SU698132A1 - Device for simulating multi-beam radio channel - Google Patents

Description

The invention relates to the field of transmissions: signals, in particular to devices for simulating a multipath radio channel, and can be used in laboratory tests of radio communication systems with mobile, objects, for example, with airplanes operating in a multipath radio channel if there is a direct one: o and reflected rays.

A device is known that simulates a multibeam radio channel with direct and reflected beams, containing successively the first tunable generator, the input frequency mixer, the first and second delay lines. Each of the taps of the second delay line is connected via a series-connected reflection unit and an auxiliary attenuator to the corresponding input of the first adder. The device also includes a first attenuator, a second adder, a second attenuator, and a third adder, the noise generator input signal is connected to another input, sequentially connected second tunable oscillator and additional frequency mixer, as well as a harmonic wave generator 1.

However, the relative Dohascher shift between the frequencies of the direct and reflected beams in a known device is simulated by changing the frequency of one of the tunable generators relative to the frequency of the second tunable oscillator so that their difference of frequencies is equal to the relative Doppler frequency. In such a simulation of the relative Doppler shift, the accuracy of the simulation depends on the stability of the tunable oscillators.

The purpose of the invention is to improve the accuracy of modeling the relative Doppler shift between the frequencies of the direct and reflected rays.

For this purpose, a device for simulating a multipath radio channel with direct and reflected beams, containing pos; Consistently connected are a first tunable oscillator, an input frequency mixer, a first delay line and a second delay line, each of whose taps through a series of reflected reflection unit. the beam and auxiliary attenuator is connected to the corresponding input of the first sum of the torus, the first attenuator, the second adder, the second attenuator and the third combinator are connected in series; the output of the noise signal generator connected in series to the second tunable generator and optionally frequency mixer as well as the generator are connected to another input harmonic signals, the first balanced modulator and sequentially connected phase shifter, the second balanced modulator, the fourth adder and rety attenuator, whose output is connected to another input of the second adder. The output of the frequency mixer is connected to the input of the phase shifter and to one of the inputs of the first balanced modulator, to the other input of which and to the other input of the second balanced modulator the corresponding outputs of the harmonic signal generator are connected. The output of the first balanced modulator is connected to another input of the fourth adder. The output of the first summatr is connected to the input of the first attenuator, and the output of the third adder is connected to another input of the additional frequency mixer, the output of which is the output of the device. The drawing shows a structural electrical circuit of the proposed device. A device for simulating a multipath radio channel contains an input mixer of I frequencies, a first tunable generator 2, a first delay line 3, a second delay line 4, a reflected beam forming unit 5, auxiliary attenuators 6, a first adder 7, a first attenuator 8, a phase shifter 9, first and second balanced modulators 10, 11, generator 12 harmonic signals, second adder 13, second attenuator 14, third adder 15, third attenuator 16, fourth adder 17, noise signal generator 18, additional mixer 19 h and the second tunable oscillator 20. The device operates as follows. The input signal is fed to one of the inputs of the input mixer 1 frequency, the second input of which is connected to the output of the first tunable oscillator 2. The frequency detuning of the oscillator 2 simulates the change in the Pre-Shger frequency shift of the input signal. At the same time, the execution of the input circuits with the wideband and the presence of the generator 2 with a frequency tunable in a wide range extend the frequency range and the input signal of the device. This allows testing of different communication systems, which differ from one another in the frequencies of the signals arriving at the input of the device. By a frequency mixer 1 and generator 2, the input signal is converted to an intermediate frequency of the device. From the output of the frequency mixer 1, the signal is branched along the direct and reflected paths. In the path of the reflected rays, the signal arrives at the input of the first delay line 3, the delay time of which determines the delay of the reflected rays with respect to the forward one. Line 3 of the delay can be made switchable to change the amount of delay. The second delay line 4 determines the variation in the delay time of the reflected rays relative to each other with an appropriate connection to it. the taps of the reflected beam forming units 5, the outputs of which through auxiliary attenuators 6, allowing to adjust the level of each reflected beam, are connected to the inputs of the first adder 7 The first attenuator 8 connected to the output of the first adder allows you to adjust the level of the total signal of the reflected beams. In the direct beam path, the signal from the output of the mixer 1 frequency through the phase shifter 9 on / G / 2 is fed to the input of the second balanced modulator 11. At the same time from the output of the mixer 1 frequency, the signal arrives at the input of the first balanced modulator 10. The second inputs of the balanced modulators, 10 and 11 are each connected to its generator output of 12 harmonic signals having two quadrature outputs SitlUJ t and cosuu.ot. The outputs of the balanced modulators 10 and 11 are connected to the inputs of the fourth adder 17. The frequency of the signal at the output of the fourth adder 17 differs from the frequency of the signal at the output of mixer 1 frequency by the value of ao If, for simplicity, assume that si And c is the signal at the output of mixer 1 frequency , then blocks 9–12 and 17 perform the frequency shift operator by realizing a mathematical transformation Ш 5iti 4Jj, t OOS ŠQo-t - i; cosajj.t sinuUajj-t 6inCuj (. + u;, joH, And f; - frequency of the input signal, rp is relative to the Doppler frequency. As a result, in the forward beam path The signal frequency of the antenna is t (JUc, and in the path of the reflected rays the frequency of the signal oi remains unchanged. The difference between the frequencies of the signals of the direct and reflected rays is s. The accuracy of the simulation of the relative loopspoBCKoro shift between frequencies is determined by the generator of 12 harmonic signals and is achieved at low requirements to its stability. The signal of the direct beam from the output of the fourth adder 17 through the third attenuator 16, designed to set the level of the direct beam, and the signal of reflected rays from the output of the first attenuator 8 go to the corresponding inputs of the second adder 13. The summed signal of the visible and reflected beams from the output of the adder 13 through the second attenuator 14 is fed to one of the inputs of the third adder 15. The adder 15 is designed to add the total matching line of the direct and reflected beams with the generator noise x signals 18. Attenuator 14 simulates the total attenuation in the radio channel, i.e. signal / pgum ratio The total signal of the direct and reflected beams, as well as the noise signal, arrive at the first input of the additional mixer 19 frequencies. The second input of the mixer 19 frequencies is connected to the output of the second tunable generator 20, which is used to transfer the frequency of the input signal of the frequency mixer 19 to the output frequency of the device. The frequency of the output signal of the device can be varied over a wide range through the use of a broadband accessory mixer 19. frequency and second tunable generator 20.

Claims (1)

Invention Formula A device for simulating a multipath radio channel with direct and reflected beams, containing in series the first tunable generator, the input frequency mixer, the first delay line And the second delay line,.-Each (and t taps of which are connected through the series-connected block of the n-1fraction of the reflected beam and auxiliary attenuator to the corresponding input of the first one from the mmator, sequentially connected to the first attenuator, second adder, second attenuator and third adder The other input of which is connected to the output of the generator of noise signals, successively connecting the second tunable generator and the additional frequency mixer, as well as the generator of harmonic signals, differing from Then, in order to increase the accuracy of modeling the relative Doppler shift between the frequencies of the direct and reflected rays, the first balanced modulator was introduced and connected in series by the phase shifter, the second binster modulator, the fourth adder and the third attenuator, the output of which is connected to another input of the second adder, while the output of the input mixer frequency is connected to the input of the phase shifter and to one of the inputs of the first balanced mod.chory, to another input of which and to the other of the second balanced modulator under the keys correspond to the outputs of the harmonic signal generator, the output of the first balanced modulator is connected to another input of the fourth adder, the output of the first adder is connected to the input of the first attenuator, and the output of the third adder is connected to another input of the additional mixer, the output of which is input of the device. . History of Information, taken into consideration during examination i. Hov4qr (aC.ScibNey, memt) e, r-3EtE, ana Chi-istoplier B.Tluncomt) TranSQCtions oti Communications, vot.com -23, / Vo7,  -1975, pp-695-705. Sincjc SinUJgo / 2 P Sh GN