Telecoms, Datacoms, Wireless, IoT


UHF transceiver for 700 MHz to 1000 MHz

23 October 2002 Telecoms, Datacoms, Wireless, IoT

The MICRF500 from Micrel is a single chip UHF transmitter and receiver intended for ISM (industrial, scientific and medical) and SRD (short range device) frequency bands from 808 MHz to 915 MHz with FSK data rates up to 128 k baud. It can also be programmed for operation at other frequency bands in the 700 MHz to 1000 MHz range.

The transmitter consists of a PLL frequency synthesiser and a power amplifier. The frequency synthesiser consists of a voltage-controlled oscillator (VCO), a crystal oscillator, dual-modulus prescaler, programmable frequency dividers and a phase-detector. The loop filter is external for flexibility and can be a simple passive circuit. The VCO is a Colpitts oscillator which requires an external resonator and varactor. FSK modulation can be applied externally to the VCO. The synthesiser has two different N, M and A frequency dividers. FSK modulation can also be implemented by switching between these dividers (max. 2400 bps). The lengths of the N and M and A registers are 12, 10 and 6 bits respectively. The output power of the power amplifier can be programmed to eight levels. A lock detect circuit will detect when PLL is in lock.

In receive mode the PLL synthesiser generates the local oscillator (LO) signal. The N, M and A values that give the LO frequency are stored in three registers. The receiver is a zero IF (intermediate frequency) type in order to make channel filtering possible with low-power integrated low-pass filters. It consists of a low noise amplifier (LNA) that drives a quadrature mixer pair whose outputs feed two identical signal channels in phase quadrature. Each channel includes a preamplifier, a third order Sallen-Key RC low pass filter that protects the following gyrator filter from strong adjacent channel signals and finally, a limiter.

The main channel filter is a gyrator capacitor implementation of a seven-pole elliptic low pass filter. This filter minimises the total capacitance required for a given selectivity and dynamic range. The cut-off frequency of the RC filter can be programmed to four different frequencies: 10 kHz, 30 kHz, 60 kHz and 200 kHz. An external resistor adjusts the cut-off frequency of the gyrator filter. The demodulator demodulates the I and Q channel outputs and produces a digital data output. It detects the relative phase of the I and the Q channel signal. If the I channel signal lags the Q channel, the FSK tone frequency lies above the LO frequency (data '1'). If the I channel leads the Q channel, the FSK tone lies below the LO frequency (data '0'). There is an RSSI (receive signal strength indicator) circuit that indicates the received signal level. A two pin serial interface is used to program the circuit.

External components are necessary for RF input and output impedance matching and decoupling of power. Other external components are the VCO resonator circuit with varactor, crystal, feedback capacitors and components for FSK modulation with the VCO, loop filter, bias resistors for the power amplifier and gyrator filters. A T/R switch can be implemented with 2-pin diodes. This gives maximum input sensitivity and transmit output power.

The MICRF500's RF output power is 10 dBm, sensitivity is -104 dBm (19,2 k bauds, BER=10-3) and max data rate is 128 k bauds. Applications are found in: telemetry; remote metering; wireless controller; wireless data repeaters; remote control systems; wireless modem; wireless security system. MICRF500BLQ comes in 44-lead LQFP.



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Quectel partners with GEODNET
Quectel Wireless Solutions Telecoms, Datacoms, Wireless, IoT
Quectel Wireless Solutions has partnered with GEODNET to deliver Quectel’s Real-Time Kinematic (RTK) correction services, enabling high-precision positioning for IoT applications.

Read more...
Bringing Bluetooth Channel Sounding to automotive and beyond with KW47
Altron Arrow Telecoms, Datacoms, Wireless, IoT
NXP’s new Channel Sounding-certified KW47 and MCX W72 wireless MCUs are set to help automakers with distance measurement, bringing an additional ranging solution for car access and autonomous systems, and will be utilised across a broader spectrum of applications.

Read more...
Dual-band GNSS antenna
RF Design Telecoms, Datacoms, Wireless, IoT
The Taoglas Accura GVLB258.A, is a passive, dual-band GNSS L1/L5, high-performance antenna for high precision GNSS accuracy and fast positioning.

Read more...
What is Wi-Fi HaLow and why choose it for IoT?
iCorp Technologies Editor's Choice Telecoms, Datacoms, Wireless, IoT
Wi-Fi HaLow introduces a low power connectivity option that, in contrast to other Wi-Fi options, offers greater range of approximately 1 km, which opens up a raft of IoT use cases.

Read more...
Wi-Fi 6 and Bluetooth LE coprocessor module
Altron Arrow Telecoms, Datacoms, Wireless, IoT
The ST67W611M1 from STMicroelectronics boasts an all-in-one design which, together with its capabilities, contribute to making it an attractive choice for IoT edge devices requiring a single-chip solution.

Read more...
Futureproofing IoT connectivity
SIMcontrol Telecoms, Datacoms, Wireless, IoT
A managed private APN assigns every device to an isolated carrier slice, producing a single ingress to the enterprise network, with traffic bypassing shared internet paths and reducing exposure.

Read more...
Extra slim 2,4 GHz radio module
Telecoms, Datacoms, Wireless, IoT
The Thyone I radio module from Würth Elektronik now has a little sibling: Thyone-e, which takes up 30% less space and represents a cost-effective alternative for applications in which the long-range mode is not required.

Read more...
Wi-Fi 6 plus Bluetooth LE SoC
Altron Arrow Telecoms, Datacoms, Wireless, IoT
Silicon Labs’ SiWx917M SoC is the company’s lowest power Wi-Fi 6 SoC, ideal for ultra-low power IoT wireless devices using Wi-Fi, Bluetooth, Matter, and IP networking for secure cloud connectivity.

Read more...
Two Bluetooth protocols – one module
Telecoms, Datacoms, Wireless, IoT
Würth Elektronik has introduced its Skoll-I, a compact wireless module that combines both Bluetooth Classic and Bluetooth Low Energy version 5.4 into a single solution.

Read more...
Compact high-performance antennas
Electrocomp Telecoms, Datacoms, Wireless, IoT
KYOCERA AVX offers a variety of extremely compact and high-performance internal, on-board, multiprotocol 2,4 GHz antennas ideal for use in SiP applications.

Read more...