Local Oscillator (LO) / Synthesizer

Product Specifications

Technical details and manufacturing context for Local Oscillator (LO) / Synthesizer

Definition

The Local Oscillator (LO) or Synthesizer is an essential electronic component within an RF Transceiver that produces a stable, tunable, and low-phase-noise reference frequency signal. It serves as the frequency source for up-conversion (transmit path) and down-conversion (receive path) by mixing with the incoming/outgoing RF signals, enabling the selection and processing of specific communication channels within the transceiver's operational bandwidth. This component is typically implemented as a phase-locked loop (PLL) synthesizer, which uses a voltage-controlled oscillator (VCO) to generate the output frequency. The VCO output is divided down and compared to a stable crystal oscillator reference via a phase detector; the resulting error voltage adjusts the VCO to lock the output frequency precisely to a multiple of the reference. This architecture allows for stable, programmable frequency synthesis across a defined range, with fine resolution and low phase noise. The LO/Synthesizer is available as a compact module with specified electrical and environmental parameters. Frequency range covers 0.1–20 GHz, with resolution steps of 0.1–10 Hz. Output power is typically 10–20 dBm, adjustable with an external attenuator. Phase noise is specified as -120 to -100 dBc/Hz at 10 kHz offset. Frequency stability is ±0.5 to ±2 ppm over temperature, with an OCXO option for higher stability. Supply voltage is 5–12 V DC, with current consumption of 100–500 mA depending on output power and frequency. Operating temperature range is -40 to 85 °C, and humidity range is 5–95% RH (non-condensing). The module is sealed to IP54–IP65 per IEC 60529. Dimensions range from 50×40×20 mm to 100×80×30 mm, and weight is 50–200 g. Materials include silicon for integrated circuits, gallium arsenide or silicon germanium for high-frequency variants, and quartz for the reference crystal oscillator. These values are directory reference ranges; verify model-specific specifications with the legal manufacturer or supplier.

Working Principle

The LO/Synthesizer typically employs a phase-locked loop (PLL) architecture. A voltage-controlled oscillator (VCO) generates the output frequency, which is divided down and compared to a stable crystal oscillator reference via a phase detector. The resulting error voltage adjusts the VCO to lock the output frequency precisely to a multiple of the reference, allowing for stable, programmable frequency synthesis across a defined range. The loop filter sets the bandwidth and transient response, balancing lock time and phase noise. The output is buffered to provide a consistent level into the mixer. Frequency selection is achieved by changing the divider ratio, typically via a serial interface. The reference crystal oscillator provides the time base; its stability directly affects the output frequency accuracy. The PLL locks the VCO to a multiple of the reference, enabling fine resolution and low phase noise. The module includes power supply regulation and reverse polarity protection. The operating principle is based on negative feedback control, ensuring the output frequency remains locked to the reference. The VCO tuning range and the divider range determine the overall frequency coverage. The phase detector and loop filter are designed to optimize phase noise and spurious performance. The output power is set by the VCO and buffer amplifier, and can be adjusted externally. The module is designed for industrial temperature ranges and sealed against dust and water jets.

Common Materials

Silicon (for integrated circuits), Gallium Arsenide (GaAs) or Silicon Germanium (SiGe) for high-frequency variants, Quartz (for reference crystal oscillator)

Technical Parameters

Parameter	Typical range	Notes & selection driver
Frequency Range	0.1–20 GHz	Covers common RF bands; wider ranges available on request.
Frequency Resolution	0.1–10 Hz	Fine steps for precise tuning.
Output Power	10–20 dBm	Typical output; adjustable with external attenuator.
Phase Noise	-120–-100 dBc/Hz @10kHz	Lower is better for signal purity.
Frequency Stability	±0.5–±2 ppm	Over temperature range; OCXO option for higher stability.
Supply Voltage	5–12 V DC	Single supply; reverse polarity protected.
Current Consumption	100–500 mA	Depends on output power and frequency.
Operating Temperature	-40–85 °C	Industrial grade; extended range optional.
Humidity	5–95 % RH	Non-condensing.
IP Rating	IP54–IP65	Sealed against dust and water jets.IEC 60529
Dimensions	50×40×20–100×80×30 mm	Compact module; custom sizes available.
Weight	50–200 g	Lightweight for portable applications.

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Components / BOM

Voltage-Controlled Oscillator (VCO)
Generates the radio frequency output signal; its frequency is controlled by an input voltage.

Material: Semiconductor (Si, GaAs, SiGe)
Phase-Frequency Detector (PFD)
Compares the phase and frequency of the divided VCO signal with the reference signal and generates an error signal.

Material: Silicon (integrated circuit)
Loop Filter Part
A low-pass filter that smooths the error signal from the PFD to provide a stable control voltage for the VCO.

Material: Passive components (resistors, capacitors)
Frequency Divider
Divides the high-frequency VCO output down to a lower frequency for comparison with the reference in the PFD.

Material: Silicon (digital logic circuits)
Reference Oscillator
Provides a highly stable, low-frequency reference signal (e.g., from a crystal oscillator).

Material: Quartz crystal, supporting silicon circuitry
Output Buffer
Holds the LO output at a constant level into the mixer, and keeps mixer loading off the VCO.
Serial Interface Optional
Loads the divider ratio, and with it the output frequency, from the host.

Applied To / Applications

This component is essential for the following industrial systems and equipment:

RF Transceiver

View system integration details

Manufacturers of Local Oscillator (LO) / Synthesizer

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Frequently Asked Questions

What is the frequency range of this local oscillator/synthesizer?

The directory lists a frequency range of 0.1–20 GHz, covering common RF bands. Wider ranges may be available on request. Always confirm the exact frequency range for your specific model with the legal manufacturer or supplier.

What is the phase noise performance?

The phase noise is specified as -120 to -100 dBc/Hz at 10 kHz offset. Lower values indicate better signal purity. Verify the phase noise specification for your application with the manufacturer, as it may vary with frequency and temperature.

What supply voltage is required?

The supply voltage is 5–12 V DC, single supply, with reverse polarity protection. Current consumption is 100–500 mA depending on output power and frequency. Ensure your power supply meets these requirements and check the specific model's datasheet.

What is the operating temperature range?

The operating temperature range is -40 to 85 °C, industrial grade. Extended ranges may be optional. The module is sealed to IP54–IP65 per IEC 60529, protecting against dust and water jets. Confirm environmental ratings with the manufacturer for your intended use.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

pressure:	Atmospheric to 1 atm (standard), hermetic sealing for harsh environments
other spec:	Frequency stability: ±0.5 ppm, Phase noise: -110 dBc/Hz @ 10 kHz offset, Output power: +10 dBm ±2 dB
temperature:	-40°C to +85°C (operational), -55°C to +125°C (storage)

Product Specifications

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