Electrical circuit for filtering a local oscillator signal and harmonic rejection mixer

Abstract

An electrical circuit (10) is provided. The electrical circuit can have an input terminal (12) to receive an input signal and an output terminal (20) at which an output signal can be provided. The electrical circuit further comprises, a local oscillator (14), a first mixer (16), a second mixer (18), and a delay element (22). In the electrical circuit the first mixer is configured to receive an input signal from the input terminal and to mix the input signal with a local oscillator signal. Also, the second mixer is configured to receive said input signal from the input terminal and to mix the input signal with a delayed local oscillator signal, where the delayed local oscillator signal is said local oscillator signal fed via the delay element to the second mixer. The electrical circuit is configured to combine the output signal from the first mixer with the output signal from the second mixer to form an output signal at the output terminal. Hereby, an electrical circuit is provided thatcan efficiently handle the non-idealities of a local oscillator, LO, signal in receivers or transmitters. This is achieved by the electrical circuit that uses a form of finite impulse response, FIR,filter mixer. For example, in receivers, the electrical circuit can be used to filter harmonic components of a pulse-shaped LO signal, resulting in attenuation of the unwanted harmonic down-conversionproducts. The electrical circuit can also be used in other applications, such as but not limited to, filtering of the quantization noise or spurious tones of a digitally generated LO signal.

Description

technical field [0001] The invention relates to a circuit for filtering local oscillator signals. The invention also relates to a finite unit impulse response (FIR) filter and a receiver using said circuit or FIR filter. Background technique [0002] In the modulation / demodulation of signals, it is often necessary to reduce out-of-band noise or unwanted tones. A typical source of out-of-band noise is the use of quantized signals in frequency mixing, where tone is the result of non-ideal mixing waveforms that generate additional mixing products. There are many techniques that can be used to reduce these unwanted effects. [0003] For example, EP2328273 describes a radio frequency (radio frequency, RF) modulator for modifying the quantization noise generated by an interpolator of the RF modulator, thereby reducing the quantization noise at a predetermined frequency. [0004] In applications described in EP2328273 et al., harmonic components resulting from the use of a pulse...

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Problems solved by technology

[0005] The inventors found several problems with existing solutions

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