Systems and methods for receiving multiple input, multiple output signals for test and analysis of multiple-input, multiple-output systems

• US 20080084951A1
• Filed: 10/06/2006
• Published: 04/10/2008
• Est. Priority Date: 10/06/2006
• Status: Abandoned Application

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Chen, Helen, Strachan, Gordon R., Lawton, Michael C., Avenell, Brian J.
• Application Number:
  US11/544,421
• Publication Number:
  US 20080084951A1
• Time in Patent Office: Days
• US Class Current: 375/347
• CPC Class Codes: H04B 17/0087 using auxiliary channels or channel simulators
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04L 1/06 using space diversity

Abstract

Systems and methods for receiving MIMO signals for testing and analyzing operation of MIMO communications devices. Examples of systems and/or methods for receiving MIMO signals include a measuring receiver with N RF paths consisting of N downconverters. Each downconverter achieves a frequency shift of the input MIMO signal equal to a shifting frequency of a first intermediate frequency (IF) plus a delta determined by the signal bandwidth multiplied by an integer number between 1 and N. The shifted N MIMO signals are combined to generate one combined analog MIMO signal. An analog to digital converter converts the combined analog MIMO signal to a stream of digital samples where the samples may be tested and analyzed with metrics on signals communicated in a MIMO environment. Example systems and method for receiving MIMO signals may also be implemented as a MIMO channel emulator such that samples generated by the ADC may be upconverted to output copies of the original signals to a receiver DUT, for example.

Claims

1. A system for receiving multiple-input, multiple output (“

MIMO”

) signals comprising;

N inputs defining N MIMO channels for receiving MIMO signals;

N downconverters to shift each MIMO signal to a shifting frequency of a first intermediate frequency plus a delta multiplied by an integer number between 1 and N;

a signal combiner to combine the shifted MIMO channel input signals to generate one combined analog MIMO signal; and

an analog to digital converter to convert the one combined analog MIMO signal to a stream of digital samples for processing as signals communicated in a MIMO environment.

2. The system of claim 1 where the N channel downconverters further comprise:

a single mixing stage for combining each MIMO input signal with a shifting frequency signal generated by a local oscillator at each channel.

3. The system of claim 1 where the N channel downcoverters further comprise:

a first mixing stage for combining each MIMO input signal with a common first IF shifting frequency signal to generate a first IF signal at each channel; and

a second mixing stage for combining each first IF signal at each channel with a second IF signal where each second IF signal frequency is Δ

*the channel number, to generate a second IF signal at each channel.

4. The system of claim 1 further comprising:

a digital signal processing block to receive the digital samples and to determine an output for the channel;

a digital to analog converter and demodulation processor for converting the digital samples back to analog form and demodulating the analog form to generate a baseband version of each MIMO channel; and

an upconverter to generate a copy of the original channel at the output for the channel.

5. The system of claim 1 where the N channel downconverters further comprise:

a single mixing stage for combining each MIMO input signal with a shifting frequency signal generated by a local oscillator at each channel.

6. The system of claim 1 where the N channel downcoverters further comprise:

a first mixing stage for combining each MIMO input signal with a common first IF shifting frequency signal to generate a first IF signal at each channel; and

a second mixing stage for combining each first IF signal at each channel with a second IF signal where each second IF signal frequency is a value, Δ

*the channel number, to generate a second IF signal at each channel.

7. A system for testing receiver functions in a first MIMO communications device comprising:

a second device to transmit MIMO signals via a plurality of transmitter antennas; and

the system of claim 4 connected to the first MIMO communications device to receive the copy of the original channel at the first MIMO communications device.

8. The system of claim 1 further comprising:

a MIMO signal measurement system to analyze the MIMO signal using selected metrics.

9. The system of claim 8 where the N channel downconverters further comprise:

a single mixing stage for combining each MIMO input signal with a shifting frequency signal generated by a local oscillator at each channel.

10. The system of claim 8 where the N channel downcoverters further comprise:

a first mixing stage for combining each MIMO input signal with a common first IF shifting frequency signal to generate a first IF signal at each channel; and

a second mixing stage for combining each first IF signal at each channel with a second IF signal where each second IF signal frequency is a value, Δ

*the channel number, to generate a second IF signal at each channel.

11. The system of claim 8 further comprising:

a high-speed data interface to a signal metrics processor, the high-speed data interface including a data fabric.

12. A system for testing receiver functions of a MIMO communications device comprising the system of claim 8 to receive MIMO signals from the MIMO communications device for analysis.

13. A method for receiving MIMO signals comprising:

receiving input signals from 1 to N MIMO channels;

shifting each input signal by a shifting frequency so that each MIMO input signal occupies a non-overlapping region of a MIMO bandwidth;

combining one or more of the shifted MIMO input signals to generate a combined, frequency multiplexed MIMO analog signal; and

converting the combined frequency multiplexed analog signal to digital samples for processing.

14. The method of claim 13 where the step of shifting each input signal comprises:

generating a first intermediate frequency signal;

generating the shifting frequency for each channel 1 to N by bandpass filtering the first intermediate frequency signal at a bandwidth delta multiplied by a corresponding integer channel number between 1 and N; and

mixing the shifting frequency with each input signal from the corresponding channel 1 to N.

15. The method of claim 13 where the step of shifting each input signal comprises:

generating the shifting frequency, F_shift for each channel 1 to N according to F_shift=F_int+delta*n, where n=a corresponding integer channel number between 1 and N;

mixing the shifting frequency for each channel with the input signal at the corresponding channel.

16. The method of claim 13 where the step of shifting each input signal comprises:

generating a first intermediate frequency signal;

mixing the first intermediate frequency signal with each input signal at each channel a mixed input frequency signal;

generating a second intermediate frequency corresponding to each channel 1 to N where each second IF frequency is Δ

multiplied by the channel number; and

mixing each second intermediate frequency at each channel number with each corresponding mixed input frequency signal.

17. A method of testing a MIMO communications device comprising:

receiving up to N input signals from up to N MIMO channels from a transmitter on the MIMO communications device;

shifting each input signal by a shifting frequency so that each MIMO input signal occupies a non-overlapping region of a MIMO bandwidth;

combining one or more of the shifted MIMO input signals to generate a combined, frequency multiplexed MIMO analog signal;

converting the combined frequency multiplexed analog signal to digital samples; and

analyzing the digital samples as MIMO signals using selected signal analysis metrics.

18. The method of claim 17 further comprising:

sending the digital samples to selected signal processing functions using a high speed data fabric.

19. A method for testing a MIMO communications device comprising:

receiving up to N input signals from up to N MIMO channels from a second MIMO communications device;

shifting each input signal by a shifting frequency so that each MIMO input signal occupies a non-overlapping region of a MIMO bandwidth;

combining one or more of the shifted MIMO input signals to generate a combined, frequency multiplexed MIMO analog signal;

converting the combined frequency multiplexed analog signal to digital samples;

demodulating the digital samples to a baseband signal of each input signal received;

upconverting each baseband signal to a copy of the input signal; and

outputting the copies of the input signals to selected outputs connected to the MIMO communications device being tested.