Frequency spectrum analyzing apparatus and transmitter characteristics measuring apparatus using the same

• US 5,706,202 A
• Filed: 03/05/1996
• Issued: 01/06/1998
• Est. Priority Date: 03/08/1995
• Status: Expired due to Term

• Current Assignee: Anritsu Corporation
• Original Assignee: Anritsu Corporation
• Inventors: Itahara, Hiroshi, Seike, Takashi
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): Wachsman, Hal D.
• Application Number:
  US08/611,241
• Time in Patent Office: 672 Days
• Field of Search: 364/484-487, 364/178, 364/572, 364/575, 364/576, 364/724.01, 364/724.13, 364/726, 324/76.15, 324/76.13, 324/76.19, 324/76.21-76.24, 324/76.26, 324/76.27, 324/76.28, 324/76.38, 324/76.41, 324/76.42, 324/76.43 , 324/76.44, 324/76.45, 324/76.47, 324/76.58, 324/76.59, 370/208, 370/210, 375/224
• US Class Current: 702/77
• CPC Class Codes: G01R 23/16 Spectrum analysis; Fourier analysis

Abstract

In a frequency spectrum analyzing apparatus which utilizes a DFT (discrete Fourier transform) filter bank, and can detect the peak value of the amplitude of an input signal, a time sequence signal generation circuit samples an input signal to convert it into a time sequence signal. A memory stores the time sequence signal. The DFT filter bank receives a time sequence signal read out from the memory by a control device, and performs DFT filter bank processing corresponding to a plurality of desired frequencies while shifting a window function by a predetermined number of sample point units. An absolute value calculation unit calculates absolute values in units of outputs from the DFT filter bank. A peak value detection unit detects peak values in units of outputs from the absolute value calculation unit. A display device displays the frequency spectrum on the basis of these peak values.

Claims

1. A frequency spectrum analyzing apparatus comprising:

a time sequence signal generator for generating a time sequence signal by sampling a signal to be measured;

a storage device for storing the time sequence signal generated by said time sequence signal generator;

a discrete Fourier transform (DFT) filter bank for receiving a signal read out from said storage device in a desired closed time period of the time sequence signal stored in said storage device, for calculating a discrete Fourier transform of the read out signal so that bandpass filter processing of the signal is performed in correspondence with a plurality of desired frequencies, and for outputting processing results in parallel for the plurality of desired frequencies;

an absolute value calculator for calculating absolute values of the processing results for each of a plurality of outputs from said DFT filter bank; and

a peak value detector for detecting peak values of the absolute values in units of outputs from said absolute value calculator, and for outputting the peak values in correspondence with the plurality of desired frequencies;

wherein said time sequence signal generator comprises;

a local oscillator for oscillating a local signal having a predetermined frequency;

a phase shifter for shifting a phase of the local signal oscillated by said local oscillator through 90°

;

a first mixer for mixing the signal to be measured with the 90°

phase-shifted local signal shifted by said phase shifter, and for outputting a first intermediate frequency (IF) signal;

a first bandpass filter for limiting a frequency band of the first IF signal output by said first mixer;

a first analog/digital converter for sampling the first IF signal band-limited by said first bandpass filter, and for outputting a first time sequence signal;

a second mixer for mixing the signal to be measured with the local signal oscillated by said local oscillator, and for outputting a second IF signal which has an orthogonal relationship with respect to the first IF signal;

a second bandpass filter for limiting a frequency band of the second IF signal output by said second mixer; and

a second analog/digital converter for sampling the second IF signal band-limited by said second bandpass filter, and for outputting a second time sequence signal which has an orthogonal relationship with respect to the first time sequence signal.

2. A frequency spectrum analyzing apparatus comprising:

a time sequence signal generator for generating a time sequence signal by sampling a signal to be measured;

a storage device for storing the time sequence signal generated by said time sequence signal generator;

a discrete Fourier transform (DFT) filter bank for receiving a signal read out from said storage device in a desired closed time period of the time sequence signal stored in said storage device, for calculating a discrete Fourier transform of the read out signal so that bandpass filter processing of the signal is performed in correspondence with a plurality of desired frequencies, and for outputting processing results in parallel for the plurality of desired frequencies;

an absolute value calculator for calculating absolute values of the processing results for each of a plurality of outputs from said DFT filter bank; and

a peak value detector for detecting peak values of the absolute values in units of outputs from said absolute value calculator, and for outputting the peak values in correspondence with the plurality of desired frequencies;

wherein said time sequence signal generator comprises;

an analog/digital (A/D) converter for sampling the signal to be measured at a predetermined sampling timing, and for outputting a time sequence signal;

an orthogonal carrier sequence generation circuit for generating an orthogonal carrier sequence signal including real and imaginary components;

a first multiplier for multiplying the time sequence signal output by said A/D converter with the real component of the orthogonal carrier sequence generated by said orthogonal carrier sequence generation circuit, and for outputting in-phase data;

a first bandpass filter for performing a first band limitation for removing components other than a baseband component from the in-phase data output by said first multiplier, and for outputting the first band-limited data;

a second multiplier for multiplying the time sequence signal output by said A/D converter with the imaginary component of the orthogonal carrier sequence generated by said orthogonal carrier sequence generation circuit, and for outputting orthogonal data; and

a second bandpass filter for performing a second band limitation for removing components other than a baseband component from the orthogonal data output by said second multiplier, and for outputting the second band-limited data.

3. A frequency spectrum analyzing apparatus comprising:

a time sequence signal generator for generating a time sequence signal by sampling a signal to be measured;

a storage device for storing the time sequence signal generated by said time sequence signal generator;

a controller for reading out a signal of the time sequence signal stored in said storage device corresponding to a desired closed time period;

a discrete Fourier transform (DFT) filter bank for calculating a discrete Fourier transform of the signal of the desired period read out from said storage device by said controller so that bandpass filter processing of the read out signal is performed in correspondence with a plurality of desired frequencies while shifting a window function by a predetermined sample point interval, and for outputting processing results in parallel for the plurality of desired frequencies;

an absolute value calculator for calculating absolute values of the processing results for each of a plurality of outputs from said DFT filter bank;

a peak value detector for detecting peak values of the absolute values in units of outputs from said absolute value calculator, and for outputting the peak values in correspondence with the plurality of desired frequencies; and

a display for displaying the peak values output from said peak value detector in correspondence with the plurality of desired frequencies;

wherein said time sequence signal generator comprises;

a local oscillator for oscillating a local signal having a predetermined frequency;

a phase shifter for shifting a phase of the local signal oscillated by said local oscillator through 90°

;

a first mixer for mixing the signal to be measured with the 90°

phase-shifted local signal shifted by said phase shifter, and for outputting a first intermediate frequency (IF) signal;

a first bandpass filter for limiting a frequency band of the first IF signal output by said first mixer;

a first analog/digital converter for sampling the first IF signal band-limited by said first bandpass filter, and for outputting a first time sequence signal;

a second mixer for mixing the signal to be measured with the local signal oscillated by said local oscillator, and for outputting a second IF signal which has an orthogonal relationship with respect to the first IF signal;

a second bandpass filter for limiting a frequency band of the second IF signal output by said second mixer; and

a second analog/digital converter for sampling the second IF signal band-limited by said second bandpass filter, and for outputting a second time sequence signal which has an orthogonal relationship with respect to the first time sequence signal.

4. A frequency spectrum analyzing apparatus comprising:

a time sequence signal generator for generating a time sequence signal by sampling a signal to be measured;

a storage device for storing the time sequence signal generated by said time sequence signal generator;

a controller for reading out a signal of the time sequence signal stored in said storage device corresponding to a desired closed time period;

a discrete Fourier transform (DFT) filter bank for calculating a discrete Fourier transform of the signal of the desired period read out from said storage device by said controller so that bandpass filter processing of the read out signal is performed in correspondence with a plurality of desired frequencies while shifting a window function by a predetermined sample point interval, and for outputting processing results in parallel for the plurality of desired frequencies;

an absolute value calculator for calculating absolute values of the processing results for each of a plurality of outputs from said DFT filter bank;

a peak value detector for detecting peak values of the absolute values in units of outputs from said absolute value calculator, and for outputting the peak values in correspondence with the plurality of desired frequencies; and

a display for displaying the peak values output from said peak value detector in correspondence with the plurality of desired frequencies;

wherein said time sequence signal generator comprises;

an analog/digital (A/D) converter for sampling the signal to be measured at a predetermined sampling timing, and for outputting a time sequence signal;

an orthogonal carrier sequence generation circuit for generating an orthogonal carrier sequence signal including real and imaginary components;

a first multiplier for multiplying the time sequence signal output by said A/D converter with the real component of the orthogonal carrier sequence generated by said orthogonal carrier sequence generation circuit, and for outputting in-phase data;

a first bandpass filter for performing a first band limitation for removing components other than a baseband component from the in-phase data output by said first multiplier, and for outputting the first band-limited data;

a second multiplier for multiplying the time sequence signal output by said A/D converter with the imaginary component of the orthogonal carrier sequence generated by said orthogonal carrier sequence generation circuit, and for outputting orthogonal data; and

a second bandpass filter for performing a second band limitation for removing components other than a baseband component from the orthogonal data output by said second multiplier, and for outputting the second band-limited data.

5. An adjacent and alternate channels power measurement apparatus for measuring power present in a predetermined frequency band to have, as a central frequency, a frequency of at least one of adjacent and alternate channels assigned at predetermined frequency intervals from a carrier frequency upon reception of a burst signal in which ON and OFF durations of a modulated carrier repetitively appear at predetermined time intervals, said apparatus comprising:

a time sequence signal generator for generating a time sequence signal by sampling the burst signal;

a storage device for storing the time sequence signal generated by said time sequence signal generator;

a discrete Fourier transform (DFT) filter bank for receiving a signal read out from said storage device in a desired closed time period of the time sequence signal stored in said storage device, for calculating a discrete Fourier transform of the received signal so that bandpass filter processing of the read out signal is performed in correspondence with a plurality of desired frequencies while shifting a window function by a predetermined number of sample point units, and for outputting processing results in parallel for the plurality of desired frequencies;

an absolute value calculator for calculating absolute values of the processing results for each of a plurality of outputs from said DFT filter bank;

a peak value detector for detecting peak values of the absolute values in units of outputs from said absolute value calculator, and for outputting the peak values in correspondence with the plurality of desired frequencies; and

an arithmetic operator for calculating the power present in the predetermined frequency range to have, as the central frequency, the frequency of at least one of the adjacent and alternate channels in accordance with the outputs from said peak value detector;

wherein said time sequence signal generator comprises;

a local oscillator for oscillating a local signal having a predetermined frequency;

a phase shifter for shifting a phase of the local signal oscillated by said local oscillator through 90°

;

a first mixer for mixing the burst signal with the 90°

phase-shifted local signal shifted by said phase shifter, and for outputting a first intermediate frequency (IF) signal;

a first bandpass filter for limiting a frequency band of the first IF signal output by said first mixer;

a first analog/digital converter for sampling the first IF signal band-limited by said first bandpass filter, and for outputting a first time sequence signal;

a second mixer for mixing the burst signal with the local signal oscillated by said local oscillator, and for outputting a second IF signal which has an orthogonal relationship with respect to the first IF signal;

a second bandpass filter for limiting a frequency band of the second IF signal output by said second mixer; and

a second analog/digital converter for sampling the second IF signal band-limited by said second bandpass filter, and for outputting a second time sequence signal which has an orthogonal relationship with respect to the first time sequence signal.

6. An adjacent and alternate channels power measurement apparatus for measuring power present in a predetermined frequency band to have, as a central frequency, a frequency of at least one of adjacent and alternate channels assigned at predetermined frequency intervals from a carrier frequency upon reception of a burst signal in which ON and OFF durations of a modulated carrier repetitively appear at predetermined time intervals, said apparatus comprising:

a time sequence signal generator for generating a time sequence signal by sampling the burst signal;

a storage device for storing the time sequence signal generated by said time sequence signal generator;

a discrete Fourier transform (DFT) filter bank for receiving a signal read out from said storage device in a desired closed time period of the time sequence signal stored in said storage device, for calculating a discrete Fourier transform of the received signal so that bandpass filter processing of the read out signal is performed in correspondence with a plurality of desired frequencies while shifting a window function by a predetermined number of sample point units, and for outputting processing results in parallel for the plurality of desired frequencies;

an absolute value calculator for calculating absolute values of the processing results for each of a plurality of outputs from said DFT filter bank;

a peak value detector for detecting peak values of the absolute values in units of outputs from said absolute value calculator, and for outputting the peak values in correspondence with the plurality of desired frequencies; and

an arithmetic operator for calculating the power present in the predetermined frequency range to have, as the central frequency, the frequency of at least one of the adjacent and alternate channels in accordance with the outputs from said peak value detector;

wherein said time sequence signal generator comprises;

an analog/digital (A/D) converter for sampling the burst signal at a predetermined sampling timing, and for outputting a time sequence signal;

an orthogonal carrier sequence generation circuit for generating an orthogonal carrier sequence signal including real and imaginary components;

a first multiplier for multiplying the time sequence signal output by said A/D converter with the real component of the orthogonal carrier sequence generated by said orthogonal carrier sequence generation circuit, and for outputting in-phase data;

a first bandpass filter for performing a first band limitation for removing components other than a baseband component from the in-phase data output by said first multiplier, and for outputting the first band-limited data;

a second multiplier for multiplying the time sequence signal output by said A/D converter with the imaginary component of the orthogonal carrier sequence generated by said orthogonal carrier sequence generation circuit, and for outputting orthogonal data; and

a second bandpass filter for performing a second band limitation for removing components other than a baseband component from the orthogonal data output by said second multiplier, and for outputting the second band-limited data.

7. An occupancy bandwidth measurement apparatus for measuring an occupancy bandwidth based on power present in a predetermined frequency band to have, as a central frequency, a frequency of at least one of adjacent and alternate channels assigned at predetermined frequency intervals from a carrier frequency upon reception of a burst signal in which ON and OFF durations of a modulated carrier repetitively appear at predetermined time intervals, said apparatus comprising:

a time sequence signal generator for generating a time sequence signal by sampling the burst signal;

a storage device for storing the time sequence signal generated by said time sequence signal generator;

a discrete Fourier transform (DFT) filter bank for receiving a signal read out from said storage device in a desired closed time period of the time sequence signal stored in said storage device, for calculating a discrete Fourier transform of the received signal so that bandpass filter processing of the read out signal is performed in correspondence with a plurality of desired frequencies while shifting a window function by a predetermined number of sample point units, and for outputting processing results in parallel for the plurality of desired frequencies;

an absolute value calculator for calculating absolute values of the processing results for each of a plurality of outputs from said DFT filter bank;

a peak value detector for detecting peak values of the absolute values in units of outputs from said absolute value calculator, and for outputting the peak values in correspondence with the plurality of desired frequencies; and

an arithmetic operator for calculating the power present in the predetermined frequency range to have, as the central frequency, the frequency of at least one of the adjacent and alternate channels in accordance with the outputs from said peak value detector, and for calculating the occupancy bandwidth based on the calculated power;

wherein said time sequence signal generator comprises;

a local oscillator for oscillating a local signal having a predetermined frequency;

a phase shifter for shifting a phase of the local signal oscillated by said local oscillator through 90°

;

a first mixer for mixing the burst signal with the 90°

phase-shifted local signal shifted by said phase shifter, and for outputting a first intermediate frequency (IF) signal;

a first bandpass filter for limiting a frequency band of the first IF signal output by said first mixer;

a first analog/digital converter for sampling the first IF signal band-limited by said first bandpass filter, and for outputting a first time sequence signal;

a second mixer for mixing the burst signal with the local signal oscillated by said local oscillator, and for outputting a second IF signal which has an orthogonal relationship with respect to the first IF signal;

a second bandpass filter for limiting a frequency band of the second IF signal output by said second mixer; and

a second analog/digital converter for sampling the second IF signal band-limited by said second bandpass filter, and for outputting a second time sequence signal which has an orthogonal relationship with respect to the first time sequence signal.

8. An occupancy bandwidth measurement apparatus for measuring an occupancy bandwidth based on power present in a predetermined frequency band to have, as a central frequency, a frequency of at least one of adjacent and alternate channels assigned at predetermined frequency intervals from a carrier frequency upon reception of a burst signal in which ON and OFF durations of a modulated carrier repetitively appear at predetermined time intervals, said apparatus comprising:

a time sequence signal generator for generating a time sequence signal by sampling the burst signal;

a storage device for storing the time sequence signal generated by said time sequence signal generator;

a discrete Fourier transform (DFT) filter bank for receiving a signal read out from said storage device in a desired closed time period of the time sequence signal stored in said storage device, for calculating a discrete Fourier transform of the received signal so that bandpass filter processing of the read out signal is performed in correspondence with a plurality of desired frequencies while shifting a window function by a predetermined number of sample point units, and for outputting processing results in parallel for the plurality of desired frequencies;

an absolute value calculator for calculating absolute values of the processing results for each of a plurality of outputs from said DFT filter bank;

a peak value detector for detecting peak values of the absolute values in units of outputs from said absolute value calculator, and for outputting the peak values in correspondence with the plurality of desired frequencies; and

an arithmetic operator for calculating the power present in the predetermined frequency range to have, as the central frequency, the frequency of at least one of the adjacent and alternate channels in accordance with the outputs from said peak value detector, and for calculating the occupancy bandwidth based on the calculated power;

wherein said time sequence signal generator comprises;

an analog/digital (A/D) converter for sampling the burst signal at a predetermined sampling timing, and for outputting a time sequence signal;

an orthogonal carrier sequence generation circuit for generating an orthogonal carrier sequence signal including real and imaginary components;

a first multiplier for multiplying the time sequence signal output by said A/D converter with the real component of the orthogonal carrier sequence generated by said orthogonal carrier sequence generation circuit, and for outputting in-phase data;

a first bandpass filter for performing a first band limitation for removing components other than a baseband component from the in-phase data output by said first multiplier, and for outputting the first band-limited data;

a second multiplier for multiplying the time sequence signal output by said A/D converter with the imaginary component of the orthogonal carrier sequence generated by said orthogonal carrier sequence generation circuit, and for outputting orthogonal data; and

a second bandpass filter for performing a second band limitation for removing components other than a baseband component from the orthogonal data output by said second multiplier, and for outputting the second band-limited data.