 nature. Rx DC offset: The zero-IF demodulator multiplies the RF signal with a local oscillator (LO) frequency. Due to unintended coupling (capacitive coupling on the printed circuit board, radiated coupling between antennas, and so on) between the LO signal and other components (say, the receiver antenna), some of the LO signals is unintentionally received at the input of the demodulator. After multiplication with the intended LO frequency (so a multiplication of two signals of the same frequency), this signal comes out as a DC offset that can reduce the dynamic range of the system. Tx LO leakage correction: Like Rx DC offset, transmit LO leakage means that the LO signal unintentionally makes its way to the RF transmit antenna and hence causes an unwanted transmission, potentially breaking RF transmitter specifications. Compensation for LO leakage can be done by generating a compensating signal in the baseband that is opposite to the LO leakage, thus canceling out the leakage. Chapter 10 Interoperability and test 337 Tx gain/phase error: As the transmitted signal passes through the digital-to-analog conversion and associated analog components before it is modulated to the RF frequency, gain and phase between I and Q signals will no longer be perfect as they were generated in the digital domain. The errors caused by this can show up as EVM errors in the transmitted signal, causing for higher bit error rates at the receiver. Tx droop correction: During transmission, power amplifiers exhibit thermal effects which, specifically, in long RF pulses with low duty cycle can impact the PA gain/phase behavior. Tools needed These measurements are executed on a test bench such as shown in Fig. 10-4 for transmit- ter testing: or in Fig. 10-5 for receiver testing: Typical test tools include: RF spectrum analyzer and or 5G signal analyzer 5G/RF signal generator(s) DC Power Measure Emulator 500 W Power attenuator Spectrum Power Analyzer Meter FIGURE 10-4 Transmitter RF testing. 5G Signal Emulator Generator Attenuator FIGURE 10-