| 摘要 |
In radio transmitting equipment that develops a carrier frequency using a mixer, techniques are used to "shift" or "hide" spurious mixer outputs so that they do not significantly degrade spectral purity of the transmitter output. These techniques generally involve establishing a predetermined frequency relationship between the two signals inputted to the transmitter mixer (TXIF (VCO) and TXLO) in addition to the relationship required to provide the desired difference frequency when the two signals are mixed in the mixer. By establishing a certain predetermined frequency relationship between these two signals it is possible to precisely locate the frequencies of the undesirable mixer output products so that they can be filtered out and/or fall onto the desired output frequency. While generally applicable, these techniques provide special advantages in equipment in which other considerations constrain the design of the transmitter circuitry and frequency inputs thereto.
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