CS238804B1 - Breast Involvement Determining Levels of Intermodulation Products and Intermodulation Spacing of Channel and Broadband Amplifiers - Google Patents

Abstract

The invention relates to a circuit for determining the levels of intermodulation products and intermodulation gaps of channel and broadband amplifiers. The essence of the circuit according to the invention lies in the fact that a generator (1) is connected to the input of the amplifier under test (2) and either a broadband microvoltmeter (3) with a suppressed zero or a broadband level meter (4) is connected to the output of the amplifier under test (2), whereby blocks (5a, 5b) of switchable attenuators, which are switchable in steps of 0.1 dB, are connected between the generator (1) and the input of the amplifier under test (2j and between the output of the amplifier under test (2J and the broadband level meter (4).

Description

238804

The invention relates to a circuit for determining the levels of intermodulation products and inter-modulation distances of channel and wide-band amplifiers.

To the classical measurements of intermodulation intervals of the 3rd order of channel or band, or second-order intermodulation shades, is demanding instrumentation, usually three foreign generators with precisely defined pedaling, sufficient power, with an adjustable frequency and level, with a high "purity" of the output signal - ie, the content of parasitic frequencies and the highest harmonics - which are very expensive, furthermore, a high selectivity of inilivoltmeter, or a level meter and a spectrum analyzer is needed full-scale equipment for akonapr. Directional couplings, band-pass filters and the preparation of the measuring workplace as well as the measurements themselves are time-consuming and complicated.

The aforementioned drawbacks are avoided by incorporating the invention in that a generator is connected to the input of the amplifier to be measured and either a broadband microvoltmeter with a suppressed null or broadband is connected to the output of the measured amplifier. a level meter, between the generator and the input of the measured amplifier and between the output of the measured amplifier and the wideband meter level, is a switchable damping cell that is switchable after 0.1 dB.

In particular, the inventive advantages of the invention result in the fact that, compared to previously known solutions, two generators and precise high-selective milivolt-rneter, respectively, have been saved from the necessary equipment. a selective level meter, and a spectrum analyzer, wherein the power of the invention can still be used to conserve electricity using a device of the present invention. The process of measurement is simpler and faster than the current situation.

1 and 2 schematically illustrate the connection examples according to the invention.

As can be seen from FIG. 1, the connection of the underlay is formed by the measured amplifier 2 to which the generator 1 is connected, the broadband microvalter 3 being connected to the output of the amplifier 2 being suppressed with zero.

The connection according to the invention shown in FIG. 2, is formed by a generator 1 which carries a first switchable damping element block 5a connected to an input of the amplifier 2 connected to the broadband meter 4 via a second switchable damping cell 5b. In the following, the invention is explained in more detail by way of example. 2. In this circuit, the RF signal generator 1 has an adjustable output level and operates as a non-scattered, precision switchable attenuator 5 connected at the input and output measured by the amplifier 2. The broadband meter 4 has been in practical application. an oscilloscope, comprising a wideband detector, an JS amplifier, and an evaluation device - screen. In the following description, the measurement of the channel amplifier 2 in the proposed circuit is discussed, and then the wideband amplifier 2 is measured in the complementary form. In both cases, the aim is to provide the respective intermodulation distance for a certain theoretical excitation of the output of the amplifier 2 by three sine signals. resp. in the case of a channel amplifier, this is equivalent to bringing a full TV signal to its input level input given by said theoretical excitation and gain measurement of the amplifier 2 in a linear portion of the transmission characteristic.

When measured in the proposed circuit, the input of the measured channel amplifier 2 feeds from the RF generator 1 a sinusoidal signal of a certain frequency F. Using a block of damping cells 5a, 5b at the input and output of the amplifier 2 to be measured. the signal level at the input of the measured amplifier 2, below which the transmission characteristic of the measured amplifier 2, i.e. the dependence of the output voltage on the input voltage, is still linear, at the same time by using a level meter 4 the gain of the measured amplifier 2 is detected in the linear part of the transmission characteristic, or possibly known. The damping elements 5a at the input of the measured amplifier 2 are set to the maximum value after the said maximum level is detected. By decreasing the attenuation of the damping elements 5a at the input of the measured amplifier 2, the signal level at the input of the measured amplifier 2 is increased to the value S resulting from the given theoretical wake-up of the output of the measured amplifier 2, in which the 3rd order intermodulation channel, i.e. aim / K and z-measured, respectively. known gain amplifier2. By increasing the damping of the damping elements 5b at the output of the measured amplifier 2, which have previously been set to a minimum, the gain of the signal level of the amplifier output 2 is determined as compared to the input level of the amplifier 2 when the max. At the output of amplifier 2, the buffer elements 5b adjust the level deflection at meter 4, or the level drop at the output of amplifier 2 is determined from the value corresponding to the theoretically linear transmission characteristic. In this way, the exact signal level at the output of amplifier 2 is measured when one sinusoidal frequency F signal and one S level signal at its input.

Claims (2)

238804 In the inverted manner, that is, by decreasing the level of the sinusoidal signal at the input of amplifier 2, by damping links 5a of its inlet, it is determined by damping elements 5b at its output, while maintaining a constant deviation of the meter evaluation device 4, for successive on-input of the measured amplifier 2 , these levels result from an already leveled S level and harmonious analysis relationships, precisely their corresponding levels of output from the power line 2. With the above-mentioned method of wideband measured levels at the output of the amplifier 2, in practice, as well as in practical application, it is sufficient to measure 3 levels precisely, then the value of the intermodulation distance of the 3rd order of channel a, m is also determined. / For a respective intended amplification of the amplifier 2 by three sinusoidal signals or a complete TV signal. Interconnection and measurement procedure for determining the 3rd order intermodulation distance of broadband amplifiers 2, similar to the wiring and procedure for measuring channel amplifiers 2. In the case of wideband amplifiers 2, the intermodulation tones of the 3rd order of the band aini are determined. B from a different value of the level S 'of the signal of the frequency F of the input of the amplifier 2, as in the case of the TV channel amplifiers - is considered to operate the broadband amplifiers by the TV signals of the same level. In the case of the measurement of broadband amplifiers 2, in the measurement results, ni / B has a certain limited validity from the level of equivalence compared to the classical sposobumerania of intermodules - with respect to the choice of 3 frequencies in the classical measurement a, m / BV the use of wiring according to it is possible to guarantee compliance with the classical meters only if three frequencies in the interval F - 5 MHz would be mentioned in the classical measurement; F + 5 MHz. Involvement of the present invention has a wide range of applications, especially in the manufacture of channel and broadband amplifiers, type tests and acceptance tests, in laboratories, research institutes, operating laboratories, transmitters, and in the lower area. frequency, that is, wherever there is a possibility of the order of intermodulation products of the 2nd and 3rd order and, if necessary, the level of some intermodulation product or the respective intermodulation output. The connection of the invention can also be used for the direct measurement of the cross-modulation distance. pa ED Μ ET Connection for determining the levels of intermodulation products and intermodulation outputs of channel and wideband amplifiers, characterized in that a generator (1) is connected to the input of the amplifier (2) and the amplifier (2) to be measured. either a broadband micro-voltmeter (3) with suppressed zero or an inventive one-level level meter (4) is connected, between the generator (1) and the input of the measured amplifier (2) and between the output of the measured amplifier (2) and the wideband the measuring levels [4j] are connected to blocks [5a, 5b] of switchable damping cells, which can be switched in 0.1 dB, 1 sheet of drawings