JPH044626A - Method for detecting leakage signal for television sensor - Google Patents

Abstract

PURPOSE:To attain accurate channel discrimination by inserting an amplifier between a reception antenna and an antenna terminal of a measurement object device, using a differential amplifier so as to amplifies signals at both ends of the amplifier differentially thereby extracting a signal having a leaked local oscillation signal at its high level. CONSTITUTION:A television sensor 3 connects between a reception antenna 1 and an antenna terminal of a measured object device 2. The input/output ratio for isolation (nearly 40dB) of an amplifier 4 in the reverse direction to amplifier 4 in the television sensor 3 is much larger than the forward gain (such as nearly 6dB). Thus, a disturbing wave for channel sensing such as a broadcast wave, a general communication wave or noise sent from the reception antenna 1 to the measured object device 2, a low level signal of nearly 6dB corresponding to the gain of the amplifier 4 is amplified as a difference signal, and conversely in the local leakage signal sent from the measured object device 2 to the reception antenna 1, the high level signal of nearly 40dB corresponding to the input/output ratio of isolation of the amplifier 4 is amplified as a difference signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for detecting a local oscillation signal in a television sensor for measuring television audience ratings.

[Conventional technology]

In order to automatically measure television audience ratings, a device called a television sensor is generally attached to a device to be measured, such as a sample home television set or video tape recorder, and the on/off information and channel information of the device to be measured are collected. etc., are collected in relation to time information, and periodically sent to a computer at the center using a telephone line.

By the way, as one of the effective methods for collecting channel information, a method is known that uses a local oscillation signal of a receiving circuit of a device to be measured. Since this corresponds to the frequency of the local oscillation signal of the receiving channel of the device to be measured and the local oscillation signal of its receiving circuit, the local oscillation signal is detected,
The receiving channel is determined from the frequency and the like.

Note that there are various methods for detecting local oscillation signals from the device under test. There are methods to take out the lead wires by directly soldering them to the circuit board in the device under test, and methods to connect the pickup coil close to the circuit. However, these methods are undesirable because they require modification to the device under test that is owned by an individual, and therefore, local oscillation signals (local oscillation leakage signals) leaking from the antenna terminal of the device under test are undesirable. It is considered desirable to use the method. In other words, when using the local oscillation signal leaking from the antenna terminal of the device to be measured, installation can be completed by simply connecting the TV sensor between the device to be measured in the sample home and the receiving antenna using a connector etc. This is because there is no need to modify the inside of the device to be measured, and the occurrence of trouble can be minimized.

[Problem to be solved by the invention]

As mentioned above, the method of using local oscillation leakage signals for channel sensing is preferable, but in addition to the local oscillation leakage signals, the signals extracted from the antenna terminal of the device to be measured include broadcast waves, This system contains many interference waves for channel sensing such as communication waves and noise, and if these components cannot be sufficiently separated, channel determination becomes impossible or errors occur.

The present invention was developed in view of the above points, and its purpose is to sufficiently separate interference waves such as broadcast waves, general communication waves, and noise so that accurate channel determination can be performed. It is an object of the present invention to provide a method for detecting a local leakage signal of a television sensor, which can perform the following steps.

[Means to solve the problem]

In order to achieve the above object, the present invention amplifies the signal of the receiving antenna using a low gain amplifier and applies it to the antenna terminal of the device to be measured, and differentially amplifies the signals at both ends of the amplifier using a differential amplifier for measurement. Local oscillation signals leaking from the target device are detected.

That is, the present invention focuses on the fact that the input/output ratio of the isolation that the amplifier has in the reverse direction is very large compared to the gain in the forward direction. By inserting an amplifier and differentially amplifying the signals at both ends of the amplifier using a differential amplifier, a signal containing a high level of local oscillation signal leaking from the device to be measured is extracted.

[Effect]

In the method for detecting a local leakage signal of a television sensor according to the present invention, a low gain amplifier amplifies a signal from a receiving antenna and supplies the amplified signal to an antenna terminal of a device to be measured, and a differential amplifier amplifies signals at both ends of the amplifier. It differentially amplifies and outputs a signal containing a high level local oscillation signal leaking from the device under test.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a television sensor to which the method for detecting a local leakage signal of a television sensor of the present invention is applied. In FIG. 1, the television sensor 3 of this embodiment has a terminal T1 connected to a receiving antenna 1 and a terminal T2 connected to an antenna terminal of a device 2 to be measured such as a television set or a video tape recorder. It is connected between the receiving antenna 1 and the antenna terminal of the device to be measured 2 .

The television sensor 3 also has a low-gain amplifier 4 connected between terminals T1 and 72 in a forward direction from the receiving antenna 1 toward the device to be measured 2, and a difference in which signals from both ends of the amplifier 4 are input. It is composed of a dynamic amplifier 5, an attenuator 6 that attenuates the output signal of the differential amplifier 5 to an appropriate level, and a television sensor main circuit section 7 that performs channel full determination based on the detected local oscillation signal. .

In operation, broadcast waves, general communication waves, noise, etc. arriving at the receiving antenna 1 are uniformly amplified at a low gain (for example, about 6 dB) by the amplifier 4, and then supplied to the antenna terminal of the device to be measured 2. . Among these signals, the broadcast waves are tuned by a tuner (not shown) in the measurement target device 2, and the television broadcast is received.

On the other hand, a local oscillation signal is leaking from the internal tuner to the antenna terminal of the device to be measured 2, and this signal is caused by the isolation input/output ratio of the amplifier 4 (for example, 40d
(approximately B) is large, so only a very small amount is fed back to the input side of the amplifier 4.

Here, the differential amplifier 5 differentially amplifies the signals at both ends of the amplifier 4, but in differential amplification, an output corresponding to the difference between the two is produced regardless of the absolute values of the signals applied to both input terminals. Broadcast waves and general communication waves transmitted from the receiving antenna 1 to the measurement target device 2 side.

Interfering waves such as noise for channel sensing are a low level signal of about 6 dB corresponding to the gain of the amplifier 4, which is amplified as a difference signal, and conversely, a local leakage signal transmitted from the device to be measured 2 to the receiving antenna 1 side. A high level signal of about 40 dB, which corresponds to the isolation input/output ratio of the amplifier 4, is amplified as a difference signal.

Therefore, considering the level difference between the interference wave included in the output signal of the differential amplifier 5 and the local leakage signal, it is 40 dB-6 dB.
= 36 dB, and sufficient separation is possible. In this embodiment, the A7 tenator 6 attenuates the level of the interference wave to the extent that it is not detected by the subsequent TV sensor main circuit 7, and only the local leakage signal is detected. is applied to the television sensor main circuit section 7.

Then, the television sensor main circuit section 7 determines the receiving channel of the measurement target device 2 based on the detected local leakage signal, and uses it as part of the audience rating measurement data.

In the above embodiment, the gain of the amplifier 4 is set to 6.
Although it has been explained that the value is about dB, it is not limited to this, and if it can be set to, for example, OdB, it is theoretically possible to prevent interference waves from appearing in the output of the differential amplifier 5. Furthermore, the isolation input/output ratio of the amplifier 4 is not limited to 40 dB, but generally 30 dB or more can be easily obtained.

〔Effect of the invention〕

As explained above, in the method for detecting a local leakage signal of a television sensor according to the present invention, the input/output ratio of the isolation that the amplifier has in the reverse direction is extremely large compared to the gain in the forward direction. By inserting an amplifier between the receiving antenna and the antenna terminal of the device to be measured, and differentially amplifying the signals at both ends of this amplifier using a differential amplifier, we can eliminate the local oscillation signal leaking from the device to be measured. Since signals containing high levels are extracted, it is possible to sufficiently separate interference waves for channel sensing such as broadcast waves, general communication waves, and noise, which has the effect of allowing accurate channel determination.

In addition, in differential amplification, the difference between two input signals is amplified regardless of the absolute value of the input signal, so it is possible to extract the local leakage signal, which has amplitude variations for each channel, as a signal with a stable amplitude. This also has the effect of making channel determination more stable.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a television sensor to which the method for detecting a local leakage signal of a television sensor of the present invention is applied. In the figure, 1...Receiving antenna 2...Device to be measured 3...TV sensor 4...Amplifier 5...Differential amplifier 6 ...Attenuator 7...TV sensor main circuit diagram 1

Claims (1)

[Claims] The signal of the receiving antenna is amplified by a low gain amplifier and applied to the antenna terminal of the device to be measured, and the signals at both ends of the amplifier are differentially amplified by a differential amplifier to detect the local oscillation signal leaking from the device to be measured. A method for detecting a local leakage signal from a television sensor, characterized by the following.