JPS648928B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronically tuned receiver using voltage variable reactance elements in a high frequency tuning circuit and an oscillation tuning circuit, and an electronically tuned receiver that improves tracking errors in low and/or high frequencies. It's about machines.

Figure 1 shows a high-frequency tuning circuit, for example, an antenna tuning circuit 1 and an oscillation tuning circuit 2, each using a variable capacitance diode of equal capacitance, which is a voltage variable reactance element.
1 is a circuit diagram showing a conventional example of a medium-wave MW band electronically tuned receiver using D ₁ and D ₂ ; FIG. In FIG. 1, 3 is a high frequency amplifier circuit, 4 is a mixing circuit, 5 is a local oscillation circuit, 6 is an intermediate frequency amplifier circuit, 7 is a detection circuit, 8 is a low frequency amplifier circuit, and 9 is a speaker. E ₁ is a power supply, VR is a variable resistor for channel selection, R ₃ is a resistor connected in series between variable resistor VR and ground 10, R ₁ and R ₂ are movable terminals 11 of variable resistor VR,
These are resistors connected between the variable capacitance diodes D ₁ and D ₂ respectively.

In the circuit shown in FIG. 1, a bias voltage is applied to each of the variable capacitance diodes D ₁ and D ₂ by operating the variable resistor VR for channel selection, so as to receive the broadcast of a desired station. However, in a superheterodyne receiver like the one shown in FIG. 1, tracking errors generally occur.

FIG. 2 is a diagram showing the relationship between the tracking error and reception frequency of the medium-wave MW band receiver configured as shown in FIG. 1. As is clear from Figure 2, there are three points within the band where the tracking error is completely zero (i.e., in the receiver of Figure 1, the low tracking frequency (600KHz), the center tracking frequency (1000KHz), and a high tracking frequency (1400 KHz)], and tracking error frequencies of up to 5 to 10 KHz occur at other frequencies. The reception band of a medium wave band receiver is about 500 to 1600 KHz, and if the load Q of the antenna tuning circuit 1 is the same, the low frequency band width is about 1/3 narrower than the high frequency band width. Therefore, the deterioration of receiving sensitivity was particularly large in the low range, which was a practical problem. For example, in the circuit shown in FIG. 1, if the same bias voltage is applied to the variable capacitance diodes D ₁ and D ₂ of the antenna tuning circuit 1 and the oscillation tuning circuit 2,
LowEnd frequency (for the circuit in Figure 1,
522KHz), the tracking error was approximately 13dB. On the other hand, even in the high frequency range, the tracking error is approximately 4 to 5 dB at the HighEnd frequency (1611 KHz in the case of the circuit shown in Figure 1), so it was desired to improve the tracking error even in the high frequency range. .

In view of this, the present invention proposes an electronically tuned receiver that improves tracking errors in low and/or high frequencies. This will be explained according to Figure 3.

In FIG. 3, the same parts as in FIG. 1 are designated by the same numbers as in FIG. 1.

In the circuit of FIG. 3, a correction power source E ₂ and a diode D ₃ are connected between the ground 10 and one end of the resistor R ₁ .
A resistor _R4 is connected in series, and a buffer amplifier 12 is connected between the movable terminal 11 of the variable resistor VR and the other end of the resistor _R1 . The configuration is such that the correction voltage is applied only to the variable capacitance diode D1 of the antenna tuning circuit ₁ in a band below the low tracking frequency (600 KHz).

In other words, the voltage of the correction power supply E ₂ is VE ₂ , and each variable capacitance diode is
The bias voltage applied to D ₁ and D ₂ is e ₁ , the bias voltage applied to the variable capacitance diode D ₂ of the oscillation tuning circuit 2 is e _LO , and the low end frequency (522KHz) is e 1 .
When the tracking error becomes zero at the LowEnd frequency, the variable capacitance diode of antenna tuning circuit 1
Assuming that the voltage applied to D ₁ is e _LA , the forward voltage of diode D ₃ is V _D3 , and the resistance values of resistors R ₁ and R ₄ are r ₁ and r ₄ respectively, V _E2 = e ₁ = V _D3 ...... (1) e _LA = e _LO + (e ₁ − e _L0 )・r ₁ / r ₄ + r ₁ ...(2) Corrected power supply E ₂ and resistance
The values of R ₁ and R ₄ are set.

As is clear from equation (1), the voltage applied to each variable capacitance diode D ₁ and D ₂ is low in the low range below e ₁ [frequency range from Low End frequency (522 KHz) to low tracking frequency (600 KHz)]. D ₁ is forward biased. Therefore, in this low frequency region, a correction voltage is applied to the variable capacitance diode _D1 of the antenna tuning circuit 1.
That is, as can be seen from equation (2), if the bias voltage from the power supply E ₁ adjusted by the variable resistor VR [the bias voltage applied to the variable capacitance diode D ₂ of the oscillation tuning circuit 2] is e ₀ , then the correction Voltage of power supply E ₂ V _E2
Since the voltage difference between the voltage obtained by subtracting the forward voltage V _D3 of the diode D ₃ (V _E2 − V _D3 = e ₁ ) from the bias voltage e ₀ is divided by the resistors R ₁ and R ₄ , this The voltage [e _{0 +} (e ₁ − eo) ・r ₁ /r ₁ + r ₄ ] that is the sum of the divided voltage [(e ₁ − e 0 )・r ₁ / _{r 1 +} r ₄ ] to the bias voltage e ₀ is used for correction. It is applied as a voltage to the variable capacitance diode _D1 of the antenna tuning circuit 1.

With this configuration, tracking errors can be significantly improved at frequencies below the low tracking frequency.

Figure 4 shows the correction power supply in the circuit of Figure 3.
The tracking error characteristics below the low tracking frequency (600KHz) when E ₂ and resistors R ₁ and R ₄ are set to satisfy equations (1) and (2) above are:
This is a characteristic diagram comparing the tracking error characteristics of the conventional circuit shown in Fig. 1. The 〇 marks are the measured values when using the circuit of the present invention shown in Fig. 3, and the × marks are the measured values when using the conventional circuit shown in Fig. 1. The measured values are shown for each case.

As is clear from the characteristic diagram in Figure 4, when the circuit of the present invention is used, there is no tracking error at frequencies below the low-end tracking frequency (600KEz), and in particular, the conventional circuit does not track at low-end frequencies (522KHz). The error was approximately 13 dB, but in the circuit of the present invention, the tracking error at the Low End frequency has been improved to almost zero.

In the circuit shown in Figure 3, at frequencies above the low tracking frequency (600KHz), the voltage from the power supply _E1 adjusted by the variable resistor VR increases, which is clear from equation (1) above. Like, diode
_D3 is reverse biased and no correction voltage is applied to the variable capacitance diode _D1 of the antenna tuning circuit 1. Therefore, the voltage applied to the variable capacitance diode D ₁ of the antenna tuning circuit 1 is the same as the voltage applied to the variable capacitance diode D ₂ of the oscillation tuning circuit 2.

Furthermore, in the circuit shown in FIG. 3, the buffer amplifier 12 is configured so that the current from the correction voltage _E
It is provided to prevent it from flowing to the side.

Although FIG. 3 shows an embodiment of an electronic tuning receiver using a manual tuning method in which a channel is selected by operating a variable resistor VR, the present invention can also be applied to a receiver using a PLL synthesizer method. FIG. 5 is a circuit diagram showing the main parts of a medium wave band PLL synthesizer receiver using the present invention. In a PLL synthesizer type receiver, a circuit 1 including a low-pass filter and a DC amplifier that constitutes a PLL circuit is used.
6 can be used as a circuit corresponding to the buffer amplifier 12 of FIG. 3, so tracking errors in low frequencies can be improved by adding only a few components. In Fig. 5, 5' is a local oscillation circuit composed of a voltage controlled oscillator VCO,
D' ₂ is a variable capacitance diode constituting the oscillation tuning circuit 2' of the local oscillation circuit; 13 is a reference oscillator; 14
is a phase comparator, 15 is a programmable frequency divider, 1
7 is an operation section. For other parts that are the same as those in FIG. 3, the same figure numbers as in FIG. 3 are used.

In the circuits of FIGS. 3 and 5, an electronically tuned receiver with improved tracking error in the low frequency range has been described, but an electronically tuned receiver with improved tracking error in the high frequency range is also conceivable.

FIG. 6 is a circuit showing a medium wave band electronically tuned receiver that improves tracking errors in low frequencies and also improves tracking errors in high frequencies. In FIG. 6, the same parts as in FIG. 3 are designated by the same numbers as in FIG. 3. In the circuit shown in FIG. 6, a resistor _R5 , a diode _D4 , and a correction power source _E3 are connected in series between one end of the resistor _R1 and the ground 10. The other configurations are the same as in FIG. 3. In the case of the circuit shown in Figure 6, the correction voltage is applied to the variable capacitance diode _D1 of the antenna tuning circuit 1 in the band below the low tracking frequency (600KHz), as in the case of Figure 3. Range tracking frequency (1400KHz)
Even in the above bands, the configuration is such that a correction voltage is applied to the variable capacitance diode _D1 of the antenna tuning circuit 1.

That is, the voltage of the correction power supply E ₃ is V _E3 , the bias voltage applied to each variable capacitance diode D ₁ and D ₂ at the high tracking frequency (1400KHz) is e ₂ , High End
The bias voltage applied to the variable capacitance diode D ₂ of the oscillation tuning circuit 2 at the frequency (1611KHz) is e _HO ,
The voltage applied to the variable capacitance diode D ₁ of the antenna tuning circuit 1 when the tracking error becomes zero at the High End frequency is e _HA , the forward voltage of the diode D ₄ is V _D4 , and the resistance values of the resistors R ₁ and R ₅ are r ₁ and r ₅ respectively, V _E3 = e ₂ − V _D4 ………(3) e _HA = e _HO − (e _HO − e ₂ )・r ₁ / r ₅ + r ₁ …(4) Correct the power supply E ₃ and resistance to satisfy the relationship
The values of R ₁ and R ₅ are set.

As is clear from equation (3), the voltage applied to each variable capacitance diode D ₁ and D ₂ is high in the high range of e ₂ or more [frequency range from high tracking frequency (1400 KHz) to High End frequency (1611 KHz)]. Diode _D4 is forward biased. Therefore, in this high frequency region, a correction voltage is applied to the variable capacitance diode _D1 of the antenna tuning circuit 1. That is,
As can be seen from equation (4), if the bias voltage from the power supply _E1 adjusted by the variable resistor VR (the bias voltage applied to the variable capacitance diode D2 of the oscillation tuning circuit ₂ ) is eo, then this bias voltage eo and
_{The difference voltage ( eo _ _
-e 2} ) is divided by the resistors _{R 1 and} R _{5 ,} so _the voltage _[ e ₀ −(e ₀ −e ₂ )·r ₁ /r ₅ +r ₁ ] is applied to the variable capacitance diode D ₁ of the antenna tuning circuit 1 as a correction voltage. In this way, a correction voltage is applied to the variable capacitance diode _D1 of the antenna tuning circuit 1 in a high frequency region higher than the high tracking frequency, so that tracking errors in the higher frequency range higher than the high tracking frequency are improved.

On the other hand, at frequencies below the high-band tracking frequency (1400 KHz), the voltage from the power supply _E1 adjusted by the variable resistor VR becomes small, and the diode _D4 is reverse biased, as is clear from equation (3).
Therefore, in the frequency range below the high tracking frequency (1400KHz) and above the low tracking frequency (600KHz), no correction voltage is applied to the variable capacitance diode _D1 of the antenna tuning circuit 1.
The voltage applied to the variable capacitance diode D ₁ is the same as the voltage applied to the variable capacitance diode D ₂ of the oscillation tuning circuit 2.

In addition, in FIG. 6, if the voltage of the power source E ₁ is V _E1 , the magnitude of the voltage of each power source E ₁ , E ₂ , E ₃ is V _E1
Since the relationship is ＞V _E3 ＞V _E2 , the voltage obtained by dividing the power supply E ₁ with the dividing resistor can be used as the correction power supply, without having to provide a correction power supply separately from the power supply E ₁ . good. In this way, the power supply
Only E ₁ is required.

Furthermore, in the embodiments shown in FIGS. 3, 5, and 6, examples of so-called dual variable capacitance diodes in which variable capacitance diodes are used in the antenna tuning circuit and the oscillation tuning circuit are shown. However, the present invention can also be applied to an electronic tuning receiver using a so-called triple variable capacitance diode system in which variable capacitance diodes are used not only in the antenna tuning circuit and the oscillation tuning circuit but also in the tuning circuit of the high frequency amplifier circuit. I can do it. In this case, the same bias voltage as the variable capacitance diode of the antenna tuning circuit may be applied to the variable capacitance diode of the tuning circuit of the high frequency amplifier circuit over all frequencies. Furthermore, the present invention can be applied to reception bands other than medium wave bands. As described above, according to the present invention, the first correction circuit includes a first resistor, a first diode, and a first correction voltage source exhibiting a voltage corresponding to a low tracking frequency; and a second correction circuit consisting of a second correction voltage source exhibiting a voltage corresponding to the high-frequency tracking frequency, are connected to a bias voltage supply line to the voltage variable reactance element of the high frequency tuning circuit, and the bias voltage is equal to the first correction voltage. When the bias voltage is lower than the bias voltage source, the correction voltage from the first correction circuit is supplied to the voltage variable reactance element, and when the bias voltage is higher than the second correction voltage source, the correction voltage from the second correction circuit is supplied to the voltage variable reactance element. Since the tracking error is supplied in the low frequency range and/or the high frequency range, tracking errors can be significantly improved.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional electronic tuning receiver;
2 is a diagram showing the relationship between tracking error and reception frequency when the circuit shown in FIG. 1 is used, FIG. 3 is a circuit diagram showing an embodiment of the electronic tuning receiver according to the present invention, and FIG. 5 is a diagram showing tracking error characteristics, FIG. 5 is a main circuit diagram showing another embodiment of the invention, and FIG. 6 is a circuit diagram showing still another embodiment of the invention. 1...Antenna tuning circuit, 2, 2'...Oscillation tuning circuit, _D1 , _D2 , D' ₂ ...Variable capacitance diode, _E2 , _E3
…Correction power supply, D ₃ , D ₄ … Diode, R ₁ .R ₄ … Resistor.

Claims (1)

[Claims] 1. In an electronic tuning receiver that uses voltage variable reactance elements of equal capacity in the high frequency tuning circuit and the oscillation tuning circuit, the first bias voltage supply line to the voltage variable reactance element of the high frequency tuning circuit is
a first correction circuit comprising a resistor, a first diode and a first correction voltage source exhibiting a voltage corresponding to a low tracking frequency; and/or a second correction circuit comprising a second resistor, a second diode and a voltage corresponding to a high tracking frequency; When a second correction circuit consisting of a voltage source is connected and the bias voltage is lower than the first correction voltage source, the correction voltage from the first correction circuit is supplied to the voltage variable reactance element via the bias voltage supply line, and When the bias voltage is higher than the second correction voltage source, the correction voltage from the second correction circuit is supplied to the voltage variable reactance element via the bias voltage supply line, thereby reducing tracking errors in the low and/or high ranges. An electronic tuning receiver characterized in that it improves.