Weather Balloon Radiosondes

Spy balloon with solar panels, military equipment with camera on sky with clouds

A radiosonde is a battery-powered telemetry instrument carried into the atmosphere by a weather balloon. From a high altitude and often extremely low temperatures, radiosondes transmit sensor data to a ground station. The timing products in radiosondes must reliably operate in an extended temperature.

SiTime MEMS timing solutions offer robust performance in harsh operating conditions – from wide temperatures to shoch and vibration. Additionally, they are available in smaller, lightweight packagers and offer low power features.

Download Application Brief

SiTime MEMS Timing Benefits

Environmentally robust

Excellent stability over temperature

No cold start issues

Shock and vibration resistance

Size and power efficient

Small footprints

Low power consumption

Drives multiple loads

Easy to use, built to last

Wide operating temperature

No quartz reliability issues

>2 billion hour MTBF

Hundreds of radiosondes are launched all over the world daily and are an essential source of meteorological data. Radiosondes measure various atmospheric parameters such as altitude, pressure, temperature, relative humidity, wind, cosmic rays, ozone concentration. Data are transmitted to ground stations via radio link.

Radiosondes rely on several clocks:

Microcontroller clock: Usually in the 16 to 40 MHz range. Although crystal resonators can be used for this purpose, SiTime oscillators have many advantages (see page 4).
RTC clock: Optional in this application, as the GPS features a time-of-day function. Some radiosondes are equipped with it.
GNSS receiver clock: Provided by a TCXO.
RF transmitter clock: Can be provided by a crystal resonator, an oscillator or a TCXO, depending on the transmitter chipset used.

Radiosondes Block Diagram

MEMS Timing for Radiosondes (Commercial Grade Products)

SiTime MEMS timing products are ideal for a range of industrial applications. They can be factory programmed to a wide combination of frequency, output and supply voltage options, eliminating the long lead times and customization costs associated with quartz products.

Device	Key Features	Key Values
MHz Oscillator SiT8021 1 to 26 MHz	Ultra low power: < 270 µA at 6.144 MHz, 1.8 V, 10 pF load 1.5 x 0.8 mm package ±50 and ±100 ppm options 1.62 to 3.63 V supply	Saves power, maximizes battery life Saves board space
MHz Oscillator SiT8918 1 to 110 MHz	-40°C to 85°C ±20 to ±50 ppm freq stability 2.0 x 1.6 mm, 2.5 x 2.0 mm, 3.2 x 2.5 mm, 5.0 x 3.2 mm, 7.0 x 5.0 mm packages	High reliability High temperature operation Various standard package options Immunity to EMI
Differential Oscillator SiT9501 25 to 644.5 MHz (70 fs^[1] IPJ)	±20 to ±50 ppm freq stability LVPECL, LVDS, HCSL 1.8 V to 3.3 V -40°C to 105°C 2.0 x 1.6 mm, 2.5 x 2.0 mm, 3.2 x 2.5 mm packages	Meets demanding jitter requirements Small PCB footprint, easier layout Easy design due to flexibility Better MEMS reliability
Super-TCXO SiT5155 12 frequencies from 10 MHz to 40 MHz	±0.5 ppm freq stability -40°C to 105°C 5.0 x 3.2 mm package	Designed for GNSS/GPS Higher dynamic performance for faster lock to satellites in harsh environments
Super-TCXO SiT5376 1 to 220 MHz SiT5377 1 to 220 MHz	±0.1 to ±0.25 ppm freq stability -40°C to 105°C 5.0 x 3.5 mm package	Designed for RF systems Low-phase-noise Digital control, pull up to ±400 ppm
32.768 kHz XO SiT1532 32.768 kHz SiT1534 1 to 32.768 Hz	900 nA typ. power consumption 1.2 V to 3.63 V operation 1.5 x 0.8 mm and 2.0 x 1.2 mm packages	Saves power, maximizes battery life Programmable output swing for further power savings Small footprint saves board space Internal VDD filtering eliminates external bypass capacitor: BOM cost reduction and further space savings
32.768 kHz XO SiT1569 1 Hz to 462.5 kHz MHz	3.3 µA current consumption at 100 kHz ±50 ppm stability 1.5 x 0.8 mm package	Saves power, maximizes battery life Programmable output swing for further power savings Small footprint saves board space Internal VDD filtering eliminates external bypass capacitor: BOM cost reduction and further space savings
32.768 kHz TCXO SiT1552 32.768 kHz	±5 to ±20 ppm 990 nA typ. consumption 1.5 V to 3.65 V supply range 1.5 x 0.8 mm package	Saves power, maximizes battery life Programmable output swing for further power savings Small footprint saves board space Internal VDD filtering eliminates external bypass capacitor: BOM cost reduction and further space savings

^[1] 12 kHz to 20 MHz integration range

MEMS Timing for Radiosondes (Endura Ruggedized Products)

Endura products are designed for aerospace, defense, and other ruggedized applications. They can be factory programmed to a wide combination of frequency, output and supply voltage options, eliminating the long lead times and customization costs associated with quartz products.

Device	Key Features	Key Values
Single ended oscillator SiT8944 1 to 60 MHz SiT8945 60 to 220 MHz	±10 to ±50 ppm freq stability over temp range -55°C to 105°C 0.1 ppb/g frequency stability Low jitter < 0.5 ps RMS^[1] 1.8 V, 2.5 V, 3.3 V	Better frequency and jitter margin enhance system stability and robustness Easy availability of any device configuration MEMS reliability Minimizes EMI from the oscillator
Differential oscillator SiT9356 1 to 220 MHz SiT9357 220 MHz to 944 MHz	Low jitter 150 fs RMS^[1] LVPECL, LVDS, HCSL, FlexSwing ±30 ppm freq stability over temp range 1.8V, 2.5, 3.3 V -55°C to 125°C 2.0 x 1.6 mm QFN package	Meets demanding jitter requirements Small PCB footprint, easier layout Easy design due to flexibility 0.04 ppb/g acceleration sensitivity for harsh environments MEMS reliability Minimizes EMI from the oscillator
Differential oscillator SiT9551 14 standard frequencies from 25 MHz to 644 MHz	Low jitter 70 fs RMS^[1] LVPECL, LVDS, HCSL, FlexSwing ±20 and ±50 ppm freq stability up to -55°C to 125°C 2016, 2520 and 3225 packages	Meets demanding jitter requirements Small PCB footprint, easier layout Easy design due to flexibility 0.04 ppb/g acceleration sensitivity for harsh environments MEMS reliability Minimizes EMI from the oscillator
Super-TCXO SiT5146 1 to 60 MHz	±0.5 to ±2.5 ppm freq stability -55°C to 105°C 5.0 x 3.2 mm package	Ultra-wide operating temperature Low 0.31 ps phase jitter (rms) Higher dynamic performance for faster lock to satellites in harsh environments
32.768 kHz Super-TCXO SiT7910 32.768 kHz	±0.1 to ±0.4 ppm freq stability -55°C to 105°C 5 μA current consumption 3.5 ppm 20-year aging at 85°C 2.5 x 2.0 mm ceramic package	Unique combination of low power and frequency stability – only possible with MEMS! Enables fast GNSS signal acquisition without compromising power

^[1] 12 kHz to 20 MHz integration range

SiTime Oscillator Advantages for Radiosondes

Wide operating temperature range: From ground level to the stratosphere, radiosondes are exposed to a wide temperature.
Guaranteed operation at -55°C: MEMS technology is not subject to the issues plaguing crystals, in particular cold start, i.e., a crystal failure to start oscillating at cold temperatures. A solution to this limitation of quartz crystals is to increase the crystal drive current. However, besides running the risk of exceeding the maximal drive current of the crystal, it consumes higher power, which is detrimental to such battery-operated systems.
Resilience to shock and vibration: Due to the smaller size and lower vibrating mass of the MEMS resonator, as well as better strength of silicon, SiTime MEMS oscillators are 100x more resilient to shock and vibration than crystal-based oscillators.
Low power consumption: Because battery capacity drops with lower temperatures, low power consumption is even more important for devices operating in cold conditions.

MEMS Timing Outperforms Quartz

Higher Reliability	Smallest Size, Lower BOM
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Weather Balloon Radiosondes