Meaning
Continuous frequency scanning operations measure signal amplitude across a defined band of the radio frequency spectrum. A standard spectrum analyzer sweep allows technicians to detect spurious emissions, measure channel power, and verify the performance of filter networks. The process involves tuning a local oscillator across the selected span while measuring the power levels at the intermediate frequency filter.
Sweep Parameter
Sweep time depends on the resolution bandwidth, the video bandwidth, and the frequency span selected by the operator. A narrow resolution bandwidth requires a slower sweep to allow the internal filter to respond fully to the incoming signal power. Sweeping too quickly causes a loss of amplitude accuracy and shifts the displayed frequency of the measured signals.
Signal Capture
Transient signals and fast frequency hoppers are easily missed by a standard sweep because the analyzer can only measure one frequency point at any single moment. Real time spectrum analyzers address this limitation by using fast Fourier transforms to capture the entire span simultaneously. For continuous wave signals, however, the traditional sweeping method offers a very wide dynamic range and excellent sensitivity at a lower cost.
Implementing a trace hold function allows the operator to capture intermittent signals over multiple sweeps, which helps to isolate sources of sporadic electromagnetic interference.
Production Test
Automated test systems execute a fast sweep to check that transmitter harmonics are within the limits set by regulatory standards. The sweep is triggered by a synchronization pulse from the device under test to ensure the transmitter is active during the measurement. The captured sweep data is then compared to a digital limit mask to determine if the device passes the production test.
