Broadband frequency agile signal characterization
A signal analyzer to characterize the RF signal transmitted by a frequency hopping radio transmitter. The transmitted signal is analyzed while hopping across a broad frequency band without knowledge of the hop frequencies, timing or signal bandwidth. A wide range of signal parameters are measured on the dehopped signal to characterize the radio performance and the compliance to the radio specifications.
1. A method of broadband radio frequency analysis comprising the steps of:
receiving a frequency hopping radio input signal for broadband analysis, said input signal having segments at different hopping frequencies and different hopping times,
for each segment,
determining from the input signal a hopping time of the segment,
processing the segment to determine a frequency of the segment, and
processing the segment to determine signal parameters,
where the signal processing includes signal demodulation to form a demodulated signal and where the signal processing includes measuring a symbol rate where the symbol rate is calculated by analysis of zero crossing times in the demodulated signal,
where time differences between zero crossings is calculated from zero crossing times,
where a TOT histogram is compiled of the time differences as delta TOTs,
where a symbol period estimate of a symbol period is formed from a center of mass of a first major peak in the TOT histogram,
where the symbol period is calculated by,
computing the modulo of the delta TOTs and the symbol period estimate,
unwrapping the modulo results about the symbol period estimate,
fitting a straight line to the unwrapped data,
using a slope of the straight line to refine the symbol period estimate thereby producing a final value for the symbol period.
2. The method of claim 1 where the straight line fit uses a least squares fit.