Complete Communications Engineering

VOCAL’s Soft Radio reference design supports a wide range of industrial and RF signaling standards, including error correction, signal detectors, encryption, and modulations. Computationally intensive routines have been optimized to meet MIPS and memory constraints on a variety of different platforms. VOCAL has the expertise and experience to develop and configure custom signaling solutions to meet specific softradio user requirements and environmental constraints. Contact us for a demo.

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VOCAL’s software libraries are optimized for performance on ANSI C and leading DSP architectures from TI, ADI, Intel, ARM and other vendors. Our radio software my be licensed as a library or complete design. Custom solutions are also available to meet your radio application needs.


Soft Radio Features

  • LCD display
  • Keypad input
  • RF Signal Strength
  • Push-to-Talk (PTT)
  • Battery strength indication
  • Headset, speaker and microphone
  • Flash

Narrowband FM (NBFM) Soft Radio

VOCAL’s Narrowband FM Soft Radio module is intended for transmission of voice band audio in the range of 300 hz to 3 khz across a narrowband FM channel approximately 15 khz wide. The frequency spread of the transmit path is adjustable, and the receiver utilizes an optimal carrier tracking PLL with a matched prefilter. Pre- and de-emphasis of the final signal are available options. Quadrature input samples are preferred for the receiver, with a sample rate in the range of 20 to 50 khz. Other types of input signals can also be handled.

12 Kbps FSK Soft Radio

VOCAL’s Soft Radio FSK module implements a standard FSK (frequency shift keying) modulation with a +-6 khz frequency variation and 12 khz baud rate. This type of data modulation is used in several governmental and civilian standards. Quadrature input samples are preferred, with a sample rate in the range of 20 to 50 khz. An FSK radio stream or other type of input data stream can also be handled. Soft or hard decision outputs are available.

Custom modulations, including QPSK and QAM, are available on request.

CTCSS Signaling

CTCSS is a set of sub-audible low frequency tones normally used for channel separation or identification when multiple devices are using the same physical channel. A typical usage would be to assign a different CTCSS tone to a number of hand-held radios, allowing each radio to be identified by the tone it transmits. Other uses include using different CTCSS tones for different channels, allowing receivers to ignore channels that are meaningless to it.

VOCAL’s CTCSS detection module has a typical 300 ms detect time, with noise floor performance that exceeds most FM carrier detect thresholds. Tone precision may be specified in tenths of a hz. Detect time and bandwidth may be adjusted based on application.

A CTCSS generation module is also available.

Selcall Signaling

Selcall is a single-tone signaling method used to communicate equipment or other machine information over a channel. The tone set typically consists of 18 tones, including 16 data tones, a tone for repetition, and a control signal tone. Tones are generally 20 ms long, though different international standards may mandate different tone periods.

VOCAL’s Selcall detector module can be configured with arbitrary tone periods and frequencies. Multiple detect patterns may be specified, such as patterns for initial Selcall identification and Extended Selcall data. The detector performance is near the noise floor and nyquist limit for detection, and uses the inter-tone restrictions to disqualify illegal patterns and improve detection quality.

A Selcall generation module is also available.

Convolutional Coding

VOCAL’s Soft Radio FSK module is often used in tandem with a seven state, rate 1/2 convolutional coder to reduce bit errors. A number of different types of convolutional coders and interleavers are available, with both hard and soft decision decoding.

Standard turbo coding modules as well as custom modules, are available depending on the specific application.

Reed-Solomon Coding

Reed Solomon error correction modules are available to further improve the quality of data modulation links. Typically, Reed Solomon coding is used as an outer code with an interleaver to clean up errors produced by an inner convolutional code. A number of standard Reed Solomon types are available, including those for Red Book and CCSDS. Custom Reed Solomon decoders can easily be created for specific applications.

Soft Radio Voice and Data Reference Design

VOCAL’s Soft Radio Voice and Data Reference Design uses our extensive software suite, with computational intensive routines optimized to meet MIPS and memory constraints. The hardware design supports various DSP options, such as the TI TMS320C55x or ADI BF-532. Development hardware is available on a demonstration board. The firmware also provides optional software interfaces for memory, LCD display, GPIO, Codec and RS232.

Soft Radio Voice Hardware Design

Additional configurable possibilities include the use of a low bandwidth vocoder, such as MELP/MELPe. The softradio design is fully compatible with our Radio over IP software to extend the range and interoperate with other radio networks. In addition, secure transmission between units is also available using VOCAL’s security stack and encryption libraries. Softradio AES encryption is available in hardware or in software modules.


  • Customizable LCD display
  • Vocoders (i.e. MELP, MELPe)
  • Secure communication

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