A software-defined radio receiver architecture robust to out-of-band interference

Abstract

In a software-defined radio (SDR) receiver it is desirable to minimize RF bandfiltering for flexibility, size and cost reasons, but this leads to increased outof-band interference (OBI). Besides harmonic and intermodulation distortion (HD/IMD), OBI can also lead to blocking and harmonic mixing. A wideband LNA [1, 2] amplifies signal and interference with equal gain. Even a low gain of 6dB can clip 0dBm OBI to a 1.2V supply, blocking the receiver. Hard-switching mixers not only translate the wanted signal to baseband but also the interference around LO harmonics. Harmonic rejection (HR) mixers have been used [3,1,4], but are sensitive to phase and gain mismatch. Indeed the HR in [4] shows a large spread, whereas other work only shows results from one chip [3,1]. This paper describes techniques to relax blocking and HD/IMD, and make HR robust to mismatch.

A High Gain and High Harmonic Rejection LNA Using High Q Series Resonance Technique for SDR Receiver

“…Consequently, a software-defined radio (SDR) receiver is needed to reduce complexity and costs [1]. An SDR receiver can accomplish this, but it can also suffer from outof-band interferences because it deals with wideband signals at the RF front-end [2].…”

RF signal generator using time domain harmonic suppression technique in 90nm CMOS

“…To reduce the circuit scale and the power consumption, a digitally controllable RF circuit technique is demonstrated [3]. In addition, a harmonic suppression using the multi voltage step signal generation has been proposed [4,5]. And we also suggested the time-to-analog conversion (TAC) technique for RF signal generation using the time domain resolution instead of the voltage domain resolution [6].…”

Wide-band, high linear low noise amplifier design in 0.18um CMOS technology

“…But the required linearity that should be fulfilled in order to avoid the down conversion of the out of band IM3 products that may overlap on the wanted signal [2,4,5] forms a technical challenge in its realization. Using multi center-frequency SAW filter between the output of LNA and the input of mixer to suppress the out of band IM3 products that are produced by the LNA seems to be a non-practical solution since the SAW filter is a bulky, expensive and off chip, even in narrow-band applications avoiding SAW filter is of a big interest [4].On the another hand enhancing the linearity performance of the RF front-end by means of modifying the system itself can be achieved on the cost of complexity, power and area [4,5]. So a compromised design is required in which the realization of wide-band, high linear LNA with low NF is essential to relax the needed system modifications to avoid the usage of SAW filter in order to achieve the required wide-band RF front-end linearity.…”