INTERMEDIATE FREQUENCY (IF) SIGNAL BETWEEN 6 AND 7 MHZ IS ALIASED BETWEEN DC AND 1MHz BY SAMPLING AT 2MSPS BASEBAND fs=2MSPS SIGNAL de To Figure 5.7 A popular application of undersampling is in digital receivers. A simplified block diagram of a traditional digital receiver using baseband sampling is shown in Figure 5.8. The mixer in the rf section of the receiver mixes the signal from the antenna with the RF frequency of the local oscillator. The desired information is contained in relatively small bandwidth of frequencies Delta f In actual receivers, Delta f may be as high as a few megahertz. The local oscillator frequency is chosen such that the Delta f band is centered about the IF frequency at the bandpass filter output. Popular IF frequencies are generally between 10 and 100MHz. The detector then translates the Delta f frequency band down to baseband where it is filtered and processing, but the simple diagram serves to illustrate the concept, s processed by a baseband ADC. Actual receivers can have several stages of rf and IF SIMPLIGIED DIGITAL RECEIVER USING BASEBAND SAMPLING FSECTON FFSECnON D>③ LOWPASS 花TE网 Figure 5.8 In a receiver which uses direct IF-to-digital techniques(often called undersampling harmonic, bandpass, or IF sampling), the If signal is applied directly to a wide bandwidth ADC as shown in Figure 5.9. The ADC sampling rate is chosen to be at least 2 Delta f. The process of sampling the if frequency at the proper rate cause one of the aliased components of Delta f to appear in the de to f/2 Nyquist8 INTERMEDIATE FREQUENCY (IF) SIGNAL BETWEEN 6 AND 7 MHz IS ALIASED BETWEEN DC AND 1MHz BY SAMPLING AT 2MSPS Figure 5.7 A popular application of undersampling is in digital receivers. A simplified block diagram of a traditional digital receiver using baseband sampling is shown in Figure 5.8. The mixer in the RF section of the receiver mixes the signal from the antenna with the RF frequency of the local oscillator. The desired information is contained in relatively small bandwidth of frequencies Delta f. In actual receivers, Delta f may be as high as a few megahertz. The local oscillator frequency is chosen such that the Delta f band is centered about the IF frequency at the bandpass filter output. Popular IF frequencies are generally between 10 and 100MHz. The detector then translates the Delta f frequency band down to baseband where it is filtered and processed by a baseband ADC. Actual receivers can have several stages of RF and IF processing, but the simple diagram serves to illustrate the concepts. SIMPLIGIED DIGITAL RECEIVER USING BASEBAND SAMPLING Figure 5.8 In a receiver which uses direct IF-to-digital techniques (often called undersampling, harmonic, bandpass, or IF sampling), the IF signal is applied directly to a wide bandwidth ADC as shown in Figure 5.9. The ADC sampling rate is chosen to be at least 2 Delta f. The process of sampling the IF frequency at the proper rate causes one of the aliased components of Delta f to appear in the dc to fs /2 Nyquist