JPS5915320A - Radio receiver - Google Patents

Abstract

PURPOSE:To always obtain the best receiving sensitivity, by using a digital means to control automatically the tracking of an RF tuning circuit. CONSTITUTION:A tuning volume 10 is coupled with a changing volume for local oscillating frequency (not shown in the diagram). Then the volume 10 is varied with interlocking to the selection of a certain broadcast signal. Thus the DC voltage value close to the approximate value of the broadcast signal frequency is supplied to a varactor within an RF amplifier 2 via a photodetecting element 21. Under such conditions, a flip-flop 14 is set. Then an oscillating circuit 16 and a clock pulse generating circuit 17 are actuated by a control circuit 15. An up-down counter 18 receives a clock pulse from the circuit 17 and then supplies the DC signals corresponding to the number of pulses to a light emitting element 20. As a result, the resistance value of the element 21 is reduced until a signal showing the best receiving point is obtained from a receiving peak detector 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an improvement in a radio receiver that performs electronic tuning using a semiconductor variable capacitance element.

(b) Background of the technology So-called electronically tuned radio receivers that use semiconductor variable capacitance elements as tuning elements and perform reception tuning by controlling the capacitance of the semiconductor variable capacitance elements by increasing or decreasing the applied voltage have already been put into practical use. There is.

The electronic iso-circular radio receiver is mechanically stronger and has better electrical characteristics than the conventional mechanical radio receiver using a variable capacitor, and the front end can be made more compact, and it is also capable of manual tuning and auto-tuning. , it has the advantage of being of equal length (equal length), which allows each preset tuning function to be easily provided, and makes tuning operations convenient. A drawback is that tracking errors occur due to changes in capacitance change characteristics due to the magnitude of the oscillation voltage.This tracking error is particularly noticeable when the reception band ratio is large, such as in an AM receiver. Uniform performance is often not achieved over the entire area.Currently, countermeasures to this problem include selecting semiconductor variable capacitors and improving circuit technology to some extent, but not completely.Therefore, tracking adjustment is required during the production process. However, 1. Tracking adjustment is troublesome and errors occur.

(c) Means for solving the problem The present invention eliminates the above-mentioned drawbacks, and provides a radio receiver that has no tracking errors without selecting semiconductor variable capacitance elements or performing tracking adjustment. be.

(2) Embodiment The present invention will be described below with reference to the drawings. (1) is an antenna, (2) is a high frequency amplification circuit connected to the antenna (1), and a high frequency amplification circuit that transmits the broadcast signal received by the antenna (1). It has a tuning circuit consisting of a semiconductor variable capacitance element and a coil for frequency tuning. (3) mixes the high frequency signal from the high frequency amplifier circuit (2) and the local oscillation signal from the local oscillation circuit (4) whose oscillation frequency is controlled by a semiconductor variable capacitance element to generate an intermediate frequency signal. A mixing circuit, (5) is an intermediate frequency amplification circuit that amplifies the intermediate frequency signal from the mixing circuit (3), (6) is a detection circuit, and the detected audio signal is added to the audio amplification circuit (7) and amplified. After that, the speaker (8) is driven. (A) is a tuning volume for obtaining a tuning voltage supplied to each of the semiconductor variable capacitance elements from the tuning power supply αη, and a part of the tuning voltage is directly applied to the local oscillation circuit (4). 02 is a DC voltage control circuit for correcting and applying the tuning voltage supplied from the tuning volume (G) to the semiconductor variable capacitance element of the high frequency amplifier circuit (2), and a detection signal from the peak value detection circuit (To). Controlled by The DC voltage control circuit 0
As shown in Figure 2, O is the RS clip-flop θ rotation R
S flip-flop becomes inoperable at chrysanthemum ~ control circuit Q! 9. an oscillation circuit a controlled by the control circuit αe; and a clock pulse generation circuit a″ for converting an oscillation signal from the oscillation circuit αO into a clock pulse signal.
i) an amplifier down counter that counts the clock pulse signal and generates a 5-bit output pulse; an output circuit 09 that converts the 5-bit output pulse into an analog signal; and an output circuit 09 connected to the output circuit 0. Light emitting diode (
e), and a light receiving element 01) optically coupled to the light emitting diode (1).

Next, the operation of the radio receiver of the present invention will be explained.

First, to select a channel, operate the tuning volume (A). Then, the tuning voltage obtained from the tuning power supply 0I) is increased or decreased. A part of the tuning voltage is directly supplied to the semiconductor variable capacitance element of the local oscillation circuit (4) to change the capacitance of the semiconductor variable capacitance element. The tuning voltage is also applied to the semiconductor variable capacitance element of the high frequency amplifier circuit (2) via the DC voltage control circuit (2) to change the tuning frequency of the tuning circuit of the high frequency amplifier circuit (2). When the tuning frequency of the tuning circuit is changed, it is tuned to the frequency of one broadcast signal received by the -r antenna (1). Therefore, the broadcast signal is applied to the high frequency amplifier circuit (2) and amplified, and then the mixing circuit (3)
) and mixed with the local oscillation signal of the local oscillation circuit (4). At this time, if you operate the tuning volume (G) as described above and set the oscillation frequency of the local oscillation signal so that the difference between the frequency of the broadcast signal being received is exactly the intermediate frequency, the mixing circuit (3) A more intermediate frequency signal can be obtained. By the way, when tuning is performed by operating the tuning volume (A) to change the capacitance of the semiconductor variable capacitance element, the difference between the oscillation frequency of the local oscillation signal and the frequency of the broadcast signal is just in the middle due to variations in the semiconductor variable capacitance element. Even if the local oscillation circuit (4) is controlled so as to match the frequency, the tuned frequency of the tuned circuit of the high frequency amplifier circuit (2) may not necessarily match the frequency of the broadcast signal being received. Therefore, the present invention operates the tuning volume (0) so that the oscillation frequency of the local oscillation circuit (4) is tuned to the difference between the frequency of the broadcast signal and the intermediate frequency. )
When the frequency of the tuning circuit is not tuned to the frequency of the broadcast signal being received, the DC voltage control circuit (6) corrects the tuning voltage applied to the semiconductor variable capacitance element of the high frequency amplifier circuit (2). Make the tuning frequency of the tuning circuit equal to the receiving frequency. That is, when tuning is started, the RS flip-flop Q→ is set and the cositroll circuit θQ is operated. Then, the oscillation circuit (
b) oscillates and generates a signal. The signal is converted into a clock signal by the clock signal generating circuit of>, passes through the control circuit ←→, is applied to the up/down counter (to), and is counted by the up/down counter (c). The count output of the up/down counter (to) is converted into an analog signal of a magnitude corresponding to the count number by the output circuit θ, and is applied to the light emitting diode (Inc.).

Therefore, as the up/down counter counts up, the luminance of the light emitting diode gradually increases, and the resistance value of the light receiving element Qυ decreases. High frequency amplifier circuit (2)
Since a voltage smaller than the optimum value is applied in advance to the semiconductor variable capacitance element by the resistor (A) board, the tuning voltage from the tuning volume (G) decreases as the resistance value of the light receiving element Q1) decreases. increases, and the capacitance value of the semiconductor variable capacitance element is changed to bring the tuning frequency of the tuning circuit closer to the frequency of the broadcasting signal. The intermediate frequency signal from the frequency amplification circuit (5) becomes larger.

Then, when the tuning frequency of the tuning circuit of the high frequency amplifier circuit (2) is completely tuned to the reception frequency, the intermediate frequency signal becomes the maximum. This is detected by the peak value detection circuit θ,
Generate a pulse signal from the peak value detection circuit 01. The pulse signal is applied to the reset terminal of the RS flip-flop 04) to reset the RS crimp-flop a<. Then, the control circuit (+49) is made inactive and stops supplying clock pulses to the up/down counter (to), so the up/down counter (i) stops counting and changes the magnitude of the signal from output circuit 01. Therefore, the tuning voltage supplied to the high frequency amplifier circuit (2) is kept constant and the tuned circuit is held at its tuned frequency.

Therefore, the broadcast signal received by the antenna (1) passes through the high frequency circuit (2) without loss, is mixed with the local oscillation signal of the local oscillation circuit (4) in the mixing circuit (3), and is converted into an intermediate frequency signal. After being amplified by an intermediate frequency amplification circuit (5), the signal is detected by a detection circuit (6) and converted into an audio signal. The audio signal is amplified by an audio amplification circuit (7) and drives a speaker (8).

(E) Effect As mentioned above, in the radio receiver of the present invention, in which tuning is performed by applying a tuning voltage to each semiconductor variable capacitance element of the high frequency amplifier circuit and the local oscillation circuit, first, the frequency of the local oscillation signal of the local oscillation circuit is The difference between the reception frequency of the first broadcast signal and the received frequency is set to the middle frequency, and then the tuning voltage applied to the semiconductor variable capacitance element of the high frequency amplifier circuit is corrected by the DC voltage control circuit, and the tuning circuit Because it is completely tuned to the frequency of the broadcast signal being received at the time, it is possible to use a semiconductor.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a radio receiver according to the present invention, and FIG. 2 is a circuit diagram showing essential parts of the present invention. (2)...High frequency amplifier circuit, (3)...Mixing circuit,
(4)...local oscillation circuit, (5)...intermediate frequency amplification circuit, (tO...tuning volume IJ, -m, @...
・DC voltage control circuit, Q3...Peak value detection circuit.

Claims (1)

[Claims] (1) A high-frequency amplification circuit whose tuning frequency can be changed by changing the capacitance of a semiconductor variable capacitance element, a mixing circuit connected to the high-frequency amplification circuit, and a semiconductor that controls the oscillation frequency of a local oscillation circuit that supplies the mixing circuit. a local oscillation circuit having a variable capacitance element, an intermediate frequency amplification circuit that amplifies an intermediate frequency signal obtained from the mixing circuit, and a tuning voltage that supplies a tuning voltage to each semiconductor variable capacitance element of the high frequency amplification circuit and the local oscillation circuit. The high frequency transmitter is controlled by signals from a generating circuit and an intermediate frequency amplifying circuit.