JPH02253714A - Receiver - Google Patents

Abstract

PURPOSE:To exactly execute a search stop by providing a first logic circuit to AND between the zero point detection signal of a signoidal characteristic voltage, which is obtained from an FM frequency detection signal, and the level detection signal of an intermediate frequency circuit and executing the search stop according to a signal from this first logic circuit. CONSTITUTION:Since a signoidal characteristic voltage Vs is outputted from an FM frequency detection circuit 5 and inputted to comparators 7 and 8, an output voltage Va is made 'L' in the non-inversion comparator 7 when the voltage Vs lower than a reference voltage V1 is inputted. Then, in the inversion comparator 8, when the voltage Vs higher than a reference voltage V2 in inputted, an output voltage Vb is made 'L'. In an intermediate frequency circuit 4, when an intermediate frequency signal effectively exists, the level of a voltage Vc in a terminal 4a is lowered to 'L'. Thus, a pulse Vd showing a central frequency can be extremely exactly taken out by suitably setting the reference voltages V1 and V2 of the comparators 7 and 8 and the search stop can be exactly executed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a receiving device having a search function.

(Prior art) In this type of receiving device, the tuning frequency (local oscillation frequency)
A search mechanism is adopted in which the search is continuously changed (searched) and the search is stopped when a broadcast is received. And this search stop is the 8
This is done by detecting the zero point of the voltage with the characteristic

[Problem to be solved by the invention]

However, this search mechanism has a problem in that erroneous detection occurs in the zero point detection of the character 8 characteristic, and erroneous search stops are likely to occur.

An object of the present invention is to enable the search to be stopped accurately.

[Means to solve the problem]

To this end, the present invention provides, in a receiver having a search function, a first logic circuit that takes the AND of the zero point detection signal of the figure-8 characteristic voltage obtained from the FM detection circuit and the level detection signal of the intermediate frequency circuit. Equipped with 1. The configuration is such that the search is stopped by a signal from the first logic circuit.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a diagram showing a chainer portion of one embodiment.

1 is a high frequency amplifier circuit that amplifies a high frequency signal (5 to 8.5 MHz); 2 is a high frequency amplifier circuit that amplifies a high frequency signal (5 to 8.5 MHz); 7M) A mixing circuit for extracting an intermediate frequency signal of Iz, 4 is an intermediate frequency amplification circuit, and 5 is an FM detection circuit.

In the PLL circuit 3, the frequency division ratio of an internal frequency dividing circuit is changed by a control section 6 made up of a microcomputer, and the frequency output to the mixing circuit 2 is changed. 7 is a non-inverting comparator that compares the S-shaped specific voltage Vs obtained by the FM detection circuit 5 with a reference voltage v1, and 8 is an inverting comparator that compares the S-shaped specific voltage Vs with a reference voltage 2.

Reference numeral 9 denotes a Nandts gate that takes the AND of the output signal from the comparator 7.8 and the output signal of the intermediate frequency signal level detection terminal (level meter connection terminal) 4a of the above-mentioned intermediate frequency circuit 4. signal “H”
As a result, the control circuit 6 stops searching for the PLL circuit 3.

Now, the above-mentioned FM detection circuit 5 outputs a voltage Vs having a figure-8 characteristic as shown in FIG.
8, so in the non-inverting comparator 7,
When a voltage Vs lower than the reference voltage 1 is input, the output voltage Va becomes "L", and when a voltage Vs higher than the reference voltage V2 is applied to the inverting comparator 8, the output vb becomes "L".

Further, in the intermediate frequency circuit 4, if the intermediate frequency signal is effectively present, the level of the voltage Vc at the terminal 4a decreases to "L".

Therefore, when a regular signal is received, the Nantes gate 9 outputs a pulse Vd indicating the frequency range of Δf including the center frequency of the zero point, as shown in FIG. As a result, the PLL circuit 3 is commanded to stop the frequency change (stop the search).

Therefore, the standard for comparator 7.8! By appropriately setting the pressures V1 and (2), it is possible to extract the pulse Vd that indicates the center frequency extremely accurately, and it is possible to accurately stop the search.

〔Effect of the invention〕

As explained above, according to the present invention, there is an advantage that the center frequency when a broadcast is received can be detected extremely accurately, and the search can be stopped accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a tuner according to an embodiment of the present invention, and FIG. 2 is a timing chart for explaining its operation. Agent Patent Attorney Tsuneaki Nagao Figure 2 +V d H1 L--111

Claims (4)

[Claims] (1) A receiving device having a search function, comprising a first logic circuit that takes an AND of a zero point detection signal of an S-characteristic voltage obtained from an FM detection circuit and a level detection signal of an intermediate frequency circuit, A receiving device characterized in that a search is stopped by a signal from the first logic circuit. (2) The circuit for zero point detection includes a non-inverting comparator to which the S-characteristic voltage is input, an inverting comparator to which the S-characteristic voltage is input, and a second Claim 1, characterized in that the reference voltage of the non-inverting comparator and the reference voltage of the inverting comparator are set to a voltage slightly shifted from the zero point of the S-characteristic voltage. receiving device. (3) The reference voltage of the non-inverting comparator and the reference voltage of the inverting comparator are set to voltages shifted in opposite directions from the zero point of the S-characteristic voltage. Receiving device. (4) The receiving device according to claim 1, wherein the level signal of the intermediate frequency circuit is obtained from a level meter terminal.