IC FSK modem. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Data transfer

 Comments on the article

Currently, there are a number of special modem chips: XR-2206/2211, AM-7910/7911, TCM-3105... Their use simplifies the circuit and greatly facilitates configuration. But in any case, knowledge of the functional diagram of the microcircuit will be useful.

Below is a description of the TCM-3105 chip used in the VHF VHF modem. The material is based on the technical description of the manufacturer.

(click to enlarge)

The transmitting part (Fig. 1) contains a phase-coherent PSK modulator, which determines the high quality of the output signal. Modulator - programmable frequency synthesizer. The division factor that determines the output frequencies is set by dividing the clock frequency set by the 4,4336 MHz quartz. It is also possible to use an external generator connected to the OSC1 pin. The division ratio is set by applying the appropriate signals to the TRS (Transmit/Reseive Standard), TRX1 and TRX2 (Bit Rate Select) and TXD inputs. These signals determine the baud rate and modulation frequencies (Figure 2 and Table 1).

TXD - signal from the computer (positive logic). When a signal is applied from RS-232, the signal must be brought to the CMOS level and inverted (TKRS-232 has negative logic). THA - analog transmitting signal. DC isolation required! (Fig. 1,3).

(click to enlarge)

Table 1

The demodulator uses the principle of frequency-to-voltage conversion. The "receiver" contains a group delay compensator that corrects for phase distortion (signal delay) occurring in the highly selective receive filter and in the "transmission medium". The signal is then clipped and fed to the FSK demodulator. The demodulator circuit can be found in (1]. At the output of the demodulator, there are double-frequency pulses of the input limited signal. Then, a constant component proportional to the received frequency is selected by filtering. The constant component is fed to the comparator, where it is compared with the voltage at the RXB input. This voltage must be selected for different exchange rates, minimizing asymmetric distortion.

The carrier detector compares the received (after the filter) signal with the level at the CDL input. A high level at the CDT output indicates the presence of a carrier. The comparator has a hysteresis of 2,5 dB and has some signal delay (Fig. 4). This ensures reliable and reliable operation.

Literature

1. Jansen I. Course of digital electronics, v.3. M." Mir, 1987

Author: B.Voronkov (UV3DIN), Pushchino; Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Data transfer.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Artificial leather for touch emulation 15.04.2024

In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>

Petgugu Global cat litter 15.04.2024

Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>

The attractiveness of caring men 14.04.2024

The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>

Random news from the Archive High performance semiconductor laser from Sharp 03.01.2013 Sharp has announced the release of a semiconductor laser GH0641FA2C with a wavelength of 642 nm and an efficiency of 33% - according to the manufacturer, a record for such devices. The laser is intended for use as a light source in compact projectors and car displays with image projection on the windshield. The threshold current of the laser LED is 55 mA. With a typical operating voltage of 2,5 V and a current of 182 mA, the optical power is 150 mW. The horizontal and vertical divergence angles are 9° and 17°, respectively. The manufacturer expects to start deliveries of trial samples of new lasers on January 31, 2013 at a price of about $58 per piece, and from March 29, 2013, serial production of GH0641FA2C in the amount of 10000 pieces per month should begin.

Other interesting news:

▪ planet diamond

▪ New User Identification Methods

▪ Portable voice recorder

▪ LED car headlight

▪ Smart watch Hannspree Sportwatch

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Stories from the life of radio amateurs. Selection of articles

▪ article Indian summer. Popular expression

▪ article In which countries participation in elections is mandatory? Detailed answer

▪ article African foxtail. Legends, cultivation, methods of application

▪ article Temperature controller. Encyclopedia of radio electronics and electrical engineering

▪ article Remote control of a VHF radio receiver. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua
2000-2024