# US 2026/0074938 A1 · Systems encoding data on multiple carrier frequencies in a sigma delta bit stream

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- Number: US 2026/0074938 A1
- Document ID: US20260074938A1
- Status: Published application
- Kind: A1
- Application number: 19/327,670
- Filed: 2025-09-12
- Published: 2026-03-12
- Earliest claimed: 2024-09-12
- Assignees: SiliconIntervention Inc.
- Applicants: SiliconIntervention Inc.
- Inventors: A. Martin Mallinson
- Web page: https://patentgrep.com/patent/US20260074938A1

## CPC

- H04L 27/2627: {Modulators}
- H03K 17/6871: {the output circuit comprising more than one controlled field-effect transistor}
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M)

## Abstract

An example system for encoding OFDM data may comprise a processor and a transmitter. The processor may be configured to encode OFDM symbols into a first sigma-delta (ΣΔ) modulated bitstream, such that spectral content of the first sigma-delta (ΣΔ) modulated bitstream contains tones at subcarrier frequencies corresponding to the encoded symbols. The transmitter may be configured to transmit the sigma-delta (ΣΔ) modulated bitstream to a receiver.

## Claims

### Claim 1

A system for encoding OFDM data, the system comprising:
a processor configured to encode OFDM symbols into a first sigma-delta (ΣΔ) modulated bitstream, such that spectral content of the first sigma-delta (ΣΔ) modulated bitstream contains tones at subcarrier frequencies corresponding to the encoded symbols; and
a transmitter configured to transmit the sigma-delta (ΣΔ) modulated bitstream to a receiver.

### Claim 2 (depends on 1)

The system of claim 1, the transmitter further configured to apply a filter to the first sigma-delta (ΣΔ) modulated bitstream to remove frequency content above a fraction of a sigma delta clock rate to create a filtered sigma-delta (ΣΔ) modulated bitstream and transmit the filtered sigma-delta (ΣΔ) modulated bitstream at a reduced rate to a receiver.

### Claim 3 (depends on 1)

The system of claim 1, wherein the sigma-delta (ΣΔ) modulated bitstream is a one-bit sigma-delta (ΣΔ) modulated bitstream.

### Claim 4 (depends on 1)

The system of claim 1, wherein the receiver that receives the sigma-delta (ΣΔ) modulated bitstream from the transmitter, accumulates samples of the sigma-delta (ΣΔ) modulated bitstream, applies an FFT to recover the OFDM symbols, and decodes the OFDM symbols.

### Claim 5 (depends on 2)

The system of claim 2, wherein the filter is a cascaded integrator-comb (CIC) filter.

### Claim 6 (depends on 5)

The system of claim 5, wherein the CIC filter is a 6-bit CIC filter configured to output a predetermined number of bits and transmit the sigma-delta (ΣΔ) modulated bitstream to the receiver, the reduced data rate being at a rate of 1/64th of a clock.

### Claim 7 (depends on 1)

The system of claim 1, wherein data to be encoded into the OFDM symbols is received from a multichannel device generating complex signals to be encoded on more than one channel.

### Claim 8 (depends on 5)

The system of claim 5, wherein the reduced data rate is less than a Pulse Code Modulation (PCM) serial clock.

### Claim 9 (depends on 1)

The system of claim 1, wherein the processor inserts a tone at a point where noise begins to fall at a percentage of clock rate with respect to increasing an over sampling ratio (OSR).

### Claim 10 (depends on 9)

The system of claim 9, wherein the processor inserts the tone at approximately 40% of a sigma-delta (ΣΔ) clock rate.

### Claim 11 (depends on 9)

The system of claim 9, wherein there are a plurality of carriers and the tones are at points such that a data rate of a data transfer is a multiple of the sigma-delta (ΣΔ) clock rate.

### Claim 12 (depends on 1)

The system of claim 1, wherein the system comprises a first analog circuit configured to assist in encoding data, the first analog circuit comprising:
a first transistor M1 including a first source configured to receive a first current, a first drain coupled to a third drain at a third transistor M3, and a signal input applied to a first gate, a voltage at the first gate determining how much current flows through the first transistor M1;
a second transistor M2 including a second source configured to receive the first current, a second drain coupled to a fourth drain at fourth transistor M4, and the signal input applied to a second gate, the voltage at the second gate determining how much current flows through the second transistor M2;
the third transistor M3 including a third source configured to receive a second current and the signal input applied to a third gate, the voltage at the third gate determining how much current flows through the third transistor M3; and
the fourth transistor M4 including a fourth source configured to receive the second current and the signal input applied to a first gate, the voltage at the first gate determining how much current flows through the fourth transistor M4.

### Claim 13 (depends on 12)

The system of claim 12, where the first transistor M1 and the fourth transistor M4 form a differential pair.

### Claim 14 (depends on 13)

The system of claim 13, wherein the second transistor M2 and the third transistor M3 are active loads that improve gain.

### Claim 15 (depends on 12)

The system of claim 12, wherein the first, second, third, and fourth transistors are NMOS FETs.

### Claim 16 (depends on 12)

The system of claim 12, further comprising:
a fifth transistor M5 including a fifth source configured to receive the first current, a fifth drain coupled to a seventh drain at a seventh transistor M7, and a signal input applied to a fifth gate, the voltage at the fifth gate determining how much current flows through the fifth transistor M5;
a sixth transistor M6 including a sixth source configured to receive the first current, a sixth drain coupled to an eighth drain at eighth transistor M8, and the signal input applied to a sixth gate, the voltage at the sixth gate determining how much current flows through the sixth transistor M6;
the seventh transistor M7 including a seventh source configured to receive the second current and the signal input applied to a seventh gate, the voltage at the seventh gate determining how much current flows through the seventh transistor M7; and
the eighth transistor M8 including an eighth source configured to receive the second current and the signal input applied to an eighth gate, the voltage at the eighth gate determining how much current flows through the eighth transistor M8.

### Claim 17 (depends on 16)

The system of claim 16, wherein the first, second, third, and fourth transistors apply to a real part of a complex number and the fifth, sixth, seventh, and eighth transistors apply to an imaginary part of the complex number.

### Claim 18 (depends on 17)

The system of claim 17, where the first current is the real part of the signal and the second current is the imaginary part of the signal.

### Claim 19 (depends on 18)

The system of claim 18, wherein a first area of the first, second, third, and fourth transistors of the first analog circuit are such that the first signal is multiplied by a cosine of 60 and a second area of the fifth, sixth, seventh, and eighth transistors of the first analog circuit are such that the first signal is multiplied by a sine of 60.

### Claim 20

A method, comprising:
encoding OFDM symbols, by a processor, into a first sigma-delta (ΣΔ) modulated bitstream, such that spectral content of the first sigma-delta (ΣΔ) modulated bitstream contains tones at subcarrier frequencies corresponding to the encoded symbols; and
transmitting, by a transmitter, the sigma-delta (ΣΔ) modulated bitstream to a receiver.