Direct conversion receiver employing subharmonic frequency translator architecture and related preprocessor

Abstract

A direct conversion receiver for receiving a first input signal and directly downconverting it to baseband frequencies. The receiver includes a frequency translator which is responsive to a phase-split input signal having 2n components, wherein n is an integer greater than 1. The phase-split signal has a period T which is about n times the period of the first input. The frequency translator alternates, at a rate of about 2n / T, between switching the first input signal to a first output, and switching the first signal to a second output. A preprocessor is available to improve the switching characteristics of the phase-split input signal.

Description

1. Background of the invention [0001] The present invention relates to direct conversion receivers, and more particularly to subharmonic frequency converters for use in such receivers, and preconditioners for improving the switching characteristics of the LO input of such frequency converters. 2. Background technology [0002] Existing techniques typically down-convert a radio frequency signal (RF) to baseband frequency in two steps. In the first step, the signal is down-converted to an intermediate frequency (IF), and then in the second step the signal is down-converted to a baseband signal. Figure 1 shows an existing receiver with a carrier frequency F RF The RF signal 1 is input to the RF port 3 of the mixer 2, and a local oscillator (LO) 9 generated by the frequency F X Less than or equal to F RF The signal 10 is passed through a bandpass filter 15 and then through a low noise amplifier (LNA) (not shown). The resulting signal is then provided to the LO input port 4 of...

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Problems solved by technology

Second, half-switched transistors introduce noise on the output, because in a Gibb mixer configuration, a half-switched transistor would cause a significant resistance drop at the emitter of the opposing transistor pair, which would Increased shot noise generated by transistors

[0013] Another undesired property of this signal is that the transition points are sensitive to variations in the amplitude of each local oscillator output signal, so the switching action of all the mixers driven by it is difficult to precisely control of

[0014] Another problem with this signal is that these signals are usually not sinusoidal due to factors such as current local oscillator limitations, but in fact are usually flat at maximum and minimum values, resulting in softer transitions, becomes less desirable for driving a mixer

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