Understanding Single-Sideband (SSB)

Introduction

Single-sideband (SSB): A special type of amplitude modulation.
Purpose: Provide a technical introduction to SSB modulation, its usage, and primary variants in RF communication systems.

AM Signals: Created using a mixer combining an unmodulated RF carrier and a low-frequency modulating signal.
Result: A modulated RF carrier whose envelope mirrors the modulating signal.
Frequency Domain: AM signal information is in sidebands (above and below the carrier frequency).
Example: 1000 Hz sine wave modulation creates tones 1000 Hz above and below the carrier.
Human Speech Modulation: Creates broad non-uniform spectral content, doubling the width of the highest modulating frequency.

Definition: A type of AM where the carrier and one sideband is suppressed.
Information Content: Identical in both upper and lower sidebands, so suppressing one doesn't lose information.
Types of SSB:
- Upper Sideband (USB): Suppresses the lower sideband.
- Lower Sideband (LSB): Suppresses the upper sideband.
Applications: Primarily for voice transmission; sometimes data.
Frequency Range: Mainly HF, sometimes low VHF.

Spectral Efficiency: Uses less bandwidth by eliminating approximately half of the signal.
Power Efficiency: Concentrates power into one sideband, avoiding waste on the carrier and redundant sideband.
Noise Reduction: Reduced bandwidth leads to lower received noise.

No Technical Difference: Between using upper or lower sideband.
Convention: Decided by mutual agreement. For example, amateur radio uses:
- LSB below 9 MHz.
- USB above 9 MHz.

Transmit Side: Suppresses the carrier and one sideband.
Receive Side: Requires reinsertion of the carrier for demodulation.
Carrier Insertion Oscillator: Reinsert the carrier; any frequency offset affects pitch of received audio.
Pitch Changes: If offset is too large, speech can become unintelligible.

Single-Sideband Suppressed Carrier: Most common variant.
Other Variants:
- Full Carrier: Carrier is not suppressed, easing carrier reinsertion.
- Reduced Carrier: Partial suppression of the carrier.
Special Variants:
- Independent Sideband: Two sidebands carry different information; proposed for AM stereo.
- Vestigial Sideband: Both sidebands present but one is reduced; used in older analog TV broadcasts.

SSB: Amplitude modulation type where carrier and one sideband are suppressed for spectral and power efficiency.
Receive Side: Carrier must be reinserted; frequency differences affect audio pitch.
Variants: Suppressed, full, and reduced carrier; independent and vestigial sidebands for specialized uses.

Conclusion: Understanding SSB and its benefits for RF communications.