Burst signal spectrum measuring system with stepwise sweeping

A spectrum analyzing apparatus comprising:

• receiving means including:
• for receiving a burst signal to be measured, said burst signal having a plurality of burst-on intervals,
• means for converting the burst signal into an intermediate frequency signal in accordance with a local oscillation signal having a predetermined swept frequency locked with a single frequency during each burst-on interval of the burst signal and differing among different burst-on intervals, and
• means for detecting the intermediate frequency signal, so as to output a signal representing a spectrum of the burst signal;
• frequency setting means for setting frequency information for determining a plurality of measuring frequencies from a first measuring frequency to an nth (where n is a natural number) measuring frequency;
• measuring time determining means for determining measurement start and end times in association with the burst signal and for outputting measurement start and end signals corresponding to the measurement start and end times;
• frequency control means for determining a desired number of measuring frequencies from an ith (where 1.ltoreq.i<n) measuring frequency to a kth (where i<k.ltoreq.n) measuring frequency in accordance with the frequency information set by sa said frequency setting means, and for stepwise-setting the predetermined swept frequency of the local oscillation signal in said receiving means at timings in accordance with an initialization signal and the measurement end signal from said measuring time determining means so as to sequentially output spectrum signals respectively corresponding to the desired number of measuring frequencies from the ith to kth measuring frequencies from said receiving means and such that the predetermined swept frequency is locked with a single frequency during each burst-on interval of the burst signal and differs among different burst-on intervals;
• level detecting means for dating on output signal from said receiving means between reception timings of the measurement start and end signals from said measuring time determining means, and sequentially detecting levels of the ith to kth measuring frequency components included in the burst signal as spectrum data in accordance with the gated output signal;
• waveform memory means for storing the spectrum data sequentially detected by said level detecting means at an address corresponding to the predetermined swept frequency set by said frequency control means;
• and
• display means for developing and displaying the spectrum data representing the ith to kth measuring frequency component levels stored in said waveform memory means on a frequency axis corresponding to the address.