| 摘要 |
A mixing circuit uses spread spectrum techniques to discriminate between desired signals and image responses associated with frequency translation, signal mixing and the like. In a receiver, the radio frequency (R.F.) signal is mixed with a first spread spectrum local oscillator (L.O.) producing a spread spectrum intermediate frequency (I.F.) signal. The spread spectrum (I.F.) is filtered and mixed with a second spread spectrum (L.O.) which de-spreads the desired signal in the (I.F.). The second (L.O.) is driven with the same spreading function as the first (L.O.) therefore the desired signal is correctly de-spread while the spurious signals are not. The circuit is equally useful in both receivers and transmitters. In general, the circuit is useful in any system where two or more signals are multiplied and it is desired to reject spurious signals. |
