Meaning
Radio receiver design requires the ability to process weak signals of interest in the presence of strong interfering transmitters. The parameter known as receiver linearity measures how well the radio front-end maintains a proportional relationship between input power and output power. High linearity ensures that the incoming signal is not distorted by the internal mixing and amplification stages.
It prevents the generation of unwanted spurious frequencies within the receiver circuitry.
Signal Interpretation
Demodulation algorithms rely on a clean representation of the incoming waveform to extract data without errors. When receiver linearity degrades, the signal constellation points deform, which increases the bit error rate of the system. The receiver loses its ability to distinguish between adjacent symbols, especially in high-order modulation schemes.
This degradation can lead to a drop in data throughput or a lost connection.
Hardware Constraint
Analog components such as low-noise amplifiers and mixers have physical limits governed by their supply voltages and bias currents. In a system with poor receiver linearity, strong out-of-band signals can push these components into saturation, causing gain compression. This compression suppresses the weak signal of interest, making it impossible to detect even if the signal is otherwise above the noise floor.
Engineers must choose components with high third-order intercept points to prevent this desensitization in congested environments. The choice of component must also balance the increased power consumption required to achieve higher linearity.
Intermodulation Assessment
Laboratory testing of radio receivers utilizes multi-tone signal generators to measure the generation of unwanted intermodulation products. To evaluate receiver linearity, two closely spaced out-of-band test tones are injected into the antenna port of the device. The receiver is then monitored to detect if the resulting third-order products fall into the active channel of the receiver.
This test determines the ultimate interference immunity of the integrated radio system.
