JPS624012B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides for freely controlling the tuning frequency and local oscillation frequency on the antenna side in a so-called electronically tuned superheterodyne receiving device in which the reception frequency is controlled by voltage or current. The present invention relates to a receiving device characterized by being able to perform the following functions.

An example of a conventional receiving device of this type is shown in FIG. In FIG. 1, 1 and 5 are varactor diodes for varying the antenna tuning frequency and local oscillation frequency, respectively, 2 is an antenna tuning circuit, 3 is a frequency mixer, 4 is a local oscillator, and 6 is an intermediate frequency amplifier (hereinafter referred to as IF). 7 is a detector.

In the above configuration, the signal radio wave entering the antenna tuning circuit 2 is mixed with the oscillation frequency of the local oscillator 4 by the frequency mixer 3 and converted into an intermediate frequency. The intermediate frequency signal is amplified by the IF amplifier 6, and the modulated signal is demodulated by the detector 7.

At this time, if the intermediate frequency is relatively low compared to the input signal frequency, the tuning frequency of the antenna 2 and the oscillation frequency of the local oscillator 4 are close to each other.
So-called tracking of both frequencies is possible.
That is, the common bias voltage generated by the bias control circuit 9 is supplied to the varactor diodes 1 and 5, and although both varactor diodes have the same capacitance change, for example, the padding capacitor 8 is connected to the oscillation side. By inserting the signal into the antenna side, it is possible to change the frequencies on the antenna side and the local side while maintaining a frequency difference corresponding to the intermediate frequency. This method uses current receiving equipment.
This is a very commonly used method.

However, as mentioned above, it is good if the intermediate frequency is relatively low compared to the signal frequency, but in a double super type receiver, especially when the first converter is an up converter, the first intermediate frequency may be lower than the signal frequency. Since the antenna tuning frequency and the local oscillation frequency are significantly different from each other, it becomes impossible to perform tracking using the method described above.

The present invention provides an electronically tuned receiving device that is also effective for such uses.

FIG. 2 shows an embodiment of the present invention.

In FIG. 2, parts with the same symbols as in FIG. 1 have the same functions. Further, the intermediate frequency is assumed to be sufficiently higher than the signal frequency. When the reception frequency is set by the reception frequency setting circuit 22, a local oscillation control code is calculated in the calculation circuit 18 in accordance with this, and based on this result, the digital signal generation circuit 16 generates a digital signal, for example. A pulse width modulated wave (hereinafter referred to as a PWM wave) is generated. This signal passes through a low-pass filter 14, where only the DC voltage is taken out and supplied to the varactor 5, which controls the local oscillation frequency.

On the other hand, the antenna tuning circuit needs to accurately track the local oscillation frequency, and in order to improve its tracking characteristics, the present invention divides the reception band into multiple parts (in this example, into three). There is. That is, in accordance with the frequency set by the receiving frequency setting circuit 22, the antenna tuning band is determined by the band determining circuit 21 which determines which band the frequency corresponds to, and the antenna is driven by the band switching control circuit 20. The tuning coil is switched to one of the tuning coils 11, 12, and 13 by a band switching switch 10.
At the same time, the arithmetic circuit 19 calculates an antenna tuning control code, the digital signal generating circuit 17 generates a digital signal, for example, a PWM wave, and the low-pass filter 15 generates a digital signal, for example, a PWM wave.
A bias voltage is supplied to the varactor diode 1 through . During this time, the relationship between the bias voltages of the varactor diodes 5 and 1 and the state of the band selection switch 10 are as shown in FIG.

Note that here, the digital signal generation circuit 16, 1
The reason for using a PWM wave as the output of 7 is that it has great practical value, such as the fact that only a low-pass filter is required for subsequent processing and only one output terminal is required.

In addition, as another example, if a CR oscillator is used as the local oscillator and an LC tuning circuit is used as the antenna tuning circuit, the relationship between the bias voltage and the frequency will have completely different characteristics. Even in such a case, according to the present invention, the arithmetic circuit 16,1
High-precision tracking can be easily achieved by simply changing the calculation conditions in step 7.

Note that in the above description, the digital signal generation circuit 16 and the low-pass filter 14 were used as means for controlling the oscillation frequency of the local oscillation circuit 4;
It may also be controlled by a phase-locked loop as shown in FIG. In FIG. 4, the output of the local oscillator 4 divided by the variable frequency divider 25 and the output of the reference frequency oscillator 26 are compared by the phase comparator 24, and this error output is passed through the low-pass filter 23 to the varactor diode 5. and controls the local oscillation frequency. The variable frequency divider 25 is connected to the arithmetic circuit 18.
In this case, the calculation circuit 18 calculates a division ratio code corresponding to the oscillation frequency.

As described above, the present invention is configured to independently supply control voltages to the local oscillation circuit and the antenna tuning circuit in accordance with the reception frequency, and in particular, the antenna tuning section subdivides the band to achieve tracking accuracy. Even in the case of an up-converter method where the intermediate frequency is sufficiently higher than the input signal frequency, optimal tuning control can be performed and a highly sensitive receiving device can be realized. It is possible to obtain excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional example, FIG. 2 is a circuit diagram of an embodiment of the present invention, FIGS. 3 a, b, and c are characteristic diagrams for explaining the operation of FIG. 2, and FIG. FIG. 3 is a circuit diagram of another embodiment of the present invention. 1...Varactor diode, 4...Local oscillation circuit, 5...Varactor diode, 11, 12, 1
3...Antenna tuning coil, 10...Band selection switch, 18, 19...Arithmetic circuit, 21...Band determination circuit, 22...Reception frequency setting circuit, 24
...Phase comparator, 25...Variable frequency divider, 26...
Reference oscillator.

Claims (1)

[Claims] 1. A superheterodyne receiving device in which the receiving frequency is controlled by voltage or current, including a plurality of input signal tuning circuits each receiving a plurality of divided receiving bands, and a plurality of input signal tuning circuits each receiving a plurality of divided receiving bands, and a switching circuit that switches between the plurality of input signal tuning circuits, an arithmetic circuit that independently calculates an input signal tuning control code and a local oscillation control code corresponding to the received frequency, and a drive circuit that is driven by the output of the arithmetic circuit. An electronically tuned receiver comprising: a digital signal generating circuit; and means for individually controlling an input signal tuning frequency and a local oscillation frequency using the output of the digital signal generating circuit. 2. In order to control the local oscillation frequency, a phase-locked loop consisting of a variable frequency divider, a reference frequency oscillator, a phase comparator, and a low-pass filter is used, and a calculation circuit calculates the division ratio of the variable frequency divider. An electronically tuned receiving device according to claim 1, characterized in that: 3. The electronically tuned receiving device according to claim 1, characterized in that a pulse width modulated wave generating circuit is used as the digital signal generating circuit.