Tag Archives: RF

VHF-UHF RF Sniffer

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by simpletronic @ instructables.com

This is a multi-chapter instructable. I will be describing the making of a short/medium range RF remote-control using the UHF 433Mhz frequency. It´s impossible to setup & adjust a RF transmit-receive link if you are not sure the transmitter is working properly.At 433MHz, your multimeter or even a regular oscilloscope are totally useless.

VHF-UHF RF Sniffer – [Link]

The Simple Scalar Network Analyzer

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by rheslip.blogspot.com:

After playing around with the SynthNV signal generator/power detector discussed in the previous post I realized what a useful a tool it is for RF testing. While its a terrific tool for VHF/UHF/Microwave testing, the SynthNV has a couple of serious limitations for amateur use in the HF region – the signal generator has a minimum frequency of 35 MHz, the generated signal has a lot of harmonics and its a fairly expensive piece of gear. This project is a fairly simple, very low cost Scalar Network Analyzer that does the same thing in the HF bands from 1MHz to 30MHz. If you buy the parts from China or Ebay and do some scrounging it should cost you less than $20 to build.

The Simple Scalar Network Analyzer – [Link]

RFM69HCW transceiver can go up to 20dBm

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This powerful RF transceiver is also highly secure thanks to a HW support of CRC-16 and AES-128.

The RFM69HCW is a highly integrated RF transceiver capable of operation over a wide frequency range, including the 433, 868 and 915 MHz license-free ISM (Industry Scientific and Medical) frequency bands. Its highly integrated architecture allows for a minimum of external components whilst maintaining maximum design flexibility.All major RF communication parameters are programmable and most of them can be dynamically set. The RFM69HW offers the unique advantage of programmable narrow-band and wide-band communication modes without the need to modify external components. The RFM69HW is optimized for low power consumption while offering high RF output power and channelized operation. TrueRF™ technology enables a low- cost external component count (elimination of the SAW filter) whilst still satisfying ETSI and FCC regulations.

On stock we also keep a less powerful version – RFM69CW, suitable for all applications where a lower range is sufficient.

RFM69HCW transceiver can go up to 20dBm – [Link]

Visualizing RF Standing Waves on Transmission Lines

This video illustrates how RF (radio frequency) standing waves are created in transmission lines – through the addition of the forward (transmitted) wave and the reflected wave that results from improperly terminating the line or matching the load or antenna to the transmission line impedance. I have done several videos that relate to transmission lines, terminations and reflections – all of which tell a piece of the story. This video is another piece, and I hope it helps you to understand how standing waves are formed and what the “look” like.

Visualizing RF Standing Waves on Transmission Lines – [Link]

Narrowband RF Power Amplifier (520MHz)

The RF power amplifier stage is usually the final active block of any electronic system that is transmitting RF power. Relatively low power RF signals are amplified to produce a more powerful signal in order to be transmitted over greater distance. RF output power can range from a few mW to MW, depend by application. RF amplifiers before were all made using vacuum tubes but modern RF amplifier nowadays uses solid state devices like MOSFET, TMOS-FET, Bipolar junction transistors, and IGBT to amplify RF signals.

This circuit features the Freescale AFT05MP075GNR1 RF power LDMOS transistor as its RF amplifier solid state device. With the use of some components and proper board layouting, Freescale was able to create a 70 watts RF power amplifier with a gain of 18.5dB. This circuit requires a 12.5Vdc power supply able to provide the maximum power this LDMOS transistor can give. In this circuit, AFT05MP075GNR1 was configured to amplify RF signal with a carrier frequency of 520MHz suitable for UHF band mobile radio applications.

The Freescale AFT05MP075GNR1 was designed for mobile two-way radio applications with frequencies ranging from 136 to 520 MHz. It can be configured as a narrowband or wideband RF power amplifier. The high gain, ruggedness and broadband performance of this device make it ideal for large-signal, common source amplifier applications in mobile radio equipment. It can operate exceptionally in a very wide temperature range, from -40 to +150 degree Celsius. Though this device handles wideband application, it can still give full power across the band.

Narrowband RF Power Amplifier (520MHz) – [Link]

LoRa = RF modules with a long range

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Modern spread spectrum modulation enables HopeRF LoRa modules to communicate on a long distance or in severe environment.

Extraordinary price-attractive modules from company HOPERF Micro-electronics specializing to RF modules and a wireless signal transmission were introduced to you in our article HOPERF – universal RF modules for surprising prices.This time we come with a novelty – module RFM95SW with a „LoRa“ suffix, indicating membership with a „Long Range“ family of modules. Long range of HopeRF LoRa modules is reached by usage of a modern efficient modulation with a spread spectrum, able to transmit data even on a noise floor level. RFM95W solves a traditional compromise among range, immunity (selectivity) and a power consumption while conforming to limits for usage in free bands.

LoRa modulation is quite complex and a user has a possibility to adjust all three main modulation parameters in order to fully meet requirements of a given application. These parameters are spreading factor, modulation bandwidth and error coding rate. For example if don´t need maximum transmission speed, we can set parameters so as to gain the highest possible quality and reliability of connection. By setting these three parameters we can choose an optimal combination for a given application.

RFM95W is ideal for OEM products with higher production series, where development costs usually get quickly refund also thanks to a very affordable price of these modules.

Detailed information will provide you the RFM95SW datasheet. To make a development easier, the RFDK_RFMxx starter kit is also available (upon order).


LoRa = RF modules with a long range – [Link]

Increasing Outputs from a Clock Source

In digital electronics, fan-out is defined as the number of gate inputs that the output of a single logic gate can feed. It is very important in digital systems for a single logic gate to drive other gates or devices. In this case, a buffer can be used between the logic gate and the devices it will drive. Clock buffer is also called as fan-out buffer. The IDT clock buffer clock divider and clock multiplexer portfolio includes devices with up to 27 outputs. Differential outputs such as LVPECL, LVDS, HCSL, CML, HSTL, as well as selectable outputs, are supported for output frequencies up to 3.2 GHz and single-ended LVCMOS outputs for frequencies up to 350MHz.

Modern digital systems often require many high quality clocks at logic levels that are different from the logic level of the clock source. Extra buffering may be required to guarantee accurate distribution to other circuit components without loss of integrity. Many systems require low jitter multiple system clocks for mixed signal processing and timing. The circuit shown in interfaces the ADF4351 integrated phase-locked loop (PLL) and voltage-controlled oscillator (VCO) to the ADCLK948, which provides up to eight low voltage differential signaling (LVDS) outputs from one differential output of the IDT 8SLVD1208-33. The IDT8SLVD1208-33I is characterized to operate from a 3.3V power supply. Guaranteed output-to-output and part-to-part skew characteristics make the IDT8SLVD1208-33I ideal for those clock distribution applications demanding well-defined performance and repeatability. Two selectable differential inputs and eight low skew outputs are available. The integrated bias voltage reference enables easy interfacing of single-ended signals to the device inputs. The device is optimized for low power consumption and low additive phase noise.

Fan-out buffers and clock dividers are general-purpose clock building block devices that can be used in any number of applications. They are ideal for clock and signal distribution in a large variety of systems, from personal computers to consumer electronics or industrial systems, as well as high-performance networking and communications systems.

Increasing Outputs from a Clock Source – [Link]

LDMOS Transistor Bias Control in RF Power Amplifiers

LDMOS

Nowadays, laterally diffused metal oxide semiconductor (LDMOS) transistors are widely used for RF Power Amplification and in many applications. A simplified circuit of an LDMOS amplifier bias circuit is shown in the schematic diagram above. The DC Bias on these amplifiers is set by applying a DC voltage to the gate (VGS) and by monitoring the Drain current (IDD). Ideally, this IDD will be constant over temperature, but since the VGS of LDMOS amplifier devices varies with temperature, some type of temperature compensation is required.

The ISL21400 features a precision voltage reference combined with a temperature sensor whose output voltage varies linearly with temperature. The precision 1.20V reference has a very low temperature coefficient, and its output voltage is scaled by an internal DAC (VREF) to produce a temperature stable output voltage that is programmable from 0V to 1.20V. The output voltage from the temperature sensor (VTS) is summed with VREF to produce a temperature dependent output voltage. The maximum voltage supply of the ISL21400 is 5.5V, and the LP2950 voltage regulator drops the LDMOS voltage to 5.5V for the ISL21400 supply. An LC filter is then added to the output of the voltage regulator to ensure no RF energy present on the supply line. The ISL21400 can be tied to a microcontroller or to any I/O connector for PC control and programming.

The RFPA bias control using the ISL21400 is very straightforward. The RFPA uses the Freescale AFT21S140W02GSR3. LDMOS are useful devices for many applications including commercial FM broadcasting and TV power transmitters, cellular and paging communication systems, and military RF and microwave hand-held transceivers.

LDMOS Transistor Bias Control in RF Power Amplifiers – [Link]

IQRF module TR72D communicates at up to 600m distance

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Higher RF power, GMSK modulation and extra low power consumption make a new communication module interesting even for rough conditions.

At cars, chip-tuning usually results in a higher power of a motor. Even the new communication module (transceiver) TR72D from IQRF has passed such „chip-tuning“ of RF portion, resulting in a higher max. RF output (up to 12mW). New RF chip – Spirit1, used at TR72D also provides excellent sensitivity and GMSK modulation (Gaussian Minimum Shift Keying) with high resistance to interference. That´s why the new module is able to transfer data at much higher distance than previous types (up to 600m on a free space). This improvement has one limitation – the new module is usable with applications originally developed for previous types, but it´s not usable in one RF network simultaneously with older types (because of a different modulation).Basically the new module TR72D offers the same straightforward development of devices with a wireless communication as previous modules. The best idea about differences among particular types will give you the attached table. TR72D is a hot novelty from which we have first engineering samples. Version „DAx“ also contains built-in antenna.

Features of IQRF technology, description of the development environment and other features can be found in a record of our webinar Wireless MESH networks without programming.

Detailed information will provide you the Wago 2059-2060-2061 brochure.

IQRF module TR72D communicates at up to 600m distance – [Link]