Understanding Chip Antennas Handbook

This LTCC technology involves the fabrication of a multi-layer ceramic substrate by screen-printing ceramic green tapes with conductive, resistive, or dielectric inks. The LTCC process enables the integration of multiple layers of circuitry, similar to a multi-layer PCB, which can be interconnected through vias, to form complex three-dimensional structures.

The advantages of LTCC technology include a consistent dielectric constant around the antenna elements near field, size, capacitive coupling resiliency, SMT for high-speed volume manufacturing, high reliability and stability at high temperatures, excellent electrical properties, low signal loss, and high dimensional accuracy. LTCC technology is widely used in various applications, including RF and microwave communication systems, automotive electronics, medical devices, and industrial automation. These chip antennas are designed to be compact and can be integrated into a wide range of electronic devices such as IoT sensors, mobile phones, laptops, Bluetooth headsets, and other small, typically portable, wireless devices.

Some of the key features of LTCC technology include but are not limited to:

• Miniaturization: LTCC technology enables the mass production/fabrication of compact and highly functional electronic components and modules.
• High-frequency operation: LTCC technology provides excellent electrical properties for RF and microwave applications.
• Highly repeatable & consistent process for volume applications that provides high yields of RF circuits and components.
• Thermal stability: LTCC technology offers high thermal conductivity, low thermal expansion, and high resistance to thermal shocks, making it suitable for high-temperature and temperature swinging applications.
• Integration: LTCC technology allows the integration of multiple components and circuits into a single package, reducing the need for external components and improving system performance.
• Customization: LTCC technology offers flexibility in design and manufacturing, enabling customization for specific applications and requirements.
• Reduction of time-to-market: Due to the aforementioned, LTCC reduces the number of prototype spins and iteration, effectively reducing the product’s development lead-time.

When to use Antenna Chips

Antenna Chips are highly effective and commercially attractive when system requirements include one or more of the following:

• Small compact packages
• Large volumes
• The operational frequency band is above 433MHz
• 4 watts (CW – Continuous Wave) or less of transmit power at the antenna.
• The antenna can be located directly on the circuit board.
• Omni directional radiation pattern performance is preferred.

When not to use Antenna Chips

Antennas Chips are often not the best solution when system requirements include one or more of the following:

• Higher than 4 watts (CW – Continuous Wave) output power at the antenna is required.
• The antenna needs to be physically located away from the circuit board.
• Replacing whip antenna while still requiring the same gain.
• The system requires directional antenna performance or an effective antenna average gain of 3dBi or more

"No-Ground" or "Keep-Out" Areas Antenna (Chip) Overview

A ground plane is typically used with an antenna chip to provide a reference plane for the antenna and to improve its performance. For Johanson antennas, a ground plane must be included.

The ground plane is an integral part of the overall antenna system design. The size of the ground plane can vary. For example, if a customer only needs one cm of range, then the ground plane can be minimal. If the customer requires 30m, then the ground size and fluidness are critical.

When Johanson designs antenna ceramic chips, there are some basic requirements established prior to conception. Some of these requirements include the size of the PCB and clearance area, gain, radiation pattern, efficiency and the type/amount of ground required.

During the optimization process which typically includes creating a uniform radiation in the desired axis, the designers at Johanson use a "no-ground" area and its geometry on the PCB as one of the key features to optimize radiation pattern performance. This "no-ground" area is critical to the final antenna performance.

It is important to note that the "no-ground" or “keep-out” area must extend down through all layers of a multilayer PCB.

However, it's important to note that while Johanson antenna chips may function with changes to the "no-ground" area, their performance may be less predictable and less efficient compared to the same antenna chips with a specified "no-ground" area. Therefore, it's important to carefully consider the requirements of your specific application and consult with the Johanson's technical team when considering changes to the "no-ground" area.

• Wearable devices
• Portable Audio
• Sensors
• Tag, Tracers, iBeacon

• Home Automation/RF Locks
• Advanced Thermostats
• POS/Payment Systems
• In-Vehicle WiFi

• WiFi Access Points
• Chipset Specific FEMs
• Portable Positioning Modules
• Vehicle/Insurance Tracking

The LTCC process starts with the preparation of the ceramic powder and other materials. The ceramic powder is mixed with organic binders and solvents to form a homogeneous slurry, which is then processed into ceramic green tapes of the desired thickness and dimensions.

Screen printing: The green tapes are then screen printed with conductive, resistive, or dielectric inks to form the desired circuit pattern. The ink is deposited onto the green tape using a fine mesh screen, which is pressed against the tape and moved along its surface. The ink is then dried to remove the solvent and binder.

Lamination: Multiple layers of green tapes with different circuit patterns are then stacked on top of each other and laminated together using a combination of heat and pressure. The resulting laminated structure is called a "green body".

Via Formation: Vias are then created in the green body to interconnect the different layers of circuitry. This is typically done by drilling or punching small holes through the green body and filling them with conductive paste.

Cutting: The substrate is then cut, singulation of the individual components.

Firing: The green body is then fired in a furnace at a low temperature (typically between 850°C and 1000°C) to remove the organic binders and sinter the ceramic particles, resulting in a dense and co-fired ceramic substrate. The conductive, resistive, and dielectric inks are also fired, creating the desired electrical properties.

Termination: The fired ceramic components are inspected for defects and then the termination paste is applied in the form of dipped termination or printed land pattern terminations. These terminations, also called solder pads, perform the electrical connections to the circuit board.

Finally, at Johanson, antenna chips undergo rigorous RF testing to ensure that only fully functional parts are delivered to our valued customers.

The LTCC process can be modified and customized to suit specific applications and requirements. For example, different materials with various dielectric properties can be used for the ceramic powder, and the firing temperature can be adjusted to achieve specific electrical and thermal properties. These different powders provide various k and loss tangent values allowing our component designers to achieve unique solutions.

Why Not Lower Than 433MHz (Frequency Range Overview)

With current design approaches and frequencies below 433MHz, the physical size of the antenna becomes relatively large and thus, cost prohibitive. At the higher costs, these chip antenna solutions below 433MHz lose commercial appeal.

The lower band is also constrained by the wavelength when limiting the package dimensions. For lower frequencies to propagate efficiently, certain elements such as the physical inductance cannot be effectively replaced by an inductor having an equivalent physical length. Although these designs have shown to resonant effectively, the lack of physical elements resulted in unacceptable radiation performance.

Lower frequency antennas require larger sizes than higher frequency antennas because the size of the antenna is directly proportional to the wavelength of the electromagnetic wave it is designed to transmit or receive. The wavelength is inversely proportional to the frequency, according to the formula: wavelength = speed of light / frequency.

This means that at a lower frequency, the wavelength is longer, and a larger antenna is required to efficiently receive or radiate the intended signal. Conversely, at a higher frequency, the wavelength is shorter, and a smaller antenna can be used.

For example, a half-wave dipole antenna (a simple type of antenna) has a length of half the wavelength it is designed to operate at. A dipole antenna designed to operate at a frequency of 1 MHz would have a length of approximately 150 meters, while a dipole antenna designed to operate at a frequency of 1 GHz would have a length of only 15 centimeters. This size difference is significant and can limit the use of lower frequency antennas in certain applications where size constraints are important.

In addition to size considerations, lower frequency antennas may also suffer from lower efficiency due to losses caused by the ground and other obstacles. These losses increase with the size of the antenna and can further limit the range and performance of the antenna. Designers must take these factors into account when selecting an antenna for a particular application.

Bandwidth (Definitions)

In an antenna, bandwidth refers to the range of frequencies over which the antenna can operate effectively. Specifically, it is the difference between the highest and lowest frequencies within which the antenna can transmit or receive a signal with acceptable radiation patterns, gain, and returnloss performance.

A wide bandwidth is desirable for an antenna as it enables the antenna to operate over a larger range of frequencies, making it more versatile and useful in a variety of applications. A narrow bandwidth, on the other hand, limits the range of frequencies over which the antenna can be used. Bandwidth is also critical in applications where capacitive coupling may shift the antenna resonance.

The bandwidth of an antenna is affected by many factors, including the ground plane, the tuning network, the size and shape of the antenna, the material used to construct it, and the operating frequency.

The bandwidth of a Johanson chip antenna can be measured in terms of percentage bandwidth or absolute bandwidth. Percentage bandwidth is the ratio of the bandwidth to the center frequency of the antenna, expressed as a percentage. Absolute bandwidth is the difference between the upper and lower frequencies within which the antenna can operate effectively, expressed in megahertz (MHz) or gigahertz (GHz).

Typical Bandwidth for Chip Antennas (Bandwidth Definitions)

The typical bandwidth is determined by the application. Many of Johanson's chip antennas are designed for ISM band frequencies, which include BLE and WiFi, are also optimized to operate over a relatively narrow band from 2.4GHz to 2.5GHz, 4% bandwidth. Our UWB antennas operate over much wider bands. For example, Johanson Technology’s unique Ultra-Wide-band antenna, P/N 3100AT51A7200, operates from 3.1GHz to 10.3GHz which is 107% bandwidth.

Wide-band VS Multi-band (Bandwidth Definitions)

Some antennas are multi-band designs while others are wide-band designs.

Multi-band designs work only in the prescribed bands and not between those bands. Wide-band designs function over the entire band of operation

Gain (Definitions)

Antenna gain is a measure of the effectiveness of an antenna in radiating or receiving electromagnetic waves in a particular direction. It is the ratio of the radiation intensity of an antenna in a given direction to the radiation intensity that would be produced by an ideal isotropic radiator (a hypothetical point source that radiates uniformly in all directions) radiating the same total power.

In simpler terms, antenna gain describes the degree to which an antenna focuses energy in a particular direction. An antenna with a higher gain will concentrate more energy in a particular direction than one with a lower gain.

Antenna gain is usually expressed in decibels (dB), and the unit of measurement is referred to as dBi (decibels relative to an isotropic radiator). Antenna gain is an important factor in the design and selection of antennas for specific applications.

Antennas with high gain are typically used in long-range communication systems, while low-gain antennas are used for short-range communications or in situations where a more omni-directional radiation pattern is desired.

Isotropic Radiator (Gain Definitions)

An isotropic radiator is a hypothetical point source of electromagnetic waves that radiates uniformly in all directions without any directional preference. In other words, it emits energy with equal intensity in all directions, creating a spherical pattern of radiation.

The concept of an isotropic radiator is used as a reference to compare the performance of other antennas or radiating elements. The gain of an antenna is usually measured with respect to the gain of an isotropic radiator, expressed in decibels (dB), and is referred to as dBi (decibels relative to isotropic).

While an isotropic radiator is an idealized concept and cannot be physically realized, it provides a useful reference for evaluating the performance of real-world antennas and other radiating elements. Since an isotropic radiator radiates energy uniformly in all directions, its radiation pattern is a perfect sphere. However, it is difficult to visualize a perfect sphere in a 2-dimensional image.

Instead, the radiation pattern of an isotropic radiator is often shown as a simple plot of gain versus direction, with the gain being constant in all directions. The plot would be a perfect circle, as shown in the image Figure 1:

As you can see, the gain (expressed in dBi) is the same in all directions, represented by the circular/ semi-spherical shape of the plot.

The gain in dBi (decibels relative to isotropic) of an isotropic radiator is always 0 dBi. This is because an isotropic radiator is a theoretical point source of electromagnetic radiation that radiates equally in all directions, and there is no direction in which it is "better" than any other direction. Therefore, by definition, its gain relative to itself is 0 dBi.

It's worth noting that while a perfect isotropic radiator doesn't actually exist in the real world, it is a useful reference point for measuring the gain of antennas and other radiating structures. The gain of an antenna is typically measured relative to an isotropic radiator, with positive values indicating that the antenna radiates more power in a particular direction than an isotropic radiator would

• Poorly matched chip antenna – specifically the antenna return-loss is lower than the specification.
• The no-ground specified on the data-sheet was not followed in the design.

• The enclosure was made of a material that was conductive or coated with a metal loaded paint, effectively blocking some or all radiation.

The enclosure was made with a high loss or high absorption material like carbon fiber.

• Large deviation from the geometry of the layout on the data-sheet specification.
• Broken up top RF ground pour (sections of ground vs fluid unobstructed ground).
• No or poor via stitch.
• Very small PCB footprint with respect to the antenna (poor ground)

• Tall conductive components placed immediately adjacent to the no ground area such as batteries, shielding, or metal screws.
• Presence of LCD displays, button, and other conductive objects in the encasement directly above or adjacent to the chip antenna.

• 1. Populate the final PCB with all components
• 2. Cut the antenna feed trace on the PCB to separate it from the filters and transceiver.
• 3. Use a probe or attach a semi-rigid cable to the antenna side of the cur trace.
• 4. Modify the enclosure to allow the semi-rigid cable to exit the enclosure opposite the antenna.

• 5. Using a network analyzer.
• 6. One-port (S11) calibration for N.A. (Network Analyzer) Open-Short-Load for desired operating bandwidth.
• 7. Mount probe (semi-rigid RF cable for our example) onto PCB and connect to N.A.
• 8. Measure S11 of test board without antenna or any matching components and save as: →S11_open →save trace to memory of N.A.
• 9. Measure S11 of test board with antenna and series 0Ω resistor mounted and save as: →S11_antenna.
• 10. Set N.A. to data/memory mode (S11_antenna/ S11_open) and display/save as: →S11_match.
• 11. Match the trace of S11_match to 50Ω (center of Smith chart at the desired frequency) by varying the values of the passive devices.

• The dielectric loading aka “capacitive loading" of the enclosure shifts the frequency response requiring a re-tuning.
• Large conductive components placed immediately adjacent the no-ground area.
• Variations in PCB impedance due to fabrication or co-planar waveguide CPWG improper calculation.

• The complete assembly was never matched.
• Unknown inner ground layers intersecting the antenna clearance region (defective PCB).
• Antenna is out of band.

• Reduced signal-to-noise ratio
• Low receiver sensitivity
• Lower than expected link budget
• Short transmit receive distance
• The enclosure is made of, coated with, or contains a non-compatible material
• Enclosure is very lossy at operational frequency.
• A customer made an enclosure out of carbon fiber and the loss of the carbon fiber cause very low gain

• Enclosure is conductive
• A customer used a type of “shiny” paint which contains metal particulates effectively blocking RF signals.
• The enclosure housed a replaceable battery that was located directly over or below the antenna
• The reflection from the battery disrupted the gain and the radiation patterns

Antenna Chip Selection Guide is a useful tool early in the design process when a decision on which Johanson antenna chip/s will be selected.

First, the designer must choose what type of layout is desired based on the product shape and remove allowable antenna chip placement.

The mounting plays a critical role in antenna chip selection.

It is important that the designer understands that the "Antenna Optimization Process" is composed of the following:

All four of these features work together to determine the final system performance. As such, changes to the no-ground area or chip locations relative to the edge of the circuit board can result in substandard performance.

Once the layout type has been selected, then determine the application type and associated operational frequency.

In some cases, the selection guide will provide two antenna chip options. We have identified features that should lead the designer to a specific selection.

Client is then sent copies of the new matching circuit schematic with their corresponding values and part numbers, measured radiated data, and patterns with their corresponding radiated efficiency and gain figures on your PCB. Sometimes this process may require Johanson Technology to modify your board in their lab, and to add probes through your enclosure/ housing.

Assemblies may be returned to customers at their request.

Please confirm with an engineer prior to sending your module. Sending modules without a confirmation risks them getting misplaced.

The ultimate goal is to optimize “Over-The-Air” performance of your design using Johanson’s extensive design knowledge and application optimization expertise for market success, this entire process takes 2 to 3 weeks, depending on the complexity of the design and environment.

Shipping address for prototypes to be tuned & characterized is:

Johanson Technology, Inc
Attention: Name of the project engineer
4001 Calle Tecate
Camarillo, CA 93012
USA

Johanson welcomes any inquiry related to LTCC antenna specifications which may not be in the catalog and will consider your needs for a unique/ custom antenna solution.

The design and tooling costs for a new antenna can be substantial. Thus, it is important that we also understand your anticipated demand for this new product. Although not an absolute requirement, an approximate minimum annual quantity of 1,000,000 pieces and a minimum of 3 years of production should be used to estimate the feasibility of developing a new chip antenna. Don't miss the opportunity to work with our outstanding design engineers.

Visit our website for more information. We look forward to assisting you with your unique design requirements See "RESOURCE" below

The Johanson Technical team will review your specification or requirements document.

Bandwidth:

The range of frequencies over which an antenna can operate with good performance.

Beam-width:

the angular width of the main lobe of an antenna radiation pattern.

Directivity:

A measure of how well an antenna concentrates energy in a particular direction, expressed as a ratio of the power radiated in a specific direction to the total power radiated.

Gain:

The measure of the ability of an antenna to direct energy in a particular direction compared to an isotropic radiator.

Impedance:

The opposition of an antenna to the flow of alternating current (AC), measured in ohms.

Isotropic Radiator:

an idealized antenna that radiates energy equally in all directions.

Polarization:

The orientation of the electric field of the radiated wave with respect to the ground plane.

Radiation Pattern:

The directional distribution of radiated energy from an antenna in three-dimensional space.

Return Loss:

A measure of the amount of power reflected back towards the source when a signal is transmitted through a transmission line or antenna. It is usually expressed in decibels (dB) and is a measure of the impedance mismatch between the source and the load.

Resonance:

The condition when an antenna is perfectly matched to the frequency of the applied signal.

VSWR (Voltage Standing Wave Ratio):

The ratio of the maximum voltage to minimum voltage along the transmission line connected to the antenna.

Planar Inverted-F Antenna (PIFA):

An antenna chip that has a rectangular or square radiating element connected to the feedline by a shorting pin. Widely used in mobile phones and other portable devices due to its compact size and low profile.

Meander Line Antenna:

An antenna chip that uses a zigzag or meandering line as the radiating element. Often used in applications that require a narrow bandwidth.

Monopole Antenna:

An antenna chip that is constructed using a simple, single-element structure. Often used in applications that require a broad bandwidth and high gain.

Dipole or Folded Dipole Antenna:

An antenna chip that consists of two identical conductive elements that are parallel to each other and oriented in the same direction.

Slot Antenna:

An antenna chip that uses a slot in the ground plane as the radiating element. Often used in applications that require a high radiation efficiency and low profile.

Ceramic Patch Antenna:

An antenna chip that uses a ceramic material as the substrate. Often used in applications that require a high radiation efficiency and low loss.

Inverted-L Antenna:

An antenna chip that has a vertical wire that is connected to a horizontal wire, creating an "L" shape.