SIGNAL ELECTRIC LABS is pleased to announce a complete suite of seven independent study modules that captures the classical concepts of digital modulation and demodulation theory in the presence of additive noise. The result allows the student to study the performance of each modulation type as a function of the signal-to-noise ratio and display the Bit Error Ratio (BER). The measured BER can then be compared to what theory predicts. Each module has been designed according to theory and they perform as theory predicts. Click on the red "OUR PRODUCTS" button to view our products.

Each module is complete with a comprehensive Technical Manual that explains everything you need to know. After using our independent-study platforms along with our Technical Manuals and your instructor, the student will learn more than you'll ever get out of many engineering labs. These modules can also be used along with textbook theory to enhance the student's understanding of digital communication systems, modulation and demodulation types, additive noise and bit errors. The use of high-quality components and design architecture ensures repeatable, accurate performance.

The student will learn about, using real, hands-on hardware, modulation, signal constellations, coherent and non-coherent demodulation, noise processes (wideband and bandpass-filtered), bit decisions and errors, integrate & dump circuits, phase lock loop frequency synthesizers, closed-loop transfer functions, data filtering, pseudorandom code generators, CVSD and 8-bit PCM digital voice encoding and decoding, actual BER measurements, Costas loops, squaring loops, phase detectors, acquisition circuits, analog and digital circuit design, heat sink design and much more.

These modules are a compliment to all colleges and universities that offer communication theory along with laboratory hands-on practice in the Art. These modules are intended for use by Juniors and Seniors in Electrical Engineering laboratories but they can also be used as independent-study platforms for current, practicing engineers to enhance their understanding of the Concepts.

The heart of our products start with the modulation process. Our Type MOD-1 Signal Modulator generates ASK, FSK, BPSK, DPSK, QPSK, Offset-QPSK (OQPSK) and 8QAM with selectable data rates and adjustable I and Q carrier levels. The BPSK signaling phase separation is adjustable from 0 to 180-degrees (antipodal). A 20-stage pseudorandom code generator, 8-bit PCM and CVSD audio CODECs form the data sources and an audio loopback feature is included to test recovered audio quality under various BER conditions. CODEC audio sources can be external, or you can use the on-board microphone or a stored audio clip of your choice using the on-board Chipcorder. Our 195-page Technical Manual for this product will teach you more than you'll learn in any one classroom on the subject. From modulation theory, phase lock loops, closed-loop feedback systems, signal constellations, audio encoding/decoding and much more.

The output of the Type MOD-1 Signal Modulator is combined with additive noise from the Type NS-1 Noise Source. The Type NS-1 Noise Source has a flat noise power spectrum to approximately 20MHz (which is much wider than any of the modulation bandwidths used in our products) with a total noise power of up to +15dBm. The Noise Source comes with pre-calibrated noise power settings that takes the guesswork out of where you are with noise power and comes with an accurate noise power step attenuator with a range from 0 ~ 31-dB in 1-dB steps. The output noise power level is held constant by a servo feedback control loop and the output noise power is made continuously variable or in steps. Once the desired maximum noise power output is set, the step attenuator takes over to precisely control the noise power in 1-dB steps.

The modulated signal plus additive noise is demodulated by a classical textbook implementation of a non-coherent bandpass envelope detector, a matched-filter integrate & dump coherent detector and a Costas/squaring loop represented by the Types NCD-1, CD-1 and COS-1 series of demodulators available from Signal Electric Labs. All demodulators are designed to interface with the Type BER-1 Bit Error Ratio (BER) measurement system and the Type MOD-1 Signal Modulator to utilize the audio loopback features. Every demodulator is equipped with an on-board RMS power detector which allows the student to accurately set both the signal and noise power for accurate and repeatable BER measurements.

Finally, as the ultimate test of the figure-of-merit of any modulation method, is the measure of the BER as a function of the demodulator SNR. The Type BER-1 Bit Error Ratio (BER) system interfaces easily with all of our demodulator products using a single CAT-6 cable (supplied). The BER is displayed as one varies the demodulation SNR by varying the noise power attenuators on the Type NS-1 Noise Source. A Test Point is supplied which provides a DC voltage relative to the BER. This is useful when adjusting for optimal data decision thresholds and Costas loop I/Q Arm bandwidths.