US 5,862,455 A · Fading simulator

Abstract

A fading simulator for generating multipath-faded test signals which have attenuation notches of precisely controllable frequency position and attenuation depth from a modulated input signal of known bandwidth. The input signal is fed to a splitter that directs two in-phase components to a first path and a second path. The input to each path is divided by a splitter into in-phase and quadrature sub-signals having a quadrature phase relationship, each sub-signal being fed to a respective inverting attenuator, the outputs of the attenuators then being combined in a combiner and the combined output being passed through a variable delay line to generate the output of the respective path. The outputs of each path are then combined in a combiner circuit to generate the multipath-faded test signal. All four inverting attenuators are preferably substantially identical to one another so that the two paths have close to identical temperature-drift and other characteristics. The attenuators and delay lines are electronically controlled in tandem, preferably using a microprocessor and stored program, to generate precision, static or dynamic, attenuation notches desired.

Claims10

Dependent claims

A fading simulator for generating multipath-faded test signals having attenuation notches of controllable frequency position and attenuation depth, from a modulated input signal of known bandwidth, comprising:

first and second signal paths extending in parallel between input circuit means at which the paths diverge and output circuit means at which the paths converge;
first electronically-controllable inverting attenuator means connected in said first path, said first electronically-controllable inverting attenuator means having a given temperature characteristic for effecting dynamic attenuation and phase-shifting of the signal in said first path;
second electronically-controllable inverting attenuator means connected in said second path, said second electronically-controllable inverting attenuator means also having a temperature characteristic similar to said given temperature characteristic for effecting dynamic attenuation and phase-shifting of the signal in said second path;
a first delay line having a given electrical length, said first delay line being connected in series with said first electrically-controllable inverting attenuator means in said first path;
a second delay line having a given electrical length, said second delay line being connected in series with said second electrically-controllable inverting attenuator means in said second path;
and
electronic control means connected to said first and second delay lines for controlling the respective electrical lengths thereof, said electronic control means also being connected to said first and second electrically-controllable inverting attenuator means for controlling said first and second electrically-controllable inverting attenuator means in tandem such that one is adjusted relative to the other to ensure that a test signal is generated having a desired notch depth and position.

4 more elements

first and second signal paths extending in parallel between input circuit means at which the paths diverge and output circuit means at which the paths converge;
first electronically-controllable inverting attenuator means connected in said first path for effecting dynamic attenuation and phase-shifting of the signal in said first path;
second electronically-controllable inverting attenuator means connected in said second path for effecting dynamic attenuation and phase-shifting of the signal in said second path;
a first delay line having a given electrical length, said first delay line being connected in series with said first electrically-controllable inverting attenuator means in said first path;
a second delay line having a given electrical length, said second delay line being connected in series with said second electrically-controllable inverting attenuator means in said second path;
and
electronic control means connected to said first and second electronically-controllable inverting attenuator means, for controlling said first and second electronically-controllable inverting attenuator means in tandem, said electronic control means also being connected to said first and second delay lines for controlling the respective electrical lengths thereof, so as to generate a desired test signal,
wherein each of said first and second electronically-controllable inverting attenuator means comprises:
a splitter circuit having an input, a first output and a second output, said splitter circuit being adapted to reproduce a signal received on the input of said splitter circuit as a first output signal on said first output and a second output signal on said second output of said splitter circuit, said first and second output signals being in a quadrature relationship to one another;
an electronically-controllable primary inverting attenuator connected to said first output, said electronically-controllable primary inverting attenuator having an output;
an electronically-controllable secondary inverting attenuator connected to said second output, said electronically-controllable secondary inverting attenuator having an output;
and
a combiner circuit connected to receive and combine said outputs of said electronically-controllable primary inverting attenuator and said electronically-controllable secondary inverting attenuator.

10 more elements

first and second signal Paths extending in parallel between input circuit means at which the paths diverge and output circuit means at which the paths converge;
first electronically-controllable inverting attenuator means connected in said first path for effecting dynamic attenuation and phase-shifting of the signal in said first path;
second electronically-controllable inverting attenuator means connected in said second path for effecting dynamic attenuation and phase-shifting of the signal in said second path;
a first delay line having a given electrical length, said first delay line being connected in series with said first electrically-controllable inverting attenuator means in said first path;
a second delay line having a given electrical length, said second delay line being connected in series with said second electrically-controllable inverting attenuator means in said second path;
and
electronic control means connected to said first and second electronically-controllable inverting attenuator means, for controlling said first and second electronically-controllable inverting attenuator means in tandem, said electronic control means also being connected to said first and second delay lines for controlling the respective electrical lengths thereof, so as to generate a desired test signal,
wherein:
said input circuit means is adapted to divide the modulated input signal into first and second path-input signals having a quadrature phase relationship to one another;
and
wherein each of said first and second electronically-controllable inverting attenuator means comprises:
a splitter circuit having an input, a first output and a second output;
an electronically-controllable primary inverting attenuator connected to said first output, said electronically-controllable primary inverting attenuator having an output;
an electronically-controllable secondary inverting attenuator connected to said second output, said electronically-controllable secondary inverting attenuator having an output;
and
a combiner circuit having a first input and a second input, said first input being connected to said output of said electronically-controllable primary inverting attenuator, and said second input being connected to said output of said electronically-controllable secondary inverting attenuator.

13 more elements

first and second signal paths extending in parallel between input circuit means at which the paths diverge and output circuit means at which the paths converge;
first electronically-controllable inverting attenuator means connected in said first path for effecting dynamic attenuation and phase-shifting of the signal in said first path;
second electronically-controllable inverting attenuator means connected in said second path for effecting dynamic attenuation and phase-shifting of the signal in said second path;
a first delay line having a given electrical length, said first delay line being connected in series with said first electrically-controllable inverting attenuator means in said first path;
a second delay line having a given electrical length, said second delay line being connected in series with said second electrically-controllable inverting attenuator means in said second path;
and
electronic control means connected to said first and second electronically-controllable inverting attenuator means, for controlling said first and second electronically-controllable inverting attenuator means in tandem, said electronic control means also being connected to said first and second delay lines for controlling the respective electrical lengths thereof, so as to generate a desired test signal,
wherein said input circuit means is adapted to divide the modulated input signal into first and second path-input signals each having an in-phase relationship, and wherein each of said first and second electronically-controllable inverting attenuator means comprises:
a splitter circuit having an input, a first output and a second output, said splitter circuit being adapted to reproduce a signal received on said input of said splitter circuit as a first output signal on said first output and a second output signal on said second output of said splitter circuit, said first and second output signals being in a quadrature relationship to one another;
an electronically-controllable primary inverting attenuator connected to said first output, said electronically-controllable primary inverting attenuator having an output;
an electronically-controllable secondary inverting attenuator connected to said second output, said electronically-controllable secondary inverting attenuator having an output;
and
a combiner circuit having a first input and a second input, said first input being connected to said output of said electronically-controllable primary inverting attenuator, and said second input being connected to said output of said electronically-controllable secondary inverting attenuator.

10 more elements

A method of generating a multipath-faded test signal, having an attenuation notch of controllable frequency position and attenuation depth, from a modulated input signal of known bandwidth, the method comprising the steps of:

dividing the input signal into first and second signal components;
adjusting a phase and amplitude of said first signal component by using a first electronically-controllable inverting attenuator;
delaying said first signal component for a predetermined time by using a first delay line;
adjusting a phase and amplitude of said second signal component by using a second electronically-controllable inverting attenuator;
delaying said second signal component for a predetermined time by using a second delay line;
combining the adjusted and delayed first and second signal components to produce a multipath-faded test signal;
and
employing microprocessor means to jointly control said first and second electronically-controllable inverting attenuators and said first and second delay lines to generate a desired attenuation notch within said test signal,
wherein the phase and amplitude of each of said first and second signal components is adjusted by the following steps:
subdividing each of said first and second signal components into primary and secondary sub-component signals;
adjusting the phase and amplitude of said primary sub-component signals by using a primary inverting attenuator;
adjusting the phase and amplitude of said secondary sub-component signals by using a secondary inverting attenuator;
and
combining the adjusted primary and second sub-component signals to form the output of the respective first and second electronically-controllable inverting attenuators.

11 more elements

Dependencies are inferred from the claim text.

Fading simulator

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Fading simulator

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Abstract

Claims10