| 摘要 |
A DME receiver is arranged to produce, at baseband, a linear replica of an RF input, over relatively wide dynamic range. The DME receiver receives a local oscillator signal from the associated transmitter which is mixed (in a first mixer) with the RF input to produce an IF signal which is a replica of the RF input. The receiver includes an IF amplifier and a bandpass filter serially coupled to the output of the first mixer. Coupled to the output of the bandpass filter is a signal processing circuit with two outputs. The signal processing circuit produces at one output a replica of its input, and at another output a phase shifted and limited replica of its input. Both outputs are coupled to a second mixer. The second mixer has two inputs and an output. By appropriately adjusting the phase of the signal in the signal processing circuit, the phase of that signal (at one input to the second mixer) and of the other signal input to the second mixer are made equal, and as a result, the output of the second mixer is a signal, at baseband, which is a linear replica of the RF input. In one embodiment of the invention, the inputs to the second mixer are at IF and in another embodiment of the invention, the inputs to the second mixer are at a second intermediate frequency, lower than the first intermediate frequency.
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