Software defined radio receivers exploiting noise cancelling: A tutorial review

Traditional radio receivers were narrowband and dedicated to a single frequency band exploiting LC tanks, whereas software defined radios target a flexibly programmable frequency. The broadband noise cancelling circuit technique has proven useful to achieve this target, as it breaks the traditional trade-off between low noise and broadband impedance matching. Different variants exist, with noise cancellation in the voltage or current domain, either at RF or after frequency translation to baseband. This article reviews the development of the noise cancelling technique and its role in inductorless interference robust software defined radio receivers.