For the local oscillator (LO) amplification at the mixer end, low phase noise (LPN) amplifiers are preferred over low noise amplifiers (LNAs).

Mixers achieve frequency conversion through the nonlinear mixing of LO and radio frequency (RF) signals. During this process, the phase noise of the LO is directly transferred to the output signal, and its impact on performance is far greater than that of the amplitude noise which LNAs primarily suppress:

If the LO has poor phase noise, the output signal spectrum will exhibit spurious expansion, leading to increased adjacent channel interference (e.g., degraded adjacent channel leakage ratio) or reduced frequency resolution (e.g., difficulty for a spectrum analyzer to distinguish weak signals).

If the LO has slightly higher amplitude noise, as long as it does not exceed the linear dynamic range of the mixer, its impact on key indicators is minimal and can be further suppressed by subsequent intermediate frequency (IF) filtering.

The core requirement for LO amplification is to ensure phase purity, and LPN amplifiers are well-suited to this need. Misusing LNAs will degrade the phase noise of the output, impairing system performance (e.g., channel isolation, frequency resolution).

Our company offers a range of high-performance LPN amplifiers (such as the BR9192TA, BR9191TA, and BR9108TA), which feature an additional phase noise as low as -165 dBc/Hz at a 10 kHz offset. These amplifiers are ideal for LO signal amplification in frequency conversion systems.