| 摘要 |
<p>An offset frequency converter (10) for the intermediate frequency (IF) stages of a multi-channel radio frequency (RF) phase/amplitude measurement receiver (8). The converter allows use of noncoherent transmitter and receiver local oscillator sources which utilize digital frequency synthesizers and enables harmonic mixing to be employed. The converter samples an incoming first intermediate frequency signal IF1 in a reference channel (38b). The IF1 sample is then upconverted to a higher frequency, filtered and downconverted to an IF1+IF2 signal offset from the IF1 sample by a lower second intermediate frequency IF2. The added frequency offset IF2 is derived from a time stabilized source independent of the transmitter but coherent with the receiver LO. The mixed IF1+IF2 signal is heterodyned with signals in both the signal channel (38a) from the antenna under test and the reference channel to obtain coherent outputs at IF2 which differ by phase and magnitude corresponding to the characteristics of the antenna under test.</p> |
