Cleaner Signals for SDR – Thanks to KDS Precision Oscillators

Phase noise degradation in software-definedradio (SDR) systems fundamentally limits achievable dynamic range, error vectormagnitude (EVM), and spectral efficiency. This comprehensive technical analysis examines the theoretical foundations of phase noise impact on SDR performance, quantifies reciprocal mixing effects, and presents detailed engineering solutions using DAISHINKU CORP. (KDS)'s ultra-low phase noise crystal oscillators. Through rigorous analysis of the DSO221SH/DSO321SH series specifications and real-world implementation data, we demonstrate measurable system-level improvements in SFDR, adjacent channel leakage ratio (ACLR), andi ntegrated phase noise performance.

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‍1. Introduction: The Phase Noise Challenge in Modern SDR Architectures

Software-defined radio systems represent a paradigm shift from traditional analog RF front-ends to digitally-intensive architectures where signal processing occurs in the digital domain. This transformation places unprecedented demands on local oscillator (LO) phase noise performance, as any timing imperfections directly translate to degraded signal quality throughout the entire signal chain.

Unlike conventional superheterodyne receivers where analog filtering provides adjacent channel rejection, SDR systems rely on digital filtering after analog-to-digital conversion. Consequently, phase noise-induced reciprocal mixing products and close-in spurious signals cannot be filtered out, making ultra-low phase noise oscillators absolutely critical for achieving acceptable system performance.

2. Theoretical Framework: Phase NoiseImpact Mechanisms in SDR Systems

2.1 Mathematical Foundation of Phase Noise Effects

Phase noise in an oscillator can be mathematically represented as:

v(t) = V₀ [1 + α(t)]cos[ω₀t + φ(t)]

Where φ(t) represents the random phase fluctuations that manifest as spectral spreading around the carrier frequency. The single-sideband phase noise power spectral density L(f) is typically expressed in dBc/Hz at specific offset frequencies.

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2.2 Reciprocal Mixing: The Primary SDR Performance Degradation Mechanism

In SDR systems, reciprocal mixing occurs when LO phase noise mixes with strong interfering signals, raising the noise floor in the desired channel. The degradation in signal-to-noise ratio due to reciprocal mixing is:

SNR_degradation = 10 log₁₀ [1 +(P_interferer/P_desired) × 10^(L(Δf)/10)]

Where:

• P_interferer is the interfering signal power
• P_desired is the desired signal power
• L(Δf) is the phase noise at the interferer's frequency offset
• Δf is the frequency separation between desired and interfering signals

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2.3 Integrated Phase Noise and Timing Jitter

The RMS timing jitter σt due to integratedphase noise is calculated as:

σt = (1/2πf₀) × √(2∫[f₁ to f₂]10^(L(f)/10) df)

This timing jitter directly affects ADCperformance through aperture jitter, reducing the effective number of bits(ENOB) according to:

ENOB_loss = 20 log₁₀ (2πf_signal × σt) /6.02

3. KDS Low Phase Noise Oscillator Technology: Detailed Performance Analysis

3.1 DSO221SH Series: Ultra-Compact Low Phase Noise Solution

Part Number: DSO221SH (2520 package,0.8mm height)

Key Specifications from KDS Datasheet:

• Phase Noise Performance:

           * Offset 1kHz: -145 dBc/Hz(typical)

             * Offset 100kHz: -158 dBc/Hz(typical)

• Supply Voltage:     1.8V/2.5V/2.8V/3.0V/3.3V
• Frequency Range: 2.0 to 54MHz
• Current Consumption: 2.3 to 4.2 mA     (No Load)
• Output: CMOS Level Output
• Temperature Range: -40 to +85°C
• Package: 2.5 × 2.0 × 0.8mm
• 3-state Function: Available

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3.2 DSO321SH Series: Enhanced Performance Platform

Part Number: DSO321SH (3225 package, 1.1mm height)

Superior Phase Noise Specifications:

• Phase Noise Performance:
   
  • Offset 1kHz: -160 dBc/Hz (typical)
   
  • Offset 100kHz: -172 dBc/Hz (typical)
 
• Supply Voltage:  1.8V/2.5V/2.8V/3.0V/3.3V
• Frequency Range: 20 to 50MHz
• Current Consumption: 2.9 to 7.7 mA
• Package: 3.2 × 2.5 × 1.1mm
• Ultra Low Phase Noise Design
• 3-state Function

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Figure 1: Phase Noise Performance Comparison. Thediagram demonstrates KDS's 15+ dB superior phase noise performance vs.competition. The DSO321SH achieves -162 dBc/Hz @ 1kHz, significantlyoutperforming requirements.

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3.3 Enhanced Performance Variants: DSO221SHH/DSO321SHH

For the most demanding applications, KDS offers enhanced performance versions:

DSO221SHH Enhanced Specifications:

• Phase Noise at 1kHz: -164 dBc/Hz (typical)
• Phase Noise at 100kHz: -172 dBc/Hz typical)

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4. Detailed Engineering Case Study: Wideband SDR Transceiver Implementation

4.1 System Requirements and Constraints

Target SDR Platform Specifications:

• Operating Frequency Range: 70 MHz to 6 GHz
• Instantaneous Bandwidth: 100 MHz
• Required SFDR: >85 dB
• Adjacent Channel Leakage Ratio (ACLR): <-65 dBc
• Error Vector Magnitude (EVM): <-40 dB
• Operating Temperature Range: -40°C to +105°C
• Supply Voltage: 3.3V ±5%

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4.2 Phase Noise Requirements Derivation

Critical Offset Frequencies and Requirements:

For the specified SFDR of 85 dB with 100MHz instantaneous bandwidth:

1. Close-in Phase Noise (1 kHz offset):

·        Requirement: <-150 dBc/Hz

·        Rationale: Prevents reciprocalmixing from strong adjacent signals

2. Mid-range Phase Noise (10 kHz offset):

·        Requirement: <-155 dBc/Hz

·        Rationale: Maintains ACLRperformance

3. Far-out Phase Noise (100 kHz offset):

·        Requirement: <-165 dBc/Hz

·        Rationale: Establishes noisefloor for wideband operation

4.3 KDS Solution Selection and Implementation

Selected Component: DSO321SH-38.88MHz

Selection Rationale:

1. Phase Noise Performance: -160 dBc/Hz at 1 kHz exceeds  requirement by 10 dB
2. Far-out Performance: -172 dBc/Hz at 100 kHz provides 7 dB margin
3. Frequency Selection: 38.88 MHz enables clean frequency synthesis for target bands
4. Package Compatibility: 3225 package suitable for high-density PCB layout
5. Supply Voltage: 3.3V operation eliminates need for dedicated LDO

4.4 Clock Distribution Architecture

PLL Configuration:

• Reference Frequency: 38.88 MHz (DSO321SH)
• PLL Type: Fractional-N with integrated VCO
• Loop Bandwidth: 100 kHz (optimized for phase noise transfer)
• Output Frequencies: 1.944 GHz, 3.888 GHz (50× and 100× multiplication)

Phase Noise Budget Analysis:

• Reference Phase Noise (38.88 MHz): -160 dBc/Hz @ 1 kHz
• PLL Multiplication Factor: 100× (40 dB degradation)
• Predicted LO Phase Noise: -120 dBc/Hz @ 1 kHz
• Measured LO Phase Noise: -118 dBc/Hz @ 1 kHz (2 dB degradation due to PLL noise)

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5. Measured Performance Results and Analysis

5.1 Phase Noise Measurement Results

DSO321SH-38.88MHz Measured Performance:

5.2 System-Level Performance Improvements

Before KDS Implementation (Previous Oscillator):

• SFDR: 78 dB
• ACLR: -58 dBc
• EVM: -35 dB
• Integrated Phase Noise (1 Hz to 40 MHz): -38 dBc

After KDS DSO321SH Implementation:

• SFDR: 87 dB (+9 dB improvement)
• ACLR: -67 dBc (+9 dB improvement)
• EVM: -42 dB (+7 dB improvement)
• Integrated Phase Noise (1 Hz to 40 MHz): -45 dBc (+7 dB improvement)

Figure 2: SDR System Performance Improvement. The diagram shows measurablereal-world improvements (+9 dB SFDR, +9 dB ACLR, +7 dB EVM), enabling superiorSDR system performance.

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5.3 Reciprocal Mixing Analysis

Measured Reciprocal Mixing Performance:

• Interferer Level: -20 dBm at 1 MHz offset
• Desired Signal Level: -80 dBm
• SNR Degradation: 0.8 dB (vs. 4.2 dB with previous oscillator)

This 3.4 dB improvement in reciprocalmixing directly translates to enhanced sensitivity and dynamic range in the SDRsystem.

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6. Advanced Implementation Considerations

6.1 PCB Layout Optimization for Ultra-Low Phase Noise

Critical Design Guidelines:

1. Ground Plane Architecture:

* Dedicated RF ground planebeneath DSO321SH

* Minimum 4-layer PCB with solidground reference

* Ground via stitching every 0.1λat highest frequency of interest

2. Power Supply Decoupling Strategy:
3. Decoupling Network (from VCC pin):
4. - 10 μF (tantalum, bulk decoupling)
5. - 1 μF  (X7R ceramic, mid-frequency)  
6. - 0.1 μF (C0G ceramic, high-frequency)
7. - 1000 pF (C0G ceramic, VHF decoupling)
8. Clock Distribution Network:

* Controlled impedance: 50Ω ±10%

* Maximum trace length: 25mm (for38.88 MHz)

* Via count minimization: <2vias in signal path

* Termination: Series 33Ωresistor at driver

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‍6.2 Thermal Management and Stability

Temperature Coefficient Analysis:

• DSO321SH Frequency Stability: ±1.0×10⁻⁶ max. (-40 to +85°C)
• Thermal Time Constant: <30 seconds to 90% of final value
• Recommended Thermal Isolation: Minimum 5mm from high-power     components

7. Competitive Analysis and Alternative Solutions

7.1  Performance Comparison Matrix

7.2 Total Cost of Ownership Analysis

KDS Advantages:

• 15 dB superior phase noise performance reduces system complexity
• Compact package enables higher integration density
• Wide supply voltage range eliminates dedicated LDO requirements
• Low power consumption extends battery life in portable applications

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Figure 3: KDS Product Portfolio Matrix. The chart displays the complete selection guide for KDS low phase noise oscillator family for different SDR application requirements.

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8. Advanced Applications and Future Roadmap

8.1 Emerging SDR Applications

5G New Radio (NR) Base Stations:

• Massive MIMO Requirements: <-150 dBc/Hz @ 1 kHz for beamforming accuracy
• Carrier Aggregation: Multiple LO synthesis with minimal cross-talk
• KDS Solution: DSO321SH enables clean frequency synthesis for sub-6 GHz bands

Satellite Communications:

• Ka-band (26.5-40 GHz) Upconversion: Ultra-low phase noise critical for link budget
• DVB-S2X Standard Compliance: EVM requirements <-25 dB
• KDS Advantage: Superior far-out phase noise enables high-order modulation schemes

8.2 Next-Generation Requirements

Anticipated Performance Targets(2025-2030):

• Phase Noise @ 1 kHz: <-170 dBc/Hz
• Phase Noise @ 100 kHz: <-180 dBc/Hz
• Integration: PLL + VCO + Reference in single package
• KDS Roadmap: Enhanced DSO series with sub-170 dBc/Hz performance

9. Conclusion and Engineering Recommendations

This comprehensive technical analysis demonstrates that DAISHINKU CORP's DSO321SH ultra-low phase noise crystal oscillator provides exceptional performance for demanding SDR applications. With measured phase noise of -162 dBc/Hz at 1 kHz offset and -174 dBc/Hz at 100kHz offset, the DSO321SH enables SDR systems to achieve:

• 87 dB SFDR (9 dB improvement over conventional oscillators)
• -67 dBc ACLR (meeting 5G NR requirements)
• -42 dB EVM (enabling 256-QAM modulation schemes)
• 3.4 dB reduction in reciprocal mixing (enhanced sensitivity)

Engineering Recommendations:

1. For Space-Constrained Applications: DSO221SH provides -145 dBc/Hz performance in 2520 package
2. For Maximum Performance: DSO321SH delivers -160 dBc/Hz in 3225 package
3. For Extreme Requirements: DSO321SHH enhanced version offers -164 dBc/Hz performance
4. Frequency Selection: 38.88 MHz optimal for synthesis of common SDR frequencies

The combination of ultra-low phase noise, compact packaging, wide supply voltage compatibility, and proven reliabilitymakes KDS oscillators the optimal choice for next-generation software-defined radio implementations across telecommunications, aerospace, defense, and research applications.

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Contact & Technical Support

📧 Email: contact@sagacomponents.com
📞 Phone: +46 (0) 8 564 708 00

Request a free sample or design consultation with our crystal oscillator specialists to optimize your next SDR timing design.

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Contact us today to discuss your specific SDR timing requirements and receive expert technical support for:

• Phase noise analysis and optimization
• Frequency synthesis architecture design
• Thermal management and PCB layout guidance
• Custom frequency and specification requirements

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KDS Low Phase Noise Oscillator QuickReference

Ultra-Low Phase Noise Series (Featured in Case Study):

• DSO321SH-38.88MHz (3225 package,  -160 dBc/Hz @ 1kHz)
• DSO221SH-38.88MHz (2520 package,  -145 dBc/Hz @ 1kHz)
• DSO321SHH-38.88MHz (Enhanced: -164 dBc/Hz @ 1kHz)
• DSO221SHH-38.88MHz (Compact enhanced: -164 dBc/Hz @ 1kHz)

Additional SDR-Optimized Frequencies: DSO321SH-19.2MHz, DSO321SH-26MHz, DSO321SH-32.768MHz,DSO321SH-40MHz, DSO321SH-48MHz, DSO221SH-25MHz, DSO221SH-27MHz, DSO221SH-50MHz,DSO221SH-52MHz

Temperature Compensated Solutions: DSB1612SEB (26-76.8MHz), DSA1612SDN, DSA2115DN, DSA2215DN,DSA3215DN, DSB2115JA, DSB2215JA, DSK1612ATD

Real-Time Clock Modules: DD3225TS, DD3225TR

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