit and the antenna and from the detection rectifier circuit. a low-pass filter having a characteristic of passing the output of the antenna and blocking the output from the antenna; and a low-pass filter that is connected between the low-pass filter and ground and that outputs the output when the output level of the low-pass filter exceeds a predetermined value. and a diode whose equivalent resistance value decreases as the level increases, and is configured to reduce the impedance of the antenna by outputting the intermediate frequency of the desired wave, thereby suppressing the reception input of interference waves. A portable wireless command receiver.