<p>Recent advancements in novel radio frequency (RF) microwave phase measurement techniques have generated significant interest. Accurate phase measurement is essential for optimal performance in various applications, including telecommunications, radars, phased array antennas, phase modulators, and GPS receivers. High-precision phase measurement methods are crucial for monitoring subtle phase shift variations accurately. This paper analyzes recent research on microwave relative phase measurement techniques based on homodyne and heterodyne detection principles and the associated challenges related to uncertainty, as utilized by national metrology institutes (NMIs). Under the homodyne principle, the National Institute of Standards and Technology (NIST) measured a single phase based on a bridge circuit at 100° with a phase accuracy of 0.5° at a frequency of 4&#xa0;GHz. This principle is extended by the National Laboratory for Infrared Physics in Japan to measure phase in the range of 0° to 180° in the X-band with a phase accuracy of 2°. Under the heterodyne principle, NIST also implemented phase measurements using a dual-channel phase-shift measurement system from 0° to 360° with an expanded uncertainty of 0.041º at 17&#xa0;GHz. Several developments in this principle were introduced to address errors and complexity. In addition, a new innovative phase detection methodology based on power measurements was developed by the National Institute of Standards (NIS) in Egypt. This technique offers precise measurements of relative phase shifts in the range from 0° to 180° with a maximum phase variation of ± 3.5°, covering S and C bands. This review aims to contribute to advancing microwave relative phase measurement techniques and provide insights into alternative methods for improvement.</p>