JPH05175873A - Radio receiver - Google Patents

Abstract

PURPOSE:To obtain the radio receiver, which eliminates the influences of jamming waves and prolongs the service life of a battery, by comparing a received electric field intensity detecting signal level with a reference voltage and increasing/decreasing the current of a mixer corresponding to the received signal level. CONSTITUTION:This device is equipped with a reference voltage source 8, voltage comparator 9 to compare the received electric field intensity detecting signal level of an intermediate frequency amplifier 5 with the reference voltage of the reference voltage source 8, and control circuit 10 to control the current of a mixer 3 corresponding to the output of this voltage comparator 9. On the other hand, the mixer 3 is added a function to mix an RF signal received by an antenna 1 and the local oscillator(LO) signal of an LO 2 with a current corresponding to the control signal of the control circuit 10. The current of the mixer 3 is controlled according to the control signal corresponding to the output of the voltage comparator 9 to compare the received electric field intensity detecting signal level with the reference voltage and when the received signal level is larger, the current of the mixer 3 is decreased. Reversely when the received signal level is smaller, the current of the mixer 3 is increased, and energy consumption is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiver using mixing means for mixing a received signal with a local oscillator signal and converting it into an intermediate frequency signal.

[0002]

2. Description of the Related Art Conventionally, a radio receiving apparatus using a mixing means for mixing a received signal with a local oscillator signal and converting it into an intermediate frequency signal has been widely used.

A conventional radio receiver of this type is shown in FIG.
It will be described with reference to FIG. As shown in FIG. 4, a conventional radio receiving apparatus mixes an antenna 1 for receiving a signal, a local oscillator 2, a received signal and a signal output from the local oscillator 2 and converts them into an intermediate frequency signal. And a bandpass filter 4 for extracting only the intermediate frequency signal from the output of the mixer 3.
, Intermediate frequency amplifier 5, and demodulator 6 for demodulating the received signal
And a speaker 7 for converting the demodulated output into voice.

The operation of the radio receiving apparatus configured as above will be described. First, the received high frequency signal of frequency fR (hereinafter referred to as RF signal) is mixed with the local oscillator signal of frequency fL (hereinafter referred to as LO signal) in the mixer 3, and fR−
It is converted into signals of fL and fR + fL. These signals are input to the bandpass filter 4 having a center frequency of fO = fR-fL, only the intermediate frequency signal of fR-fL is output, and is input to the demodulator 6 through the amplifier 5. The demodulator 6 reproduces an audio signal from the intermediate frequency signal and outputs it from the speaker 7.

By the way, one of the important characteristics is an interfering wave characteristic such as intermodulation. The intermodulation is an unnecessary signal generated in the reception channel by the two interfering wave signals of the adjacent channel and the next adjacent channel, and is mainly generated by the distortion of the mixer.

Now, fR-Δf and fR-Δ2f are added to the mixer.
5 is input, the output of the mixer 3 is fIF-Δf and fIF-2Δf (fIF =
A signal of (fR-fL) is output, and third-order distortion components fIF-3Δf and fIF are further generated as intermodulation distortion.
Of these signals, the signals other than the signal fIF are removed by the bandpass filter 4, but the fIF signal is the intermediate frequency amplifier 5,
It is transmitted to the demodulator 6 and causes interference. Reducing the generation of this third-order distortion component is important in the mixer design. Usually, when the same element is used, the larger the current flowing in the mixer 3 is, the less the third-order distortion is generated, and the larger current is supplied to the mixer 3 so that a predetermined third-order distortion characteristic can be obtained. The machine is realized.

[0007]

However, in the above configuration, the portable receiver among the wireless receivers uses the battery as the power source, and therefore the above-mentioned configuration is achieved regardless of the strength of the high frequency reception signal level. As described above, when a large current is constantly supplied to the mixer 3, there is a problem that the talk time is shortened.

The present invention solves the above problems and provides a radio receiving apparatus which is not affected by interfering waves and has a long battery life.

[0009]

In order to solve the above problems, the present invention relates to a voltage comparing means for comparing the output of the received electric field strength detecting means with a reference voltage, and a control signal according to the output of the voltage comparing means. Is provided, and the current of the mixing means is controlled by the control signal output by the control means.

[0010]

With the above construction, the received electric field strength detection signal level is compared with the reference voltage, and the current of the mixer is reduced when the received signal level is high, and conversely, when the received signal level is low. By increasing the current, consumption of the battery can be prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a wireless reception device according to the present invention. In this figure, the present embodiment is different from the conventional example shown in FIG. 4 in that the reference voltage source 8, the received electric field intensity detection signal (hereinafter referred to as RSSI signal) level of the conventional intermediate frequency amplifier 5 and the reference voltage are the same. A voltage comparator 9 for comparing the reference voltage of the source 8 and a control circuit 10 for controlling the current of the mixer 3 by the output of the voltage comparator 9 are provided. With the current according to the control signal, the RF signal received by the antenna 1 and the LO of the local oscillator 2 are received.
The point is that the function of mixing with a signal is added. Others are the same as in the conventional example, and therefore, the same reference numerals are given to the same components and the description thereof is omitted.

The operation of this embodiment having the above-mentioned structure will be described below. As shown in FIG. 3, the relationship between the reception level of the RF signal and the output level of the mixer 3 is a straight line and R
As the F signal level increases, so does the mixer output level. Now, if the RF signal level is below VO, RSS
The I signal has a value lower than the reference voltage of the reference voltage source 8, the output of the voltage comparator 9 becomes L, and the control circuit 10 consequently outputs H as a control signal. With this signal,
The mixer 3 operates with a large current, and the third-order distortion level due to adjacent channel and next adjacent channel interference waves is low level L.
It becomes 1.

On the other hand, when the RF signal level is VO or higher,
The RSSI signal has a value higher than the reference voltage of the reference voltage source 8, the output of the voltage comparator 9 becomes H, and the control circuit 10 outputs L as a control signal as a result. With this signal, the mixer 3 operates with a small current, and the third-order distortion level due to the adjacent channel and the next adjacent channel interference wave becomes a high level L2, but the desired wave level is also large, so there is no problem in the reception operation and low consumption. Electricity can be achieved.

FIG. 2 is a circuit diagram of the mixer 3 used in the radio receiving apparatus of the present invention. The mixer 3 includes an RF terminal 11 and an LO terminal 12 connected to the antenna 1 and the local oscillator 2, respectively. The two band pass filters 13 and 14 that pass only the RF signal and the LO signal, and the bases of the band pass filters 13 and 14 connected to the band pass filters 13 and 14 via the capacitor 15,
The mixing transistor 16 for mixing the O signal, the transformer 18 having the primary side connected to the collector of the transistor 16 and the secondary side connected to the bandpass filter 4 via the IF terminal 17, and the mixing transistor 2 Bias resistors 19 and 20
A switching transistor 21 connected in parallel with the bias resistor 20, and a CONT terminal provided on the base of the switching transistor 21 and connected to the control circuit 10.
It is composed of 22 and.

The operation of the mixer 3 constructed as above will be described. First, when the CONT terminal 22 is H, the switching transistor 21 is turned on, the base current flows through the mixing transistor 16 through the resistor 19, and as a result, the current flowing through the collector of the mixing transistor 16 is relatively large. The third-order distortion due to is small.

On the other hand, when the CONT terminal 22 is L, the switching transistor 21 is in the OFF state, and the base current smaller than that in the former case flows through the resistors 19 and 20 in the mixing transistor 16, so that the collector current is also smaller than that in the former case. It is small, and as a result, the generation of third-order distortion due to the interfering wave is large. In this way, the operating current of the mixer 3 can be changed by the signal input from the control circuit 10 to the CONT terminal 22.

[0017]

As described above, according to the present invention,
By the control signal according to the output of the voltage comparator that compares the received electric field strength detection signal level and the reference voltage, the current of the mixer is controlled, and when the received signal level is high, the current of the mixer is reduced, and conversely, When the received signal level is low, the current of the mixer is increased to reduce the power consumption, and it is possible to obtain a radio receiving apparatus that has a long battery life and is not affected by an interference wave.

[Brief description of drawings]

FIG. 1 is a block diagram of a wireless reception device according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a mixer according to the present invention.

FIG. 3 is an input / output characteristic diagram of a mixer in the wireless reception device according to the present invention.

FIG. 4 is a block diagram of a conventional wireless receiver.

FIG. 5 is an output spectrum of a conventional mixer.

[Explanation of symbols]

1 ... Antenna, 2 ... Local oscillator, 3 ... Mixer, 4,
13, 14 ... Bandpass filter, 5 ... Intermediate frequency amplifier, 6 ... Demodulator, 7 ... Speaker, 8 ... Reference voltage source, 9 ... Voltage comparator, 10 ... Control circuit.

Claims (1)

[Claims] 1. A mixing means for mixing a received signal with a local oscillator signal to convert it into an intermediate frequency signal, a bandpass filtering means for bandpass filtering the output of the mixing means, and an amplification of the output of the bandpass filtering means. In a radio receiving device comprising an intermediate frequency amplifying means and a demodulating means for demodulating an output of the intermediate frequency amplifying means, a receiving electric field strength detecting means for generating a receiving electric field strength signal from an output of the bandpass filtering means, and a reference voltage. A voltage source, a voltage comparison means for comparing the output of the received electric field strength detection means with a reference voltage, and a control means for outputting a control signal in accordance with the output of the voltage comparison means, and the output of the control means is provided. A radio receiving apparatus, wherein a current of the mixing means is increased or decreased according to a received signal level by a control signal.