Electronic Circuits, Modems, and Analog-Digital Conversion

Posted on Jan 17, 2025 in Technology

Unit 8: Switches and Their Functionality

A switch is a device that can be used to either establish or remove (also called make or break) connections between at least two points in an electric or electronic circuit. The mechanical or electromechanical parts which help the contacts to physically touch and separate are called actuators. A switch can be considered to be a gate which either allows or disallows a certain entity.

Key Components and Properties of Switches

  • Actuators: The component that helps the contacts to physically touch and separate.
  • Contacts: Small metallic pieces in a regular electric switch that control power to domestic appliances.

Properties of Metallic Contacts:

  • High resistance is not a property of metallic contacts.

Types of Switches:

  • SPST (Single Pole – Single Throw): Refers to a single contact and a single movement.

Gate Array Based Logic (GAL):

  • The present tennis scoring system includes input devices for each player to indicate whether one player or the other has won a particular point.
  • A common display and annunciator unit may be used, which receives signals from input devices of each player.
  • A league and tournament system is disclosed which includes a centralized league machine that transmits data to one or more of a plurality of electronic dart games via modem or using a wireless portable data storage device.

Calibration and Design Considerations

Fine-tuning can be accomplished by monitoring the pressure and comparing it with a known reference source, such as a nearby airport or National Weather Service.

The contacts are made to physically touch each other to make a circuit, while separation between them breaks it. The mechanical or electromechanical part which helps the contacts to physically touch and separate are called actuators. These could be a spring-loaded toggle, a rocker, an electrically operated relay, a push-button, etc. Electronic hardware technology provides us with miniature logic gates which can be put together in large numbers on a single chip, which can function as a system of logic. This is an automatic traffic light controller and can be implemented by programming any gate array based logic (GAL) device such as FPGA. The design is generic and can be customized to suit different types of road junctions with minor changes.

Assumptions/Design Criteria for 1-Wire Barometer

  1. This will minimize output variations caused by temperature and will lengthen the calibration intervals.
  2. Will be easy to calibrate.
  3. The operating range will be from 28.00 inHg to 32.00 inHg.
  4. The interface will be standard Dallas Semiconductor 1-wire.

Reductions in the number of elements required to realize each function makes it possible to use fewer chips or to do more on a given chip. In high-performance systems, eliminating redundant gates not only frees up chip area, it reduces power dissipation, often the limiting factor.

Unit 9: Modems and Multiplexing

Multiplexing equipment used by the news services in the year 1920s are not commonly counted in the history of modems, as the modem function was incidental to the multiplexing function. Using Smartmodem, a computer can directly dial the phone using corresponding commands.

Key Concepts in Modem Technology

  • Data Phone (1960): Introduced in 1960.
  • POTS (Plain Old Telephone Systems): Classification of modem is mostly done on the basis of bits/sec.
  • Modem: A device that modulates an analog carrier signal for encoding digital information.
  • TV Modem: Not a type of modem.
  • High-Speed Modem: Uses the concept of fallback.
  • Datacards: An example of an external modem.

Modern Modem Developments

Current modems are composed of an analog, digital V.92, the digital PCM technique was applied to increase the upload speed to a maximum of 48 kbit/s, but at the expense of download rates. Power line modems and double-way satellite modems are new types of latest broadband modems.

  • Amperes: Used as a quantity for current.
  • Ohms: Used as a quantity for resistance.
  • Siemens: Used as a quantity for conductance.
  • Henrys: Used as a quantity for inductance.

The accuracy of digital multimeters is better when compared to analog meters.

Softmodem/Winmodem

A softmodem or winmodem is a stripped-down modem that takes up most of the tasks in software, which was traditionally performed in hardware. In high-speed modems, the concept of fallback is used very commonly.

Multimeter Resolution

  1. In a multimeter, digits are often used to specify the resolution.
  2. The resolution can be specified using “display counts”.
  3. The largest number that can be displayed by a multimeter can be determined from the display counts.
  4. In multimeter specification, the display count is just referred to as count.

A voiceband modem is one apt example that converts digital 0s and 1s from a personal computer into sound signals which could be transmitted over telephone lines of Plain Old Telephone Systems (POTS) which on the other side receives the sound signal and converts it back to the corresponding digital information.

Differences with Deep Space Telecom Modems vs. Landline Modems

  • Digital modulation formats that have high Doppler immunity are typically used.
  • Waveform complexity tends to be low, typically binary phase shift keying.
  • Error correction varies from mission to mission, but is typically much stronger than most landline modems.

Unit 10: Analog-to-Digital Conversion

The count of samples that the circuit can generate over a range of analog values is indicated by the measure resolution. Quantization error ranges from 0 to one-half of the LSB value. Successive approximation ADCs make use of comparators to eliminate the ranges of voltages, gradually settling on a final voltage range. An ADC takes in an analog continuous signal that is to be transformed, and it is then sampled into a digital set of values. Ideally, the DAC’s outputs a series of impulses which then undergo a filtration by the reconstruction agent. The analog-to-digital conversion process is a linear process; the majority of the conversion circuits are known as of the type linear.

Key Concepts in ADC and DAC

  • Resolution: The unit of resolution is Volts. The count of samples that the circuit can generate over a range of analog values is indicated by the measure called Resolution. Resolution can be defined as voltage range divided by the count of distinct intervals.
  • RAMDAC: A device called RAMDAC combines DAC with a memory (RAM) which stores the conversion tables for contrast, brightness, and gamma corrections.
  • Sigma-Delta ADC (Delta-Sigma ADC): Samples the input signal by a large factor and filters out only the required signal band.
  • Pulse Width Modulator: A low-pass analog filter with a duration specified by the digital input is used. A stable current or voltage is passed into this filter.
  • Rotary Encoders: Different kinds of ADCs like rotary encoders which are non-electronic, semi-electronic devices.
  • Signal-to-Noise Ratio: With respect to quantization noise, it takes the best value in case the probability density function (PDF) of a signal is uniform.
  • CDF (Cumulative Distribution Function): CDF stands for Cumulative Distribution Function.
  • Quantization Error: An inescapable error in all types of ADCs which arises due to the finite resolution.
  • Pulse Width Modulator: The simplest type of DAC.
  • R-2R Ladder ADC: A binary weighted DAC in which resistors of values R and 2R are repeatedly used.

DAC Characteristics

  1. Resolution: This is the count of the output levels that the DAC can possibly reproduce.
  2. Maximum Sampling Frequency: This is the maximum speed at which the DACs can produce the correct output.
  3. Monotonicity: This is the ability of the analog output of DAC to increase with an increase in digital code or vice versa.
  4. THD+N: This is the measure that projects the noise and distortions introduced into the signal by the DAC.

ADC conversion has to convert the flow of continuous analog in time into digital values. Hence the rate of sampling of the analog signal plays a major role. Sampling rate or sampling frequency is the term for the rate at which new digital values are sampled.