Design and performance of an ultra-low phase noise, radar exciter

This paper reports on the design and performance of a radar exciter exhibiting state-of-the-art phase noise characteristics. The exciter provides fully coherent receiver local oscillator signals at HF, L-band, and X-band as well as requisite, auxiliary VHF and HF clock signals. Output signal spectral performance was achieved via use of a variety of recently-developed circuit technologies and frequency synthesis techniques. Included in these are use of multiple quartz crystals in the master oscillator, cascaded stages of narrowband, UHF SAW resonator filters, regenerative frequency division, and low noise, diode doubler and step recovery diode frequency multiplication. For the X-band outputs, the measured phase noise performance is given. Exciter output signal spectral performance in the presence of modest levels of mechanical vibration is also presented. Included in the vibration data are results of SAW resonator vibration sensitivity measurements for several different SAWR die designs. The data indicates large variations in SAWR vibration sensitivity values as well as spectral peaking in the fm=7 KHz carrier offset frequency region that is associated with SAWR mechanical mount resonances excited by environmental (sound level) stress and can be suppressed via acoustic shielding