HANDHELD VECTOR NETWORK ANALYZER (VNA) OPERATING AT A HIGH FREQUENCY BY MIXING LO AND RF SIGNALS HAVING OFFSET ODD HARMONICS

摘要

A vector network analyzer (VNA) has a first harmonic generator multiplying an RF signal by an odd number M1 to produce incident and reflected test signals received at inputs of mixers providing IF signals. A second harmonic generator multiplies an LO signal by an odd number M2 offset by 2 from M1 to provide signals to additional inputs of the mixers providing IF signals. With the harmonic generators providing odd harmonics separated by 2, a single filter removes remaining harmonics from IF signals provided from each mixer. Each harmonic generator includes two step recovery diodes (SRDs) with opposing ends connecting the signal path to ground, the SRDs functioning to cancel even harmonics. A first coupler provides the output of the first harmonic generator to the mixers, the first coupler having a minimal size enabling its output power to increase with frequency. With the first harmonic generator having power decreasing with frequency and the first coupler having power increasing with frequency, the VNA test signal will have a substantially flat power vs. frequency response. Additional couplers having a minimal size provide the incident and reflected test signals to the mixers. With the second harmonic generator providing an LO signal with power decreasing with frequency to the mixers, and the additional couplers providing power increasing with frequency, the IF signals from the mixers will also have a flat power vs. frequency response.