JPH0671196B2 - Receiver - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving device that can be used in V, U, SHF band television receivers, communication devices, and the like. In particular, the present invention relates to an electronic tuning type receiver using a varactor diode as a tuning element, and an object thereof is to detect a frequency characteristic within a reception band and correct it to an optimum frequency characteristic to enable stable reception.

Conventional technology In recent years, not only conventional video and audio,
Digital signals have come to be transmitted as represented by teletext broadcasting. With conventional receivers, the frequency characteristics within the reception band change depending on the desired reception frequency, and also due to the AGC operation of the high-frequency amplifier that suppresses fluctuations in the received electric field strength, causing deterioration of the demodulated image, voice, and data. In order to improve this, the varactor diodes constituting each tuning circuit are selected to suppress the tuning error and the characteristics are made uniform, but the fluctuation of the frequency characteristics for each reception frequency cannot be sufficiently suppressed. However, in the future broadcasting form,
Further improvement in performance is required.

Hereinafter, the above-described conventional receiving device will be described with reference to the drawings. FIG. 4 is a circuit block diagram of a conventional receiving device, in which a high frequency signal is supplied to a high frequency signal input terminal 13, a frequency is selected by the signal receiving unit 1, and after high frequency amplification,
After converting to the required intermediate frequency, it is output from the intermediate frequency signal output terminal 14.

The tuning voltage of the tuning circuit including the local oscillator of the signal receiving unit 1 is supplied from the tuning voltage generating unit 10 at the same voltage. Therefore, when the desired signal is received, each tuning circuit cannot always have the optimum characteristic for the desired signal, and the frequency characteristic within the reception band changes depending on the reception frequency, so that it is necessary to maintain this optimum characteristic. This technique typified by the single-super-heterodyne reception system is a basic technique for reception including a television broadcast signal, and the literatures and the like relating to this technique are not particularly appropriate.

Problems to be Solved by the Invention However, in the above configuration, since a common tuning voltage is supplied to the varactor diodes of each tuning stage,
We have attempted to equalize the frequency characteristics within the reception band by suppressing the error of the varactor diode, which is one of the tuning elements, during manufacturing, but it is possible to completely eliminate the error of the varactor diode at each tuning stage. However, the error causes the tuning error of the tuning circuit as it is, and considering the error of the coil and the capacitor that make up the tuning circuit, suppressing the tuning error complicates the tuning configuration and increases the cost. It was very difficult to integrate it.

The present invention has been made in view of the above problems, and detects a change due to gain control of a reception band frequency characteristic of a receiving device and a change for each desired signal frequency, and an optimum reception band frequency characteristic for receiving a desired signal. Therefore, it is an object of the present invention to provide a receiving device with improved performance and productivity without the need to severely suppress the error of the varactor diode, the coil, and the capacitor that are the tuning elements.

Means for Solving the Problems In order to solve the above problems, the receiving apparatus of the present invention supplies a signal for frequency sweeping in a desired receiving frequency band from a frequency sweeping signal generator to an input terminal of a signal receiving unit. Extracted from the intermediate frequency output terminal, converted to a DC voltage according to the output signal level with a detector, sampled and held to detect the DC voltage at any frequency, and compare the DC characteristics at each frequency point for frequency characteristics. Connect the calculation processing control unit to judge the error, correct the tuning voltage in the tuning voltage generation unit, and set the AGC voltage in the AGC voltage generation unit. It is provided with a configuration that suppresses the influence of changes in control and errors of the tuning element.

Operation The present invention can suppress the deterioration of the frequency characteristic within the reception band due to the influence of the error of the tuning element, the change at the time of gain control, and the change for each desired signal frequency by the above-mentioned configuration.

Embodiment Hereinafter, a receiver according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a receiving apparatus according to an embodiment of the present invention. Here, the operations of the signal receiving unit 1, the AGC voltage generating unit 11, and the tuning voltage generating unit 10 are the same as those in the conventional example, and thus detailed description thereof will be omitted.

In FIG. 1, when a desired signal is received, the desired signal is input from the input terminal 13, passes through the signal switch 2 and is supplied to the signal receiving unit 1. The signal receiving unit 1 converts the frequency to an intermediate frequency, takes out from the intermediate frequency signal output terminal 14, and supplies it to the circuit of the next stage. The circuit in the next stage generates an AGC voltage, supplies the voltage to the arithmetic processing control unit 12, and through the AGC voltage generation unit 11,
From here, the AGC voltage is supplied to the signal receiving unit 1. On the other hand, a part of the AGC voltage is supplied to the signal level controller 7 for adjusting the oscillation signal level of the frequency sweep signal generator 8 used for detecting the frequency characteristic in the reception band to the same level as the desired reception signal. We are supplying from 11. After setting the AGC voltage, the signal switch 2 is electrically connected between the signal level controller 7 and the input terminals of the signal receiving unit 1.

From the arithmetic processing control unit 12, the encoded control signal is given to the tuning voltage generating unit 10, the circuit to be supplied by the tuning voltage generating unit 10 is determined, and the DC voltage after A / D conversion is frequency swept signal generator. 8 and a signal having a frequency corresponding to the control signal from the arithmetic processing control unit 12 is generated. This frequency sweep signal is generated including the desired reception frequency band, and is repeatedly swept in the high and low directions within the sweep band. On the other hand, the oscillating frequency of the local oscillator of the signal receiving unit 1 oscillates in a relationship that produces an intermediate frequency, and the frequency sweep signal is input to the signal receiving unit 1 via the signal level controller 7 and the signal switcher 2. For example, a signal for frequency sweeping with the same sweep bandwidth is generated at the intermediate frequency output terminal. This means that the frequency sweep signal always appears in the intermediate frequency band even if the desired reception frequency is changed. Therefore,
The frequency sweep signal taken out from the intermediate frequency output terminal 14 is input to the frequency discriminator 9, and the DC voltage generated at the output is continuously sampled by the sample / hold device 5, and the A / D
After being converted into a digital signal by the converter 6, the static characteristic of the frequency discriminator 9 stored in advance, that is, a comparison with the frequency-voltage characteristic, is performed by the frequency sweep signal generator 8 to generate an arbitrary frequency. A control signal for the frequency sweep signal of the processing control unit 12 is determined. By the above operation, for example, in the case of receiving a television broadcast signal, the control signal corresponding to the center frequency, the video carrier frequency, and the audio carrier frequency within the desired reception band can be determined. After that, the signal switch 2 is switched so that the output end of the signal level controller 7 and the input end of the signal switch 3 become conductive. Again, the arithmetic processing control unit 12 supplies a frequency sweep reference signal to the tuning voltage generation unit 10,
A DC voltage corresponding thereto is generated from the tuning voltage generator 10 and a frequency sweep signal of a desired reception frequency pair enters the detector 4 through the signal level controller 7 and the signal switches 2 and 3 and is converted into a DC voltage. The sample / hold unit 5 holds the signal level at an arbitrary frequency point, the A / D converter 6 converts the signal level into a digital signal, and the digital signal is stored in the post-arithmetic processing control unit 12. The sweep frequency at this time may be the intermediate frequency band or the desired reception frequency. This signal represents the frequency characteristic of the frequency characteristic detection circuit. Next, the signal switch 2 is connected to the signal level controller 7
And so that the input end of the signal receiving unit 1 becomes conductive,
The frequency sweep signal is supplied to the signal receiving unit 1. Terminal 15 is connected to the output of the tuning circuit to be corrected, terminal 15 being coupled to the extent that its load does not affect the tuning circuit. The frequency sweep signal taken out from the terminal 15 flows to the detector 4 by the signal switching device 3 and the sample and hold device 5
Is supplied to. Here, whether the frequency is a preset frequency or not is determined by the arithmetic processing control unit 12 using the control signal given to the tuning voltage generation unit 10. When they match, a gate control pulse is generated in the sample and hold unit 5, and the detector 4 Holds the output voltage of the above, supplies a conversion start pulse from the arithmetic processing control unit 12 to the A / D converter, A / D converts the held DC voltage, and stores it inside the arithmetic processing control unit 12. Further, the arithmetic processing control unit 12 corrects the deviation due to the frequency characteristic of the stored frequency characteristic detection circuit to calculate the accurate in-band frequency characteristic of the signal receiving unit 1. For example, when receiving a television broadcast signal, if the center frequency, the video carrier frequency, and the audio carrier frequency are detected, the in-band frequency characteristics are ideal and the frequencies at the video carrier frequency and the audio carrier frequency are the same. It may be desirable for the characteristics to be at the same level. Therefore, in order to satisfy these relationships, the arithmetic processing control unit 12 supplies a control signal to the tuning voltage generating unit 10 to change each tuning voltage of the signal receiving unit 1 to change the frequency characteristic of the tuning circuit. As described above, the frequency characteristic is detected again to obtain a more optimal in-band frequency characteristic.

FIG. 2 is a signal waveform showing the operation of the main part of the receiving apparatus showing the embodiment of the present invention. The horizontal axis represents time. Reference numeral 16 represents a change in the time direction of the DC voltage supplied from the tuning voltage generator 10 to the frequency sweep signal generator 8. Also, this waveform is similar to the change in the output voltage of the frequency discriminator 9 in the time direction, which is operating to detect the tuning voltage at an arbitrary frequency. Reference numeral 17 indicates a gate control pulse for operating the sample / hold device 5. Reference numeral 18 is a voltage waveform obtained from the terminal 15 of the signal receiving section 1. Since the frequency sweep signal generator 8 generates the frequency sweep signal in which the frequency rises and falls, the frequency sweep signal appears alternately at every repetition at an arbitrary frequency point. That is, any time t ₁ on the time axis is t ₅ , t
₂ is t ₄ and t ₆ is t ₈ . As explained in Figure 1,
When the frequency discriminator 9 detects the DC voltage for sweep control at a specific frequency point, the time t ₁ , t ₂ , t ₄ , t ₅ , t ₆ , t of each point on the broken line 16 is detected.
₈ is that. Therefore, in order to hold the output signal taken out from the terminal 15 of the signal receiving unit 1 at this time, a gate control pulse such as the waveform 17 is supplied to the sample and hold unit 5 to sample and hold the signal 18 from the terminal 15. I do.

For example, when receiving a television broadcast signal, the time t ₁ , t
_In some cases, ₅ indicates the center frequency of the frequency characteristic in the reception band, times t ₂ and t ₄ indicate the video carrier frequency or the audio carrier frequency, and times t ₆ and t ₈ indicate the audio carrier frequency or the video carrier frequency.

FIG. 3 shows the frequency characteristic within the reception band of the receiving apparatus showing the embodiment of the present invention. The vertical axis represents the detection signal level, and the horizontal axis represents the frequency. The characteristic curve 19 is the case of the conventional example in which the tuning voltage is not corrected, and the characteristic curve 20 is according to the embodiment of the present invention. In the conventional example, each tuning circuit of the signal receiving unit 1 causes an error, so that the frequency characteristic within the reception band as a general characteristic has a deviation within the band. However, in the embodiment of the present invention, the frequency sweep signal level at an arbitrary frequency point can always be detected regardless of the operating state of the signal receiving unit 1, so that the frequency characteristic within the reception band is flat as shown by the characteristic curve 20. It is also possible to obtain, and it is also possible to obtain an arbitrary frequency characteristic depending on the calculation in the calculation processing control section 12.

EFFECTS OF THE INVENTION As is apparent from the above description, the present invention detects the frequency characteristic within the reception band according to the electric field strength at the time of reception, and individually adjusts the tuning voltage of each tuning circuit so that the frequency characteristic is suitable for signal reception. It is not necessary to severely suppress the error of each tuning element by controlling, supplying, and setting to, and it is possible to comprehensively suppress the error of the tuning circuit. Further, since it is possible to detect the in-band frequency characteristic at an arbitrary frequency point and obtain the required frequency characteristic, it is possible to more accurately correct the in-band frequency characteristic. Therefore, it is possible to provide a receiving device capable of improving performance and productivity while suppressing deterioration of the frequency characteristic in the receiving band due to the change at the time of gain control and the influence of the difference between the receiving frequencies, which are difficult with the conventional receiving device. it can.

[Brief description of drawings]

FIG. 1 is a block diagram of a receiving apparatus of the present invention, FIG. 2 is a signal waveform diagram during operation of a main part of the receiving apparatus in the embodiment of the present invention, and FIG. 3 is a band of the receiving apparatus in the embodiment of the present invention. FIG. 4 is a block diagram of a conventional receiving device. 1 ... Signal receiving unit, 2,3 ... Signal switching unit, 4 ... Detector, 5 ... Sample and hold device, 6 ... A / D converter,
7 ... Signal level controller, 8 ... Frequency sweep signal generator, 9 ... Frequency discriminator, 10 ... Tuning voltage generator, 11 ...
… AGC voltage generator, 12… Arithmetic processing controller.

Claims (1)

[Claims] 1. A frequency sweep signal generator for obtaining an intermediate frequency sweep signal by inputting a sweep signal to an input terminal for optimizing a frequency characteristic of a receiver for receiving a desired signal, and a frequency sweep signal for the intermediate frequency sweep signal. A frequency discriminator for detecting, a detector for detecting the voltage of the intermediate frequency sweep signal, a sample-and-hold device for holding a detection output signal of the detector, and an arithmetic control unit, and the frequency discriminator. The instrument sends a timing signal to the sample-and-hold instrument when the frequency reaches a predetermined frequency, and the arithmetic and control unit makes the sample and
A receiving device characterized by performing arithmetic processing for changing a tuning voltage according to an output signal of a hold device, and correcting the tuning voltage so that a frequency characteristic in a reception band is optimized.