RF Spectrum Analyzer Dong-Yo Jheng 2012/07/12

RF (Radio Frequency) Frequency: 3 kHz ~ 300 GHz 2

Spectrum Analyzer Block Diagram 3

Mixer RF: Radio Frequency LO: local Oscillator IF: Intermediate Frequency 4 Wanted:f LO - f in Image: f LO + f in Higher order: f LO ±2f in, f LO ±3f in

Sweep Operation 5

Intermediate Frequency Filter 6

Dynamic Range and Noise  Displayed Noise Level -Thermal noise inside circuit dBm/Hz at RT  Noise Sideband: -Phase noise of LO -Unit: dBc/Hz  Methods to reduce noise -Reduce RBW -Reduce input attenuation -Reduce VBW 7

Digital Spectrum Analyzer  All-digital IF stage  Swept mode -Digital filter(Better selectivity)  FFT mode -Faster swept in narrow span -Preserves phase information  Modern SAs combine both modes 8

State of the Art 9 Agilent N9030A-550Tektronix RSA6120B Frequency Range3 Hz ~ 50 GHz9 Hz ~ 20 GHz RBW1 Hz ~ 3 MHz0.1 Hz ~ 10 MHz Selectivity4.1:1 DANL at 2 GHz-152 dBm/Hz-151 dBm/Hz Phase nosie (10 1 GHz center frequency) -129 dBc/Hz- 106 dBc/Hz Acquisition BW140 MHz110 MHz ADC rate400 MS/s300 MS/s

References  Agilent Application Note: Spectrum Analysis Basics ( EN)  Agilent Application Note: Performance Spectrum Analyzer Series - Swept and FFT Analysis ( EN) 10