|}
In this part of the tutorial lesson, you will build and test an FMCW system with a QAM demodulator circuitsawtooth chirp modulation. To test your demodulator circuit[[RF.Spice A/D]] provides three types of chirp generator devices. All three are based on sawtooth modulation but each provides a different output waveform. They are sinusoidal chirp generator, triangular wave chirp generator and square wave chirp generator. For this project, you will initially use an AM-modulated voltage source for the input signal. This source is accessible first type, which can be access from '''Menu > Parts > Waveform Generation Blocks > Modulated Waveforms Chirp Generators > Single-Tone AM Modulated SourceSine Wave Chirp Generator'''. It represents a sinusoidal baseband signal of frequency f<sub>Set the '''Chirp Period''' to 100μs</sub> modulated on (i.e. a carrier frequency 10kHz chirp), and set the values of f<sub>c</sub>the two [[parameters]] '''freq_low''' and '''freq_high''' to 1GHz and 1. The AM waveform can be expressed as: 01GHz, respectively.
<math> y(t) = A_c \left( 1 + m x(t) \right) cos(2\pi f_c t) = A_c \left( 1 + m A_s cos(2\pi f_s t) \right) cos(2\pi f_c t) </math>
where f<sub>c</sub> and f<sub>s</sub> are the carrier and signal frequencies, respectively, and m (the MDI parameter) is the modulation index or depth. m = 0 means no modulation, and m = 1 represent full modulation. You are going to feed an AM modulated signal with a signal frequency of 300MHz, a carrier frequency of 3GHz, a carrier amplitude of 15V and a modulation index of m = 1. Â {{Note|Most RF devices in [[RF.Spice A/D]] have a center frequency fc parameter that must be specified in GHz. On the other hand, the frequency of analog sources and most virtual blocks has to be specified in Hz.}} Â <table><tr><td>[[File:SysTUT7 14.png|thumb|550px|The property dialog of the AM-Modulated Source.]]</td></tr></table>Â Place and connect all the parts as shown in the figure below. For the receiver circuit, instead of a Wilkinson power divider, you will use a simpler resistive power divider. Set the lengths of the input and output feed lines to a minimum: len_in = len_out = 2mm. For this part, you will use the "Limiter Block" simply as an amplifier with a gain of 5. For the peak detector block of the receiver circuit, you will use a full-wave bridge rectifier together with a simple RC filter. The analog binary output of this circuit fluctuates between low and high voltage levels. Finally, the '''Ideal Comparator Block''' compares the output of the peak detector circuit to a fixed DC voltage of +4V. Set the gain of the comparator to 10. This may also serve as an IF or baseband amplifier. The output of the comparator is converted to a digital output using s ADC bridge.
<table>