JPH057166A - Heterodyne system receiver - Google Patents

Abstract

PURPOSE:To improve the characteristic against a disturbing wave due to fluctuation in an ambient temperature of a heterodyne receiver. CONSTITUTION:This receiver is made up of a temperature detection section 6 detecting ambient temperature, a temperature correction section 7 selecting a frequency control signal determined in response to the detected detection signal, and a frequency control section 8 controlling the oscillation frequency of a local oscillator 3 by using the selected frequency control signal. The predetermined control signal is referred to as a frequency control signal determined in response to each temperature so that the effect is reduced due to the disturbing wave when a reception band characteristic is changed by the temperature characteristic of the local oscillator 3 and a BPF 4. Thus, even when the temperature characteristic of the local oscillator and the BPF differs in any way, the effect of a disturbing wave is reduced by varying a preset value to the temperature correction section in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver, and more particularly to a heterodyne radio receiver.

[0002]

2. Description of the Related Art In a conventional heterodyne type receiver, as shown in FIG. 8, a received high frequency signal input from an input terminal 1 is input to a frequency mixer 2 and an intermediate frequency signal is generated by a local oscillator signal generated by a local oscillator 3. Converted to a signal. The converted intermediate frequency signal is input to a demodulator 5 through a bandpass filter (hereinafter abbreviated as BPF) 4, and the demodulator 5 demodulates to obtain a demodulated signal.

However, since the oscillation frequency of the local oscillator 3 changes due to temperature fluctuations, the intermediate frequency signal also changes accordingly. As a result, there is a problem in that the reception band characteristic obtained by the BPF 4 is deviated, and the frequency is likely to be influenced by the interfering wave signal.

In order to solve this problem, as shown in FIG. 9, a function for controlling the oscillation frequency of the local oscillator 3 from the outside (Voltage Control Oscillation) is provided.
and a reference oscillator 31 that has a small change in oscillation frequency with respect to temperature fluctuations to form a phase-locked loop circuit (PLL circuit).
Had stabilized the oscillation frequency.

[0005]

In this conventional receiver, the reception band characteristic is improved by reducing the change in the oscillation frequency of the local oscillator, but in recent years, in order to improve the utilization efficiency of the frequency band, As the occupied bandwidth is being narrowed, the BPF is required to have a narrow bandwidth characteristic. As a result, even if the oscillation frequency of the local oscillator is constant, the reception bandwidth changes due to the change in the bandwidth of the BPF itself with respect to the temperature change, and there is a problem that the interference wave is again affected.

The present invention solves the above-mentioned problems of the prior art, and provides a receiver having a simple structure and reducing the influence of adjacent interfering waves.

[0007]

According to the present invention, a local oscillator that emits a local oscillation frequency, a received high frequency signal, a frequency mixer that emits an intermediate frequency signal from the local oscillation frequency, and a band to which the intermediate frequency signal is input are provided. In a receiver having a filter, a frequency control unit for controlling the oscillation frequency of the local oscillator, a temperature detection unit for detecting the temperature around the receiver, and a detection signal detected by the temperature detection unit,
A heterodyne type receiver including a temperature correction unit that selects a control signal predetermined by the temperature characteristics of the local oscillator and the bandpass filter and outputs the control signal to the frequency control unit is obtained. .

In the above, it is most effective that the temperature detecting section detects the ambient temperature of the local oscillator and the bandpass filter.

[0009]

The present invention will be described below with reference to the drawings.

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

The received high frequency signal input from the input terminal 1 is input to the frequency mixer 2 and converted into an intermediate frequency signal by the signal of the local oscillator 3. The converted intermediate frequency signal is input to the demodulator 5 through the BPF 4. The demodulator 5 demodulates and obtains a demodulated signal.

On the other hand, the detection signal detected by the temperature detection unit 6 which detects the ambient temperature of the local oscillator 3 and the BPF 4 is input to the temperature correction unit 7. In the temperature correction unit 7, the change in the oscillation frequency of the local oscillator 3 due to the temperature change and the BPF
A control signal preset according to each temperature is output to the frequency control unit 8 so as to improve the influence of the adjacent interfering wave caused by the change in the band characteristic of No. 4. The frequency control unit 8 controls the oscillation frequency of the local oscillator 3 according to the input control signal.

Next, the temperature characteristics and reception band characteristics of the above local oscillator 3 and BPF 4 will be described.

FIG. 2 is a diagram showing the frequency spectrum of the output signal of the frequency mixer 2. First, of the received high-frequency signals input from the input terminal 1, the desired received wave signal is f _D
And the disturbance signal is f _U. The oscillation signal of the local oscillator 3 is f _L0 . In the frequency mixer 2, the intermediate frequency signal _fIF is generated by the following relationships by these input signals. That is, the intermediate frequency signal f _IFD of the desired wave signal to be received is expressed in the form of subtracting f _L0 from f _D, and the intermediate frequency signal f _IFU of the interfering wave is expressed in the form of subtracting f _L0 from f _U. Therefore, if f _L0 is varied at a temperature, as f _IFD, f _{IF U} also fluctuates.

FIG. 3 is a frequency band characteristic diagram of the BPF 4. In the case of characteristic A, as shown in FIG. 4, out of f _IFD and f _IFU input to BPF 4, f _IFU is attenuated to f _IFD.
However, in the case of the characteristic B changed due to temperature fluctuation, f _IFD and f can be output as shown in FIG.
_{The IFUs} output together, causing a problem such as poor reception sensitivity under the influence of the interfering wave f _IFU .

Even when the band characteristic of the BPF 4 does not change, depending on the change of f _L0 , as shown in FIGS.
_IFU = is output. Here, FIG. 6 is an output frequency spectrum diagram of the frequency mixer 2 when f _L0 changes at a temperature different from that of FIG. 2, and FIG. 7 shows f _IFD = and f _IFU = of FIG. 6 as the BPF 4 of the characteristic A of FIG. It is a frequency spectrum figure output when it is inputted.

[0017] Therefore, in the present invention, as disturbance f _IFU relative change with respect to temperature variation of the band characteristic of f _L0 of the local oscillator 3 and BPF4 is minimized, select the control signal with a predetermined local oscillator 2 To output f _L0 .

[0018]

As described above, the present invention has the function of detecting the ambient temperature, the frequency control unit for controlling the oscillation frequency of the local oscillator so that the influence of the interfering wave is reduced, and the temperature correction unit. The influence of the interfering wave can be reduced, and the complicated structure such as the PLL circuit which is the conventional method is not necessary.

Furthermore, even if the local oscillator and the BPF have different temperature characteristics, the influence of the interfering wave can be reduced by arbitrarily setting a predetermined value in the temperature correction unit.

[Brief description of drawings]

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

2 is a diagram of an output frequency spectrum of the frequency mixer 2. FIG.

FIG. 3 is a diagram of band characteristics of BPF4.

FIG. 4 is a diagram of a frequency spectrum output in the case of the characteristic A of the BPF 4.

FIG. 5 is a diagram of a frequency spectrum output in the case of the characteristic B of BPF4.

FIG. 6 is a diagram of an output frequency spectrum of the frequency mixer 2 when f _L0 changes at a temperature different from that in FIG. 2.

FIG. 7 shows f _IFD and f _IFU of FIG. 6 as BPF of characteristic A of FIG.
4 is a diagram of a frequency spectrum that is output when input to 4; FIG.

FIG. 8 is a block diagram of an example of a conventional example.

9 is a block diagram of a conventional example in which some of the problems of the example of FIG. 8 are solved.

[Explanation of symbols]

1 Input Terminal 2 Frequency Mixer 3 Local Oscillator 4 BPF (Band Filter) 5 Demodulator 6 Temperature Detector 7 Temperature Corrector 8 Frequency Controller 9 PLL Circuit (Phase Lock Loop Circuit) 31 Reference Oscillator f _D Desired Received Wave Signal intermediate frequency signal of the intermediate frequency signal f _IFU f _U of the oscillation signal f _IFD f _D of f _U disturbance signal f _L0 local oscillator 3

Claims (2)

[Claims] 1. A receiver having a local oscillator that emits a local oscillation frequency, a received high frequency signal, a frequency mixer that emits an intermediate frequency signal from the local oscillation frequency, and a bandpass filter to which the intermediate frequency signal is input. A frequency control unit that controls the oscillation frequency of the oscillator, a temperature detection unit that detects the temperature around the receiver, and a temperature characteristic of the local oscillator and the bandpass filter according to the detection signal detected by the temperature detection unit. A heterodyne type receiver, comprising: a temperature correction unit that selects a control signal that is predetermined by and outputs the control signal to the frequency control unit. 2. The heterodyne receiver according to claim 1, wherein the temperature detector detects the ambient temperature of the local oscillator and the bandpass filter.