JP2705794B2 - Receiving machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] When the passband of an IF signal obtained by converting a desired reception frequency to a predetermined intermediate frequency is changed, the first IF signal generated by shifting the frequency of the IF signal is filtered. The second IF signal generated by shifting the frequency of the filtered first IF signal is filtered, and further, the frequency of the filtered second IF signal is shifted to a predetermined intermediate frequency, so that the IF signal passes through. The band can be varied, and good reception according to the reception state can be obtained.

[Industrial applications]

The present invention relates to a super-heterodyne receiver for receiving an IF signal whose reception frequency has been converted to an intermediate frequency. In particular, a receiver that reproduces a stereo signal using both the upper sideband and the lower sideband of the intermediate frequency, for example, an in-vehicle FM receiver that exhibits a drastic change in radio wave conditions, has a remarkable effect.

In general, in a super-heterodyne receiver, by increasing the passband width of the intermediate frequency, the passbands of the upper sideband and the lower sideband of the intermediate frequency are widened, thereby enabling reception with excellent sound quality.

On the other hand, when the reception condition is deteriorated, for example, when the signal level of the desired reception frequency is lowered and the signal level emitted from the jamming station is high, the pass band width of the intermediate frequency is rather narrowed. This attenuates the interference frequency and noise components mixed with the frequency of the interfering station, and enables reception with a high S / N ratio.

Therefore, in order to always obtain good reception, it is necessary to change the passband of the intermediate frequency each time according to the reception state.

[Conventional technology]

In a conventional super-heterodyne receiver, the following is a method for changing the pass band width of the intermediate frequency. One is to provide a plurality of filters (for example, ceramic filters and the like) having different pass bandwidths and change the pass bandwidth of the intermediate frequency by a filter selected by a changeover switch or the like.

One is to use an intermediate frequency transformer that combines a tuning circuit composed of a coil and a capacitor (forming a so-called double tuning circuit), for example, by changing the capacitance of a capacitor in the intermediate frequency transformer. The tuning frequency is set (thus forming a bandpass filter) and the passband of the intermediate frequency is changed.

[Problems to be solved by the invention]

Various methods for changing the passband of the intermediate frequency have the following problems. When a plurality of filters are used, a problem arises in that the pass bandwidth of the intermediate frequency cannot be continuously varied, so that the pass bandwidth cannot be finely adjusted according to the reception state. Also, when an intermediate frequency transformer is used, in order to obtain a desired filter characteristic,
Intermediate frequency transformers must be combined in multiple stages,
Therefore, it is necessary to adjust the filter characteristics for each intermediate frequency transformer, which causes a problem that the adjustment is troublesome.

The present invention has been made in order to solve the above-mentioned problems, and simplifies adjustment of the intermediate frequency pass bandwidth.
It is another object of the present invention to provide a receiver capable of continuously varying its pass bandwidth.

[Means for solving the problem]

FIG. 1 is a diagram showing the principle configuration of a receiver based on the present invention. In FIG. 1, reference numeral 1 denotes a receiving unit, which receives a desired reception frequency as an IF signal converted into a predetermined intermediate frequency. 2 is a first 1IF shifter, the frequency of the IF signal, for example, shifted in the direction of the upper sideband Z _U of the IF signal first 1I
Generate an F signal. Reference numeral 3 denotes a first filter unit that has a fixed filter characteristic and filters the first IF signal. 4 is the 2nd IF
A shift unit, the first and the second 1IF signal wave Delo first filter unit 3, shifted in the direction of the lower sideband Z _D of example IF signal
Generate 2IF signal. Reference numeral 5 denotes a second filter unit which has a fixed filter characteristic and filters the second IF signal. Reference numeral 6 denotes a third shift unit, and the second IF filtered by the second filter unit 5
The frequency of the signal is shifted to the frequency of the IF signal. Reference numeral 7 denotes a reproducing unit that reproduces an audio signal S _A from the IF signal output from the third shift unit 6.

(Operation)

The present invention filters the first IF signal generated by shifting the IF signal output from the receiving unit 1, and further filters the second IF signal generated by shifting the filtered first IF signal. By shifting the second IF signal to the original IF signal, the intermediate signal pass bandwidth of the IF signal is changed.

That is, with the above configuration, the first IF shift unit 2
The frequency of the IF signal from the receiving unit 1, for example, shifted by a desired frequency in the direction of the upper sideband Z _U to generate a first 1IF signal, the first filter unit 3 for filtering the first 1IF signal. No. 2
IF shift section 4, a first 1IF signal filtered, for example, to generate a first 2IF signal shifted by a desired frequency in the direction of the lower sideband Z _D, the first filter unit 5, the first 2IF signal Filter. The third IF shift unit 6 converts the second IF signal into a signal having a predetermined intermediate frequency.
Shift to IF signal.

As a result, the pass band of the IF signal can be varied, and good reception according to the reception state can be performed.

〔Example〕

FIG. 2 shows an embodiment of the present invention. In the figure, the first IF shift unit 2 includes a first variable oscillator 20 and a first mixer 21. The first variable oscillator 20 continuously varies the oscillation frequency, and the first mixer 21 controls the variable oscillation frequency. By taking a difference from the intermediate frequency of the IF signal from the receiving unit 1, the intermediate frequency of the IF signal is shifted up to generate the first IF signal. The second IF shift unit 4 includes a second variable oscillator 40 and a second mixer 41. The second variable oscillator 40 continuously varies the oscillation frequency. The second mixer 41 includes the variable oscillation frequency and the first filter unit. The second IF signal is generated by shifting down the intermediate frequency of the IF signal by taking the difference from the frequency of the first IF signal from the third IF signal. The third IF shift unit 6 includes a third variable oscillator 60 and a third mixer 61, and a third variable oscillator
60 continuously varies the oscillation frequency, and the third mixer 61 calculates the difference between the varied oscillation frequency and the frequency of the second IF signal from the second filter unit 5 to obtain the intermediate frequency of the original IF signal. Shift up. The eleventh filter unit 3 includes a first filter 30, and the first filter 30 filters the first IF signal. The second filter unit 5 includes a second filter 50,
Filter 50 filters the second IF signal. Regarding other configurations, the same components as those shown in FIG. 1 are denoted by the same reference numerals or symbols.

This embodiment shifts the intermediate frequency up and down in the upper sideband direction and the lower sideband direction, respectively, by mixing each of the continuously variable oscillation frequencies and the intermediate frequency of the IF signal, respectively. Filtering is performed for each intermediate frequency that has been shifted up and down, respectively, and is returned to the intermediate frequency of the original IF signal, thereby continuously changing the pass band of the IF signal according to the variable oscillation frequency.

With the above configuration, it will be described in detail with reference to FIG. 3, for converting the receiving unit 1, the frequency of the radio waves received from the antenna ANT into an intermediate frequency f ₀ ((1 column)). (1)
The column is a spectrum of the intermediate frequency, occupying the upper sideband Z _U and the lower sideband Z _D around the carrier f _0. The first mixer 21 calculates a difference between the oscillation frequency f ₀ + f ₁ + Δf set by the first variable oscillator 20 and the intermediate frequency f ₀ , thereby obtaining Δf with respect to the center frequency f ₁ of the first filter 30. only an intermediate frequency f ₀ is shifted up in the direction of the upper sideband Z _U ((column 2)). The first filter 30 filters the shifted-up intermediate frequency f ₁ + Δf according to predetermined filter characteristics (points indicated by dotted lines in the column (2)) (column (3)). The second mixer 41 calculates the difference between the intermediate frequency f ₁ + Δf from the first filter 30 and the oscillation frequency f ₁ + f ₂ + 2Δf set by the second variable oscillation section 40, thereby obtaining the center frequency f 2 of the second filter 50. (column (4)) only Δf against ₂ intermediate frequency direction of the shift-down of the lower sideband Z _D. In the second filter 50, the shifted down intermediate frequency f ₂ −Δf is filtered by a predetermined filter characteristic (a portion indicated by a dotted line in the column (5)) (column (5)). Third
The difference between the intermediate frequency f ₂ -Δf from the second filter 50 of the mixer 61 and the oscillation frequency f ₀ + f ₂ -Δf from the third variable oscillator 60 is returned to the original intermediate frequency f ₀ ((6 ) Column). Thereby, the first variable oscillator 20 and the second variable oscillator 4
By continuously varying the oscillation frequency of 0 and the third variable oscillator 60 (that is, Δf is continuously varied), the pass band of the IF signal from the receiving unit 1 can be continuously varied. Thus, the IF signal that has passed through the pass band that can be continuously changed is reproduced by the reproducing unit 6 as the audio signal S _A.
Will be played.

FIG. 4 shows a specific example in this embodiment,
This is an example of application to an on-vehicle FM receiver, in which one variable oscillator 8 is shared, and Δf in the above-described embodiment is continuously changed, so that the intermediate frequency f ₀ of the IF signal can be controlled by one operation.
Indicating that continuously vary the passband width of the upper sideband Z _U and the lower sideband Z _D in. In the figure, the receiving unit 1 is made of the high-frequency amplifier circuit 10 and the variable oscillator 11, a radio frequency amplifier circuit 10 is tuned to the desired frequency f _r, the variable oscillator 11 to convert the frequency f _r to a predetermined intermediate frequency Generate frequencies to be mixed. 1st variable oscillator 2
0, a second variable oscillator 40 and the third variable oscillator 60 share the variable oscillator 8, the amount of frequency shift in the direction of the upper sideband of the intermediate frequency Z _U and the lower sideband Z _D in the variable oscillator 8 Stipulate. The first mixer 21 includes a frequency that is mixed by the mixer 22 and a variable frequency from a variable frequency and a variable oscillator 8 from the variable oscillator 11, the reception frequency f _r of the first intermediate frequency f _if1
Convert to The second mixer 41 includes mixers 42 and 44 and an oscillator 4
According to 3, the first intermediate frequency f _if1 from the first filter 30 is converted into the second intermediate frequency f _ir2 . The third mixer 61 is a mixer
63 and the oscillator 62 convert the second intermediate frequency f _ir2 from the second filter 50 to a first intermediate frequency f _if1 .

The reproducing unit 7 includes an IF detection circuit 70, an MPX demodulation circuit 71, and a power amplification circuit 72. The IF detection circuit 70 detects the signal of the first intermediate frequency f _if1 from the third mixer 61 into a low-frequency signal,
The detected low frequency signal is demodulated by the MPX demodulation circuit 71 into L channel and R channel stereo signals.
Stereo broadcast is reproduced from the speaker 100 via the power amplifier circuit 72. In addition, in order to eliminate the frequency f _if1 + 2f _ir2 + 2Δf of the sum of the second intermediate frequency f _ir2 + Δf and the oscillation frequency f _if1 + f _ir2 + Δf after the third mixer 61, the transmission filter of the first intermediate frequency f _if1 is deleted. _{May be} provided, and since this filter only _{needs to} actually remove the frequency of f _if1 + 2f _ir2 + 2Δf, there is almost no effect on the first intermediate frequency f _if1 .

The operation of the above configuration will be described below with reference to FIG. In the high frequency amplifier circuit 10 through the antenna ANT transmits the received frequency f _r which is tuned to the desired frequency f _r to the first mixer 21. In the mixer 22, the reception frequency f _r
Conjunction with the taking and the oscillation frequency f _r from the variable oscillator 11, the sum of the oscillation frequency f _if1 + Delta] f from the variable oscillator 8, and sends the oscillation frequency f _r + f _if1 + Δf to first mixer 21. In the variable oscillator 8, the oscillation frequency can be varied by changing Δf in the positive or negative direction. First
In the mixer 21, the reception frequency f _r and the oscillation frequency f _r + f _if1 + Δ
By taking the difference is f, converts the received frequency f _r to the first intermediate frequency f _if1 with ((1 column)), the first
The intermediate frequency f _if1 is shifted by Δf (column (2)).
In the first filter 30, the shifted first intermediate frequency f
_If1 + Δf is filtered by a predetermined filter characteristic (the center frequency is f _if1 and the portion indicated by the dotted line in the column indicated by the dotted line in (2)) is sent to the second mixer 41. At this time, the oscillation frequency f _if1 + f _if2 + 2Δf is input to the second mixer 41. The oscillation frequency f _if1 + f _if2 + _2Δf, due mixer 42 and an oscillation frequency 2f _if1 + 2.DELTA.f that Tei multiplying the oscillation frequency f _if1 + Delta] f from the variable oscillator 8, the natural oscillation frequency f _if1 -f _if2 from the oscillator 43 The difference is obtained by taking the difference with the mixer 44. In the second mixer 41, the filtered first
Intermediate frequency f _if1 + Δf and oscillation frequency f _if1 + f _if2 + 2Δf
_Is converted to the second intermediate frequency f _if2 by calculating the difference between the second intermediate frequency f _if2 and the second intermediate frequency f _if2 + Δf obtained by shifting the second intermediate frequency f _{if2 by} Δf to the second filter 50. In the second filter 50, the shifted second intermediate frequency f _if2 + Δf is filtered by the filter characteristic (column (3)) as the center frequency f _if2 and sent to the third mixer 61. At this time, in the third mixer 61, the sum of the oscillation frequency f _if1 + Δf from the variable oscillator 8 and the unique oscillation frequency f _if2 from the oscillator 62 is obtained by the mixer 63, and the oscillation frequency f _if1 obtained by + F _if2 + Δf is input. Third mixer
At 61, the difference is returned between the filtered second intermediate frequency f _if2 + Δf and the oscillation frequency f _if1 + f _if2 + Δf to return to the first intermediate frequency f _if1 . Thereby, the first intermediate frequency f
_if1 is detected by the IF detection circuit 70, demodulated as a stereo signal by the MPX demodulation circuit 71, power-amplified by the power amplification circuit 72, and output from the speaker 100 as stereo broadcast.

Thus, by continuously varying the oscillation frequency of the variable oscillator 8, the passband of the intermediate frequency can be continuously varied.

FIG. 6 is a diagram showing a configuration example of the variable oscillator 8. In the figure, variable oscillator 8 comprises an oscillation circuit 80 and a buffer circuit 83, an oscillation circuit 80, the capacitance of the varicap 82 by lowering the voltage by the variable resistor 81 to a DC voltage V _B of, for example, external supply Change the oscillation frequency by changing. The buffer circuit 83 stabilizes the oscillation frequency f _if1 + Δf in the oscillation circuit 80.

FIG. 7 is a diagram showing an improved example of this specific example. As shown in FIG. 6, but the voltage V _B by external supply in order to change the oscillation frequency of the variable oscillator 8 is controlled by a semi-fixed resistor 81, in this modified example, as the voltage V _B to be controlled, reception The oscillation frequency of the variable oscillator 8 is changed according to the signal level of the signal. That is, as shown in FIG. 8, since the antenna input level L ₁ (dBF) and the signal intensity S (V) are in a proportional relationship, the signal intensity normally detected in the IF detection circuit 70 is used by using this. By changing the oscillation frequency of the variable oscillator 8 according to the voltage (usually referred to as the S level voltage or the AGC voltage), the pass band of the intermediate frequency according to the signal level of the received signal can be automatically changed. Therefore, the operation of varying the passband of the intermediate frequency according to the reception state is simplified. In FIG. 7, the semi-fixed resistor VR is for correcting, for example, a variation in signal strength level. In the configuration of FIG. 7, the same components as those shown in FIG. 4 are denoted by the same reference numerals and symbols.

〔The invention's effect〕

As described above, according to the present invention, the passband of the intermediate frequency can be continuously varied according to the reception state, so that good reception according to the reception state becomes possible.
This is advantageous when the reception state changes during traveling of the vehicle, such as a vehicle-mounted receiver.

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle configuration of an in-vehicle receiver according to the present invention, FIG. 2 is a diagram showing one embodiment of the present invention, FIG. 3 is a diagram showing the operation of FIG. 2, and FIG. FIG. 5 shows a specific example of this embodiment, FIG. 5 shows the operation of FIG. 4, FIG. 6 shows a configuration example of the variable oscillator 8, and FIG. 7 shows an improved example of this specific example. Fig. 8 shows the antenna input level L _I (dBf) and signal strength S
It is a figure which shows the relationship with (V). 1 reception section, 2 first IF shift section, 3 first filter section, 4 second IF shift section, 5 second filter section, 6 third IF shift section, 7 reproduction Section, 20 first variable oscillator, 21 first mixer, 40 second variable oscillator, 41 second mixer, 60 third variable oscillator, 61 third mixer, 8. Variable oscillator.

Claims (2)

(57) [Claims] 1. A receiver for receiving a desired reception frequency as an IF signal converted to a predetermined intermediate frequency, detecting the IF signal, and reproducing the IF signal as an audio signal (S _A ), comprising: A first IF shift unit (2) that shifts the first IF signal to generate a first IF signal; a first filter unit (3) that has a fixed filter characteristic and filters the first IF signal; 3) a second IF shift unit (4) for shifting the frequency of the 1IF signal filtered to generate a second IF signal, and a second filter unit (4) having a fixed filter characteristic and filtering the second IF signal ( 5); and a third IF shift unit (6) for shifting the frequency of the second IF signal filtered by the second filter unit (5) to the frequency of the IF signal; and the first filter unit (3). In one side of the frequency of the first IF signal is cut off or attenuated, and the second Filter unit (5) in the other side of the frequency of the first 2IF signal is blocked or attenuated, wherein said 1IF shift unit (2) and the first 2IF shift unit (4)
In the receiver in which the pass band width of the IF signal is made variable by changing the shift amount of the frequency in the first IF shift unit (2), the second IF shift unit (4), and the third IF shift The variable shift amount in the section (6) is determined by one common variable oscillator (8),
A receiver, wherein the common variable oscillator (8) is controlled according to an output signal of the third IF shift unit (6). 2. An oscillation frequency of said common variable oscillator (8) is controlled in accordance with a signal strength detected by an IF detection circuit (70) for detecting an IF signal output from said third IF shift section (6). Item 2. The receiver according to Item 1.