JPH0450672Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a synthesizer receiver having a synthesizer tuner, and particularly to a synthesizer receiver that eliminates tracking errors.

[Prior Art] As is well known, a superheterodyne receiver converts a reception frequency to a predetermined intermediate frequency for detection.

As this kind of superheterodyne receiver,
An example of a synthesizer receiver using a synthesizer tuner is as shown in FIG.

A high frequency signal fed from an antenna is supplied to a high frequency amplifier 2, and a predetermined reception frequency is tuned and output, and this is supplied from a synthesizer oscillator 10 to a mixer 11, where it is converted into a predetermined intermediate frequency.

The intermediate frequency output is supplied to a detector 4 via an intermediate frequency amplification circuit 3, and the audio signal, which is the detected output, is supplied to a speaker 6 via an amplifier 5.

As is well known, the synthesizer oscillator 10 has a variable oscillator 12, whose oscillation output is supplied to a PLL 14, and a frequency control signal obtained by the PLL 14 is supplied to a frequency control section (resonant circuit) 13 of the variable oscillator 12. Ru.

Therefore, the PLL 1 is configured to oscillate at a predetermined frequency specified by the microcomputer 17.
4 is controlled, and the variable oscillator 12 is controlled. The oscillation output of the variable oscillator 12, that is, the local oscillation frequency, is supplied to the mixer 11 described above. This local oscillation frequency _fOSC is controlled so that local oscillation frequency fOSC=reception frequency _fRF ±intermediate frequency _fIF .

On the other hand, the frequency control signal supplied to the variable oscillator 12 is also supplied to the input tuning circuit 20 as its frequency control signal. Input tuning circuit circuit 2
0, the tuning frequency is controlled to become the receiving frequency.

Reference numerals 21 and 22 indicate variable capacitance elements (variable capacitance diodes), which have the same characteristics.

[Problems that the invention attempts to solve] By the way, in the superheterodyne receiver,
As described above, the local oscillation frequency supplied to the mixer 11 must always maintain the sum or difference between the reception frequency and the intermediate frequency. Ideally, tracking adjustment to adjust to such a frequency relationship is performed in all reception bands.

However, it is impossible to perform tracking adjustment in all frequency bands for the following reasons.

As described above, in the synthesizer oscillator 10, its frequency control section 13 and input tuning circuit 2
The variable capacitance elements 21 and 22 provided at 0 have the same capacitance and the same capacitance characteristics.

However, the frequencies to be controlled differ by the intermediate frequency between the input tuning circuit 20 and the frequency control section 13 of the variable oscillator 12, which are controlled by the same frequency control signal. Therefore, the input tuning circuit 20 and the frequency control section 13 of the variable oscillator 12 naturally have different oscillation constants.

Due to this, the frequency change characteristics for the frequency control signal in the input tuning circuit 20 and the frequency change characteristics for the frequency control signal in the frequency control section 13 of the variable oscillator 12 become different characteristics, and only at some frequencies. Both characteristics do not match.

As is well known, there are three matching points. Therefore,
In other frequency regions, the local oscillation frequency cannot be the sum or difference between the reception frequency and the intermediate frequency, and a tracking error will occur.

Note that the above-mentioned tracking error can be considered from another perspective as follows.

To take AM radio broadcasting as an example, the reception frequency band is 522-1611KHz, and the intermediate frequency is 450K.
Hz, the reception frequency expansion ratio is: Reception frequency expansion ratio = highest reception frequency / lowest reception frequency ≒3.09. However, the local oscillation frequency (variable oscillator 1
The expansion ratio of the oscillation frequency (2 oscillation frequency) is as follows: Local oscillation frequency expansion ratio = maximum local oscillation frequency/minimum local oscillation frequency ≒2.12.

If the expansion ratios differ in this way, tracking errors will occur at points other than the three adjustment points. this is,
The reception frequency at the input tuning circuit 20 and the mixer 11
This is because the receiving frequency at the 1st and 10th frequencies deviates from each other, and this deviation occurs based on the above-mentioned causes.

When a tracking error occurs, reception sensitivity deteriorates, and image interference ratio and IF interference ratio deteriorate.

Therefore, this invention solves these conventional problems and proposes a synthesizer receiver that eliminates tracking errors over the entire reception frequency band.

[Technical means for solving the problem] In order to solve the above-mentioned problem, this invention includes an input tuning circuit provided in a high frequency amplifier, a synthesizer tuner, and a synthesizer tuner provided in the synthesizer tuner. It has a variable oscillation section that oscillates the same frequency as the received frequency, a fixed oscillation section that oscillates an intermediate frequency, and a frequency mixer that mixes the received frequency and the intermediate frequency to obtain a local oscillation frequency. The oscillation section is incorporated in a PLL provided in the synthesizer tuner, and the frequency control signal from the PLL supplied to the variable oscillation section is also supplied as a frequency control signal to the input tuning circuit. It is something to do.

[Operation] In this configuration, the microcomputer 17 is configured to oscillate the reception frequency in the variable oscillation unit 40.
The PLL 14 is controlled by the frequency control signal from the PLL 14.

On the other hand, the oscillation frequency of the fixed oscillation section 50 is selected as an intermediate frequency, and this intermediate frequency and the reception frequency are supplied to a frequency mixer 60 and frequency-mixed.

Therefore, the frequency mixer 60 outputs a frequency that is the sum or difference of the intermediate frequency with respect to the received frequency, that is, a local oscillation frequency.

One of the local oscillation frequencies is extracted by the tuning circuit 70. In the embodiment, the sum (upper oscillation) frequency is output as the local oscillation frequency.

The frequency control signal output from the PLL 14 is also supplied to the input tuning circuit 20 as its frequency control signal.

By this frequency control signal, the input tuning circuit 20
will be tuned to the receiving frequency.

Here, since both the variable oscillator 40 and the input tuning circuit 20 are controlled to have the same resonance frequency, their respective expansion ratios are also the same.

The tuning frequency of the variable oscillator 40 and the input tuning circuit 20 is the same as the receiving frequency.

The output of the synthesizer oscillator 10 is transmitted to the variable oscillator 4
Since the frequency of the fixed oscillator 50, that is, the intermediate frequency, differs from the reception frequency of 0, the frequency of the input tuning circuit 20 and the synthesizer oscillator 10
The frequencies of will always have an intermediate frequency difference.

This relationship is maintained at any receiving frequency.

Therefore, no tracking error occurs in any frequency band.

[Example] Next, an example of a synthesizer receiver according to the invention will be described in detail with reference to FIG. 1.

Components corresponding to those in FIG. 3 will be described with the same reference numerals.

The synthesizer oscillator 10 includes a variable oscillation section 40, a fixed oscillation section 50, a frequency mixer 60, and a tuning circuit 7.
Consists of 0. Microcomputer 1
The output of 7 controls the PLL14, and from the PLL14,
The frequency control signal is supplied to the frequency variable section 42.

The variable oscillation section 40 includes an oscillation main body section 41 composed of an amplification means, a frequency variable section 42, and a PLL.
It consists of 14.

The frequency variable section 42 is configured as a tank circuit including a variable capacitance element 43, an inductance element 44, and a capacitor 45, and the frequency control signal described above is supplied as a control voltage of the variable capacitance element 43.

Since a part of the oscillation frequency (f _RF ') is supplied to the PLL 14 to form a closed loop, the frequency control signal applied to the frequency variable section 42 always allows the variable oscillation section 40 to output the received frequency. The same frequency is oscillated.

The synthesizer oscillator 10 is further provided with a fixed oscillation section 50.

The fixed oscillation section 50 is provided to obtain an intermediate frequency, and 51 is an oscillation main body section composed of amplifying means and the like, and in this example, a crystal resonator is used as the oscillation element 52. .

The intermediate frequency output from the fixed oscillator 50,
The received frequency output from the variable oscillator 40 is frequency-mixed in a frequency mixer 60. The frequency mixer 60 obtains the frequency of the sum or difference between the reception frequency and the intermediate frequency, and the tuning circuit 70 extracts either the sum or difference frequency of the reception frequency and the intermediate frequency.

In the example, the frequency of the sum is extracted. The frequency of this sum is used as the local oscillation frequency by the mixer 11.
It is supplied to

As shown, the tuning circuit 70 is configured as a tank circuit including a variable capacitance element 71 and an inductance element (using the primary side of a transformer) 72.

The reason why the variable capacitance element 71 is used in the tuning circuit 70 is that the tuning frequency needs to be changed in accordance with the reception frequency from the variable oscillation section 40.

Therefore, the output control signal that is the output of the PLL 14 is applied to the variable capacitance element 71 as the control signal.

The frequency control signal is further supplied to an input tuning circuit 20 and tuned to the reception frequency.

The input tuning circuit 20 also uses a tank circuit composed of a variable capacitance element 22, an inductance element 37, and a capacitor 38.

The variable capacitance element 4 provided in the frequency variable section 42, the tuning circuit 70, and the input tuning circuit 20 described above
Elements 3, 71 and 22 have the same values and characteristics. Further, the frequency variable section 42,
For the inductance elements 44, 72, and 37, and the capacitors 45 and 38 provided in the tuning circuit 70 and the input tuning circuit 20, elements having the same value and the same characteristics are used.

Note that in order to prevent spurious interference from occurring due to the oscillation forces from the variable oscillation section 40, fixed oscillation section 50, and tuning circuit 70, the respective oscillation outputs are made weak, or the variable oscillation section 40, fixed oscillation section 50 The entire synthesizer oscillator 10 constituted by the tuning circuit 70 and the tuning circuit 70 is shielded.

The PLL 14 provided in the variable oscillator 40 is connected to the microcomputer 1 that controls the receiver main body.
7.

A part of the output of the intermediate frequency amplifier circuit 3 is supplied to a signal detector 16, which detects the intermediate frequency signal during tuning.
7, where processing such as fixing a frequency sweep signal for channel selection is performed.

Further, during reception, a reception command signal is sent from the microcomputer 17 to the PLL 14 so that a local oscillation frequency is obtained in which the reception frequency is converted to an intermediate frequency and output.

Here, the same frequency control signal is commonly supplied to each of the variable oscillator 40, the input tuning circuit 20, and the tuning circuit 70, so that the input tuning circuit 20 is always tuned to the receiving frequency. Frequency control is performed, and the PLL 14 is used to obtain a local oscillation frequency for the synthesizer oscillator 10 so that it can always receive the reception frequency.
It is controlled by the output of

In this way, the tuning frequency of the input tuning circuit 20 is controlled to match the receiving frequency, and the receiving frequency and the local oscillation frequency are always controlled with a constant intermediate frequency difference by the same frequency control signal. That will happen. This relationship is maintained at any reception frequency.

Therefore, the receiving frequency obtained from the variable oscillator 40 and the tuning frequency of the input tuning circuit 20, that is, the receiving frequency (the receiving frequency input to the mixer 11)
are the same. As a result, the local oscillation frequency always maintains the sum or difference between the reception frequency and the intermediate frequency, so no tracking error occurs in any frequency band.

Let us consider the above-mentioned configuration of this invention using the above-mentioned expansion ratio as a reference.

Since both the variable oscillator 40 and the input tuning circuit 20 are controlled to oscillate the same receiving frequency, the variable capacitor 2
Elements 2, 43, and 71 each have the same capacitance and the same capacitance characteristics. Similarly,
Inductance element 37 configuring the tank circuit,
For both 44 and 72, elements having the same inductance value are used.

Therefore, the tuning frequencies of the respective resonant circuits become equal. Therefore, at least the expansion ratio of the tuning frequency in the frequency variable section 42 and the input tuning circuit 20 becomes equal. This relationship is satisfied for all frequency bands.

In other words, this means that tracking errors do not occur at all frequencies.

Incidentally, the variable oscillation section 40 provided within the synthesizer oscillator 10 would also originally have a PLL configuration.

That is, it should generally be configured as shown in FIG.

In the figure, a frequency control signal for instructing tuning is sent from a microcomputer 17 to an input tuning circuit 20 via an oscillation circuit 30.

The oscillation circuit 30 is configured to always oscillate the same frequency as the reception frequency, and has a PLL configuration.

Therefore, it has a variable oscillation section 31, and its oscillation output (its oscillation frequency f _RF ') is supplied to the PLL 32,
The output from the PLL 32 is applied to a tuning section 35 provided in the variable oscillator 31 as its frequency control signal.

In order to prevent spurious interference caused by the oscillation output, the oscillation output is made weak or the entire oscillation circuit 30 is shielded.

The frequency control signal supplied to the tuning section 35 is also supplied as a frequency control signal for tuning of the input tuning circuit 20.

Here, a control signal is supplied to the oscillation circuit 30 from the microcomputer 17 so that the oscillation circuit 30 always oscillates at the reception frequency. That is, a frequency control signal (tuning control signal) for receiving the specified broadcast station is sent to the synthesizer tuner 10.

On the other hand, a frequency control signal that is higher or lower than the intermediate frequency is sent to the PLL 32 of the oscillation circuit 30 so that the reception frequency of the designated broadcasting station is oscillated.

Therefore, the local oscillation frequency of the variable oscillator 12 and the oscillation frequency of the oscillation circuit 30 are controlled with a constant intermediate frequency difference.

The fact that the reception frequency and the oscillation frequency of the oscillation circuit 30 are equal means that the reception frequency and the local oscillation frequency are always controlled to have a constant intermediate frequency difference. This relationship is maintained at any reception frequency.

In this manner, according to the configuration shown in FIG. 2, a PLL is used for each of the synthesizer oscillator 10 and the oscillation circuit 30.

However, in the embodiment of this invention, the synthesizer oscillator 10 that obtains the local oscillation frequency has a
The PLL is configured so that it can also be used as a PLL of the variable oscillation section 40.

Therefore, with this configuration, it is possible to share the PLL system.

Note that when mounting, it is possible that the values of each element may differ slightly depending on the precision of the components. In that case, the inductance element is adjusted so that the sensitivity is maximized when receiving the highest and lowest frequencies in the reception band.

As a result, since the respective resonance constants match, it is possible to equalize the expansion ratio of the tuning frequency.

[Effects of the invention] As explained above, in this invention, a variable oscillation section that oscillates the same frequency as the reception frequency is provided, and the frequency control signal supplied to this section is used as the frequency control signal of the input tuning circuit 20. It is configured for common use.

According to this, the reception frequency obtained from the variable oscillation section 40 almost completely matches the reception frequency that is the tuning frequency of the input tuning circuit 20.

The fact that the respective reception frequencies are equal means that the expansion ratio can be kept constant, and the local oscillation frequency can be obtained by mixing the reception frequency and the fixed oscillation section, so the reception frequency and the local oscillation frequency always have a constant intermediate frequency difference. It will be controlled by

This relationship is maintained at any receiving frequency.

Therefore, no tracking error occurs in any frequency band.

Therefore, according to this invention, the deterioration of sensitivity caused by tracking error, the image disturbance ratio and
It has the feature of improving the deterioration of the IF interference ratio.

Therefore, the synthesizer receiver according to this invention is extremely suitable for application to a synthesizer receiver equipped with a synthesizer tuner controlled by a microcomputer as described above.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing an example of the essential parts of a synthesizer receiver according to this invention, Fig. 2 is a connection diagram of a synthesizer receiver used to explain this invention, and Fig. 3 is a connection diagram of a conventional synthesizer receiver. It is. 1...Synthesizer receiver, 10...Synthesizer oscillator, 14...PLL, 17...Microcomputer, 20...Input tuning circuit, 40...
Variable oscillation section, 42... Frequency variable section, 50... Fixed oscillation section, 60... Frequency mixer, 70... Tuning circuit.

Claims (1)

[Claims for Utility Model Registration] An input tuning circuit provided in a high-frequency amplifier, a synthesizer tuner, and a variable oscillator provided in the synthesizer tuner that oscillates at the same frequency as the receiving frequency;
It has a fixed oscillation section that oscillates an intermediate frequency, and a frequency mixer that mixes the reception frequency and the intermediate frequency to obtain a local oscillation frequency, and the variable oscillation section is installed in the PLL provided in the synthesizer tuner. A synthesizer receiver, wherein the frequency control signal from the PLL is incorporated and is supplied to the variable oscillation section, and is also supplied as a frequency control signal to an input tuning circuit.