Wireless & Communications

Envelope Tracking is a power supply technique used for improving the energy efficiency of Radio Frequency (RF) power amplifiers. Using this technique, the fixed DC supply voltage to the RF power amplifier is replaced with a dynamic supply voltage that closely tracks the amplitude, or "envelope" of the transmitted RF signal. Envelope tracking ensures that the amplifier is operating at peak efficiency with respect to given output power requirements.

Arbitrary Waveform Generators (AWG) have always been incorporated in RF signal generation systems to generate complex modulations, analog or digital. Traditionally, AWGs generated real or complex (I/Q) baseband signals to feed modulators.

As AWGs grew in bandwidth, linearity, and accuracy, a new approach was possible. Instead of generating the baseband signals, it was possible to generate an already modulated IF signal. The final RF frequency was then achieved through a mixer. However, mixers and L.O. add their own impairments

The continuous advances in DAC and memory technologies have increased bandwidths and sampling rates for AWGs to the 10GHz range and beyond, while the improved signal processing capabilities have resulted in the incorporation of real-time interpolators, IQ Modulators, and NCOs to implement Digital Up-Converters (DUC). This allows for the direct generation of modulated RF signals in the UHF, L, S, C and X Bands.  This approach can support extremely high modulation BW, well beyond 2GHz, and reduce the complexity and cost while improving flexibility and channel density, which is especially useful for today’s radar (i.e. AESA radars) and wireless communication systems (i.e. Massive MIMO).

The IEEE standard 802.11ad is a wideband millimeter wavelength addition to the 802.11 family of standards. It provides multi Gbps short range signals in the 57-71GHz band, supporting up to six 2.16GHz channels, each with 1760MHz bandwidth.

In this white paper we explore a number of different approaches to generating and analyzing these wide bandwidth signals using the Proteus Arbitrary Waveform Transceiver. Generation and analysis can be performed using IQ baseband signals with I and Q on each generator or acquisition channel, or fully modulated IF signals using the built-in DUC/DDC functions with more than 2GHz of modulation/analysis BW.

The Proteus Architecture is also scalable to tens, even hundreds, of synchronized and coherent output and input channels, allowing for the creation of test systems supporting beamforming and/or MIMO.

Waveform Memory Size and Overall Waveform Data Transfer Rate

The gains in terms of waveform memory efficiency when DUC is used to generate RF signals (thanks to the usage of interpolation) has been mentioned in the previous part. However, these gains go beyond what can be expected from the mere reduction of the incoming sample rate for baseband waveforms. Generating accurate RF signals through direct generation of the carrier is not as straight forward as it could seem. For a continuous modulation, the waveform must be calculated in such a way it can be looped seamlessly. In this chapter we’ll demonstrate the advantages of DUC for RF signal Generation in AWGs

In this chapter, we’ll demonstrate Implementation of the DUC in the Proteus Family, which incorporates DUC in the P258X (optional) and P948X products, regardless of the platform (B, D, or M). The main differences between the P258X and P948X are maximum sample rate (2.5GS/s vs. 9GS/s) and the 8-bit DAC mode available in the P948X products so direct generation without interpolation or digital up-conversion is possible up to 9GS/s. The PXIe modules can incorporate two or four channels.

This white paper introduces how modern AWGs (Arbitrary Waveform Generators) can generate multi-tone signals that can compete in quality with those generated by multiple CW (Continuous Wave) generators while improving flexibility, the number of tones, and cost-effectiveness.

Multi-tone signals, to be useful, must be generated in a convenient and cost-effective way with sufficient quality to address the target application. One of the important issues to consider is the frequency band to be covered and the ratio between the central frequency and the bandwidth of the multi-tone signal.

AWGs can generate a fully defined baseband (I/Q complex signal with two channels) or an IF/RF (real signal with just one channel) multi-tone signal from a mathematically defined waveform. Continuous generation is possible thanks to the seamless looping capability existing in all arbitrary waveform generators.

SFDR is probably the most limiting factor when using a multi-tone signal for a given test. In previous sections, the best practices to maximize this parameter have been shown and discussed. However, IMD caused by non-linearities will always show up in the final signal. It will be visible as unwanted tones in the adjacent channels or within the notch implemented for in-band testing.

Creating and analyzing signals with Proteus and MATLAB takes a few simple steps. In this application note we show how to generate and receive a WLAN beacon signal at 2.4GHz in the instruments' first Nyquist Zone. The code can easily be modified to create a signal in the second Nyquist zone, all the way up to the WiFi-6 frequency extension of 7.125GHz.

Next generation wireless signal such as WLAN in the 6GHz band, Ultra-wideband (UWB) and 5G use orthogonal frequency division multiplexing (OFDM) to transmit high speed data over a wireless link. OFDM uses hundreds of carries with a simple narrowband modulation on each carrier. This means each carrier is more robust to interference but has a low transmission bandwidth, but by having 100’s of carriers you get a highspeed data transfer rate. The force multiplier!

Traditionally, Arbitrary Waveform Generators have analog BW, which is not much higher than the BW of its DAC’s Nyquist criteria, causing the suppression of signals at higher Nyquist zones. The new DAC technology found in Tabor’s Signal Expert series of AWGs, offers exceptionally wide bandwidth reaching up to 7GHz and even beyond. Ideal for research, electronic test, radar & IEEE 802.11ad applications.

One of the key elements in a WiGig test setup, is an Arbitrary Waveform Generator. see how the Tabor SE5082, with its 5GS/s sampling clock & up to 5GHz IQ modulation bandwidth can serve as an excellent candidate.

Today, modulated signals are used in almost every existing communication method. They are found in many industries such as mobile phones, radars, lasers, Wi-Fi networks, modems, navigation systems (GPS), RFID tags and satellite communications. In implementations such as in digital communications, amplitude and phase may be modulated simultaneously. This way, the baseband signal (the data signal) is separated into two orthogonal components: In-phase and Quadrature.

DTMF (Dual-Tone Multi Frequency), or “touch-tone” signaling, was developed as a handset-to-switchboard signaling system for use over analog telephone lines. Using DTMF, a key press results in the generation of 2 tones using distinct frequencies, with a different combination representing each key. DTMF signaling is widely used in telephony and IVR (interactive voice response) applications.

Radio Frequency Identification (RFID) is an automatic method of collecting data from tags and transmitting it directly into computer systems using radio waves and without human intervention.
An RFID tag is an object that can be integrated into or attached to a product, animal, or person for the purpose of identification and tracking. The tags are read by an RFID reader using radio waves.

Arbitrary waveform transceivers (AWTs) are a type of AWGs that both generate and receive waveforms in testing environments. Here’s how they are helping engineers test out applications in the field of wireless communications.